JP7783604B2 - Variable focus lens and method for controlling the variable focus lens - Google Patents

Description

The present invention relates to a variable focus lens and a method for controlling a variable focus lens.

One known example of a variable-focus gel lens is that described in Patent Document 1. The variable-focus gel lens described in Patent Document 1 comprises 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.

To apply variable-focus gel lenses to eyeglass devices such as smart glasses, it is desirable to achieve both concave and concave shapes in a single lens and to be able to control the focal length for both 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.

JP 2013-61549 A

The present invention was made in consideration of the above circumstances, and its objective 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.

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 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 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.

With this configuration, the traveling ultrasonic waves increase the pressure on the periphery of the lens, causing the periphery to bulge, thereby deforming the center of the lens into a concave shape. Furthermore, the focal length can be controlled by controlling the voltage value of the electrical signal.

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.

With this configuration, both concave and convex shapes can be achieved with a single lens, and the focal length can be controlled for both convex and concave shapes.

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.

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

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.

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 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 is characterized by including a first step in which the driving unit applies the electrical signals of different phases and of which phases increase or decrease in the circumferential direction to the N electrodes, 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.

With this configuration, the traveling ultrasonic waves increase the pressure on the periphery of the lens, causing the periphery to bulge, thereby deforming the center of the lens into a concave shape. Furthermore, the focal length can be controlled by controlling the voltage value of the electrical signal.

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.

With this configuration, both concave and convex shapes can be achieved with a single lens, and the focal length can be controlled for both convex and concave shapes.

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

In the method for controlling a variable-focus lens,
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.

The present invention provides 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.

1A and 1B are a plan view and a cross-sectional view, respectively, of a variable focus lens according to a first embodiment of the present invention. FIG. 10 is a diagram showing vibration intensity on the upper surface of the lens in a standing wave mode. FIG. 10 is a diagram showing vibration intensity on the upper surface of the lens in a traveling wave mode. 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. 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. 1A and 1B are a plan view and a cross-sectional view, respectively, of a variable focus lens according to a second embodiment of the present invention.

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

[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.

Substrate 2 is a glass substrate formed in a disk shape. Substrate 2 has a diameter of 30 mm and a thickness of 0.7 mm.

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

The ultrasonic transducer 3 has four aluminum electrodes (first electrode 31, second electrode 32, third electrode 33, and fourth electrode 34) divided into four parts in the circumferential direction. All four aluminum electrodes consist of a positive electrode and a negative electrode that are insulated from each other and have the same shape.

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 underside (substrate 2 side) of the ultrasonic vibrator 3.

Lens 4 is made of a transparent viscoelastic gel and is placed in the central opening of the ultrasonic transducer 3. 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 from 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 hydrophobic silica particles being 7%.

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

In 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. The first electrode 31 to the fourth electrode 34 generate ultrasonic waves at a predetermined frequency corresponding to the electrical signal. For example, the first electrode 31 to the fourth electrode 34 generate ultrasonic waves with a frequency that matches the resonant frequency of the lens 4.

When 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 primary mode flexural vibration, are generated in the lens 4. Primary mode flexural vibration 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.

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 between the upper surface of lens 4 and air and the boundary 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.

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 drive unit 5, the focal length of the convex shape can be controlled.

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

When the ultrasonic waves generated by the first electrode 31 to the fourth electrode 34 propagate to the lens 4, a traveling wave of ultrasonic waves (acoustic traveling wave) propagating in the circumferential direction, i.e., a traveling wave of flexural vibration, is generated in the lens 4.

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

Furthermore, when the voltage value of the electrical 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 electrical signal with drive unit 5, the focal length of the concave shape can be controlled.

(Method for controlling a variable focus gel lens)
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.

In the first step, the drive unit 5 (first drive unit 51 to fourth drive unit 54) applies electrical signals to the first electrode 31 to the fourth electrode 34, with the phases shifted by 90° (increased by 90°) in the circumferential direction, generating traveling waves of flexural vibration that propagate in the circumferential direction of the lens 4. The electrical signals output by the first drive unit 51 to the fourth drive 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).

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 transparent viscoelastic gel of lens 4, causing the peripheral portion of the transparent viscoelastic gel to rise. As the peripheral portion rises, the center of the transparent viscoelastic gel sinks, and lens 4 is deformed into a concave shape.

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, generating standing waves 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).

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 transparent viscoelastic gel of lens 4, causing the center of the transparent viscoelastic gel to bulge. As a result, lens 4 is deformed into a convex shape.

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

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

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

Figure 2 shows that in the standing wave mode, the vibration intensity of the flexural vibration is higher at the center of lens 4. This result indicates that the center of lens 4 has a convex shape. Figure 3 shows that in the traveling wave mode, the vibration intensity of the flexural vibration is higher at the periphery of lens 4 and lower at the center. This result indicates that the center of lens 4 has a concave shape.

Figure 4 shows the relationship between the peak-to-peak voltage value Vpp of the electrical signal in standing wave mode and the cross-sectional shape of lens 4. Figure 5 shows the relationship between the peak-to-peak voltage value Vpp of the electrical signal in traveling wave mode and the cross-sectional shape of lens 4. In Figures 4 and 5, the vertical axis indicates the top surface position of lens 4, with the top surface position when no electrical signal is applied being set to 0. The horizontal axis indicates the radial position (X direction) of lens 4, with the center of lens 4 being set to 0.

Figure 4 shows 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 top surface position of the center. Figure 5 shows 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 top surface position of the center. These results show that by controlling the peak-to-peak voltage value Vpp of the electrical signal, the focal length can be controlled for both convex and concave shapes.

In the end, the variable focus gel lens 1 and its control method can achieve 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.

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.

As shown in Figure 6(B), the lens 4' includes a liquid material 4a and a film material 4b formed to cover the surface (top surface) of the 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.

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 (e.g., a resin material such as epoxy resin), so there is no risk of the liquid material 4a leaking out of the central opening of the ultrasonic transducer 3. For this reason, the film material 4b is formed only on the surface (top surface) of the liquid material 4a so as to have a predetermined tension. However, in addition to the surface of the liquid material 4a, the film material 4b may also be formed on the side (outer peripheral surface) of the liquid material 4a or on the back surface (bottom surface) of the liquid material 4a.

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 substance. Examples of the liquid material 4a include water, silicone oil, and a fluorine-based inert liquid. When filled into the central opening of the ultrasonic transducer 3, the liquid material 4a has a thickness of, for example, 300 μm to 1000 μm.

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 deform under pressure from acoustic radiation force. In this embodiment, it deforms from a flat shape to a concave or convex curved shape. Examples of materials that can be used as the film material 4b include silicone rubber (e.g., PDMS), fluororubber, and urethane rubber. The film material 4b has a thickness of, for example, 50 μm to 500 μm, and is preferably thinner than the liquid material 4a.

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

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' deforms into a convex shape.

Furthermore, when the voltage value of the electrical signal is changed, the pressure due to the acoustic radiation force of the standing wave changes, and the height of the convex shape at the center of lens 4' also changes, changing the focal length. Therefore, by controlling the voltage value of the electrical signal with drive unit 5, the focal length of the convex shape can be controlled.

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 rise. As the periphery of film material 4b rises, 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.

Furthermore, changing the voltage value of the electrical 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 electrical signal with drive unit 5, the focal length of the concave shape can be controlled.

The focusing response time of lens 4' depends on the viscosity of the material comprising 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 lens 4' contains 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 will occur 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 film material 4b and optimizing the viscosity of liquid material 4a.

(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, that is, the control method 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.

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

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

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 also have the same voltage value and frequency.

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 membrane material 4b and the air, causing the center of membrane material 4b to bulge (the thickness of the center of liquid material 4a increases). As a result, lens 4' deforms into a convex shape.

In the first and second steps, when the first to fourth driving units 51 to 54 change the voltage value of the electrical signal, the focal length of the lens 4' changes. Furthermore, if the first to fourth driving units 51 to 54 change the voltage value of each electrical signal 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 liquid material 4a, the focusing response time can be shortened compared to the first embodiment.

[Modification]
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.

The variable-focus lens of the present invention is a variable-focus lens comprising an annular ultrasonic transducer having a central opening, a transparent and elastic lens positioned in the central opening, and a drive unit that applies an electrical signal to the ultrasonic transducer to generate ultrasonic waves and deform the shape of the lens using the ultrasonic waves.The ultrasonic transducer has N electrodes (N is an integer of 3 or greater) divided circumferentially into N parts, and the drive unit applies electrical signals to the N electrodes with different phases and with phases that increase or decrease circumferentially, generating traveling waves of ultrasonic waves that propagate circumferentially around the lens, and the configuration can be modified as appropriate, as long as the traveling waves cause the peripheral portion of the lens to rise relative to the center.

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 electrical signals of any phase may be applied as long as they can generate traveling ultrasonic waves that propagate in the circumferential direction of the lens 4 (4').

The variable focus gel lens 1 of the first embodiment includes a substrate 2, but does not need to include a substrate 2 if the lens 4 can be held in the central opening of the ultrasonic transducer 3. The variable focus liquid lens 1' of 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 (bottom surface) of the liquid material 4a as well.

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, it only needs to be transparent to ultraviolet light, and if infrared light is used, it only needs to be transparent to infrared light. 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.

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, thereby 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 using the traveling waves.

1 Variable focus gel lens 1' Variable focus liquid lens 2 Substrate 3 Ultrasonic transducer 31 First electrode 31a First positive electrode 31b First negative electrode 32 Second electrode 32a Second positive electrode 32b Second negative electrode 33 Third electrode 33a Third positive electrode 33b Third negative electrode 34 Fourth electrode 34a Fourth positive electrode 34b Fourth negative electrode 4, 4' Lens 4a Liquid material 4b Film material 5 Drive unit 51 First drive unit 52 Second drive unit 53 Third drive unit 54 Fourth drive unit

Claims (9)

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
A variable focus lens characterized in that the electrical signals are applied 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. 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;
The variable focus lens of claim 1, characterized in that in the standing wave mode, the driving unit applies the electrical signals of the same phase to the N electrodes, generating 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. The N electrodes have the same shape,
2. The variable-focus lens according to claim 1, wherein 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, wherein the lens is made of a transparent viscoelastic gel. The lens is
A liquid material;
2. The variable-focus lens according to claim 1, further comprising a film material formed to cover the surface of the liquid material, the film material being deformed by the ultrasonic waves. 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,
A method for controlling a variable-focus lens, comprising a first step of applying the electrical signals of different phases and of which the phases increase or decrease in the circumferential direction to the N electrodes by the driving unit, generating a traveling wave of the ultrasonic waves that propagates 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 wave. A control method for a variable focus lens as described in claim 6, characterized in that it includes 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. 7. The method for controlling a variable-focus lens according to claim 6, wherein the lens is made of a transparent viscoelastic gel. The lens is
A liquid material;
and a film material formed to cover the surface of the liquid material, the film material being deformed by the ultrasonic waves.