JP4532651B2 - Variable focus lens, optical system and photographing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical element constituting a varifocal lens that controls the refractive power of light passing through an optical system, a so-called variable power lens, and a photographing apparatus using the optical element, and particularly to miniaturization. it can, efficiently with a simple structure can control the optical power, the variable focus lens, a variable focus lens suitable variable focus lens or the like, partially formed by the varifocal lens optics and imaging apparatus It aims at realization.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a photographing optical system used in a photographing apparatus such as a still camera or a video camera requires functions such as focus adjustment or magnification adjustment.
Each of these functions requires an actuator such as a motor and a conversion mechanism that converts the output of the actuator into movement in the direction of the optical axis of a part of the lens.
However, this conversion mechanism has a drawback that a mechanical drive unit is required and the apparatus becomes large or generates sound when operated.
[0003]
In order to eliminate such drawbacks, a variable focus lens using an electrocapillary phenomenon (electrowetting phenomenon) is disclosed in WO99 / 18456. When this technology is used, electric energy can be directly used to change the shape of the lens, so that the focus can be adjusted without mechanically moving the lens.
[0004]
[Problems to be solved by the invention]
However, WO99 / 18456 discloses a technique for making optical power variable by using electrocapillarity (electrowetting phenomenon). However, in the first to fifth embodiments described herein, all of them are disclosed. There is a drawback in that there is a transparent electrode in the transmitted light path, and the amount of light transmitted through the lens is reduced. In all of the first to sixth embodiments, the optical element has a large thickness in the optical axis direction, so there is room for improvement in that it is substantially difficult to incorporate into a civilian device that requires compactness. .
[0005]
Therefore, the present invention provides a variable focus lens having a structure that can efficiently control the lens power with a small configuration by solving the above-described problems and utilizing the electrowetting phenomenon. It is an object of the present invention to provide an optical system and a photographing apparatus configured by a variable focus lens .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a variable focus lens configured as in the following (1) to ( 8 ), an optical system and a photographing apparatus partially configured by the variable focus lens. is there.
(1) A container in which the first liquid and the second liquid are sealed, each having a different refractive index and having conductivity or polarity that does not mix with each other;
A first electrode provided to be electrically connected to the first liquid and formed at a site that does not hinder the passage of incident light;
Side surfaces with respect to the incident and exit surfaces are inclined with respect to the optical axis so that the light exit surface that is insulated from the first electrode and the first liquid and faces the light incident surface is narrowed. A second electrode provided on the side surface of the container and inclined in the same direction as the inclination of the side surface;
The first and second liquids are formed so that the convex direction of the R-shaped interface formed at the interface between these liquids faces the direction of the light exit surface, and the second electrode in the container is Sealed to the container in such a way that there is an intersection between the containing side surface and the interface between the liquids ,
The refractive power of light passing therethrough is changed by changing the shape of the interface between the first liquid and the second liquid by controlling the output of the voltage applied by the first electrode and the second electrode. A variable focus lens characterized by that.
(2) The variable focus lens according to (1), wherein the second electrode is a ring-shaped electrode and is disposed so as to surround the second liquid.
(3) the optical path length on the optical axis of the optical path length and the second liquid on the optical axis of the first liquid, above, characterized in that changes in accordance with output of the applied voltage (1) or ( The variable focus lens according to 2) .
( 4 ) The refractive index of the first liquid is smaller than the refractive index of the second liquid, and the optical path length of the first liquid in the optical axis direction increases according to the distance from the optical axis. The variable focus lens according to any one of (1) to ( 3 ), wherein
( 5 ) The refractive index of the first liquid is smaller than the refractive index of the second liquid, and the optical path length on the optical axis of the first liquid varies between finite dimensions according to the output of the applied voltage. The varifocal lens according to any one of (1) to ( 3 ), wherein the varifocal lens changes.
( 6 ) The variable focus lens according to any one of (1) to ( 5 ), wherein the optical surface of the container in which the solution exists is a curved surface.
( 7 ) In an optical system in which a predetermined image is formed or condensed by a lens element, a part of the optical system is configured by the variable focus lens according to any one of (1) to ( 6 ). An optical system characterized by that.
( 8 ) An imaging apparatus comprising the optical system of ( 7 ) above.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The optical element or the photographing apparatus disclosed in the present embodiment uses the above-described configuration, so that an optical system and a photographing apparatus in which an optical element suitable for a compact variable focal length apparatus or an automatic focusing apparatus is built in a lens element. Can be realized.
For example, by using the configurations (1) to (12) described above, by providing the electrode on a surface through which light does not pass, the optical power of the first and second liquids is changed by the change in the interface shape by the output control of the applied voltage. In controlling the change, it becomes possible to improve the light transmittance and to construct an efficient optical element, and to seal the liquid in the container in a state where the thickness of the liquid in the optical axis direction is reduced. Compactness can be achieved.
[0008]
By the way, the above-described configuration is based on the principle configuration of the optical element (Japanese Patent Application No. 11-169657) by the present applicant that can control the amount of transmitted light by using the electrocapillary phenomenon (electrowetting phenomenon). Is an improvement. Therefore, since the above-described configuration is based on this principle configuration, for the purpose of understanding the details, first, this principle configuration will be described with reference to FIG.
[0009]
FIG. 5 and FIG. 6 are diagrams for explaining the principle configuration of the above-described optical element in which the amount of transmitted light can be controlled using the electrocapillary phenomenon (electrowetting phenomenon).
In FIG. 5, reference numeral 101 denotes an overall configuration of an optical element for explaining the above-described principle configuration, and 102 is a transparent acrylic transparent substrate having a recess at the center. 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 in close contact with the upper surface. The insulating layer 104 is formed by dropping a replica resin onto the center of the transparent electrode 103 and pressing it with a glass plate to smooth the surface, and then irradiating with UV irradiation and curing. A cylindrical container 105 having a light-shielding property is bonded and fixed to the upper surface of the insulating layer 104, and a cover plate 106 made of transparent acrylic is bonded and fixed to the upper surface. Further, the upper surface has a diameter D3 at the center. A diaphragm plate 107 having an opening is disposed. In the above configuration, a sealed space having a predetermined volume surrounded by the insulating layer 104, the container 105, and the upper cover 106, that is, a casing having a liquid chamber is formed. And the following surface treatment is given to the wall surface of a liquid chamber.
[0010]
First, a water repellent treatment agent is applied within the range of the diameter D1 to form a water repellent film 111 on the central upper surface of the insulating layer 104. The water repellent treatment agent is preferably a fluorine compound or the like. In addition, a hydrophilic treatment agent is applied to a range outside the diameter D1 on the upper surface of the insulating layer 104, and a hydrophilic film 112 is formed. As the hydrophilic agent, a surfactant, a hydrophilic polymer and the like are suitable. On the other hand, a hydrophilic film 113 having the same properties as the hydrophilic film 112 is formed on the lower surface of the cover plate 106 within the range of the diameter D2. All the constituent members described so far have a rotationally symmetric shape with respect to the optical axis 123. Further, a hole is formed in a part of the container 105, and a rod-shaped electrode 125 is inserted therein and sealed with an adhesive to maintain the sealing property of the liquid chamber. A power feeding 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.
[0011]
The liquid chamber having the above configuration is filled with the following two types of liquids. First, a predetermined amount of the second liquid 122 is dropped on the water repellent film 111 on the insulating layer 104. The second liquid 122 is colorless and transparent, and silicon oil having a specific gravity of 1.06 and a refractive index of 1.49 at room temperature is used. On the other hand, the remaining space in the liquid chamber is filled with the first liquid 121. The first liquid 121 is an electrolytic solution 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 sodium chloride is added. That is, as the first and second liquids, liquids having the same specific gravity and insoluble in each other are selected. Therefore, both liquids form an interface 124, and they exist independently without being mixed.
[0012]
Next, the shape of the interface will be described. First, when no voltage is applied to the first liquid, the shape of the interface 124 includes the interface tension between the two liquids and the interface tension between the first liquid and the water-repellent film 111 or the hydrophilic film 112 on the insulating layer 104. It is determined by the interfacial tension between the second liquid and the water repellent film 111 or the hydrophilic film 112 on the insulating layer 104 and the volume of the second liquid. In this embodiment, the material is selected so that the interfacial tension between the silicon oil that is the material of the second liquid 122 and the water repellent film 111 is relatively small. That is, since the wettability between the two materials is high, the outer edge of the lenticular droplet formed by the second liquid 122 has a tendency to spread, and is stabilized when the outer edge coincides with the application region of the water repellent film 111. That is, the diameter A1 of the bottom surface of the lens 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 the radius of curvature and the height h 1 are determined by the volume of the second liquid 122. Further, the thickness of the first liquid on the optical axis is t1.
[0013]
On the other hand, 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 decreases due to the electrocapillary phenomenon, and the first liquid becomes a hydrophilic film. Overcoming the boundary between 112 and the hydrophobic film 122 and entering the hydrophobic film 122. As a result, as shown in FIG. 6, the diameter of the bottom surface of the lens made by the second liquid decreases from A1 to A2, and the height increases from h1 to h2. Further, the thickness of the first liquid on the optical axis is t2. In this way, by applying a voltage to the first liquid 121, the balance of the interfacial tension between the two liquids changes, and the shape of the interface between the two liquids changes.
[0014]
Therefore, an optical element in which the shape of the interface 123 can be freely changed by voltage control of the power feeding means 126 can be realized. Also. Since the first and second liquids have different refractive indexes, power as an optical lens is applied, so that the optical element 101 becomes a variable focus lens due to the shape change of the interface 123. .
[0015]
Furthermore, since the radius of curvature of the interface 124 of FIG. 6 is shorter than that of FIG. 5, the optical element 101 in the state of FIG. 6 has a shorter focal length of the optical element 101 than that of FIG. .
[0016]
FIG. 7 is a diagram for explaining the relationship between the output voltage of the power feeding means 126 of the present invention and the deformation of the optical element 101.
In FIG. 7A, when a voltage having a voltage value V ₀ is applied to the optical element 101 at time t ₀ , the deformation of the interface 124 of the optical element 101 starts with a time constant t ₁₁ (see FIG. 7B). ). Even if the voltage application is controlled as it is, a considerably long time is required until the interface 124 reaches the desired change amount δ ₀ . Therefore, when the interface 124 is deformed to an allowable amount as an error for the optical system, for example, 95% of the desired interface change amount δ ₀ (denoted as 0.95δ _{0 in} FIG. 7B) (time t _12). ) Is considered to have reached the desired amount of deformation. If the amount of deformation is not reached, the next control of the optical element 101 is set not to proceed. The allowable deformation amount is determined based on the optical system in which the optical element 101 is incorporated.
[0017]
FIG. 8 and FIG. 9 are explanatory views of the power supply means related to the optical element in the above-described principle configuration and the variable focus lens of Example 1 of the present invention to be described later, and FIG. 8 is a diagram showing a drive circuit suitable for them. FIG. 9 is a diagram showing drive voltages for these.
The configuration and creation method of the power supply means will be described with reference to FIGS.
Reference numeral 130 denotes a central processing unit (hereinafter abbreviated as CPU) that controls the operation of the entire optical device 150, which will be described later. ROM, RAM, EEPROM, A / D conversion function, D / A conversion function, PWM (Pulse Width Modulation) function It is a one-chip microcomputer having. Reference numeral 131 denotes power supply means for applying a voltage to the optical element 101, and the configuration thereof will be described below.
[0018]
132 is a DC power source such as a dry battery incorporated in the optical device 151, 133 is a DC / DC converter that boosts the voltage output from the power source 132 to a desired voltage value according to a control signal of the CPU 130, and 134 and 135 are This is an amplifier that amplifies the signal level to a voltage level boosted by the DC / DC converter 133 in accordance with a control signal of the CPU 130, for example, a frequency / duty ratio variable signal for realizing the 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, the output voltage of the power supply 132 is applied to the optical element 101 at a desired voltage value, frequency, and duty by the DC / DC converter 133, the amplifier 134, and the amplifier 135 according to the control signal of the CPU 130.
[0019]
FIG. 9 is a diagram for explaining voltage waveforms output from the amplifiers 134 and 135. In the following description, it is assumed that a voltage of 100 V is output from the DC / DC converter 133 to the amplifiers 134 and 135, respectively.
As shown in FIG. 9A, the amplifiers 134 and 135 are connected to the optical element 101, respectively. As shown in FIG. 9B, the amplifier 134 outputs a voltage having a rectangular waveform with a desired frequency and duty ratio in accordance with a control signal from the CPU 130. On the other hand, as shown in FIG. 9C, the amplifier 135 outputs a rectangular waveform voltage having the same frequency and the same duty ratio as the amplifier 134 in accordance with the control signal of the CPU 130. As a result, the voltage applied between the transparent electrode 103 and the rod-shaped electrode 125 of the optical element 101 becomes a voltage having a rectangular waveform of ± 100 V, that is, an alternating voltage as shown in FIG.
[0020]
Therefore, an AC voltage is applied to the optical element 101 by the power supply means 131. Incidentally, since the effective value from the start of application of the voltage applied to the optical element 101 can be expressed as shown in FIG. 9E, the waveform of the AC voltage applied to the optical element 101 is shown in FIG. It will be expressed following.
In the above description, it has been described that a rectangular waveform voltage is output from the amplifiers 134 and 135, but it goes without saying that a sine wave has the same configuration.
In the above description, the case where the power source 132 is incorporated in the optical device 150 has been described. However, an AC power may be applied to the optical element 101 by an external power source or a power feeding unit.
[0021]
FIG. 10 shows the optical element 101 applied to an optical apparatus. In the present embodiment, the optical device 150 will be described by taking as an example a so-called digital still camera in which a still image is photoelectrically converted into an electrical signal by a photographing means and recorded as digital data.
Reference numeral 140 denotes a photographing optical system composed of a plurality of lens groups, and includes a first lens group 141, a second lens group 142, and an optical element 101. Focus adjustment is performed by the advance and retreat of the first lens group 141 in the optical axis direction. Zooming is performed by changing the power of the optical element 101. 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 a diaphragm aperture diameter is adjusted between the first lens group 141 and the optical element 101 by a known technique. A diaphragm unit 143 for adjusting the amount of light flux is disposed.
An imaging unit 144 is disposed at the focal position (planned imaging plane) of the photographing optical system 140. This is a photoelectric conversion means such as a two-dimensional CCD comprising a plurality of photoelectric conversion units for converting irradiated light energy into charges, a charge storage unit for storing the charges, and a charge transfer unit for transferring the charges and sending them to the outside. Is used.
[0022]
An image signal processing circuit 145 performs A / D conversion on the analog surface image signal input from the imaging unit 144 and performs image processing such as AGC control, white balance, γ correction, and edge enhancement. A temperature sensor 146 measures the environmental temperature (air temperature) of the optical device 150. Reference numeral 147 denotes a timer provided in the CPU 130 for counting the time set by the CPU 130.
[0023]
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 apparatus having a variable focus lens. Reference numeral 152 denotes a main switch for starting the CPU 130 from the sleep state to the program execution state, and reference numeral 153 denotes a zoom switch. The zoom switch performs a scaling operation described later according to the zoom switch operation of the photographer, thereby changing the focal length of the photographing optical system 140. 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 a shutter speed, and the like. Reference numeral 155 denotes a focus detection unit, which is preferably a phase difference detection type focus detection unit used in a single-lens reflex camera. A focus driving unit 156 includes an actuator and a driver circuit for moving the first lens group 141 back and forth in the optical axis direction. The focus driving unit 156 performs a focusing operation based on the focus signal calculated by the focus detection unit 155 to Adjust the condition. Reference numeral 157 denotes memory means for recording a photographed image signal. Specifically, a detachable PC card type flash memory or the like is preferable.
[0024]
FIG. 11 is a control flow chart of the CPU 130 included in the optical device 150 shown in FIG. Hereinafter, the control flow of the optical device 150 will be described with reference to FIGS. 10 and 11.
In step S101, it is determined whether or not the main switch 152 has been turned on. When the main switch 152 has not been turned on, the standby mode is awaiting the operation of various switches. If it is determined in step S101 that the main switch 152 is turned on, the standby mode is canceled, and the process proceeds to the next step S102 and subsequent steps.
In step S102, the temperature sensor 146 measures the ambient temperature where the optical device 150 is placed, that is, the ambient temperature around the optical device 150.
In step S103, the setting of the photographing condition by the photographer is accepted. For example, setting of exposure control mode (shutter priority AE, program AE, etc.), surface quality mode (number of recorded surface primes, image compression rate, etc.), strobe mode (forced flash, flash emission prohibited, etc.) Do.
In step S104, it is determined whether the zoom switch 153 has been operated by the photographer. If it is not turned on, the process proceeds to step S105. When the zoom switch 153 is operated here, the process proceeds to step S121.
[0025]
In step S121, it is determined whether the timer 147 is counting. If not counting, the process proceeds to step S123. If the counting is being performed, the counter value is reset (S122), and then the process proceeds to step S123.
[0026]
In step S123, the operation amount (operation direction, on-time, etc.) of the zoom switch 153 is detected, and the corresponding focal length change amount is calculated based on the operation amount (S124). Based on the calculation result, the final applied voltage value V ₀ to the optical element 101 is determined (S125), and the process proceeds to a “temperature correction” subroutine for correcting the final voltage value by temperature and determining the voltage application waveform (see FIG. 12). Details will be described later). The power supply means 131 is controlled by the final voltage value and the applied waveform pattern applied to the optical element 101 determined in the “temperature correction” subroutine, and a voltage is applied to the optical element 101 (S127). At the same time, the timer 147 starts counting (S128). Then, the process returns to step S103. That is, when the zoom switch 153 is continuously operated, Steps S103 to S128 are repeatedly executed, and the process proceeds to Step S105 when the zoom switch 153 is turned on.
[0027]
In step S105, it is determined whether or not the photographer has turned on the photographing preparation switch (denoted as SW1 in the flowchart of FIG. 11) in the operation switch group 154. If the on-operation has not been performed, the process returns to step S103, and reception of shooting condition settings and determination of the operation of the zoom switch 153 are repeated. If it is determined in step S105 that the shooting preparation switch has been turned on, the process proceeds to step S111.
[0028]
In step S111, the imaging unit 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 condition of the final recording surface image and to allow the photographer to grasp the photographing composition.
In step S112, the light reception level of the preview image acquired in step S111 is recognized. Specifically, the highest, lowest and average output signal levels are calculated in the image signal output by the imaging unit 144, and the amount of light incident on the imaging unit 144 is recognized.
In step S113, based on the amount of received light recognized in step S112, the aperture unit 143 provided in the photographing optical system 140 is driven to adjust the aperture diameter of the aperture unit 143 so that an appropriate amount of light is obtained.
In step S114, the preview image acquired in step S111 is displayed on the display 151. In step S115, the focus detection unit 154 is used to detect the focus state of the photographing optical system 140. In step S116, the focus driving unit 155 moves the first lens group 141 back and forth in the optical axis direction to perform a focusing operation. Thereafter, the process proceeds to step S117, and it is determined whether or not the photographing switch (denoted as SW2 in the flow chart 11) is turned on. When the on-operation is not performed, the process returns to step S111, and steps from acquisition of the preview surface image to focus driving are repeatedly executed.
[0029]
As described above, when the photographer turns on the photographing switch while the photographing preparation operation is repeatedly executed, it is determined whether or not the timer 147 has been counted (S118). If the count is not completed, the determination is continued as it is, and when the count of the timer 147 is completed, the process jumps from step S118 to step S131, resets the count value of the timer 147 (S131), and proceeds to step S132. To do.
[0030]
In step S132, imaging is performed. That is, the subject image formed on the image pickup unit 144 is photoelectrically converted, and charges proportional to the intensity of the optical image are accumulated in the charge accumulating unit near each light receiving unit. In step S133, the charge accumulated in step S132 is read through the charge transfer line, and the read analog signal is input to the signal processing circuit 145. In step S134, the signal processing circuit 145 performs A / D conversion on the input analog image signal, performs image processing such as AGC control, white balance, γ correction, and edge enhancement, and is stored in the CPU 130 as necessary. JPEG compression or the like is performed using the image compression program. In step S135, the image signal obtained in step S134 is recorded in the memory 157. At the same time, the preview image is once erased in step S136, and then the image signal obtained in step S134 is displayed again on the display 151. Thereafter, the power supply means 131 is controlled to turn off the voltage application to the optical element 101 (S137), and a series of photographing operations is completed.
[0031]
In step S151, it is determined whether or not the temperature measured by the temperature sensor 146 is 15 ° C. or higher. When the temperature is 15 ° C. or lower, the voltage application waveform A shown in FIG. 9A is selected (S152). As described above, the time until the interface is completely deformed is increased because the viscosity of the liquids 121 and 122 in the optical element 101 is increased at a low temperature. By applying a voltage higher than the final voltage reference value V _{0, the} amount of deformation of the interface at the time of startup is increased, thereby shortening the interface deformation completion time.
This is because the first voltage applied to the optical element 101, that is, a predetermined time before applying the final voltage reference value V ₀ (hereinafter referred to as pre-application time) is higher than the final voltage reference value V ₀ . , That is, a pre-voltage value V ₁ is applied to the optical element 101, and after the pre-application time has elapsed, a final voltage reference value V ₀ is applied to the optical element 101.
When the measured temperature is 10 ° C. or higher and lower than 15 ° C. (S153), the pre-application time is set to 0 ms (S154), and the process proceeds to S180 for calculating the pre-voltage value V ₁ .
[0032]
When the measured temperature is 5 ° C. or higher and lower than 10 ° C. (S155), the pre-application time is set to 10 ms (S156), and the process proceeds to S180 for calculating the pre-voltage value V ₁ .
When the measured temperature is 0 ° C. or higher and lower than 5 ° C. (S160), the pre-application time is set to 20 ms (S156), and the process proceeds to S180 for calculating the pre-voltage value V ₁ .
When the measured temperature is less than 0 ° C. (S160), the pre-application time is set to 30 ms (S156), and the process proceeds to S180 for calculating the pre-voltage value V ₁ .
The pre-voltage value V ₁ calculated in step S180 is obtained by the following equation, for example.
Pre-voltage value V ₁ = (correction constant 1) × (reference temperature−measured temperature) (1-1) In other words, the value obtained by multiplying the temperature difference from the reference temperature and 15 ° C. by (correction constant 1) The voltage value is V ₁ .
[0033]
After the pre-voltage value V ₁ is obtained, the process proceeds to step S181 to calculate the correction amount of the final voltage reference value V ₀ and obtain the final voltage application time. Although the final voltage reference value V ₀ is obtained in step S125, for example, correction represented by the following equation is performed.
Corrected final voltage value V ₀ ′ = (final voltage reference value V ₀ ) + (correction constant 2) × (reference temperature−measured temperature) (1-2) Equation, that is, the final voltage reference value obtained in step S125 The corrected final voltage value V ₀ ′ is obtained by adding a value obtained by multiplying V ₀ by the temperature difference from the reference temperature of 15 ° C. (correction constant 2).
By performing the above control, the applied voltage waveform is finely changed according to the temperature as shown in FIG. 9A. As a result, the response waveform at the interface is almost independent of the temperature as shown in FIG. fixed and will, time t ₃₂ Deho if the deformation is completed. Therefore the latency timer 147 which is a measure of the deformation completed slightly longer T _A from t _32, and stored in this pre CPUl30 in memory. Then, by the T _A and determined value of the timer completes in step S118 of FIG. 7, the interface is executed from the settling in step S131 and subsequent flow is admitted.
[0034]
On the other hand, if the measured temperature is 15 ° C. or higher in step S151, the voltage application waveform B shown in FIG. 9B is selected (S170). This is because, as described above, the vibration phenomenon occurs until the interface is completely deformed due to the low viscosity of the liquids 121 and 122 in the optical element 101 at a high temperature. By applying a voltage up to a predetermined final voltage reference value V ₀ , the vibration phenomenon of the interface at the start-up is suppressed.
That is, a waveform pattern for performing voltage control so that a predetermined time (also referred to as pre-application time) before applying the final voltage reference value V ₀ applied to the optical element 101 gradually becomes the final voltage reference value V _0. is there.
[0035]
When the measured temperature is 15 ° C. or higher and lower than 20 ° C. (S171), the pre-application time is set to 10 ms (S172), the corrected final voltage value V ₀ ′ is calculated, and the process proceeds to step S181 for obtaining the final voltage application time. move on.
When the measured temperature is 20 ° C. or higher and lower than 30 ° C. (S173), the pre-application time is set to 20 ms (S174), the corrected final voltage value V ₀ ′ is calculated, and the process proceeds to step S181 for obtaining the final voltage application time. move on.
If the measured temperature is 30 ° C. or higher (S173), the pre-application time is set to 30 ms (S175), the corrected final voltage value V ₀ ′ is calculated, and the process proceeds to step S181 for obtaining the final voltage application time.
[0036]
By performing the above control, the applied voltage waveform is finely changed according to the temperature as shown in FIG. 9B. As a result, the response waveform of the interface is almost independent of the temperature as shown in FIG. constant and becomes substantially deformation is completed at time t _42. Therefore the latency timer 147 which is a measure of the deformation completed, slightly longer T _B from t _42, and stored in this pre-CPU130 in memory. Then, by the T _B and determined value of the timer completes in step S118 of FIG. 7, the interface is executed from the settling in step S131 and subsequent flow is admitted.
[0037]
Thus, the final applied voltage value and the voltage applied waveform pattern corresponding to the temperature are determined (S182), and the process returns to step S127.
Further, by controlling the final applied voltage value and the voltage applied waveform pattern according to the temperature, it becomes possible to perform optimum drive control for each temperature.
[0038]
According to Example 1 above,
(1) It is possible to obtain an optical device capable of shortening the deformation completion time of the optical element by controlling the final applied voltage value and the voltage application waveform pattern to the optical element according to the temperature.
(2) Since the time for actually driving the optical element can be shortened, the power consumption of the optical device can be reduced.
(3) Since the exposure is prohibited until the deformation of the optical element is settled, the influence on the photographing operation of the optical device is eliminated.
Etc. are achieved.
[0039]
In this embodiment, the reference temperature for switching the voltage application waveform pattern is set to 15 ° C., and the pre-application time is set for each temperature. A similar effect can be obtained by setting the pre-application time.
Further, although the voltage application to the optical element is made in two stages, the same effect can be obtained even if the voltage is applied in more stages.
Further, the correction amount of the final applied voltage value and the pre-applied voltage value for each temperature is obtained by calculation. For example, as shown in FIG. 10, a table determined by the temperature of the desired focal length is stored in the CPU. Even if it is used as each correction amount, the same effect as in this embodiment can be obtained.
In this embodiment, a digital still camera is taken as an example of an optical apparatus, but it goes without saying that the present invention can be applied to other video cameras, silver halide cameras, and the like without impairing the effect.
[0040]
【Example】
Examples of the present invention will be described below.
[Example 1]
The principle of the configuration of the optical element constituting the variable focus lens used in the optical system of Example 1 of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 7 denotes a container sealed with the following liquid, which is the same as described in the principle diagram, and is made of an insulator. In the drawing, the horizontal direction (light incident / exit direction) is made transparent. .
8 is the 2nd liquid sealed by the container 7, and is comprised here with transparent silicone oil. Reference numeral 9 denotes an electrolytic solution such as water in which salt is dissolved in a transparent first liquid having a refractive index lower than that of the second liquid sealed in the container 7.
Reference numeral 10 denotes an electrode for applying an electric potential to the electrolytic solution 9 from the outside and is connected to a control circuit (not shown), and an alternating electric field of about plus or minus 200 V as described above is applied.
[0041]
Reference numeral 11 denotes a ring-shaped second electrode embedded in an insulator, which is also connected to a control circuit (not shown). The above-described positive and negative AC electric fields of about 200 V are opposite in polarity to the electrode 10 described above. It is applied with the phase.
Reference numeral 12 denotes a light beam. In the state shown in FIG. 1A, when the light enters the first liquid 9 from the second liquid 8, it is refracted and condensed at the interface due to the difference in refractive index. In the applied state (b), the first liquid 9 which is an electrolysis liquid pushes the first liquid 8 such as silicon oil in the vicinity of the ring-shaped electrode 11, thereby further increasing the convexity of the interface between the two liquids. Thus, the light collecting property of the emitted light 13 is increased. That is, the optical element in FIG. 1 is changed to a lens having a short focal length.
[0042]
In the above configuration, as described above, when a control circuit (not shown) starts alternating current energization to the electrodes 10 and 11 in order to adjust the focus of the camera or change the magnification from the non-energized state of FIG. ), The focal length is shorter. Since this is related to the voltage applied to the electrodes 10 and 11, an arbitrary focal length can be set.
[0043]
In this embodiment, the above optical element is used, focus adjustment and magnification change are performed, for example, the lens 101 is configured as shown in FIG. 10, and an optical system capable of achieving miniaturization and high performance is provided. Can be configured.
[0044]
2B and 2C show the configuration of the optical element in Example 1 of the present invention. Compared to the principle diagram shown in FIG. 1 and the one shown again in FIG. 2 (a), the liquid can be sealed in the container in a state where the thickness in the direction of the optical axis is further reduced, thereby further reducing the size. It is designed to be able to plan.
[0045]
FIG. 2A is a diagram based on the same principle configuration as FIG. 1, but at this time, paying attention to a point P that is the intersection of the two liquids of the side surface of the container and the first liquid and the second liquid, these two liquids The interface state is generated in the direction of the tangent line ψ of the boundary surface of this electrode, and when the electrodes 10 and 11 are energized from this state, the state of the interface, ψ changes in the increasing direction (where θ is a so-called contact angle and ψ = 90 [deg.]-[Theta].
[0046]
Paying attention to the thickness d of the unit, it can be seen that the thickness d ′ of the unit of this embodiment can be made smaller (thinner) if the configuration is such that ψ approaches zero.
For this reason, a thin unit can be formed as shown in FIG. 2 (b) by inclining the side surface of the container by an angle ψ and configuring it like 7b.
Here, FIG. 3 shows an enlarged view of the point P in FIG. In FIG. 3, t indicates the thickness on the aqueous solution side, and t = 0.1 to 0.5 mm is a suitable condition that achieves both light shielding properties and unit compactness.
Further, ψ is configured so that the interface between the two liquids has a large R shape as shown in the figure at an angle that matches the contact angle determined by the side surfaces of the two solutions and the container as shown in FIG. The electrode 11 is, for example, about 10 to 30 μm so as to incline by δ, which is a very slight angle from the side surface of the container, and as close as possible to the inside of the container.
In addition, the inner surface of the container indicated by a broken line in the drawing is subjected to a known water repellent treatment in advance to repel the aqueous solution 9.
[0047]
With the configuration as described above, the energization from the amplifiers 134 and 135 shown in FIG. 8 described above deforms the interface between the two liquids as shown in FIG. It plays the role of a focusing device that passes through. As described above, the convex size at this time, that is, the focal length of the lens or the lens power is approximately proportional to the voltage from the amplifiers 134 and 135 described above.
[0048]
[Example 2]
FIG. 4 shows the configuration of a variable focus lens according to Example 2 of the present invention. The variable focus lens formed using the basic configuration according to Example 1 is incorporated in a lens element. .
FIG. 4 (a) shows a state where the interface between the two liquids does not affect the light transmitted through the variable focus lens in a non-energized state, and FIG. 4 (b) applies an electric field as described above from FIG. 4 (a). 4 shows a state in which the focal length of the lens in FIG. 4 is changed by changing the interface between the two liquids.
[0049]
In the state of FIG. 4B, R at the interface between the second liquid 8 having a higher refractive index and the first liquid 9 having a lower refractive index is smaller than in the state of (a) where the same voltage as in the above example is not applied. In addition, the focal length of the entire lens shown in the figure is shorter, that is, the power changes strongly, and the focus adjustment function is achieved.
[0050]
In the present embodiment, a variable focus structure is incorporated in the lens function as compared with the first embodiment, so that a more compact unit can be realized in total.
[0051]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a variable focus lens capable of efficiently controlling the focus adjustment or zooming of the lens system with a simple configuration by utilizing the electrowetting phenomenon. it is possible, furthermore, it is possible to realize a compact optical system and imaging device by the variable focus lens.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration principle of an optical element used in an optical system according to Example 1 of the present invention.
FIG. 2 is a diagram showing a configuration of an optical element in Example 1 of the present invention.
FIG. 3 is a diagram showing a configuration in which a point P portion in FIG. 2 is enlarged.
FIG. 4 is a diagram showing a configuration of a variable focus lens in Example 2 of the present invention.
FIG. 5 is a diagram for explaining a principle configuration of an optical element that can control a variable focus lens by using an electrocapillary phenomenon (electrowetting phenomenon).
FIG. 6 is a diagram for explaining the principle configuration of an optical element that can control a variable focus lens by using an electrocapillary phenomenon (electrowetting phenomenon).
7 is a diagram illustrating the relationship between the output voltage of the power feeding means and the deformation of the optical element when a voltage is applied to the optical element of FIG. 6 or the lens of the present embodiment.
FIG. 8 is a diagram showing a driving circuit suitable for an optical element having the above-described principle configuration and a variable focus lens in an embodiment of the present invention.
FIG. 9 is a diagram showing drive voltages for the optical element having the above-described principle configuration and a variable focus lens in an embodiment of the present invention.
FIG. 10 is a system diagram when the optical element having the above-described principle configuration and the variable focus lens in the embodiment of the present invention are applied to an optical device.
FIG. 11 is a flowchart when applied to the optical device.
FIG. 12 is a flowchart when applied to the optical device.
FIG. 13 is a diagram showing the temperature correction operation of the variable focus lens of the present invention.
14 is a diagram showing a table in the microcomputer when the temperature is corrected in FIG. 13; FIG.
[Explanation of symbols]
7 ... Optical element container 8 ... Oil such as silicon oil 9 ... Aqueous solution mixed with carbon particles (electrolyte)
DESCRIPTION OF SYMBOLS 10 ... Electrode terminal 11 ... Ring-shaped electrode 12 ... Incident light 13 ... Emission light 101 ... Optical element 102 ... Transparent substrate 103 ... Transparent electrode 104 ... Insulating layer 105 ... Container 106 ... Upper cover 107 ... Diaphragm 111 ... Water repellent film 112 ... Hydrophilic film 113 ... Hydrophilic film 121, 421 ... First liquid 122, 422 .... Second liquid 123 ... Optical axis 124 ... Interface 125 ... Bar electrode 126 ... Power supply means 130 ... CPU
131 ... Power supply means 132 ... Power supply 134, 135 ... Amplifier 140 ... Shooting optical system 141 ... First lens group 142 ... Second lens group 143 ... Aperture unit 144 ... Image pickup means 145 ... image signal processing circuit 146 ... temperature sensor 147 ... timer 150 ... optical device 151 ... display 152 ... main switch 153 ... zoom switch 154 ... Operation switch group 155 ... focus detection means 156 ... focus drive means 157 ... memory means

Claims (8)

A container having a first liquid and a second liquid hermetically sealed, having different refractive indices and having conductivity or polarity that do not mix with each other;
A first electrode provided to be electrically connected to the first liquid and formed at a site that does not hinder the passage of incident light;
Side surfaces with respect to the incident and exit surfaces are inclined with respect to the optical axis so that the light exit surface that is insulated from the first electrode and the first liquid and faces the light incident surface is narrowed. A second electrode provided on the side surface of the container and inclined in the same direction as the inclination of the side surface;
The first and second liquids are formed so that the convex direction of the R-shaped interface formed at the interface between these liquids faces the direction of the light exit surface, and the second electrode in the container is Sealed to the container in such a way that there is an intersection between the containing side surface and the interface between the liquids ,
The refractive power of light passing therethrough is changed by changing the shape of the interface between the first liquid and the second liquid by controlling the output of the voltage applied by the first electrode and the second electrode. A variable focus lens characterized by that.   The variable focus lens according to claim 1, wherein the second electrode is a ring-shaped electrode and is disposed so as to surround the second liquid. The optical path length on the optical axis of the optical path length and the second liquid on the optical axis of the first liquid, according to claim 1 or claim 2, characterized in that changes in accordance with output of the applied voltage Variable focus lens. The refractive index of the first liquid is smaller than the refractive index of the second liquid, and the optical path length of the first liquid in the optical axis direction increases according to the distance from the optical axis. The variable focus lens of any one of Claims 1-3 . The refractive index of the first liquid is smaller than the refractive index of the second liquid, and the optical path length on the optical axis of the first liquid varies between finite dimensions according to the output of the applied voltage. The variable focus lens according to any one of claims 1 to 3 . Variable focus lens according to any one of claims 1 to 5, characterized in that it has a curved optical surface of the container in the presence of said solution. An optical system in which a predetermined image is formed or condensed by a lens element, wherein a part of the optical system is configured by the variable focus lens according to any one of claims 1 to 6. Optical system. A photographing apparatus comprising the optical system according to claim 7 .

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