JP2002169110A - Optical element, optical device and photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent eccentricity of an optical element by utilizing the electrowetting effect. SOLUTION: In this optical element, first liquid 121 which has electrical conductivity and polarity and second liquid 122 which is immiscible with the first liquid are stored in a container, the shape of an interface 124 between the first liquid and the second liquid is changed according to the change of voltage impressed between the first liquid and an electrode 103 disposed on the side of a container 105 and, thereby the optical characteristics thereof are changed. Therein, interface retaining parts 113, 114 which are brought into contact with one part of the interface and suppress the movement of optical axis of optical operation part in the interface are disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element utilizing an electrowetting effect (electrocapillary phenomenon) and an optical device having this optical element.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 11-352453 discloses a varifocal lens which uses a liquid crystal as an optical element utilizing a liquid, and adjusts a focal length by forming and changing a refractive index distribution by changing an electric field, a magnetic field and a temperature. Has been proposed.

Further, a variable focus lens which adjusts the focal length by changing the shape of the interface between two liquids by changing the voltage by utilizing the electrowetting effect (electrocapillary phenomenon) is disclosed in WO 99/184456. It is disclosed in.

[0004] In the variable focus lens using such a liquid, there is a problem that the eccentricity of the lens occurs when the focal length is changed by driving means such as a voltage.

On the other hand, Japanese Unexamined Patent Application Publication No. 11-35245 discloses
No. 3 proposes a method of making the focal length variable, but does not propose a method for preventing eccentricity of the lens.

On the other hand, the configuration disclosed in International Patent Publication No. 99/184456 is as shown in FIG. 9 of the present application.

In FIG. 9, an optical element is a substrate 901.
, Electrodes 902, 905, insulating layer 903, surface treatment layer 905, silicone oil 906, electrolyte 907
It is composed of In this optical element, the thickness of the insulating layer 903 is changed from the center of the optical axis to the radially outward direction.

[0008] By changing the thickness of the insulating layer 903 in this manner, the distribution of the electrolytic strength in the insulating layer 903 is given, and the electrical eccentricity is prevented.

[0009]

In order to reduce the interface driving voltage applied between the electrodes 902 and 905 in the optical element shown in FIG. 9, it is necessary to make the insulating layer 903 thinner.

However, it is technically difficult to reduce the thickness of the insulating layer 903 and to change the thickness in order to prevent eccentricity of the optical element.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical element utilizing the electrowetting effect so that its eccentricity can be prevented with a simple structure.

[0012]

In order to achieve the above object, according to the present invention, a first liquid having conductivity or polarity and a second liquid which is not mixed with the first liquid are provided. Optical properties are accommodated in a container, and the shape of the interface between the first liquid and the second liquid changes according to the change in the voltage applied between the first liquid and the electrode provided on the container side, whereby the optical characteristics are improved. In the optical element that changes, an interface holding portion that contacts the part of the interface and suppresses displacement of the optical axis of the optically acting portion at the interface is provided in the container.

According to this, the first voltage is changed according to the change of the applied voltage.
Even if the shape of the interface between the liquid and the second liquid changes, the optical axis displacement (that is, eccentricity) of the optically acting portion at the interface is suppressed by the function of the interface holding portion, and thus the optical performance of the optical element It is possible to maintain In addition, since it is only necessary to provide the interface holding portion in the container, it is possible to suppress the eccentricity of the optical action portion with a simple configuration.

Further, by suppressing the change of the shape, the size and the position of the optically acting portion on the plane orthogonal to the optical axis by the interface holding portion, only the curvature of the optically acting portion is changed according to the change of the applied voltage. And the optical power can be easily controlled while maintaining the effective diameter of the optically active portion.

[0015] Specifically, the interface holding section may be constituted by first and second adsorbing sections having adsorbing properties for the first liquid and the second liquid, respectively.

Further, it is preferable that the interface holding portion is formed in a shape (in particular, an annular shape) in contact with the interface so as to surround the outer periphery of the optically active portion. By using the ring shape, it is possible to obtain a spherical surface centered on the optical axis as the optically active portion.

By providing the interface holding portion from the first liquid side to the tip of the member in contact with the interface, it is possible to freely set the effective diameter of the optically active portion without changing the volume of the second liquid. It is possible.

Further, by providing the interface holding portion from the second liquid side to the tip of the member which is in contact with the interface, the volume of the second liquid is changed, thereby setting the curvature of the optically active portion in the state where no voltage is applied. It is possible to do.

By setting the inner diameter of the interface holding portion to 3 mm or more, it becomes possible to allow the second liquid such as silicone oil to smoothly enter the inside of the interface holding portion. Eccentricity can be suppressed.

By providing the above-mentioned optical element and a power supply control circuit for changing a voltage applied between the first liquid and an electrode provided on the container side, electrowetting can be performed without optical eccentricity. It is possible to realize an optical device in which the optical power is made variable by the effect.

Further, by constituting a photographing apparatus provided with a photographing optical system including the above-described optical element, it is possible to realize an image pickup apparatus in which the focal length can be varied by the electrowetting effect without optical eccentricity. It is.

[0022]

(First Embodiment) FIGS. 1 and 2
Now, the configuration and optical function of the optical element according to the first embodiment of the present invention will be described. In the present embodiment,
The description will be made assuming that the optical axis 123 of the optical element extends in the vertical direction.

In these figures, reference numeral 101 denotes the entire optical element of the present embodiment. Reference numeral 102 denotes a transparent acrylic transparent substrate. A transparent electrode (ITO) 103 made of indium tin oxide is formed on the upper surface of the transparent substrate 102 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 irradiating with UV to cure.

A cylindrical container body 105 having a light-shielding property is adhesively fixed on the upper surface of the insulating layer 104, and a transparent acrylic upper cover 106 is adhesively fixed on the upper surface. Further, on the upper surface of the upper cover 106, a diaphragm plate 107 having an opening having a diameter D2 in the center is arranged.

In the above configuration, a container having a predetermined volume of space surrounded by the insulating layer 104, the container body 105, and the upper cover 106, that is, a container having a liquid chamber is formed. The inner wall surface surrounding the liquid chamber is subjected to the following surface treatment.

First, a water-repellent agent is applied to the center upper surface of the insulating layer 104 within a range of a diameter D1 to form a water-repellent film 111. As the water repellent, a fluorine compound or the like is suitable.

A hydrophilic treatment agent is applied to a region outside the diameter D1 of the water-repellent film 111 on 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 upper cover 106, a cylindrical member 128 (a member extending from a first liquid side described later to a position in contact with the interface) having a height t1 having an inner diameter B1 equal to the diameter D2 of the diaphragm plate 107 is provided. Is provided. At least one hole 129 is formed in the peripheral wall of the cylindrical member 128.

It is desirable that the inner diameter B1 of the cylindrical member 128 be smaller than the diameter A1 of the lens bottom surface, which will be described later, and that B1 ≧ 3 mm. The reason will be described later.

The inner surface of the cylindrical member 128 is subjected to a hydrophilic treatment, and a hydrophilic film (first adsorption portion) 113 having the same properties as the hydrophilic film 112 is formed. In addition, a lipophilic treatment is applied to the tip of the cylindrical member 128 to form a lipophilic film (second adsorbing portion) 114 having an adsorbing property (affinity or wettability) with respect to a second liquid described later. Have been.

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 body 105, and the rod-like electrode 125 is inserted into the hole. The gap between the rod-shaped electrode 125 and the hole is sealed with an adhesive,
The tightness of the liquid chamber is maintained. The transparent electrode 103 and the rod-shaped electrode 125 have a power supply circuit 131 described later.
Are connected, and a predetermined voltage can be applied between both electrodes.

The above-mentioned liquid chamber is filled with the following two types of liquids. First, the water-repellent film 111 on the insulating layer 104
The second liquid 122 is dropped by a predetermined amount on the top.
The second liquid 122 is colorless and transparent, has a specific gravity of 1.06,
Silicon oil having a refractive index of 1.49 at room temperature is used.

On the other hand, the remaining space in the liquid chamber is filled and accommodated with the first liquid 121. The first liquid 121 is an electrolytic solution (conductive or polar) having a specific gravity of 1.06 and a refractive index of 1.38 at room temperature, in which water and ethyl alcohol are mixed at a predetermined ratio and a predetermined amount of salt is added. Which is a liquid having

That is, in the present embodiment, as the first and second liquids 121 and 122, liquids having the same specific gravity, different refractive indices, and immiscible (insoluble) are selected. Therefore, both liquids 12
1 and 122 form an interface 124 having a shape to be described later, and are each independently housed in the liquid chamber without being mixed.

Next, the shape of the interface 124 will be described. First, as shown in FIG.
When no voltage is applied between the liquid 121) and the transparent electrode 103, the shape of the interface 124 is such that both liquids 121 and
The interfacial tension between the first liquid 121 and the insulating layer 104
Interfacial tension with the upper water-repellent film 111 or hydrophilic film 112,
The interfacial tension between the second liquid 122 and the water-repellent film 111 or the hydrophilic film 112 on the insulating layer 104, the interfacial tension between the second liquid 122 and the lipophilic film 114 on the cylindrical member 128, and the Determined by volume.

In the present embodiment, the material is selected such that the interfacial tension between the silicone oil as 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 122
The outer edge of the lens-shaped liquid droplet formed by has a tendency to spread, and becomes stable when the outer edge coincides with the application area of the water-repellent film 111.

As a result, the diameter A 1 of the lens bottom surface formed by the second liquid 122 is equal to the diameter D 1 of the water-repellent film 111. Further, since the interface 124 is in contact with the annular lipophilic film 114 and the hydrophilic film 113, the effective diameter as a lens is equal to the inner diameter B1 of the cylindrical member 128. For this reason,
By changing the inner diameter B1, the effective diameter can be changed freely.

At this time, the cylindrical member 128 holds the first liquid 1
Since it is provided only on the 21 side, there is no need to change the volume of the second liquid 122. The inner diameter B1 is B1 ≧ 3.
mm is desirable. This is because if the inner diameter B1 is smaller than 3 mm, the second liquid 122 cannot enter the cylindrical member 128 due to the interfacial tension between the first liquid 121 and the second liquid 122.

Since the specific gravities of the two liquids 121 and 122 are equal as described above, apparently no gravity acts on these liquids. For this reason, the interface 124 is
The radius of curvature and the height are determined by the volume of the second liquid 122 except where it is in contact with.

On the other hand, as shown in FIG.
From the rod-shaped electrode 125 (first liquid 121) and the transparent electrode 1
When a voltage is applied between the first liquid 121 and the hydrophilic film 112, the interfacial tension between the first liquid 121 and the hydrophilic film 112 decreases due to an electrowetting effect (electrocapillary phenomenon).
Crosses the boundary between the hydrophilic film 112 and the water-repellent film 111 and enters the water-repellent film 111.

As a result, as shown in FIG. 2, the diameter of the bottom surface of the lens formed by the second liquid 122 decreases from A1 to A2, and the second liquid 122 enters the inside of the cylindrical member 128. Accordingly, the first liquid 121 existing inside the cylindrical member 128 passes through the hole 129 and the cylindrical member 1
Pushed out of 28. As a result, the height of the lens is h
It increases from 1 to h2.

At this time, a lipophilic film 114 is formed at the lower end of the cylindrical member 128, and a hydrophilic film 113 is formed on the inner surface of the cylindrical member 128 and the inner diameter of the lipophilic film 114. Lipophilic film 114 and hydrophilic film 1
The position of the portion P that is in contact with the lower end of the lens 13 is fixed, and only the curvature of the lens upper surface portion (the optically active portion) of the interface 124 inside the hydrophilic film 113 changes.

As described above, by applying a voltage between the first liquid 121 and the transparent electrode 103, the two kinds of liquids 121,
The balance of the interfacial tension of the two liquids 121 and 122 changes.
The shape of the interface 124 between the 122 changes.

Therefore, by controlling the voltage applied between the first liquid 121 and the transparent electrode 103 by the power supply circuit 131, an optical element that can freely change the shape (curvature) of the lens upper surface portion of the interface 124 is provided. Can be configured.

Then, the first and second liquids 121, 1
Since the lenses 22 have different refractive indices, optical power (1 / f: f is a focal length) is given as a lens, and the optical element 101 changes the curvature of the upper surface of the lens at the interface 124. Thereby, a variable focus lens whose optical power is variable is obtained.

Further, since the radius of curvature of the upper surface of the lens in the state of FIG. 2 is smaller than that in the state of FIG. 1, the focal length of the optical element 101 in the state of FIG. 2 is shorter than that in the state of FIG. Become. On the other hand, the shape and size of the effective diameter of the lens and the position of the optical axis 123 are substantially maintained. As a result, by controlling the voltage of the power supply circuit 131, it is possible to realize an optical element in which only the curvature (that is, the optical power) changes while the lens optical axis 123 is aligned. That is, the optical axis displacement (eccentricity) of the lens can be reduced.

As described above, according to this embodiment, the lipophilic film 114 and the hydrophilic film 113 (lower end) as the interface holding portion are provided in the container, so that the optically active portion (lens) of the interface 124 is provided. Top surface shape change (curvature change)
The displacement (eccentricity) of the optical axis 123 due to the above can be suppressed, and the optical performance of the optical element 101 can be maintained and improved.

In addition, the above effect can be obtained with a simple structure in which the cylindrical member 128 is disposed in the container, the lipophilic film 114 is provided at the end, and the hydrophilic film 113 is provided on the inner surface.
Cost can be reduced.

The effective diameter of the lens can be freely set by changing the inner diameter of the cylindrical member 128, so that an optical element having a desired effective diameter of the lens can be easily obtained.

In the present embodiment, the second liquid 122
The lens effective diameter can be set freely without changing the volume of the lens.

Next, with reference to FIG.
The relationship between the output voltage of the optical element 31 and the deformation of the interface 124 (the upper surface of the lens) of the optical element 101 will be described.

In FIG. 3A, when a voltage having a voltage value V0 is applied to the optical element 101 at time t0, deformation of the interface 124 of the optical element 101 starts at a time constant t11 (see FIG. 3B). . Even if the voltage application is continued as it is, a considerably long time is required until the interface 124 reaches the desired change amount δ0.

Therefore, as for the optical system, the amount of deformation that can be tolerated as an error, for example, 95% of the desired interface change amount δ0 (expressed as 0.95δ0) in FIG.
Is considered to have reached the desired amount of deformation when is deformed (time t12). If this deformation amount is not reached, the next control of the optical element 101 is set so as not to proceed. Note that the allowable deformation amount is determined based on the optical system in which the optical element 101 is incorporated.

FIG. 4 shows the configuration of a power supply control circuit that includes the power supply circuit 131 and controls the voltage applied to the optical element 101.

In FIG. 4, reference numeral 130 denotes a central processing unit (hereinafter abbreviated as CPU) for controlling the entire operation of the optical device constituted by using the optical element 101;
1 with RAM, EEPROM, A / D conversion function, D / A conversion function, PWM (Pulse Width Modulation) function
It is a chip microcomputer.

In a power supply circuit 131 surrounded by a dotted line frame in FIG. 4, reference numeral 132 denotes a DC power supply such as a dry battery incorporated in the optical device 151, and reference numeral 133 denotes a voltage output from the power supply 132 in accordance with a control signal of the CPU 130. DC / DC converters 134 and 135 for boosting to a voltage value of
An amplifier that amplifies the signal level to a voltage level boosted by the DC / DC converter 133 in response to a control signal of 130, for example, a variable frequency / duty ratio signal that realizes a PWM function.

The amplifier 134 is connected to the transparent electrode 103 of the optical element 101, and the amplifier 135 is connected to the rod-shaped electrode 125 of the optical element 101.

That is, in response to the control signal of the CPU 130, the output voltage of the power
The voltage, the frequency, and the duty ratio are converted into desired values by the amplifier 33, the amplifier 134, and the amplifier 135, and are applied to the optical element 101.

FIG. 5 is a diagram for explaining voltage waveforms output from the amplifiers 134 and 135. In addition, DC / DC
The following description is based on the assumption that a voltage of 100 V is output from converter 133 to amplifiers 134 and 135, respectively.

As shown in FIG. 5A, the amplifier 134
Is connected to the transparent electrode 103, and the amplifier 135 is connected to the rod-shaped electrode 125, respectively.

As shown in FIG. 5B, a desired frequency corresponding to the control signal of the CPU 130 is output from the amplifier 134.
A rectangular waveform voltage is output at the duty ratio. On the other hand, from the amplifier 135, as shown in FIG.
According to the 30 control signals, the phase is opposite to that of the amplifier 134,
A rectangular waveform voltage having the same frequency and the same duty ratio is output. Thereby, the transparent electrode 1 of the optical element 101
03 and the voltage applied between the rod electrodes 125 are shown in FIG.
As shown in (d), the voltage has a rectangular waveform of ± 100 V, that is, an AC voltage.

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). It is represented according to FIG.

Although the description has been made here assuming that the amplifiers 134 and 135 output voltages having a rectangular waveform,
The same is true even if a sine waveform voltage is output.

Although the case where the power supply 132 is incorporated in the optical device has been described, alternating current may be applied to the optical element 101 by an external power supply or an external power supply circuit.

(Second Embodiment) FIG. 6 shows an example in which the optical element 101 of the first embodiment is applied to a photographing device as an optical device. Photographing device 150 of the present embodiment
Is a so-called digital still camera in which a still image is photoelectrically converted by an image sensor into an electric signal and this is recorded as digital data.

In FIG. 6, reference numeral 140 denotes a photographing optical system (imaging optical system) including a plurality of lens groups, and includes a first lens group 141, a second lens group 142, and the optical element 101.

The photographing optical system 140 includes the first lens group 1
Focus adjustment is performed by moving the optical element 41 in the optical axis direction, and the optical element 1
Zooming is performed with a power change of 01. The second lens group 142 is a relay lens group that does not move.

The optical element 101 is disposed between the first lens group 141 and the second lens group 142, and the distance between the first lens group 141 and the optical element 101 is changed by changing the aperture diameter. Aperture unit 14 for adjusting light quantity
3 are arranged.

An image sensor 144 is arranged at the focal position (planned image plane) of the photographing optical system 140. this is,
A photoelectric conversion element, such as a two-dimensional CCD, including a plurality of photoelectric conversion units that convert the irradiated light energy into electric charges, a charge accumulation unit that stores the electric charges, and a charge transfer unit that transfers the electric charges and sends them to the outside is used. .

An image signal processing circuit 145 performs A / D conversion on an analog image signal input from the image sensor 144 and performs image processing such as AGC control, white balance, γ correction, and edge enhancement.

Reference numeral 151 denotes a display such as a liquid crystal display.
The image of the subject acquired through the image sensor 144 and the operation status of the photographing device 150 are displayed.

Reference numeral 152 denotes the CPU described in the first embodiment.
A main switch for activating 130 from a sleep state to a program execution state.

Reference numerals 153a and 153b denote wide (W) and tele (T) zoom switches, respectively.
In response to the operation of these zoom switches by the photographer, the drive of changing the focal length of the photographing optical system 140 is performed.

Reference numeral 154 denotes an operation switch group other than the above switches, which includes a photographing preparation switch, a photographing start switch, a photographing condition setting switch for setting shutter time, and the like.

Reference numeral 155 denotes a focus detection device which performs a phase difference detection type focus detection operation used in a single-lens reflex camera, or detects a distance to a subject using the principle of triangulation.

Reference numeral 156 denotes a focus drive circuit,
An actuator and a driver circuit for moving the lens group 141 in the optical axis direction and a driver circuit, and perform a focus operation based on a focus signal calculated by the focus detection device 155;
The photographing optical system 140 is focused.

Reference numeral 157 denotes an external memory for recording a captured image signal. Specifically, a removable PC card type flash memory or the like is preferable.

FIG. 7 is a view showing a CP included in the photographing device 150.
It is a control flowchart which shows operation of U130. Hereinafter, the operation of the photographing apparatus 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, the apparatus enters a standby mode in which it waits 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 the next step S102 and subsequent steps.

In step S102, the photographer sets the photographing conditions. For example, settings such as exposure control mode setting (shutter priority AE, program AE, etc.), image quality mode (size of recording pixels, size of image compression ratio, etc.), strobe mode (forced emission, emission inhibition, etc.) are accepted.

In step S103, the photographer sets W
It is determined whether or not the side zoom switch 153a has been operated. If the on operation has not been performed, the process proceeds to step S104. If the W-side zoom switch 153a has been operated here, the flow shifts to step S121.

In step S121, the operation amount (operation direction, ON time, etc.) of the W-side zoom switch 153a is detected, and the corresponding focal length change amount is calculated based on the operation amount (S122). Then, in step S123,
The amount of voltage applied to the optical element 101 is determined based on the calculation result, and the output voltage of the power supply circuit 131 is controlled to apply the voltage to the optical element 101 (S124). Then, the process returns to step S102.

That is, when the W-side zoom switch 153a is continuously operated, the steps S102 to S124 are repeatedly executed, and the W-side zoom switch 153a is repeatedly operated.
When the ON operation of 3a is completed, the process proceeds to step S104.

In step S104, T
It is determined whether or not the side zoom switch 153b has been operated. If the ON operation has not been performed, the process proceeds to step S105. If the T-side zoom switch 153b has been operated here, the flow shifts to step S121.

In step S121, the operation amount (operation direction, ON time, etc.) of the T-side zoom switch 153b is detected, and the corresponding focal length change amount is calculated based on the operation amount (S122). Then, in step S123,
The amount of voltage applied to the optical element 101 is determined based on the calculation result, and the output voltage of the power supply circuit 131 is controlled to apply the voltage to the optical element 101 (S124). Then, the process returns to step S102.

That is, when the T-side zoom switch 153b is continuously operated, Steps S102 to S124 are repeatedly executed, and the T-side zoom switch 153b is repeatedly operated.
When the on operation of Step 3b is completed, the process proceeds to Step S105.

In step S105, it is determined whether or not the photographer has turned on the 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 S1
If it is determined in step 05 that the shooting preparation switch has been turned on, the process proceeds to step S111.

In step S111, the image pickup device 144 and the signal processing circuit 145 are driven to obtain a preview image. The preview image is an image acquired before photographing in order to appropriately set the photographing conditions of the final recording image and to allow the photographer to grasp the photographing composition.

In step S112, step S111
Recognize the light receiving level of the preview image acquired in step (1). Specifically, in the image signal output from the image sensor 144, the highest, lowest, and average output signal levels are calculated,
The amount of light incident on the image sensor 144 is recognized.

In step S113, step S112
The aperture unit 143 provided in the photographing optical system 140 is driven based on the amount of received light recognized in step S1 to adjust the aperture diameter of the aperture unit 143 so that an appropriate amount of light is obtained.

In step S114, step S111
Is displayed on the display 151.
Subsequently, in step S115, the focus adjustment state of the imaging optical system 140 is detected using the focus detection device 155. Subsequently, in step S116, the focus driving circuit 15
6, the first lens group 141 is moved back and forth in the optical axis direction,
Perform focusing operation.

Thereafter, the flow advances to step S117 to determine whether or not the photographing switch (in the flowchart, denoted as SW2) has been turned on. When the ON operation has not been performed, the process returns to step S111, and the steps from acquisition of the preview image to focus driving are repeatedly executed.

As described above, if the photographer turns on the photographing switch while the photographing preparation operation is being repeatedly executed, the process jumps from step S117 to step S131.

In step S131, imaging is performed. That is, the subject image formed on the image sensor 144 is photoelectrically converted, and charges proportional to the intensity of the optical image are stored in the charge storage units near each light receiving unit.

In step S132, step S131
Read out the charge accumulated at
The read analog signal is input to the signal processing circuit 145.

In step S133, the signal processing circuit 14
In step 5, the input analog image signal is A / D converted, subjected to image processing such as AGC control, white balance, γ correction, edge enhancement, and the like.
JPEG compression or the like is performed by the image compression program stored in the “0”.

In step S134, 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. Thereafter, the power supply circuit 131 is controlled to turn off the voltage application to the optical element 101 (S13).
6), a series of photographing operations ends.

In the present embodiment, a digital still camera is taken as an example of a photographing device. However, the optical element of the present invention is not limited to a video camera, a silver halide camera, and other optical devices including an optical system. The present invention can be applied to a device without impairing the effect.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
1 illustrates a configuration of an optical element according to an embodiment. Here, the description will be made assuming that the optical axis 223 of the optical element extends in the vertical direction.

In the first embodiment, in order to reduce the optical axis displacement (eccentricity) of the optical element in which the shape of the interface between the two liquids changes due to the application of a voltage, the second liquid is placed on the first liquid 121 side. Cylindrical member 1 having lipophilic film 114 that adsorbs 122
In the present embodiment, the case where the cylindrical member 228 having the hydrophilic film 213 that adsorbs the first liquid 121 is provided will be described.

The components common to those of the first embodiment among the components of the optical element 201 of the present embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof will be omitted.

The optical element 201 of the present embodiment has an aperture diameter D
3, a cylindrical member 228 having an inner diameter B2 and a height t2 is provided on the second liquid 122 side, that is, on the water-repellent film 111 on the insulating layer 104. At least one or more holes 229 are formed in the peripheral wall of the cylindrical member 228.

The inner diameter B3 of the cylindrical member 228 is different from that of the water-repellent film 11
It is desirable that the diameter D1 be smaller than the diameter D1 and B3 ≧ 3 mm. The inner surface of the cylindrical member 228 is subjected to lipophilic treatment, and a lipophilic film (second adsorbing portion) 214 is formed.

Further, the upper end portion of the cylindrical member 228 is subjected to a hydrophilic treatment, and a hydrophilic film (first suction portion) 213 is formed. Further, the container (liquid chamber) is filled with the second liquid 122 so that the height h3 of the second liquid 112 satisfies h3 ≧ t2, and the first liquid is filled in the remaining space of the liquid chamber. 12
1 is filled and stored. In addition, these 1st and 2nd
The same liquids 121 and 122 as those in the first embodiment are used. The two liquids 121 and 122 form an interface 124 having a shape described later, and each of the liquids 121 and 122 independently fits in the liquid chamber without being mixed. ing. I have.

Next, the shape of the interface 124 will be described. First, as shown in FIG.
When no voltage is applied between the (first liquid 121) and the transparent electrode 103, the shape of the interface 124 is
1, 122, the first liquid 121 and the insulating layer 1
04, the interfacial tension with the water-repellent film 111 or the hydrophilic film 112, the second liquid 122 and the water-repellent film 111 on the insulating layer 104.
Alternatively, the interfacial tension with the hydrophilic film 112, the second liquid 122
And the volume of the second liquid 122.

In the present embodiment, the material is selected such that the interfacial tension between the silicone oil as 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 122
The outer edge of the lens-shaped liquid droplet formed by has a tendency to spread, and becomes stable when the outer edge coincides with the application area of the water-repellent film 111.

That is, the diameter A3 of the lens bottom surface formed by the second liquid 122 is equal to the diameter D1 of the water-repellent film 111. Since the interface 124 is in contact with the upper ends of the annular hydrophilic film 213 and the lipophilic film 114, the effective diameter of the lens is equal to the inner diameter B3 of the cylindrical member 228.

Since the specific gravities of the two liquids 121 and 122 are equal, gravity does not seem to act on these liquids 121 and 122 apparently. Thus, the interface 124 is
The surface becomes a spherical surface except where it is in contact with the hydrophilic film 213, and its radius of curvature and height are determined by the volume of the second liquid 122.

On the other hand, the rod-shaped electrode 125
When a voltage is applied between the (first liquid 121) and the transparent electrode 103, as shown in FIG. 8B, the first liquid 12 is formed by an electrowetting effect (electrocapillary phenomenon).
1 and the hydrophilic film 112, the first liquid 1
21 crosses the boundary between the hydrophilic film 112 and the water-repellent film 111 and enters the water-repellent film 111. As a result, the second liquid 1
The diameter of the bottom surface of the lens created by 22 decreases from A3 to A4, and second liquid 122 passes through hole 229 to form cylindrical member 22.
8, the height of the lens increases from h3 to h4.

The hydrophilic film 2 is provided on the upper end of the cylindrical member 228.
13 are formed, and the lipophilic film 214 is formed on the inner surface of the cylindrical member 228 and the inner diameter of the hydrophilic film 213.
The position of the portion Q in contact with the upper end of 4 is fixed, and only the curvature of the lens upper surface portion (optical action portion) inside the interface 124 inside the lipophilic film 214 changes.

As described above, by applying the voltage to the first liquid 121 and the transparent electrode 103, the two kinds of liquids 121, 1
The balance of the interfacial tension of the two liquids 121 and 1 changes.
The shape of the interface 124 between the two 22 changes.

For this reason, by controlling the voltage applied between the first liquid 121 and the transparent electrode 103 by the power supply circuit 131, an optical element that can freely change the shape (curvature) of the lens upper surface portion of the interface 124 is provided. Can be configured.

Then, the first and second liquids 121, 1
Since the lenses 22 have different refractive indices, optical power (1 / f: f is a focal length) is given as a lens, and the optical element 101 changes the curvature of the upper surface of the lens at the interface 124. Thereby, a variable focus lens whose optical power is variable is obtained.

On the other hand, the shape and size of the effective diameter of the lens and the position of the optical axis 223 are substantially maintained. As a result,
By controlling the voltage of the power supply circuit 131, the lens optical axis 223
It is possible to realize an optical element in which only the curvature (that is, the optical power) changes while keeping the same. That is, the optical axis displacement (eccentricity) of the lens can be reduced.

As described above, according to the present embodiment, by providing the hydrophilic film 213 and (the upper end of) the lipophilic film 2114 as the interface holding portion in the container, the optically active portion (lens) of the interface 124 is provided. The displacement (eccentricity) of the optical axis 223 due to the shape change (curvature change) of the upper surface can be suppressed, and the optical performance of the optical element 201 can be maintained and improved.

In addition, the above effect can be obtained with a simple configuration in which the cylindrical member 228 is disposed in the container, the hydrophilic film 213 is provided at the end, and the lipophilic film 214 is provided on the inner surface.
Cost can be reduced.

Further, by changing the inner diameter of the cylindrical member 228, the effective lens diameter can be freely changed, so that an optical element having a desired effective lens diameter can be easily obtained.

In the present embodiment, the second liquid 122
, The curvature of the optically active portion in a state where no voltage is applied can be determined.

Further, in the optical element of the present invention, as shown in the first and third embodiments, the cylindrical members 128 and 228 for providing the interface holding portions are provided on the first liquid 121 side also on the second liquid 122 side. Since it can be provided on either side, it can be used properly depending on the form of installation.

For example, when miniaturization and thinning are desired,
To reduce the thickness in the direction parallel to the optical axis, the inner surface of the liquid chamber needs to be tapered. For example, if the taper is such that the opening of the upper cover 106> the opening of the transparent substrate 102 side, it is desirable that the cylindrical member 128 be provided on the first liquid 121 side, thereby increasing the size in the direction perpendicular to the optical axis. Can be avoided.

When the taper is reversed,
It is desirable that the cylindrical member 128 be provided on the second liquid side.

[0124]

As described above, according to the present invention,
An interface holding portion is provided in contact with a part of the interface between the first liquid and the second liquid to suppress the displacement of the optical axis of the optically acting portion at the interface. 1
Even if the shape of the interface between the liquid and the second liquid changes, the displacement of the optical axis (that is, eccentricity) of the optically active portion at the interface can be suppressed by the function of the interface holding portion, and the optical element Performance can be maintained.

Moreover, since it is only necessary to provide the interface holding portion in the container, the eccentricity of the optically active portion can be suppressed with a simple configuration.

Further, if the interface holding portion is made to suppress the change of the shape, size and position of the optically acting portion on the plane orthogonal to the optical axis, the optically acting portion can be changed in accordance with a change in applied voltage. Only the curvature changes, and the optical power can be easily controlled while maintaining the effective diameter of the optically active portion.

Further, if the interface holding portion is formed in a shape (especially, an annular shape) in contact with the interface so as to surround the outer periphery of the optical action portion, a spherical surface around the optical axis can be obtained as the optical action portion. it can.

By providing the interface holding portion from the first liquid side to the tip of the member in contact with the interface, the effective diameter of the optically active portion can be freely set without changing the volume of the second liquid. it can.

Further, by providing the interface holding portion from the second liquid side to the tip of the member which is in contact with the interface, the volume of the second liquid is changed so that the curvature of the optically active portion in the state where no voltage is applied is set. It can be performed.

Further, by setting the inner diameter of the interface holding portion to 3 mm or more, it becomes possible to allow the second liquid, such as silicone oil, to smoothly enter the inside of the interface holding portion, thereby more effectively forming the optically active portion. Eccentricity can be suppressed.

By providing the above-described optical element and a power supply control circuit for changing a voltage applied between the first liquid and an electrode provided on the container side, electrowetting can be performed without optical eccentricity. An optical device with variable optical power can be realized by the effect.

Further, by forming a photographing apparatus provided with a photographing optical system including the above-described optical element, it is possible to realize an image pickup apparatus having a variable focal length by the electrowetting effect without optical eccentricity. .

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of an optical element (when no voltage is applied) according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the optical element (when voltage is applied).

FIG. 3 is an explanatory diagram showing a relationship between an applied voltage and an interface deformation amount in the optical element.

FIG. 4 is a configuration diagram of a power supply control circuit that controls a voltage applied to the optical element.

FIG. 5 is an operation explanatory diagram of the power supply control circuit.

FIG. 6 is a configuration diagram of an imaging device (optical device) according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of the photographing apparatus.

FIG. 8 is a sectional view of an optical element according to a third embodiment of the present invention.

FIG. 9 is a sectional configuration diagram of a conventional optical element.

[Explanation of symbols]

 101, 201 Optical element 102 Transparent substrate 103 Transparent electrode 104 Insulating layer 107, 207 Aperture plate 111 Water-repellent film 112 Hydrophilic film 113, 213 Hydrophilic film 114, 214 Lipophilic film 121 First liquid 122 Second liquid 123, 223 Light Shaft 124 Interface 125 Bar-shaped electrode 128,228 Cylindrical member 129,229 Hole 130 CPU 131 Power supply circuit 132 DC power supply 133 DC / DC converter 134,135 Amplifier 140 Imaging optical system 141 First lens group 142 Second lens group 143 Aperture unit 144 Image sensor 145 Image signal processing circuit 150 Imaging device (optical device) 151 Display device 152 Main switch 153a W-side zoom switch 153b T-side zoom switch 154 Operation switch group 155 Focus detection device 156 Focus drive time 157 memory 901 substrate 902,905 electrode 903 insulating layer 904 surface treatment unit 906 silicone oil 907 electrolyte

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Goro Noto 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H041 AA12 AB32 AC06 AZ06 AZ08 2H087 KA03 MA12 RA27 SA11 SA63 SA72 SA74 5C022 AA13 AB21 AB66 AC03 AC42 AC54 AC69

Claims (11)

[Claims] 1. A first liquid having conductivity or polarity and a second liquid which is not mixed with the first liquid are accommodated in a container, and are provided on the side of the first liquid and the container. An optical element whose optical characteristics change by changing the shape of an interface between the first liquid and the second liquid in accordance with a change in applied voltage between the applied electrodes, wherein the interface is provided in the container. An optical element characterized in that an interface holding portion for suppressing displacement of the optical axis of the optically acting portion at the interface is provided in contact with a part of the interface. 2. The apparatus according to claim 1, wherein the interface holding section is in contact with a part of the interface to suppress a change in shape, size, and position of the optically active portion on a plane orthogonal to the optical axis. 2. The optical element according to 1. 3. The optical element according to claim 1, wherein the interface holding portion is in contact with the interface so as to surround an outer periphery of the optically active portion. 4. The optical element according to claim 3, wherein the interface holding section is formed in an annular shape. 5. The optical device according to claim 1, wherein the interface holding section is provided at a tip of a member extending from the first liquid side to a position in contact with the interface. element. 6. The optical device according to claim 1, wherein the interface holding portion is provided at a tip of a member extending from the second liquid side to a position in contact with the interface. element. 7. The interface holding section includes a first adsorbing section having an adsorbing property with respect to the first liquid and a second adsorbing section having an adsorbing property with respect to the second liquid. The optical element according to claim 1, wherein: 8. An aperture member having an aperture formed to allow light incident on the interface to pass therethrough, wherein an inner diameter of the interface holding portion is larger than an aperture diameter of the aperture member. Item 5. The optical element according to item 3 or 4. 9. The optical element according to claim 3, wherein an inner diameter of the interface holding section is 3 mm or more. 10. An optical element according to claim 1, further comprising a power supply control circuit for changing a voltage applied between the first liquid and an electrode provided on the container side. Characteristic optical device. 11. A power supply control circuit for changing a voltage applied between an imaging optical system including the optical element according to claim 1 and an electrode provided between the first liquid and an electrode provided on the container side. An imaging device comprising: