JP2001249262A - OPTICAL ELEMENT CAPACITANCE DETECTOR AND OPTICAL DEVICE WITH CAPACITANCE DETECTOR - Google Patents

Abstract

(57) [Problem] To be able to accurately detect a capacitance corresponding to a change in the amount of deformation of a varifocal lens as an optical element with a simple configuration without providing a capacitance detection electrode, Provided are a capacitance detection device capable of accurately controlling various operations of an optical device based on a detection result, and an optical device including the capacitance detection device. An optical element whose optical characteristics change due to a change in an interface shape due to a voltage applied between a first electrode and a second electrode provided in a container, and a predetermined electrode provided to change the interface shape. Power supply means for applying a voltage, control means for controlling the applied voltage, and capacitance means for detecting a capacitance between the first electrode and the second electrode, wherein the capacitance element detects the optical element. And an optical device including the capacitance detecting device for detecting a capacitance corresponding to the change in the interface shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance detecting device for an optical element and an optical device provided with the capacitance detecting device, for example, having a capacitor structure by measuring capacitance and applying a voltage to the device. An element whose capacitance is variable,
For example, the present invention relates to a capacitance detecting device of an optical element that detects a capacitance corresponding to a deformation amount of a variable focus lens using an electrocapillary phenomenon (electrowetting), and an optical device including the capacitance detecting device.

[0002]

2. Description of the Related Art Among optical systems incorporated in optical devices such as still cameras and video cameras, most of which can change the focal length, most of them are lenses (or lens groups) constituting the optical system. The focal length of the entire optical system is changed by mechanically moving the unit in the optical axis direction. Among them, various methods for detecting the changed focal length have been proposed. For example, as shown in Japanese Patent Application Laid-Open No. 05-150151, when a variable condenser is formed by providing electrodes in a fixed barrel and a movable barrel so as to face each other and in a non-contact manner, the fixed barrel and the movable barrel (that is, the movable lens) become It is known that focusing on the fact that the capacitance of the capacitor changes due to relative movement, and the focal length after movement is detected by detecting the position of the lens based on the change in the capacitance.

In Japanese Patent Application Laid-Open No. H11-133210, a potential difference is applied between the first electrode and the conductive elastic plate to generate a suction force due to Coulomb force, thereby narrowing the interval between the two. With the volume of the transparent liquid rejected from the distance between the two, the central portion of the transparent elastic plate can be deformed by protruding backward against the transparent liquid.
Then, a convex lens is formed by the transparent elastic plate deformed into a convex shape, the transparent plate, and the transparent liquid filling the space between the transparent plate and the transparent plate. By adjusting the potential difference, the power of this convex lens is adjusted to form a varifocal lens. are doing. A separate capacitance detection electrode is provided on the first electrode and the conductive elastic plate, which is a control means of the variable focus lens, and the focal length is measured by detecting the capacitance between these electrodes. I have. In addition, an applied voltage for driving the varifocal lens is controlled based on the detected capacitance.

On the other hand, a variable focus lens using the electrocapillary phenomenon (electrowetting) is disclosed in WO99 / 184.
56. By using this technique, electric energy can be directly used for changing the shape of the lens formed by the interface between the first liquid and the second liquid, so that the lens is made to have a variable focus without mechanically moving. Things become possible.

[0005]

However, the above-mentioned prior art has problems in the following points.
For example, in the above-mentioned Japanese Patent Application Laid-Open No. 05-150151, it is necessary to provide an electrode for each of the fixed lens barrel and the movable cylinder in order to form a focal length, that is, a capacitance, so that the space is required and the size is small. However, there are drawbacks in that the production is difficult and that the production cost is increased. In JP-A-11-133210, a capacitance detection electrode is separately provided on the first electrode serving as a drive electrode of the optical element and the conductive elastic plate in order to detect the capacitance. Thus, a variable capacitor is formed, and the capacitance at each time is detected by focusing on the fact that the distance between the first electrode and the conductive elastic plate changes. In this configuration, since the distance between the first electrode and the conductive elastic plate is small, it is difficult to detect a change in capacitance. In addition, the above-mentioned WO99
/ 18456 discloses a technique for varying the optical power, but does not disclose a description of detecting a focal length based on capacitance, and discloses nothing about a drive sequence when incorporated in an optical device. Absent.

Accordingly, the present invention solves the above-mentioned problems in the prior art, and provides a capacitance corresponding to a change in variable focus of an optical element utilizing an electrocapillary phenomenon without providing a capacitance detection electrode. Provided are a capacitance detection device that can accurately detect with a simple configuration and that can accurately control various operations of the optical device based on the detection result, and an optical device including the capacitance detection device. It is intended to do so.

[0007]

In order to achieve the above object, the present invention provides a capacitance detecting device for an optical element and a capacitance detecting device configured as in the following (1) to (14). The present invention provides an optical device provided with the optical device. (1) A conductive or polar first liquid and a second liquid which are not mixed with the first liquid are hermetically sealed in a container with their interfaces having a predetermined shape, An optical element whose optical characteristics change due to a change in the interface shape due to a voltage applied between the first electrode and the second electrode provided in the container; and applying a predetermined voltage to the electrode to change the interface shape Power supply means, a control means for controlling the applied voltage, and a capacitance detection means for detecting a capacitance between the first electrode and the second electrode, wherein the capacitance detection means detects the capacitance of the optical element. A capacitance detecting device for an optical element, which detects a capacitance corresponding to a change in an interface shape. (2) A conductive or polar first liquid and a second liquid which are not mixed with the first liquid are hermetically sealed in a container with their interfaces having a predetermined shape, An optical element whose optical characteristics change due to a change in the interface shape due to a voltage applied between the first electrode and the second electrode provided in the container; and applying a predetermined voltage to the electrode to change the shape of the interface. An optical device comprising: a power supply unit for applying; a control unit for controlling the applied voltage; and a capacitance detection unit for detecting a capacitance between the first electrode and the second electrode. (3) The optical device according to (2), wherein the focal length is controlled based on the capacitance detected by the capacitance detection unit. (4) The optical device according to claim 2, wherein the capacitance detected by the capacitance detection unit is displayed on a display unit. (5) determining whether or not the detected value of the capacitance is within an allowable range based on the capacitance detected by the capacitance detecting means;
The optical device according to (2), wherein a voltage applied to the optical element is controlled. (6) It has an imaging optical system and an image recording unit, and determines whether or not the detected value of the capacitance is within an allowable range based on the capacitance detected by the capacitance detecting unit, and performs image pickup. The optical device according to the above (2), which controls a recording operation. (7) The first liquid and the second liquid have substantially different refractive indices, and are sealed in the container with their interface in a large R shape when the voltage is not applied. The optical device according to any one of the above (1) to (6). (8) The first liquid and the second liquid have substantially the same refractive index, and are sealed in the container in a state where their interfaces have a substantially flat shape when the voltage is not applied. The optical device according to any one of the above (1) to (6), wherein (9) The electrode comprises a first electrode and a second electrode insulated from the first liquid, and the first electrode is provided so as to be electrically connected to the first liquid. The optical device according to any one of the above (1) to (8), wherein (10) The optical device according to (9), wherein the first electrode is provided so as to be electrically connected to the first liquid from a side surface of the container. (11) The optical device according to (9), wherein the first electrode is provided so as to conduct from the upper surface side of the container to the first liquid. (12) The optical device according to (9), wherein the second electrode is provided on a side surface of the container. (13) The second electrode is a ring-shaped electrode,
The optical device according to (12), wherein the optical device is arranged so as to surround the second liquid. (14) The optical device according to the above (13), wherein the ring-shaped electrode has a shape whose inner diameter gradually increases in a light beam emission direction.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention,
By applying the above configuration, the capacitance detecting means for detecting the capacitance between the first electrode and the second electrode of the optical element,
By detecting the capacitance corresponding to the change in the interface shape of the optical element, it is possible to integrate the drive electrode and the capacitance detection electrode, without providing a separate capacitance detection electrode, The capacitance can be accurately detected with a simple configuration. In addition, by incorporating the capacitance detecting device of the above-described optical element into the optical device and performing a predetermined operation in the optical device based on the capacitance detected by the capacitance detecting device. In addition, when a defect occurs in the optical element, the correction can be easily performed. In addition, the predetermined operation may be configured to control the focal length, or display the detection result of the detected capacitance on a display of information on an optical system included in the optical device. With such a configuration, it is possible to easily detect a failure or the like. Further, by configuring means for determining whether or not the capacitance detection value is within the optically allowable range, by controlling the voltage applied to the optical element, it is possible to obtain desired optical characteristics,
Alternatively, it is possible to prohibit photographing when the detected value of the capacitance is out of the range, thereby preventing extra recording.

[0009]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. [Embodiment 1] FIGS. 1 to 8 are diagrams relating to Embodiment 1 of the present invention, and FIGS. 1 and 2 are cross-sectional views showing the configuration of an optical element of this embodiment. The configuration of the optical element of this embodiment and a method of forming the optical element will be described with reference to FIGS. Reference numeral 101 denotes the entire optical element of the present invention, and reference numeral 102 denotes a transparent acrylic transparent substrate provided with a concave portion at the center. Transparent substrate 102
The transparent electrode made of indium tin oxide (IT
O) 103 is formed by sputtering, and an insulating layer 104 made of transparent acrylic is provided on the upper surface thereof in close contact therewith.
The insulating layer 104 is formed by dropping a replica resin at the center of the transparent electrode 103, pressing the replica resin with a glass plate to smooth the surface, and then performing UV irradiation and curing. Insulating layer 10
A cylindrical container 105 having a light-shielding property is adhesively fixed on the upper surface of the cover 4, and a transparent acrylic cover plate 1 is mounted on the upper surface of the cylindrical container 105.
06 is adhered and fixed, and the upper surface thereof has a diameter D at the center.
An aperture plate 107 having three openings is arranged. In the above configuration, the insulating layer 104, the container 105, and the upper cover 1
A housing having a closed space of a predetermined volume surrounded by 06, that is, a liquid chamber is formed. The wall surface of the liquid chamber is subjected to the following surface treatment.

First, a diameter D
A water-repellent treatment agent is applied within the range of 1 to form a water-repellent film 111. As the water repellent, a fluorine compound or the like is preferable. Further, a hydrophilic treatment agent is applied to a region outside the diameter D1 on the upper surface of the insulating layer 104 to form a hydrophilic film 112. As the hydrophilic agent, a surfactant, a hydrophilic polymer and the like are preferable. On the other hand, on the lower surface of the cover plate 106, a hydrophilic treatment is performed within the range of the diameter D2, and a hydrophilic film 113 having the same properties as the hydrophilic film 112 is formed. All the components described so far have rotationally symmetric shapes with respect to the optical axis 123. Further, a hole is formed in a part of the container 105, and a rod-like electrode 125 is inserted therein, and sealed with an adhesive to maintain the hermeticity of the liquid chamber. A power supply means 126 is connected to the transparent electrode 103 and the rod-shaped electrode 125, and a predetermined voltage can be applied between both electrodes by operating the switch 127.

The liquid chamber having the above configuration is filled with the following two types of liquids. First, the water-repellent film 11 on the insulating layer 104
A predetermined amount of the second liquid 122 is dropped on the first liquid 122. The second liquid 122 is a colorless and transparent silicone oil having a specific gravity of 1.06 and a refractive index of 1.49 at room temperature. On the other hand, the remaining space in the liquid chamber is filled with the first liquid 121. The first liquid 121 is obtained by mixing water and ethyl alcohol at a predetermined ratio, and further adding a predetermined amount of electrolyte such as salt, and has a specific gravity of 1.06 and a refractive index of 1.38 at room temperature.
Electrolyte solution. That is, as the first and second liquids, liquids having the same specific gravity and being insoluble in each other are selected. Therefore, both liquids form an interface 124, and each liquid exists independently without being mixed.

Next, the shape of the interface will be described. First, when no voltage is applied to the first liquid, the interface 1
The shape of 24 is the interfacial tension between the two liquids, the interfacial tension between the first liquid and the water-repellent film 111 or the hydrophilic film 112 on the insulating layer 104, the second liquid and the water-repellent film 111 on the insulating layer 104 or It is determined by the interfacial tension with the hydrophilic film 112 and the volume of the second liquid. In this embodiment, the material is selected so that the interfacial tension between the silicone oil, which is the material of the second liquid 122, and the water-repellent film 111 is relatively small.
That is, since the wettability between both materials is high, the second liquid 12
The outer edge of the lenticular droplet formed by 2 has a tendency to spread,
It is stabilized when the outer edge coincides with the application area of the water-repellent film 111. That is, the diameter A1 of the lens bottom surface formed by the second liquid is equal to the diameter D1 of the water-repellent film 111. On the other hand, since the specific gravity of both liquids is equal as described above, gravity does not act.
Therefore, the interface 124 becomes a spherical surface, and its radius of curvature and height h1 are determined by the volume of the second liquid 122. The thickness of the first liquid on the optical axis is t1.

Further, in the above configuration, the optical element 101
Has a capacitor structure in which the first liquid 121 serves as one electrode and the transparent electrode 103 serves as the other electrode.
Here, since the water-repellent film 111 and the hydrophilic film 112 are extremely thin, their existence is ignored, and the first liquid 121 is applied to the insulating layer 1.
Assuming that the area of the portion in contact with 04 is S1 and the thickness of the insulating layer 104 is d, the optical element 101 is a capacitor having the electrode plate area S1 and the gap d between the electrodes. Changes, the capacitance of the capacitor also changes.

Here, when the switch 127 is closed and a voltage is applied to the first liquid 121, the interfacial tension between the first liquid 121 and the hydrophilic film 112 is reduced by an electrocapillary phenomenon, and the first liquid 121 is turned off. The liquid crosses the boundary between the hydrophilic film 112 and the hydrophobic film 122 and enters the hydrophobic film 122. as a result,
As shown in FIG. 2, the diameter of the bottom surface of the lens formed by the second liquid decreases from A1 to A2, the height increases from h1 to h2,
The area increases from S1 to S2. The thickness of the first liquid on the optical axis is t2. Thus, the first liquid 121
By applying a voltage to the liquid, the balance of the interfacial tension of the two liquids changes, and the shape of the interface between the two liquids changes.

Further, since the first and second liquids have different refractive indices, the power as an optical lens is given, so that the optical element 101 is
A varifocal lens is formed by the shape change. Further, the optical element 101 is equivalent in energy to a capacitor, and the capacitance of the optical element 101 is such that the first liquid 121 is the insulating layer 104.
Is proportional to the area of contact. Therefore, the capacitance of the optical element 101 changes due to a change in the shape of the interface 124. The higher the applied voltage, the larger the capacitance. Next, the configuration of a power supply unit used in the present embodiment and a method of forming the power supply unit will be described with reference to FIGS.

Reference numeral 130 denotes a central processing unit (hereinafter abbreviated as CPU) for controlling the overall operation of an optical device 150 described later.
ROM, RAM, EEPROM, A / D conversion function,
It is a one-chip microcomputer having a D / A conversion function and a PWM function. Reference numeral 131 denotes a power supply unit for applying a voltage to the optical element 101, and its configuration will be described below. 132 is a DC power supply such as a dry battery incorporated in the optical device 150;
133 denotes a voltage output from the power supply 132
DC / D that boosts to a desired voltage value in accordance with the control signal of
The C converters 134 and 135 are amplifiers that amplify the signal level to a voltage level boosted by the DC / DC converter 133 according to a control signal of the CPU 130, for example, a frequency / duty ratio variable signal for realizing a PWM function. is there. The amplifier 134 is a transparent electrode 103 which is a second electrode of the optical element 101 via an LC upright resonance circuit 162 of the capacitance detecting means 161 described later, and the amplifier 135 is a first electrode of the optical element 101. Each is connected to a rod-shaped electrode 125.

That is, in response to the control signal of the CPU 130, the output voltage of the power
3. The amplifier 134 and the amplifier 135 apply the desired voltage value, frequency, and duty to the optical element 101. FIG. 5 is a diagram illustrating voltage waveforms output from the amplifiers 134 and 135. In addition, DC /
The following description is based on the assumption that a voltage of 100 V is output from the DC converter 133 to the amplifiers 134 and 135, respectively. As shown in FIG.
And 135 are connected to the optical element 101, respectively.
From the amplifier 134, as shown in FIG.
According to the 30 control signals, a rectangular waveform voltage is output at a desired frequency and a desired duty ratio. On the other hand, from the amplifier 135,
As shown in FIG. 5C, a rectangular waveform voltage having the same frequency and the same duty ratio is output in a phase opposite to that of the amplifier 134 by the control signal of the CPU 130. This allows
The voltage applied between the transparent electrode 103 and the rod-shaped electrode 125 of the optical element 101 is ± 100 V as shown in FIG.
, Ie, an AC voltage. Therefore, an AC voltage is applied to the optical element 101 by the power supply unit 131.

The effective value of the voltage applied to the optical element 101 from the start of application can be expressed as shown in FIG. 5 (e). (E) will be represented. In the above description, it has been described that a rectangular waveform voltage is output from the amplifiers 134 and 135. However, it is needless to say that a sine wave has the same configuration. In the above description, the case where the power supply 132 is incorporated in the optical device 150 has been described. However, a case where an alternating current is applied to the optical element 101 by an external power supply or a power supply unit may be used.

Next, a configuration and a detection method of the capacitance detecting means of this embodiment will be described with reference to FIG. In this embodiment, the optical element 101 having an unknown capacitance is used.
By applying an AC drive voltage E ₀ having a predetermined frequency f _{0 to} the rod-shaped electrode 125 as the first electrode from the feeding means 131 having the output impedance Z ₀ ,
The current i ₀ flowing out of the transparent electrode 103 which is the second electrode of the LC series resonance circuit 1 having the impedance Zs
62, and a detection voltage Es is generated at the middle point of the LC series resonance circuit 162. This detection voltage Es is proportional to the current i ₀ . Then, the detection voltage Es at the middle point of the LC series resonance circuit 162 is amplified A times by the amplifier 163, and the detection voltage A × Es of the amplifier 163 is converted to AC / DC.
The conversion unit 164 converts the DC voltage into a DC voltage,
To supply. Although a series resonance circuit is used here as the capacitance detecting means, a parallel bridge or the like used in an LCR meter known as a capacitance detecting device may be used.

FIG. 4 shows the relationship between the drive voltage E ₀ and the detection voltage Es generated at the middle point of the LC series resonance circuit 162. The capacitance is C1 <C2. FIG. 4
3D is a graph showing the relationship between the drive voltage and the detection voltage when a short circuit occurs in the circuit of FIG. The optical element 101 is an element having a capacitor structure, and its capacitance is variable with respect to an applied voltage. The higher the applied voltage, the larger the capacitance. When the power supply means 131 from the drive voltage E ₀ 1 is applied, the interface shape 124 is changed in the optical element 101, the detection voltage because the electrostatic capacity is C1 becomes EsI. Then, when the driving voltage is applied to large E ₀ 2 than E ₀ 1, interface shape 124 of the optical element 101
Further changes, the capacitance of the optical element 101 becomes C
2, the detection voltage becomes Es2. Therefore, the relationship between the drive voltage E ₀ and the detection voltage Es for the optical element 101 is a curve as shown in FIG.

FIG. 6 shows an application of the optical element 101 to an optical device. In the present embodiment, a description will be given of an example of a so-called digital still camera in which the optical device 150 photoelectrically converts a still image into an electric signal by an imaging unit and records this as digital data. An imaging optical system 140 includes a plurality of lens groups, and includes a first lens group 141 and a second lens group 1.
42 and an optical element 101. Focus adjustment is performed by moving the first lens group 141 back and forth in the optical axis direction. Zooming is performed by the power change of the optical element 101. Second
The lens group 142 is a non-moving relay lens group. The optical element 101 is disposed between the first lens group 141 and the second lens group 142, and the aperture between the first lens group 141 and the optical element 101 is adjusted by a known technique to adjust the aperture. Aperture unit 14 for adjusting the amount of light flux
3 are arranged.

An image pickup means 144 is arranged at the focal position (planned image plane) of the photographing optical system 140. This is a plurality of photoelectric conversion units that convert the irradiated light energy into electric charges,
A photoelectric conversion unit, such as a two-dimensional CCD, including a charge storage unit that stores the charge and a charge transfer unit that transfers the charge and sends the charge to the outside is used. Reference numeral 145 denotes an image signal processing circuit which converts an analog image signal input from the imaging unit 144 into an A / D signal.
After conversion, image processing such as AGC control, white balance, γ correction, and edge enhancement is performed.

Reference numeral 146 denotes a look-up table provided inside the CPU 130, which is a correspondence table of the focal length f of the photographing optical system 140, the drive voltage E ₀ of the power supply means 131, and the detection voltage Es of the electrostatic detection means. Is read to control the voltage applied to the optical element 101. Reference numeral 151 denotes a display such as a liquid crystal display, which displays the subject image acquired by the imaging unit 144 and the operation status of the optical device having the variable focus lens. 152 is a main switch for activating the CPU 130 from a sleep state to a program execution state;
Is a zoom switch, which changes the focal length of the photographing optical system 140 by performing a zooming operation described later in accordance with the zoom switch operation of the photographer. Reference numeral 154 denotes an operation switch group other than the above switches, which includes a shooting preparation switch, a shooting start switch, a shooting condition setting switch for setting shutter time, and the like. Reference numeral 155 denotes a focus detection unit, which is preferably a phase difference detection type focus detection unit used for a single-lens reflex camera.

Reference numeral 156 denotes a focus driving unit which includes an actuator for moving the first lens group 141 back and forth in the optical axis direction and a driver circuit, and performs a focus operation based on the focus signal calculated by the focus detection unit 155. Adjust the focus state of 140. 157 is a memory means for recording a photographed image signal. In particular,
A removable PC card type flash memory or the like is preferable.

FIGS. 7 and 8 are control flowcharts of the CPU 130 included in the optical device 150 shown in FIG. Hereinafter, a control flow of the optical device 150 will be described with reference to FIGS. In step S101, it is determined whether or not the main switch 152 has been turned on. If the main switch 152 has not been turned on, it is in a standby mode state of waiting for the operation of various switches. If it is determined in step S101 that the main switch 152 has been turned on, the standby mode is released, and the process proceeds to step S102 and subsequent steps. In step S102, the setting of the photographing condition by the photographer is accepted. For example, setting of an exposure control mode (shutter priority AE, program AE, etc.), image quality mode (size of recording pixels, size of image compression ratio, etc.), strobe mode (forced light emission, light emission inhibition, etc.) are performed.

In step S103, it is determined whether or not the photographer has operated the zoom switch 153. If the on operation has not been performed, the process proceeds to step S104. If the zoom switch 153 has been operated here, the process proceeds to step S121. In step S121, the operation amount (operation direction, ON time, and the like) of the zoom switch 153 is detected, and a change instruction value of the focal length of the imaging optical system 140 is calculated based on the operation amount, and the changed focal length f is calculated. The calculation is performed (S122). After the calculation is completed, the process proceeds to a subroutine of “applied voltage control” in the next step S123.

In step S141, step S1
A drive voltage E ₀ for obtaining the focal length f calculated in 22 is calculated and applied. Specifically, the ROM in the CPU 130
The relationship between the drive voltage E ₀ and the detection voltage Es corresponding to each focal length f is stored as a look-up table 146. With reference to the table 146, a predetermined drive voltage E ₀ is Applied to the optical element 101. The capacitance detection unit 161 detects the detection voltage E _SR at that time (S142), the value of E _SR CPU 13
It is determined whether the value is equal to Es read out from the look-up table 146 within 0 (S143). Here, if they match, the process returns to step S102, and if they do not match, the process shifts to step S151 and subsequent steps. Note that, depending on the properties of the optical device, step S143 is performed at the actual detection voltage E.
_{The SR} and the value on the look-up table 146 may have a certain range as well as a complete match. Step S
At 151, it is determined whether or not the value of the detection voltage _ESR is within a predetermined range, and if it is within the range, the process proceeds to step S152. If it is out of the range, it is determined that the optical element 101 has failed,
The process proceeds to step S161 to display a failure on the display 151 (S161), and stops the photographing operation (S1).
62). Note that, depending on the properties of the optical device, step S1
The range of 51 may be slightly wider or narrower.

On the other hand, in step S152, the display 15
1, a warning is displayed, the correction voltage V is calculated from the equation (1) (S153), and the correction voltage V is applied to the optical element 101 from the power supply means 131 based on the calculation result (S15).
4).

Then, the process returns to step S142. That is, the detected voltage value _ESR is stored in the lookup table 147 of the ROM.
Step S14 until it matches the called voltage Es
Steps S154 to S154 are repeated. When they match, the process returns to step S102. That is, the zoom switch 153
If is continuously operated, steps S102 to S123 are repeatedly executed, and the zoom switch 15
When the on operation of No. 3 is completed, the process proceeds to step S104.

In step S104, it is determined whether or not the photographer has turned on a photographing preparation switch (denoted by SW1 in the flowchart of FIG. 7) in the operation switch group 154. If the ON operation has not been performed, the process returns to step S102, and the reception of the photographing condition setting and the determination of the operation of the zoom switch 153 are repeated. Step S10
If it is determined in step 4 that the shooting preparation switch has been turned on, the process proceeds to step S111.

In step S111, the image pickup means 144 and the signal processing circuit 145 are driven to obtain a preview image. The preview image is an image acquired before shooting in order to appropriately set the shooting conditions of the image for final recording and to allow the photographer to grasp the shooting composition. In step S112, the light receiving level of the preview image acquired in step S111 is recognized. Specifically, the maximum, minimum, and average output signal levels of the image signal output by the imaging unit 144 are calculated, and the amount of light incident on the imaging unit 144 is recognized.

In step S113, step S1 is performed.
Based on the amount of received light recognized in step 12, the aperture unit 143 provided in the photographing optical system 140 is driven to adjust the aperture diameter of the aperture unit 143 so as to obtain an appropriate amount of light. In step S114, the preview image acquired in step S111 is displayed on the display 151. Then step S
At 115, the photographing optical system 1 is
Forty focus states are detected. Subsequently, in step S116, the first lens group 1 is
The focusing operation is performed by moving the lens 41 forward and backward in the optical axis direction. Thereafter, the process proceeds to step S117, and it is determined whether or not the photographing switch (in the flowchart, described as SW2) is turned on. When the ON operation has not been performed, the process returns to step S111, and steps from acquisition of the preview image to focus driving are repeatedly executed. As described above, when the photographer turns on the photographing switch while the photographing preparation operation is repeatedly performed, the process jumps from step S117 to step S131.

In step S131, an image is taken. That is, the subject image formed on the imaging unit 144 is photoelectrically converted, and charges proportional to the intensity of the optical image are accumulated in the charge accumulation units near each light receiving unit. In step S132, the charge accumulated in step S131 is read out via the charge transfer line, and the read analog signal is read by the signal processing circuit 1.
45. In step S133, the signal processing circuit 145 converts the input analog image signal into an A / D signal.
The image data is converted and subjected to image processing such as AGC control, white balance, gamma correction, and edge enhancement.
JPEG compression or the like is performed by an image compression program stored in 130. In step S134, the above step S1
At the same time as recording the image signal obtained in step S33 in the memory 157, the preview image is deleted once in step S135, and the image signal obtained in step S133 is displayed again on the display unit 151. Then, the power supply unit 131 is controlled to turn off the voltage application to the optical element 101 (S1).
36), a series of photographing operations ends.

According to the first embodiment, in the optical element having the capacitor structure, the capacitance can be detected by using the drive electrode of the optical element. Further, since the capacitance change corresponds to the area change instead of the distance change, the capacitance can be detected with high accuracy. Further, in an optical device incorporating an optical element having a capacitor structure, by detecting the capacitance of the optical element, it is possible to control the voltage applied to the optical element in order to obtain a desired focal length. Further, there is an effect that a failure of the optical device can be detected. In this embodiment, a digital still camera is taken as an example of the optical device. However, it goes without saying that the present invention can be applied to other video cameras, silver halide cameras, and the like without impairing the effects.

[Embodiment 2] FIGS. 9 to 13 are diagrams relating to Embodiment 2 of the present invention, and FIGS. 9 and 10 are explanatory diagrams relating to the optical element and the feeding means of this embodiment. FIG. 9 is a diagram showing a cross section showing the configuration of the optical element of the present embodiment and a configuration of the power supply means for driving the optical element. The configuration of the optical element will be described with reference to FIG. Reference numeral 801 denotes the entire optical element of the present embodiment, and 802 denotes a disk-shaped first sealing plate made of transparent acrylic or glass. Reference numeral 803 denotes an electrode ring, which is a metal ring-shaped member whose outer diameter is uniform and whose inner diameter gradually increases in a downward direction. An insulating layer 8 made of acrylic resin or the like is formed all around the inner surface of the electrode ring 803.
04 is closely formed. Since the inner diameter of the insulating layer 804 is uniform, the thickness gradually increases downward. Then, a water-repellent treatment agent is applied on the lower side of the entire inner surface of the insulating layer 804 to form a water-repellent film 811 and the insulating layer 80
A hydrophilic treatment agent is applied to the upper part of the entire inner surface of No. 4 to form a hydrophilic film 812.

Reference numeral 806 denotes a disk-shaped second sealing plate made of transparent acrylic or glass.
The rod-shaped electrode 825 is inserted here and sealed with an adhesive. Reference numeral 807 denotes an aperture plate for limiting the diameter of a light beam incident on the optical element 801, which is fixed on the upper surface of the second sealing plate 806. The first sealing plate 802, the metal ring 803, and the second sealing plate 806 are adhered and fixed to each other to form a sealed space of a predetermined volume surrounded by these members, that is, a housing having a liquid chamber. You. This housing is provided with the rod-shaped electrode 825.
The portion other than the insertion portion has a rotationally symmetric shape with respect to the optical axis 823. The liquid chamber is filled with the following two types of liquids.

First, a second liquid 822 is provided on the bottom side of the liquid chamber.
Is dropped by an amount such that the height of the liquid column becomes the same as the height of the water-repellent film 811 forming part. The second liquid 822 is a colorless and transparent silicone oil having a specific gravity of 1.06 and a refractive index of 1.38 at room temperature. Subsequently, the remaining space in the liquid chamber is filled with the first liquid 821. First liquid 8
21 is a mixture of water and ethyl alcohol at a predetermined ratio,
Further, a specific gravity of 1.0 to which a predetermined amount of electrolyte such as salt was added.
6. An electrolytic solution having a refractive index of 1.38 at room temperature. Further first
The liquid 821 is added with an achromatic water-soluble dye, for example, carbon black or a titanium oxide-based material. That is, as the first and second liquids, liquids having the same specific gravity and refractive index, different light absorption efficiencies, and insoluble in each other are selected. Therefore, both liquids form an interface 824, and each of them exists independently without being mixed. The shape of the interface 824 is determined by the balance of three interfacial tensions acting on the point where the three substances of the liquid chamber wall, the first liquid, and the second liquid intersect, that is, the outer edge of the interface 824. In this embodiment, the contact angles of the first and second liquids with respect to the inner wall of the liquid chamber are 9
The materials of the water-repellent film 811 and the hydrophilic film 812 are selected so as to be 0 degrees.

Reference numeral 131 denotes a power supply unit 131 shown in FIG.
Since these members have the same configuration and operation as those described above, detailed description thereof will be omitted. The amplifier 134 of the feeding means 131 is connected to the metal ring 803, and the amplifier 135 is connected to the rod-shaped electrode 825.
Connected to. In this configuration, a voltage is applied to the first liquid 821 via the rod-shaped electrode 825, and the interface 82 is formed by an electrocapillary phenomenon (electrowetting effect).
4 is deformed.

Next, regarding the deformation of the interface 824 of the optical element 801 and the optical action caused by the deformation,
This will be described with reference to FIG. First, when no voltage is applied to the first liquid 821, the shape of the interface 824 becomes flat as described above (FIG. 10A). Here, the second liquid is substantially transparent, but the first liquid has a predetermined light absorbing efficiency due to the added light absorbing material. Therefore, when a light beam is incident from the opening of the aperture plate 807, the first
The light beam is absorbed by an amount corresponding to the optical path length of the liquid, and the intensity of the light beam emitted from the first sealing plate 802 decreases uniformly.

On the other hand, when a voltage is applied to the first liquid, the shape of the interface 824 becomes spherical due to the electrocapillary phenomenon (electrowetting effect) (FIG. 10B). Therefore, the light flux incident from the aperture of the aperture plate 807 also changes the absorptance at a rate corresponding to the change in the optical path length of the first liquid, and the intensity of the light flux emitted from the first sealing plate 802 changes from the center to the periphery. , And the average intensity is higher than in the case of FIG. That is, the interface 8 is controlled by the voltage control of the power supply means 131.
By changing the shape of 24, an optical element that can freely change the amount of transmitted light can be realized. In addition, since the refractive indices of the first and second liquids are equal and only the intensity of the emitted light is changed without changing the direction of the incident light, the aperture means for adjusting the light quantity of the incident light, -Can be used for an optical shutter that blocks light.

The principle of deformation of the two-liquid interface by the electrocapillary phenomenon (electrowetting) is described in International Patent WO99.
/ 18456, and the interface 824 of the present embodiment.
Is the position A of the two-liquid interface described in FIG. 6 of the patent.
And B. The principle and effect of adjusting the amount of transmitted light of the incident light beam due to deformation of the interface between the two liquids are described in Japanese Patent Application No. 11-169657 filed by the present applicant.

FIG. 11 shows an example in which the optical element 801 is applied to an optical device. In this embodiment, similar to the first embodiment,
Reference numeral 161 denotes a capacitance detection unit that detects the capacitance of the optical element 801. The optical device 150 is a so-called digital still camera that photoelectrically converts a still image into an electric signal by an imaging unit and records this as digital data. This will be described as an example. The detailed description of the same components as those in the first embodiment is omitted. An imaging optical system 430 includes a plurality of lens groups, and includes a first lens group 431 and a second lens group 4.
32, and a third lens group 433. Focus adjustment is performed by moving the first lens group 431 in the optical axis direction. Second
Zooming is performed by the reciprocation of the lens group 432 in the optical axis direction. The third lens group 433 is a relay lens group that does not move. Then, the second lens group 432 and the third lens group 4
The optical element 801 is disposed between the optical elements 33. Shooting optical system 4
An imaging unit 144 is arranged at the focal position 30 (planned imaging plane).

Next, the operation of the optical element 801 in this embodiment will be described. The dynamic range of the luminance of a subject existing in the natural world is very large, and in order to keep the dynamic range within a predetermined range, a mechanical diaphragm mechanism is usually provided inside the photographing optical system to adjust the light amount of the photographing light beam. However, it is difficult to reduce the size of the mechanical aperture mechanism, and in a small aperture state where the aperture opening is small, the resolution of the subject image is reduced due to the diffraction phenomenon of light rays by the end face of the aperture blade. Therefore, in this embodiment, by using the optical element 801 as a variable ND filter that substitutes for the mechanical diaphragm mechanism, the amount of light passing through the photographing optical system is appropriately adjusted without causing the above-described disadvantage.

FIGS. 12 and 13 are control flowcharts of the CPU 130 included in the optical device 150 shown in FIG. Hereinafter, a control flow of the optical device 150 will be described with reference to FIGS. 11, 12, and 13. FIG. A detailed description of the same control flow as in the first embodiment will be omitted.
In step S201, the main switch 1
It is determined whether or not 52 has been turned on, and if not, the process remains in step S201. Step S20
If it is determined in step 1 that the main switch 152 has been turned on, the CPU 130 exits the sleep state and executes step S202 and subsequent steps. In step S202, the photographer sets the photographing conditions.

In step S203, it is determined whether or not the photographer has turned on a photographing preparation switch (denoted by SW1 in the flowchart). If the ON operation has not been performed, the process returns to S202, and the determination of the reception of the shooting condition setting is repeated. If it is determined in step S203 that the shooting preparation switch has been turned on, the process proceeds to step S211.
Steps S211 and S212 are the same as in the first embodiment, and a description thereof will be omitted. In step S213, it is determined whether the amount of received light determined in step S212 is appropriate. If it is determined in this step that it is appropriate, the process proceeds to step S214. On the other hand, if it is determined in step S213 that the received light amount determined in step S212 is not appropriate, the process jumps to step S221.

In step S221, an appropriate transmittance is calculated.
After completion of the calculation, the “applied voltage control”
Proceed to subroutine. In step S241, the above
Driving for obtaining proper transmittance calculated in step S221
Voltage E₀Is calculated and applied. Specifically, the CPU 130
Drive voltage E corresponding to each transmittance₀and
The relationship between the detection voltages Es is represented by a lookup table 146.
The table is referred to the power supply means.
131, a predetermined driving voltage E₀To the optical element 101
Apply. Detection at that time by the capacitance detecting means 161
Voltage E_SRIs detected (S242), and E _SRIs the value of
Es is equal to Es read from lookup table 146
It is determined whether it is (S243).

Here, if they match, step S
Returning to step 202, if they do not match, the process proceeds to step S251 and subsequent steps. Note that, depending on the properties of the optical device, in step S243, the actual detection voltage _ESR and the value on the look-up table 146 may have a certain range as well as completely coincidence. In step S251, the detection voltage E _SR
Is determined to be within a predetermined range, and if it is within the range, the process proceeds to step S252. If out of the range, the optical element 10
1 is determined to be faulty, the process proceeds to step S261, and the display 151 indicates that the fault has occurred (S26).
1) The photographing operation is stopped (S262). Note that the range of step S151 may be slightly wider or narrower depending on the properties of the optical device.

On the other hand, in step S252, the display 15
1, a warning is displayed, the correction voltage V is calculated from the equation (2) (S253), and the correction voltage V is applied to the optical element 101 from the power supply means 131 based on the calculation result (S25).
4).

Then, the process returns to step S242. That step until the detected voltage value E _SR matches the voltage Es of calling from a look-up table 146 of ROM S242
To S254 are repeated. Steps S214 to S237 are the same as those in the first and second embodiments, and a description thereof will be omitted.

As described above, in an optical device incorporating an optical element having a capacitor structure, by detecting the capacitance of the optical element, the voltage applied to the optical element is controlled to obtain a desired transmittance. can do. Further, there is an effect that a failure of the optical device can be detected. In this embodiment, a digital still camera is taken as an example of the optical device. However, it goes without saying that the present invention can be applied to other video cameras, silver halide cameras, and the like without impairing the effects.

[0051]

As described above, according to the present invention, the capacitance corresponding to the change of the variable focal point of the optical element utilizing the electrocapillary phenomenon (electrowetting) is calculated as follows.
By using the drive electrodes of the optical element without providing a capacitance detection electrode, a simple configuration can be achieved. In addition, since the capacitance change corresponds to the area change instead of the distance change, the accuracy can be improved. Thus, it is possible to realize a capacitance detection device capable of performing good detection and accurately controlling various operations of the optical device based on the detection result, and an optical device including the capacitance detection device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an optical element according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram when a voltage is applied to the optical element according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a configuration of an electrostatic capacitance detection unit and a power supply unit and an optical element according to the first embodiment of the present invention.

FIG. 4 is a relationship diagram between a drive voltage and a detection voltage according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a voltage waveform output from an amplifier of a feeding unit according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical device incorporating the optical element according to the first embodiment of the present invention.

FIG. 7 is a control flowchart of the optical device according to the first embodiment of the present invention.

FIG. 8 is a control flowchart of the optical device according to the first embodiment of the present invention.

FIG. 9 is a diagram illustrating a cross section illustrating a configuration of an optical element according to a second embodiment of the present invention and a configuration of a power supply unit that drives the optical element.

FIG. 10 is a diagram for explaining deformation of an interface due to application of a voltage to an optical element according to the second embodiment of the present invention, and an optical action due to the deformation.

FIG. 11 is a configuration diagram of an optical device incorporating a capacitance detection unit, a power supply unit, and an optical element according to a second embodiment of the present invention.

FIG. 12 is a control flowchart of an optical device according to a second embodiment of the present invention.

FIG. 13 is a control flowchart of the optical device according to the second embodiment of the present invention.

[Explanation of symbols]

 101 optical element 102 transparent substrate 103 transparent electrode 104 insulating layer 107 diaphragm plate 111 water repellent film 112 hydrophilic film 113 hydrophilic film 121 ... 1st liquid 122 ... 2nd liquid 123 ... optical axis 124 ... interface 125 ... rod-shaped electrode 130 ... CPU 131 ... feeding means 132 ... DC power supply 133 ... DC / DC converters 134, 135 ... amplifiers 140, 430 ... photographing optical systems 141, 431 ... first lens groups 142, 432 ... second lens groups 433 ... third lenses Group 143 ... Aperture unit 144 ... Imaging unit 145 ... Image signal processing unit 150 ... Optical device 151 ... Display unit 152 ... Main switch 153 ... Zoom switch 16 DESCRIPTION OF SYMBOLS 1 ... Capacitance detection means 162 ... LC series resonance circuit 163 ... Amplifier 164 ... AC / DC conversion means 801 ... Optical element 802 ... First sealing plate 803 ... An electrode ring 804 an insulating layer 806 a second sealing plate 811 a water-repellent film 812 a hydrophilic film 821 a first liquid 822 a second liquid 824 ..Interface 825: rod-shaped electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G03B 3/04 G03B 3/04 13/32 (72) Inventor Goro Noto 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 F term in Canon Inc. (reference) 2F065 AA02 AA06 LL10 2G028 AA05 BC04 CG07 DH04 EJ01 FK01 GL07 MS03 2G060 AA09 AE40 AF10 AG11 EA06 2H044 BF01 BF05 2H051 FA61 GB00 GB03

Claims (14)

[Claims] An electroconductive or polar first liquid and a second liquid which are not mixed with the first liquid are sealed in a container with their interfaces having a predetermined shape. An optical element whose optical characteristics change due to a change in the interface shape caused by application of a voltage between the first electrode and the second electrode provided in the container; and a predetermined voltage applied to the electrode to change the interface shape. Power supply means for applying voltage, control means for controlling the applied voltage, and capacitance detection means for detecting a capacitance between the first electrode and the second electrode, wherein the optical capacity is detected by the capacitance detection means. An electrostatic capacitance detecting device for an optical element, which detects an electrostatic capacitance corresponding to a change in an interface shape of the element. 2. A conductive or polar first liquid and a second liquid which are not mixed with the first liquid are sealed in a container with their interfaces having a predetermined shape. An optical element whose optical characteristics change due to a change in interface shape due to a voltage applied between a first electrode and a second electrode provided in the container; and a predetermined electrode on the electrode for changing the shape of the interface. An optical device comprising: a power supply unit that applies a voltage; a control unit that controls the applied voltage; and a capacitance detection unit that detects a capacitance between the first electrode and the second electrode. . 3. The optical device according to claim 2, wherein a focal length is controlled based on the capacitance detected by said capacitance detecting means. 4. The optical device according to claim 2, wherein the capacitance detected by said capacitance detecting means is displayed on a display means. 5. A method for controlling a voltage applied to said optical element by judging whether or not a detected value of said capacitance is within an allowable range based on the capacitance detected by said capacitance detecting means. The optical device according to claim 2, wherein: 6. An apparatus according to claim 1, further comprising: a photographing optical system; and an image pickup recording unit, and judges whether a detected value of the capacitance is within an allowable range based on the capacitance detected by the capacitance detection unit. The optical device according to claim 2, wherein the optical device controls an image pickup recording operation. 7. The first liquid and the second liquid have substantially different refractive indices, and are sealed in the container with their interfaces in a large R shape when the voltage is not applied. The optical device according to claim 1, wherein: 8. The first liquid and the second liquid have substantially the same refractive index, and their interfaces are substantially flat when no voltage is applied. The method according to any one of claims 1 to 6, wherein
The optical device according to Item. 9. An electrode comprising a first electrode and a second electrode insulated from the first liquid, wherein the first electrode is provided so as to be electrically connected to the first liquid. The optical device according to claim 1, wherein: 10. The optical device according to claim 9, wherein the first electrode is provided so as to be electrically connected to the first liquid from a side surface of the container. 11. The optical device according to claim 9, wherein the first electrode is provided so as to be electrically connected to the first liquid from an upper surface side of the container. 12. The optical device according to claim 9, wherein the second electrode is provided on a side surface of the container. 13. The optical device according to claim 12, wherein the second electrode is a ring-shaped electrode and is disposed so as to surround the second liquid. 14. The optical device according to claim 13, wherein the ring-shaped electrode has a shape whose inner diameter gradually increases in a light beam emitting direction.