JP2006078650A - Optical element, lens unit, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance optical element, a lens unit, and an imaging apparatus. <P>SOLUTION: Insulating liquid and conductive liquid having mutually different refractive index, not mutually mixable, separately having light transmissivity, and either of which is refractive index variable liquid whose refractive index is changed with the voltage application, are stored in a liquid container. Further, an optical element is provided with a 1st electrode coming into contact with the conductive liquid and a 2nd electrode insulated from the conductive liquid are prepared, and by applying the voltage between the 1st electrode and the 2nd electrode, the shape of a boundary surface between the conductive liquid and the insulating liquid is changed, and also, the refractive index of the refractive index variable liquid is changed. Then, the optical function of the optical element is drastically changed with the synergetic effects of the shape change of the boundary surface and the refractive index change. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element that transmits light, a lens unit, and an imaging device that forms image of subject light to acquire image data.

  In an electronic still camera that forms an image of a subject on a solid-state image sensor such as a charge coupled device (CCD) and captures image data representing the subject as a signal, or a film camera that takes a photograph on a photographic film Some cameras have a zoom function for freely setting a shooting angle of view, and such a camera is provided with a photographing lens whose focal length changes in accordance with the operation of a zoom switch. This photographing lens is generally a compound lens composed of a combination of a plurality of lens elements, and the relative positions of the plurality of lens elements are adjusted according to the focal length set by the zoom switch. Such a camera is equipped with a cam mechanism, and the cam mechanism transmits the rotation of the motor in response to the operation of the zoom switch, so that the plurality of lens elements move back and forth in the optical axis direction and the relative positions are adjusted. And the focal length changes.

  In addition, there is a focus lens for focus adjustment among the plurality of lens elements, and a lens driving mechanism for moving the focus lens may be provided separately from the cam mechanism.

  In recent years, in place of the above-described photographic lens having a drive mechanism, a variable focal length liquid lens in which two kinds of liquids having different refractive indexes and immiscible with each other is housed has been proposed (for example, Non-Patent Document 1).

  In the liquid lens proposed in Non-Patent Document 1, two kinds of liquids having different refractive indexes and immiscible with each other are accommodated inside, and one of these two kinds of liquids is A conductive aqueous solution and the other liquid is an insulating oil. These two kinds of liquids are accommodated in a liquid container in which both ends of a short glass tube are closed with a transparent end cap having light permeability. The inner wall of the tube and the inner wall of one end cap are covered with a water repellent film. According to the liquid lens thus configured, the conductive aqueous solution of the two types of liquid repels the inner wall of the tube covered with the water-repellent film and the inner wall of one end cap. Since the aqueous solution stays in a hemispherical shape in contact with the other end cap, the interface portion between the conductive aqueous solution and the insulating oil functions as a concave lens. The liquid lens is also provided with two electrodes for applying a voltage to the conductive aqueous solution, and one of the two electrodes is disposed in contact with the conductive aqueous solution. The other electrode is disposed on the back side of the water-repellent film. When a voltage is applied to such an electrode, an electric charge is released from the electrode disposed so as to be in contact with the aqueous conductive solution into the aqueous conductive solution, and the released charge is insulated in the aqueous conductive solution. Phenomenon that accumulates at the interface with the oil. The electric charge accumulated in the interface portion and the electric charge collected on the electrode disposed on the back side of the water-repellent film having a polarity opposite to that of the electric charge are attracted by the Coulomb force, so that the charge in the conductive aqueous solution is transferred to the water-repellent film. Attracted nearby. As a result, the conductive aqueous solution begins to wet the water-repellent film coated on the inner wall of the tube, and the interface shape of the two types of liquid changes. That is, as the voltage is applied to the conductive aqueous solution, the radius of curvature of the interface portion of the conductive aqueous solution that initially functioned as the concave lens with the insulating oil changes. It becomes flat or the conductive aqueous solution functions as a convex lens, and the focal length changes.

  According to such a liquid lens, since the focal length can be changed without moving the lens, the zoom function and the focus function can be realized without providing the cam mechanism or the lens driving mechanism described above. . Therefore, the apparatus can be significantly reduced in size, and can be applied to a small device such as a mobile phone.

Further, as an improvement technique for such a liquid lens, a technique for reducing the voltage required for changing the focus by forming an insulation provided between the water repellent film and the electrode in a thin film of 1 μm or less (see Patent Document 1). In addition, there is also known a technique (see Patent Document 2) in which a gel agent is included in the liquid in the liquid container and the distortion of the interface due to gravity or inertia force is suppressed.
As a lens having a variable focal length, a liquid crystal lens that changes the focal length by utilizing the electro-optic effect of liquid crystal is also known. For example, in Patent Document 3, the first and second light transmissive substrates having a flat plate shape and the third light transmissive substrate formed between the first and second light transmissive substrates with both surfaces formed in a concave shape are disclosed. And a space sandwiched between the first light transmissive substrate and the third light transmissive substrate and a space sandwiched between the second light transmissive substrate and the third light transmissive substrate. There has been proposed a liquid crystal lens having a liquid crystal encapsulated therein. In this liquid crystal lens, the orientation of the liquid crystal molecules changes according to the magnitude of the applied voltage, whereby the refractive index of the liquid crystal lens changes and the focal length as the lens changes.
"Philips' Fluid Lenses", [online], March 3, 2004, Royal Philips Electronics, [March 31, 2004 search], Internet <URL: http: // www. dpreview. com / news / 0403/040030302 philipsfluidens. asp> JP 2000-347005 A JP 2001-13306 A JP 2002-341111 A

  The amount of change in the focal length that occurs in the liquid lens as described above depends on the refractive index difference between the insulating oil and the conductive aqueous solution, and the larger the refractive index difference, the better the performance as a variable focal length lens. It will be. Further, the amount of change in the focal length that occurs in the liquid crystal lens as described above depends on the refractive index change accompanying the alignment of the liquid crystal molecules, and the larger the refractive index change, the better the performance as a variable focal length lens. It will be.

  Since the performance of the conventional liquid lens and liquid crystal lens is insufficient as the performance of the zoom lens and the focus lens, development of a material capable of obtaining a larger refractive index difference and refractive index change is desired.

  However, such materials need not only satisfy the requirements for refractive index but also satisfy the requirements for functioning as a liquid lens or a liquid crystal lens. There is a problem that is difficult.

  Such a problem is not a problem that occurs only in a lens but a problem that generally occurs in an optical element that applies the principle of the liquid lens or the liquid crystal lens described above.

  In view of the above circumstances, an object of the present invention is to provide a high-performance optical element, a lens unit, and an imaging apparatus.

The optical element of the present invention that achieves the above object provides:
An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
And a second electrode insulated from the conductive liquid in the liquid container.

  Here, the refractive index variable liquid does not need to change the refractive index of the entire liquid by applying a voltage, and may be, for example, only the refractive index near the electrode. The refractive index change need not be an absolute change due to a change in physical properties or the like, and may be an apparent change when viewed from a specific direction, for example.

  According to the optical element of the present invention, when a voltage is applied between the first electrode and the second electrode, electric charges are discharged from the first electrode into the conductive liquid, and the second electrode Collects charges of the opposite polarity. As a result, the charge in the conductive liquid and the charge collected on the second electrode are attracted by the Coulomb force, and the shape of the boundary surface between the conductive liquid and the insulating liquid changes. Further, the refractive index of the refractive index variable liquid also changes, and the optical function of the optical element (for example, the focal length of the lens and the refractive angle of the prism) changes greatly due to the synergistic effect of the change in the shape of the boundary surface and the change in the refractive index. . Therefore, the optical element of the present invention has high performance and a long life because a sufficient change can be obtained at a low voltage.

  The optical element of the present invention includes a dispersion medium having a refractive index different from the refractive index of the light-transmitting dispersion medium, the light-transmitting dispersion medium dispersed in the dispersion medium. It is preferable that it consists of.

  According to such a suitable optical element, when a voltage is applied between the first electrode and the second electrode, the refractive index different from the refractive index of the dispersion medium is formed along with the change in the shape of the boundary surface described above. Electrophoresis of a dispersoid having a refractive index occurs, and the refractive index changes according to the amount of movement of the dispersoid.

  The degree of freedom in selecting the dispersoid is high, and a high-performance optical element can be realized without difficult material development.

  Here, the dispersoid is preferably composed of nanoparticles.

  Even if the dispersoid is a nanoparticle, it can be electrophoresed.

  It is also a preferred aspect that the dispersoid is made of titanium oxide nanoparticles.

  When the dispersoid is made of titanium oxide nanoparticles, an optical element having a higher refractive index can be realized. In addition, since titanium oxide nanoparticles are general-purpose, they are easily available for production.

  Further, the dispersoid is preferably made of alumina nanoparticles.

  If the dispersoid is made of alumina nanoparticles, the cost of the dispersoid can be reduced.

  Furthermore, the dispersion medium is preferably water.

  When the dispersion medium is water, the dispersibility of the dispersoid is excellent and the cost of the dispersion medium is low.

  It is also a preferred embodiment that the dispersion medium is an organic dispersion medium.

  When the dispersion medium is an organic dispersion medium, it is electrically stable.

  Furthermore, the dispersion medium is preferably a hydrocarbon-based organic dispersion medium.

  When the dispersion medium is a hydrocarbon-based organic dispersion medium, it is more electrically stable than an organic solvent having a functional group.

  In the optical element of the present invention, it is also preferable that the refractive index variable liquid is a liquid containing liquid crystal.

  According to such a suitable optical element, when a voltage is applied between the first electrode and the second electrode, the alignment of the liquid crystal molecules occurs along with the change in shape of the boundary surface described above, and the amount of alignment The refractive index changes according to Such alignment of the liquid crystal molecules is faster than the movement of the dispersoid by electrophoresis, so that the response speed of the optical element is fast.

  In the optical element of the present invention, it is more preferable that the refractive index variable liquid is a liquid containing a nematic liquid crystal.

  Since the nematic liquid crystal has a negative dielectric anisotropy, the hydrophilicity / hydrophobicity of the nematic liquid crystal changes greatly upon voltage application. As a result, the orientation in the liquid container is greatly changed, resulting in a large refractive index change.

The lens unit of the present invention that achieves the above object provides:
An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
A second electrode insulated against the conductive liquid in the liquid container,
The shape of the boundary surface between the insulating liquid and the conductive liquid changes according to the voltage applied between the first electrode and the second electrode.

  According to the lens unit of the present invention, as in the case of the optical element of the present invention, a large change in optical function occurs, so that the performance is high.

  Note that the lens unit according to the present invention is only shown in its basic form here, but this is only for avoiding duplication, and the lens unit according to the present invention is not limited to the above basic form. Various forms corresponding to the respective forms of the optical element described above are included.

In addition, the imaging device of the present invention that achieves the above-described object provides:
An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
A second electrode insulated from the conductive liquid in the liquid container;
A controller that changes the shape of the boundary surface between the insulating liquid and the conductive liquid by applying a voltage between the first electrode and the second electrode;
An imaging device that includes an insulating liquid and subject light that has passed through the conductive liquid is imaged on the surface to generate an image signal representing the subject light.

  According to the imaging device of the present invention, as in the optical element of the present invention, a large change in the optical function occurs. Therefore, high performance such as a wide focus range and a large zoom change using the change in the optical function is obtained. Realized.

  Note that only the basic form of the imaging apparatus according to the present invention is shown here, but this is only for avoiding duplication, and the imaging apparatus according to the present invention is not limited to the above basic form. Various forms corresponding to the respective forms of the optical element described above are included.

  ADVANTAGE OF THE INVENTION According to this invention, a high performance optical element, a lens unit, and an imaging device can be provided.

  Hereinafter, prior to describing embodiments of the present invention, the problems of the liquid lens described in Non-Patent Document 1 described above will be analyzed in detail.

  FIG. 1 is a schematic configuration diagram of a liquid lens as a comparative example. Hereinafter, light is transmitted in the direction of the arrow O, and the light incident side (upper side in FIG. 1) is referred to as the upper side, and the light emission side (lower side in FIG. 1) is referred to as the lower side.

  As shown in FIG. 1, the liquid lens 1 is made of transparent water in which a supporting electrolyte is added into a glass container 11 in which both ends of a glass tube 11a are closed with glass caps 11b and 11c. 21 and transparent oil 22 that is an insulating liquid are contained without being mixed with each other. Since the oil 22 has a higher light refractive index than the water 21, the oil 22 plays the role of a lens that refracts light in the liquid lens 1.

  The inner surface of the tube 11a of the container 11 and the inner surface of the cap 11b that closes the upper end of the tube 11a are covered with a water-repellent water-repellent film 15, and the inner surface of the cap 11c that closes the lower end of the tube 11a is hydrophilic. It is covered with a hydrophilic film 16 having

  Further, an insulating film 14 is provided between the tube 11 a and the water repellent film 15, and the liquid lens 1 is insulated from the water 21 by the first electrode 12 in contact with the water 21 and the insulating film 14. A second electrode 13 is also provided.

When no voltage is applied between the first electrode 12 and the second electrode 13, the water 21 repels the water-repellent film 15 and repels the hydrophilic film 16 as shown in part (A) of FIG. Therefore, the contact portion P ₁ between the water 21 and the water repellent film 15 becomes small. For this reason, the water 21 stays in a hemispherical shape, and the oil 22 pushed by the water 21 stays in a shape that penetrates the hemisphere from the cylindrical shape. Since the shape of the boundary surface between the water 21 and the oil 22 when viewed from the oil 22 is concave, in the part (A), the liquid lens 1 functions as a concave lens.

For example, when a positive voltage is applied to the first electrode 12 and a negative voltage is applied to the second electrode 13, a positive charge 31 a is released from the first electrode 12 to the water 21, and a negative voltage is applied to the second electrode 13. Charge 31b accumulates. At this time, the positive charge 31a released to the water 21 is attracted to the negative charge 31b of the second electrode 13 by the Coulomb force, and the contact portion P ₂ between the water 21 and the water repellent film 15 increases according to the applied voltage. . In part (B), the shape of the boundary surface between the water 21 and the oil 22 when viewed from the oil 22 is convex, and the liquid lens 1 functions as a convex lens. Moreover, the shape of the boundary surface between the water 21 and the oil 22 can be changed little by little by adjusting the voltage applied to the first electrode 12 and the second electrode 13.

  Thus, according to the liquid lens 1, the zoom function and the focus function can be realized by changing the shape of the boundary surface between the water 21 and the oil 22 without providing a mechanism for moving the lens.

  However, in the liquid lens 1, the difference in refractive index between the water 21 and the oil 22 is small, and a large change in the shape of the boundary surface is necessary to realize the zoom function and the focus function. For this reason, a high voltage is applied between the first electrode 12 and the second electrode 13, and the life of the liquid lens 1 is shortened.

  The present invention is based on the detailed analysis as described above.

  A first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 2 is an external perspective view of the digital camera corresponding to the first embodiment of the present invention as seen from diagonally above the front.

  As shown in FIG. 2, a photographing lens 101 is provided at the center of the front surface of the digital camera 100. Further, an optical viewfinder objective window 102 and an auxiliary light emitting unit 103 are provided on the upper front of the digital camera 100. Further, a slide-type power switch 104 and a release switch 150 are provided on the upper surface of the digital camera 100.

  FIG. 3 is a schematic configuration diagram of the digital camera 100 shown in FIG.

  As shown in FIG. 3, the breakdown of the digital camera 100 is roughly divided into a photographing optical system 110 and a signal processing unit 120. In addition to these, the digital camera 100 includes an image display unit 130 for displaying captured images, an external recording medium 140 for recording captured image signals, and various processes for capturing digital cameras. A zoom switch 170, a shooting mode switch 160, and a release switch 150 are provided.

  First, the configuration of the photographing optical system 110 will be described with reference to FIG.

  In the digital camera 100, subject light enters from the left in FIG. 3, passes through the zoom unit 115 and the focus unit 114, passes through the iris 113 that adjusts the amount of the subject light, and then is solid when the shutter 112 is open. An image is formed on the image sensor 111. The solid-state image sensor 111 corresponds to an example of an image sensor according to the present invention. Originally, a plurality of lenses are provided in the photographing optical system, and at least one of the plurality of lenses is largely involved in the focus adjustment, and the relative position of each lens is involved in the focal length. A lens related to a change in focal length is schematically shown as a zoom unit 115, and a lens related to focus adjustment is also shown schematically as a focus unit 114.

  The zoom unit 115, the iris 113, and the shutter 112 are driven and moved by the zoom motor 115a, the iris motor 113a, and the shutter motor 112a, respectively. The focus unit 114 is provided with a focus controller 114a that changes the lens shape of the focus unit 114 instead of the motor. Instructions for operating the zoom motor 115a, the iris motor 113a, and the shutter motor 112a are transmitted from the digital signal processing unit 120b in the signal processing unit 120 through the motor driver 120c, and instructions for operating the focus controller 114a are digital. Directly transmitted from the signal processing unit 120b.

  The zoom unit 115 is moved in a direction along the optical axis by a zoom motor 115a. When the zoom unit 115 is moved to a position corresponding to the signal from the signal processing unit 120, the focal length is changed and the photographing magnification is determined.

  The focus unit 114 is a lens for realizing a TTLAF function. In general, the TTLAF function is such that the AF / AE calculation unit 126 of the signal processing unit 120 detects the contrast of the image signal obtained by the solid-state imaging device 111 while moving the focus unit in the direction along the optical axis. The focus position 114 is adjusted to the focus position with the lens position where the contrast peak is obtained as the focus position. With this TTLAF function, it is possible to automatically focus on a subject whose contrast is at a peak (that is, the closest subject closest to the subject). In this embodiment, instead of moving the focus unit 114, the focus controller 114a changes the lens shape and refractive index of the focus unit 114 to focus on the subject. The configuration of the focusing unit 114 and the method of changing the lens shape and the refractive index will be described in detail later.

  The iris 113 is driven based on an instruction given from the AF / AE calculation unit 126 of the digital signal processing unit 120b to adjust the amount of subject light.

  The above is the configuration of the photographing optical system 110.

  Next, the configuration of the signal processing unit 120 will be described. A subject image formed on the solid-state imaging device 111 by the photographing optical system is read as an image signal to the analog processing (A / D) unit 120a, and the analog processing unit (A / D) 120a converts the analog signal into a digital signal. It is converted and supplied to the digital signal processor 120b. A system controller 121 is provided in the digital signal processing unit 120b, and signal processing in the digital signal processing unit 120b is performed in accordance with a program showing an operation procedure in the system controller 121. Data between the system controller 121 and the image signal processing unit 122, image display control unit 123, image compression unit 124, media controller 125, AF / AE calculation unit 126, key controller 127, buffer memory 128, and internal memory 129 Is transferred via the bus 1200, and the internal memory 129 serves as a buffer when data is transferred via the bus 1200. Data serving as variables is written to the internal memory 129 as needed according to the progress of the processing process of each unit, and the system controller 121, the image signal processing unit 122, the image display control unit 123, the image compression unit 124, and the media controller 125 are written. The AF / AE calculation unit 126 and the key controller 127 perform appropriate processing by referring to the data. That is, an instruction from the system controller 121 is transmitted to each of the above units via the bus 1200, and a processing process of each unit is started. Then, the data in the internal memory 129 is rewritten in accordance with the progress of the process, and is further referred to on the system controller 121 side to manage the operation of each unit described above. In other words, the power is turned on, and the process of each unit is started according to the procedure of the program in the system controller 121. For example, when the release switch 150, zoom switch, and shooting mode switch are operated, information indicating that the switch has been operated is transmitted to the system controller 121 via the key controller 127, and processing corresponding to the operation is performed by the system controller. This is performed according to the program procedure in 121.

  When the release operation is performed, the image data read from the solid-state imaging device is converted from an analog signal to a digital signal by an analog processing (A / D) unit 120a, and the digitized image data is converted into a digital signal processing unit. Once stored in the buffer memory 128 in 120b. The RGB signal of the digitized image data is converted into a YC signal by the image signal processing unit 122, and further compression called JPEG compression is performed by the image compression unit 124 so that the image signal becomes an image file and the media controller 125 is set. To the external recording medium 140. The image data recorded as the image file is reproduced on the image display unit 130 through the image display control unit 123. In this processing, the AF / AE calculation unit performs the focus adjustment and the exposure adjustment based on the RGB signals. The AF / AE calculation unit 126 detects the contrast for each subject distance from the RGB signals for focus adjustment. Based on the detection result, the focus unit 114 performs focus adjustment. The AF / AE calculation unit extracts a luminance signal from the RGB signal, and detects the field luminance therefrom. Based on this result, exposure adjustment is performed by the iris 113 so that the amount of subject light given to the solid-state imaging device is appropriate.

  The digital camera 100 is basically configured as described above.

  Here, the feature of the present invention in the digital camera 100 resides in the focus unit 114. Hereinafter, the focus unit 114 will be described in detail.

  FIG. 4 is a schematic configuration diagram of the focus unit. The object light enters from the left side of FIG. 4 in the direction of arrow O, and the light incident side (left side of FIG. 4) is referred to as the front side, and the light emission side (right side of FIG. 4) is referred to as the rear side. I do.

  In the focus unit 114, the conductive liquid 302 and the insulating liquid 301 immiscible with the conductive liquid 302 are stored in the liquid container 201 in which both ends of the tube 201a are closed with caps 201b and 201c. Is formed. The liquid container 201 is made of transparent glass and corresponds to an example of the liquid container referred to in the present invention.

  The surface (inner surface) in contact with the liquid of the cap 201c that closes the rear end of the tube 201a is covered with a hydrophilic film 206 having hydrophilicity. The inner surface of the liquid container 201 other than the portion covered with the hydrophilic film 206 is covered with a water-repellent film 205 having water repellency. The water repellent film 205 corresponds to an example of a coating film according to the present invention.

  Further, in the liquid container 201, the first electrode 202 disposed so as to sandwich the hydrophilic film 206, the insulating film 204 sandwiched between the tube 201 a and the water-repellent film 205, and the insulating film 204 are disposed. The second electrode 203 insulated from the liquid is also provided. The first electrode 202 and the second electrode 203 are connected to the focus controller 114a shown in FIG. 3, and a voltage is applied between these electrodes by the focus controller 114a. The first electrode 202 corresponds to an example of the first electrode according to the present invention, and the second electrode 203 corresponds to an example of the second electrode according to the present invention. The focus controller 114a corresponds to an example of a control unit referred to in the present invention.

  In the liquid container 201 as described above, the conductive liquid 302 and the insulating liquid 301 having different optical refractive indexes are stored. In this embodiment, a conductive liquid 302 in which a supporting electrolyte (tetrabutylammonium perchlorate 0.1 mol / L) is added to water is used, and an organic solvent (Isopar: Exxon) is used as the insulating liquid 301. And a refractive index of 1.43) is applied. The conductive liquid 302 corresponds to an example of the conductive liquid according to the present invention, and the insulating liquid 301 corresponds to an example of the insulating liquid according to the present invention.

  Further, in the insulating liquid 301, about 20% by volume of titanium oxide nanoparticles 303 (refractive index 2.30) are mixed and dispersed. That is, in this embodiment, the insulating liquid 301 corresponds to an example of the dispersion medium referred to in the present invention, and the nanoparticles 303 correspond to an example of the dispersoid referred to in the present invention, and the nanoparticles 303 are dispersed. The insulating liquid 301 in the state corresponds to an example of the refractive index variable liquid referred to in the present invention.

  These titanium oxide nanoparticles 303 were obtained by making hydrous titanium oxide amorphous with alkali, then aging it in hydrochloric acid, and heating it to a particle size of 10 nm. Stearoyl titanate) is obtained by treatment with a solution and is positively charged.

  In a state where no voltage is applied between the first electrode 202 and the second electrode 203, the conductive liquid 302 repels the water-repellent film 205, whereby the boundary surface between the conductive liquid 302 and the insulating liquid 301. Has a shape as shown in FIG. At this time, the first electrode 202 and the conductive liquid 302 are in contact with each other. Further, the nanoparticles 303 are uniformly dispersed in the insulating liquid 301.

In the state shown in FIG. 4, since the refractive index n1 of the insulating liquid 301 is 1.604 and the refractive index n2 of the conductive liquid 302 is 1.33, the focus portion 114 acts as a concave lens. The focal length at this time is such that the curvature R of the boundary surface is 5.0 mm, the thickness d1 of the insulating liquid 301 is 1.0 mm, and the thickness d2 of the conductive liquid 302 is 3.5 mm.
Focal length -18.25mm
Back focus -20.88mm
Front focus 18.87mm
It becomes.

  Here, when the focus controller 114 a applies a voltage between the first electrode 202 and the second electrode 203 in accordance with an instruction from the signal processing unit 120 shown in FIG. 3, the electric charge is charged from the first electrode 202 to the conductive liquid 302. The second electrode 203 collects charges having a polarity opposite to that of the charges discharged to the conductive liquid 302. The charge released to the conductive liquid 302 and the charge of the second electrode 203 are attracted by Coulomb force, and the charge in the conductive liquid 302 is attracted to the vicinity of the water repellent film 205. As a result, the boundary surface between the conductive liquid 302 and the insulating liquid 301 changes.

  FIG. 5 is a diagram illustrating a state in which a voltage is applied to the focus unit.

  When a voltage is applied between the first electrode 202 and the second electrode 203, the boundary surface between the conductive liquid 302 and the insulating liquid 301 changes to a shape as shown in FIG. Here, the first electrode 202 is an anode and the second electrode 203 is a cathode.

  Since the nanoparticles 303 dispersed in the insulating liquid 301 are positively charged, the nanoparticles 303 gather around the second electrode 203 by electrophoresis. Since the surfaces of the nanoparticles 303 are treated with a solution of a titanium coupling agent, aggregation of the nanoparticles 303 is prevented. Further, since the surface of the second electrode 203 is covered with the water-repellent film 205, the nanoparticles 303 are also prevented from adsorbing to the surface of the second electrode 203.

In the state shown in FIG. 5, since the refractive index n1 of the insulating liquid 301 is 1.43 and the refractive index n2 of the conductive liquid 302 is 1.33, the focus portion 114 also functions as a concave lens. The focal length at this time is such that the curvature R of the boundary surface is 8.5 mm, the thickness d1 of the insulating liquid 301 is 1.5 mm, and the thickness d2 of the conductive liquid 302 is 3.0 mm.
Focal length -85.0mm
Back focus -87.26mm
Front focus 86.05mm
It becomes.

  As described above, the focal length of the focus unit 114 changes significantly at a low voltage due to the synergistic effect of the change in the shape of the boundary surface and the change in the refractive index. In addition, such a focus unit 114 has a long life by avoiding deterioration due to application of a high voltage.

  The state shown in FIGS. 4 and 5 is a state realized by a static voltage, but since the speed of the shape change of the interface and the speed of electrophoresis of the nanoparticles are significantly different, in addition to the static voltage, Intermediate states are also realized by using instantaneous voltage changes.

  FIG. 6 is a diagram illustrating a state realized by instantaneously applying a voltage from the state illustrated in FIG. 4.

  In the state shown in FIG. 4, when the focus controller 114a momentarily applies a voltage between the first electrode 202 and the second electrode 203, the shape of the boundary surface is maintained while the uniform dispersion state of the nanoparticles 303 is maintained. A change occurs, and the state shown in FIG. 6 is realized.

In the state shown in FIG. 6, the refractive index n1 of the insulating liquid 301 is 1.604 and the refractive index n2 of the conductive liquid 302 is 1.33 as in the state shown in FIG. Similarly to the shape shown in FIG. 5, the boundary surface has a curvature R of 8.5 mm, the thickness d1 of the insulating liquid 301 is 1.5 mm, and the thickness d2 of the conductive liquid 302 is 3.0 mm. Then, the focal length of the focus unit 114 is
Focal length -31.02mm
Back focus -33.28mm
Front focus 31.96mm
It becomes.

  Thus, an intermediate focal length is instantaneously realized by applying a voltage instantaneously from the state shown in FIG. Further, by adjusting the instantaneous applied voltage, an arbitrary focal length between -18.25 mm and -31.02 mm can be obtained. The digital camera 100 shown in FIG. 2 can sufficiently shoot even in such a state that is instantaneously realized.

  The intermediate focal length can also be realized by instantaneously lowering the applied voltage from the state shown in FIG.

  FIG. 7 is a diagram showing a state realized by instantaneously lowering the applied voltage from the state shown in FIG.

  In the state shown in FIG. 5, when the focus controller 114 a instantaneously reduces the voltage between the first electrode 202 and the second electrode 203, the state where the nanoparticles 303 are gathered around the second electrode 203 is maintained. As a result, the shape of the boundary surface changes, and the state shown in FIG. 7 is realized.

In the state shown in FIG. 7, the refractive index n1 of the insulating liquid 301 is 1.43 and the refractive index n2 of the conductive liquid 302 is 1.33 as in the state shown in FIG. Further, when the voltage instantaneously drops to 0 V, the boundary surface has a curvature R of 5.0 mm and the insulating liquid 301 has a thickness d1 of 1.0 mm, as in the shape shown in FIG. Since the thickness d2 of the conductive liquid 302 is 3.5 mm, the focal length of the focus unit 114 is
Focal length -50.0mm
Back focus -52.63mm
Front focus 50.70mm
It becomes.

  Thus, an intermediate focal length is instantaneously realized by instantaneously reducing the voltage from the state shown in FIG. Furthermore, by adjusting the magnitude of the instantaneous drop voltage, an arbitrary focal length between -85.0 mm and -50.0 mm can be obtained. In the example shown above, since there is a focal length gap between the focal length in the state shown in FIG. 6 and the focal length in the state shown in FIG. 7, the applied voltage in the state shown in FIG. It is desirable that the distance be set slightly higher so that the distance gap is eliminated.

  By using such a focus unit 114, the TTLAF function is realized by the following procedure.

  First, a static voltage and an instantaneous voltage are applied between the first electrode 202 and the second electrode 203 by the focus controller 114a, and the instantaneous focal distance of the focus unit 114 is gradually changed. An imaging signal at each moment is acquired by the solid-state imaging device 111 shown in FIG. Subsequently, the contrast of the imaging signal is detected by the AF / AE calculation unit 126, and the static voltage and the instantaneous voltage that realize the focal length when the contrast peak is obtained are the first electrode 202 and the second electrode 203. Between each other. Thus, the subject can be focused by performing shooting in a state where the appropriate focal length is determined.

  Above, description of 1st Embodiment of this invention is complete | finished, and 2nd Embodiment is demonstrated continuously. Since the first embodiment and the second embodiment have substantially the same device configuration, the difference from the first embodiment is noted, and the same elements are denoted by the same reference numerals and the description thereof is omitted.

  FIG. 8 is a schematic configuration diagram of a focus unit in the second embodiment of the present invention. In this case as well, the object light is incident in the direction of the arrow O from the left side of the figure, and the side on which the light is incident (left side of the figure) is referred to as the front side, and the side from which light is emitted (right side of the figure) is referred to as the rear side. Do.

  In the second embodiment, the focus unit 116 shown here is incorporated in the digital camera 100 in place of the focus unit 114 shown in FIG.

  In the focus unit 116 of the second embodiment, liquid crystal 304 is used in place of the insulating liquid in which nanoparticles are dispersed in the focus unit of the first embodiment. As the liquid crystal 304, liquid crystal MLC-6608 (manufactured by Merck) having negative dielectric anisotropy is used. Further, a vertical alignment film (here, a polyimide film) 207 that causes vertical alignment of liquid crystal molecules is provided on the inner surface portion of the front cap 201b, and the molecules of the liquid crystal 304 are aligned along the light incident direction. ing.

    Here, when the focus controller 114a applies a voltage between the first electrode 202 and the second electrode 203 in accordance with an instruction from the signal processing unit 120 shown in FIG. As the shape of the interface changes, the orientation of the molecules in the liquid crystal 304 also changes.

  FIG. 9 is a diagram illustrating a state in which a voltage is applied to the focus unit illustrated in FIG.

  As shown in FIG. 9, when a voltage is applied between the first electrode 202 and the second electrode 203, the boundary surface shape changes, and the liquid crystal 304 in the vicinity of the second electrode 203 changes. The molecules are oriented in the direction toward the second electrode 203. As a result, in the vicinity of the second electrode 203, the refractive index changes from the refractive index “1.70” when no voltage is applied to the refractive index “1.50” when a voltage is applied. Due to the synergistic effect of the change in refractive index and the change in the shape of the boundary surface, the focal length of the focus portion 116 changes greatly at a low voltage. In the focus unit 116, both the change in refractive index and the change in the shape of the boundary surface change according to the static applied voltage. Therefore, when the TTLAF function is realized, the applied voltage is The contrast at each applied voltage is detected while being changed little by little.

  This is the end of the description of the embodiment of the present invention.

  In the above description, an example in which two types of liquids, that is, a conductive liquid and an insulating liquid are stored in the liquid container has been described. However, three or more kinds of liquids are stored in the liquid container according to the present invention. May be.

  In the above description, the example in which the optical element of the present invention is applied to the focus unit has been described. However, the optical element of the present invention may be applied to a zoom unit or the like.

  Further, in the above, a focus unit capable of realizing an intermediate focal length is shown as an example of the optical element of the present invention. However, in the optical element of the present invention, it is not essential to realize an intermediate focal length. For example, when used for switching the photographing magnification, only the state with the longest focal length and the state with the shortest focal length may be used.

Subsequently, various forms that can be adopted in each component constituting the present invention will be additionally described.
<Liquid>
The conductive liquid and the insulating liquid referred to in the present invention may be two or more kinds of liquids having different refractive indexes and not mixed with each other.

  Any combination of these liquids may be used, but a combination of water and an organic solvent is preferable. As the organic solvent, preferably, hydrocarbons (hexane, heptane, pentane, octane, isopar (exxon), etc.), hydrocarbon aromatic compounds (benzene, toluene, xylene, mesitylene, etc.), halogenated hydrocarbons ( Difluoropropane, dichloroethane, chloroethane, bromoethane, etc.), halogenated hydrocarbon aromatic compounds (chlorobenzene, etc.), and ether compounds (diphenyl ether, anisole, diphenyl ether, etc.) are preferred.

  Moreover, it is preferable to add a supporting electrolyte to water for the purpose of increasing electrical conductivity. As the supporting electrolyte, TMAP: Tetramethylammonium perchlorate, TBAF: Tetrabutylammonium hexafluorophosphate, or the like is used.

In the present invention, it is necessary that at least one of the conductive liquid and the insulating liquid has a refractive index that changes in the traveling direction of light by voltage application, and the refractive index changes in this way. Any of these may be used, but a liquid in which transparent charged particles are dispersed or a liquid containing at least one liquid crystal compound is preferable. Moreover, nanoparticles are preferable as the transparent charged particles.
<Nanoparticles>
Any material may be used for the nanoparticles described above. Examples thereof include silica, alumina, zirconia, titanium oxide, tungsten oxide, zinc oxide, tin oxide, and barium titanate. Titanium oxide, silica gel (SiO ₂ ), alumina, and polymer particles are preferable. The method for adjusting the nanoparticles may be any of a solid phase method, a liquid phase method and a gas phase method, preferably a liquid phase method and a gas phase method. Details thereof are described in the document “Preparation of nanoparticles and dispersion / aggregation control and evaluation thereof, Technical Information Association, 2003”. The particle size is preferably 100 nm or less. If the particle size exceeds 100 nm, light scattering occurs and transparency (light transmission) is impaired.

  The surface of the nanoparticles is preferably modified for the purpose of improving the dispersion stability in the dispersion medium. Surface modification methods include titanium coupling agents (such as isopropyl triisostearoyl titanate), silane coupling agents (such as pentadecafluorodecyltrimethylsilane), aluminum coupling agents (such as acetoalkoxyaluminum diisopropylate), and grafts. Polymerization etc. are mentioned. For graft polymerization, polyethylene graft polymerization and polystyrene graft polymerization can be used for titanium oxide, and graft polymerization using silanol groups can be used for silica gel. Known anions, cations, and nonionic surfactants are used for the polymer particles. Particularly preferred are anionic surfactants such as sodium laurate, sodium stearate, sodium oleate, sodium dodecyl sulfate, sodium lauryl sulfate, sodium stearyl sulfate, sodium stearyl phosphate and the like.

Furthermore, it is preferable to use a charging agent for imparting an appropriate charge to the nanoparticles. As the charging agent used, various amphiphilic (high) molecules, nigrosine compounds, alkoxylated amines, quaternary ammonium salts, alkylamides, phosphorus and tungsten simple substances and compounds, molybdenum chelate pigments, hydrophobic silica, Boron, halogen compound, metal complex salt of monoazo dye, salicylic acid, alkyl salicylic acid, dialkyl salicylic acid, metal complex salt of naphthoic acid, chlorinated polyolefin, chlorinated polyester, excess acid group polyester, sulfonylamine of copper phthalocyanine, oil black, naphthene Examples include acid metal salts, fatty acid metal salts, and resin acid soaps. The addition amount of the charging agent contained in the nanoparticles is preferably in the range of 2% by mass to 70% by mass.
<Dispersion medium>
As the dispersion medium for dispersing the nanoparticles, water or a non-aqueous organic dispersion medium can be used. Further, water and an organic dispersion medium may be mixed and used. As the non-aqueous organic dispersion medium, preferably, hydrocarbon (hexane, heptane, pentane, octane, isopar (Exxon), etc.), hydrocarbon aromatic compound (benzene, toluene, xylene, mesitylene, ethylbenzene, etc.), halogen Hydrocarbons (difluoropropane, dichloroethane, chloroethane, bromoethane, etc.), halogenated hydrocarbon aromatic compounds (chlorobenzene, etc.), ether compounds (dibutyl ether, anisole, diphenyl ether, etc.), alcohol compounds (glycerin, etc.), carbonyl Compounds having a group (such as propylene carbonate), nitro compounds (such as nitromethane), nitrile compounds (such as acetonitrile and benzonitrile), and water are preferable.

  About a dispersion medium, it is preferable to adjust a refractive index, specific gravity, a viscosity, a resistivity, a dielectric constant etc. in relation to the use of an optical element. This adjustment can be performed by mixing a plurality of dispersion media.

In addition, an acid, an alkali, a salt, a dispersion stabilizer, a stabilizer for the purpose of preventing oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like can be added to the dispersion medium.
<LCD>
The liquid containing the liquid crystalline compound described above may be a liquid composed only of the liquid crystalline compound, or may be a mixed liquid of water or an organic solvent and the liquid crystalline compound.

  The liquid crystal whose refractive index changes in response to the application of an electric field is preferably a nematic liquid crystal, a smectic liquid crystal, or a discotic liquid crystal, particularly preferably a nematic liquid crystal, and more preferably a fluorine-based liquid crystal.

  The liquid crystal usually has a larger value of n‖ when compared with the refractive index (n‖) in the molecular long axis direction and the refractive index (n⊥) in the molecular short axis direction. The molecular long axes are aligned in the direction.

When liquid crystal is used in the present invention, a combination using water as the conductive liquid and a liquid crystal compound as the insulating liquid is preferable. Therefore, when no electric field is applied, the liquid crystal molecules are preferably aligned parallel to the incident direction of light. This is because, when an electric field is applied, the liquid crystal molecules in the vicinity of the electrodes are aligned in the direction intersecting the light incident direction, whereby the difference in refractive index between the two liquids can be further reduced. In order to align the liquid crystal molecules parallel to the incident direction of light, it is desirable to provide a vertical alignment film (such as a polyimide film) on the inner wall of the liquid container where the light is incident.
<Liquid container>
The liquid container materials described above include glass substrate, polyester, polyimide, polymethyl methacrylate, polystyrene, polypropylene, polyethylene, polyamide, nylon, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyether sulfone, silicone resin, polyacetal. A polymer film such as a resin, a fluororesin, a cellulose derivative, and a polyolefin, a plate substrate, a metal substrate, an inorganic substrate such as a ceramic substrate, and the like are preferably used. A container having a light transmittance of at least 50% is preferred, and more preferably a light transmittance of 80% or more.
<Electrode>
Examples of cathode and anode electrode members include gold, silver, copper, aluminum, magnesium, nickel, platinum, carbon, conductive polymers, tin oxide indium oxide (ITO), tin oxide, and zinc oxide. What formed the oxide layer is used suitably. Moreover, when installing an electrode in the part which permeate | transmits light, it is preferable to use what is called a transparent electrode. Metal oxides typified by tin oxide indium monoxide (ITO), tin oxide, zinc oxide and the like are preferred.

  Here, the basic embodiment for realizing the concept of the present invention has been described above. However, when the optical element employed in the present invention is put into practical use, dust, water droplets, or the like adhere to the optical path. It is preferable to devise measures to prevent a problem that the lens performance deteriorates.

  For example, it is preferable to provide a water-repellent film on the outer surface (hereinafter, this surface is referred to as a light transmission surface) that intersects with the optical path of the container containing the liquid. By imparting water repellency to the light transmitting surface, dust and water droplets can be prevented from adhering and the high light transmittance of the optical element can be maintained. The material constituting the water-repellent film is preferably a silicone resin, an organopolysiloxane block copolymer, a fluorine-based polymer, or polytetrafluoroethane.

  It is also preferable to attach a hydrophilic film to the light transmission surface of the container constituting the optical element. By imparting hydrophilic oil repellency to the light transmitting surface, it is possible to prevent dust from adhering. As this hydrophilic film, a film composed of an acrylate polymer, or a film coated with a surfactant such as a nonionic organosilicone surfactant is preferable. Monomer plasma polymerization, ion beam treatment, and the like can be applied.

  It is also preferable to attach a photocatalyst such as titanium oxide to the light transmission surface of the container constituting the optical element. Dirt is decomposed by the photocatalyst that reacts with light, and the light transmission surface can be kept clean.

  It is also preferable to provide an antistatic film on the light transmission surface of the container constituting the optical element. If static electricity accumulates on the light transmission surface of the container or is charged by an electrode, dust or dust may stick to the light transmission surface. By attaching an antistatic film to the light transmission surface, such unnecessary objects can be prevented from being attached and the light transmission of the optical element can be maintained. The antistatic film is preferably composed of a polymer alloy material, and the polymer alloy system may be a polyether type, a polyether ester amide type, those having a cationic group, Name, Daiichi Kogyo Seiyaku Co., Ltd.). The antistatic film is preferably produced by a mist method.

  Further, an antifouling material may be applied to the container constituting the optical element. As the antifouling material, a fluororesin is preferable, but specifically, a fluorine-containing alkylalkoxysilane compound, a fluorine-containing alkyl group-containing polymer, an oligomer, or the like is preferable, and has a functional group capable of crosslinking with the curable resin. Is particularly preferred. Moreover, it is preferable that the addition amount of antifouling | stain-proof material is a required minimum amount which expresses antifouling property.

It is a schematic block diagram of the liquid lens which is a comparative example. It is the external appearance perspective view which looked at the digital camera equivalent to 1st Embodiment of this invention from the front diagonally upward. It is a schematic block diagram of the digital camera 100 shown in FIG. It is a schematic block diagram of a focus part. It is a figure which shows the state in which the voltage was applied to the focus part. It is a figure which shows the state implement | achieved by applying a voltage instantaneously from the state shown in FIG. FIG. 6 is a diagram showing a state realized by instantaneously lowering the applied voltage from the state shown in FIG. 5. It is a schematic block diagram of the focus part in 2nd Embodiment of this invention. It is a figure which shows the state in which the voltage was applied to the focus part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid lens 11 Container 11a Tube 11b, 11c Cap 12 1st electrode 13 2nd electrode 14 Insulating film 15 Water repellent film 16 Hydrophilic film 21 Water 22 Oil 100 Digital camera 101 Shooting lens 102 Optical viewfinder objective window 103 Auxiliary light emission Unit 104 power switch 110 imaging optical system 111 solid-state imaging device 112 shutter 112a shutter motor 113 iris 113a iris motor 114, 116 focus unit 114a focus controller 115 zoom lens 115a zoom motor 120 signal processing unit 120a analog processing (A / D) unit 120b Digital signal processing unit 120c Motor driver 121 System controller 122 Image signal processing unit 123 Image display control unit 124 Image compression unit 125 Media co Troller 126 AF / AE calculation unit 127 Key controller 128 Buffer memory 129 Internal memory 1200 Bus 130 Image display unit 140 External recording medium 150 Release switch 160 Shooting mode switch 170 Zoom switch 201 Liquid container 201a Tube 201b, 201c Cap 202 First electrode 203 Second electrode 204 Insulating film 205 Water repellent film 206 Hydrophilic film 207 Vertical alignment film 301 Insulating liquid 302 Conductive liquid 303 Nanoparticle 304 Liquid crystal

Claims (12)

An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
An optical element comprising: a second electrode insulated from the conductive liquid in the liquid container.   The refractive index variable liquid is composed of a light-transmitting dispersion medium and a dispersoid dispersed in the dispersion medium and having a light-transmitting refractive index different from that of the dispersion medium. The optical element according to claim 1.   The optical element according to claim 2, wherein the dispersoid includes nanoparticles.   The optical element according to claim 2, wherein the dispersoid is made of titanium oxide nanoparticles.   The optical element according to claim 2, wherein the dispersoid is made of alumina nanoparticles.   The optical element according to claim 2, wherein the dispersion medium is water.   The optical element according to claim 2, wherein the dispersion medium is an organic dispersion medium.   The optical element according to claim 2, wherein the dispersion medium is a hydrocarbon-based organic dispersion medium.   The optical element according to claim 1, wherein the refractive index variable liquid is a liquid containing liquid crystal. The optical element according to claim 1, wherein the refractive index variable liquid is a liquid containing a nematic liquid crystal. An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
A second electrode insulated against the conductive liquid in the liquid container,
The shape of the boundary surface between the insulating liquid and the conductive liquid changes according to the voltage applied between the first electrode and the second electrode, and the refractive index of the refractive index variable liquid. A lens unit characterized by changing. An insulating liquid and a conductive liquid, which are refractive index variable liquids that have different refractive indexes, are immiscible with each other, and each have optical transparency, and at least one of which changes the refractive index when a voltage is applied, are contained inside. A liquid container that transmits light at least in a predetermined optical axis direction;
A first electrode in contact with the conductive liquid in the liquid container;
A second electrode insulated from the conductive liquid in the liquid container;
By applying a voltage between the first electrode and the second electrode, the shape of the boundary surface between the insulating liquid and the conductive liquid is changed, and the refractive index of the refractive index variable liquid is also changed. A control unit to change,
An imaging apparatus comprising: an imaging element that forms an image signal representing the subject light by imaging the insulating liquid and subject light that has passed through the conductive liquid on a surface thereof.

Images