WO2004025355A1

WO2004025355A1 - Focusing unit of optical device

Info

Publication number: WO2004025355A1
Application number: PCT/RU2003/000353
Authority: WO
Inventors: Oleg Abel
Original assignee: Oleg Abel
Priority date: 2002-09-12
Filing date: 2003-08-07
Publication date: 2004-03-25
Also published as: AU2003263699A1; IL151731A0

Abstract

The principle of creating optical junction with the high-speed changing (µs) of the focal distance (autofocusing) was described. The high-speed changing is achieved with piezoelectric materials. These materials can change the refraction coefficient very fast. The acceptable range of the changing of the focal distance is achieved with using several pitches that appear in graded-index optical elements. That is, the graded-index optical element created from piezoelectric materials can provide with the acceptable speed and the range of the autofocusing.

Description

Focusing unit of Optical Device

Field of the Invention

The present invention relates to the optical devices for measuring, reading and recording, specifically to the devices requiring the high speed of changing the focus distance. •^•

• Background of the Invention

The optical devices of the prior art are designed for the measuring, reading or recording , by means of focusing the beam on the object surface. The focus on the object surface is detected with the sensors as they measure the differences in the intensity of incident light .reflected from the object surface.

US PatEtit 4907024 discloses automatic focus adjusting apparatus for measuring a distance. between the object and the camera. The apparatus comprises an automatic focus motor,' which drives an automatic focus ring through a mechanical transmission including ¹ gear wheels and link members. As a result, the optical lens system is moved forward or

X !• backward along its optical axis thereby focusing the light on a measured object. The

, disadvantage of the apparatus is the certain inertia of the mentioned focus motor, mechanical , transmission, movable focus ring and lens system, restricting the speed of measurement rqcesses.

GB.Patent 2286497 discloses automatic focusing apparatus comprising an optical system having a group of focusing lenses. There is also an automatic focus motor and joint members transmitting the motor rotation to the focus adjusting mechanism for moving the focusing lens unit in the optical axis direction and focusing the lens unit on the surface of measured object The disadvantage of the apparatus is the certain inertia of the mechanical drive system for focusing the lens group, including the motor's rotor, the joint members, the movable parts of the adjusting mechanism and the lens unit. The inertia restricts the speed of the lens group focusing and'the measurement as a whole.

DE Patent 19954684 discloses the method and the device for the measurement of the object surface. An optical sensor of the device including a focusing unit directs a light beam

. onto the surface and detects a light beam reflected from the surface. The co-ordinates of the * rtieasufing point on the surface are determined from the position of the sensor. This position

^:,is maintained by means of the sensor movement so that the light focus always lies on the ".'^'surface. However, the speed of the sensor movement is substantially restricted by the inertia of the sensor and the means for the sensor drive. ^'■^' US Patent 5182444 discloses a measuring apparatus with a split lens, which consists of

,twό. halves separated along the lens optical axis and movable with respect to each other. i These lens halves are displaced from each other along the contact plane to focus the light ^'.'reflected froiB the medium onto light sensors. The disadvantage of the measuring apparatus is" the restricted speed of the measurement caused by the inertia of movable parts during the .; displacement of the lens halves for focusing the light. . US Patent 518929*4.. discloses the transform lens with a plurality of sliced lens segments.

The transform lens is used to focus the optical output signals by displacing lens slices. As in . ^' above cases, the speed of the focusing and the measurement is restricted because of the inertia of movable lens segments and the parts of the lens segment drive.

Thus, the common disadvantage of the optical measurement devises of the prior art is the '•' focusing of the optical systems by means of the mechanical transposition of their optical components, decreasing the speed of the focusing and the measurement as a whole because ' , of the inertia of the movable components. One cycle of the measurement for these devices is in the order of 1 msec. The transposition of the optical components is implemented by |. mechanical driving system including the focus motor, transmitting links, guides etc.,

•complicating. the device design and increasing its cost. Moreover, the presence of movable friction parts leads to reducing the device durability and can create the hazard of part . jamming. The disadvantage of the known optical measurement devices also is the limited range of the variatiαty.-pf measured distances because of the limited diapason of the mechanical transposition inside of the device as well as the absence of the variation of the beam wavelength used for focusing and measurement.

In parallel with aforementioned optical measurement system using the lens optical ^■ elements, there are systems, wherein the optical elements with a graded index of refraction ^•' are used,

US Patent 4030122 discloses an apparatus including a reading means transmitting the ^' , signal through videoprocessing means, beam-forming source of modulated pulses, and hemicyliridrical lens to an optical fiber with a graded index of refraction. The latter is made i of glass, is_. characterized by a parabolic radial index of refraction, and the beam curve inside , "the optical fiber has length in the limit of approximately half of the pitch of this beam curve, the optical fiber is mounted on a support arm, which is deflected to achieve line scan of the • recording medium (screen) and translated to achieve frame scan of one. The distance between the fiber output face and the recording medium as well as focal distance remain constant during scanning of the recording medium. In this case, the optical fiber acts like a serjes of 'spherical lenses to focus the beam onto the recording medium, and for this purpose, its length, equal to half of beam curve pitch, is quite sufficient. Thus, the optical fiber is the equivalent of usual lenses and, taken alone, cannot eliminate the above noted disadvantages of the optical measurement devices.

^' Summary of the Invention

, ;;■ The objective of the present invention is considerable reducing the time needed for focusing the beam of optical device and heightening the speed of the device operation as a .whole.

^: Another objective is substantial extension of the variation range of the focus distances. Another objective is increasing the reliability and durability of the optical device. Another objective is the design simplification and the cost reduction of the optical device. ... The above noted objectives are accomplished by the focusing unit of the optical device comprising a beam source, a beam refracting component to focus said beam onto an object surface, and a focusing means for changing the properties, determining a complex refractive index of the beam refracting component, at least one of two factors including the beam and material of the beam refracting component. The focusing means for changing the properties of. the material of the beam refracting component is a field means creating a field with a controlled field gradient. The beam refracting component is located in this field and the material of beam refracting component is capable of changing the complex refractive index under the action of the field gradient. As a result, the change of the field gradient allows , changing the complex refractive index of the beam refracting component and a focus distance, of the focusing unit. One cycle of the operation with focusing by means of the field gradient arhounts in the, order of 1 mcsec, i. e, three orders less than the mechanical focusing of the prior art systems. Thus, the speed of the device operation considerably increases. Moreover, the field means allows the elimination of the most cumbersome and expensive mechanical drive motors, transmitting mechanisms and links with friction parts inherent in the focusing systems of the prior art. As a result, the design of the optical device is simplified, its the cost is reduced, and its durability and reliability are increased. ■' As a field, the electric, magnetic or electromagnetic field can be applied. As a material of

.the beam refracting component, located in the electrical field, nonpolar dielectric or

. ^{' ■ •} ' ^* , ^{• •} 3 ferroelectric, specifically piezoelectric, can be applied. Their refractive index is variable under the action of the electrical field gradient. As for piezoelectric, also there is the variation of its form and sizes, which additionally change the complex refractive index of the

^• beam refracting component. As a material of the beam refracting component located in the magnetic or electromagnetic field, also ferromagnetic can be used. It is capable of c nsiderable changing the complex refractive gradient of the beam refracting component. As ^"a beam refracting component, an optical element is used, whose refractive index is a

„ graded index of refraction. The optical element is formed with the material layers having . different refractive .indexes, subsequently coated onto one another and creating nonlinear optical structure, which has the radial change of the refractive index, for example according to parabola law, and is characterized by pitch of the beam curve and the steepness of the beam curve. The pitch quantity and the beam curve steepness determine the variation ranges of the focus distance and the needed field gradient. Their required values can be obtained as a result of the mentioned forming the optical element. Therewith it should be taken into account, that increasing the pitch quantity and decreasing the beam curve steepness lead to decreasing the needed range of the field gradient variation and to extending the range of the fp.cus distance variation. As a result, the range of focus distances can be substantially extended in comparison with the prior art.

. As afocusing means, also a beam changing means is used for changing the beam .wavelength emitted by the beam source. The beam changing means of the beam source

. presents the variator with strictly specified sequence of the beam wavelength change. The

, change of the beam, wavelength allows stepped changing the complex refractive, index of the , beam refracting component and the focus distance ranges of the focusing unit. The combined focusing means include the beam changing means for changing the focus distance ranges as well as the field means for the smooth control of the complex refractive index and the focus distance inside of the focus distance ranges. In version embodiment, the combined focusing means include the beam changing means for changing the focus distance ranges as

^' well as a mechanical moving means for transposing the elements of the beam refracting component to smoothly control the focus distance inside of the focus distance ranges. In any case, the use of the beam changing means allows the considerable extension of the focus- - distance range in comparison with the prior art and in comparison with the application of the field means as a singe focusing means.

-Brief Description of the Drawing Fig. 1 schematically shows the focusing unit comprising the optical element with graded refractive ind x disposed in the electrical field with controlled field gradient. Fig. 2 shows the approximate graph of the dependence of focus distance on beam

.^'wavelength λ and field gradient E (electrical field), or H (magnetic field), or the distance L between the focusing unit and an object surface. Fig: 3 schematically shows the optical element with graded refractive index composed of the layers with different refractive indexes n and characterized with beam pitch P as well as diameter D, radius r and length Z of the optical element. Fig. 4 shows parabola characterizing the dependence of refractive index n on radius r of the optical element with graded refractive index. Fig. 5 schematically shows the focusing unit comprising the optical element with graded refractive index disposed in the magnetic field with controlled field gradient. •Fig.^* 6 schematically shows the focusing unit including the beam refracting component in the form of a lens series with the focusing means provided with the mechanical drive as well as the-he m source with variable wavelength.

Detailed Description of the Invention

Referring first to fig. 1, the focusing unit of optical device will be described. Focusing unit 10 comprises beam source 11, the beam refracting component in the form of optical element 12 with graded refractive index, and the focusing means in the form of the field means including electrically charged plates 13, 14 connected to current source 15 through voltage regulator 16. Plates 13, 14 form electrical field 11 whose gradient is controlled by regulator 16. Optical element 12 is disposed in electrical field and its material is capable of chang rigthe complex refractive index of optical element 12 under the action of the gradient of electrical field 17. Beams 18 of beam source 11 pass through optical element 12, which .refracts them and focuses onto object surface 19. Focus is detected with sensor 20, which transmits obtained* data to processing unit 21. The latter judges the differences in the intensity of incident light reflected from object surface 19 and sends a controlling signal to executing unit in the form of voltage regulator 16. Regulator 16 changes the voltage between plates 13, 14, thereby changing the gradient of electrical field 17 and, as a consequence, the refractive index of material of optical element 12. As a result, optical element 12 changes its focus distance. This process continues until beams 18 are focused on object surface 19. Due to the absence of movable parts in focusing unit 10, it is characterized with high focusing speed^'..Specifically, thk ϊme of one cycle of focus change amounts in the order of about 1 mesec j^'that is three orders less than in the focusing units of the prior art.

• ^■ Material of optical element 12 is nonpolar dielectric or ferroelectric whose refractive inde ^'depends oh the gradient of electrical field 17. The presence of such dependence is confirmed with the following known relationship of Klausius - Mosotty for the nonpolar dielectrics:

^' :, .^' , . ^' * (ε - l) / (ε +2) = xe / 3, where: ε - relative dielectrical permeability of material; e- dielectrical susceptibility of material. However ε = n², where n - absolute light refractive index; and xe= Pe/E, where

Pe - vectorial sum of dipole moments of molecules, and E - gradient of electrical field.

Heηce, relationship of Klausius- Mosotty can be presented as follows:

^' " ^' .^' _. , ^• («²- l) / («² + 2) =Pe / 3E.

According to this relationship, the more electrical field gradient E the less refractive index n.

Tlius, the complex reff active index of optical element 12 is changeable under the action of electrical field gradient E. In the version embodiment, material of optical element 12 is piezoelectric, which is the variety of ferroelectric and allows changing the complex refractive index, of optical element 12 due to the variation of both the material refractive index and the form and sizes of optical element 12 under the action of the change of the electrical field gradient E.

:. Fig. 3 allows the detailed explanation of the design of the optical element 23 with graded refractive index similar to optical element 12 in fig. 1. Optical element 23 is formed with material layers 24, 25, 26, 27, 28 being the varieties of nonpolar dielectric or ferroelectric having different refractive indexes no, m, nx_im_im_i respectively. These layers are subsequently coated onto one another and create nonlinear optical structure. The choice of layer number, their thickness and values n allows forming the optical structures with various laws of the dependence of n on radius r, specifically according to parabola law (shown in fig. 4). In this case, beaiii curve 29 (fig. 3) is characterized by pitch P and curvature radiuses

R of mentioned parabola 30 (fig. 4). According to the parabola law, refractive index of the optical^' element decreases from maximal value in central layer 24 to minimal value m in peripheral layer 28. The smooth transition from one material layer to another allows obtaining the smooth line of parabola 30, as it is shown in fig. 4. The abrupt transitions

^•between the material layers allow obtaining the stepped line, which approximately corresponds to the parabola law. The optical element 23 also is characterized with its length ", Z and diameter D. There is following know relationship between the parameters of such ' optical element: 2πP = Z" A, where A is gradient constant of the optical element with the ^• gradient refractive, i_.i^iex. The parabola curvature radius R in arbitrarily taken point M is equal: R = m³/p², where m is line MK normal to the tangent to parabola 30 in point M,p is line FB parallel to axis r and disposed between parabola focus F and point B on parabola.. Values R are, determined by the refractive indexes no- m of material layers 24-29: the more refractive indexes the less R, and in turn, the less R the more pitch quantity. R also determines the steepness of the beam, curve: the less R the more steepness of lateral branches . of beam curvature 29. This steepness, specifically as applied to right output branches 33, 34 . of beam curves 31, 32, respectively (fig. 1), determines range λi of the focus distances upon preset ranges of the controlled field gradients E and the complex refractive indexes. The .^' steepness also determines the needed range of the controlled field gradients E and the - complex refractive indexes upon preset range λi. The less R and, consequently steeper ^'. ^'branches 33, 34, the more range λi and the less needed range of controlled field gradients E. '.The pitch quantity is determined with R, as it was noted above, as well as with length Z of ' ^• the optical el ementi.^'I turn, the pitch quantity determines range λi and the needed range of the field gradients E. As is clear from fig. 1, the more pitch quantity the more displacement of the right end of beam curves 31, 32 leading to increasing the focus distance range and decreasing the needed range of the field gradients. Thus, optical element 23 is formed to obtain the quantity of the pitches P and the values of parabola curvature radiuses R, which allow using the needed ranges of the smooth variation of the field gradient E and the focus distance. Therewith, it should be taken into account, that increasing the pitch quantity and . decreasing parabola curvature radiuses R lead to decreasing the needed range of the field gradient variation and to extending the range of the focus distance variation. The recommended pitch quantity amounts at least not less one entire pitch. The limit of the " increase of the pitch quantity and the decrease of R is the excessive sensitivity of the focus ^■ distance variation to the change of the field gradient leading to lowering the measurement . accuracy.

• In version embodiment, the focusing means of focusing unit 10 includes a beam changing ' means for changing the beam wavelength emitted by beam source 11. The beam changing means is capable of generating four beam varieties with various wavelengths λi, λi, λs, λ*. Refractive index n of optical material depends on the beam wavelength so that the more wavelength the less n. This dependence lead to the stepped change of the complex refractive index of optical element 12 and, as a consequence, to stepped changing the variation range of the focus distance of the focusing unit as a result of changing the beam wavelength. Fig. 1 shows four such ranges of the focus distances - λi, λ2, λa, 1A, designated according to the beam wavelengths, which have formed them. If, for example in range λi, the beam focusing was not achieved, processing unit 21 switches beam source 11 to subsequent range λ2 and

, the focusing unit attempts to focus the beam inside of range λ2 by changing the electrical field gradient E. Therewith, changing the beam wavelength λ is used for changing the focus distance ranges and changing the electrical field gradient E is used for the smooth control of the focus distance inside of the focus distance ranges. Fig. 2 shows the general graph of the focus^d^'istarice control implemented by changing both beam wavelength λ and electrical field gradient E. Changing the beam wavelength allows considerable extending the total diapason

. of the focus distance control without applying the movable part of focusing unit, thereby maintaining the highspeed of beam focusing.

Fig. 5 shows focusing unit 110 comprising beam source 111, the beam refracting component in the form of optical element 112 with graded refractive index and the focusing means in the form of the field means. The latter includes north magnetic pole 113 and south magnetic pole 114 of electromagnet 135 having electric winding 136 connected to current source 115. through regulator 116. Poles 113, 114 form magnetic field 117 whose gradientH is controlled by regulator 116. Optical element 112 is disposed in magnetic field 117 and its material is capable of changing the complex refractive index of optical element 112 under the action of gradient H of magnetic field 117. Beams 118 of beam source 111 pass through optical element 112, which refracts them and focuses onto object surface 119. Focus is deteςted with sensor 120, which transmits obtained data to processing unit 121. The latter judges the difference in the intensity of incident light reflected from object surface 119 and sends a controlling signal to executing unit in the form of regulator 116. Regulator 116 changes gradient H 'o magnetic field 117 between poles 113, 114 and, as a consequence, the refractive index of material of optical element 112. As a result, optical element 112 changes its focus distance. This process continues until beams 118 are focused on measured surface 119.^' Due to the absence of movable parts in focusing unit 110, it is characterized with high focusing speed similar to focusing unit 10 in fig. 1.

Optical element 112 is formed with material layers having different refractive indexes* subsequently coated onto one another and creating nonlinear optical structure. This structure has refractive index n depending on radius r of the optical element and is characterized by pitch P and the steepness of the beam curve. In the case of parabolic dependence of n on r, the steepness is determined by curvature radiuses R of mentioned parabola. Mainly, the ■properties of optical elements 12, 23, described for figs. 1, 3, 4, are also inherent in optical element .112 in fig. 5/ with the exception of material of the optical element. Material of Optical element 112 is ferromagnetic whose refractive index depends on gradient H of . magnetic field 117. The more gradient H the less refractive index of ferromagnetic.

In version embodiment, the focusing means of focusing unit 110 includes the beam , .changing means for changing the beam wavelength emitted by beam source 111. All description relating to the design and operation of the beam changing means of the version, /shown in fig. 1, also relates to fig. 5. Therewith, changing the beam wavelength λ is used for , changing the focus distance ranges and changing the magnetic field gradient H is used for , the smooth control of the focus distance inside of the focus distance ranges. Fig. 2 shows the •general graph of the focus distance control of focusing unit 110 implemented by changing , both beam wavelength λ and magnetic field gradient H.

,.! The versions of focusing units 10 and 110 have approximately the same advantages, , Fig. 6 shows the focusing unit 210, wherein beam refracting component 238 comprises ^' the series of spherical lenses 239, 240, 241. The focusing means includes beam source 211 ^' with variable beam wavelength for stepped changing the ranges of the focus distances and , mechanical moving means 242 for transposing the beam refracting component 238 to , smooth control the focus distance inside of the ranges determined by beam source 211. . 'Mechanical moving means 242 includes drive motor 243, gear transmission 244 and carrier 245 of beam refracting component 238 movable in guide 246. Beam source 211 comprises . thfe beam changing means in the form of exchangeable beam sources 247, 248, 249, 250 , with different wavelengths λi, λz, λs, λ4, respectively, and variator 2 1 with strictly specified , ; sequence^', of the beam wavelength change. For every wavelength there is corresponding to it range of the focus distances designed with the designation of its wavelength. Altogether, n. ^* . ^{' ■ •*}

'there are four such ranges - λi, λ2, λs, λ4, shown in right portion of fig. 6. Beams 218 of beam source 211 pass through lenses 239-241, which refract them and focus onto object surface 219. The focus is detected with sensor 220, which transmits obtained data to processing unit 221. The latter judges the differences in the intensity of the incident light reflected from object surface 219 and sends a controlling signal to executing unit in the form of drive motor .•243. Drive motor 243 displaces lenses 239-241, thereby changing the focus distance. If the .beam focusing was not achieved, processing unit 221 switches exchangeable beam sources _: '.'247-250 to subsequent range of the focus distances by variator 251 with strictly specified sequence of the beam wavelength change. Then, mechanical moving means 242 again 'attempts to focus the beam inside of the new range. This process continues until beams 218 .are focused on object surface 219. Fig. 2 shows the general graph o focus distance control ^: of focusing unit 210 implemented by changing both beam wavelength λ and distance L ¹ between focusing unit 210 and object surface 219.

^' , Using the beam changing means allows reducing the needed diapason of mechanical ■^' transposition of beam refracting component 238, thereby reducing the needed time for the beam^' focusing. Moreover, the beam changing means substantially extends the total range of

* the focus distances of focusing unit.210.

^■ In version embodiment (not shown), focusing unit 10, shown in fig.1, comprises the beam refracting component in the form of a lens series similar to shown in fig.6 instead of optical element 12. Material of these lenses is nonpolar dielectric or ferroelectric, specifically .piezoelectric. . ' , In version embodiment (not shown), focusing unit 110, shown in fig. 5, comprises the :^' beam refracting component in the form of a lens series similar to shown in fig.6 instead of

* optical element 112. Material of these lenses is ferromagnetic.

In version embodiments, focusing units 10, 110, 120, shown in figs. 1, 5, 6, comprise the . beam 'source with variable beam wavelength including the wavelengths, which are disposed beyond the visible portion of electromagnetic wave spectrum.

In version embodiments, focusing units 10, 110, shown in figs. 1, 5, comprise the beam Source emitted the 'beam of only one wavelength. ^•

, ,lh version embodiment (not shown), the optical element with graded refractive index is disposed in the electrical and magnetic fields created with the field means, which include the electrically charged plates similar to plates 13, 14, shown in fig, 1, and magnetic poles , similar to poles 113, 114, shown in fig. 5.

In version embodiments, focusing units 10 an 110, shown in figs. 1, 5, are provided with ^'the beam changing means in the form of exchangeable beam sources 247, 248, 249, 250 with different wavelengths λi, λi, λa, λ-t, respectively, and variator 251 with strictly specified sequence of the beam wavelength change, shown in fig, 6.

The means for the focus detection, for processing the beam reflected from the object surface and generating the signal controlling the focusing means, schematically presented in the present invention in the form of sensors 20, 120, 220, processing units 21, 121, 221 (figs. 1, 5, 6), and variator 251 do not relate to the subject of the present invention, are in principle , known and can be developed by ordinary specialist skilled in the art.

Claims

Claims:

1. A focusing unit of an optical device, including:

• a source of a beam, - a beam refracting component to focus said beam onto an object surface,

• a focusing means for changing the properties, determining a complex retractive index of said beam refracting component, of at least one of two factors including said beam and material of said beam refracting component.

2. The focusing unit of claim 1, wherein said focusing means is a field means creating a field with a controlled field gradient, said beam refracting component is located in said field, and said material of beam refracting component is capable of changing said complex refractive index under the change of said field gradient and thereby of changing said complex refractive index of beam refracting component and a focus distance of said focusing unit.

3. The focusing unit of claim 1, wherein said focusing means is a beam changing means for changing the beam wavelength emitted by said beam source and thereby for stepped changing said complex refractive index of beam refracting component and focus distance ranges of said focusing unit.

4. The focusing unit of claims 2, 3, wherein said focusing means include said beam changing means for changing said focus distance ranges as well as said field means for the smooth control of said complex refractive index and said focus distance inside of said focus distance ranges.

5. The focusing unit of claim 3, wherein said focusing means include said beam changing means for changing said focus distance ranges, as well as a mechanical moving means for transposing the elements of said beam refracting component to smoothly control the focus distance inside of said focus distance ranges.

6. The focusing unit of claim 1, wherein said beam refracting component presents a series of spherical lenses.

7. The focusing unit of claim 1, wherein said beam refracting component presents an optical element whose refractive index is a graded refractive index.

8. The focusing unit of claim 7, wherein said optical element with graded refractive index is formed with the layers of material having different refractive indexes, subsequently coated onto one another and creating nonlinear optical structure, which has the radial change of said refractive index and is characterized by pitch and steepness of the curve of said beam.

9. The focusing unit of claim 8, wherein said radial change of said refractive index substantially corresponds to parabola law and said steepnes of beam curve is determined with curvature radiuses of said parabola.

10. The focusing unit of claims 2, 8, wherein said optical element with graded refractive index is formed to obtain the quantity of said pitches and the character of said beam curve steepness, which allow the use of the needed ranges of the smooth variation of said field gradient and focus distance, taking into account that increasing said pitch quantity and said steepness lead to decreasing said needed range of field gradient variation and to extending said range of said focus distance variation.

11. The focusing unit of claims 2, wherein said field is electrical field.

12. The focusing unit of claims 2, wherein said field is magnetic field.

13. The focusing unit of claims 2, wherein said field is electromagnetic field.

14. The focusing unit of claims 11, wherein said material of beam refracting component is nonpolar dielectric.

15. The focusing unit of claims 11, wherein said material of beam refracting component is ferroelectric.

16. The focusing unit of claim 15, wherein said material of beam refracting component is piezoelectric, changing said complex refractive index of beam refracting component due to the variation of both the material refractive index and the form and sizes of said beam refracting component under the change of the gradient of said electrical field.

17. The focusing unit of claims 12, 13, wherein said material of beam refracting component is ferromagnetic.

18. The focusing unit of claim 3, wherein said beam changing means of said beam source comprises several sources of the beam of different wavelength, which are switched from one to another by means of a variator with strictly specified sequence of the beam wavelength change.

19. A focusing unit of an optical device, including:

• a source of a beam of at least one wavelength,

• a beam refracting component to focus said beam onto an object surface,

• a focusing means in the form of a field means creating a field with a controlled field gradient, • said beam refracting component is located in said field, and

• material of said beam refracting component is capable of changing a complex refractive index of said beam refracting component under the change of said field gradient and thereby of changing a focus distance of said focusing unit.

20. The focusing unit of claim 19, wherein said focusing means also includes a beam changing means for changing the beam wavelength emitted by said beam source and thereby for stepped changing said complex refractive index of beam refracting component and focus distance ranges of said focusing unit, therewith said beam changing means is used for changing said focus distance ranges and said field means is used for the smooth control of said complex refractive index and said focus distance inside of said focus distance ranges.

21. The focusing unit of claim 19, wherein said beam refracting component presents a series of spherical lenses.

22. The focusing unit of claim 19, wherein said beam refracting component presents an optical element whose refractive index is a graded refractive index.

23. The focusing unit of claim 22, wherein said optical element with graded refractive index is formed with the material layers having different refractive indexes, subsequently coated onto one another and creating nonlinear optical structure, which has the radial change of refractive index and is characterized by pitch and steepness of the curve of said beam.

24. The focusing unit of claim 23, wherein said radial change of said refractive index substantially corresponds to parabola law and said steepnes of beam curve is determined with curvature radiuses of said parabola.

25. The focusing unit of claims 22, wherein said optical element with graded refractive index is formed to obtain the quantity of said pitches and the character of said steepness, which allow the use of the needed ranges of the smooth variation of said field gradient and focus distance, taking into account that increasing said pitch quantity and said steepness lead to decreasing said needed range of complex field gradient variation and to extending said range of focus distance variation.

26. The focusing unit of claims 19, wherein said field is electrical field.

27. The focusing unit of claims 19, wherein said field is magnetic field.

28. The focusing unit of claims 19, wherein said field is electromagnetic field.

29. The focusing unit of claims 26, wherein said material of beam refracting component is nonpolar dielectric.

30. The focusing unit of claims 26, wherein said material of beam refracting component is ferroelectric.

31. The focusing unit of claim 30, wherein said material of beam refracting component is piezoelectric, which allows changing said complex refractive index of beam refracting component due to the variation of both the material refractive index and the form and sizes of said beam refracting component under the action of the gradient of said electrical field.

32. The focusing unit of claims 27, 28, wherein said material of beam refracting component is ferromagnetic.

33. The focusing unit of claim 20, wherein said beam changing means of said beam source comprises several sources of the beam of different wavelength, which are switched from one to another by means of a variator with strictly specified sequence of the beam wavelength change.

34. A focusing unit of an optical device, including:

• a source of a beam, • a beam refracting component to focus said beam onto an object surface,

• a focusing means in the form of a beam changing means for changing the beam wavelength emitted by said beam source and thereby for stepped changing a complex refractive index of said beam retracting component and focus distance ranges of said focusing unit.

35. The focusing uivit of claim 34, wherein said beam changing means of said beam source, comprises several sources of the beam of different wavelength, which are switched from one to another by means of a variator with strictly specified sequence of the beam wavelength change.

36. The focusing unit of claim 34, wherein said focusing means includes also a field means creating a field with a controlled field gradient, said beam refracting component is located in said field, and material of said beam refracting component is capable of changing said complex refractive index under the change of said field gradient and thereby of changing said complex refractive index of beam refracting component and a focus distance of said focusing unit, therewith said beam changing means is used for changing said focus distance ranges and said field means is used for the smooth control of said complex refractive index and said focus distance inside of said focus distance ranges.

37. The focusing unit of claim 34, wherein said focusing means includes also a mechanical moving means for transposing the elements of said beam refracting component to control the focus distance, therewith said beam changing means is used for changing said focus distance ranges and said mechanical moving means is used for the smooth control of said focus distance inside of said focus distance ranges.

38. The focusing unit of claim 34, wherein said beam refracting component presents a series of spherical lenses.

39. The focusing unit of claim 34, wherein said beam refracting component presents an optical element whose retractive index is a graded refractive index.

40. The focusing unit of claim 39, wherein said optical element with graded refractive index is formed with the material layers having different refractive indexes, subsequently coated onto one another and creating nonlinear optical structure, which has the radial change of refractive index and is characterized by pitch and steepness of the curve of said beam.

41. The focusing unit of claim 40, wherein said radial change of said refractive index substantially corresponds to parabola law and said steepnes of beam curve is determined with curvature radiuses of said parabola.

42. The focusing unit of claims 36, 40, wherein said optical element with graded refractive index is formed to obtain the quantity of said pitches and the character of said steepness, which allow the use of the needed ranges of the smooth variation of said field gradient and focus distance, taking into account that increasing said pitch quantity and said beam curve steepness lead to decreasing said needed range of field gradient variation and to extending said range of focus distance variation.

43. The focusing unit of claims 36, wherein said field is electrical field.

44. The focusing unit of claims 36, wherein said field is magnetic field.

45. The focusing unit of claims 36, wherein said field is electromagnetic field.

46. The focusing unit of claims 43, wherein said material of beam refracting component is nonpolar dielectric.

47. The focusing unit of claims 43, wherein said material of beam refracting component is ferroelectric.

48. The focusing unit of claim 47, wherein said material of beam refracting component is piezoelectric, which allows changing said complex refractive index of beam refracting component due to the variations of both the material refractive index and the form and sizes of said beam refracting component under the action of the gradient of said electrical field.

49. The focusing unit of claims 44, 45, wherein said material of beam refracting component is ferromagnetic.