JP2004198780A - Optical low pass filter and imaging device using the filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality and highly reliable optical low pass filter in which an effective optical area is secured even though the size is made small, mechanical impact resistance is not degraded and front and rear discrimination of a luminous flux separation direction and an optical low pass filter main surface is easily conducted so as to obtain a necessary luminous flux separation pattern and to provide an imaging device using the filter. <P>SOLUTION: A rectangular parallelepiped optical filter 1 has a square main surface and a luminous flux separating direction to separate and emit the light beams, which are being made incident on the main surface, into a prescribed direction. One or more markings M1, which indicate luminous flux separation direction, are formed on one of the main surfaces of the incident side or the emitting side in a non-point symmetry manner with respect to the center of the main surface at a tip part. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical low-pass filter such as a crystal birefringent plate used for a video camera or an electronic still camera, or to a structure of an imaging device using the same.
[0002]
[Prior art]
2. Description of the Related Art An image pickup apparatus such as a general video camera and an electronic still camera includes a coupling optical system, a color correction filter such as an infrared cut filter, various optical filters such as an optical low-pass filter, a CCD ( The solid-state imaging devices such as a charge coupled device (MOS) and a metal oxide semiconductor (MOS) are arranged in this order.
[0003]
Among these configurations, the optical low-pass filter filters an optical false signal detected by the imaging device, thereby preventing the image quality of the video camera from being degraded. That is, when a subject having color information (such as lattice fringes) close to the pixel pitch of an imaging device such as a CCD is photographed, a pseudo signal different from the original video information is generated in the imaging device, and the color of the output video is blurred. Moire phenomenon sometimes occurred. An optical low-pass filter is used to block and attenuate a spatial frequency component related to such a pseudo signal. The optical low-pass filter has, for example, a configuration in which at least one or more quartz birefringent plates are used, and an antireflection film is generally applied to a main surface portion exposed on the surface thereof. The incident light is separated into an ordinary ray and an extraordinary ray by the birefringence effect of the crystal to be emitted light, and has a predetermined light beam separation direction and a predetermined separation width on its main surface. In such a crystal birefringent plate, a notch or the like is generally formed at an end of the main surface to clearly indicate the light beam separation direction. (For example, see Patent Document 1).
[0004]
However, such an explicit means is weak against mechanical impacts, such as the generation of minute cracks when processing the notch, which tends to cause cracks and chips. Further, by forming a notch or the like, an optically effective area due to the small size of the optical low-pass filter may not be secured. Furthermore, recently, as an optical low-pass filter for an electronic still camera, a filter having a substantially square plate shape has been adopted in accordance with the shape of a solid-state imaging device such as a CCD. In this case, in addition to the determination of the light beam separation direction of the optical low-pass filter, the determination of the main surface on the incident side and the output side of the optical low-pass filter, and the vertical direction when rotated by 90 ° at the center point of the main surface of the optical low-pass filter. There is a need for lateral discrimination. For example, depending on the luminous flux separation pattern of the optical low-pass filter, arranging the main surfaces on the incident side and the outgoing side of the optical low-pass filter incorrectly results in a luminous flux separation pattern that is different from the originally required one, and sufficiently improves the performance of the optical low-pass filter. There was something that could not be demonstrated.
[0005]
Further, an imaging device such as a CCD has a relatively wide sensitivity characteristic, and responds to light in a part of the infrared region in addition to light in the visible region. However, in an imaging apparatus used for normal subject photographing, infrared incident light becomes stray light, which causes a decrease in resolution, image spots and unevenness, and adversely affects color reproducibility. In order to eliminate such adverse effects and correct optical characteristics, the optical low-pass filter includes an infrared cut filter, an ultraviolet cut filter, and an infrared ultraviolet cut filter as color correction filters. For example, as an infrared cut filter, a member such as a colored glass or a colored resin plate may be attached to the optical low-pass filter or a multilayer infrared cut coat material such as Al2O3, TiO2, and SiO2 (hereinafter referred to as an infrared cut coat) depending on the application. ) Is formed on the optical low-pass filter, and these are combined as needed. Recently, as the optical low-pass filter is reduced in size and thickness, a coating material is often formed as the color correction filter.
[0006]
However, when the above-mentioned coating material is formed only on one main surface of the optical low-pass filter, or when one coating surface of the optical low-pass filter is formed with a multilayered coating material more than the other main surface, it is visually observed. It was extremely difficult to determine on which principal surface the coating material was formed, or on which principal surface a more multilayered coating material was formed. That is, when assembling the optical low-pass filter to the imaging apparatus, the worker cannot recognize the main surface on the side on which the coating material is formed or the main surface on the side on which the multilayer coating material is formed, and The risk of misplacement was also very high.
[0007]
In particular, in recent years, the size of imaging devices such as video cameras has been reduced, and the distance from an optical low-pass filter disposed in front of an imaging device such as a CCD has also become shorter. The quartz birefringent plate was sometimes arranged closer to the CCD than the main surface. At this time, there is a problem that the unevenness of the main surface becomes an optical foreign matter and becomes conspicuous as noise on an image to deteriorate the quality of video output. This is because, in the case of a coating material in which dozens of multilayer thin films are formed on the main surface of an optical low-pass filter by vapor deposition or the like, such as an infrared cut coat, the main surface is particularly likely to be uneven, and as an optical foreign matter, It is conceivable that it appears more prominently.
[0008]
[Patent Document 1]
JP-A-63-109901 [0009]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above problems, and secures an optically effective area even if it is miniaturized, without lowering mechanical shock, and has a required light beam separation pattern and optical characteristics. It is an object of the present invention to provide a high-quality and more reliable optical low-pass filter that does not degrade the obtained and video-output image quality, and an imaging device using the optical low-pass filter.
[0010]
[Means for Solving the Problems]
Therefore, the optical low-pass filter of the present invention is a rectangular parallelepiped optical low-pass filter having a main surface rectangular shape and having a light beam separation direction in which light rays incident on the main surface are separated in a predetermined direction and emitted. Alternatively, one or more markings indicating the light beam separation direction are formed on one of the main surfaces on the emission side in an asymmetry with respect to the center of the main surface.
[0011]
As a marking formed asymmetrically at the end with respect to the center of the main surface, a marking indicating a light beam separation direction only near one corner of the main surface on one main surface on the incident side or the output side. May be formed, or a first marking indicating a light beam separation direction and a second marking are formed on one main surface of the incident side or the output side near two adjacent corners of the main surface. Alternatively, a first marking, a second marking, and a third marking indicating a light beam separation direction are formed near one of three corners of the main surface on one of the main surfaces on the incident side or the output side. Is also good.
[0012]
Further, a rectangular parallelepiped optical low-pass filter having a light-flux separation direction in which light rays incident on the main surface in a main-surface rectangular shape are separated in a predetermined direction and emitted, and on one side surface of the optical low-pass filter, One or more markings indicating a light beam separation direction are formed asymptotically with respect to the center of the side surface.
[0013]
As one of the markings formed asymmetrically with respect to the center of the side surface, a marking indicating the light beam separation direction may be formed only at one edge of one side on one side surface of the optical low-pass filter.
[0014]
Further, an image pickup apparatus in which the optical low-pass filter is attached to an opening of a package in which an image pickup device is stored, wherein the optical low-pass filter has a coating material formed only on one main surface side, or One main surface side is formed with a multilayer coating material from the other main surface side, and the main surface having the coating material, or the main surface having a more multilayer coating material, is used as the main surface on the incidence side of the optical low-pass filter. The package is attached to an opening of the package toward the outside of the package.
[0015]
【The invention's effect】
According to claims 1 to 4, one or more markings indicating a light beam separation direction are provided on one of the main surfaces on the entrance side or the exit side of the optical low-pass filter at the end with respect to the center of the main surface. Since one or more markings indicating the light beam separation direction are formed symmetrically with respect to one side surface of the optical low-pass filter or asymmetry with respect to the center of the side surface, the optical separation indicated by the markings may be performed. In a state where the direction is recognized, it can be arranged on the image sensor. In addition, it is possible to determine whether the surface is a light incident surface or a light emitting surface according to the place where the marking is formed. Furthermore, even with an optical low-pass filter having a substantially square main surface corresponding to the shape of the main surface of a solid-state image sensor such as an electronic still camera, the image sensor may be used in a state where the vertical and horizontal directions of the main surface are recognized. Can be arranged.
[0016]
In other words, according to the marking of the optical low-pass filter of the present invention, the luminous flux separation direction in the optical low-pass filter having a substantially square main surface, the distinction between the entrance-side principal surface and the exit-side principal surface, and the center point of the principal surface are determined. It is possible to simultaneously determine the vertical direction and the horizontal direction when rotated by 90 °.
[0017]
Furthermore, by forming the marking on the end of the main surface of the optical low-pass filter or on the side surface of the optical low-pass filter, the optical effective area can be reduced even when the size is reduced, as compared with a conventional mark formed by a notch or the like. Since it is easy to secure and no mechanical grinding is performed on the optical low-pass filter, no crack or the like is generated. When an optical low-pass filter having a substantially square main surface corresponding to the main surface shape of a solid-state imaging device such as a CCD for an electronic still camera is used, the shape of a package accommodating the imaging device can be supported. Since an optical low-pass filter can be attached as a member, the overall size of the imaging device can be reduced.
[0018]
Therefore, even if the size is reduced, an optically effective area is secured, and the mechanical impact is not reduced. Since the originally required light beam separation pattern is obtained, the performance of the optical low-pass filter can be sufficiently exhibited. The quality of the video output is not degraded. An optical low-pass filter with higher quality and higher reliability can be provided.
[0019]
According to the second aspect, in addition to the above-described functions and effects, the marking formed asymmetrically at the end of the main surface is formed only near the corner of the main surface. Since an effective area can be more easily secured, and a marking forming location can be easily specified on the main surface of the optical low-pass filter, the productivity is high.
[0020]
According to the fourth aspect, in addition to the above-described functions and effects, the marking is formed on one side surface of the optical low-pass filter, and the marking indicating the light beam separation direction is formed only at the end of one side. Since the entire main surface can be secured as an optically effective area, and a marking forming location can be easily specified on the side surface of the optical low-pass filter, the productivity is high.
[0021]
According to the fifth aspect, the main surface of the optical low-pass filter on which the coating material or the multi-layer coating material is formed is set as the main surface on the incident side, and attached to the opening of the package toward the outside of the package. Therefore, the main surface on which the coating material or the multilayer coating material is formed can be arranged separately from the image sensor. Therefore, the unevenness of the coating material does not become an optical foreign matter and becomes noticeable as noise on the image, so that the quality of the video output is not deteriorated. A high-quality and highly reliable imaging device can be provided.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described with reference to the drawings, taking an optical low-pass filter as an example. FIG. 1 is a diagram showing a first embodiment according to the present invention, and FIG. 2 is a diagram showing a manufacturing method. 3 and 4 are perspective views of an optical low-pass filter showing a modified example thereof.
[0023]
The optical low-pass filter according to the present embodiment has a single-plate configuration of a crystal birefringent plate 1 having a substantially square main surface as shown in FIG. As is well known, the crystal birefringent plate separates incident light into an ordinary ray and an extraordinary ray by using the birefringence effect of quartz to make outgoing light, and the light separation direction and separation width are appropriately adjusted by predetermined parameters. Can be. An infrared cut coat 1a is formed as a color correction filter on the main surface of the crystal birefringent plate 1 on the light incident side. Although the details of the coat 1a are not shown, a high-refractive dielectric thin film (for example, TiO2) and a low-refractive dielectric thin film (for example, SiO2 or the like) are alternately laminated from 10 to 60 layers to form a multilayer. A film is formed.
[0024]
The crystal birefringent plate 1 is set so as to separate light rays in, for example, a 45 ° direction (0 ° in the horizontal direction on the right side with respect to the main surface and 45 ° counterclockwise). On the side main surface, a dot-like marking M1 is formed by immortal ink or laser in the vicinity of a corner 11 of the main surface in the light beam separation direction.
As shown in FIG. 1 (b), the crystal birefringent plate 1 configured as described above uses a main surface of the crystal birefringent plate on which the coating material 1a is formed as an incident side main surface and picks up an image of a CCD or the like. It is arranged in a direction in which it is separated from the element 4 and is attached to, for example, an opening 51 of a package 5 for accommodating a CCD, and is incorporated into an imaging device such as a video camera or an electronic still camera together with a coupling optical system (not shown).
[0025]
In the first embodiment of the present invention, since the marking M1 is formed only near one corner of the main surface on the light incident surface of the crystal birefringent plate 1, for example, the corner where the marking M1 is formed is formed. It is clearly indicated that the optical separation direction exists in the direction of 11, and it is possible to determine whether the front surface or the back surface is the main surface on which the marking M1 is formed and the main surface on which the coating material 1a is formed. It becomes. Furthermore, the crystal birefringent plate 1 has a substantially square main surface. Even if the main surface is rotated by 90 ° at the center point of the main surface, the vertical direction and the horizontal direction can be distinguished.
[0026]
Next, a method of forming the optical low-pass filter will be described with reference to the schematic diagram of FIG.
As shown in FIG. 2A, a birefringent plate wafer W is obtained in which light is separated in a 45 ° direction (arrows in the figure) and both main surfaces are polished and polished.
As shown in FIG. 2 (b), in order to form an infrared cut coat on the incident surface W1 of the wafer W, dielectric thin films (TiO2 and SiO2) H are alternately laminated by means such as a vacuum deposition method to form a multilayer film. To form
As shown in FIG. 2 (c), such an optical low-pass filter wafer W is adhered on a support S with a water-soluble adhesive, and cut into small pieces in a matrix by a dicing blade.
As shown in FIG. 2D, a laser beam is applied to a corner portion of the cut individual wafer W corresponding to the light beam separating direction, and a part of the dielectric thin film is removed to form a marking M. .
As shown in FIG. 2E, the water-soluble adhesive is dissolved and separated into individual optical low-pass filters 1.
[0027]
The method for manufacturing the optical low-pass filter according to the present invention is not limited to the above method. For example, the marking may be formed first by irradiating a laser before cutting the dicing blade, or the marking may be formed by imprinting ink by stamping or masking instead of laser.
[0028]
It should be noted that the present invention is not limited to the marking form of the first embodiment, but may be that shown in FIG.
[0029]
The crystal birefringent plate 1 of FIG. 3A is set so as to separate light rays in, for example, a 135 ° direction, and an infrared cut coat 1a is formed as a color correction filter on a light incident side main surface. An antireflection coat 1b is formed on the main surface. Although the infrared cut coat 1a is not shown in detail, a high-refractive dielectric thin film (for example, TiO2) and a low-refractive dielectric thin film (for example, SiO2 or the like) are alternately laminated from 10 to 60 layers. Thus, a multilayer film is formed. Although the antireflection coat 1b is not shown in detail, two to five layers of a high-refractive dielectric thin film (for example, TiO2) and a low-refractive dielectric thin film (for example, SiO2) are alternately laminated. To form a multilayer film. On the light-emitting side main surface of the crystal birefringent plate 1, near the three corners 11, 12, and 13, a dot-shaped first marking M1, a dot-shaped second marking M2 indicating a light flux separation direction, and A dot-like third marking M3 is formed by immortal ink or laser.
[0030]
Although not shown, the crystal birefringent plate 1 configured as described above is configured such that the main surface of the crystal birefringent plate on which the multilayer infrared cut coat material 1a is formed with respect to the antireflection coat 1b is located on the incident side. The main surface is arranged in a direction to be separated from an image pickup device such as a CCD, and is attached as a cover member to an opening of a package containing the CCD, for example, and is incorporated into an image pickup device such as a video camera or an electronic still camera together with a coupling optical system. .
[0031]
In such a configuration, the first marking M1, the second marking M2, and the third marking M3 are formed near the three corners of the main surface on the light emitting surface of the crystal birefringent plate 1, For example, it is specified that the optical separation direction exists in the direction of the corner 14 where the markings M1 to M3 are not formed on the main surface, the main surface on which the markings are formed is a light emitting surface, As the main surface on which the coat 1b is formed, the front and back can be distinguished. Furthermore, the crystal birefringent plate 1 has a substantially square main surface. Even if the main surface is rotated by 90 ° at the center point of the main surface, the vertical direction and the horizontal direction can be distinguished.
[0032]
The optical low-pass filter 2 of FIG. 3B has a configuration in which a crystal birefringent plate 21, a quarter-wave plate 22 (a crystal plate, a resin plate, or the like) and a crystal birefringent plate 23 are bonded together. The crystal birefringent plate 21 is set to separate light rays in, for example, a 0 ° direction, and has a function of separating incident light in the horizontal direction by the birefringence effect of quartz. On the light incident surface of the crystal birefringent plate 21, a coating material 2a such as an infrared cut coat is formed as a color correction filter. The quartz birefringent plate 23 is set, for example, to separate light rays in the 90 ° direction, and has a function of separating incident light in the 90 ° direction by the birefringence effect of quartz. In addition, an anti-reflection coating 2b is formed on the light exit surface of the crystal birefringent plate 23. Although the infrared cut coat 2a is not shown in detail, a high-refractive dielectric thin film (for example, TiO2) and a low-refractive dielectric thin film (for example, SiO2 or the like) are alternately laminated from 10 to 60 layers. Thus, a multilayer film is formed. Although the antireflection coating 2b is not shown in detail, a high refractive dielectric thin film (for example, TiO2) and a low refractive dielectric thin film (for example, SiO2 or the like) are alternately laminated to two to five layers. To form a multilayer film. On the light-incident side main surface of the optical low-pass filter 2, a first marking M1 having a dot shape is provided near two corners 211 and 212 adjacent to a side of the quartz birefringent plate 21 in the light beam separation direction. The second marking M2 is formed by immortal ink or laser.
[0033]
Although not illustrated, the optical low-pass filter 2 configured as described above is configured such that a main surface on which a multilayer infrared cut coat material 2a is formed with respect to the antireflection coat 2b of the optical low-pass filter is a main surface on the incident side. It is arranged in a direction in which it is separated from an image pickup device such as a CCD, and is attached to, for example, an opening of a package containing the CCD, and is incorporated into an image pickup device such as a video camera or an electronic still camera together with a coupling optical system.
[0034]
In such a configuration, the first marking M1 and the second marking M2 are formed in the light incident surface of the crystal birefringent plate 2 in the vicinity of two adjacent corners of the main surface. It is specified that the optical separation direction exists in the direction of the side on which the marking M1 and the second marking M2 are formed, the main surface on which each of the markings is formed is the light incident surface, and the infrared cut coat 2a is formed. It is possible to determine whether the front side or the back side is the main surface. Furthermore, the crystal birefringent plate 1 has a substantially square main surface. Even if the main surface is rotated by 90 ° at the center point of the main surface, the vertical direction and the horizontal direction can be distinguished. Note that the first marking M1 and the second marking M2 are also provided on the light emitting side main surface of the optical low-pass filter 2 near two corners adjacent to the side of the quartz birefringent plate 23 in the light beam separation direction. The marking M2 may be formed with immortal ink or laser.
[0035]
Further, as a marking formed asymptotically at the end with respect to the center of the main surface of the optical low-pass filter (quartz birefringent plate), the marking is not limited to the marking form only in the vicinity of the corner, but is shown in FIG. It may be something.
[0036]
The crystal birefringent plate 1 of FIG. 4A is set so as to separate light rays, for example, in the direction of 0 °, and an infrared cut coat 1a is formed on the light incident side main surface as a color correction filter. On the light-incident side main surface of the crystal birefringent plate 1, a dot-shaped first marking M1 indicating the light beam separation direction is formed only by the center of one side 15 using immortal ink or laser.
[0037]
Further, the crystal birefringent plate 1 of FIG. 4B is set so as to separate light rays in, for example, a 0 ° direction, and an infrared cut coat 1a is formed on a light incident side main surface as a color correction filter. . On the light-incident side main surface of the crystal birefringent plate 1, the first marking M <b> 1 having a dot shape indicating the light flux separation direction on the side 15, the second marking M <b> 2 having the dot shape, and the light separation direction is indicated on the side 16. A dot-like third marking M3 is formed by immortal ink or laser.
[0038]
Further, the crystal birefringent plate 1 of FIG. 4C is set so as to separate light rays, for example, in the direction of 0 °, and an infrared cut coat 1a as a color correction filter is formed on the light incident side main surface. . On the light incident side main surface of the crystal birefringent plate 1, a linear first marking M1 indicating the light beam separation direction is formed along the side 15 with immortal ink or laser.
[0039]
In this manner, one or more markings may be formed on any of the specific sides, and markings that are asymmetry at the end with respect to the center of the main surface of the optical low-pass filter may be formed.
[0040]
Although not shown, the crystal birefringent plate 1 configured as described above is separated from an image pickup device such as a CCD with the main surface of the crystal birefringent plate on which the infrared cut coat material 1a is formed as the main surface on the incident side. For example, it is mounted as a cover member in an opening of a package for accommodating a CCD, and is incorporated into an imaging device such as a video camera or an electronic still camera together with a coupling optical system.
[0041]
Next, an optical low-pass filter according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a second embodiment according to the present invention.
[0042]
The optical low-pass filter according to the present embodiment has a single-plate configuration of a quartz birefringent plate 3 having a substantially square main surface as shown in FIG. As is well known, the crystal birefringent plate separates incident light into an ordinary ray and an extraordinary ray by using the birefringence effect of quartz to make outgoing light, and the light separation direction and separation width are appropriately adjusted by predetermined parameters. Can be. An antireflection coating 3a is formed on the main surface of the quartz birefringent plate 3 on the light incident side. Although not shown in detail, the coat 3a is formed by alternately stacking two to five layers of a high-refractive dielectric thin film (for example, TiO2) and a low-refractive dielectric thin film (for example, SiO2). A film is formed.
[0043]
The crystal birefringent plate 3 is set to separate light rays in, for example, a 45 ° direction. On the side surface 31 above the incident surface of the crystal birefringent plate 3, the light beam separating direction is set to the right end 311 in the long side direction. Marking M4 shown is formed by immortal ink or laser. In addition, in the embodiment of the present invention, since the marking is formed on the side surface of the element, it is possible to simply write the mark with an oil-based pen.
[0044]
As shown in FIG. 5B, the crystal birefringent plate 3 configured as described above uses a main surface of the crystal birefringent plate on which the coating material 3a is formed as a main surface on the incident side and an image of a CCD or the like. It is arranged in a direction in which it is separated from the element 4, and is attached as a cover member to an opening 51 of a package 5 for accommodating, for example, a CCD.
[0045]
In the second embodiment of the present invention, the light beam separating direction is set to the right end (only one end) in the long side direction on the upper side surface 31 (one side surface of the optical low pass filter) of the incident surface of the optical low pass filter 3. Since the pointed marking M4 is formed, for example, it is specified that the optical separation direction exists in the direction of the side end 311 on which the marking M4 is formed. When it is arranged at the end, it is possible to distinguish between front and back, assuming that the main surface on the front side is the light incident surface and the main surface on which the coating material 1a is formed. Furthermore, the crystal birefringent plate 1 has a substantially square main surface. Even if the main surface is rotated by 90 ° at the center point of the main surface, the vertical direction and the horizontal direction can be distinguished.
[0046]
Note that the marking formed asymptotically with respect to the center of the side surface of the optical low-pass filter (quartz birefringent plate) is not limited to the above-described marking form, and may be the one shown in FIG.
[0047]
The crystal birefringent plate 3 in FIG. 6A is set so as to separate light rays in, for example, a 45 ° direction, and an infrared cut coat 3a is formed as a color correction filter on the light incident side main surface. On the side surface 31 above the incident surface of the crystal birefringent plate 1, a dot-shaped first marking M4 and a dot-shaped second marking indicating a light beam separation direction are provided at the center and the right end 311 in the long side direction. M5 is formed.
[0048]
Further, the crystal birefringent plate 3 in FIG. 6B is set so as to separate light rays in, for example, a 45 ° direction, and an infrared cut coat 3a is formed as a color correction filter on the light incident side main surface. . On the side surface 31 above the incident surface of the crystal birefringent plate 1, a linear first marking M4 indicating the light beam separation direction is formed at the right end 311 in the long side direction from the center.
[0049]
In this manner, one or more markings may be formed on a specific side surface, and markings that are asymmetric about the center of the side surface of the optical low-pass filter may be formed.
[0050]
Although not shown, the crystal birefringent plate 3 configured as described above is isolated from an image pickup device such as a CCD, with the main surface of the crystal birefringent plate on which the infrared cut coat material 3a is formed as the main surface on the incident side. For example, it is mounted as a cover member in an opening of a package for accommodating a CCD, and is incorporated into an imaging device such as a video camera or an electronic still camera together with a coupling optical system.
[0051]
In the embodiment of the present invention, an infrared cut filter is used as an example of the color correction filter. However, the present invention may be applied to an ultraviolet cut filter, a filter that cuts infrared rays and ultraviolet rays, and the like. In addition, the present invention is not limited to the above-described marking shapes, and various marking forms such as figures, characters, and symbols can be adopted, and these may be combined. Further, the present invention is not limited to an optical low-pass filter for an imaging device, but can be applied to a display device such as a projector or other uses. Although the present invention has been described with reference to an example in which the main surface has a substantially square shape, the present invention is also applicable to a main surface having a rectangular shape.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment.
FIG. 2 is a diagram illustrating a manufacturing method according to the first embodiment;
FIG. 3 is a perspective view of an optical low-pass filter showing a modification of the first embodiment.
FIG. 4 is a perspective view of an optical low-pass filter showing a modification of the first embodiment.
FIG. 5 is a diagram showing a second embodiment.
FIG. 6 is a perspective view of an optical low-pass filter showing a modification of the second embodiment.
[Explanation of symbols]
1, 3, 21, 23 Quartz Birefringent Plate 22 Quarter Wavelength Plate 4 Image Sensor 5 Image Sensor Package W Optical Low-Pass Filter Wafer

Claims (5)

A rectangular parallelepiped optical low-pass filter having a light beam separation direction in which light rays incident on a main surface in a main surface square shape are separated and emitted in a predetermined direction,
An optical low-pass filter, wherein one or more markings indicating a light beam separation direction are formed at one end of the main surface on the incident side or the output side symmetrically at the end with respect to the center of the main surface. As a marking formed asymmetry at the end with respect to the center of the main surface,
{Circle around (1)} marking on one of the main surfaces on the incident side or the outgoing side to indicate a light beam separation direction only near one corner of the main surface;
{Circle around (2)} a first marking, a second marking, indicating a light beam separation direction on one of the main surfaces on the incident side or the output side, near two corners adjacent to the main surface;
{Circle around (3)} a first marking, a second marking, and a third marking on one of the main surfaces on the incident side or the outgoing side, which indicate a light beam separation direction near three corners of the main surface;
2. The optical low-pass filter according to claim 1, wherein the marking described in any one of (1) to (3) is formed. A rectangular parallelepiped optical low-pass filter having a light beam separation direction in which light rays incident on a main surface in a main surface square shape are separated and emitted in a predetermined direction,
An optical low-pass filter, wherein one or more markings indicating a light beam separation direction are formed on one side surface of the optical low-pass filter so as to be asymmetric with respect to the center of the side surface. As a marking formed asymptotically with respect to the center of the side surface,
4. The optical low-pass filter according to claim 3, wherein a marking indicating a light beam separation direction is formed only on one end of one side on one side surface of the optical low-pass filter. An image pickup apparatus comprising: the optical low-pass filter according to claim 1 attached to an opening of a package in which an image pickup device is stored.
In the optical low-pass filter, a coating material is formed only on one main surface side, or a multilayer coating material is formed on one main surface side from the other main surface side. An imaging device, wherein a surface or a main surface having a multilayer coating material is attached to an opening of the package toward the outside of the package as a main surface on the incident side of the optical low-pass filter.

Images