Variable focus lens and method for controlling the variable focus lens

Abstract

A varifocal gel lens 1 comprising an annular ultrasonic transducer 3, a transparent and elastic lens 4, and a drive unit 5 that applies an electric signal to the ultrasonic transducer 3 to generate an ultrasonic wave is characterized in that the ultrasonic transducer 3 includes four electrodes 31 to 34 divided into N in the circumferential direction, and the drive unit 5 has a traveling wave mode in which electric signals of different phases that increase or decrease in the circumferential direction are applied to the four electrodes 31 to 34 and an ultrasonic wave propagating in the circumferential direction of the lens 4 is generated to raise a peripheral portion of the lens 4.

Description

[Technical Field]

[0001] The present invention relates to a variable focus lens and a method for controlling a variable focus lens. [Background technology]

[0002] A known variable-focus gel lens is described in Patent Document 1, for example. The variable-focus gel lens described in Patent Document 1 includes an annular ultrasonic transducer with a central opening and a lens made of transparent viscoelastic gel placed in the central opening. The variable-focus gel lens described in Patent Document 1 can deform the center of the lens into a convex shape by pushing up the surface of the transparent viscoelastic gel with the acoustic radiation force of ultrasound generated by the ultrasonic transducer. Furthermore, the focal length can be controlled by controlling the voltage value of the electrical signal applied to the ultrasonic transducer.

[0003] In order to apply a variable-focus gel lens to eyeglass devices such as smart glasses, it is preferable to realize both concave and concave shapes in a single lens and to be able to control the focal length for both the concave and concave shapes. However, the variable-focus gel lens described in Patent Document 1 has the problem that the center of the lens cannot be deformed into a concave shape. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-61549 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a variable-focus lens and a method for controlling a variable-focus lens that can deform the center of the lens into a concave shape and control the focal length in the concave shape. [Means for solving the problem]

[0006] In order to solve the above problems, the variable focus lens according to the present invention comprises: an annular ultrasonic transducer having a central opening; a transparent and elastic lens disposed in the central opening; a driving unit that applies an electric signal to the ultrasonic vibrator to generate ultrasonic waves and deforms the shape of the lens using the ultrasonic waves; A variable focus lens comprising: The ultrasonic transducer is provided with N electrodes (N is an integer of 3 or more) divided into N parts in the circumferential direction, The drive unit is The electrical signals are applied to the N electrodes at different phases and with phases that increase or decrease in the circumferential direction, generating a traveling wave of the ultrasonic waves that propagates in the circumferential direction of the lens, and the traveling wave causes the peripheral part of the lens to rise relative to the center part.

[0007] With this configuration, the pressure on the periphery of the lens is increased by the traveling ultrasonic wave, causing the periphery to bulge, thereby deforming the center of the lens into a concave shape. Also, the focal length can be controlled by controlling the voltage value of the electrical signal.

[0008] In the variable focus lens, The drive unit is It is preferable that the electrical signals of the same phase are applied to the N electrodes to generate standing waves of the ultrasonic waves, and that the central portion of the lens is raised relative to the peripheral portion by the standing waves.

[0009] According to this configuration, it is possible to realize both concave and convex shapes with a single lens, and it is also possible to control the focal length for both the concave and convex shapes.

[0010] In the variable focus lens, the N electrodes have the same shape; The electrical signals may be shifted in phase by (360 / N) degrees in the circumferential direction for the N electrodes.

[0011] In the variable focus lens, The lens may be made of a transparent viscoelastic gel.

[0012] In the variable focus lens, The lens is A liquid material; a film material formed to cover the surface of the liquid material and whose shape is deformed by the ultrasonic waves.

[0013] In order to solve the above problem, a method for controlling a variable-focus lens according to the present invention includes: A method for controlling a variable-focus lens comprising: an ultrasonic transducer formed in an annular shape having a central opening and divided into N electrodes in a circumferential direction (N is an integer of 3 or more); a transparent and elastic lens disposed in the central opening; and a driver that applies an electric signal to the ultrasonic transducer to generate ultrasonic waves, The method is characterized by including a first step in which the driving unit applies the electrical signals to the N electrodes with different phases and with phases that increase or decrease in the circumferential direction, generating a traveling wave of the ultrasonic waves that propagates in the circumferential direction of the lens, and the traveling wave causes the peripheral part of the lens to rise relative to the center part.

[0014] With this configuration, the pressure on the periphery of the lens is increased by the traveling ultrasonic wave, causing the periphery to bulge, thereby deforming the center of the lens into a concave shape. Also, the focal length can be controlled by controlling the voltage value of the electrical signal.

[0015] In the method for controlling a variable-focus lens, The method can be configured to include a second step of applying the electrical signals of the same phase to the N electrodes by the driving unit to generate standing waves of the ultrasonic waves, and causing the central part of the lens to rise relative to the peripheral part by the standing waves.

[0016] According to this configuration, it is possible to realize both concave and convex shapes with a single lens, and it is also possible to control the focal length for both the concave and convex shapes.

[0017] In the method for controlling a variable-focus lens, The lens may be made of a transparent viscoelastic gel.

[0018] In the method for controlling a variable-focus lens, The lens is A liquid material; a film material formed to cover the surface of the liquid material and whose shape is deformed by the ultrasonic waves. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a variable-focus lens and a method for controlling a variable-focus lens, in which the center of the lens can be deformed into a concave shape and the focal length can be controlled in the concave shape. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are plan and cross-sectional views of a variable focus lens according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing vibration intensity on the upper surface of the lens in a standing wave mode. [Figure 3] FIG. 10 is a diagram showing vibration intensity on the upper surface of the lens in a traveling wave mode. [Figure 4] FIG. 10 is a diagram showing the relationship between the peak-to-peak voltage value of an electrical signal in a standing wave mode and the cross-sectional shape of a lens. [Figure 5] FIG. 10 is a diagram showing the relationship between the peak-to-peak voltage value of an electrical signal in a traveling wave mode and the cross-sectional shape of a lens. [Figure 6] 1A and 1B are plan and cross-sectional views of a variable focus lens according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of a variable-focus lens and a variable-focus lens control method according to the present invention will be described with reference to the accompanying drawings. Note that a variable-focus gel lens will be used as an example of the variable-focus lens in the first embodiment, and a variable-focus liquid lens will be used as an example of the variable-focus lens in the second embodiment.

[0022] [First embodiment] (variable focus gel lens) 1 shows a variable-focus gel lens 1 according to the first embodiment. The variable-focus gel lens 1 includes a substrate 2, an ultrasonic transducer 3, a lens 4, and a driving unit 5.

[0023] The substrate 2 is a glass substrate formed in a disk shape, and has a diameter of 30 mm and a thickness of 0.7 mm.

[0024] The ultrasonic transducer 3 is a circular piezoelectric ultrasonic transducer with a central opening, and is made of lead zirconate titanate (PZT). The ultrasonic transducer 3 has an inner diameter of 20 mm, an outer diameter of 30 mm, and a thickness of 1 mm.

[0025] The ultrasonic transducer 3 is provided with four aluminum electrodes (first electrode 31, second electrode 32, third electrode 33, and fourth electrode 34) divided into four in the circumferential direction. All four aluminum electrodes are made up of a positive electrode and a negative electrode that are insulated from each other and have the same shape.

[0026] The first electrode 31 consists of a first positive electrode 31a and a first negative electrode 31b. The second electrode 32 consists of a second positive electrode 32a and a second negative electrode 32b. The third electrode 33 consists of a third positive electrode 33a and a third negative electrode 33b. The fourth electrode 34 consists of a fourth positive electrode 34a and a fourth negative electrode 34b. The first negative electrode 31b, the second negative electrode 32b, the third negative electrode 33b, and the fourth negative electrode 34b are connected to a common negative electrode formed on the lower surface side (substrate 2 side) of the ultrasonic transducer 3.

[0027] The lens 4 is made of a transparent viscoelastic gel and is placed in the central opening of the ultrasonic transducer 3. The lens 4 has a thickness of 0.5 mm. The transparent viscoelastic gel is transparent to visible light, can maintain its shape against gravity, and can deform under pressure due to acoustic radiation force. In this embodiment, the transparent viscoelastic gel is a silicone gel made of hydrophobic silica particles and silicone oil, with the mass ratio of the hydrophobic silica particles being 7%.

[0028] The driving unit 5 has a traveling wave mode and a standing wave mode as driving modes, and is configured to generate ultrasonic waves by applying an electric signal (AC voltage signal) to the ultrasonic transducer 3. The driving unit 5 includes a first driving unit 51 connected to the first electrode 31, a second driving unit 52 connected to the second electrode 32, a third driving unit 53 connected to the third electrode 33, and a fourth driving unit 54 connected to the fourth electrode 34. The first driving unit 51 to the fourth driving unit 54 can each independently control the phase, voltage value, and frequency of the electric signal.

[0029] In the standing wave mode, the driver 5 applies in-phase electrical signals to the ultrasonic transducer 3. That is, the first driver 51 to the fourth driver 54 apply in-phase electrical signals to the first electrode 31 to the fourth electrode 34 to which they are connected, respectively. The first electrode 31 to the fourth electrode 34 generate ultrasonic waves of a predetermined frequency according to the electrical signals. For example, the first electrode 31 to the fourth electrode 34 generate ultrasonic waves having a frequency that matches the resonant frequency of the lens 4.

[0030] When the ultrasonic waves generated by the first electrode 31 to the fourth electrode 34 propagate to the lens 4, standing waves of ultrasonic waves (acoustic standing waves), specifically standing waves of flexural vibration in the first mode, are generated in the lens 4. The flexural vibration in the first mode refers to vibration in which the vibration intensity decreases continuously from the center of the lens 4 toward the outer periphery. In the present invention, the center of the lens 4 and its vicinity are defined as the central portion, and the area around the central portion (the entire lens 4 other than the central portion) is defined as the peripheral portion.

[0031] When a standing wave of flexural vibration occurs in lens 4, pressure due to the acoustic radiation force of the standing wave acts on the boundary surface between the upper surface of lens 4 and air and the boundary surface between the lower surface of lens 4 and substrate 2. The pressure due to the acoustic radiation force of the standing wave is highest at the center of lens 4, causing the center to bulge and deform into a convex shape.

[0032] Furthermore, changing the voltage value of the electrical signal changes the pressure due to the acoustic radiation force of the standing wave, which in turn changes the height of the convex shape at the center of lens 4, thereby changing the focal length. Therefore, by controlling the voltage value of the electrical signal with driver 5, the focal length of the convex shape can be controlled.

[0033] In the traveling wave mode, the driver 5 applies electrical signals to the first electrode 31 to the fourth electrode 34, the phases of which are shifted by 90° in the circumferential direction (incremented by 90°). That is, with respect to the electrical signal applied to the first electrode 31 by the first driver 51, the electrical signal applied to the second electrode 32 by the second driver 52 has a phase difference of 90°, the electrical signal applied to the third electrode 33 by the third driver 53 has a phase difference of 180°, and the electrical signal applied to the fourth electrode 34 by the fourth driver 54 has a phase difference of 270°. The first electrode 31 to the fourth electrode 34 generate ultrasonic waves according to each electrical signal.

[0034] When the ultrasonic waves generated by the first to fourth electrodes 31 to 34 propagate to the lens 4, the lens 4 generates ultrasonic traveling waves (acoustic traveling waves) that propagate in the circumferential direction, that is, traveling waves of flexural vibration.

[0035] When a traveling wave of flexural vibration is generated in the lens 4, pressure due to the acoustic radiation force of the traveling wave acts on the boundary surface between the upper surface of the lens 4 and the air and the boundary surface between the lower surface of the lens 4 and the substrate 2. The pressure due to the acoustic radiation force of the traveling wave is higher at the periphery of the lens 4, causing the periphery to rise. As the periphery rises, the center sinks and deforms into a concave shape.

[0036] Furthermore, changing the voltage value of the electric signal changes the pressure due to the acoustic radiation force of the traveling wave, which in turn changes the depth of the concave shape at the center of lens 4, thereby changing the focal length. Therefore, by controlling the voltage value of the electric signal with driver 5, the focal length of the concave shape can be controlled.

[0037] (Variable focus gel lens control method) The control method for the variable-focus gel lens according to the first embodiment is the control method for the variable-focus gel lens 1. That is, the control method includes a first step of changing the lens 4 into a concave shape and a second step of changing the lens 4 into a convex shape.

[0038] In the first step, the driving unit 5 (first driving unit 51 to fourth driving unit 54) applies electrical signals to the first electrode 31 to the fourth electrode 34, the phases of which are shifted by 90° in the circumferential direction (increased by 90° increments), to generate traveling waves of flexural vibration that propagate in the circumferential direction of the lens 4. The electrical signals output by the first driving unit 51 to the fourth driving unit 54 differ only in phase, but have the same voltage value (in this embodiment, peak-to-peak voltage value = 10 [Vpp]) and frequency (in this embodiment, 26 [kHz]).

[0039] When a traveling wave of flexural vibration is generated in the lens 4, pressure due to the acoustic radiation force of the traveling wave acts on the transparent viscoelastic gel of the lens 4, causing the peripheral part of the transparent viscoelastic gel to rise. As the peripheral part rises, the center of the transparent viscoelastic gel sinks, and the lens 4 is deformed into a concave shape.

[0040] In the second step, the driving unit 5 (first driving unit 51 to fourth driving unit 54) applies in-phase electrical signals to the first electrode 31 to fourth electrode 34, thereby generating a standing wave of flexural vibration in the lens 4. The electrical signals output by the first driving unit 51 to fourth driving unit 54 also have the same voltage value (in this embodiment, peak-to-peak voltage value=10 [Vpp]) and frequency (in this embodiment, 40 [kHz]).

[0041] When a standing wave of flexural vibration occurs in the lens 4, pressure due to the acoustic radiation force of the standing wave acts on the transparent viscoelastic gel of the lens 4, causing the center of the transparent viscoelastic gel to bulge, resulting in the lens 4 being deformed into a convex shape.

[0042] In the first and second steps, when the first to fourth driving units 51 to 54 change the voltage values ​​of the electrical signals, the focal length of the lens 4 changes. Furthermore, when the first to fourth driving units 51 to 54 change the voltage values ​​of the electrical signals by different amounts, it is possible to control not only the focal length but also the focal position on the XY plane.

[0043] (Evaluation experiment) Next, an evaluation experiment of the variable-focus gel lens 1 and its control method will be described.

[0044] 2 and 3 are images observed using a laser Doppler vibrometer (LDV) showing the vibration intensity distribution on the upper surface of lens 4. Fig. 2 is an image in standing wave mode, and Fig. 3 is an image in traveling wave mode.

[0045] From Figure 2, it can be seen that in the standing wave mode, the vibration intensity of the flexural vibration is higher at the center of the lens 4. This result indicates that the center of the lens 4 has a convex shape. From Figure 3, it can be seen that in the traveling wave mode, the vibration intensity of the flexural vibration is higher at the periphery of the lens 4 and lower at the center. This result indicates that the center of the lens 4 has a concave shape.

[0046] Fig. 4 is a diagram showing the relationship between the peak-to-peak voltage value Vpp of the electric signal in standing wave mode and the cross-sectional shape of the lens 4. Fig. 5 is a diagram showing the relationship between the peak-to-peak voltage value Vpp of the electric signal in traveling wave mode and the cross-sectional shape of the lens 4. In Figs. 4 and 5, the vertical axis indicates the top surface position of the lens 4, with the top surface position when no electric signal is applied being set to 0. The horizontal axis indicates the radial position of the lens 4 (X direction), with the center of the lens 4 being set to 0.

[0047] From Figure 4, we can see that in standing wave mode, the center of lens 4 becomes convex and the higher the peak-to-peak voltage value Vpp of the electrical signal, the higher the upper surface position of the center. From Figure 5, we can see that in traveling wave mode, the center of lens 4 becomes concave and the higher the peak-to-peak voltage value Vpp of the electrical signal, the lower the upper surface position of the center. These results show that by controlling the peak-to-peak voltage value Vpp of the electrical signal, it is possible to control the focal length for both convex and concave shapes.

[0048] Ultimately, the variable focus gel lens 1 and its control method can realize both concave and convex lens functions in a single lens (for example, a lens that can be switched between nearsightedness and farsightedness), which is required for eyeglass devices such as smart glasses, and can provide a multifunctional, thin variable focus lens.

[0049] [Second embodiment] (variable focus liquid lens) 6 shows a variable-focus liquid lens 1' according to the second embodiment. The variable-focus liquid lens 1' is the same as the first embodiment except that it includes a lens 4' made of a liquid lens instead of the lens 4 made of a gel lens.

[0050] 6(B), lens 4' includes liquid material 4a and film material 4b formed to cover the surface (upper surface) of liquid material 4a. In this way, in the present invention, a lens made up of a liquid material and a film material is called a liquid lens.

[0051] In the variable-focus liquid lens 1', the gaps between the ultrasonic transducers 3 and the gap between the ultrasonic transducers 3 and the substrate 2 are sealed with a sealing material (for example, a resin material such as epoxy resin), so there is no risk of the liquid material 4a leaking out from the central opening of the ultrasonic transducers 3. For this reason, the film material 4b is formed only on the surface (upper surface) of the liquid material 4a so as to have a predetermined tension. However, the film material 4b may be formed on the side surface (outer peripheral surface) of the liquid material 4a in addition to the surface of the liquid material 4a, or may be formed on the back surface (lower surface) of the liquid material 4a.

[0052] The liquid material 4a may be any material that is transparent to visible light and has a low viscosity, such as a liquid or liquid-like material. For example, water, silicone oil, or a fluorine-based inert liquid may be used as the liquid material 4a. The liquid material 4a has a thickness of, for example, 300 μm to 1000 μm when filled in the central opening of the ultrasonic transducer 3.

[0053] The film material 4b may be any film that is transparent to visible light, can maintain its shape (the shape of the lens 4') against gravity, and can be deformed by pressure from acoustic radiation force. In this embodiment, the film deforms from a flat shape to a curved shape that is concave or convex. For example, silicone rubber (e.g., PDMS), fluororubber, or urethane rubber can be used as the film material 4b. The film material 4b has a thickness of, for example, 50 μm to 500 μm, and is preferably thinner than the liquid material 4a.

[0054] In this embodiment, the thickness of the film material 4b is uniform, but it may be non-uniform. For example, the thickness of the film material 4b may be different between the center and the peripheral portion. Furthermore, in this embodiment, when no electrical signal is applied to the ultrasonic transducer 3, the film material 4b has a flat shape, but it may also have a concave or convex curved shape.

[0055] When a standing wave of flexural vibration occurs in lens 4', pressure due to the acoustic radiation force of the standing wave acts on the interface between the upper surface of film material 4b and air, the interface between the lower surface of film material 4b and the upper surface of liquid material 4a, the interface between the lower surface of liquid material 4a and the upper surface of substrate 2, and the interface between the lower surface of substrate 2 and air. However, it is the acoustic radiation force of the standing wave acting on the interface between the upper surface of film material 4b and air that contributes most to the deformation of lens 4'. The pressure due to this acoustic radiation force is highest at the center of the upper surface of film material 4b, causing the center of film material 4b to bulge. The bulging of the center of film material 4b increases the thickness of the center of liquid material 4a, and lens 4' is deformed into a convex shape.

[0056] Furthermore, when the voltage value of the electrical signal is changed, the pressure due to the acoustic radiation force of the standing wave changes, which in turn changes the height of the convex shape at the center of lens 4', thereby changing the focal length. Therefore, by controlling the voltage value of the electrical signal with driver 5, the focal length of the convex shape can be controlled.

[0057] When a traveling wave of flexural vibration is generated in lens 4', pressure due to the acoustic radiation force of the traveling wave acts on the interface between the upper surface of film material 4b and air, the interface between the lower surface of film material 4b and the upper surface of liquid material 4a, the interface between the lower surface of liquid material 4a and the upper surface of substrate 2, and the interface between the lower surface of substrate 2 and air. However, it is the acoustic radiation force of the traveling wave acting on the interface between the upper surface of film material 4b and air that contributes most to the deformation of lens 4'. The pressure due to this acoustic radiation force is higher at the periphery of the upper surface of film material 4b, causing the periphery of film material 4b to bulge. As the periphery of film material 4b bulges, the center of film material 4b sinks (the thickness of the periphery of liquid material 4a increases, while the thickness of the center of liquid material 4a decreases), and lens 4' deforms into a concave shape.

[0058] Furthermore, when the voltage value of the electric signal is changed, the pressure due to the acoustic radiation force of the traveling wave changes, and the depth of the concave shape at the center of lens 4' also changes, changing the focal length. Therefore, by controlling the voltage value of the electric signal with driver 5, the focal length of the concave shape can be controlled.

[0059] The focusing response time of the lens 4' depends on the viscosity of the material constituting the lens 4'. For example, a high-viscosity material will have a slower response speed at the start of the shape change, while a low-viscosity material will have a faster response speed at the start of the shape change. In this embodiment, because the lens 4' contains the liquid material 4a, the response speed at the start of the shape change is faster than in the first embodiment, and the focusing response time can be shortened. Note that if the viscosity is too low, ringing occurs after the start of the shape change, which may actually lengthen the time it takes to reach a steady state. However, in this embodiment, ringing can be suppressed to some extent by adjusting the tension and thickness (mass) of the film material 4b and optimizing the viscosity of the liquid material 4a.

[0060] (Method for controlling a variable-focus liquid lens) The control method for the variable-focus liquid lens according to the second embodiment is the control method for the variable-focus liquid lens 1′ described above, which includes a first step of changing the shape of the lens 4′ to a concave shape and a second step of changing the shape of the lens 4′ to a convex shape.

[0061] In the first step, the driving unit 5 (first driving unit 51 to fourth driving unit 54) applies electrical signals to the first electrode 31 to the fourth electrode 34, the phases of which are shifted by 90° (increased by 90°) in the circumferential direction, to generate traveling waves of flexural vibration that propagate in the circumferential direction of the lens 4'. The electrical signals output by the first driving unit 51 to the fourth driving unit 54 differ only in phase, but have the same voltage value and frequency.

[0062] When a traveling wave of flexural vibration occurs in lens 4', pressure due to the acoustic radiation force of the traveling wave acts mainly on the boundary between the upper surface of film material 4b and the air, causing the peripheral part of film material 4b to rise. As the peripheral part rises, the center of film material 4b sinks (the thickness of the peripheral part of liquid material 4a increases, while the thickness of the central part of liquid material 4a decreases), and lens 4' is deformed into a concave shape.

[0063] In the second step, the driving unit 5 (first driving unit 51 to fourth driving unit 54) applies in-phase electrical signals to the first electrode 31 to the fourth electrode 34, generating a standing wave of flexural vibration in the lens 4'. The electrical signals output by the first driving unit 51 to the fourth driving unit 54 have the same voltage value and frequency.

[0064] When a standing wave of flexural vibration occurs in lens 4', pressure due to the acoustic radiation force of the standing wave acts mainly on the boundary between the upper surface of film material 4b and the air, causing the center of film material 4b to bulge (the thickness of the center of liquid material 4a increases). As a result, lens 4' is deformed into a convex shape.

[0065] In the first and second steps, when the first to fourth driving units 51 to 54 change the voltage values ​​of the electrical signals, the focal length of the lens 4' changes. Furthermore, when the first to fourth driving units 51 to 54 change the voltage values ​​of the electrical signals by different amounts, it is possible to control not only the focal length but also the focal position in the XY plane. Furthermore, since this embodiment uses a lens 4' containing a liquid material 4a, it is possible to shorten the focusing response time compared to the first embodiment.

[0066] [Variations] Although the embodiments of the variable-focus lens and the control method for the variable-focus lens according to the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0067] The variable focus lens of the present invention is a variable focus lens comprising an annular ultrasonic vibrator having a central opening, a transparent and elastic lens placed in the central opening, and a drive unit that applies an electrical signal to the ultrasonic vibrator to generate ultrasonic waves and deform the shape of the lens using the ultrasonic waves, wherein the ultrasonic vibrator has N electrodes (N is an integer of 3 or more) divided into N parts in the circumferential direction, and the drive unit applies electrical signals to the N electrodes with different phases and with phases that increase or decrease in the circumferential direction, generating traveling waves of ultrasonic waves that propagate in the circumferential direction of the lens, and the configuration can be modified as appropriate as long as the traveling waves cause the peripheral part of the lens to rise relative to the center.

[0068] In the above embodiment, the driving unit 5 applies electrical signals to the first electrode 31 to the fourth electrode 34 with the phase increasing by 90° in the circumferential direction, but an electrical signal of any phase may be applied as long as it can generate a traveling wave of ultrasonic waves that propagate in the circumferential direction of the lens 4 (4').

[0069] The variable-focus gel lens 1 according to the first embodiment includes a substrate 2, but does not need to include the substrate 2 as long as the lens 4 can be held in the central opening of the ultrasonic transducer 3. The variable-focus liquid lens 1' according to the second embodiment can also omit the substrate, but in that case, it is necessary to form the film material 4b on the back surface (lower surface) of the liquid material 4a as well.

[0070] The lens 4 of the first embodiment is configured to be transparent to visible light, but can also be configured to be transparent to the wavelength range of light used in the lens 4. For example, if ultraviolet light is used, the material only needs to be transparent to ultraviolet light, and if infrared light is used, the material only needs to be transparent to infrared light. Similarly, the liquid material 4a and film material 4b that make up the lens 4' of the second embodiment can also be configured to be transparent to the wavelength range of light used.

[0071] The control method for a variable-focus lens according to the present invention can be configured as appropriate, provided that it includes a first step in which a driving unit of the variable-focus lens according to the present invention applies electrical signals of different phases and with phases that increase or decrease circumferentially to N electrodes of an ultrasonic vibrator, generating traveling waves of ultrasonic waves that propagate circumferentially around the lens, and causing the peripheral portion of the lens to rise relative to the center portion using the traveling waves. [Explanation of symbols]

[0072] 1 Variable Focus Gel Lens 1' Variable Focus Liquid Lens 2 boards 3 Ultrasonic transducer 31 1st electrode 31a 1st positive electrode 31b 1st negative electrode 32 2nd electrode 32a 2nd positive electrode 32b 2nd negative electrode 33 Third electrode 33a Third positive electrode 33b Third negative electrode 34 4th electrode 34a 4th positive electrode 34b 4th negative electrode 4, 4' lens 4a liquid material 4b Membrane material 5 Drive unit 51 First drive unit 52 Second drive unit 53 Third drive unit 54 4th drive unit

Claims

1. an annular ultrasonic transducer having a central opening; a transparent and elastic lens disposed in the central opening; a driving unit that applies an electric signal to the ultrasonic vibrator to generate ultrasonic waves and deforms the shape of the lens using the ultrasonic waves; A variable focus lens comprising: The ultrasonic transducer includes N electrodes (N is an integer of 3 or more) divided into N parts in the circumferential direction, The drive unit is The electrical signals are applied to the N electrodes with different phases and with phases that increase or decrease in the circumferential direction, generating traveling waves of the ultrasonic waves that propagate in the circumferential direction of the lens, and the traveling waves cause the peripheral portion of the lens to rise relative to the center portion. A variable focus lens characterized by:

2. the driving unit has a traveling wave mode and a standing wave mode as driving modes, the driving unit in the traveling wave mode causes the peripheral portion to rise relative to the central portion by the traveling wave; In the standing wave mode, the driving unit applies the electrical signals of the same phase to the N electrodes to generate standing waves of the ultrasonic waves, and the central portion of the lens is raised relative to the peripheral portion by the standing waves.

2. The variable focus lens according to claim 1.

3. The N electrodes have the same shape, The electrical signals are shifted in phase by (360 / N) degrees in the circumferential direction for the N electrodes.

2. The variable focus lens according to claim 1.

4. The lens is made of a transparent viscoelastic gel.

2. The variable focus lens according to claim 1.

5. The lens is A liquid material; a membrane material formed to cover the surface of the liquid material and whose shape is deformed by the ultrasonic waves; 2. The variable focus lens according to claim 1.

6. A method for controlling a variable-focus lens comprising: an ultrasonic transducer formed in an annular shape having a central opening and divided into N electrodes in a circumferential direction (N being an integer of 3 or more); a transparent and elastic lens disposed in the central opening; and a driver that applies an electric signal to the ultrasonic transducer to generate ultrasonic waves, The method includes a first step of applying the electrical signals, which have different phases and whose phases are increased or decreased in the circumferential direction, to the N electrodes by the driving unit, thereby generating traveling waves of the ultrasonic waves that propagate in the circumferential direction of the lens, and causing the peripheral portion of the lens to rise relative to the center portion by the traveling waves. A method for controlling a variable focus lens.

7. a second step of applying the electrical signals of the same phase to the N electrodes by the driving unit to generate standing waves of the ultrasonic waves, and causing the central portion of the lens to rise relative to the peripheral portion by the standing waves.

7. The method for controlling a variable-focus lens according to claim 6.

8. The lens is made of a transparent viscoelastic gel.

7. The method for controlling a variable-focus lens according to claim 6.

9. The lens is A liquid material; a membrane material formed to cover the surface of the liquid material and whose shape is deformed by the ultrasonic waves; 7. The method for controlling a variable-focus lens according to claim 6.

Images