WO2013120800A1

WO2013120800A1 - Wavefront manipulator and optical device

Info

Publication number: WO2013120800A1
Application number: PCT/EP2013/052673
Authority: WO
Inventors: Marco Pretorius
Original assignee: Carl Zeiss Ag
Priority date: 2012-02-16
Filing date: 2013-02-11
Publication date: 2013-08-22
Also published as: DE102012101262B3

Abstract

The invention relates to a wavefront manipulator, comprising at least one first optical component (1) and one second optical component (3). The optical components (1, 3) are arranged one behind the other along an optical axis (OA), wherein the first optical component (1) and the second optical component (3) are both arranged such as to be movable relative to each other in a respective direction of motion perpendicular to the optical axis (OA). In addition, the first optical component (1) and the second optical component (3) both have at least one refractive freeform surface (5, 7). An immersion medium that contacts the two components (1, 3) is arranged between the first optical component (1) and the second optical component (3).

Description

Wavefront manipulator and optical device

The present invention relates to a wavefront manipulator having at least a first optical component and a second optical component, which are arranged one behind the other along an optical axis. In addition, the invention relates to a use of the wavefront manipulator and an optical device with a wavefront manipulator.

In US Pat. No. 3,305,294 by Luiz W. Alvarez, optical elements having at least one first optical component and a second optical component, which are arranged one behind the other along an optical axis, each have a refractive free-form surface and are displaceable relative to one another relative to the optical axis. By lateral displacement of the optical components with the free-form surfaces, the refractive power of an optical element composed of the two components can be varied. Such optical elements are therefore also called Alvarez elements or Variolinsen. A variable refractive power corresponds to a variable focal position, which can be described by a change in the parabolic component of the wavefront of a beam bundle incident parallel to the axis. In this sense, a vario lens can be considered as a special wavefront manipulator.

In addition, from IM Barton et al., "Diffractive Alvarez Lens" Optics Letters 2000 (25), pages 1-3 elements are known, which are arranged along an optical axis one behind the other, with respect to the optical axis laterally displaced against each other and diffractive The diffractive effect of one of the two displaceable elements formed optical element depends on the lateral position of the two elements to each other.

Variolenses which may be provided according to the teaching of US 3,305,294 are suitable for numerous applications. Examples of this are performing rapid Z-scans of a focus position for acquiring three-dimensional image information, the three-dimensional image stabilization, as described for example in DE 10 2011 054 087 or the compensation of a defocusing, for example in the field of microscopy by varying a cover glass thickness or by Variation of a refractive index can occur. In addition, there are numerous other applications in which zoom lenses can be used to realize a zoom functionality, such as photo or film camera lenses, especially flat-mounted Vario lenses in compact cameras and mobile phones.

In almost all practically relevant cases, it is highly desirable to keep the optical image largely free from color aberrations over the zoom range. However, this is very difficult, if not impossible, to achieve this by conventional means. For example, thermally induced or otherwise induced refractive index variations of an optical medium often produce changes in system power that have a strong wavelength dependency. While the refractive power change at an average wavelength can usually be compensated sufficiently well by a known defocus compensator (for example a sliding lens, a change in the air space between two lenses, etc.), the wavelength dependence of the defocusing remains as a residual error that can not otherwise be compensated. In particular, in the case of flat-mounted zoom lenses no practicable teaching is known which would make it possible to obtain a constant achromatic correction over the entire zoom range. It is therefore a first object of the present invention, an advantageous wavefront manipulator with at least a first optical component and a second optical component, which are arranged along an optical axis in a row and perpendicular to the optical Axle can be moved relative to each other, to provide. It is a second object of the present invention to provide an advantageous optical device. A third object of the present invention is to provide an advantageous use for the wavefront manipulator according to the invention.

The first object is achieved by a wavefront manipulator according to claim 1, the second object by an optical device according to claim 16 and the third object by use of a wavefront manipulator according to claim 17. The dependent claims contain advantageous embodiments of the invention.

An inventive wavefront manipulator comprises at least a first optical component and a second optical component, which are arranged one behind the other along an optical axis. The first optical component and the second optical component are each arranged to be movable relative to one another in a direction of movement perpendicular to the optical axis. In addition, the first optical component and the second optical component each have at least one refractive free-form surface. The optical components can be arranged so that free-form surfaces of adjacent optical components face each other, or so that the freeform surfaces are facing away from each other. By lateral displacement (i.e., displacement perpendicular to the optical axis) of the two optical components relative to one another, the strength of the refractive power of the optical element can be changed thanks to the free-form surfaces. The influencing of the refractive power by lateral displacement is described in US Pat. No. 3,305,294, to which reference is made in this connection.

Such an optical element has, however, without further measures on the adjustment of the strength of the power-dependent, variable color error. These manifest themselves when using the optical element in an optical system, depending on its arrangement in the beam path either predominantly as longitudinal chromatic aberration or as lateral chromatic aberrations, also called chromatic magnification errors. Thus, when pupil-like arrangement occur mainly longitudinal chromatic aberration, near the field Arrangement predominantly lateral chromatic aberration. In other arrangements, other aberrations such as coma or astigmatism may also be wavelength dependent, such that, for example, chromatic variations of astigmatism or chromatic coma may result as aberrations. In order to avoid chromatic aberrations, an immersion medium contacting the two components is therefore located in the wavefront manipulator according to the invention between the first optical component and the second optical component. Suitable immersion medium are, in particular, liquids, for example ultrapure water, salt solutions, immersion oils, etc., and elastic optics. Since only a lateral movement of the first optical component and the second optical component takes place, the wavefront manipulator with immersion medium can have a flat construction, ie a small extent perpendicular to the lateral direction of movement. By suitably adjusting the refractive index and the Abbe number of the immersion medium to the refractive index and the Abbe number of the material from which the optical elements are made, a variably adjustable wavefront manipulation can be achieved, the effect of which is independent of the wavelength over an extended wavelength range, so that the wavefront manipulator according to the invention can be used as an achromatic wavefront manipulator. With the embodiment of the wavefront manipulator according to the invention, therefore, the color errors described above, in particular the longitudinal chromatic aberrations, can be largely avoided when varying the refractive power. For example, in one possible application, he provides a suitable solution to the problem of compensation for thickness and index fluctuations in microscopy with high-aperture objectives, as described in the introduction.

The wavefront manipulator according to the invention has a broad field of application in the correction of primary and secondary chromatic aberrations, which goes beyond the mere use as an achromatic vario lens. In one embodiment, it can achromatically provide a variable parabolic phase effect, ie a variable optical power. In another embodiment It allows a targeted influence on higher order of errors of the wavefront, such as for the targeted influence of spherical aberration, coma or astigmatism. In particular, it is also possible to correct any wavefront error which is described by a fixed predefined functional dependency on the pupil coordinates, namely in each case only for one field point. The freeform surface profile to be used for this purpose is given in the direction parallel to the displacement direction by the parent function of the pupil function, ie the function which describes the pupil dependence of the wavefront error, and in the direction perpendicular thereto by a function proportional to the pupil function. An application for the wavefront manipulator is also conceivable, for example, where a Vario basic optics, which may consist of conventional lens groups displaceable relative to one another along the optical axis, has variable values of the image aberration over an adjustment range. This variable aberration can then be selectively compensated by a wavefront manipulator according to the invention over the entire adjustment range. It is therefore possible, for example, to use the wavefront manipulator as compensating element in a photographic zoom lens in which then a compensation of the zooming dependent compensation of the occurring and by conventional means not correctable aberrations takes place.

If an opto-cement is used as the immersion medium, in which excessive movements could induce disturbing voltages, it is advantageous if the first optical component and the second optical component are each movable in a direction of movement perpendicular to the optical axis by a distance of a maximum of 50 pm. The maximum possible distance over which the components can be moved without inducing disturbing stresses depends in particular on the shear modulus of the opto-cuttings used. It is particularly advantageous if the first optical component and the second optical component can each be moved by a distance of a maximum of 20 μm, in particular of a maximum of 10 μm, since this increases the number of usable optical elements. When using an immersion liquid as immersion medium but also displacement paths in the millimeter range are possible. The effect of the wavefront manipulator is exactly identical for two wavelengths λι and λ ₂ if the condition η _λ - \ i ₂ - 1 _{= Q}

exactly maintained. For example, in this case the color longitudinal error of a wavefront manipulator embodied as a variometer disappears exactly. Some authors then speak of a "dichromate" or "dichromatic correction", which is linguistically more precise than "Achromat" or "achromatic correction", but has not generally prevailed in the literature as a linguistic usage. The two wavelengths λι and λ ₂ are the wavelengths to which the two Abbe numbers refer as secondary wavelengths, if, as usual, defined:

Some authors then denote the Abbe number with specification of the two auxiliary wavelengths λι and λ ₂ in the index of the formula character. In order not to conflict here with the indices 1 and 2, which refer in the context of the invention to the two media (eg, glass and immersion liquid), the wavelengths for greater clarity in brackets the symbol for the Abbe number adjusted.

An achromatic wavefront manipulator, ie a wavefront manipulator, with which a wavefront manipulation can be brought about essentially without color aberration, can be obtained, for example, if the first optical component and the second optical component consist of the same material and the material of the optical components and the immersion medium fulfill the following condition:

Ni and vi denote the refractive index and the Abbe number respectively of the material of the optical components, and n ₂ and v ₂ denote the refractive index. index or the Abbe number of the immersion medium. Fulfillment of the above-mentioned inequality leads to an at least approximately achromatic wavefront manipulator with reduced chromatic aberrations, which in some applications can already be considered sufficient. However, to obtain useful achromatization for a large number of applications, it is advantageous if the stricter inequality

is satisfied. If a particularly high-quality achromatic wavefront manipulator is to be created, the even stricter inequality should

be fulfilled.

The described achromatic wavefront manipulator can be embodied, in particular, as an achromatic lens with variable refractive power, that is to say as an achromatic variolynx, if the free-form surfaces of the optical elements are designed to influence the parabolic component of the wavefront. If a particular wavefront error, which can be clearly described by its dependency on the pupil coordinates or alternatively by reference to the Zernike order, is to be influenced by the wavefront manipulator, the surface profile in the direction parallel to the sliding direction of the elements is proportional to the parent function of this pupil function , and to choose perpendicularly proportional to the pupil function itself.

By suitable choice of the shape of the free-form surfaces, any wavefront manipulation at the fundamental wavelength can be brought about without generating appreciable chromatic aberrations. The degree to which color errors are avoided depends on how large the limits to be met in the above inequality are. Analogous to the condition for achieving achromatic (more precisely: dichromatic) correction of the wavefront manipulator, a corresponding condition for apochromatic (more precisely: trichromatic) correction and an explicit condition for the disappearance of the secondary spectrum can be established. For trichromaticity, for example, a combination of Two zoom lenses according to the invention (each with two mutually movable free-form elements and one enclosed "immersion lens") and thus has high relevance as a preferred design of the wavefront manipulator with a wavefront manipulator according to the invention, a color error, especially the longitudinal chromatic aberration, but not only targeted Zero to achieve achromatization, but the wavefront manipulator can be formed, for example, with a different choice of optical media, that a defined color error for a Rand or Nebenwellenlängen the transmitted wavelength range is generated. Without further measures, a defined refractive power change, that is to say a defined defocusing, is generally brought about at the same time for a mean wavelength of the transmitted wavelength range. In some applications this can be tolerated. Often, however, it is desirable to generate a defined chromatic aberration for an edge or minor wavelength of the transmitted wavelength range without causing defocus for the central wavelength. This is possible with a wavefront manipulator according to the invention, in which the first optical component and the second optical component consist of the same material and the material of the optical components and the immersion medium fulfill the following conditions:

In. - «J <0.05

In this case, ni and v- _\ denote the refractive index and the Abbe number of the material of the optical components and n2 and V2 the refractive index and Abbe's number of the immersion medium. One Wavefront manipulator, which satisfies the aforementioned inequalities, represents a wavefront manipulator for selectively influencing the chromatic variation of the wavefront intervention.

The smaller the difference between the refractive index ni of the material of the optical components and the refractive index Π2 of the immersion medium precipitates (ideally n1 = n ₂ ), the less changes the focal position at the central wavelength when setting a predetermined color error. The more that the dispersion characteristics descriptive Abbezahl vi of the material of the optical components of the Abbezahl v _{2 of} the immersion medium, the smaller the lateral displacement paths and the flatter can the free-form profiles, which are necessary to achieve a given chromatic variation of the element precipitate. It is therefore advantageous if, instead of the above condition, the more stringent condition Ι ^ -η ^ Ο, ΟΙ

| _j - v ₂ | > 10 is fulfilled. It is particularly beneficial to whom the even more stringent condition

is satisfied.

In the wavefront manipulator described for selectively influencing the chromatic variation of the wavefront engagement, the material of the optical components can be, for example, glass, crystalline material or plastic. An example of an immersion medium is an organic hydrocarbon, water or an aqueous solution. In one example of a material combination, the material of the optical components is plastic, the immersion medium is an alkali-ion-doped aqueous solution, or a saline solution. The wavefront manipulator according to the invention can be used not only in the visible spectral range but also in the UV spectral range. For this purpose, as the material of the optical components, for example, quartz glass or a crystalline material may be selected. In particular, highly pure water is considered as immersion medium.

If the structure of the refractive free-form surfaces of the optical components comprises a superposition of at least two structural profiles, different wavefront manipulations in any fixed predetermined relationship can be carried out simultaneously. For example. For example, the actual free-form surface of the optical components may be formed by an overlay of a free-form surface for changing the refractive power and a free-form surface for changing the spherical aberration. A corresponding variola varies with the displacement of the optical components against each other a refractive power and at the same time changes a spherical aberration, both changes are proportional to each other with an arbitrary but firmly vorzuswählenden proportionality factor. Even in such more general applications, the rules set out above for material selection for achromatization or for producing a defined chromatic aberration can be applied mutatis mutandis. According to one development of the wavefront manipulator, both the front side and the rear side of an optical component are provided with a refractive free-form surface. This development makes it possible to provide wavefront manipulators with profile depths of the freeform surfaces smaller than 30 μm, in particular smaller than 10 m. In a particular development of the wavefront manipulator, the refractive free-form surface of the first component may be assigned a first diffractive structure and the refractive free-form surface of the second component a second diffractive structure. The associated diffractive structures can then be used to influence a wavelength-dependent effect of the respective refractive free-form surface. By means of a suitably chosen immersion medium, it is then possible to bring about a far-reaching independence of the diffraction efficiency of the diffractive structure from the wavelength, so that a so-called efficiency Achromatized diffractive optical element (EA-DOE) receives. The independence of the diffraction efficiency from the wavelength is obtained, in particular, when the first optical component and the second optical component consist of the same material, the material of the optical components and of the immersion medium have refractive indices whose difference is a linear function of the wavelength, and the material / Medium having the lower refractive index has a higher dispersion than the material / medium having the higher refractive index. The shape of a refractive free-form surface can be described in each case by a polynomial winding which has development coefficients that are different from zero in finitely many specific polynomial orders. The diffractive structure associated with a refractive free-form surface is then described by a polynomial winding which has non-zero development coefficients in the same polynomial orders as the polynomial winding of the refractive free-form surface. Those development coefficients of a polynomial winding describing a refractive free-form surface and the polynomial winding describing the associated diffractive structure, which are each assigned the same polynomial order, are in a fixed functional relationship to one another. In this case, the development coefficients respectively associated with the same polynomial order of a polynomial winding describing a refractive free-form surface and the polynomial winding describing the associated diffractive structure may be in a linear functional relationship in particular. The functional relationship may in particular depend on the material used in the respective optical component, ie on its dispersion. In particular, an identical functional relationship can be present for all polynomial orders having coefficients other than zero.

The polynomials of the first and second polynomial windings may each be appended by two variables representing different directions perpendicular to the optical axis of the optical element. In this case, the two directions can be perpendicular to one another, wherein the one direction corresponds to the direction of movement of the optical components and wherein the polynomial winding describing a refractive free-form surface and the polynomial winding describing the associated diffractive structure each have only odd polynomial orders in those variables which the direction of movement of the optical components represents. The polynomial winding describing a refractive free-form surface and the polynomial winding describing the associated diffractive structure then each need only have straight polynomial orders in that variable which represents the direction perpendicular to the direction of movement of the optical components.

Further details on the design of the diffractive surfaces and on the use of optical elements provided with diffractive structures and free-form surfaces are described in DE 10 2011 055 777, to which reference is made with regard to these aspects.

According to a second aspect of the invention, an optical device is provided. The optical device according to the invention can be, for example, an optical observation device such as a microscope, in particular a surgical microscope, a telescope, a camera, etc. But it can also be another optical device such as, for example, an optical measuring device. It is equipped with at least one wavefront manipulator according to the invention. Therefore, in the optical device of the present invention, the effects and advantages described with respect to the optical element of the present invention can be obtained.

According to a third aspect of the invention, a use of at least one wavefront manipulator according to the invention is provided. In the use according to the invention, at least one wavefront manipulator according to the invention serves to bring about one or more of the following corrections or reductions: dichromatic correction, trichromatic correction, reduction of the secondary spectrum, reduction of the tertiary spectrum. A trichromatic correction can, for example, be brought about by using at least two wavefront manipulators according to the invention. However, it is also possible to bring about a trichromatic correction with only one wavefront manipulator according to the invention, if it is equipped with a diffractive structure as described above. The additional degrees of freedom gained by the additional diffractive structure can be used for trichromatic correction, because the diffractive structure according to the Sweatt model corresponds to a lens made of a material with an equivalent (negative) Abbe number. Thus, a wavefront manipulator comprising two moving free-form elements with an immersion medium located therebetween and a diffractive structure on the free-form elements has three independently adjustable refractive powers with which the trichromatic condition can be fulfilled.

The condition for the disappearance of the secondary or tertiary spectrum requires at least one medium whose partial dispersion deviates from the normal straight line. This condition can also theoretically and practically meet with a variolysis invention or a wavefront manipulator according to the invention, since the known immersion oils, such as, for example, the Immersol 518N, bring about an abnormal partial dispersion for chemical reasons. Thus, in a variola invention according to the invention whose free-form elements are formed from a standard glass (glass whose dispersion behavior follows the normal straight line), between which a conventional immersion oil is located, one can actually meet the condition for the disappearance of the secondary spectrum without great difficulty.

In a further use of a wavefront manipulator according to the invention, this can be used to bring about a position-dependent correction of at least one wavefront error in a zoom lens. For this purpose, the wavefront manipulator can be arranged in particular in the region of an (approximately) collimated beam path in the zoom lens and can be laterally deflected depending on the position of the zoom lens in such a way that it produces a wavefront error (eg, a longitudinal chromatic aberration, a spherical aberration, etc.) of the zoom lens.

Further features, properties and advantages of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures.

Figure 1 shows a first embodiment of a wavefront manipulator according to the invention in a schematic representation.

Figure 2 shows an alternative embodiment of the wavefront manipulator according to the invention in a schematic representation.

Figures 3 and 4 show a festbrennweitige optics and the occurring

Chromatic aberrations.

FIGS. 5 to 9 show an optic with a wavefront manipulator in various positions.

FIGS. 10 to 14 show those shown in FIGS. 5 to 9

Positions of the displaceable components associated color errors without immersion medium between the optical components of the wavefront manipulator.

FIGS. 15 to 19 show those shown in FIGS. 5 to 9

Color errors associated with positions of the displaceable components when using an immersion medium between the optical components of the wavefront manipulator. FIG. 20 shows a third exemplary embodiment of the wavefront manipulator according to the invention in a schematic representation. shows a third embodiment of the wavefront manipulator according to the invention in a schematic representation.

Before discussing an embodiment of the invention, the conditions for dichromaticity, trichromaticity and correction of the secondary spectrum are briefly outlined.

The condition for achromatism of a variolysis of any number of elements is:

In this case, cj denotes the refractive power of the jth lens and (λι, Xi) the associated Abbe number of the medium from which the lens is formed with reference to the auxiliary wavelengths λ-1, λ, defined by:

If at the same time a predetermined system breaking force O _{tot is to be} achieved, the following additional condition must also be fulfilled:

In a dichromatic ("achromatic") corrected optical system, the system refractive power is exactly the same for the two wavelengths λι and λ _2. It is then said that the primary longitudinal chromatic aberration disappears.

However, at all other wavelengths, especially at the center wavelength, λο still deviates. The deviation is called the "secondary spectrum" of the longitudinal chromatic aberration.

For other wavefront effects of the wavefront manipulator element, the above reasoning can be directly transmitted analogously. The The dichroism condition remains exactly and the second equation (constant power) is replaced by an analogue equalization setting a requirement (constraint) for the overall system effect on the desired wavefront error (eg, spherical aberration). To correct the secondary spectrum, the size is defined as the so-called partial dispersion coefficient P of a medium at the reference wavelength λο and the spurious wavelengths λι and λ2

The condition for the disappearance of the secondary spectrum at λ ₀ is explicitly:

This additional condition can only be fulfilled if at least one medium has a partial dispersion coefficient P which deviates significantly from the so-called normal straight line. It turns out that, for example, organic immersion oils differ significantly from the normal lines of the dispersion relationship known for optical glasses. Consequently, a variolysis invention or a wavefront manipulator according to the invention can be designed such that the secondary spectrum disappears. Quite explicitly this means that the wavefront effect of the wavefront manipulator according to the invention can have an exactly identical (predetermined) effect at 3 wavelengths λο, λι and λ2 when the above condition is met. In a trichromat ("apochromats"), in generalization of the above conditions, the wavefront effect of a wavefront manipulator according to the invention at exactly three wavelengths λο, λι and λ2 are exactly the same The explicit condition for trichromaticity in a system with at least three independently adjustable powers and media taken from popular textbooks. A first exemplary embodiment of a wavefront manipulator according to the invention is shown in FIG. The wavefront manipulator comprises two optical components 1, 3, which are arranged one behind the other along an optical axis OA and are arranged laterally, ie perpendicular to the optical axis OA, displaceable relative to one another, as indicated in the figure by the arrows in -y and + y direction is. In the present exemplary embodiment, each of the two optical components 1, 3 has a refractive free-form surface 5, 7 on one side and a plane surface 9, 11 on the side remote from the free-form surface. The optical components 1, 3 are arranged relative to one another such that their free-form surfaces 5, 7 lie opposite one another. The free-form surfaces 5, 7 behave in a zero position exactly complementary to each other, so that the two optical components 1, 3 are equivalent in a zero position of a plane-parallel plate. Between the two optical elements 1, 3 there is an immersion medium 13, which in the exemplary embodiment shown in FIG. 1 is a liquid such as ultrapure water, a salt solution, an immersion oil, etc. In order to hold the liquid in the space between the two optical components 1, 3, the peripheral surface of the wavefront manipulator is provided with an elastic sleeve 15, which prevents leakage of the liquid immersion medium 13 and also in the lateral movement of the optical components 1, 3 relative to each other keeps tight. The sleeve 15 may, for example, be formed by a plastic film. Instead of a cuff of elastic material but also another liquid-tight seal can be used, for example. In the form of a bellows construction. Since the lateral movement of the optical components 1, 3 is in many cases only fractions of a millimeter, a variety of common liquid-tight seals are basically applicable. For example. As a further alternative, it is possible to provide the surfaces to be wetted by the immersion liquid with an adhesive coating which holds a thin immersion film between the free-form surfaces by adhesive forces and thus prevents leakage of the immersion liquid. The optical components 1, 3 themselves may, for example, consist of glass, of plastic or of crystalline material. The choice of material may depend in particular on the intended use of the wavefront manipulator. If this is to be used in the optical spectral range, the choice will usually fall on glass or plastic. On the other hand, if it is to be used in the ultraviolet spectral range, the optical components 1, 3 will typically consist of quartz glass or a crystalline material, such as calcium fluoride or barium fluoride. As immersion liquid, for example, ultrapure water is considered in the ultraviolet spectral range.

A second embodiment of the wavefront manipulator according to the invention is shown in FIG. Elements which do not differ from the wavefront manipulator of the first embodiment are designated in FIG. 2 with the same reference number as in FIG. 1 and will not be explained again in order to avoid repetitions.

The wavefront manipulator of the second embodiment differs from that of the first embodiment in that the immersion medium is formed by an elastic optic material 17 instead of a liquid. On an elastic sleeve, as it is present in the first embodiment, is therefore omitted in the second embodiment.

In wavefront manipulator of the second embodiment is advantageous if the two optical components 1, 3 are each limited in their movement perpendicular to the optical axis to a maximum displacement of 50 pm in order to avoid disturbing voltages in the optocouple 17. The maximum possible distance over which the optical components can be moved without inducing disturbing voltages depends in particular on the shear modulus of the opto-cuttings used. Depending on the optocouple used 17, it may therefore be advantageous if the optical components 1, 3 each only by a distance of a maximum of 20 μιτι, or even only by a distance of a maximum of 10 pm are movable. Regardless of the type of immersion medium used, the wavefront manipulator in the simplest embodiment has exactly two optical components 1, 3 which can be displaced laterally, ie transversely to the optical system axis OA (compare FIGS. 1 and 2, in which the one optical component 3 in + y is shifted, the other optical component 1 in -y direction, both in opposite directions by equal amounts).

The basic principles for designing the freeform surfaces are presented below.

In the case of an explicit area representation in the form z (x, y), the free-form surface may preferably be described by a polynomial having only straight powers of x in a direction orthogonal to the direction of movement of the optical components 1, 3 and in a direction y parallel to the direction of movement has only odd powers of y. The free-form surface z (x, y) can first generally, for example, by a polynomial winding of the form oo

z = Σ C x ^m y ⁿ (1)

m, n = \, where C _{mn represents} the development _{coefficient of} the polynomial winding of the free-form surface in the order m with respect to the x-direction and the order n with respect to the y-direction. Here, x, y and z denote the three Cartesian coordinates of a point lying on the surface in the local area-related coordinate system. The coordinates x and y are to be used as dimensionless measures in so-called lens units in the formula. Lens units here means that all lengths are first given as dimensionless numbers and later interpreted to be consistently multiplied by the same unit of measure (nm, pm, mm, m). The background is that the geometric optics is scale-invariant, and in contrast to the wave optics does not have a natural length unit. A pure defocusing effect can be effected according to the teaching of Alvarez, if the free-form surface of the optical components 1, 3 can be described by the following polynomial of 3rd order:

Here, it is assumed that the lateral displacement of the optical components 1, 3 takes place along the y-axis, which is thereby defined. If the displacement is to take place along the x-axis, the role of x and y must be changed accordingly in the above equation. The parameter K virtually scales the profile depth and in this way determines the achievable refractive power change per unit of the lateral displacement path s.

For parallel to the optical axis OA incident beam and air (refractive index n = 1) between the two optical components 1, 3 causes the lateral displacement of the optical components by a distance s = | ± y | thus changing the wavefront according to the equation:

ie a change in the focus position by changing the parabolic wavefront component plus a so-called Piston term (Zernike polynomial with j = 1, n = 0 and m = 0), the latter corresponding to a constant phase and then not affecting the imaging properties, when the optical element according to the invention is in the infinite beam path. Otherwise, the Piston term for the imaging properties can usually be neglected.

The surface power of such a zoom lens is given by the following formula:

Φ = 4 K - s (n - \) (4) Here s is the lateral displacement of an element along the y-direction, K is the scaling factor of the tread depth and n is the refractive index of the material from which the lens is formed at the respective wavelength.

In order to minimize the center thickness of the element, a term proportional to y (wedge or tilt term) can also be added, the optical effect of which on the two free-form surfaces then almost canceling out, but minimizing the center thickness of the element. A pure tilting term on the free-form surfaces is optically ineffective in a first approximation and therefore does not cause any color aberrations in particular. It is possible that the two relative to each other moving optical components 1, 3 are oriented as shown in Figure 1 so that the two free-form surfaces 5, 7 facing each other. In this case, it is particularly easy to perform an adjustment of the zero position, namely by the distance between the two optical components 1, 3 is reduced until the two components touch. In this position, a centering of the optical components takes place automatically. Subsequently, the distance in the axial direction can be increased just as far again that the two optical components 1, 3 are not touching during the lateral movement during the functional operation.

But it is also possible to orient the two optical components 1, 3 such that the free-form surfaces 5, 7 are remote from each other. In this way, the distance between the optical components, which are then opposite to those with the flat surfaces 9, 11, minimized, which is often advantageous, especially at larger field and aperture angles at the interface between the two optical components has exposed the picture quality.

It is also possible that the free-form surfaces can have additional terms of higher order for influencing individual image defects. For example, a term would be the form z (x, y) = - (y- x ⁴ +. (x ² .y ³ ) + (5) predominantly affects spherical aberration and could therefore be used for applications in the field of microscopy, focusing on another sample depth Correcting aberration can also help in this way to partially or completely compensate the spherical aberration caused by the change in thickness of the element (Piston term) in the convergent beam path.

The structure profiles may be freely superimposed, i. a structure for changing the refractive power and a structure for changing the spherical aberration may be superimposed in a free-form surface 5, 7, so that a corresponding wavelength manipulator upon displacement of the optical components 1, 3 against each other varies a refractive power and simultaneously changes a spherical aberration, both Changes are proportional to each other with an arbitrarily but firmly preselected proportionality factor.

Furthermore, it is also possible for both sides of the moving optical components 1, 3 to have an active mold according to the forms described above. For example, a symmetrical division of the surface profile according to the above formula on the front and rear surface of a component could cause the tread depths on each surface to remain sufficiently low, such that, for example, a photolithographic fabrication of the elements, typically only maximum tread depths in the range <10-30 allows μ ^η τι, is facilitated.

According to Lohmann (see Appl. Opt., Vol. 9, No. 7, (1970), pp. 1669-1671), it is possible to represent a variolae which is largely equivalent to the teachings of Alvarez, in which two free-form surfaces, for example, in the lowest order by a Equation of the form z (x, y) = A - (x ³ + y ³ ) (6) are described and the relative movement of the optical components 1, 3 to each other along a 45 ° with respect to the x and y axis extending straight line perpendicular to the optical system axis. The constant A is again a free scaling constant, which describes the maximum profile depth of the free-form surface and thereby the refractive power change per path length. The description according to Lohmann is not an independent solution, but essentially only an alternative representation.

Further details on the construction of the free-form surfaces 5, 7, with which the variable refractive power effect can be achieved, is described in US Pat. No. 3,305,294. Reference is made to this document for the construction of freeform surfaces.

The adaptation of the immersion medium 13, 17 to the material of the optical components 1, 3 will be described below with reference to two concrete examples. First, as a first example, a description will be given of an adaptation for providing an achromatic zoom lens, before, as a second example, a description of an adaptation for providing a defined adjustment of the longitudinal chromatic aberration without changing the focal position. For the provision of an achromatic vario lens, the condition for the adaptation of the immersion medium 13, 17 to the material of the optical components 1, 3 in the wavefront manipulator can be derived as follows:

The two freely moving free-form elements 1, 3 form a refractive power Φ = 4- / c- s- (n ₁ -l) and the variable "immersion medium lens" between the plates has a refractive power <b ₂ = 4 ks (n ₂ -Y), where k denotes the scaling factor of the free-form profile function, s the displacement path of the elements and ni and n ₂ the refractive indices of the material of the free-form elements 1, 3 or of the immersion medium at an average wavelength of the considered spectral range. The condition for achromaticity for two closely spaced lenses is generally:

In this case, vi and V2 denote the Abbe number of the material of the free-form elements 1, 3 or the Abbe number of the immersion medium. By inserting the equations for the refractive powers Φι and Φ ₂ in equation (7), the following condition can be established for the achromatic vario lens according to the invention n ₂ -1

(8) Of course, due to the limited choice of available optical materials, especially considering special requirements such as aging resistance, thermal expansion, etc., in practice, it may be slightly deviated from the above condition without departing from the scope of the invention. A parameter range for a variolysis according to the invention can be characterized approximately by the following conditions:

Preferred should even apply:

And more preferably, may apply:

(8c)

An achromatic wavefront manipulator, which is intended to influence a specific Zernike term instead of defocusing, also has to fulfill the same achromatization condition (7) or (8a) to (8c).

For example, an element providing a certain amount of spherical aberration independent of wavelength would be provided by two free-form elements whose area has the form z (x, y) = / - (y- x ⁴ + ^ (x ² .y ³ ) + ^) (9) and which are formed of a glass which, together with the immersion medium, satisfies conditions (7) and (8a) to (8c), respectively.

Analogously, the achromatization condition also applies in all other cases in which an "arbitrary" wavefront change AW (x, y) at a

Fundamental wavelength is generated by the free-form profile function z (x, y) is designed in the direction of movement of the elements to each other proportional to the parent function of AW (x, y) and perpendicular to the direction of movement proportional to the function AW (x, y) itself.

With an element according to the invention, a color longitudinal error can not only be deliberately set to zero with a different choice of optical media, but the element can also be designed so that defined amounts of longitudinal chromatic aberration are generated. In the case of a deviation from the condition according to equation (8a), equation (8b) or equation (8c), a lateral displacement of the free-form elements according to equation (2) simultaneously produces a refractive power change at the central wavelength (ie a defocus) and relative thereto a longitudinal chromatic aberration the marginal or minor wavelengths. The greater the deviation from the condition according to equation (8a), equation (8b) or equation (8c), the more noticeable is this effect. It is particularly noticeable when equation (8a) is not satisfied. In individual cases such superimposition could be useful, for example if the defocus at the middle wavelength can be compensated by other optical means. In general, however, one desires a clear separation between a change in a central focus position and a change in the longitudinal chromatic aberration. In this case, the solution proposed according to the invention consists in using for the free-form elements 1, 3 and the immersion medium 13, 17 arranged therebetween materials and media which are almost not in the refractive index n at the central wavelength but clearly in the Abbe number v differ from each other, especially those materials and media in which at the same time the conditions

-n ₂ \ <0.05 and | v, - v ₂ | > 5 (9a) are fulfilled. If a greater change in the longitudinal chromatic aberration is desired without changing the focal position, these conditions should be tightened, namely

(9b) or even

<0.002 and k - v,> 15 (9c)

Suitable combinations of materials are to be found and even widely used, since the dispersion of organic hydrocarbons is consistently significantly higher than glass at typical refractive indices of glass. In the event that the free-form elements 1, 3 are formed from plastic, as an immersion medium 13, 17, for example, with an appropriate alkali-doped aqueous (salt) solution into consideration. The conditions (9a) to (9c) can be understood from the following consideration: The more the Abbe number of free-form elements differs from the Abbe number of the immersion medium, the smaller the lateral displacement paths can be - and the flatter the freeform profiles 1, 3 can be Achieving a given color longitudinal error fail through the wavefront manipulator. On the other hand, the less the refractive index of the free-form elements differs from the refractive index of the immersion medium, the lower the change in the focal position at the central wavelength when setting a predetermined chromatic aberration.

According to the construction principle expressed in equations (8a) to (8c), for example, with two optical elements 1, 3 whose free-form surfaces 5, 7 are given by the equation (5), a wavefront manipulator for influencing the so-called Gaussian error, that is, the image defect that describes the chromatic variation of the spherical aberration.

As already mentioned, a plurality of structural profiles can be freely superposed in the free-form surfaces 5, 7 of the optical components 1, 3. For example. For example, a structure for changing the refractive power and a structure for changing the spherical aberration in the free-form surfaces 5, 7 may be superimposed so that a corresponding zoom lens will vary a refractive power when the optical components 1, 3 are displaced while changing a spherical aberration, both Changes are proportional to each other with an arbitrarily but firmly preselected proportionality factor. Even in such more general applications, the rules set out above for the effect of a corresponding choice of material according to condition (8a), (8b) or (8c) or according to the conditions (9a), (9b) or (9c) can be applied mutatis mutandis.

Hereinafter, a concrete embodiment for constructing a wavefront manipulator according to the present invention will be described with reference to design data.

The concrete example is based on a vario lens with two optical components 1, 3, each having a free-form surface 5, 7, whose shape is described by the polynomial winding according to equation (1). The development coefficients C _m , _{n of} the polynomial winding are in the design data listed in the following tables, respectively corresponding areas are indicated, wherein the development coefficients are marked with the powers of the associated polynomial terms.

Furthermore, there are rotationally symmetric aspheric surfaces defined by the equation: z = + A - (x ² + y ² ) ² + B - (x ² + y ² f + C - (x ² + y ² ) ⁴ + D - (x ² + y ² )

The associated coefficients k, A, B, C and D are indicated on the corresponding surfaces, respectively, following the vertex radius.

It should be noted that there are mathematically infinitely many equivalent representations of the same free-form surfaces. As stated earlier, a different definition of the displacement axes leads to a different-looking representation, but proves to be largely equivalent. The invention is therefore not limited to the explicit form of the representation selected in the specific embodiment.

The wavefront manipulator of the specific embodiment relates to an inventively designed solution for an achromatic focusing optics, which is connected upstream of a fixed firing group, and which allows a continuous adjustment of focusing on different object distances between So = -500 mm and So = -167 mm. The diameter of the aperture diaphragm is constant in the concrete embodiment, 20 mm.

In order to be able to show the construction of the optical element according to the invention with reference to the specific embodiment, the procedure is three-step. First, in a first step, an optically group designed for a fixed average object distance of So = -250 mm and quasi-defect-free for this fixed object distance is specified. In the second step, a Vario-lens is added to vary the system's refractive power and thus adapt it to the changed object intercept. The Variolinse still has no immersion medium. Finally, in the third step, a Variolinse invention with immersion medium is given, with It is possible to compensate the chromatic aberrations almost completely and over the entire distance range which can be set with the variolo- gy.

The optics 20, which images almost faultlessly for a fixed mean object distance of So = -250 mm, is represented in the concrete exemplary embodiment by a rotationally symmetrical hybrid optics, as shown schematically in FIG. For reasons of clearer presentation of the essential core of the invention, the representation in the figure is limited to idealized boundary conditions (only one field point). The optical system 20 shown in FIG. 3 consists of a collecting lens made of the glass FK5, which is aspherical on the front side, and a spherical diverging lens made of the glass SF1 cemented thereto. The diverging lens is provided on the back (F7) with an adapted DOE structure. In order to take into account the glass paths of the later required elements of the Variolinse, the optics 20 two plane-parallel glass plates 21, 23 are connected upstream. This part of the system is used here to simulate a virtually perfectly corrected fixed-focal-length optics, which, of course, can also be formed in practical applications by very differently constructed multi-lens objectives. In the concrete embodiment, the fixed focal length group is designed to image an object located 250 mm in front of the vertex of the leftmost glass surface F1 on an image plane 50 mm away from the vertex of the last, rightmost lens surface F7 , As an application for the example described here, for example, an objective for a digital surgical microscope can be considered, ie a surgical microscope with digital eyepieces and / or another display.

The design parameters of the optics 20 shown in FIG. 3 and the upstream glass plates 21, 23 are summarized in Table 1 below. Table 1 Area Vertex radius Thickness Material

in mm in mm

Object level 00 250,000 F1 00 1, 000 NLASF44 F2 00 0,400 F3 00 1, 000 NLASF44 F4 00 0,500 Aperture oo 0,000

F5 18,51472 6,000 FK5

aspheric coefficients:

k: 0.0000

A: -0.106452E-04 B: -0.216063E-07 C: -0.285433E-10 D: -0.207670E-12 F6 -76.75116 1.000 SF1

306,32,659 50,000

DOE parameters

λ ₀ : 546.00 d: -2.2271 E-04 C ₂ : 5.3348E-07

Image level 00 0.000

FIG. 4 shows the image error curves belonging to the optics from FIG. The vertical axis denotes the geometrical-optical transverse aberrations in millimeters and ranges from -0.05 mm to 0.05 mm. In this case, the left side, which is referred to in the figure as Y-fan (German Y-fan), the transverse aberration for a beam in dependence on the Y-coordinate of the opening beam in the exit pupil. The right-hand side, which in the figure is designated as an X-fan, shows a corresponding representation of the transverse aberration for the beam as a function of the X-fan. Coordinate of the opening beam in the exit pupil. The beam has an axis beam as the main beam, ie, the main beam is a beam that runs on the optical axis of the fixed focal length group 20, ie the X and Y coordinates has 0.0 and in the YZ plane and in the XZ Plane has the angle of incidence zero degrees with respect to the optical axis. The image point generated by the optics of a beam characterized by an axis beam as the main beam lies on the optical axis. In the figure, the main ray of the beam in the Relative Field is corresponding to the Y coordinate 0.00 and the angle 0 ° for the Y fan and the X coordinate 0.00 and the angle 0 ° for the X-Fan marked.

It can be seen from FIG. 4 that the residual errors that occur are practically completely negligible; The basic optical system is diffraction-limited for the one fixedly specified object intersection. The figure by the fixed focal length optics described is therefore virtually perfect against aperture errors and corrected for primary and secondary chromatic aberrations and represents a nearly ideal lens for the fixed predetermined average object distance of 250mm.

In the next step for the construction of the optical element according to the invention takes the place of the plane-parallel glass plates 21, 23 in front of the optics 20, a zoom lens with two optical components 1, 3, the free-form surfaces 5, 7 have. An immersion medium is not yet available. The zoom lens serves to focus on different object distances, which in the example range from -500 mm to -166.67 mm and are shown in FIGS. 5 to 9 on the basis of the following five intermediate positions: So = -500 mm, S ₀ = -333.33 mm, S ₀ = -250 mm, S ₀ = -200 mm and S ₀ = -166.67 mm. The two optical components 1, 3, each carrying a free-form surface 5, 7 on the inside, are laterally moved in opposite directions to each other to set the focus on the different object distances, so that a variable air lens results in the interior. The displacement paths of the first laterally moved optical component 1 in the 5 positions are +1.50 mm, +0.75 mm, 0.00 mm; -0.75 mm; -1.50 mm in the y direction. The second optical component 3 shifts in each case by equal amounts in the opposite direction, so that the displacement paths of the second laterally moving optical component 3 in the 5 positions -1.50 mm, -0.75 mm, 0.00 mm; +0.75 mm; +1.50 mm. The position of the image plane relative to the optics 20 remains constant (50 mm free cut width).

In the Variolinse the concrete Ausführungsbeipiels higher orders of the Alvarez freeform surface are used to adjust the spherical aberration with changed object intersection accordingly. The design data of the system according to step 2 are given in Table 2 below:

Table 2

Area Crest radius Thick material

in mm in mm

Object level 00 Variable F1 00 1, 000 NLASF44

F2 00 0.120

Free-form surface parameters:

Y: 3,2947E-02 X2Y: -4,0866E-04 Y3: -1.3622E-04

X4Y: 5,1255E-09 X2Y3: 3,8124E-09 Y5: 1 Ό076Ε-09

F3 00 1, 000 NLASF44

Free-form surface parameters:

Y: 3.2947E-02 X2Y: -4.0886E-04 Y3: -1.3622E-04

X4Y: 5.1255E-09 X2Y3: 3.8124E-09 Y5: 1.0076E-09

F4 00 0.500

Aperture oo 0.000 F5 18.51472 6.000 FK5 Asphärenparameter:

k: 0.0000

A: -0.106452E-04 B: -0.216063 E-07 C: -0.285433E-10 D: -0.207670E-12 F6 -76.75116 1.000 SF1

F7 306,32,659 50,000

DOE parameters

λ ₀ : 546.00 d: -2.2271 E-04 C ₂ : 5.3348E-07 Image plane oo 0.000

The result achievable with the variometer without immersion medium together with the fixed focal length optics 20 is reproduced in FIGS. 10 to 14, which show the aberrations associated with the positions of the optical components shown in FIGS. 5 to 9. As in FIG. 4, the vertical axes in each case denote the geometric-optical transverse aberrations in millimeters and extend from -0.05 mm to 0.05 mm. The left side of the figures again shows the transverse aberration for a beam with axis beam as the main beam as a function of the Y-coordinate of the opening beam in the exit pupil, the right side a corresponding representation of the transverse aberration for the beam in dependence on the X-coordinate of Opening beam in the exit pupil. It can be seen from FIGS. 10 to 14 that with increasing lateral displacement of the optical components 1, 3 of the variolore, severe chromatic errors occur that can not be eliminated with the approach known from the prior art. It can be clearly seen that only in the position 3 belonging to the original object distance of -250 mm does a chromatically corrected image result, while in all other positions a very considerable longitudinal chromatic aberration occurs as a limiting aberration. The person skilled in the art recognizes that the transverse aberrations belonging to different wavelengths are each approximately represented by a straight line tilted about the horizontal. Finally, in the third step, the previous variolysis is replaced by an inventively constructed zoom lens with immersion medium between the two optical components 1, 3. The free-form surfaces 5, 7 bearing optical components 1, 3 are made in the specific example of the glass NLAK8. At a wavelength of 546 nm, its refractive index is? I = 1.713003 and its Abbe number vi = 53.8316. The immersion medium 13 used is an immersion oil which has a refractive index n ₂ = 1.518 and an Abbe number v ₂ = 41.1 at a wavelength of 546 nm. Such an immersion oil is available, for example, from Zeiss under the name "Immersion Oil 518." If these numbers are used in inequality 8a, the result is 0.00062, which is well below the limit of inequality (8a) and even below that in equation (8c) and thus results in a very good correction of the chromatic aberration shown in Figures 10 to 14. Thus, with this inventive variola, it is possible to achieve chromatic aberrations almost completely and over the entire adjustable distance range avoid.

The remaining construction data of the concrete example for the variolese invention are summarized in the following Table 3.

Table 3

Area Crest radius Thick material

in mm in mm

Object level OO Variable F1 00 1, 500 NLAK8

Immersion oil

F2 OO 0.250

518

Free-form surface parameters:

Y: 1.1692E-01 X2Y: -1.6940E-03 Y3: -5.6465E-04

X4Y: 1.6363E-08 X2Y3: 2.0062E-08 Y5: 2.9304E-09 F3 oo 1, 500 NLAK8

Free-form surface parameters:

Y: 1.1692E-01 X2Y: -1.6940E-03 Y3: -5.6465E-04

X4Y: 1.6363E-08 X2Y3: 2.0062E-08 Y5: 2.9304E-09

F4 00 0.500

Aperture 00 0.000

F5 18,51472 6,000 FK5

Asphärenparameter:

k: 0.0000

A: -0.106452 E-04 B: -0.216063E-07 C: -0.285433E-10 D: -0.207670E-12

F6 -76.75116 1, 000 SF1 F7 306.32659 50,000

DOE parameters

λ ₀ : 546.00 d: -2.2271 E-04 5.3348E-07

Image level 00 0.000

Figures 15 to 19 show the aberrations that occur in the festbrennweitigen optics 20 with upstream Vario according to the invention. The vertical axes, in turn, each denote the geometrical-optical transverse aberrations in millimeters and range from -0.05 mm to 0.05 mm, the left side of the figures being the transverse aberration for a beam with the axis of the beam as the main beam as a function of the Y-coordinate of Opening beam in the exit pupil and the right side shows a corresponding representation of the transverse aberration for the beam in dependence on the X-coordinate of the opening beam in the exit pupil. In comparison with the image aberrations of the system with variolinse without immersion medium (Figures 10 to 14) it can be seen that for all object distances and associated travel paths of the free-form elements excellent correction of the longitudinal chromatic aberration is achieved. A third embodiment of a wavefront manipulator according to the invention is shown in FIG. The wavefront manipulator comprises two optical components 1, 3 which are arranged one behind the other along an optical axis OA and are arranged so as to be laterally displaceable relative to one another, ie perpendicular to the optical axis OA. Each of the two optical elements 1, 3 has a refractive free-form surface 5, 7 with an associated diffractive structure 25, 27. Between the optical components 1, 3 there is an immersion liquid 13 adapted in its refractive index. The wavefront manipulator is protected against leakage of the immersion liquid 13 by an elastic sealing collar 15, a sealing bellows or the like. Alternatively, it is also possible to provide the surfaces to be wetted by the immersion liquid with an adhesive coating which holds a thin immersion film between the free-form surfaces by adhesion forces and thus prevents leakage of the immersion liquid.

The material of the optical components 1, 3 and the immersion medium 13 are chosen so that their refractive indices have a difference which is a linear function of the wavelength. In addition, the lower refractive index material / medium has a higher dispersion than the higher refractive index material / medium. Such an optical element composed of a first material (in the present case the material of the optical components) and a second material (in this case the immersion medium) having different refractive indices and having a diffractive structure at the interface between the two materials also called efficiency achromatized diffractive optical element (EA-DOE). Efficiency achromatized diffractive optical elements and the conditions for a diffraction efficiency independent of the wavelength are described in detail, for example, in DE 10 2007 051 887 A1, to which reference is made in particular with regard to the conditions for a wavelength-independent diffraction efficiency. The conditions mentioned therein can be easily transferred to the present case where the second medium is an immersion medium. If the wavefront manipulator according to the invention is also embodied as an efficiency-achromatized diffractive optical element, refractive and diffractive wavefront manipulators can be produced, for example those with variable refractive power, in which the diffraction efficiency of the diffractive structure 25, 27 varies only slightly over a wide wavelength range and False light is suppressed in unwanted diffraction orders. As a result, diffractive wavefront manipulators can also be realized in which the diffraction efficiency does not vary more than 5% over a wavelength range of at least 200 nm, in particular at least 300 nm, and in particular varies no more than 1% over a wavelength range of at least 200 nm. For example, wavefront manipulators for the visible spectral range can be realized in which the diffraction efficiency in the range of 410 nm to 710 nm does not vary more than 5% and does not vary more than 1% in the range of 425 nm to 650 nm.

The diffractive structure can be described by a polynomial winding corresponding to the polynomial winding for the freeform surfaces (equation (1)). The phase function φ then has the form:

Here, C ' _mn denotes the development _{coefficient of} the polynomial winding of the diffractive structure 25, 27 in the order m with respect to the x direction and the order n with respect to the y direction. The coordinates x and y as well as the reference wavelength λο are to be used in equation (10) as dimensionless numerical measures (so-called lens units) in millimeters. The diffractive structure described in this way can be physically imagined such that, starting from the support surface, which may be a free-form surface, a plane surface or a curved surface, the associated segment of the diffractive structure each leaps around one upon reaching a fixed phase value of 2π Amount λο / ( ^η (λο) -1) in the z-direction relative to the support surface. The diffractive structure 25, 27 belonging to a refractive free-form surface 5, 7 is described by a polynomial winding which has non-zero development coefficients in the same polynomial orders as the polynomial winding of the refractive free-form surface 5, 7. Those development coefficients of a polynomial winding describing a refractive free-form surface 5, 7 and the polynomial winding describing the associated diffractive structure 25, 27, which are each assigned the same polynomial order, are in a fixed functional relationship to one another. In the case of the wavefront manipulator according to the invention, the development coefficients of the free-form surface C _{m, n} and the development coefficients of the diffractive structure C ' _m , _n are therefore different from zero with the same values of n and m and in particular coupled to each other by a fixed proportionality factor. The proportionality factor preferably depends on the dispersion in the material used of the optical components 1, 3 and is to be determined in each individual case from a numerical optimization calculation.

The diffractive structure belonging to the refractive free-form surface according to equation (2) accordingly has the following defining equation:

where the coefficient C is a constant proportional to K related to K in a manner dependent on the dispersion properties of the glass used and, in a concrete case, numerically determined. If, in order to minimize the center thickness of the optical component 1, 3, a term proportional to y is also added (wedge or tilt term) whose optical effect on the two free-form surfaces 5, 7 is almost canceled, but a minimization of the center thickness of the component 1, 3 of the element, the corresponding term can then also be provided in the diffractive structure. However, unlike the above teaching, he needs the phase function the diffractive surface 25, 27 and the height profile of the refractive free-form surface 5, 7 always contain the same polynomial terms - not necessarily in the diffractive structure 25, 27 may be provided. This is due to the fact that a pure tilting term on the free-form surfaces is optically ineffective to a first approximation.

If the free-form surfaces have additional terms of higher order for influencing individual image errors according to equation (3), the associated phase function of the diffractive structure then has the following form:

If the representation according to Lohmann is chosen (equation (6)), the corresponding phase function of the diffractive structure is to be described accordingly by the equation φ = - · 5 · ( ^χ3 + /) (13), where B is again to be interpreted proportional to A. and depends on the dispersion of the type of glass or type of plastic used.

With reference to FIG. 21, an exemplary embodiment of a wavefront manipulator is described below, in which four optical components 101, 103, 111, 113 are present. Two of the optical components together form an assembly 105, 115, which can be considered as a wavefront manipulator as described with reference to FIG. 1, FIG. 2 or FIG. The assemblies 105, 115 need not be the same design. For example. For example, one of the assemblies may be formed as a wavefront manipulator according to claim 1, the other as a wavefront manipulator according to claim 20. In the present embodiment, the four optical components 101, 103, 111, 113 form two assemblies 105, 115, each forming a wavefront manipulator according to FIG. The wavefront manipulator comprising the two subassemblies 105, 115 is arranged in the present exemplary embodiment in a zoom system which comprises four lens groups 107-110, which are shown in simplified form only as lenses in FIG. The two outer lens groups 107, 110 are fixed and collecting, the two inner lens groups 108, 109 displaceable and dispersive. The assemblies 105, 115 of the wavefront manipulator are positioned between the two inner lens groups 108, 109 in the region of an aperture diaphragm 106 - for example in front of and behind the aperture diaphragm 106, as indicated in the figure, where in a central zoom position a collimated beam path and in others Zommstellungen at least an approximately collimated beam path is present. In the illustrated central zoom position, the optical elements of the zoom system form a symmetrical arrangement with respect to the aperture diaphragm plane. In the exemplary embodiment shown in FIG. 21, the wavefront manipulator serves to bring about a trichromatic correction over the entire zoom range. However, it is also possible to bring about a dichromatic correction and a reduction of the secondary spectrum by means of the wavefront manipulator comprising the two components 105, 115. The more assemblies with optical elements of the wavefront manipulator which are displaceable relative to one another relative to the optical axis, the more corrections or reductions can be made with the additionally obtained degrees of freedom. The provision of diffractive structures, as described with reference to FIG. 20, also increases the number of degrees of freedom and thus also the number of possible corrections or reductions. Depending on what type of correction or reduction is to be made, only one of the assemblies 105, 115 - with or without a diffractive structure - can be sufficient in the zoom system. The present invention has been explained in detail by means of embodiments for illustrative purposes. However, it should not be limited to the embodiments, since the skilled artisan will recognize that deviations from the embodiments in the context of the accompanying Claims are possible. For example, a limitation of the lateral movement has been described only with respect to the embodiment with an optical cement as immersion medium between the free-form elements. A person skilled in the art, however, recognizes that a limitation of the lateral movements may be useful even if, instead of the optokit, an immersion fluid is used as the immersion medium. The limitation of the lateral movement can then ensure, for example, that the sealing effect of the cuff, the bellows, etc. is ensured in any case over the entire lateral range of motion. In addition, other considerations, such as a limitation of the space required for the wavefront manipulator, lead to a limitation of the lateral movement. A limitation of the lateral movement can, for example, be brought about by increasing the scaling factor k for the profile depth of the freeform surface given a given wavefront effect. Furthermore, in the embodiments, the free-form surfaces of the optical components have been described as identical. In fact, there may be slight differences between the free-form surfaces, such as to account for non-paraxial effects due to the deviation of the incident height of rays at the first and second free-form surfaces due to the finite path in the immersion medium. To derive these minor deviations, however, it is difficult to specify a general teaching. Often the deviations must be determined empirically. In addition, it is also possible in the third embodiment to replace the immersion liquid by an elastic optokit. Likewise, in deviation from FIG. 20, the diffractive structure may be present on the planar surfaces instead of on the free-form surfaces, the optical components then facing one another with their plane surfaces and the immersion medium being arranged between the planar surfaces. The same applies to embodiments without diffractive structure. Also in these, the optical components can be arranged so that their planar surfaces face each other and the immersion medium is arranged between the planar surfaces. The present invention should, therefore, be limited in scope only by the appended claims. LIST OF REFERENCES

1 optical component

3 optical component

5 refractive free-form surface

7 refractive free-form surface

9 plane surface

11 plane surface

13 immersion solution

15 cuff

17 elastic optokitt

20 fixed group

21 plane-parallel plate

23 plane-parallel plate

25 diffractive structure

27 diffractive structure

101 optical component

103 optical component

105 assembly

106 Aperture stop

107 lens group

108 lens group

109 lens group

110 lens group

111 optical component

113 optical component

115 assembly

Claims

claims

A wavefront manipulator comprising at least a first optical component (1) and a second optical component (3) arranged one behind the other along an optical axis (OA), wherein the first optical component (1) and the second optical component (3) respectively in a direction of movement perpendicular to the optical axis (OA) are arranged movable relative to each other and wherein the first optical component (1) and the second optical component (3) each have at least one refractive free-form surface (5,

7), characterized in that between the first optical component (1) and the second optical component (3) is an immersion medium contacting the two components (1, 3).

2. wavefront manipulator according to claim 1, characterized in that the immersion medium is a liquid.

3. wavefront manipulator according to claim 1, characterized in that the immersion medium is an elastic Optokitt.

4. wavefront manipulator according to claim 3, characterized in that the first optical component (1) and the second optical component (3) in each case in a direction perpendicular to the optical axis (OA) relative to each other by a distance of a maximum

50 pm are movable.

Wavefront manipulator according to one of claims 1 to 4, characterized in that the first optical component (1) and the second optical component (3) consist of the same material and the material of the optical components (1, 3) and the immersion medium satisfy the following condition :

<0.05,

where ni is the refractive index and vi is the Abbe number of the material of the optical components (1, 3), and n _{2 is} the refractive index and v _{2 is} the Abbe number of the immersion medium.

6. wavefront manipulator according to one of claims 1 to 5, characterized in that the first optical component (1) and the second optical component (3) consist of the same material and the material of the optical components (1, 3) and the immersion medium, the following Satisfy conditions:

«, - n ₂ <0.05,

7. wavefront manipulator according to claim 6, characterized in that the material of the optical components (1, 3) glass or plastic and the immersion medium is an organic hydrocarbon, water or an aqueous solution.

8. wavefront manipulator according to claim 7, characterized in that the material of the optical components (1, 3) is plastic and the immersion medium is an alkali-doped aqueous solution.

9. wavefront manipulator according to claim 7, characterized in that the material of the optical components (1, 3) is quartz glass or a crystalline material and the immersion medium is high purity water.

10. wavefront manipulator according to one of claims 1 to 9, characterized in that the structure of the refractive free-form surfaces of the optical components (1, 3) comprises a superposition of at least two structural profiles.

11. wavefront manipulator according to one of claims 1 to 10, characterized in that both the front and the back of an optical component (1, 3) is provided with a refractive free-form surface.

12. wavefront manipulator according to one of claims 1 to 11, characterized in that the refractive free-form surface (5) of the first component (1) is associated with a first diffractive structure (9) and the refractive free-form surface (7) of the second component (3) second diffractive structure (11) is assigned, wherein the associated diffractive structures (9, 11) influence a wavelength-dependent effect of the respective refractive free-form surface (5, 7).

13. wavefront manipulator according to claim 12, characterized in that

the form of a refractive free-form surface (5, 7) is described in each case by a polynomial winding which has development coefficients that are different from zero in finitely many definite polynomial orders,

- The one refractive free-form surface (5, 7) associated diffractive

(9, 11) structure is described by a polynomial winding which has non-zero development coefficients in the same polynomial orders as the polynomial winding of the refractive free-form surface (5, 7), and those development coefficients one refractive

Freiformfläche (5, 7) descriptive polynomial winding and the corresponding diffractive structure (9, 11) descriptive polynomial winding, each of the same polynomial Order are associated with each other in a fixed functional relationship.

Wavefront manipulator according to claim 13, characterized in that the functional relationship depends on the material used in the respective optical component (1, 3).

Wavefront manipulator according to one of Claims 12 to 14, characterized in that the first optical component (1) and the second optical component (3) consist of the same material, the material of the optical components (1, 3) and the immersion medium have refractive indices whose Difference is a linear function of the wavelength, and the material / medium having the lower refractive index has a higher dispersion than the material / medium having the higher refractive index.

Optical device with a wavefront manipulator according to one of the preceding claims.

Use of at least one wavefront manipulator according to one of claims 1 to 15 for bringing about at least one of the group of the following corrections or reductions: dichromatic correction, trichromatic correction, reduction of the secondary spectrum, reduction of the tertiary spectrum.

Use of at least one wavefront manipulator according to one of claims 1 to 15 for effecting a position-dependent correction of at least one wavefront error in a zoom objective.