Lens device and lens control method

Abstract

To provide a lens device that can exhibit a hand shake correction function without using a mechanical movable unit.SOLUTION: A lens device 1A includes a lens unit 2 and a control unit 6. The lens unit 2 includes: a plurality of ultrasonic vibrators 5 (Ch1 to Ch4) for vibrating and generating ultrasonic waves; and an elastic lens 4 which is deformed by an acoustic radiation force generated by ultrasonic waves. The control unit 6 makes the vibrating state of a part of the ultrasonic vibrators 5 (Ch1 to Ch4) different from the vibrating state of the other vibrators and eccentrically deforms the elastic lens 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lens apparatus and a lens control method. [Background technology]

[0002] The camera modules installed in general digital cameras and smartphones are equipped with a lens device. Conventional lens devices move and rotate the lens using mechanical moving parts such as actuators, thereby correcting changes in the lens position and tilt caused by external vibrations and achieving image stabilization during shooting.

[0003] However, the presence of mechanical moving parts causes problems such as an increase in the number of parts, an increase in the size of the device, and a decrease in earthquake resistance. Therefore, if a small, thin lens device with image stabilization function that does not have mechanical moving parts could be developed, it would lead to thinner camera modules and could also be expected to be applied to in-vehicle camera modules that require earthquake resistance and a long lifespan.

[0004] Incidentally, a known example of a lens device without a mechanically movable part is the variable-focus lens described in Patent Document 1. The variable-focus lens described in Patent Document 1 includes an annular ultrasonic transducer having a central opening, and a lens made of transparent viscoelastic gel placed in the central opening. In the variable-focus lens described in Patent Document 1, the height of the convex shape at the center of the lens increases as the voltage amplitude value of the electrical signal applied to the ultrasonic transducer increases, and therefore the focal length of the lens can be controlled by controlling the voltage amplitude value.

[0005] However, the variable-focus lens described in Patent Document 1 only lengthens or shortens the focal length of the lens, and is unable to move the focal position of the lens in the radial direction of the lens, and does not have an image stabilization function. For this reason, when performing image stabilization with the variable-focus lens described in Patent Document 1, a mechanically movable part is required to correct changes in the position and tilt of the lens, just like the lens device described above.

[0006] Patent Document 2 proposes a method of tilting the optical axis of an optical element directly fabricated in a predetermined area of ​​a substrate by displacing the predetermined area of ​​the substrate with a piezoelectric element. Patent Document 3 proposes a method of changing the focal length of a lens by deforming a piezoelectric material using the piezoelectric effect to deform the shape of the lens. However, the methods of Patent Documents 2 and 3 do not utilize the acoustic radiation force of ultrasound. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-61549 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-210968 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-243918 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and its object is to provide a lens device and a lens control method that can achieve image stabilization without using mechanically moving parts. [Means for solving the problem]

[0009] In order to solve the above problems, a lens device according to the present invention comprises: A lens device including a lens unit and a control unit, The lens portion is a plurality of ultrasonic transducers that vibrate to generate ultrasonic waves; an elastic lens whose shape is deformed by an acoustic radiation force generated by the ultrasonic waves; Equipped with The control unit The vibration state of some of the ultrasonic vibrators is made different from the vibration state of the other ultrasonic vibrators, thereby causing eccentric deformation of the elastic lens.

[0010] In the lens device, The control unit A normal control in which an electrical signal with a common voltage value is applied to the plurality of ultrasonic transducers; The ultrasonic transducer may be configured to perform voltage difference control by applying electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, thereby generating a voltage difference between at least one pair of electrical signals and changing the voltage difference.

[0011] In the lens device, It is preferable that the control unit performs the pre-voltage difference control in a state where the common frequency is set to a value different from the resonance frequency of the lens unit.

[0012] In the lens device, The control unit The ultrasonic transducers may be configured to apply electrical signals of different voltage values ​​and a common frequency to the ultrasonic transducers, and perform frequency control to change the common frequency while generating a voltage difference between at least one pair of electrical signals.

[0013] In the lens device, In the lens portion, flexural vibration is excited by the ultrasonic wave, The control unit During the frequency control, the common frequency can be changed in a frequency band in which the flexural vibration is in a state between the (n-1)th resonance mode (n is an integer of 2 or more) and the (n+1)th resonance mode.

[0014] In the lens device, The plurality of ultrasonic transducers are arranged around the elastic lens and include N ultrasonic transducers (N is an integer of 3 or more) divided into N in the circumferential direction, The control unit The N ultrasonic transducers may be configured to apply electrical signals of different phases and with phases that increase or decrease in the circumferential direction, thereby generating traveling waves of the ultrasonic waves that propagate in the circumferential direction of the elastic lens.

[0015] In order to solve the above problem, a lens control method according to the present invention includes: A lens control method for a lens device including a lens unit including a plurality of ultrasonic transducers that vibrate to generate ultrasonic waves and an elastic lens that changes shape by acoustic radiation force generated by the ultrasonic waves, and a control unit, The method is characterized in that it includes a step of causing the control unit to cause the vibration state of some of the plurality of ultrasonic vibrators to differ from the vibration state of other ultrasonic vibrators, thereby eccentrically deforming the elastic lens.

[0016] The lens control method includes: a normal control step in which the control unit applies an electrical signal with a common voltage value to the plurality of ultrasonic transducers; The method can be configured to include a voltage difference control step in which the control unit applies electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, thereby generating a voltage difference between at least one pair of electrical signals and changing the voltage difference.

[0017] The lens control method includes: In the voltage difference control step, it is preferable that the voltage difference is changed with the common frequency set to a value different from the resonance frequency of the lens portion.

[0018] The lens control method includes: The control unit can be configured to include a frequency control step in which electrical signals of different voltage values ​​and a common frequency are applied to the plurality of ultrasonic transducers, and the common frequency is changed while a voltage difference is generated between at least one pair of electrical signals.

[0019] In the lens control method, In the frequency control step, the control unit can be configured to change the common frequency in a frequency band in which the flexural vibration excited in the lens unit is in a state between an (n-1)th order resonance mode (n is an integer greater than or equal to 2) and an (n+1)th order resonance mode.

[0020] In the lens control method, The plurality of ultrasonic transducers are arranged around the elastic lens and include N ultrasonic transducers (N is an integer of 3 or more) divided into N in the circumferential direction, The method can be configured to include a step in which the control unit applies electrical signals of different phases and of phases that increase or decrease circumferentially to the N ultrasonic transducers, thereby generating traveling waves of the ultrasonic waves that propagate circumferentially around the elastic lens. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a lens device and a lens control method that are capable of achieving an image stabilization function without using any mechanically moving parts. [Brief explanation of the drawings]

[0022] [Figure 1] 1A and 1B are a plan view and a cross-sectional view, respectively, of a lens device according to a first embodiment of the present invention. [Figure 2] 10A and 10B are diagrams showing the vibration intensity of the upper surface of the substrate of the lens device according to the first embodiment, where FIG. 10A is a diagram showing the vibration intensity when the voltage values ​​are (0, 10, 10, 10) Vpp, FIG. 10B is a diagram showing the vibration intensity when the voltage values ​​are (10, 10, 10, 10) Vpp, and FIG. 10C is a diagram showing the vibration intensity when the voltage values ​​are (20, 10, 10, 10) Vpp. [Figure 3] FIG. 10 is a diagram showing the relationship between the voltage value and the movement distance of the maximum vibration position. [Figure 4] 1A and 1B are diagrams showing the vibration strength of the upper surface of the substrate of the lens device of the first embodiment, where (A) is a diagram when the frequency is 32.5 kHz, (B) is a diagram when the frequency is 40.5 kHz, and (C) is a diagram when the frequency is 48.5 kHz. [Figure 5]FIG. 10 is a diagram showing the relationship between frequency and the movement distance of the maximum vibration position. [Figure 6] 10A and 10B are plan and cross-sectional views of a lens device according to a second embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens apparatus and a lens control method according to embodiments of the present invention will be described below with reference to the accompanying drawings.

[0024] [First embodiment] (lens device) 1 shows a lens device 1A according to a first embodiment. The lens device 1A includes a lens unit 2 (a substrate 3, a lens 4, and an ultrasonic vibrator 5) and a control unit 6. The lens device 1A is used, for example, in a camera module mounted on a digital camera or a smartphone, or in a vehicle-mounted camera module.

[0025] The substrate 3 is a glass substrate formed in a disk shape, and has a diameter of 30 mm and a thickness of 1.1 mm.

[0026] The lens 4 is an elastic lens made of a transparent viscoelastic gel. 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, a silicone gel made of hydrophobic silica particles and silicone oil is used as the transparent viscoelastic gel.

[0027] The ultrasonic transducer 5 is a circular piezoelectric ultrasonic transducer having an inner diameter of 20 mm, an outer diameter of 30 mm, and a thickness of 1 mm. In this embodiment, the ultrasonic transducer 5 is divided into four parts in the circumferential direction, namely, a first ultrasonic transducer Ch1, a second ultrasonic transducer Ch2, a third ultrasonic transducer Ch3, and a fourth ultrasonic transducer Ch4.

[0028] The ultrasonic transducers Ch1 to Ch4 are arranged on the upper surface of the substrate 3, and form a central opening on the upper surface of the substrate 3. A lens 4 is arranged in the central opening. In this embodiment, the central axis of the lens 4 and the central axis of the substrate 3 coincide with each other.

[0029] Each of the ultrasonic transducers Ch1 to Ch4 includes a piezoelectric element 5a (lead zirconate titanate (PZT) in this embodiment) polarized in the thickness direction (Z direction), a positive electrode 5b, and a negative electrode 5c (all aluminum electrodes in this embodiment). The positive electrode 5b is formed on the upper surface of the piezoelectric element 5a. The negative electrode 5c is also formed on the lower surface (substrate 3 side) of the piezoelectric element 5a, extending from the upper surface to the side surface.

[0030] The gaps between the ultrasonic transducers Ch1 to Ch4 are filled with a sealing material (for example, a resin material such as epoxy resin) to prevent the gel that constitutes the lens 4 from leaking out through the gaps. In this embodiment, the piezoelectric element 5a is divided into four, but it is also possible to use an undivided circular piezoelectric element 5a, with the positive electrode 5b and negative electrode 5c of each ultrasonic transducer Ch1 to Ch4 formed on its upper surface as in FIG. 1(A). The negative electrode 5c on the lower surface side may or may not be divided into four.

[0031] The control unit 6 includes drive circuits DC1 to DC4 that apply electric signals (in this embodiment, AC voltage signals) to the ultrasonic transducers Ch1 to Ch4, and a control circuit that controls the phase, voltage value (in this embodiment, peak-to-peak voltage value), and frequency of the electric signals output by the drive circuits DC1 to DC4. The drive circuits DC1 to DC4 and the control circuit are configured with analog circuits and / or digital circuits.

[0032] The control unit 6 performs normal control to control the focal length of the lens 4 and correction control to decenter the lens 4, i.e., to move the focal point of the lens 4 in the radial direction (XY direction) of the lens 4.

[0033] During normal control, the control unit 6 applies an electrical signal with a common voltage, a common frequency, and a common phase to each of the ultrasonic transducers Ch1 to Ch4, which causes the ultrasonic transducers Ch1 to Ch4 to enter the same vibration state and generate ultrasonic waves of a predetermined frequency according to each electrical signal.

[0034] When ultrasonic waves generated by ultrasonic vibrators Ch1 to Ch4 propagate to substrate 3, flexural vibrations are excited in substrate 3, generating standing waves of flexural vibrations (acoustic standing waves). As a result, pressure due to the acoustic radiation force of the standing waves acts on the boundary between the upper surface of lens 4 and air, the boundary between the lower surface of lens 4 and substrate 3, and the boundary between the lower surface of substrate 3 and air. However, it is the acoustic radiation force of the standing waves acting on the boundary between the upper surface of lens 4 and air that contributes most to the deformation of lens 4. The pressure due to the acoustic radiation force is highest at the center of lens 4, causing the center to bulge and deforming lens 4 into a convex shape.

[0035] When the control unit 6 increases or decreases the common voltage value of the electrical signal, the pressure due to the acoustic radiation force of the standing wave changes, and the height of the convex shape at the center of the lens 4 also changes, changing the focal length of the lens 4. Therefore, by controlling the common voltage value of the electrical signal with the control unit 6, the focal length of the convex shape can be controlled.

[0036] During correction control, the control unit 6 performs voltage difference control and frequency control to make the vibration state of some of the ultrasonic transducers Ch1 to Ch4 different from the vibration state of the other transducers.

[0037] During voltage difference control, the control unit 6 applies electrical signals of different voltage values, a common frequency, and a common phase to the ultrasonic transducers Ch1 to Ch4, and changes the voltage difference while generating a voltage difference between the electrical signals. For example, the control unit 6 generates a voltage difference between the peak-to-peak voltage value of the electrical signal applied to some of the ultrasonic transducers Ch1 to Ch4 and the peak-to-peak voltage value of the electrical signal applied to the other transducers.

[0038] When ultrasonic transducers Ch1 to Ch4 generate ultrasonic waves while a voltage difference is being generated, non-axisymmetric flexural vibrations are excited in substrate 3 with respect to the central axis of substrate 3, generating standing waves of non-axisymmetric flexural vibrations (non-axisymmetric acoustic standing waves). Pressure due to non-axisymmetric acoustic radiation force acts mainly on the boundary surface between the upper surface of lens 4 and the air, and this pressure becomes higher at positions radially shifted from the central axis of lens 4, causing the positions shifted from the central axis to bulge and deforming the shape of lens 4.

[0039] When the control unit 6 increases or decreases the voltage difference between the electrical signals, the vibration distribution of the flexural vibration, i.e., the pressure distribution of the acoustic radiation force, moves in the radial direction of the lens 4. In other words, when the voltage difference is increased or decreased, the maximum protrusion position of the lens 4 moves closer or farther away from the central axis of the lens 4. Therefore, by controlling the voltage difference between the electrical signals, the control unit 6 can control the focal position of the lens 4 and thereby exhibit the image stabilization function.

[0040] Incidentally, when the frequency of the electrical signal is set to the same value as the resonant frequency of the lens unit 2, the flexural vibration excited in the substrate 3 enters a resonant state (resonant mode). In the resonant state, the vibration distribution is such that the maximum vibration position of the flexural vibration coincides with the central axis of the lens 4, and furthermore, the vibration amplitude of the maximum vibration position increases. Therefore, even if the control unit 6 performs voltage difference control, the axial symmetry of the flexural vibration is maintained (the vibration distribution of the flexural vibration does not move in the radial direction of the lens 4). For this reason, it is preferable that the control unit 6 sets the frequency of the electrical signal to a value different from the resonant frequency of the lens unit 2 and performs voltage difference control.

[0041] Even if the frequency of the electrical signal is set to the same value as the resonant frequency of the lens section 2 and voltage difference control is performed, it may be possible to move the vibration distribution of the flexural vibration in the radial direction of the lens 4, for example, by increasing the voltage difference between the electrical signals or by changing the configuration of the lens 4 (for example, by using a material with a lower viscosity).

[0042] During frequency control, the control unit 6 applies electrical signals of different voltage values, a common frequency and a common phase to the ultrasonic transducers Ch1 to Ch4, and changes the frequency while generating a voltage difference between the electrical signals.

[0043] When the frequency of the electrical signal is set to the same value as the resonance frequency of the lens unit 2, as described above, the maximum vibration position of the flexural vibration coincides with the central axis of the lens 4. When the frequency of the electrical signal is reduced below the resonance frequency of the lens unit 2, the maximum vibration position of the flexural vibration moves away from the central axis of the lens 4 to one side in the radial direction. When the frequency of the electrical signal is increased above the resonance frequency of the lens unit 2, the maximum vibration position of the flexural vibration moves away from the central axis of the lens 4 to the other side in the radial direction.

[0044] If the flexural vibration occurring when the frequency of the electrical signal is set to the same value as the resonance frequency of the lens unit 2 is defined as the nth resonance mode flexural vibration, the flexural vibration begins to transition to the (n-1)th resonance mode as the frequency of the electrical signal is lowered, and begins to transition to the (n+1)th resonance mode as the frequency of the electrical signal is increased. The further away from the nth resonance mode, the smaller the influence of the resonance, while the closer to the (n-1)th or (n+1)th resonance mode, the greater the influence of the resonance. Affected by the resonance due to such a transition of the resonance mode, the vibration distribution of the flexural vibration moves in the radial direction of the lens 4.

[0045] When the control unit 6 changes the frequency of the electrical signal near the resonance frequency of the lens unit 2, the vibration distribution of the flexural vibration, i.e., the pressure distribution of the acoustic radiation force, moves in the radial direction of the lens 4, and therefore the maximum protrusion position of the lens 4 also moves in the radial direction. Therefore, by controlling the frequency of the electrical signal, the control unit 6 can control the focal position of the lens 4 and thereby exhibit the image stabilization function.

[0046] When the frequency of the electrical signal is decreased (or increased) below the resonance frequency of the lens unit 2, which side in the radial direction of the lens 4 the maximum vibration position of the flexural vibration moves to varies depending on the configuration of the lens unit 2, the voltage difference between the electrical signals, etc. Therefore, it is preferable to create in advance data indicating the relationship between the frequency of the electrical signal, the voltage difference between the electrical signals, and the moving direction of the maximum vibration position of the flexural vibration, and store this data in the control unit 6. This allows the control unit 6 to perform frequency control while referring to this data.

[0047] (Lens control method) The lens control method according to the first embodiment is a method for controlling the lens device 1A. That is, the lens control method includes a first step in which the control unit 6 performs normal control, a second step in which the control unit 6 performs voltage difference control, and a third step in which the control unit 6 performs frequency control. In the lens control method, the steps may be performed in any order, or multiple steps may be performed simultaneously, although this may complicate the control. The normal control, voltage difference control, and frequency control have been described above, so they will not be described here.

[0048] (Evaluation experiment) Next, an evaluation experiment of the lens device 1A and the lens control method thereof will be described.

[0049] Figure 2 is an image showing the vibration intensity distribution in a specified range from the center of the top surface of substrate 3, measured using a laser Doppler vibrometer (LDV). In Figure 2, the measurement was performed with lens 4 removed to avoid interference between the top surface of lens 4 and the laser light reflected from the top surface of substrate 3.

[0050] The peak-to-peak voltage values ​​of the electrical signals applied to the ultrasonic transducers Ch1 to Ch4 are (V1, V2, V3, V4) Vpp. Figure 2(A) shows measurements at (0, 10, 10, 10) Vpp, Figure 2(B) shows measurements at (10, 10, 10, 10) Vpp, and Figure 2(C) shows measurements at (20, 10, 10, 10) Vpp. The frequency of the electrical signals applied to the ultrasonic transducers Ch1 to Ch4 is set to 36.5 kHz, which is different from the resonant frequency (40.5 kHz) of the lens unit 2 without lens 4.

[0051] FIG. 3 is a diagram showing the relationship between the peak-to-peak voltage V1 [Vpp] applied to the ultrasonic transducer Ch1 and the movement distance from the central axis of the substrate 3 (=the central axis of the lens 4) to the maximum vibration position.

[0052] From Figures 2 and 3, it can be seen that when V1 = 10 [Vpp], the maximum vibration position coincides with the central axis of substrate 3, when V1 > 10 [Vpp], the maximum vibration position moves in a direction closer to ultrasonic transducer Ch1, and when V1 < 10 [Vpp], the maximum vibration position moves in a direction closer to ultrasonic transducer Ch3.

[0053] The maximum vibration position of the substrate 3 corresponds to the position where the pressure of the acoustic radiation force is maximum when the lens 4 is present, and corresponds to the maximum protrusion position of the lens 4. Therefore, from Figures 2 and 3, it can be seen that the focal position of the lens 4 can be controlled by controlling the voltage difference between the electrical signals applied by the control unit 6 to the ultrasonic transducers Ch1 to Ch4.

[0054] Figure 4 is an image showing the vibration intensity distribution measured in the same way as Figure 2. In Figure 4, the peak-to-peak voltage value of the electrical signal applied to the ultrasonic transducers Ch1 to Ch4 was fixed at (0, 10, 10, 10) Vpp, and only the frequency was varied for measurements. Figure 4(A) was measured at a frequency of 32.5 kHz, Figure 4(B) was measured at a frequency of 40.5 kHz (= the resonant frequency of the lens unit 2 without lens 4), and Figure 4(C) was measured at a frequency of 48.5 kHz.

[0055] In Fig. 4(B), the flexural vibration excited in the substrate 3 is in a resonant state of the second-order resonance mode, while in Fig. 4(A), it is in a transition state between the first-order resonance mode and the second-order resonance mode, and in Fig. 4(C), it is in a transition state between the second-order resonance mode and the third-order resonance mode.

[0056] FIG. 5 is a diagram showing the relationship between the frequency of the electric signal applied to the ultrasonic transducers Ch1 to Ch4 and the moving distance from the central axis of the substrate 3 (=the central axis of the lens 4) to the maximum vibration position.

[0057] From Figures 4 and 5, it can be seen that when the frequency of the electrical signal is set to the resonant frequency of 40.5 kHz, the maximum vibration position coincides with the central axis of substrate 3, and when the frequency of the electrical signal is lower than the resonant frequency, the maximum vibration position moves in a direction closer to ultrasonic transducer Ch1, and when the frequency of the electrical signal is higher than the resonant frequency, the maximum vibration position moves in a direction closer to ultrasonic transducer Ch3.

[0058] 4 and 5, it can be seen that the focal position of the lens 4 can be controlled by controlling the frequency of the electrical signals applied to the ultrasonic transducers Ch1 to Ch4 by the control unit 6. In this embodiment, it is preferable to change the frequency in a frequency band where the flexural vibration is in a state between the first and third resonance modes (i.e., a frequency band before and after the second resonance mode).

[0059] Furthermore, when the focal position of lens 4 is moved from the central axis of lens 4 by voltage difference control, the focal position of lens 4 can be returned to the central axis of lens 4 by setting the frequency of the electrical signal to the resonant frequency of lens section 2 by frequency control, even when a voltage difference is generated between the electrical signals applied to ultrasonic vibrators Ch1 to Ch4.

[0060] [Second embodiment] (lens device) 6 shows a lens device 1B according to a second embodiment. Lens device 1B is the same as in the first embodiment except that it includes a lens 4' instead of lens 4 and a control unit 6' instead of control unit 6.

[0061] 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 of a liquid material and a film material is called a liquid lens (corresponding to the "elastic lens" of the present invention).

[0062] 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 vibrator 5.

[0063] 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.

[0064] In this embodiment, the membrane material 4b is formed only on the upper surface of the liquid material 4a so as to have a predetermined tension. However, it may be formed on the side (outer peripheral surface) of the liquid material 4a in addition to the upper surface of the liquid material 4a, or on the lower surface of the liquid material 4a. Furthermore, while the thickness of the membrane material 4b is uniform, it may also be non-uniform. For example, the thickness of the membrane material 4b may be different between the center and the periphery. Furthermore, when no electrical signal is applied to the ultrasonic transducer 5, the membrane material 4b has a flat shape, but it may also have a concave or convex curved shape.

[0065] The control unit 6' has the same configuration as the control unit 6, and performs the normal control (first normal control) and correction control (first correction control) performed by the control unit 6, and further performs second normal control and second correction control. The first normal control and first correction control are controls that generate standing waves of flexural vibration, while the second normal control and second correction control are controls that generate traveling waves of flexural vibration.

[0066] During second normal control, the control unit 6' applies to the ultrasonic transducers Ch1 to Ch4 electrical signals of a common voltage value and a common frequency, with the phases shifted by 90° (increased by 90°) in the circumferential direction. That is, with respect to the electrical signal applied to ultrasonic transducer Ch1 by drive circuit DC1, the electrical signal applied to ultrasonic transducer Ch2 by drive circuit DC2 has a phase difference of 90°, the electrical signal applied to ultrasonic transducer Ch3 by drive circuit DC3 has a phase difference of 180°, and the electrical signal applied to ultrasonic transducer Ch4 by drive circuit DC4 has a phase difference of 270°. The ultrasonic transducers Ch1 to Ch4 generate ultrasonic waves according to each electrical signal.

[0067] When ultrasonic waves generated by the ultrasonic transducers Ch1 to Ch4 propagate to the substrate 3, flexural vibrations are excited in the substrate 3, generating traveling waves of flexural vibration (acoustic traveling waves) that propagate in the circumferential direction. As a result, pressure due to the acoustic radiation force of the traveling waves acts on the interface between the upper surface of the film material 4b and the air, the interface between the lower surface of the film material 4b and the upper surface of the liquid material 4a, the interface between the lower surface of the liquid material 4a and the upper surface of the substrate 3, and the interface between the lower surface of the substrate 3 and the air. However, it is the acoustic radiation force of the traveling waves acting on the interface between the upper surface of the film material 4b and the air that contributes most to the deformation of the lens 4'. The pressure due to this acoustic radiation force is higher at the periphery of the upper surface of the film material 4b, causing the periphery of the film material 4b to rise. As the periphery of the film material 4b rises, the center of the film material 4b sinks (the thickness of the periphery of the liquid material 4a increases, while the thickness of the center of the liquid material 4a decreases), and the lens 4' deforms into a concave shape.

[0068] Furthermore, increasing or decreasing the common voltage value of the electrical signal changes the pressure due to the acoustic radiation force of the traveling wave, which 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 control unit 6', the focal length of the concave shape can be controlled.

[0069] During the second correction control, the control unit 6' performs voltage difference control and frequency control to make the vibration state of some of the ultrasonic transducers Ch1 to Ch4 different from the vibration state of the other transducers. The voltage difference control and frequency control during the second correction control will be described below.

[0070] During voltage difference control, the control unit 6' applies electrical signals of different voltage values, the same frequency, and phases shifted by 90° to the ultrasonic transducers Ch1 to Ch4, and changes the voltage difference while generating a voltage difference between the electrical signals. For example, the control unit 6' generates a voltage difference between the peak-to-peak voltage value of the electrical signal applied to some of the ultrasonic transducers Ch1 to Ch4 and the peak-to-peak voltage value of the electrical signal applied to the other transducers.

[0071] When the ultrasonic transducers Ch1 to Ch4 generate ultrasonic waves while a voltage difference is being generated, flexural vibration is excited in the substrate 3, generating traveling waves of flexural vibration (acoustic traveling waves) that propagate in the circumferential direction. The vibration distribution of the traveling waves of flexural vibration is shifted in the radial direction of the substrate 3 compared to the traveling waves during second normal control. When such traveling waves are generated, pressure due to acoustic radiation force acts mainly on the boundary surface between the upper surface of the lens 4' and the air, and this pressure is shifted in the radial direction of the lens 4' compared to the second normal control. As a result, the concave shape of the lens 4' is also shifted in the radial direction.

[0072] When the control unit 6' changes the voltage difference between the electrical signals applied to the ultrasonic transducers Ch1 to Ch4, the vibration distribution of the flexural vibration, i.e., the pressure distribution of the acoustic radiation force, moves in the radial direction of the lens 4', and the concave shape of the lens 4' also moves in the radial direction. Therefore, by controlling the voltage difference between the electrical signals, the control unit 6' can control the focal position of the lens 4' and thereby exhibit the image stabilization function.

[0073] During frequency control, the control unit 6' changes the common frequency of the electrical signals applied to the ultrasonic transducers Ch1 to Ch4 while generating a voltage difference between the electrical signals applied to the ultrasonic transducers Ch1 to Ch4. The principle is the same as in the first embodiment, so a description thereof will be omitted here.

[0074] When the control unit 6' changes the frequency of the electrical signals applied to the ultrasonic transducers Ch1 to Ch4, the vibration distribution of the flexural vibration, i.e., the pressure distribution of the acoustic radiation force, moves in the radial direction of the lens 4', and therefore the concave shape of the lens 4' also moves in the radial direction. Therefore, by controlling the frequency of the electrical signals, the control unit 6' can control the focal position of the lens 4' and thereby achieve the image stabilization function.

[0075] (Lens control method) The lens control method according to the second embodiment is a control method for the lens device 1B. That is, the lens control method includes a first step in which the control unit 6′ performs first normal control, a second step in which the control unit 6′ performs voltage difference control for first correction control, a third step in which the control unit 6′ performs frequency control for the first correction control, a fourth step in which the control unit 6′ performs second normal control, a fifth step in which the control unit 6′ performs voltage difference control for second correction control, and a sixth step in which the control unit 6′ performs frequency control for the second correction control.

[0076] In this lens control method, the steps may be performed in any order, or multiple steps may be performed simultaneously, although this may complicate the control. Each control has been described above, so a detailed description is omitted here.

[0077] [Variations] Although the lens apparatus and lens control method according to the present invention have been described above as embodiments, the present invention is not limited to the above embodiments.

[0078] The lens device according to the present invention is a lens device comprising a lens unit and a control unit, wherein the lens unit comprises a plurality of ultrasonic vibrators that vibrate to generate ultrasonic waves, and an elastic lens that deforms in shape by the acoustic radiation force generated by the ultrasonic waves, and the control unit can be configured as appropriate as long as it causes the vibration state of some of the plurality of ultrasonic vibrators to differ from the vibration state of the other ultrasonic vibrators, thereby shifting the pressure distribution of the acoustic radiation force in the radial direction of the elastic lens, thereby eccentrically deforming the elastic lens.

[0079] At least two ultrasonic vibrators are required to correct camera shake in the vertical direction, for example.

[0080] In the first embodiment, only the peak-to-peak voltage value of the electrical signal applied to the ultrasonic transducer Ch1 is changed in the voltage difference control, but as long as a voltage difference occurs between at least one pair of electrical signals, the peak-to-peak voltage values ​​of the electrical signals applied to the other ultrasonic transducers Ch2 to Ch4 may be changed, or the peak-to-peak voltage values ​​of the electrical signals applied to all ultrasonic transducers Ch1 to Ch4 may be changed.

[0081] The lens device 1A according to the first embodiment includes a substrate 3, but the substrate 3 need not be provided as long as the lens 4 can be held in the central opening of the ultrasonic vibrator 5. The lens device 1B according to the second embodiment can also omit the substrate 3, but in that case, it is necessary to form a film material 4b also on the underside of the liquid material 4a. If the substrate 3 is provided, it is sufficient that the substrate 3 is configured to excite flexural vibration.

[0082] 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.

[0083] In the first embodiment, the lens 4' of the second embodiment may be used, and in the second embodiment, the lens 4 of the first embodiment may be used.

[0084] In the second embodiment, the control unit 6' applies electrical signals to the ultrasonic transducers Ch1 to Ch4 with the phase increased by 90° in the circumferential direction, but electrical signals of any phase may be applied as long as they can generate traveling waves of ultrasonic waves that propagate in the circumferential direction of the lens 4'.

[0085] The lens control method of the present invention is a lens control method for a lens device that includes a lens unit having a plurality of ultrasonic vibrators that vibrate to generate ultrasonic waves and an elastic lens that deforms its shape by the acoustic radiation force generated by the ultrasonic waves, and a control unit, and the configuration can be modified as appropriate as long as it includes a step in which the control unit causes the vibration state of some of the plurality of ultrasonic vibrators to differ from the vibration state of the other ultrasonic vibrators, thereby eccentrically deforming the elastic lens. [Explanation of symbols]

[0086] 1A, 1B lens device 2 Lens section 3. Circuit Board 4, 4' lens 4a liquid material 4b Membrane material 5 Ultrasonic transducer 5a Piezoelectric element 5b Positive electrode 5c negative electrode 6, 6' control section

Claims

1. A lens device comprising a lens unit and a control unit, The lens portion is a plurality of ultrasonic transducers that vibrate to generate ultrasonic waves; an elastic lens whose shape is deformed by an acoustic radiation force generated by the ultrasonic waves; Equipped with The control unit A normal control in which an electrical signal with a common voltage value is applied to the plurality of ultrasonic transducers; voltage difference control, which applies electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, generates a voltage difference between at least one pair of electrical signals, and changes the voltage difference to eccentrically deform the elastic lens; The control unit performs the voltage difference control in a state where the common frequency is set to a value different from the resonance frequency of the lens unit. A lens device characterized by:

2. A lens device comprising a lens unit and a control unit, The lens portion is a plurality of ultrasonic transducers that vibrate to generate ultrasonic waves; an elastic lens whose shape is deformed by an acoustic radiation force generated by the ultrasonic waves; Equipped with The control unit A normal control in which an electrical signal with a common voltage value is applied to the plurality of ultrasonic transducers; voltage difference control in which electrical signals of different voltage values ​​and a common frequency are applied to the plurality of ultrasonic transducers to generate a voltage difference between at least one pair of electrical signals and change the voltage difference to eccentrically deform the elastic lens; and applying electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, and changing the common frequency while generating a voltage difference between at least one pair of electrical signals, thereby performing frequency control to eccentrically deform the elastic lens. A lens device characterized by:

3. In the lens portion, flexural vibration is excited by the ultrasonic wave, The control unit During the frequency control, the common frequency is changed in a frequency band in which the flexural vibration is in a state between an (n-1)th resonance mode (n is an integer of 2 or more) and an (n+1)th resonance mode.

3. The lens device according to claim 2.

4. The plurality of ultrasonic transducers are arranged around the elastic lens and include N ultrasonic transducers (N is an integer of 3 or more) divided into N in the circumferential direction, The control unit Electric signals having different phases and phases that increase or decrease in the circumferential direction are applied to the N ultrasonic transducers, generating traveling waves of the ultrasonic waves that propagate in the circumferential direction of the elastic lens.

4. The lens device according to claim 1, wherein the lens device is a lens unit.

5. A lens control method for a lens device comprising: a lens unit including a plurality of ultrasonic vibrators that vibrate to generate ultrasonic waves and an elastic lens that deforms its shape by an acoustic radiation force generated by the ultrasonic waves; and a control unit, a normal control step in which the control unit applies an electrical signal with a common voltage value to the plurality of ultrasonic transducers; a voltage difference control step of applying, by the control unit, electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, to generate a voltage difference between at least one pair of electrical signals, thereby changing the voltage difference and thereby eccentrically deforming the elastic lens, In the voltage difference control step, the voltage difference is changed while the common frequency is set to a value different from the resonance frequency of the lens portion. A lens control method comprising:

6. A lens control method for a lens device comprising: a lens unit including a plurality of ultrasonic vibrators that vibrate to generate ultrasonic waves and an elastic lens that deforms its shape by an acoustic radiation force generated by the ultrasonic waves; and a control unit, a normal control step in which the control unit applies an electrical signal with a common voltage value to the plurality of ultrasonic transducers; a voltage difference control step in which the control unit applies electrical signals having different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, and generates a voltage difference between at least one pair of electrical signals, thereby changing the voltage difference and eccentrically deforming the elastic lens; and a frequency control step of applying, by the control unit, electrical signals of different voltage values ​​and a common frequency to the plurality of ultrasonic transducers, and changing the common frequency while generating a voltage difference between at least one pair of electrical signals, thereby eccentrically deforming the elastic lens. A lens control method comprising:

7. In the frequency control step, the control unit changes the common frequency in a frequency band in which the flexural vibration excited in the lens unit is in a state between an (n-1)th order resonance mode (n is an integer of 2 or more) and an (n+1)th order resonance mode.

7. The lens control method according to claim 6.

8. The plurality of ultrasonic transducers are arranged around the elastic lens and include N ultrasonic transducers (N is an integer of 3 or more) divided into N in the circumferential direction, The control unit applies, to the N ultrasonic transducers, electrical signals of different phases and phases that increase or decrease in the circumferential direction, to generate traveling waves of the ultrasonic waves that propagate in the circumferential direction of the elastic lens.

8. The lens control method according to claim 5, wherein:

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