JP2006243573A - Liquid crystal lens and camera module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal lens which allows an optical image of high definition to be obtained with a camera module made thin as much as possible even in the case that the camera module is a camera module with AF incorporating a liquid crystal lens unit, and to provide a camera module having the liquid crystal lens mounted thereon. <P>SOLUTION: The liquid crystal lens has two transparent substrates, at least one of which has a pattern electrode formed thereon, disposed with a prescribed space between them and has a liquid crystal disposed in this space and has such a configuration that a spacer is formed in almost all the outer periphery of a lens effective area defined by the pattern electrode, by a member having a light shielding property to be able to shield light incident on the outer periphery of the lens effective area by the spacer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal lens and a camera module, and in particular, even if a liquid crystal lens unit is incorporated to form a camera module with AF, a high-definition optical image with a high contrast can be obtained while reducing the thickness of the camera module as much as possible. The present invention relates to a liquid crystal lens that can be obtained and a camera module equipped with the same.

  In recent years, research and development of a single-focus camera module that has a lens system, a photoelectric conversion element that photoelectrically converts an optical image that has passed through the lens system, and a lens barrel on which these members are mounted, which is mounted on a digital camera or the like This single focus type camera module is required to be smaller and thinner and to improve image quality. Particularly in recent years, even in small mobile terminals such as mobile phones, the image quality of camera modules has been improved, and further reduction in size and thickness has been demanded.

  Therefore, a single focus type camera module corresponding to such an application has been proposed (see, for example, Patent Document 1). The configuration of this conventional camera module is shown in FIG.

  As shown in this drawing, a single-focus camera module 100 described in Patent Document 1 includes a lens barrel 111 in which an aperture stop 101 that covers an optical surface periphery on the incident light side of a lens system 112 is formed. Incident light (optical image) 140 restricted by the aperture stop 101 is condensed on a photoelectric conversion element 113 composed of a C-MOS image sensor or a CCD image sensor. The aperture stop 101 functions as a stop for restricting the opening of the light beam incident on the lens system 112, and thereby a single-focus camera module capable of acquiring a high-definition optical image with high contrast, Will be able to.

  There is also a demand to add an autofocus function to a small and thin single focus type camera module. The camera module to which the autofocus function is added (hereinafter referred to as a camera module with AF) is incident on the camera by moving at least one of a plurality of lenses constituting the lens system by a lens driving mechanism. The focus of light can be made variable. However, this camera module with AF requires a lens operating area, a space for arranging a lens driving mechanism, etc., as compared with the above-described single focus type camera module, and the camera module with AF is made smaller and thinner. Was considered difficult. If the AF-equipped camera module cannot be reduced in size and thickness, it cannot be mounted on a small mobile device.

  Therefore, a liquid crystal lens unit has been proposed in which two liquid crystal lenses, a P-polarization liquid crystal lens and an S-polarization liquid crystal lens, are stacked in order to function as a variable focus lens by changing the refractive index of incident light. (For example, refer to Patent Document 2).

  If the liquid crystal lens unit having the above-described configuration is used, a polarization-independent liquid crystal lens can be obtained, and a variable focus function can be achieved by electrically controlling the liquid crystal layer provided in the liquid crystal lens. The operating area of the lens in the attached camera module, the lens driving mechanism and the like are not necessary.

Japanese Patent Laid-Open No. 2001-221904 (page 3-4, FIG. 1) JP 61-156221 A (page 2-3, FIG. 3)

  In the single-focus camera module 100 described in Patent Document 1, since the aperture stop 101 is configured by the lens barrel 111, the thickness of the thickness of the lens barrel 111 is the thickness on the optical axis side of the camera module 100. Will be increased. If the liquid crystal lens unit described in Patent Document 2 is incorporated into the single focus type camera module 100 to form a camera module with AF, the thickness of the camera module is further increased by the amount of the liquid crystal lens unit. End up.

  Therefore, it is clear that it is more difficult to achieve a reduction in size and thickness in such a camera module with AF.

  Therefore, the present invention solves the above-described problem and obtains a high-definition optical image with high contrast by reducing the thickness of the camera module as much as possible even if a liquid crystal lens unit is incorporated to form a camera module with AF. An object of the present invention is to provide a liquid crystal lens and a camera module having the liquid crystal lens mounted thereon.

  In order to achieve the above-described object, the liquid crystal lens of the present invention and a camera module equipped with the liquid crystal lens basically adopt the configuration described below.

  The liquid crystal lens according to the present invention is defined by a pattern electrode in a liquid crystal lens in which two transparent substrates each having a pattern electrode formed on at least one side are fixedly arranged with a predetermined gap and liquid crystal is arranged in the gap. A spacer is formed of a light-shielding member over almost the entire outer periphery of the effective lens area, and light incident on the outer periphery of the effective lens area can be blocked by the spacer. Is.

  In the liquid crystal lens according to the present invention, the spacer described above is formed of a light-shielding member and shields incident light, and has a function of fixing and arranging two transparent substrates with a predetermined gap. It is characterized by having.

  Further, the liquid crystal lens according to the present invention is characterized in that the above-described spacer is made of a metal film and functions as a heater electrode for directly heating the liquid crystal.

  In the liquid crystal lens according to the present invention, the liquid crystal lens described above includes a first liquid crystal lens and a second liquid crystal lens to form a liquid crystal lens unit, and the second liquid crystal lens serves as the first liquid crystal lens. The alignment direction is perpendicular to the alignment direction, and the layers are stacked and arranged.

  In the liquid crystal lens according to the present invention, the liquid crystal injection holes in the first and second liquid crystal lenses are stacked so as not to overlap each other.

  In the camera module according to the present invention, the lens includes a lens system, a photoelectric conversion element that receives an optical image that has passed through the lens system, and a lens barrel that mounts the lens system and the photoelectric conversion element. The system includes one of the liquid crystal lenses described above.

In the camera module according to the present invention, the spacer described above functions as an aperture stop for light incident on the lens system.

  If the configuration of the present invention is adopted, it is not necessary to separately prepare a diaphragm in the optical system including the liquid crystal lens, and the length of the camera module in the optical axis direction can be shortened.

  The liquid crystal lens of the present invention is provided with two transparent substrates each having a pattern electrode formed on at least one side thereof, arranged with a predetermined gap facing each other on the surface on which the electrode is formed, and liquid crystal in the gap. The arrangement is arranged. In this liquid crystal lens, a spacer is formed by a light-shielding member over almost the entire outer periphery of the lens effective area defined by the pattern electrode, and light incident on the outer periphery of the lens effective area is The spacer can shield light.

  Hereinafter, preferred embodiments of a liquid crystal lens according to the present invention will be described in detail with reference to the drawings. FIG. 1A is a cross-sectional view showing a schematic configuration of the liquid crystal lens of the present invention, and FIG. 1B shows the relationship between the spacer and the lens effective area of the liquid crystal lens shown in FIG. It is a drawing.

  As shown in FIG. 1A, a liquid crystal lens 7a according to the present invention includes a transparent substrate 3a on which a transparent electrode 5a is formed and a transparent substrate 3b on which a transparent electrode 5b is formed. Are arranged between the transparent substrates 3a and 3b via a spacer 1a, and the liquid crystal 2 is sealed in a gap defined by the spacer 1a. The transparent electrodes 5a and 5b are formed with a pattern electrode composed of a plurality of concentric ring-shaped electrodes, and the other transparent electrode is formed with a common electrode. By applying a stepped voltage to adjacent annular electrodes in the pattern electrode formed on the transparent electrode, the focal position with respect to the incident light incident on the liquid crystal lens 7a can be varied. Note that pattern electrodes may be formed on both the transparent electrodes 5a and 5b.

  In addition, the spacer 1a shown in this embodiment is configured to keep the gap constant by using a sealant in which spherical or cylindrical gap defining members are dispersed, and this spacer 1a shields the light shown below. It has a structure that combines the function and the function of keeping the gap constant.

  Further, as shown in FIG. 1 (b), the spacer 1a disposed on the liquid crystal lens 7a is substantially at the outer edge of the pattern electrode 8 formed of one of a plurality of concentric ring-shaped electrodes formed on one transparent electrode. It is formed over the entire surface. A liquid crystal injection port 6a for enclosing the liquid crystal 2 is provided in a part of the spacer 1a. Hereinafter, the inner area of the pattern electrode 8 will be described as the lens effective area 4. With this configuration, only incident light passing through the lens effective area 4 in the liquid crystal lens 7a of the present invention is acted as a lens.

  Moreover, since the member which comprises the spacer 1a is provided with the function mentioned above, it is important to make it the member which can light-shield. As a member for shielding light, an adhesive containing a light shielding material containing a black pigment or the like can be used as a sealing agent. In this embodiment, the spacer 1a has an example in which the function of blocking incident light and the function of a seal for fixing the transparent substrates 3a and 3b at a constant interval are shown. Instead, a member that shields light such as a metal film is provided as a spacer between the two transparent substrates 3a and 3b, and separately, the two transparent substrates 3a and 3b are fixed with a sealant. It does not matter.

  Further, this metal film may function as a heater electrode for directly heating the liquid crystal 2. When setting it as this form, it is necessary to form a heater electrode in the same transparent base | substrate 3a surface as the pattern electrode 8. FIG. This heater electrode is provided to alleviate a decrease in response speed of the liquid crystal 2 particularly in a low temperature environment. Thus, by using the spacer 1a as the heater electrode, the liquid crystal lens 7a that can be operated at a sufficient speed in practical use under various temperature environments, particularly in a low temperature environment, can be obtained.

  In this way, the spacer 1a can block all light incident on the area other than the liquid crystal injection port 6a and the lens effective area 4 and function as an aperture stop. Only the light passing through the lens effective area 4 can act as a lens.

  Next, a configuration example of the camera module of the present invention in which the liquid crystal lens 7a described above is installed in the camera module will be described with reference to FIG. FIG. 2 is a schematic diagram showing a configuration example in which a liquid crystal lens is incorporated into a single focus camera module to form a camera module with AF.

  As shown in FIG. 2, the camera module 15 includes a lens system 12 that condenses the optical image that has passed through the lens barrel 11 at a predetermined position in the subsequent stage, and an optical image that is condensed by the lens system 12. The photoelectric conversion element 13 includes a CCD image sensor or a C-MOS image sensor that performs photoelectric conversion. Only the camera module 15 functions as a single-focus camera module. Note that the incident surface side of the light incident on the camera module 15 does not have an aperture stop formed by the edge of the lens barrel 11 shown in the prior art as shown in the drawing.

  Then, a liquid crystal lens unit 7 composed of two liquid crystal lenses 7a having basically the same configuration is provided before the light incident on the camera module 15 is incident to form a camera module with AF. In the following description, the liquid crystal lens 7a is shown as a first liquid crystal lens, and the liquid crystal lens disposed in the subsequent stage is shown as a second liquid crystal lens 7b.

  The first and second liquid crystal lenses 7a and 7b constituting the liquid crystal lens unit 7 are basically the same except for the arrangement form of the liquid crystal inlet described later, and are polarization independent. Thus, the two liquid crystal lenses are stacked and arranged so that the alignment direction of the liquid crystal is perpendicular. The liquid crystal lens unit 7 is configured such that the lens effective areas 4 respectively provided in the first and second liquid crystal lenses 7a and 7b overlap at the same position.

  Next, the arrangement relationship of the liquid crystal injection holes in the first and second liquid crystal lenses will be described with reference to FIG. FIG. 3 is a perspective view showing the arrangement relationship of the liquid crystal inlets of the first and second liquid crystal lenses in the liquid crystal lens unit.

  As shown in FIG. 3, when the first and second liquid crystal lenses 7a and 7b are stacked, the liquid crystal injection ports 6a and 6b are not overlapped at the same position, for example, as shown in this drawing. It is preferable that the two liquid crystal lenses are laminated and installed so that the liquid crystal injection ports 6a and 6b are in symmetrical positions. In this way, the first and second liquid crystal lenses 7a and 7b are not the lens effective area 4 and the liquid crystal injection ports 6a and 6b so that the liquid crystal injection ports 6a and 6b do not overlap each other. Since the spacers 1a and 1b functioning as an aperture stop (in this embodiment, the seal also functions as the spacer) are disposed over the entire surface of the liquid crystal, incident light is transmitted from the periphery of the liquid crystal lens unit. The entry into the camera module 15 can be suppressed as much as possible.

In the drawing, the liquid crystal injection ports 6a and 6b are connected to the first and second liquid crystal lenses 7a and 7b.
Although the example provided in the position which opposes the rectangular-shaped transparent base | substrates 3a and 3b in b was shown, it is not limited to this, It is on the same side so that this liquid crystal injection port 6a and 6b may not overlap. It may be provided, or may be provided on each adjacent side. Moreover, you may comprise using what made the shape of transparent base | substrate 3a, 3b circular.

  Next, the operation of the camera module of the present invention provided with the liquid crystal lens unit 7 will be described with reference to FIG. FIG. 4 is a view for explaining the operation of the camera module of the present invention.

  Incident light 40 having two polarization components of S-polarized light and P-polarized light is incident on the liquid crystal lens unit 7 installed in the camera module 15. At this time, the first and second liquid crystal lenses 7a and 7b are provided with spacers 1a and 1b, and the spacers 1a and 1b function as an aperture stop. The incident light 40 is transmitted only from the above.

  In addition, the transmitted light 41 transmitted through the lens effective area 4 in the first and second liquid crystal lenses 7a and 7b is refracted by the lens system 12 disposed in the subsequent stage of the first and second liquid crystal lenses 7a and 7b. An image is formed on the photoelectric conversion unit 13. In the example shown in the drawing, the lens system 12 including two lenses is shown. However, in order to correct the aberration of the transmitted light 41, another lens may be newly arranged, or the camera Depending on the specifications of the module, this lens system 12 may be a single lens.

  Then, the variable focus type first and second liquid crystal lenses 7a and 7b control the respective polarization components in the optical image of the incident light 40 to the photoelectric conversion unit 13 by driving means (not shown) provided outside. Thus, it can function as a camera module with AF.

  In the first and second liquid crystal lenses 7a and 7b, spacers 1a and 1b are disposed in the outer region of the lens effective area 4 over almost the entire area as described above. Since the spacers 1a and 1b are not installed in the 6a and 6b, when the incident light 40 is transmitted through the first liquid crystal lens 7a, the incident light is transmitted from the liquid crystal injection port 6a. However, as described above, since the liquid crystal injection port 6b and the liquid crystal injection port 6a in the liquid crystal lens unit 7 are installed at positions where they do not overlap, the light transmitted through the liquid crystal injection port 6a enters the second liquid crystal lens 7b. Light is shielded by the installed spacer 1b and light other than the lens effective area 4 of the first and second liquid crystal lenses 7a and 7b does not enter the camera module 15.

  As described above, the thickness of the camera module can be obtained by using the spacers 1a and 1b constituting the first and second liquid crystal lenses 7a and 7b so as to function as an aperture stop. As much as possible, a high-definition optical image with high contrast can be obtained.

  In addition, since the spacers 1a and 1b functioning as the aperture stop are disposed inside the liquid crystal lens, it is not necessary to separately install the aperture stop in the lens barrel 11 as in the prior art. Therefore, it is possible to provide a small camera module in which the length of the module in the optical axis direction is shortened by the thickness of the aperture stop provided in the lens barrel 11.

  In the present embodiment, the spacers 1a and 1b are arranged so that the shape of the spacers 1a and 1b is substantially the same as the diameter of the lens effective area 4 in the liquid crystal lens unit 7. Therefore, the transparent bases 3a and 3b of the lens effective area 4 are arranged. It is also possible to reduce the uneven thickness of the liquid crystal layer.

  Further, the present invention is not limited to the configuration of the first and second liquid crystal lenses 7a and 7b shown in the above-described embodiment, and the shape of the cell in which the liquid crystal is sealed may be different. For example, a liquid crystal lens in which one surface or both surfaces of the cell are concave, convex, or Fresnel lens shape may be used. Further, in this embodiment, the example in which the first and second liquid crystal lenses 7a and 7b are superposed one by one has been described. However, the first and second liquid crystal lenses 7a and 7b may be plural in number. I do not care.

  Further, in the present embodiment, the configuration example in which the liquid crystal lens unit 7 is disposed on the front surface of the camera module 15 is shown, but even if the liquid crystal lens unit 7 is installed inside the camera module 15, the function as an aperture stop is achieved. Achieved.

Next, a modification of the camera module of the present invention will be described.
FIG. 5 is a diagram showing a schematic configuration in which the spacer constituting the liquid crystal lens of the present invention described above serves as a field stop of the camera module 15.

  As shown in FIG. 5, the camera module 15 shown here includes a lens barrel 11, a lens system 12, and a photoelectric conversion unit 13, and two cameras module 15 are arranged so that the orientation direction is perpendicular to the inside of the camera module 15. The liquid crystal lens unit 7 in which the first and second liquid crystal lenses 7a and 7b are stacked is fixed.

  An aperture stop 16 is integrated with the lens barrel 11 and is disposed in front of the lens system 12 so as to cover the periphery of the optical surface on the incident light side of the lens system 12, as in the prior art. The configuration of the liquid crystal lens unit 7 shown here is the same as that shown above, but the spacers 1a and 1b in the first and second liquid crystal lenses 7a and 7b receive the light emitted from the lens system 12. This is different from the above-described embodiment in that it is arranged at a position where it can block light having a predetermined angle of view or more, and has a field stop function. As a result, it is possible to prevent incident light having an angle of view more than necessary from entering the photoelectric conversion unit 13 regardless of the imaging effect.

Next, the operation of the camera module when the liquid crystal lens unit 7 described above is installed inside the camera module 15 will be described with reference to this drawing.
Incident light 40 enters the lens system 12 from the front surface of the camera module 15. The light emitted from the lens system 12 is incident on the liquid crystal lens unit 7 including the first liquid crystal lens 7a and the second liquid crystal lens 7b, and is emitted after birefringence occurs in the respective liquid crystal lenses. To form an image.

  Further, the spacers 1a and 1b formed on the first and second liquid crystal lenses 7a and 7b block light other than a predetermined field angle of light from the lens system 12, and function as a field stop as a camera module. be able to.

  In this way, the spacer 1a, 1b disposed on the liquid crystal lens unit 7 uses a light blocking member, and the light incident on the area other than the lens effective area 4 of the liquid crystal lens is blocked by the spacer 1a, 1b. The camera module with AF in which the field stop is formed inside 15 can be obtained.

  The liquid crystal lens according to the present invention reduces the height of the camera module relative to the optical length in the camera module with AF, and is particularly suitable for a camera, a digital camera, a movie camera, a camera unit of a camera-equipped mobile phone, a car, etc. It is suitable for cameras that are mounted and used for rear-viewing monitors, endoscope camera units, and the like.

It is sectional drawing and the top view which show schematic structural example of the liquid crystal lens concerning this invention. It is drawing which shows the structural example of the camera module of this invention. It is a perspective view which shows the structural example of the camera module of this invention. It is drawing which shows the effect | action of the camera module of this invention. It is drawing which shows the modification and effect | action of the camera module of this invention. It is drawing which shows the structural example of the conventional camera module.

Explanation of symbols

1a, 1b Spacer 2 Liquid crystal 3a, 3b Transparent base 4 Lens effective area 5a, 5b Transparent electrode 6a, 6b Liquid crystal inlet 7 Liquid crystal lens unit 7a First liquid crystal lens (liquid crystal lens)
7b Second liquid crystal lens 8 Pattern electrode 11 Lens barrel 12 Lens system 13 Photoelectric conversion unit 15 Camera module 40 Incident light 41 Transmitted light

Claims (7)

In a variable focus type liquid crystal lens in which at least one transparent substrate having a pattern electrode formed thereon is arranged with a predetermined gap and liquid crystal is arranged in the gap,
Over almost the entire outer periphery of the lens effective area defined by the pattern electrode, a spacer is formed of a light-shielding member,
A liquid crystal lens characterized in that light incident on the outer periphery of the lens effective area can be shielded by the spacer.   2. The spacer according to claim 1, wherein the spacer is formed of a light-shielding member and has a function of blocking incident light, and a function of fixing and arranging the two transparent substrates with a predetermined gap. The liquid crystal lens described.   The liquid crystal lens according to claim 1, wherein the spacer is made of a metal film and functions as a heater electrode that directly heats the liquid crystal. The liquid crystal lens has a first liquid crystal lens and a second liquid crystal lens,
4. The second liquid crystal lens according to claim 1, wherein the second liquid crystal lens is disposed so as to be laminated with the alignment direction orthogonal to the alignment direction of the first liquid crystal lens. 5. Liquid crystal lens.   5. The liquid crystal lens according to claim 4, wherein the liquid crystal injection holes in the first and second liquid crystal lenses are laminated so as not to overlap each other. In a camera module comprising a lens system, a photoelectric conversion element that receives an optical image that has passed through the lens system, and a lens barrel on which the lens system and the photoelectric conversion element are placed,
The lens system includes a liquid crystal lens according to any one of claims 1 to 5, and a variable focus camera module. The camera module according to claim 6, wherein the spacer functions as an aperture stop for light incident on the lens system.

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