JP2023180205A - Liquid crystal lens device and wide-angle fovea lens device - Google Patents

Abstract

To provide a liquid crystal lens device that can generate a lens effect at an arbitrary position while suppressing reduction in optical performance, and a wide-angle fovea lens device using the same.SOLUTION: A liquid crystal lens device 10 has a liquid crystal cell 11, an ultrasonic unit 12 having a plurality of ultrasonic generation elements 18, a driving circuit 14, and a control section 15 controlling the ultrasonic unit 12 through the driving circuit 14. The liquid crystal lens device overlaps ultrasonic waves from the plurality of ultrasonic generation elements 18 to form one or more lens areas to be a convex lens or a concave lens at an arbitrary position of the liquid crystal cell 11.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid crystal lens device and a wide-angle foveal lens device.

An optical system called a wide-angle foveal lens is known, which is modeled after the human eye and has a wide field of view and high resolution in the center, which is the region of interest (for example, see Patent Document 1). Furthermore, a liquid crystal lens is known in which a liquid crystal layer is provided between a pair of substrates and a voltage is applied to the liquid crystal layer from electrodes provided on the pair of substrates (see Patent Document 2). In this liquid crystal lens, by controlling the orientation of liquid crystal molecules using a voltage, one or more parts of a subject image at an arbitrary position can be enlarged or reduced.

Further, Patent Document 3 discloses a liquid crystal lens that changes the focal length of the liquid crystal lens by causing the liquid crystal lens to resonate with the vibration of an ultrasonic wave generating element and changing the thickness of the liquid crystal layer according to the vibration intensity of the ultrasonic wave. It is being In the liquid crystal lens described in Patent Document 3, a ring-shaped ultrasonic wave generating element that generates an ultrasonic wave with a frequency that matches the resonance frequency of the liquid crystal lens is placed around a liquid crystal layer, and one of the elements sandwiching the liquid crystal layer. It is installed on the board.

Furthermore, a plurality of ultrasonic generating elements are provided on a substrate on which a rectangular liquid crystal cell is provided, and by making the liquid crystal cell resonate with these ultrasonic generating elements, a lattice-shaped flexural vibration is generated, and the alignment of liquid crystal molecules is achieved. A liquid crystal molecule orientation control method for two-dimensionally and periodically changing is known (for example, Patent Document 4).

JP2020-56849A International Publication No. 2012/153837 Japanese Patent Application Publication No. 2018-92069 JP 2018-31818 Publication

By the way, with a wide-angle foveal lens using a liquid crystal lens as described in Patent Document 2, it is possible to move a region of interest with high magnification within an image circle and to change the magnification while eliminating the need for a mechanical mechanism. It can be changed. However, the wiring for applying voltage to the electrodes causes anisotropy in the lens effect, which causes a decrease in the optical performance of the lens. Further, in the liquid crystal lens described in Patent Document 3, since resonance of the liquid crystal lens is utilized, a lens effect cannot be generated at an arbitrary position.

The present invention has been made in view of the above circumstances, and provides a liquid crystal lens device that can generate a lens effect at any position while suppressing deterioration of optical performance, and a wide-angle foveal lens device using the same. The purpose is to

The liquid crystal lens device of the present invention is a liquid crystal cell having a pair of transparent substrates arranged to face each other and having an alignment film formed on the facing surfaces, and a liquid crystal layer made of liquid crystal provided between the pair of transparent substrates. an ultrasonic unit having a plurality of ultrasonic generation elements provided on the peripheral surface of the liquid crystal cell, the ultrasonic generation elements applying ultrasonic waves from the periphery of the liquid crystal cell to the liquid crystal layer; and the liquid crystal layer. based on the position of the lens area so that a standing wave having an antinode or a node at the center position of the lens area, which is one or more lenses, is formed by superimposing each ultrasonic wave from the ultrasonic generating element. The apparatus further includes a control section that controls the phase and output timing of the ultrasonic waves from the plurality of ultrasonic wave generating elements.

The wide-angle foveal lens device of the present invention includes a pair of transparent substrates that are arranged to face each other and have an alignment film formed on their facing surfaces, and a first liquid crystal layer made of liquid crystal that is provided between the pair of transparent substrates. a second liquid crystal cell having a first liquid crystal cell and a second liquid crystal layer; An ultrasonic wave generator having a first ultrasonic generating element and a plurality of second ultrasonic generating elements provided on the peripheral surface of the second liquid crystal cell and applying ultrasonic waves from the peripheral edge of the second liquid crystal cell to the second liquid crystal layer. a sonic wave unit; and a second lens region in which one of the first liquid crystal layer or the second liquid crystal layer has a convex lens and a standing wave having an antinode at the center position of the lens region, and the other liquid crystal layer has a concave lens. Based on the position of the lens area in the first liquid crystal layer, the ultrasonic waves from the plurality of first ultrasonic generating elements are formed so that a standing wave having a node at the center position of the ultrasonic wave is formed by superimposing a plurality of ultrasonic waves. and a control unit that controls the phase and output timing of the ultrasound waves and also controls the phase and output timing of the ultrasound waves from the plurality of second ultrasound generation elements based on the position of the lens region in the second liquid crystal layer. It is something.

According to the present invention, ultrasonic waves input into the liquid crystal layer from a plurality of ultrasonic generating elements provided around the liquid crystal cell are superimposed to form a lens region that becomes a lens, so that optical performance can be suppressed while suppressing deterioration of optical performance. A lens effect can be generated at the position of

FIG. 1 is a block diagram showing the configuration of a liquid crystal lens device according to an embodiment. FIG. 2 is a perspective view showing a liquid crystal cell and an ultrasonic wave generating element. FIG. 2 is an explanatory diagram schematically showing the orientation of liquid crystal molecules in a liquid crystal cell. FIG. 2 is a plan view showing an example of a disk-shaped liquid crystal cell. FIG. 3 is an explanatory diagram showing a state in which a lens region that becomes a convex lens is formed by a standing wave of an ultrasonic wave. FIG. 3 is an explanatory diagram showing a state in which a lens region that becomes a concave lens is formed by a standing wave of an ultrasonic wave. FIG. 6 is an explanatory diagram showing a state in which the initial phases are controlled so that the peaks of each ultrasonic wave overlap at a predetermined center position. FIG. 6 is an explanatory diagram showing a state in which the output timing of each ultrasonic wave is controlled so as to form a lens region that becomes a convex lens around a center position P. FIG. FIG. 6 is an explanatory diagram showing a state in which the output timing of each ultrasonic wave is controlled so as to form a lens region that becomes a concave lens around a center position P. FIG. FIG. 3 is an explanatory diagram showing each ultrasonic wave input into a liquid crystal layer when forming a lens region that becomes a convex lens in a square liquid crystal cell. FIG. 2 is an explanatory diagram showing each ultrasonic wave input into a liquid crystal layer when forming a lens region that becomes two convex lenses centered on center positions P ₁ and P ₂ in a disk-shaped liquid crystal cell. FIG. 2 is an explanatory diagram showing the configuration of a wide-angle foveal lens device using a liquid crystal cell.

In FIG. 1, the liquid crystal lens device 10 is broadly divided into a lens unit U1 and a control unit U2. The lens unit U1 includes a liquid crystal cell 11 serving as a lens and an ultrasonic unit 12. Further, the control unit U2 includes a drive circuit 14 that drives the ultrasound unit 12 and a control section 15 that controls the ultrasound unit 12 via the drive circuit 14. The ultrasonic unit 12 is provided with a plurality of ultrasonic generating elements (hereinafter simply referred to as "generating elements") 18 that generate and output ultrasonic waves. Each generating element 18 is attached to the liquid crystal cell 11. This liquid crystal lens device 10 forms one or more lens regions serving as convex lenses or concave lenses at arbitrary positions of the liquid crystal cell 11 using ultrasonic waves from a plurality of generating elements 18 .

In FIG. 2, the liquid crystal cell 11 of the lens unit U1 includes a pair of substrates 21 and 22, and a liquid crystal layer 23 formed between these substrates 21 and 22. The substrates 21 and 22 are plate-shaped and made of an optically transparent material. In this example, the substrates 21 and 22 are square glass plates with each side having a length Ds. Therefore, the liquid crystal cell 11 has a square shape when viewed from above. One of the outer surfaces of the substrates 21 and 22 (the surface opposite to the liquid crystal layer 23) becomes a light incident surface, and the other becomes a light exit surface.

The substrates 21 and 22 are arranged in parallel with each other with one surface facing each other with a predetermined interval, and their peripheral edges are sealed with a sealing material 24. The liquid crystal layer 23 is formed by filling a space formed between the substrates 21 and 22 and the sealant 24 with liquid crystal. The liquid crystal layer 23 is made of nematic liquid crystal in this example. The distance between the substrate 21 and the substrate 22 is kept constant. Therefore, in this example, the liquid crystal layer 23 has a constant thickness and has a square plate shape with a cross section that is approximately the same size as the substrates 21 and 22.

An alignment film 25 is formed on the opposing inner surfaces of the substrates 21 and 22, respectively. As schematically shown in FIG. 3, the alignment film 25 vertically aligns the liquid crystal molecules 27 constituting the liquid crystal layer 23 at a pretilt angle of 90 degrees. As a result, the liquid crystal molecules 27 are vertically aligned at a pretilt angle of 90 degrees in the portions of the liquid crystal layer 23 where the pressure does not fluctuate due to the ultrasonic waves.

As shown in FIG. 2, four surfaces (hereinafter referred to as peripheral surfaces) 28 around the liquid crystal cell 11 that are perpendicular to the incident surface and the exit surface and surround the liquid crystal layer 23 include A plurality of generating elements 18 of the sound wave unit 12 are respectively provided. In this example, five generating elements 18 are provided on each of the four peripheral surfaces 28. In this example, five generating elements 18 are provided at a constant pitch on each of the circumferential surfaces 28, and by making the pitches of the generating elements 18 provided on each circumferential surface 28 equal, the lens unit U1 can be used as a liquid crystal cell. The shape and arrangement are rotationally symmetrical around the axis passing through the center of 11.

Note that the shape of the liquid crystal cell 11, the arrangement of the generating elements 18, the number of generating elements 18, etc. are not limited to those described above. For example, the shape of the liquid crystal cell 11 in plan view may be a triangle or a polygon such as a pentagon. Further, as in the lens unit U1 shown in FIG. 4, a plurality of generating elements 18 may be arranged at a predetermined pitch in the circumferential direction on the circumferential surface of a disk-shaped (circular in plan view) liquid crystal cell 11A. In the example of FIG. 4, 12 generating elements 18 are evenly arranged around the liquid crystal cell 11A at a constant pitch.

The generating element 18 is composed of, for example, a piezoelectric element, and outputs an ultrasonic wave based on a drive signal input from the drive circuit 14. The generating element 18 is attached to the peripheral surface 28 so as to apply the ultrasonic waves it outputs from the peripheral edge of the liquid crystal cell 11 to the liquid crystal layer 23 . In this example, one end (output end) of the generating element 18 is attached in close contact with the sealing material 24, and the ultrasonic waves from the generating element 18 are transmitted to the liquid crystal layer 23 via the sealing material 24. The ultrasonic waves transmitted to the liquid crystal layer 23 propagate through the liquid crystal layer 23 using the liquid crystal forming the liquid crystal layer 23 as a medium. Note that the method for attaching the generating element 18 is not limited to this, as long as the ultrasonic wave can be applied to the liquid crystal layer 23 from the periphery of the liquid crystal cell 11. For example, the generating element 18 may be attached so that one end thereof is exposed to the liquid crystal layer 23, or there may be a gap such as an air layer between the generating element 18 and the liquid crystal layer 23. Further, the output end of the generating element 18 may be attached in close contact with the end face of one or both of the substrates 21 and 22 that constitute the peripheral surface 28 of the liquid crystal cell 11 to transmit the ultrasonic waves to one or both of the substrates 21 and 22. Accordingly, ultrasonic waves may be propagated through one or both of the substrates 21 and 22 from the periphery of the liquid crystal cell 11, and the vibrations of the ultrasonic waves may be applied to the liquid crystal layer 23.

When forming a lens region, the control unit 15 selects a plurality of generating elements 18 from the ultrasonic unit 12 and drives the selected generating elements 18 via the drive circuit 14. The number of generating elements 18 to be selected may be two or more, and all the generating elements 18 of the ultrasonic unit 12 may be selected. From the perspective of isotropically forming the lens region, that is, making the lens effect by the lens region isotropic, it is important to make sure that ultrasonic waves propagate toward the lens region to be formed from different directions and from more directions. It is preferable to select a plurality of generating elements 18. When the generating elements 18 are provided on the circumferential surface 28 of the square liquid crystal cell 11 as in this example, it is preferable to select the generating elements 18 provided on the four circumferential surfaces 28, respectively. Furthermore, from the above point of view, when the liquid crystal cell is made into a polygonal shape and the generation elements 18 are provided on each peripheral surface, the degree of isotropy of the lens effect increases as the number of vertices of the polygon of the liquid crystal cell increases. Since the height increases, it is preferable to have many vertices, and it is particularly preferable to have a circular shape like the liquid crystal cell 11A.

When forming the lens region, the control unit 15 controls the initial phase and output timing of the ultrasonic wave from the selected generation element 18 depending on the center position of the lens region and whether the lens region is a convex lens or a concave lens. Control. Each generating element 18 outputs ultrasonic waves having the same frequency f.

In the liquid crystal layer 23, the liquid crystal molecules constituting the liquid crystal layer 23 are tilted due to the acoustic radiation pressure generated by the ultrasonic waves. The larger the fluctuation (amplitude) of the acoustic radiation pressure, the more the liquid crystal molecules tilt from the initial vertical direction toward the horizontal direction, and the tilt angle becomes larger. As a result, the optical path length of the light transmitted from the entrance surface to the exit surface of the liquid crystal cell 11 changes depending on the tilt angle of the liquid crystal molecules.

5 and 6 show a case where a standing wave Sw generated by an ultrasonic resonance phenomenon is formed in the liquid crystal layer 23. In the following, the waveforms of ultrasonic waves and their standing waves will be explained and illustrated as indicating changes in pressure (sound pressure) (changes in density) of the ultrasonic medium, that is, the liquid crystal of the liquid crystal layer 23, unless otherwise mentioned. do. For example, in an ultrasonic standing wave, an "antinode" is a position where pressure fluctuation is maximum (the amplitude of pressure is maximum), and a "node" is a position where pressure fluctuation is minimum or does not change. In addition, the peak (maximum) and bottom (minimum) of an ultrasound are the parts where the pressure (pressure of the medium) is maximum or minimum, and the center of vibration of an ultrasound is the center of the amplitude of the pressure. This is the part where the change is "0". Note that the variation in acoustic radiation pressure becomes maximum at the antinode position of the standing wave of the ultrasonic wave, and becomes minimum or zero at the node position.

As shown in FIG. 5, the angle of inclination of the liquid crystal molecules gradually decreases from the center of the antinode of the ultrasonic standing wave Sw toward both sides, forming a lens region having a lens effect. Ru. The lens effect is due to the fact that the larger the angle of inclination of liquid crystal molecules, the shorter the optical path length. The lens region in this case functions as a convex lens. Furthermore, as shown in Fig. 6, if we focus on the node positions of the ultrasonic standing waves Sw, a lens region is formed in which the tilt angle of the liquid crystal molecules gradually increases continuously from that position toward both sides. be done. The lens region in this case functions as a concave lens.

The control unit 15 generates each ultrasonic wave from the selected generating element 18 so that the antinode or node of the standing wave due to each ultrasonic wave from the selected generating element 18 is at the center position of the lens area in the liquid crystal layer 23. Determine the initial phase of. When the lens area is to function as a convex lens, the center position of the lens area should be at the antinode of the standing wave, and when it is to function as a concave lens, the center position of the lens area should be the node of the standing wave. .

In the example schematically shown in FIG. 7, the initial stage of each ultrasonic wave S1 and S2 input to the liquid crystal layer 23 from opposing positions is such that the antinode of the standing wave Sw is formed at the center position P, which is the lens area. This shows a state where the phase is controlled. By controlling the initial phase to further lag (or advance) by π so that one of the opposing generating elements 18 thus controlled has an opposite phase, the ultrasonic wave can be kept at the center position P. It can be controlled so that nodes of the wave Sw are formed.

FIG. 8 shows that the control unit 15 controls the initial phase of each ultrasonic wave as shown in FIG. A state in which the peaks are superimposed only at the center position P is shown. In such control, a mountain-shaped ultrasonic standing wave Swa having a peak at the center position P is generated. This standing wave Swa forms a lens region centered on the center position P that functions as a convex lens similar to the case shown in FIG. Even if the bottoms of the ultrasonic waves S1a and S2a from the generating element 18 are overlapped only at the center position P to generate a trough-shaped ultrasonic standing wave, a lens region that functions as a convex lens is similarly formed. In this way, the center position P of the lens area forms a standing wave in which the amplitude of the pressure (acoustic radiation pressure) gradually decreases outward from the antinode of the standing wave, that is, the center position P, so that the lens functions as a convex lens. A region is formed.

In FIG. 9, the control unit 15 controls the initial phase of each ultrasonic wave so that the node of the standing wave Swb is at the center position P, and also controls the output timing to generate each ultrasonic wave S1b from the generating element 18. , S2b are overlapped only at the center position P. In this type of control, the pressure fluctuation of the liquid crystal becomes "0" at the center position P, and the pressure gradually decreases in one direction from the center position P, and the pressure gradually increases in the other direction. Current wave Swb occurs. This standing wave Swb forms a lens region that functions as a concave lens similar to the case shown in FIG. In this way, the center position P of the lens area forms a node of a standing wave, that is, a standing wave in which the amplitude of pressure (acoustic radiation pressure) gradually increases in one direction around the center position P, which functions as a concave lens. A lens region is formed. In addition, in any case of FIG. 8, FIG. 9, the control part 15 is controlled to output the ultrasonic waves S1b and S2b of half wavelength.

Note that by controlling the amplitude and frequency (wavelength) of the ultrasonic waves output by the generating element 18, the height of the refractive index (length of focal length) and the size of the lens area can be controlled. For example, the greater the amplitude of the ultrasonic waves, that is, the sound pressure, the greater the absolute value of the refractive index of the lens region. Furthermore, the lens area can be made wider as the frequency of the ultrasonic wave is decreased, that is, the wavelength of the ultrasonic wave in the liquid crystal is increased. The refractive index of the lens region can also be adjusted by increasing or decreasing the amplitude of the standing wave generated by the selected generating element 18, ie by the number of superimposed ultrasound waves.

Next, in the liquid crystal lens device 10 configured as described above, a case where one lens region is formed at an arbitrary position of the liquid crystal cell 11 will be described. First, the case of forming a lens region that functions as a convex lens will be described. Note that although the case of the square liquid crystal cell 11 shown in FIG. 1 will be described as an example, the same applies to the case of the disk-shaped liquid crystal cell 11A.

In the following description, in order to simplify the explanation, it will be assumed that the generating element 18 transmits the ultrasonic wave directly to the liquid crystal layer 23. In addition, each position in the liquid crystal cell 11 and the liquid crystal layer 23 is expressed using XY coordinates whose XY plane is parallel to the surface of the liquid crystal cell 11 (substrate 21), and the center position of the lens area to be formed is P, and the center position P Let the coordinates of be (X _P , Y _P ). Further, the position on the circumferential surface 28 where each generating element 18 is attached, that is, the input position of the ultrasonic wave to the liquid crystal layer 23 is defined as Q _i (i is 1, 2, . . . ), and the coordinates of the input position Q _i are Let it be (X _i , Y _i ). Further, when the generating element 18 located at the input position Q _i is particularly distinguished, it will be described as the generating element 18 _i .

When forming a lens region that becomes a convex lens around the center position P, two or more generating elements 18 are selected from the ultrasonic unit 12, and the peaks of the ultrasonic waves from the selected generating elements 18 are aligned with each other or Each of the generating elements 18 is driven to output half a wavelength of ultrasonic waves so that the bottoms overlap each other at the center position P. When ultrasonic waves are output from each generating element 18, it is expected that a Fresnel lens-like lens effect with repeated concave and convex areas will occur in the lens area, but even at that time, due to the maximum acoustic radiation pressure, It is sufficient if the lens effect of forming a convex lens becomes dominant and the lens region can be regarded as a convex lens. Therefore, it is not necessary that the ultrasonic wave output from the generating element 18 be exactly half a wavelength. Note that the same applies to the case of forming a lens region that becomes a concave lens.

The ultrasonic wave (S _i ) at the input position Q _i is expressed by equation (1) using amplitude A _i , angular frequency ω (=2πf), and initial phase φ _i . The amplitude A _i may be the same or different for each generating element 18, but it may be caused by incremental interference when the peaks or bottoms of the ultrasonic waves from the selected generating elements 18 overlap at the center position P. The amplitude of the standing wave generated is adjusted so that it corresponds to the focal length of the convex lens to be formed.
S _i =A _i・sin(ωt+φ _i )...(1)

When the peaks overlap, the initial phase φ _i is set so that the peak of the ultrasonic wave from the generating element 18 _i overlaps the peak of the ultrasonic wave from each of the other selected generating elements 18 _i at the center position P. Set. When the bottoms overlap each other, the initial phase φ _i is set such that the bottom of the ultrasonic wave from the generating element 18 _i overlaps the bottom of the ultrasonic wave from each of the other selected generating elements 18 _i at the center position P. Set. The generating element 18 generates, for example, an ultrasonic wave having the same frequency and phase as the drive signal input thereto. Therefore, by adjusting the phase of the drive signal input to each selected generation element 18, the initial phase is adjusted such that the peaks or bottoms of the ultrasonic waves from each selected generation element 18 overlap each other at the center position P. Adjustment of φ _i is possible.

Specifically, in order to overlap the peaks or bottoms of each ultrasonic wave at the center position P, the distance from the input position Q _i of the generating element 18 _i to the center position P is set as L _i , and the ultrasonic wave is When the speed of moving the layer 23 is v (m/s) (the arrival time from the input position Q _i to the center position P is T _i =L _i /v), time t = T _i +n・T+t ₀ In each case, the initial stage of equation (1) is set so that the phase of the ultrasonic waves at the center position P is "π/2 + 2π・m" when the peaks are mutual, and "3π/2 + 2π・m" when the phases are between the bottoms. Adjust the phase φ _i . Here, the period T(s) is the generation period of a constant ultrasonic output pattern consisting of on and off waves emitted by the generating element _18i , and n and m are integers of 0 or more. Further, _t0 is an arbitrary time that serves as a reference when switching the output pattern of the ultrasonic wave with a period T for producing a lens effect at a desired position.

Furthermore, in order to simplify the explanation, the explanation here assumes that the ultrasonic wave moves only through the liquid crystal layer 23 at a speed v on the way from the generating element 18 _i to the center position P. In addition to the layer 23, if there is a gap due to an air layer or the like between the sealing material 24 or the generating element _18i and the liquid crystal layer 23 (and the sealing material 24), when passing through the sealing material 24 or the air layer, It is necessary to consider that the speed v of the ultrasonic wave changes depending on the medium through which it passes. In addition, when the ultrasonic waves are transmitted directly from the generating element 18 _i to the substrates 21 and 22 and the ultrasonic waves propagate using the substrates 21 and 22 as a medium, the velocity v is expressed as the velocity of the ultrasonic waves within the substrates 21 and 22. shall be.

The selected generating element _18i outputs an ultrasonic wave of half wavelength centered at the peak or bottom at a period T(s). At this time, ultrasonic waves are output during a period when time t is "n・T+T _i -ΔT+t ₀ ≦t≦n・T+T _i +ΔT+t ₀ ", and time t is "n・T+t ₀ ≦t≦n・T+T _i -ΔT+t ₀ ” and “n·T+T _i +ΔT+t ₀ ≦t≦(n+1)T+t ₀ ”, the selected generation element 18 _i is controlled so as not to output ultrasonic waves.

The above-mentioned time ΔT is defined as the time for outputting 1/2 of the length (half wavelength) of the ultrasonic wave from the generating element 18 as described above. That is, the time ΔT is the time during which the generating element 18 outputs an ultrasonic wave corresponding to 1/4 wavelength, and is the time required for the ultrasonic wave to travel within the liquid crystal layer 23 by 1/4 wavelength. As described above, the ultrasonic wave output from the generating element 18 does not have to be exactly half a wavelength, so the time ΔT does not have to be strict either. The time ΔT is obtained in advance from the ultrasonic frequency f. The period T is predetermined, for example, as the time required for the ultrasonic wave to travel the length (Ds) of one side of the liquid crystal cell 11 in the liquid crystal layer 23 (T=Ds/v).

As mentioned above, only during the period when time t is "n・T+T _i -ΔT+t ₀ ≦t≦n・T+T _i +ΔT+t ₀ ", the ultrasonic wave whose phase has been adjusted every period T is emitted from the selected generating element 18 _i . By outputting, a convex lens can be generated in a lens region at an arbitrary center position P.

By outputting ultrasonic waves from the selected generating elements 18 _i in the above manner, the peaks or bottoms of the ultrasonic waves from all the selected generating elements 18 overlap at the same time at the center position P, and the center position P A lens region that becomes a convex lens is formed. Each of the selected generating elements _18i repeatedly outputs ultrasonic waves with a period T, and the peaks or bottoms of the sound pressure of the repeating ultrasonic waves overlap each other with a short period T, so that a lens region is constantly formed. As a result, the lens region formed in this way can be used as a lens.

When the period T is determined as described above, the center position P can be set within a circle inscribed in a square of the liquid crystal cell 11 whose side length is Ds. Note that if the period T is the time required to travel the length of the diagonal line of the liquid crystal cell 11 through the liquid crystal layer 23 (T=2 ^1/2 ·Ds/v) or longer, then the center position P is the length of the liquid crystal cell 11. It can be set in the entire range of 11. In the case of a disk-shaped liquid crystal cell 11A, if the period T is the time required to move through the liquid crystal layer 23 by the length of the diameter of the liquid crystal cell 11A or longer, then the center position P is set at the center position P of the liquid crystal cell 11A. It can be set over the entire range.

In the above, a case has been described in which a convex lens effect is generated in the lens region at the center position P. However, at every time t=T _i +n·T, an ultrasonic wave from a part of the selected generation element 18 is generated at the center position P. By adjusting the initial phase φ _i in equation (1) so that the phase of the ultrasonic wave from the remaining part becomes "0+2π・m" and the phase of the ultrasonic wave from the remaining part becomes the opposite phase, that is, "π+2π・m", the center position can be determined. It is possible to generate a concave lens effect in the lens region of P. In this case, an ultrasonic wave with a half wavelength centered around the vibration center is output.

When generating a concave lens effect in a configuration in which the arrangement of the generating elements 18 is rotationally symmetrical, other generating elements 18 that are in a specific positional relationship (opposed relationship) with respect to one arbitrarily selected generating element 18 are also selected. , it is preferable to drive them so that they have the above phase relationship. The generating elements 18 in a specific positional relationship are the generating elements 18 arranged on the opposite side across the axis of rotational symmetry, and more specifically, one selected generating element (hereinafter referred to as the focused generating element). Among the generating elements 18 located at a position rotationally symmetrical to the generating element 18 of interest, this is the generating element 18 having the maximum distance from the generating element 18 of interest. For example, when n is set to 2, 3, etc., and the generating elements 18 are arranged on the peripheral surface 28 of a regular (2n) square or circular liquid crystal cell, a specific position for one generating element 18 of interest is set. One generating element 18 is selected as related. On the other hand, when the generating elements 18 are arranged on the circumferential surface 28 of a regular (2n-1) square liquid crystal cell 11, such as an equilateral triangle or a regular pentagon, a specific position is set for one generating element 18 of interest. Two generating elements 18 are selected as being related. In this way, when two generating elements 18 are selected as having a specific positional relationship, the amplitude of the ultrasonic waves from these two generating elements 18 is set to half the amplitude of the ultrasonic wave from the focused generating element 18. And it is sufficient.

FIG. 10 shows input positions Q 1 , Q 3 , Q ₄ when generating elements 18 _{1 ,} 18 ₃ , 18 ₄ , 18 ₁₁ , 18 ₁₃ , and 18 ₁₅ are selected to form a lens region at center _position P. , Q ₁₁ , Q ₁₃ , and Q ₁₅ , which schematically shows the ultrasonic waves input into the liquid crystal layer 23 . As shown in FIG. 10, from input positions Q ₁ , Q ₃ , Q ₄ , Q ₁₁ , Q ₁₃ , and Q ₁₅ , half-wavelength ultrasonic waves are input into the liquid crystal layer 23 repeatedly at a period T. . In this example, ultrasonic waves for half a wavelength centered on the peak are input.

Each of the ultrasonic waves inputted in this way has its output timing controlled as described above, so that the ultrasonic waves are transmitted from the input positions Q ₁ , Q ₃ , Q ₄ , Q ₁₁ , Q ₁₃ , and Q ₁₅ to the center position P. The generation timing is shifted by times T ₁ , T ₃ , T ₄ , T ₁₁ , T ₁₃ , and T ₁₅ depending on the distance. For example, the ultrasonic wave from the input position Q3 is input to the liquid crystal layer 23 with a delay of time (T ₁ - T ₃ ) with respect to the ultrasonic wave from the input position Q ₁ . In this way, the peaks of all the ultrasound waves from the generating elements 18 ₁ , 18 ₃ , 18 ₄ , 18 ₁₁ , 18 ₁₃ , 18 ₁₅ overlap at the center position P at the same time. In addition, a mountain-shaped standing wave having a peak at the center position P is formed due to the incremental interference of each ultrasonic wave.

Then, by repeatedly inputting half-wavelength ultrasonic waves from the generating elements 18 ₁ , 18 ₃ , 18 ₄ , 18 ₁₁ , 18 ₁₃ , and 18 ₁₅ to the liquid crystal layer 23 with a period T, the peak is set at the center position P. A mountain-shaped standing wave is continuously formed. As a result, a lens region that becomes a convex lens is continuously formed around the center position P. Note that although the lens region that becomes a convex lens is formed by inputting ultrasonic waves for a half wavelength centered at the peak into the liquid crystal layer 23, it is also possible to input ultrasonic waves for a half wavelength centered at the bottom (minimum). It's okay.

When forming a lens region that becomes a concave lens, the initial phase of the selected plurality of generating elements 18 _i is changed from the initial phase when forming a lens region that becomes a convex lens, and for some of the generating elements 18 _i , π/2 , and the remaining part is delayed by π/2, and as described above, the ultrasonic waves from some of the generating elements 18 _i and the ultrasonic waves from the remaining part of the generating elements 18 _i are reversed. All you have to do is take the phase. In this case, a plurality of ultrasonic waves each having a half wavelength centered on the center of vibration are input to the liquid crystal layer 23, respectively. Then, the centers of all the vibrations of each ultrasonic wave for half a wavelength overlap each other at the center position P, and a lens region that becomes a concave lens is formed by the standing waves formed by these incremental interferences. In this case as well, by repeatedly inputting half-wavelength ultrasonic waves to the liquid crystal layer 23 with a period T, a lens region that becomes a concave lens is continuously formed.

When forming either a convex lens region or a concave lens region, the initial phase and output of the ultrasonic waves output from the generating elements 18 ₁ , 18 ₃ , 18 ₄ , 18 ₁₁ , 18 ₁₃ , 18 ₁₅ By changing the timing, the center position P can be changed and a lens region can be formed around the center position P. For example, if the amplitude of the ultrasonic waves output from some or all of the ultrasonic waves output from the generating elements 18 ₁ , 18 ₃ , 18 ₄ , 18 ₁₁ , 18 ₁₃ , 18 ₁₅ is increased or decreased, the generated The focal length depending on the lens area can be changed.

FIG. 11 shows an example in which a disk-shaped (circular in plan view) liquid crystal cell 11A is used to form a lens region that becomes two convex lenses centered at center positions P ₁ and P ₂ . The generating element 18 _i and the input position Q _i will be described in the same manner as in the above example. In the example of FIG. 11, the generating elements _18i of i=3, 4, 6, 9, 10, and 12 are selected.

In the case of forming two lens regions, the selected generating element 18 generates an ultrasonic wave (hereinafter referred to as the first ultrasonic wave) G1 that forms the lens region around the center position _P1 , and an ultrasonic wave G1 that forms the lens area around the center position _P2. Ultrasonic waves (hereinafter referred to as second ultrasonic waves) G2 that form a lens region around G2 are repeatedly input to the liquid crystal layer 23 at a period T from a plurality of selected generating elements 18. In this example, the first ultrasonic wave G1 and the second ultrasonic wave G2 both form a lens region that becomes a convex lens, so both are ultrasonic waves of half a wavelength centered on the peak, for example.

Note that the first ultrasonic wave G1 and the second ultrasonic wave G2 may be half-wavelength ultrasonic waves centered on the bottom; It may also be an ultrasonic wave with a half wavelength around the center. Further, in this example, the generating element 18 that outputs the first ultrasonic wave G1 and the generating element 18 that outputs the second ultrasonic wave G2 are the same, but the generating element 18 that outputs the first ultrasonic wave G1 On the other hand, part or all of the generating element 18 that outputs the second ultrasonic wave G2 may be different.

The initial phase φ _1i of the first ultrasonic wave G1 is set so that the peak of the ultrasonic wave from the generating element 18 _i overlaps with the peak of the ultrasonic wave from each of the other selected generating elements 18 _i at the center position P ₁ be done. Moreover, this first ultrasonic wave G1 is output during a period in which time t is "n・T+T _1i -ΔT+t ₀ ≦t≦n・T+T _1i +ΔT+t ₀ ", and time t is "n・T+t ₀ ≦t≦+n The selected generating element 18i is controlled so that no ultrasonic waves are output during the periods where ・T+T _1i −ΔT+t ₀ ” and “n·T+T _1i +ΔT+t ₀ ≦t≦(n+ ₁ )T+t 0 ”. Note that the time T _1i is the time required for the ultrasonic wave to travel from the input position Q _i to the center position P ₁ in the liquid crystal layer 23 .

The initial phase φ _2i of the second ultrasonic wave G2 is set so that the peak of the ultrasonic wave from the generating element 18 _i overlaps with the peak of the ultrasonic wave from each of the other selected generating elements 18 _i at the center position P ₁ be done. Therefore, when outputting the first ultrasonic wave G1 and the second ultrasonic wave G2, the initial phase settings are switched. Further, this second ultrasonic wave G2 is output during a period in which time t is "n・T+T _2i -ΔT+t ₀ ≦t≦n・T+T _2i +ΔT+t ₀ ", and time t is "n・T+t ₀ ≦t≦+n The selected generating element 18i is controlled so that the ultrasonic wave is not output during the period in which: ・T+T _{2i −ΔT} + _{t 0 ”} and “n·T+T 2i +ΔT+t 0 ≦t _≦ (n+1)T+t 0 ”. Note that the time T _2i is the time required for the ultrasonic wave to travel from the input position Q _i to the center position P ₂ in the liquid crystal layer 23 .

The first ultrasonic wave G1 and the second ultrasonic wave G2 from each of the generating elements 18 selected as described above are repeatedly input into the liquid crystal layer 23 at a period T. This causes all of the first ultrasound waves to repeatedly overlap at the center position _P1 at the same time. Also, all of the second ultrasound waves overlap at the center position _P2 at the same time. As a result, a lens region that becomes a convex lens is formed around the center position _P1 , and at the same time, a lens region that becomes a convex lens is formed around the center position _P2 .

The above example describes an example in which two lens regions that become convex lenses are formed, but by changing the waveforms of the first ultrasound G1 and the second ultrasound G2 as described above, two lens regions that become concave lenses can be formed. It is also possible to form a lens region, or to form two lens regions that are a convex lens and a concave lens. Furthermore, even when a square liquid crystal cell 11 is used, a plurality of lens regions can be formed in the same manner. Furthermore, three or more lens regions can also be formed.

The liquid crystal lens device 10 can form a lens region having a lens effect at any position as described above, and in the liquid crystal cell 11 through which light passes, there are electrodes and the like that cause anisotropy in the lens effect. Since no wiring is provided, deterioration in optical performance is suppressed. In addition, since the formation position of the lens region can be changed by controlling the phase and output timing of the ultrasonic waves output from the generating element 18, even if the position is controlled with high precision, anisotropy may occur in the lens effect. There is no increase in the number of electrodes or wirings, and no further deterioration of optical performance occurs.

A wide-angle foveal lens device can be constructed using the liquid crystal lens device configured as described above. As an example is shown in FIG. 12, the wide-angle foveal lens device 30 includes, in order from the object side, a condenser lens group 31, a liquid crystal cell 32 of lens unit U1A, a liquid crystal cell 33 of lens unit U1B, and an imaging lens group 34. It has lens systems arranged apart in the optical axis direction, drive circuits 37a and 37b provided corresponding to lens units U1A and U1B, and a control section 38. The condensing lens group 31 is composed of one or more lenses for widening the lens system. Further, the imaging lens group 34 is composed of one or more lenses that form an image of the lens system on an image plane (not shown).

Lens units U1A and U1B are configured to include an ultrasonic unit like the lens unit U1 described above. The liquid crystal cells 32 and 33 have substrates arranged perpendicularly to the optical axis of the lens system. The control unit 38 drives a plurality of generating elements (not shown) of the ultrasonic units provided in the liquid crystal cells 32 and 33, respectively, via drive circuits 37a and 37b. As a result, lens regions are formed in the lens system at the positions of the liquid crystal cells 32 and 33 corresponding to the region of interest to be observed with high resolution or high magnification. At this time, the control unit 38 makes the lens region of the liquid crystal cell 32 a convex lens, and the lens region of the liquid crystal cell 33 a concave lens. Thereby, the image magnification of the region of interest is made higher than that of the surrounding region by the combination of the convex lens and the concave lens. In contrast, by making the lens region of the liquid crystal cell 32 a concave lens and the lens region of the liquid crystal cell 33 a convex lens, the image magnification of the region of interest can be made lower than that of the surrounding region.

In the wide-angle foveal lens device 30 as described above, it is necessary to precisely control the formation positions of each lens region that becomes a convex lens and a concave lens, but even when controlling in this way, the optical performance This will not cause a further decrease in Furthermore, by changing the position and lens power of each lens area, the position of the area of interest can be moved and the image magnification of the area of interest can be changed to enlarge or reduce the image of the area of interest. Furthermore, the image magnification of each of the plurality of attention areas can be made high or low, or the image magnification of the attention areas can be made different from each other.

10 Liquid crystal lens device 11, 11A, 32, 33 Liquid crystal cell 12 Ultrasonic unit 15, 38 Control section 18 Ultrasonic wave generating element 21, 22 Substrate 23 Liquid crystal layer 30 Wide-angle foveal lens device

Claims (6)

A liquid crystal cell having a pair of transparent substrates arranged to face each other and having an alignment film formed on the facing surfaces, and a liquid crystal layer made of liquid crystal provided between the pair of transparent substrates;
an ultrasonic unit having a plurality of ultrasonic generating elements provided on a peripheral surface of the liquid crystal cell, the ultrasonic generating elements applying ultrasonic waves to the liquid crystal layer from the peripheral edge of the liquid crystal cell;
The position of the lens area is such that a standing wave having an antinode or node at the center position of the lens area, which is one or more lenses of the liquid crystal layer, is formed by superimposing each ultrasonic wave from the ultrasonic wave generating element. and a control section that controls the phase and output timing of ultrasound from the plurality of ultrasound generating elements based on the following. Claim 1, wherein the number of the ultrasonic generating elements that output ultrasonic waves or the amplitude of the ultrasonic waves output from the ultrasonic generating elements is increased or decreased depending on the focal length of the lens area as a lens. The liquid crystal lens device described in . 2. The liquid crystal lens device according to claim 1, wherein the frequency of the ultrasonic wave is increased or decreased depending on the size of the lens area. 4. The liquid crystal lens device according to claim 1, wherein the liquid crystal cell has a square shape in plan view, and the ultrasonic wave generating element is provided on each peripheral surface. 4. The liquid crystal lens device according to claim 1, wherein the liquid crystal cell has a circular shape in a plan view, and each of the ultrasonic wave generating elements is provided on a peripheral surface of the liquid crystal cell. A first liquid crystal cell and a second liquid crystal layer having a pair of transparent substrates arranged to face each other and having an alignment film formed on their facing surfaces, and a first liquid crystal layer made of liquid crystal provided between the pair of transparent substrates; and a second liquid crystal layer. a second liquid crystal cell having;
a plurality of first ultrasonic generating elements provided on the circumferential surface of the first liquid crystal cell and applying ultrasonic waves from the circumferential edge of the first liquid crystal cell to the first liquid crystal layer; and a plurality of first ultrasonic wave generating elements provided on the circumferential surface of the second liquid crystal cell. an ultrasonic unit having a plurality of second ultrasonic generating elements that apply ultrasonic waves to the second liquid crystal layer from the periphery of the second liquid crystal cell;
One liquid crystal layer of the first liquid crystal layer or the second liquid crystal layer has a standing wave whose center position is a convex lens area, and the other liquid crystal layer has a standing wave whose center position is a concave lens area. The phase and phase of the ultrasonic waves from the plurality of first ultrasonic generating elements are determined based on the position of the lens region in the first liquid crystal layer so that standing waves serving as nodes are formed by superimposing a plurality of ultrasonic waves. A control unit that controls output timing and also controls the phase and output timing of ultrasonic waves from the plurality of second ultrasonic wave generating elements based on the position of the lens region in the second liquid crystal layer. wide-angle foveal lens device.

Images