JP2007333975A - Liquid lens and optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient liquid lens by lowering the reflectivity at a boundary between a first liquid and a second liquid. <P>SOLUTION: The liquid lens (120) includes the first liquid (1), the second liquid (2), and a first layer (13). The second liquid has a refractive index different from that of the first liquid. The first layer has the refractive index between the refractive index of the first liquid and the refractive index of the second liquid and is provided between the first liquid and the second liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid lens and an optical apparatus using the liquid lens.

Conventionally, an optical system has been proposed in which a liquid lens is configured by filling a container with two types of liquids having different refractive indices, and the interface shape of the liquid is changed by applying a voltage, thereby using the varifocal lens. . An example of the above optical system is disclosed in Patent Document 1.
JP 2001-515539 A

However, in the conventional liquid lens, if the refractive index of the entire liquid lens is increased by increasing the difference between the refractive index of the first liquid and the refractive index of the second liquid, the first liquid and the second liquid There is room for improvement in that the reflectance with respect to the incident light beam becomes large at the interface with the liquid.
An object of this invention is to provide the liquid lens which made the reflectance in the interface of a 1st liquid and a 2nd liquid small.

The liquid lens of the first invention includes a first liquid, a second liquid, and a first layer. The second liquid has a refractive index different from that of the first liquid. The first layer has a refractive index between the refractive index of the first liquid and the refractive index of the second liquid, and is provided between the first liquid and the second liquid.
In a second aspect based on the first aspect, the first layer is provided separately from the first liquid and the second liquid.

According to a third aspect, in the first or second aspect, the first layer has fluidity.
In a fourth invention according to any one of the first to third inventions, the first layer includes any one of a viscous material, a liquid, a polymer film, and a polymer particle.
In a fifth aspect based on any one of the first to fourth aspects, the first liquid, the second liquid, and the first layer are arranged along the optical axis of the incident light.

In a sixth aspect based on any one of the first to fifth aspects, the first layer serves as an antireflection film for incident light flux.
In a seventh invention according to any one of the first to sixth inventions, when the wavelength of incident light is λ and the refractive index of the first layer is n, the thickness of the first layer is λ / ( 4n).
In an eighth aspect based on any one of the first to seventh aspects, the first layer has an affinity for at least one of the first liquid and the second liquid.

  An optical apparatus according to a ninth aspect uses the liquid lens according to any one of the first to eighth aspects.

  ADVANTAGE OF THE INVENTION According to this invention, the highly functional liquid lens which made small the reflectance in the interface of a 1st liquid and a 2nd liquid can be provided.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
(Description of liquid lens)
1 to 3 are explanatory views showing the operation of the liquid lens of the present embodiment. FIG. 1 shows a state in which the liquid lens is cut horizontally with the optical axis direction.
The liquid lens 120 shown in FIG. 1 includes a conductive liquid 1, a dielectric liquid 2, a container 5, an insulating layer 6, upper electrodes 7a and 8a, lower electrodes 7b and 8b, and a third material layer 13. have.

  The container 5 includes a container body having a cylindrical inner space and a lid that closes the opening of the container body. The material of this container 5 is comprised with the translucent resin etc. which have insulation. In the assembled state of the liquid lens 120, each component constituting the liquid lens is stored in the container 5. For convenience, FIG. 1 shows the container 5 as an integral part. The inner side surface of the container 5 is water repellent.

  The inside of the container 5 is filled with a conductive liquid 1 and a dielectric liquid 2 each having translucency. A light-transmitting third material layer 13 is formed between the conductive liquid 1 and the dielectric liquid 2. The third material layer 13 is provided in the container 5 separately from the conductive liquid 1 and the dielectric liquid 2. That is, the conductive liquid 1 and the dielectric liquid 2 are separated by the third material layer 13 in the container 5, and the respective liquids are not mixed. The third material layer 13 also serves as an antireflection film for incident light flux.

  Further, the conductive liquid 1, the dielectric liquid 2, and the third material layer 13 are disposed along the optical axis of the incident light with respect to the liquid lens 120. Specifically, in FIG. 1, the dielectric liquid 2, the third material layer 13, and the conductive liquid 1 are arranged in order from the incident side (the upper side in FIG. 1) of the liquid lens 120 in the optical axis direction. ing. Note that the upper interface in the figure of the conductive liquid 1 is formed as a convex spherical surface with the central portion protruding from the dielectric liquid 2 and the third material layer 13 by the water repellent processing of the inner side surface of the container 5.

Here, for example, an aqueous solution of an inorganic salt is used for the conductive liquid 1. The dielectric liquid 2 is, for example, fluorinated oil. The conductive liquid 1 and the dielectric liquid 2 each have a different refractive index, and the conductive liquid 1 is set to have a higher refractive index than the dielectric liquid 2.
The third material layer 13 is made of a fluid material and allows deformation of the interface shape between the conductive liquid 1 and the dielectric liquid 2. For example, the third material layer 13 includes any one of a viscous material, a liquid, a polymer film, and polymer particles. The refractive index of the third material layer 13 is set to be a value between the refractive index of the conductive liquid 1 and the refractive index of the dielectric liquid 2. The thickness of the third material layer 13 is particularly preferably set to a value of λ / (4n) where λ is the wavelength of incident light and n is the refractive index of the third material layer 13.

  In FIG. 1, the lower surface of the third material layer 13 has affinity with the conductive liquid 1. Similarly, the upper surface of the third material layer 13 has affinity with the dielectric liquid 2. Here, affinity means the property that a certain substance easily binds to another substance. However, in practice, the third material layer 13 does not have to have an affinity for both the conductive liquid 1 and the dielectric liquid 2. For example, it is sufficient that the third material layer 13 has an affinity for one of the conductive liquid 1 and the dielectric liquid 2.

In FIG. 1, an upper electrode 7a and a lower electrode 7b, and an upper electrode 8a and a lower electrode 8b each constitute a pair of electrodes. A DC voltage is applied between the pair of electrodes. Moreover, the container inner surface side of the lower electrodes 7b and 8b is covered with an insulating layer 6, respectively. FIG. 1 shows a state in which no voltage is applied to any electrode.
FIG. 2 is a diagram showing a state when a DC voltage is applied between the upper electrode 8a and the lower electrode 8b. When a DC voltage is applied to the upper electrode 8a and the lower electrode 8b, the surface tension between the conductive liquid 1 and the dielectric liquid 2 is changed by the electric field, and the conductive liquid 1 is drawn toward the electrodes 8a and 8b. Will be displaced. Thereby, the shape of the interface between the conductive liquid 1 and the dielectric liquid 2 changes, and the optical characteristics of the liquid lens 120 change.

  In the liquid lens 120 of the present embodiment, four pairs of electrodes are arranged in the circumferential direction of the lens. Thereby, the displacement of the interface in the liquid lens 120 can be controlled in two directions in a plane perpendicular to the optical axis. FIG. 3 is a view of the liquid lens 120 as viewed from the optical axis direction. On the circumference of the container 5, four arc-shaped pairs of electrodes 7, 8, 9, 10 are arranged. Then, by applying a voltage to the electrode 7 or the electrode 8, the liquid lens 120 can be controlled in the left-right direction (X direction) on the paper surface. Similarly, by applying a voltage to the electrode 9 or the electrode 10, the liquid lens 120 can be controlled in the vertical direction (Y direction) on the paper surface.

  Here, each of the electrodes (7 to 10) shown in FIG. 3 has an upper electrode and a lower electrode. The configuration of the electrodes 9 and 10 is almost the same as the configuration of the electrodes 7a, 7b, 8a and 8b shown in FIGS. Further, when it is necessary to control the refractive index of the liquid lens 120 with high accuracy, the number of divided electrodes may be further increased. In order to drive the liquid lens 120 effectively, at least three pairs of electrodes are required.

According to the above configuration, it is possible to provide the liquid lens 120 that can change the optical characteristics with a simple mechanism and can be easily reduced in size. In particular, in the present embodiment, the third material layer 13 prevents reflection at the interface of the incident light beam, so that a high-performance liquid lens 120 with improved utilization efficiency of the incident light beam can be realized.
In this embodiment, the example in which the electrodes (7 to 10) are provided in the container 5 has been described. However, a voltage may be directly applied to the conductive liquid 1.

(Specific example of this embodiment)
Next, a specific example of this embodiment will be described. Here, the refractive index of the conductive liquid 1 is nb, the refractive index of the dielectric liquid 2 is na, the refractive index of the third material layer 13 is nc, and the film thickness of the third material layer is d. In addition, the value of the refractive index in the present embodiment has a relationship of na <nc <nb. In this case, the reflectance Rc of light incident perpendicularly to the interface is expressed by the following equation.

Rc = ((na × nb−nc ² ) / (na × nb + nc ² )) ²
Since the reflection intensity of the upper surface and the lower surface of the third material layer 13 is equal, Rc = 0 in a state where there is no reflected light. Therefore, the amplitude condition is expressed by the following equation.
nc = (na × nb) ^1/2
In addition, the phase difference of the reflected light at the upper and lower boundary surfaces of the third material layer 13 needs to be λ / 2. Therefore, the phase condition is expressed by the following equation.

nc × d = λ / 4
Therefore, if the above amplitude condition and phase condition are satisfied, the reflectance Rc becomes 0 with respect to the wavelength λ. In general, reflection at the interface of the liquid lens is particularly large at a specific wavelength λ. Therefore, if the liquid lens is designed so as to satisfy the amplitude condition and the phase condition for the wavelength λ, the reflectance of light incident perpendicularly to the interface of the liquid lens can be greatly reduced.

(Comparative example)
As a comparative example to the specific example described above, an example of the reflectance R at the interface of the liquid lens not provided with the third material layer 13 is shown.
The refractive index of the conductive liquid (high refractive index) is 1.8, and the refractive index of the dielectric liquid (low refractive index) is 1.3. In this case, the reflectance R of light incident perpendicularly to the interface of the liquid lens can be expressed by the following equation.

R = ((1.8−1.3) / (1.8 + 1.3)) ²
In the above formula, the reflectance R is about 2.6% in terms of percentage, which is larger than the reflectance Rc of the specific example. Therefore, according to the present embodiment, it can be seen that the reflectance of light at the interface of the liquid lens can be greatly reduced.
(Application example 1 of liquid lens to optical equipment)
FIG. 4 is a schematic diagram showing a case where the liquid lens 120 of the present embodiment is applied to a camera system. In the example of the figure, the above-described liquid lens 120 is applied to a lens shift system blur correction device of a single-lens reflex camera system.

The camera system in FIG. 4 includes an interchangeable lens 200 and a camera body 210. The blur correction device is mounted in the interchangeable lens 200.
The interchangeable lens 200 includes an angular velocity sensor 15, an amplification unit 20, an A / D conversion unit 30, a basic value calculation unit 40, a subtractor 50, a target drive value calculation unit 60, a drive amount data table 70, The imaging magnification information calculation unit 90, the shooting distance information calculation unit 100, the blur correction lens optical information calculation unit 110, the ROM 115, the driver 80, and the liquid lens 120 for image blur correction are provided.

The basic value calculator 40, the subtractor 50, the target drive value calculator 60, the drive amount data table 70, the shooting magnification information calculator 90, the shooting distance information calculator 100, the blur correction lens optical information calculator 110, and the ROM 115 As shown in the figure, the microcomputer 150 is used. The ROM 115 stores a control method (control procedure) for the microcomputer 150.
The angular velocity sensor 15 detects vibration applied to the camera system as an angular velocity, and outputs an angular velocity detection signal corresponding to the detected angular velocity. As the angular velocity sensor 15, a piezoelectric vibration type angular velocity sensor that detects Coriolis force is usually used.

  The amplifying unit 20 amplifies the angular velocity detection signal output from the angular velocity sensor 15. Since the output of the angular velocity sensor 10 is small, the resolution of the angular velocity detection signal is too low (that is, the angular velocity detection signal per bit is too large) even if it is digitized by the A / D converter 30 and processed in the microcomputer. For this reason, accurate vibration detection cannot be performed as it is, and the accuracy of image blur correction cannot be increased. Therefore, the amplification unit 20 amplifies the angular velocity detection signal before inputting it to the A / D conversion unit 30. Thereby, the resolution of the angular velocity detection signal in the microcomputer 150 can be increased (the angular velocity detection signal per bit is reduced), and the blur correction accuracy can be increased. In addition, the amplifying unit 20 may include a low-pass filter or the like in order to reduce high-frequency noise included in the output of the angular velocity sensor 15 as well as amplify the angular velocity detection signal. The amplified angular velocity detection signal is transmitted to the A / D converter 30.

  The A / D converter 30 converts the analog angular velocity signal sent from the amplifier 20 into a digital signal. By converting the angular velocity detection signal into a digital signal, arithmetic processing in the microcomputer 150 can be performed. The A / D conversion unit 30 may be provided separately from the microcomputer 150 as shown in FIG. 4, or when the A / D conversion unit is built in the microcomputer 150, the A / D conversion unit May be used. The angular velocity detection signal is converted from an analog signal into a digital signal by the A / D conversion unit 30 and then input to the reference value calculation unit 40 and the subtracter 50.

The reference value calculation unit 40 calculates a reference value of the angular velocity detection signal when there is no shake based on the angular velocity detection signal. That is, the reference value calculation unit 40 outputs the angular velocity detection signal when the shake is zero to the subtracter 50 as a reference value.
As an example of a reference value calculation method in the reference value calculation unit 40, there is a moving average shown in the following (Equation 1).

In addition, the reference value may be calculated using a general low-pass filter. For example, a low pass filter may be provided between the amplification unit 20 and the A / D conversion unit 30.
The subtracter 50 subtracts the reference value from the angular velocity detection signal output from the A / D conversion unit 30 to obtain a shake detection signal represented by the angular velocity, and sends the obtained shake detection signal to the target drive value calculation unit 60. Output.

  The target drive value calculation unit 60 converts the shake detection signal represented by the angular velocity into shake angle information by time integration. After that, the target drive value calculation unit 60 includes shake angle information, shooting magnification information β calculated by the shooting magnification information calculation unit 90, lens focal length information R calculated by the shooting distance information calculation unit 100, and blur information. Target drive value information for driving the liquid lens 120 is calculated using the blur correction lens optical information (blur correction coefficient K) calculated by the correction lens optical information calculation unit 110.

That is, the photographing magnification information calculation unit 90 calculates the photographing magnification information β from the focal length of the photographing magnification information optical system, the position of the focus adjustment lens, and the like. The calculated photographing magnification information β is input to the target drive value calculation unit 60.
The shooting distance information calculation unit 100 calculates shooting distance information R from the focal length of the shooting distance information optical system, the position of the focus adjustment lens, and the like. The shooting distance information R is input to the target drive value calculation unit 60.

The blur correction lens optical information calculation unit 110 inputs optical information related to the blur correction lens to the target drive value calculation unit 60. The optical information here is the blur correction coefficient K as described above. The definition of the blur correction coefficient K is blur correction coefficient = image movement amount with respect to lens movement amount.
An example of an arithmetic expression for target drive value information is shown in the following (Equation 2).

  (Equation 2) calculates the deviation between the lens target drive value θ and the angular velocity detection signal output from the A / D converter 30 (operation of the subtractor 50), and drives the liquid lens 120 based on the deviation. The drive signal for calculating is calculated. The calculation of the drive signal is generally PID control in which the drive signal is calculated by adding a term proportional to the deviation, a term proportional to the integral of the deviation, and a term proportional to the derivative of the deviation. However, the method is not limited to PID control, and other methods may be used.

The drive signal output from the target drive value calculation unit 60 is input to the drive amount data table 70. The drive amount data table 70 uses the drive signal (digital signal) output from the target drive value calculation unit 60 to drive the liquid lens 120 in consideration of the optical axis shift amount of the liquid lens 120 and the shift amount in the optical axis direction. It is converted into a voltage and output to the driver 80.
The driver 80 receives the driving voltage output from the driving amount data table 70, converts the voltage to the voltage applied to the upper electrode 7a, the lower electrode 7b, the upper electrode 8a, and the lower electrode 8b, and outputs the voltage.

  The liquid lens 120 is built in the imaging optical system of the photographing unit as shown in FIG. In the liquid lens 120, the third material layer 13 located at the interface between the conductive liquid 1 and the dielectric liquid 2 prevents reflection of incident light, as in the above example. In addition, the liquid lens 120 includes four pairs of electrodes as in the above example. However, in the description of FIGS. 6 and 7 to be described later, only the control of the liquid lens with two pairs of electrodes is described for convenience, and the redundant description of the control of the liquid lens with the other two pairs of electrodes is omitted.

The camera body 210 is configured so that the interchangeable lens 200 can be attached and detached. Inside the camera body 210, a group of parts necessary for image capturing including a quick return mirror 300, an amplification type image pickup device (CCD, CMOS, etc.) 400, an optical viewfinder 500, and the like are provided.
Image blur such as a photograph occurs when an image on the imaging surface moves during exposure due to vibration applied to the camera such as camera shake. However, a camera with a shake correction apparatus as shown in FIG. 4 includes a vibration detection sensor such as the angular velocity sensor 15. These vibration detection sensors detect vibration applied to the camera system. If the vibration applied to the camera system is detected, the movement of the image on the imaging surface can be known. Therefore, the liquid lens 120 is operated so that the movement of the image on the imaging surface stops, and the imaging surface The movement of the upper image, that is, the image blur can be corrected. At this time, since the third material layer 13 of the liquid lens 120 prevents reflection of incident light, a high-performance blur correction device can be realized.

In the above embodiment, the angular velocity sensor 15 is used. However, the present invention is not limited to this, and an acceleration sensor, for example, may be used instead of the angular velocity sensor 15.
Note that the microcomputer 150 includes all the non-volatile memory that stores various information such as the arithmetic unit, the conversion unit, and the control program described above. In the above description, an example of an interchangeable lens camera system has been described. However, a camera system in which a lens and a camera are integrated may of course be used.

(Application example 2 of liquid lens to optical equipment)
FIG. 5 is a diagram showing an example in which the liquid lens 120 is applied to a lens system L of a mobile phone having a camera function. That is, by applying the liquid lens 120 to the lens system L of a mobile phone, a mobile phone having a camera function capable of performing optical blur correction can be provided. In the cellular phone shown in FIG. 5, each mechanism necessary for realizing the blur correction by the liquid lens 120 is substantially the same as the configuration shown in FIG.

(Explanation of image blur correction by liquid lens)
Hereinafter, a specific example of correcting the image blur by controlling the liquid lens 120 will be described.
FIG. 6 is a diagram showing an optical system of the shake correction apparatus in the present embodiment. In FIG. 6, the same components as those in FIG. The optical system in FIG. 6 includes optical system groups 21 and 22 that do not shift with respect to the optical axis, and a liquid lens 120 that shifts with respect to the optical axis. FIG. 6 shows a state in which the optical axes of the optical system groups are substantially coaxial. In FIG. 6, the image plane for infinity is denoted by reference numeral 31.

  7 is output from the driver 80 shown in FIG. 4 between the upper electrode 7a and the lower electrode 7b of the liquid lens 120 and between the upper electrode 8a and the lower electrode 8b of the blur correction device of FIG. This shows a state in which a voltage is applied. In this case, by changing the interface shape between the conductive liquid 1 and the dielectric liquid 2, the position of the image plane 33 is made to be almost the same position (in focus) as the image plane 31 shown in FIG. be able to.

Explanatory drawing which shows the liquid lens of this embodiment Explanatory drawing which shows the liquid lens of this embodiment Explanatory drawing which shows the liquid lens of this embodiment Block diagram showing the basic configuration of a camera equipped with a shake correction device Explanatory diagram showing an example of a mobile phone with a camera function The figure explaining the correction of the image blur by a liquid lens The figure explaining the correction of the image blur by a liquid lens

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive liquid, 2 ... Dielectric liquid, 5 ... Container, 6 ... Insulating layer, 7a, 7b ... Upper electrode, 8a, 8b ... Lower electrode, 13 ... 3rd substance layer, 15 ... Angular velocity sensor, 20 ... Amplification , 30 ... A / D converter, 40 ... basic value calculator, 50 ... subtractor, 60 ... target drive value calculator, 70 ... drive amount data table, 80 ... driver, 90 ... shooting magnification information calculator, 100 ... shooting distance information calculation unit, 110 ... blur correction lens optical information calculation unit, 115 ... ROM, 120 ... liquid lens, 200 ... interchangeable lens, 210 ... camera body, L ... lens system (cell phone)

Claims (9)

A first liquid;
A second liquid having a refractive index different from that of the first liquid;
A first layer having a refractive index between the refractive index of the first liquid and the refractive index of the second liquid and provided between the first liquid and the second liquid; A liquid lens comprising: The liquid lens according to claim 1,
The liquid lens, wherein the first layer is provided separately from the first liquid and the second liquid. The liquid lens according to claim 1 or 2, wherein
The liquid lens, wherein the first layer has fluidity. A liquid lens according to any one of claims 1 to 3, wherein
The liquid lens, wherein the first layer includes any one of a viscous material, a liquid, a polymer film, and polymer particles. A liquid lens according to any one of claims 1 to 4, wherein
The liquid lens, wherein the first liquid, the second liquid, and the first layer are disposed along an optical axis of incident light. A liquid lens according to any one of claims 1 to 5, wherein
The liquid lens according to claim 1, wherein the first layer has a role as an antireflection film for an incident light beam. A liquid lens according to any one of claims 1 to 6, wherein
When the wavelength of incident light is λ and the refractive index of the first layer is n,
The liquid lens according to claim 1, wherein the thickness of the first layer is λ / (4n). A liquid lens according to any one of claims 1 to 7,
The liquid lens, wherein the first layer has affinity with at least one of the first liquid and the second liquid. An optical apparatus using the liquid lens according to any one of claims 1 to 8.

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