WO2003102636A1

WO2003102636A1 - Variable-focus lens and lens controller

Info

Publication number: WO2003102636A1
Application number: PCT/JP2003/006509
Authority: WO
Inventors: Masatoshi Ishikawa; Hiromasa Oku
Original assignee: Masatoshi Ishikawa; Hiromasa Oku
Priority date: 2002-06-04
Filing date: 2003-05-26
Publication date: 2003-12-11
Also published as: JPWO2003102636A1; AU2003235425A1

Abstract

A variable-focus lens that responses at the frame rate of a high-speed visual system, and it controller. A variable-focus lens (10) comprising a container (11) filled with liquid thereinside. The container (11) comprises a pressure transmitting part (15) kept in contact with an actuator (14) to transmit its vibration, and two light transmitting parts (12, 12) on light incoming and outgoing surfaces. A surface portion, capable of being displaced convexly and concavely in an optical axis direction in response to a displacement imparted from the pressure transmitting part (15) via liquid, is provided on at least one of the light incoming and outgoing surfaces, with a ratio (s/S) between the area s of the surface portion and that S of the pressure transmitting part (15) being up to a specified value, thereby changing a focal distance when the surface portion displaces in response to the displacement of the actuator (14).

Description

Specification

Variable focus lens and lens control device TECHNICAL FIELD

The present invention relates to a varifocal lens capable of changing focus at high speed and a control device thereof.

Background art

Recently, a high-speed vision capable of obtaining and processing an image at high speed at a frame rate of 1 k H z, massively parallel typified by S ³ PE. Ultra-high-speed vision chips are attracting attention. In such high-speed vision, an optical system composed of a lens such as a photographic lens or a telescope is often used for image formation. If the optical system is configured in combination with a varifocal lens that can control the focal length of the lens, a focusing mechanism and a zoom mechanism can be realized, and by actively using such a dynamic optical system, It is expected that new applications for high-speed vision systems can be explored.

In order to capture an object with different optical characteristics for each frame of such a high-speed vision system, the varifocal lens must also have a response of 1 kHz or more.

However, the conventional varifocal lens is much slower than the high-speed vision frame rate of 1 kHz, which impairs the speed of high-speed vision. For example, "A new, compact and quick -response dynamic iocu sing lens (Takashi Kaneko et. Al R TRANSDUCERS '97, Vol. 1, p. 63 -66, 1997)" has the highest response speed, about 1 Variable focus lenses have been proposed that are 50 Hz. However, the response of such varifocal lenses is an order of magnitude smaller than the frame rate of high-speed vision, and there are significant speed limitations in applications that use optical systems.

An object of the present invention is to provide a variable focus lens which responds at a frame rate of a high-speed vision system, and a control device thereof.

Disclosure of the invention

The present inventors have devised a structure of a varifocal lens capable of controlling a focal length at a rate of 1 kHz as described below. Roughly speaking, this variable focus lens is A transparent liquid is sealed inside a rigid container, and an elastic circular thin transparent plate is attached to the surface of the container, which is used as the lens surface. Separately from the lens surface, an elastic partition for applying pressure to the liquid inside is attached. In this specification, this part is called a cylinder part or a pressure transmitting part.

The focal length is controlled by applying pressure to the liquid inside from the outside through the cylinder to deform the lens surface. The liquid inside has two roles, the medium that refracts light and the transmission of force. Fig. 1 shows the principle of how the varifocal lens changes the focal length. As shown in Fig. 1, by driving the actuator 14 in the direction of pressing the liquid (the direction of arrow A), the elastically deformable thin and transparent plates (lens surface) 12 and 12 are convex. , Thereby forming a convex lens. On the other hand, by driving the actuator 14 in the direction of drawing in the liquid (the direction of arrow B), the thin and transparent plates 12 and 12 become concave, thereby forming a concave lens. At present, one of the varifocal lenses according to the present invention, which can be used as an actuator that satisfies the high speed characteristic, has a resonance frequency of about several tens of kHz and positioning on the order of n (nano) m There is a stacked piezo akuchie that is possible. This type of actuary, which has a resonance frequency of several + kHz, has a movable range of only about 10 / m. Therefore, in the present invention, the area of the part where the actuator applies pressure to the liquid is designed to be sufficiently larger (for example, about several tens times) than the area of the lens surface. By adopting such a structure, the lens surface can be deformed by amplifying the displacement of the actuator.

In addition, since the cylinder and the lens surface need to vibrate at high speed, they were designed to have a sufficiently high natural frequency compared to the desired response speed.

More specifically, an object of the present invention is to provide a container in which a liquid is filled, wherein the pressure transmitting portion is configured to come into contact with the actuator and transmit the vibration of the actuator, and to receive light. A container provided with two light transmitting portions on a surface and an emission surface, and at least one of the incident surface and the emission surface is provided with a light in response to a displacement given from the pressure transmitting portion via a liquid. One or more surface portions that can be displaced unevenly in the axial direction, and a ratio (s / S) of an area s thereof to an area S of the pressure transmitting portion is equal to or less than a predetermined value. Such a surface portion is provided, and the focal length is changed by displacing the surface portion in response to the displacement of the actuator, thereby achieving a variable focal length lens.

According to the present invention, the displacement from the actuator applied to the pressure transmitting section by S / s times appears as the displacement of the surface portion. Therefore, even if it has a high-speed response, such as a piezo-stacked actuator (PZT), its surface area can be sufficiently displaced in the optical axis direction even if a small movable range is used. , The focal length can be changed on the order of 1 kHz. A flexible or elastic surface portion may be formed on both the entrance surface and the exit surface, or may be formed on only one of the surfaces and the other may be a rigid surface.

In a preferred embodiment, in the container, the diameter is expanded toward one end, a pressure transmitting portion is arranged at the expanded end, and a portion near the other end has a single diameter. Then, opposing entrance and exit surfaces are formed. With such a configuration, it is possible to form a compact varifocal lens having a sufficient response performance.

In a more preferred embodiment, a projection is formed on a surface of the pressure transmitting portion that is in contact with the actuator. The projection has a cross shape. By configuring the pressure transmitting section in this manner, the resonance frequency is increased, and the liquid in the container can be pushed out or pulled back efficiently with respect to the actuating-evening displacement.

In another preferred embodiment, the container has a first portion including the first pressure transmitting portion and the incident surface in contact with the first actuator, and a second portion in contact with the second actuator. A second portion including the pressure transmitting portion and the exit surface, and a connection surface in which the first portion and the second portion are in close contact with each other at least at a position facing the entrance surface and the exit surface. Displaceable in any combination of the entrance surface of the first portion and the connection surface, the entrance surface of the first portion and the exit surface of the second portion, and the connection surface and the exit surface of the second portion A surface portion is formed. By adopting such a two-layer structure, the degree of freedom is "2", and the driving of each actuary allows only the focal length to be used. It is also possible to correct aberrations.

For example, the connection surface and the emission surface may be formed of materials having different refractive indexes, and the connection surface and the liquid may be formed of materials having different refractive indexes. Is also good.

Further, the first portion and the second portion may be filled with liquids having different refractive indexes. Thereby, for example, chromatic aberration can be corrected. In still another preferred embodiment, the container has a first portion including the first pressure transmitting portion and the incident surface that is in contact with the first actuator, and a first portion that includes the n-th actuator. (N-2) intermediate portions interposed between the first portion and the n-th portion, the n-th portion including the n-th pressure transmitting portion and the emission surface; i (i = 2 ₃ 3,..., (n−2))) and an intermediate portion including an i-th pressure transmitting portion in contact with the actuator. A connection surface is formed in close contact with a portion facing the emission surface, and a displaceable surface portion is formed in each of the incident surface, the connection surface, and the Z or emission surface. By adopting such a multilayer structure, the degree of freedom can be further increased in some cases, and the imaging capability of the lens can be further improved. In the above-described example, the first portion, the (n−2) intermediate portions, and the n-th portion may be filled with liquids having different refractive indexes. Further, as in the previous embodiment, the connection surface and the emission surface may be formed of materials having different refractive indices, respectively, and the connection surface and the liquid may be formed of materials having different refractive indices. It may be formed.

Even in a multi-layer structure of two or more layers, the diameter of each part (first part, middle part, etc.) that constitutes the container increases toward the pressure transmitting part where the actuator contacts. A structure may be adopted. As a result, it is possible to provide a lens that can be variously controlled without increasing the size of the lens so much.

In another preferred embodiment, a plurality of surface portions are arranged on the entrance surface and / or at least one in a predetermined geometric arrangement. Said surface portion is It has a diameter of several tens / several hundreds / m, and a microlens is formed by a surface portion formed on one of the entrance surface and the exit surface, or an opposing pair of surface portions formed on both. May be. Alternatively, the surface portion is a rectangular shape elongated in the longitudinal direction having a width of several tens to several hundreds of meters, and is formed on one or both of the entrance surface and the exit surface. A microlens may be formed by the surface portions of the pair facing each other. In the example of a rectangular microlens, it is desirable that the surface portions are arranged so that the longitudinal sides are almost touching.

Further, an object of the present invention is to provide a lens control device characterized by comprising the above-mentioned variable focus lens, a control unit for supplying a signal for driving each actuator, and an amplifier for amplifying each of the signals. Is also achieved by

The control unit may receive a displacement of the actuator as feedback. Utilizing this feedback, the level of the drive signal for the factories can be controlled. Furthermore, a lens displacement measuring unit that measures displacement in the surface portion may be further provided, and the displacement of the surface portion may be feed-packed to the control unit. The lens displacement may be used to control the level of the drive signal for the above-mentioned factor. In addition, it is possible to feed back the distortion of the lens by these feedback signals, thereby realizing more appropriate control. The lens surface distortion is measured indirectly by estimating the displacement of the actuator. Feedback can be provided, and it can also be realized by directly measuring from the displacement of the surface part.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating the principle of a variable focus lens according to the present invention.

FIG. 2 is a perspective view schematically showing the variable focus lens according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating the structure of the pressure transmitting unit according to the present embodiment in more detail. FIG. 4 is a graph showing characteristics of a material used in the variable focus lens according to the present embodiment.

FIG. 5 schematically shows the variable focus lens and its control device according to the present embodiment. This is a block diagram.

6A and 6B are diagrams showing the structure of a prototype of the variable focus lens according to the present embodiment.

Figure 7 is a Bode plot of the frequency response measured on the prototype.

8A to 8D are diagrams each showing an example of a multi-layered variable focal length lens in the present embodiment.

9A and 9B are diagrams each showing an example of a multi-layered variable focal length lens in the present embodiment.

FIG. 10 is a diagram for explaining the relationship between the pressure transmitting body according to the present invention and a surface portion.

FIG. 11 is a diagram schematically showing an example of a microscope using the variable focus lens according to the present invention.

FIG. 12 is a perspective view of a varifocal lens according to another embodiment of the present invention.

FIG. 13 is a diagram for explaining a lens surface portion of a variable focus lens according to another embodiment of the present invention.

FIGS. 14A and 14B are diagrams showing an application example of such a micro variable-focus lens array.

FIG. 15 is a diagram showing a variable focus lens according to still another embodiment of the present invention, and shows an example in which a lens having an asymmetry is employed.

FIG. 16 is a diagram showing an example of a microvariable focus lens array in which lens surface portions each having an elongated rectangular shape are arranged in one direction.

BEST MODE FOR CARRYING OUT THE INVENTION

[Lens outline]

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a perspective view schematically showing the variable focus lens according to the embodiment of the present invention. As shown in FIGS. 1 and 2, the varifocal lens 10 according to the present embodiment includes a rigid container 11. The container 11 has, for example, a diameter that increases toward one end, and has an adhesive surface at its end that is in close contact with the actuator 14. The contact surface is The opening is formed to secure a large area, and a film 15 made of a thin material is formed so that vibrations of the actuator can be transmitted to the inside of the container. This part is also called a cylinder part. The other end of the actuator 14 has at least one (two in the present embodiment) opening for a lens surface portion. This opening has a circular shape, for example, and a lens surface portion 12 made of a thin and transparent plate that can be elastically deformed is arranged therein. It is desirable that the area of the contact surface 13 be sufficiently larger than the area of the lens surface portion 12 and that the lens surface portion be deformed by sufficiently amplifying the displacement of the actuator transmitted to the contact surface. In other words, the contact surface functions as a pressure transmitting section that applies displacement for changing the focal point of the lens, while the lens surface portion functions as a receiving section that receives displacement from the pressure transmitting section. Hereinafter, the film formed on the contact surface is referred to as a pressure transmitting unit.

Further, the inside of the container 11 is filled with a liquid for transmitting the displacement of the actuator. The refractive index of this liquid is preferably the same as the refractive index of the lens surface portion 12. For example, emulsion oil can be used as the liquid to be filled.

In the present embodiment, a stacked piezo evening is used as the evening 14. The stacked piezo-electric device can be driven accurately with a frequency of 1 kHz or more, but the movable range is as small as several / z m. Therefore, as described above, the area of the pressure transmitting section is made sufficiently larger than the area of the receiving section, and the displacement of the layered Piazochiue is amplified at an amplification factor corresponding to the area ratio and transmitted to the receiving section. are doing.

FIG. 3 is a diagram showing the structure of the pressure transmitting portion formed on the contact surface in more detail. As shown in FIG. 3, the pressure transmitting portion (membrane) 15 according to the present embodiment is made of a metal material (for example, SUS304) and has a radius of 20 mm and a thickness of 0.5 mm. It is the size. Further, a cross-shaped projection 16 is formed at the center of the surface of the film 15 facing the actuator, so that the magnification of the lens displacement is increased. The protrusion is 20 mm long, 2 mm wide, and 0 height. It is 8 mm in size. By contacting this protrusion with the activist, the liquid in the container 11 is efficiently pushed out, Or you can pull in. The adoption of such a structure also has the effect of increasing the resonance frequency.

Hereinafter, the principle of the variable focus lens according to the present invention will be described.

[Principle of the present invention. Lens surface]

The surface of the lens is required to have a high natural frequency that enables high-speed response, flexibility to sufficiently deform under the pressure generated by piezo-electricity, and optical performance as a lens. These are described below. In describing the natural frequency and flexibility, it is assumed that the shape of the lens surface is disk-shaped and the periphery is fixed.

Hereinafter, a radius of the disc a [m], a thickness d [m], the density of the material of the disk p [kg / m ^3], the Young's modulus and record the E [GP a] _s Poisson's ratio.

Based on this, we clarify the relationship between the natural frequency of the disk and the flexibility. First, the natural vibration of a fixed disk is described.

So far, we have described the "natural frequency", but strictly speaking, it is about the first-order natural frequency. This is because in order for the disk to function as a lens, it must vibrate in a point-symmetrical shape, and it is necessary that only one vibration mode be excited. Hereinafter, the natural frequency simply refers to the first-order natural frequency.

When the circumference of this disk is completely fixed, the first natural frequency is

m, _n = k ² _m , _N V ~ (D / μ) (m, n = 0, 1, 2 °

. · · (1). (In the present specification, (a) indicates that (a) is ^1/2 . (“A” means a numerical value or a mathematical expression.))

j = ρά D = E d ³ / (1 2 (1—so ² ).

k _m, nヽ

I _m (ka) J _{m →} (ka)-J _m (ka) l _{m →} (ka) = 0

(Where I _m : m-th modified Bessel function of the first kind J _m : m-th Wessel function of the first kind)

Correspond to n = 0 ₃ 1 ₃ 2, · · · numbered in ascending order. In the present invention, since only the first-order natural frequency is focused on, only the case where m = 0 and n = 0 is considered, and hereinafter, it is simply described as k (= k _0> o).

Next, when the pressure P [Pa] is applied from one side of the disk, the curvature formed by the center of the disk and the focal length corresponding to the curvature are described.

pressure! ^{3 The} radius of curvature r _{c at} the center when [P a] is added

_{r c = (1 6D) /} (a 2 P). . . (3)

It is represented by

In this case, assuming that the refractive index inside the lens is n and the outside is air (refractive index 1), the focal length f at the center satisfies the following relationship.

l / f = ((a ² (n-1)) / (16D)) P

When the lens surface is flat, 1 / f is 0 (zero) because the focal length becomes ∞. If the lens surface is slightly distorted, the focal length becomes a finite large value, and 1 / f becomes a very small number. In other words, 1 / f indicates that the larger the lens surface, the more deformed the lens surface. The index S of deformability with respect to unit pressure is

S = (l / f)-(l / P) = (a ² (n-1)) / (16D)

…(Five)

Is defined. The larger the value of S, the more easily it deforms in response to pressure, and is considered to represent flexibility.

From the natural frequency ω and the flexibility index S, it can be seen how much the parameter of the disk contributes to the primary natural frequency ω and the flexibility index S. From these, we explain how the design can increase the first-order natural frequency and increase the flexibility.

Among the parameters of the disk, there are three choices in the design: radius (a), thickness (d), and material (E ₃ p, v). First, consider the radius (a). Since the radius (a) is determined by equation (2), the following relationship is satisfied.

k∞ l / a (6)

Therefore, the explanation will be made here assuming that the first-order natural frequency ω is inversely proportional to the square of the radius, and the flexibility index S is proportional to the square of the radius. ωοο ΐ / a ² ''. (7)

S∞a ² ·, '(8)

Similarly, considering the thickness d, the first-order natural frequency ω is proportional to the thickness, and the flexibility index S is inversely proportional to the cube of the thickness.

ωοοά · · ■ (9)

Soc l / d ³

Finally, consider the materials. First, for the sake of explanation, if the first-order natural frequency ω is described in the parameters for the material,

w = k ² d ((1 / (1 2 (1-ν ² ))) · (Ε /)). . . (11). Extracting only the parameters related to the material overnight,

ωοο "(Ε / (ρ (1-ν ² ))) '·-(1 2)

It is.

Efficiency, that is, the parameter that is less likely to lose flexibility when the natural frequency is increased is the radius.If the radius is halved, the natural frequency is 4 times, and the index of flexibility is 1/4 times.

The material is a special design element in that the parameters パラ, ρ and および cannot be freely selected.

In general, the Poisson's ratio has a relatively small variation in value depending on the material, so assuming that it can be regarded as a constant, the sensitivity (index) S decreases with the reciprocal of the Young's modulus Ε, and the natural frequency ω is the square root of ΕΖρ It increases. Therefore, it is important to select substances with large ΕΖ / Ο.

The parameter with poor efficiency is the thickness. If the thickness is doubled, the natural frequency will be doubled and the index of flexibility will be 1/8 times smaller.

In summary, if you optimize in the order of radius, material, and thickness, you will be able to maintain high flexibility and maintain high natural frequency.

Based on these results, the case of actual design is described. The radius determines the lens diameter, so the lower limit is determined by the requirements of the optical system. Therefore, it is difficult to discuss unless the actual application is determined. Materials are also subject to various restrictions due to the requirements of the optical system, but here we assume that there are no restrictions and will consider them. From the previous explanation, it is known that the larger the EZ (p (1-V ² )) and the smaller the Young's modulus E, the higher the natural frequency. The natural vibration number of coefficients EZ Cp (1-Seo ²⁾⁾ on the horizontal axis, a plot of various substances flexibility coefficient 1ZE the ordinate, shown in Fig. However, the numerical values were plotted by multiplying by a constant. As shown in Fig. 4, when the material distributed on the right or top in the graph constitutes the lens surface, it is easy to increase the natural frequency and it is flexible. It is believed that there is. In FIG. 4, "Gr ass # 1 (see sign 401)", "G rass # 2 (see sign 402)", "Gr ass # 3 (see sign 403)", "Gr ass # 4 (see sign 404)" ”,“ Gr ass # 5 (see 405) ”and“ Gras s # 6 (see 406) ”are: Alkaline zinc borosilicate, lead-based liquid, aluminosilicate, borosilicate, high Shows lead and quartz glass. They have almost the same coefficient of flexibility. Of these, borosilicate (404), zinc borosilicate (401), quartz glass (406) and aluminosilicate (403) have relatively high natural frequency coefficients.

Glass has a high natural frequency and relatively large flexibility, and the high molecular compound polyethylene / polystyrene has great flexibility, but its natural frequency is low. These materials are likely candidates for lens surface materials. The selection of these materials is desirably determined in consideration of the width (range) of displacement of the lens surface portion 12 and the required response speed.

The thickness should be as thick as possible within the range discussed here. However, as the thickness increases, the flexibility decreases, so the thickness should be as large as possible within the range of pressure that can be generated in the actuator. The laminated piezo actuator used in the proposed varifocal lens can generate a very large force (10 to 1000 [N]), so the degree of freedom is large.

[Principle of the present invention. Cylinder section (pressure transmission section)]

Since the cylinder has the same structure as the lens surface, basically the same considerations apply as for the lens surface. Since this part also needs to oscillate at 1 kHz, it is necessary to design a high natural frequency. The radius of the cylinder is determined by the movable range of the actuator and the amplification factor required to sufficiently deform the lens surface. The thickness and material can be basically considered in the same way as the lens surface.

However, since it does not need to function as a lens, it can be made stiffer and lighter by providing protrusions and complicated structures in its shape, and various structures can be adopted. For example, with a honeycomb structure used for aircraft, etc., it is possible to create a pressure transmitting section with a high natural frequency and large elasticity.

If it is necessary to greatly amplify the displacement of the actuator and transmit it to the lens surface, the pressure transmitting section (cylinder section) must have a large radius, so the material and thickness must be increased accordingly. Come out. In this case, it is more important to design a rigid and light structure.

[Principle of the present invention: pressure transmission oil]

The mechanism that transmits the pressure generated by the actuator to the lens surface needs to have a high-speed response to transmit the pressure that changes in the order of kHz and accurately measure the distortion of the lens surface. If the distortion of the lens surface cannot be known, the optical characteristics such as the focal length cannot be known, so that the lens cannot be used as a varifocal lens.

The proposed lens uses a mechanism that distorts the lens surface by applying pressure to the high refractive index oil that fills the inside of the lens. The fact that this structure has a high-speed response and can accurately measure the distortion of the lens surface will be described below.

In general, liquid has a low compressibility, and is suitable as a medium for efficiently transmitting pressure as represented by a hydraulic mechanism. In particular, oil is stable to temperature and easy to handle, and has a low compression ratio, so it is suitable for pressure transmission. The pressure required to distort the varifocal lens is estimated to be around 30 [NZm ² ], at which oil compression is negligible. Therefore, it can be assumed that the volume extruded due to the deformation of the cylinder due to the displacement of the actuator is equal to the volume expanded by distorting the lens. Actuate — Since the displacement in the evening can be measured accurately, the degree of lens distortion can also be estimated from the displacement in the actuate, and the optical characteristics of the lens can be known. > Configuration and operation]

FIG. 5 is a block diagram schematically showing the varifocal lens and its control device according to the present embodiment. As shown in FIG. 5, a control computer 20, an amplifier 22 that receives a drive voltage output from the control computer, amplifies the drive voltage, and supplies the amplified voltage to a piezoelectric actuator 14, and a varifocal lens 10. It has. Note that the prototype has a sensor head 24 and a sensor control unit 26 for detecting the displacement of the lens surface portion 12. The displacement signal of the lens surface is returned from the sensor controller 26 to the control console 20. The displacement of the piezoelectric actuator 14 is returned from the amplifier 22 to the control computer 20. In FIG. 5, the signal line indicated by the broken line and the components surrounded by the broken line are used to obtain a complete set of test results. Therefore, these components can be omitted when actually used as a lens.

In the system configured as described above, in the control computer 20, data for causing a predetermined displacement at a predetermined frequency is D / A-converted and provided to the amplifier as an analog signal. The amplifier 22 amplifies the applied analog signal to a level sufficient to drive the piezo-electric device. As a result, the piezoelectric element 14 is displaced, and this is applied to the pressure transmitting part 15 of the lens 10. This displacement is transmitted to the lens surface portion 12 via the liquid filled in the lens container 11, thereby displacing the lens surface portion 12 in a convex or concave shape, and changing the focal point of the lens. .

[Example]

The following describes the prototype of the variable focus lens used in the system shown in Fig. 5. As shown in FIGS. 6A and 6B, in the prototype 100 of the variable focus lens according to the present embodiment, a double glass tube having a height of 50 mm, an inner diameter of 27 mm, and an outer diameter of 35 mm was used. Thus, oil was filled between the glass tube forming the inner diameter and the glass tube forming the outer diameter, and this was designated as a container 111. In the glass tube 120 constituting the outer diameter of the housing 1 1 1, two opposite holes (7.5 mm diameter) are formed almost at the center side surface, and there is a thickness of 20 / m Place the glass thin film and this The lens surface portion 1 1 2 was used to transform. Further, a glass plate 122 having a thickness of l mm and a hole having a diameter of 5 mm was disposed thereon, thereby fixing the lens surface portion 112 (see FIG. 6B). By feeding back the overnight displacement (see reference numeral 501 in FIG. 5) and the displacement of the lens surface portion (see reference numeral 502), distortion on the lens surface is detected, and more appropriate control based on this is detected. It is also possible.

For example, the lens surface distortion can be indirectly measured and fed back by estimating it using the displacement of the actuator 14 and the direct measurement of the lens surface is also possible. Can be realized. If the pressure of the liquid inside is negligible and the natural frequencies of the lens surface and cylinder are sufficiently high, there is a one-to-one correspondence between the input of the actuary and the distortion of the lens surface. A relationship can be assumed. Therefore, the lens distortion can be estimated only by measuring the displacement of the actuator 14. In other words, in the system shown in Fig. 5, it is also possible to estimate the distortion of the lens surface from the displacement of the actuator 14 and feed it back.

At the lower part of the container 111, for example, a pressure transmitting element 115 made of SUS304 is placed, and the piezo-actuator closely attached to its lower part (shown in FIGS. 6A and 6B). ) Is transmitted. As shown in FIG. 3, the pressure transmitting section 1 15 has a central portion so that the resonance frequency becomes high and the liquid in the container 1 1 1 can be pushed out efficiently with respect to the displacement of the actuator. The design is reinforced. In addition, a container cover having a thickness of 5 mm is arranged on the upper part of the container 111 to seal the liquid stored between the two glass tubes.

The prototype was designed with the primary resonance frequency of about 8.0 kHz. When the primary resonance frequency of the designed structure is estimated by the finite element method, the lens surface is 8. 2 kHz, the cylinder section was 7.7 kHz.

[Lens response]

In order to confirm that the prototype varifocal lens has a response performance on the order of kHz, the displacement (see reference numeral 501) of the piezoelectric actuator shown in Fig. 5 was input. The frequency response was measured using the displacement at the center of the lens surface portion 12 (see reference numeral 502) as the output.

In order to measure the displacement of the center of the lens surface, a laser rangefinder LC-240 (Keyence, response frequency 20 kHz) was used as the sensor head 24 and the controller 26. It was measured. As Piezochiyue 14, we used P-84.1.10 (manufactured by PI-Polytec, primary resonance frequency 18 kHz, movable range 15 μm, built-in strain sensor). In the control computer 20, the control cycle is 0. The measurement was performed at 1 ms.

Figure 7 is a Bode plot of the measured frequency response. From Fig. 7, it was found that the response characteristics hardly changed up to 1 kHz, confirming that the structure of the prototype varifocal lens can respond in the order of kHz.

[Application example]

Next, another configuration example of the variable focus lens according to the present invention will be described. In the first embodiment, the container is filled with a single liquid, but by dividing the container into a plurality of parts, a plurality of liquids having different refractive indices can be divided into parts of the container. It is also possible to fill each one.

If the focal length of the lens is changed, the optical parameters will change accordingly, and the conditions for aberration correction will change. Conventionally, in such a case, the movement of multiple parameters was absorbed by moving multiple lenses.However, by moving the lens at a speed reaching the order of 1 kHz, It is difficult to absorb change. Therefore, in the present invention, in order to solve this problem, a structure in which the variable focus mechanism is multi-layered was invented. Multilayering increases the degree of freedom of optical parameters by the number of layers.

8A to 8D are cross-sectional views each showing an example of a multi-layer variable focus lens. For example, in the varifocal lens shown in FIG. 8A, the container 211 is divided into a first part 222 and a second part 222, and the first part 222 and the second part 222 are divided into two parts. At the end of each of them, piezoakchiyue 2 14 and 2 15 are arranged. Also, the first part 222 and the second part 222 are rigid, for example, 223 In addition, on the outer surfaces of the first portion 2 2 1 and the second portion 2 2 2, flexible or elastic surface portions 2 1 2 and 2 13 are formed.o

With such a configuration, the surface portion 2 12 is displaced by driving the piezoelectric element 2 14, while the surface portion 2 13 is displaced by driving the piezoelectric element 2 15 be able to. As a result, the degree of freedom becomes “2”, and two optical parameters, for example, the focal length and the spherical aberration can be adjusted.

In the varifocal lens shown in FIG. 8B, a connecting portion (connecting surface) 3 13 having flexibility or elasticity is also formed between the first portion 3 21 and the second portion 3 22. On the other hand, the surface portion 316 disposed on the outer surface of the second portion 322 has rigidity. Also in this example, two optical parameters can be adjusted. Note that the optical parameters include coma as well as focal length and spherical aberration.

Further, as shown in FIG. 8C, the container 4 11 is divided into a first portion 4 2 1, a second portion 4 2.2 and a third portion 4 2 3, and the first portion 4 2 Surface portion 4 1 2 provided on the outer surface of 1, connection portion 4 2 4 between first portion 4 2 1 and third portion 4 2 3, and provided on the outer surface of second portion 4 2 2 The given surface portion 4 13 has flexibility or elasticity, and can be displaced by driving the corresponding actuator. In addition, the connecting portion 4 25 between the second portion and the third portion has rigidity. In this example, the degree of freedom can be set to “3”. In this case, it becomes possible to adjust three optical parameters, for example, the focal length, spherical aberration, and coma. FIG. 8D shows still another example of the varifocal lens having a degree of freedom of “3”. Here, the outer surface of the second part 5 2 2 is rigid (see reference numeral 5 16), while the connection between the second part 5 2 2 and the third part 5 3 3 (reference number 5 13) has flexibility or elasticity. The outer surface portion 5 1 2 s of the first portion 5 2 1 and the connecting portion 5 2 4 between the first portion 5 2 1 and the third portion 5 2 3 have flexibility or elasticity. This is similar to the example in FIG. 8C.

In addition, each part of the container is filled with a liquid having a different refractive index. Is also good. As a result, the degree of freedom of the optical parameters can be increased, and the color difference can be adjusted. FIGS. 9A and 9B show such examples. The structure of the variable focus lens shown in FIG. 9A is the same as that of FIG. 8B. The first portion 3 2 1 of the variable focus lens 3 1 1 is filled with a liquid having a refractive index (≠ refractive index η of air), and the second portion 4 3 3 has a refractive index n ₂ (≠ ni and ≠ η.) Liquid is filled.

The structure of the variable focus lens shown in FIG. 9D is the same as that of FIG. 8D. Again, the first part 5 2 1 contains a liquid with a refractive index ii i (≠ n.), The second part a liquid with a refractive index n ₂ and ≠ n ₀ ), and a third part Liquids with a refractive index of n ₃ (≠ n ₁₅ ≠ n ₂ and ≠ n.) Are each filled.

In this way, by making the varifocal lens multi-layered and filling each layer with a liquid having a different refractive index, it is possible to achieve high imaging accuracy while maintaining a high response speed. .

[Application of the above embodiment and application example]

Next, an example in which the varifocal lens according to the above-described embodiment or application example is applied to a microscope will be described. FIG. 11 is a diagram schematically showing an example of a microscope using a variable focus lens. In this example, a varifocal lens 111 is disposed between the objective lens 110 and the imaging device 110. This varifocal lens may have a configuration as shown in FIGS. 1 and 2 or a configuration as shown in FIGS. 8A to 8D or FIGS. 9A and 9B. This microscope includes an image forming unit 1104 and a lens control unit 1106 connected to the image pickup device 1102. The image forming unit 111 and the lens control unit 110 constitute an arithmetic unit 111. The image forming unit 1104 receives a signal from the image sensor 111 and creates image data captured by a microscope. Further, the lens control unit 1106 extracts a component having a relatively high spatial frequency in the signal, for example, including a Laplacian filter, and determines whether or not the lens is in focus.

A control voltage for controlling the function (not shown) of the varifocal lens 110 is output from the lens controller 1106. Also, from the varifocal lens 1 1 1 0 A signal indicating the displacement may be returned to the lens control unit 1106. In the microscope configured as described above, when the focal plane 1 1 1 2 changes in the optical axis direction of the microscope due to the movement of the object (see the dashed-dotted line and the dashed-dotted line), the lens control unit 1 10 6 determines that the focus is out of focus, and controls the actuator to move the focal plane back and forth in the optical axis direction. The lens control unit 1106 determines the in-focus position based on the image taken by the imaging device 1102 during the forward and backward movement. In this embodiment, since the control of the focal length can be realized at a rate of 1 kHz, the movement of the focal plane can be made sufficiently faster than the movement of the object. It is possible to perform appropriate focusing.

[Other embodiments]

Next, another embodiment of the variable focus lens according to the present invention will be described. As shown in FIGS. 12 and 13, in the varifocal lens 12 10 according to this embodiment, the configuration of the container 11, the actuator 14, the membrane 15, and the like are shown in FIGS. It is almost the same as shown in Fig. 3. Further, the inside of the container 11 is filled with a liquid for transmitting the displacement of the actuator, for example, emulsion oil.

On the side of the varifocal lens 1 210 where the actuator 14 is not arranged, two substantially parallel surfaces are formed, and on each surface, a plurality of circular openings are formed so as to face each other. At the opening, a lens surface portion 12 made of a thin and transparent plate that is elastically deformable is arranged. The plurality of lens surface portions 12 are arranged according to a certain geometric arrangement. For example, as shown in FIG. 13, the arrangement may be such that every other row and column are arranged, or the arrangement may be such that adjacent rows and columns are arranged. It is desirable that the refractive index of the lens surface portion 12 and the refractive index of the liquid filled in the container 11 be the same.

The diameter of the lens surface portion 12 is very small (for example, several tens of m to several hundreds / m), and the varifocal lens 1210 has the opposite lens surface portion 12 functioning as a micro lens. It functions as a micro variable focus lens array. In this example, each lens surface portion 12 is in contact with the same liquid, and the same pressure is applied by driving the actuator 14. Therefore, the focal length is uniformly controlled It is. Of course, the lens surface portion 12 may be formed only on one surface of the container. FIGS. 14A and 14B are diagrams showing an application example of such a micro variable-focus lens array. In the example of Fig. 14A, the lens surface part 1 2 (single lens surface part or a set of opposing lens surface parts) of the micro variable-focus lens array and the image sensor 1401 correspond one-to-one. are doing. On the other hand, in the example of FIG. 14B, a plurality of (9) lens surface portions (or 9 sets of lens surface portions) 1 4 2 0—1 and 1 4 2 0—2 and an imaging device 1 4 1 1—1, 1 4 1 1 1 and 2 correspond. In addition, a rigid transparent partition is placed in the container of the micro variable-focus lens array so that another liquid (the refractive index may be the same or different) may be in contact with that of the facing lens surface. You may. This arrangement corresponds to the structure shown in FIG. 8A when focusing only on the opposing lens surface. Further, as shown in FIG. 8B, in the partition, one surface of the container and a lens surface portion facing the partition may be formed. Further, a three-layer structure as shown in FIG. 8C or FIG. 8D may be adopted.

Fig. 15 shows an example in which an astigmatic lens is used. In this example, the lens surface portion 1512 is rectangular. Even when the lens shape is an asymmetry, as in the examples shown in FIGS. 12 and 13, the length of each side is very small (for example, several tens of meters to several hundreds of meters). A micro variable focus lens array may be formed in which the lens surface portions of the above are arranged according to a certain geometrical arrangement. Further, in such a micro variable focal length lens, a transparent partition may be arranged so that another liquid comes into contact with each of the opposing lens surface portions (see FIGS. 8A to 8D). Also in this example, the lens surface portion 1512 may be formed only on one surface of the container, or the lens surface portion may be formed so as to face both surfaces.

FIG. 16 is a diagram showing an example of a microvariable focus lens array in which lens surface portions each having an elongated rectangular shape are arranged in one direction. The lens surface portion 1612 is adjacently arranged via a rigid boundary portion 1613. In each lens surface part 12, the center in the longitudinal direction (reference numeral 1610) is The shape of the step surface at each position becomes the same even when the pressure inside the container changes. Therefore, the center 1610 can be used as a lens. Also in this example, the lens surface portion 1612 may be formed only on one surface of the container 1611, or the lens surface portion 1612 may be formed on both surfaces so as to face each other. May be. The micro-variable-focus lens array shown in Fig. 16 can be used, for example, by placing it on the front side of an LCD (Liquid Crystal Display) and changing the lens focus to enable the display of so-called three-dimensional images. O

Further, in this micro variable focus lens array, a multilayer structure as shown in FIGS. 8A to 8D may be adopted for each of the opposing lens surface portions. In addition, each layer may be filled with the same liquid, or may be filled with liquids having different refractive indexes.

The present invention is not limited to the above embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say,

For example, in the present embodiment, regarding the structure of the varifocal lens, a pressure transmitting portion is disposed on one of the funnel-shaped expanded sides, and a flexible or elastic surface portion is arranged so as to face the thinly extended side. By arranging and driving a pressure transmitter having an area that is sufficiently large compared to the surface area, it is possible to amplify the small movements of the piezo actuator to a sufficient displacement of the surface area.

However, the shape is not limited to the above-mentioned shape or the shape of the prototype. In the present invention, as shown in FIG. 10, the area S of the side on which the actuator 14 is mounted (the pressure transmitting section 15) is the area of the flexible or elastic surface portion functioning as a lens. Sufficiently larger than the area s (S>> s), and the pressure transmission part and the surface part are connected by a liquid such as oil, and the vibration of the pressure transmission part 15 is transmitted to the surface part 12. Any structure is acceptable. By adopting such a structure, the displacement of the surface portion can be SZs times the displacement of the pressure transmitting portion. By adjusting the ratio of the area S of the pressure transmitting section to the area s of the surface portion, the displacement of the surface portion can be adjusted to a desired range. Further, in the above-described embodiment, the cross-shaped projection is formed on the side of the pressure transmitting portion that comes into contact with the actuator, but the shape of the projection is not limited to this. Triangular shape arranged at an angular interval of Further, in the above-described embodiment, an example in which the container has a two-layer structure or a three-layer structure has been described, but it goes without saying that a four-layer or more layer structure may be employed. Also in this case, it is sufficient to adopt a configuration in which a pressure transmitting unit is arranged in each layer and the displacement of the actuator can be transmitted to the connecting unit and the lens surface.

Further, the degree of freedom is sacrificed. However, in the multilayer structure, the surface portions and connection surfaces of some layers may be configured to be displaceable without arranging the actuators in all layers. In addition, in the example of the microlens array, instead of or in addition to arranging a transparent partition in parallel with the surface of the container, a partition almost perpendicular to the surface of the container is arranged, and It may be filled with a different liquid.

According to the present invention, it is possible to provide a variable focus lens that responds at a frame rate of a high-speed vision system, and a control device therefor.

Industrial applications

The present invention is particularly desirable to cooperate with a lens having a high-speed response of 1 kHz or more, and can be applied to a high-speed vision system using a vision chip. This high-speed vision system can follow an image of an object moving at high speed in a focused state, generate an image of the object, or capture other objects moving at high speed. It is also possible to control devices (arms).

Further, in the present invention, a micro variable focal length lens array in which minute lenses are arranged in a geometrical arrangement is constituted, and a plurality of images are formed by associating a single micro lens or a predetermined number of micro lenses with an image sensor. By generating them and generating new images based on them, it becomes possible to acquire more precise images. In addition, a three-dimensional image can be generated by combining with LCD or the like.

Claims

The scope of the claims

1. A container filled with liquid,

A pressure transmitting portion that contacts the actuator and transmits the vibration of the actuator, and a container having two light transmitting portions on a light incident surface and a light emitting surface, and the incident surface and the light emitting portion. At least one of the surfaces is at least one surface portion that can be displaced unevenly in the optical axis direction in response to a displacement given from the pressure transmitting portion via the liquid, and has an area s and the pressure By providing a surface portion such that the ratio (s / S) to the area S of the transmission portion is equal to or less than a predetermined value, the focal portion is formed by the displacement of the surface portion in response to the displacement of the actuator. A varifocal lens characterized by changing the distance.

2. In the container, the diameter is expanded toward one end, a pressure transmitting portion is arranged at the expanded end, and the other end has a single diameter near the end, and is opposed to each other. The varifocal lens according to claim 1, wherein an incident surface and an exit surface are formed.

3. The varifocal lens according to claim 1, wherein a projection is formed on a surface of the pressure transmitting portion that comes into contact with the actuator.

4. The variable focus lens according to claim 3, wherein the projection has a cross shape.

5. The first part including the first pressure transmitting portion and the incident surface, wherein the container contacts the first actuator, and the second pressure transmitting, which contacts the second actuator. A second portion including a portion and the exit surface; and a connecting surface in which the first portion and the second portion are in close contact with each other at least at a position facing the entrance surface and the exit surface,

Displaceable by any combination of the incident surface and the coupling surface of the first portion, the incident surface of the first portion and the exit surface of the second portion, and the coupling surface and the exit surface of the second portion. The variable focus lens according to any one of claims 1 to 4, wherein a variable surface portion is formed.

6. The varifocal lens according to claim 5, wherein the connection surface and the emission surface are respectively formed of materials having different refractive indexes.

7. 7. The varifocal lens according to claim 5, wherein the connection surface and the liquid are formed of materials having different refractive indices, respectively.

8. 8. The variable focus lens according to claim 5, wherein the first portion and the second portion are filled with liquids having different refractive indexes.

9. A first portion including the first pressure transmitting portion and the incident surface, wherein the container is in contact with the first actuator, an n-th pressure transmitting portion in contact with the n-th actuator, and (N−2) intermediate portions interposed between the n-th portion including the emission surface and the first portion and the n-th portion, the i-th (i = 2, 3, '' ', (N-2))) and an intermediate portion including an i-th pressure transmitting portion in contact with the actuator.

In the adjacent intermediate portion, a connecting surface is formed in close contact with a portion facing the incident surface and the emitting surface, and in each of the portions, the incident surface, the connecting surface, and the Z or the emitting surface are displaceable. The varifocal lens according to any one of claims 1 to 4, wherein a surface portion is formed.

Ten. The varifocal lens according to claim 9, wherein the connection surface and the emission surface are formed of materials having different refractive indexes, respectively.

11. The varifocal lens according to claim 9 or 10, wherein the connection surface and the liquid are formed of materials having different refractive indexes, respectively.

12. 12. The method according to claim 9, wherein the first part, the (η-2) intermediate parts and the η-th part are filled with liquids having different refractive indexes. A varifocal lens according to Item.

13. The varifocal lens according to any one of claims 1 to 12, wherein a plurality of surface portions are arranged in a predetermined geometrical arrangement on the incident surface and at least one thereof. .

14. The surface portions each have a diameter of several tens of m to several hundreds // m, and are formed on one of the entrance surface and the exit surface, or on opposite pairs formed on both surfaces. 2. A microlens is formed by a surface portion of the microlens. 3. The variable focus lens according to 3.

15. The surface portion is a longitudinally elongated rectangle having a width of several tens to several hundreds of meters, and is formed on one or both of the entrance surface and the exit surface. 14. The varifocal lens according to claim 13, wherein a micro lens is formed by the surface portions of the pair facing each other.

16. The varifocal lens according to claim 15, wherein the surface portions are arranged such that sides in a longitudinal direction thereof are substantially in contact with each other.

17. The varifocal lens according to any one of claims 1 to 16, a control unit that supplies a signal for driving each actuator, and an amplifier that amplifies each of the signals. Characteristic lens control device.

18. The lens control device according to claim 17, wherein the control unit receives the displacement of the actuator as feedback.

19. The method according to claim 17, further comprising a lens displacement measuring unit for measuring a displacement of the surface portion, wherein the displacement of the surface portion is fed back to the control unit. Lens control device.