WO2005010594A1

WO2005010594A1 - Optical filter, imager, and method for manufacturing optical filter

Info

Publication number: WO2005010594A1
Application number: PCT/JP2003/009476
Authority: WO
Inventors: Hirokazu Aritake
Original assignee: Fujitsu Limited; Fujitsu Media Devices Limited
Priority date: 2003-07-25
Filing date: 2003-07-25
Publication date: 2005-02-03
Also published as: AU2003248124A1

Abstract

An optical filter for filtering a predetermined spatial frequency component of a light wave, comprising a birefringent film (71) disposed between birefringent plates (72, 73) each for separating an incident light beam into two light beams and adapted to change the velocity of the incident light depending on the direction of the vibration of the light wave, wherein birefringent film portions (711, 712) constituting the birefringent film (71) are formed on at least one of the surfaces of the birefringent plates (72, 73), and the birefringent plates (72, 73) are so integrated into one piece that the birefringent film (71) formed on the surface and composed of the birefringent film portions (711, 712) is interposed therebetween.

Description

Description Optical filter, imaging device, and method of manufacturing optical filter

The present invention is directed to a third birefringent region in which a traveling speed changes according to a vibration direction of a light wave incident between a first birefringent region and a second birefringent region, each of which separates an incident light wave into two light waves. The present invention relates to an optical filter for filtering a predetermined spatial frequency component of the light wave, an imaging device including the optical filter, and a method for manufacturing the optical filter. The present invention relates to a high-performance optical filter that can be easily manufactured at a low cost even if it is thin, an imaging device provided with the optical filter, and a method of manufacturing the optical filter. Background art

Conventionally, in an imaging apparatus such as a digital still camera, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) power ^s for Rere et al .; Rereru Te t.

These CCDs and CMOSs are semiconductor light receiving elements that convert optical information into electrical signals. In an imaging device, a plurality of CCDs or CMs that are two-dimensionally arranged vertically and horizontally in correspondence with pixels are used as an area sensor.

In this area sensor, since each CCD or CMOS signal is spatially arranged at a predetermined pixel pitch together with a desired color filter, when an image including a high frequency component equal to or higher than the pixel pitch is captured, the moiré pattern is reduced.あった There was a problem that pseudo colors were generated.

Therefore, in order to avoid the above-mentioned problem, the conventional imaging apparatus is configured such that an optical low-pass filter is disposed in an optical system and transmits only a light component having a predetermined spatial frequency (for example, see Patent Document 1). See, 2.). FIG. 13 is a diagram showing a schematic configuration of the above-described conventional imaging apparatus. As shown in the perspective view of the imaging device in FIG. 13 (a) and the plan view in FIG. 13 (b), the optical system of the imaging device for imaging the imaging object 10 includes a lens 2. 0, an optical low-pass filter 40, and an area sensor 50.

The lens 20 is a lens that collects incident light from the imaging target 10 and guides the light to the optical low-pass filter 40. The optical low-pass filter 40 is an optical filter that transmits only a light component having a specific spatial frequency in incident light, and is made of laminated birefringent materials cut out in different directions with respect to the crystal axis.

FIG. 14 is a diagram for explaining the principle of light beam separation of the optical low-pass filter 40. As shown in the figure, the birefringent plate 1 is a crystal plate of quartz or lithium niobate (L i N b 0 ₃₎ or Ranaru thickness d, are cut at an angle Θ with respect to the crystal axis 2 It has an optical property of birefringence.

Birefringence refers to a phenomenon in which the light refracted at the boundary surface of the birefringent plate 1 becomes two instead of one. That is, when the incident light P i is incident on one end surface of the birefringent plate 1, it is separated into two polarized lights with a separation angle φ along the fast axis and the slow axis based on the refractive index ellipsoid 3, and the birefringence The ordinary light Pa and the extraordinary light Pb are emitted with a separation distance X by the other end surface of the plate 1.

FIG. 15 is a diagram showing a configuration of a conventional optical low-pass filter 40. FIG. 6A shows a case where an optical low-pass filter 40 is formed by using two birefringent plates 47 and 48.

In this case, the two birefringent plates 47 and 48 form an angle of 45 degrees between the projected optical axes when their optical axes are projected on a plane perpendicular to the traveling direction of the light wave. It is joined so that it may become. Therefore, the incident light P i is divided into four, and is detected by the respective light receiving elements 50 i to 50 _n of the area sensor 50 in a parallelogram type spatial separation pattern.

However, in this configuration, since the spatial separation pattern is asymmetric with a parallelogram type, the effect of spatial frequency filtering differs depending on the direction, and a pseudo color occurs. There was a problem that it did or did not occur.

Thus, a one-pass filter 40 is constructed by placing a quarter-wave plate between the two birefringent plates 1 so that the spatial separation pattern of the incident light Pi is square. Has been done in the past.

FIG. 15 (b) shows a case where an optical low-pass filter 40 is configured by disposing a quarter-wave plate 41 between two birefringent plates 42 and 43. In this case, the two birefringent plates 42 and 43 have an angle between the projected optical axes of 90 when the respective optical axes are projected on a plane perpendicular to the traveling direction of the light wave. Put the rooster in the right position.

Then, by disposing a quarter-wave plate 41 for converting linearly polarized light into circularly polarized light between the two birefringent plates 42 and 43, the light passes through the birefringent plate 42 and becomes two. Each of the separated incident light P i passes through the birefringent plate 43 to be further separated into two, and is applied to each light receiving element 5 1 1 _n of the area sensor 50 in a square-shaped spatial separation pattern. Each is detected.

FIG. 16 is a diagram showing the configuration of the optical low-pass filter 40 shown in FIG. 15 (b). Fig. 16 (a) shows the case where a single-pass filter 40 is constructed using quartz as the material of the birefringent plates 42 and 43. Fig. 16 (b) shows the birefringence. This is a case where an optical low-pass filter 40 is formed by using lithium niobate as the material of the plates 42 and 43.

As shown in Fig. 16 (a), the optical low-pass finoleta 40 using quartz for the birefringent plates 42 and 43 has an AR (Antireflection) coat 45. wave plate 4 1, the birefringent plate 4 3 and AR coating 4 5 ₂ are stacked.

AR coating 4 5丄and 4 5 ₂ are coated membrane suppress reflection of incident light P i. The birefringent plates 42 and 43 are quartz, which is one of the birefringent crystals, and are cut out at a predetermined angle with respect to the crystal axis. The quarter-wave plate 41 converts linearly polarized light into circularly polarized light.

Here, the birefringent plate 4 2 and the quarter-wave plate 4 1 are joined using an adhesive 4 4 Has been. Similarly, the birefringent plate 4 3 and the quarter-wave plate 4 1, are joined by an adhesive 4 4 _2.

As shown in FIG. 16 (b), the optical low-pass filter 40 using lithium niobate for the birefringent plates 42 and 43 is composed of an AR coat 45 or a birefringent plate 42 Tsuchinguko one DOO 4 6 i and 4 6 _2, quarter-wave plate 4 1, matching coat 4 6 ₃ and 4 6 _4, the birefringent plate 4 3 and AR coating 4 5 ₂ are stacked.

Matching coat 4 6 I～4 6 _4, by matching the refractive index between the birefringent plate 4 2 and 4 3 and the adhesive 4 6丄Contact and 4 6 _2, the reflection of incident light P i Suppress Coated film.

The birefringent plate 42 coated with the matching coat 46 and the quarter-wave plate 41 coated with the matching coat 46 ₂ are joined using an adhesive 44 i. I have. Similarly, the matching coat 4 6 ₃ 1 wave plate 4 quarter coated is a birefringent plate 4 3 to the matching coat 4 6 ₄ is coated is joined by an adhesive 4 4 ₂ I have.

When lithium niobate is used as the birefringent plate for separation, equivalent separation performance of incident light Pi can be obtained with a thickness of about 1/6 that of a quartz crystal (for example, see Patent Document 4). ).

FIG. 17 is a diagram showing an example of the relationship between the incident light wavelength and the transmitted light intensity in the quarter-wave plate 41. FIG. 17 (a) shows a case where the quarter-wave plate 41 is made of a crystal having a thickness of 0.5 mm. FIG. 17 (b) shows a case where the quarter-wave plate 41 is formed. 1 This is the case where the thickness is made of lithium niobate having a thickness of 0.2 mm.

Here, the intensity of the incident light P i with respect to the optical low-pass filter 40 is set to 1, and before the incident light P i is incident on the quarter-wave plate 41, the action of the birefringent plate 42 is performed. Therefore, the transmitted light intensity per transmitted light is 0.5 at the maximum.

As shown in Fig. 17 (a), in the quarter-wave plate 41, the transmitted light intensity changes depending on the wavelength, and the color tone of the captured image is different from the actual color tone. (See, for example, Patent Document 3). In order to improve this, it is necessary to further increase the thickness of the quarter-wave plate 41.

As shown in Fig. 17 (b), in the quarter-wave plate 41 made of lithium niobate, the degree of birefringence is larger than that of quartz, so that the transmitted light intensity is small when the wavelength changes slightly. Change drastically. Therefore, the wavelength dependence of the transmitted light intensity can be apparently reduced.

(Patent Document 1)

JP 10-54960

(Patent Document 2)

JP 2001-324698

(Patent Document 3)

JP 2002-303824

(Patent Document 4)

JP 11-218612

However, according to the conventional techniques represented by Patent Documents 1 to 4, when manufacturing the optical low-pass filter 40, after forming a quarter-wave plate, it is bonded to a birefringent plate with an adhesive or the like. However, there is a problem that the number of manufacturing processes increases and the manufacturing cost increases.

In particular, Patent Document 3 discloses an optical low-pass filter using a very thin quarter-wave plate having a thickness of about 10 to ⁵ m and having a small wavelength dependence of transmitted light intensity. It was very difficult to manufacture an optical filter by manufacturing a thin quarter-wave plate and joining it to a birefringent plate, which led to an increase in manufacturing costs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A high-performance optical filter that can be easily applied at the time of manufacturing and can be manufactured at a low cost even with a thin one, and an imaging device provided with the optical filter. It is an object to provide an apparatus and a method for manufacturing the optical filter. Disclosure of the invention

The present invention provides a first birefringent region for separating an incident light wave into two light waves, and a third birefringent region for converting the vibration direction of the incident light wave between the second birefringent region and the second birefringent region. An optical filter for filtering a predetermined spatial frequency component of the light wave, wherein the third birefringent region has a birefringent structure including the first birefringent region and the second birefringent region. At least one surface of the region is formed directly on the surface.

Therefore, since the birefringent structure is directly formed as the third birefringent region on at least one of the surfaces of the first birefringent region and the second birefringent region, processing at the time of manufacturing is performed. It is possible to provide a high-performance optical filter that can be manufactured easily and inexpensively even if it is thin.

Further, in the present invention, the birefringent structure may be formed in such a manner that at least one surface of the first birefringent region and the second birefringent region has a striped unevenness at an interval of a use wavelength or less. It is characterized by being realized.

Therefore, by utilizing the birefringence generated by the unevenness, it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin.

Further, the present invention is characterized in that the birefringent structure is realized by depositing an oblique deposition film on at least one surface of the first birefringent region and the second birefringent region. And

Therefore, by utilizing the birefringence of the obliquely deposited film, it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacture and can be manufactured at low cost even if it is thin.

Also, in the present invention, the birefringent structure is formed directly on the surface of any one of the first birefringent region and the second birefringent region, and the birefringent structure is formed. Table of the birefringent structure of the first birefringent region or the second birefringent region A surface and a surface of the first birefringent region or the second birefringent region where the birefringent structure is not formed are bonded by an adhesive.

Therefore, if the birefringent structure is formed on the surface of any of the birefringent regions, the surface of the birefringent structure and the surface of the first or second birefringent region should be bonded with an adhesive. Accordingly, it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin.

Further, in the present invention, the birefringent structure is formed directly on both surfaces of the first birefringent region and the second birefringent region, and the birefringent structure is formed. The surfaces of the birefringent structures of the first birefringent region and the second birefringent region are joined by an adhesive.

Therefore, when the birefringent structure is produced on the surface of both birefringent regions, the two birefringent structures are joined with an adhesive to facilitate processing at the time of production, and even a thin material. It is possible to provide a high-performance optical filter that can be manufactured at low cost.

Also, in the present invention, the birefringent structure is formed directly on the surface of any one of the first birefringent region and the second birefringent region, and the birefringent structure is formed. A surface of the birefringent structure of the first birefringent region or the second birefringent region, and a surface of the first birefringent region or the second birefringent region where the birefringent structure has not been formed. And the surface of the hydrophilized birefringent structure and the surface of the hydrophilized first birefringent region or the surface of the second birefringent region are joined together. It is characterized by becoming.

Therefore, when the birefringent structure is formed on the surface of any of the birefringent regions, the surface of the birefringent structure and the surface of the first birefringent region or the surface of the second birefringent region are subjected to a hydrophilic treatment. By bonding, it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin.

Also, in the present invention, the birefringent structure is formed directly on the surface of both the first birefringent region and the second birefringent region, The surface of the created birefringent structure and the surface of the birefringent structure created in the second birefringent region are hydrophilized and joined by superposing the two hydrophilized birefringent structures. It is characterized by the following.

Therefore, when the birefringent structures are formed on the surfaces of both birefringent regions, the surfaces of the two birefringent structures are subjected to a hydrophilic treatment and joined to facilitate processing during manufacturing, It is possible to provide a high-performance optical filter that can be manufactured inexpensively even if it is thin.

Further, in the invention, it is preferable that the birefringent structure is formed directly on the surface of the first birefringent region or the second birefringent region in a position shifted from the surface of the first birefringent region or the second birefringent region. The first birefringent region or the second birefringent region formed and the first birefringent region or the second birefringent region where the birefringent structure has not been formed are activated. It is characterized by being joined by joining.

Therefore, when the birefringent structure is formed on the surface of the birefringent region, the surface activity of the birefringent structure and the surface of the first or second birefringent region are changed. By joining by dangling, it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacture and can be manufactured at low cost even if it is thin.

Also, in the present invention, the birefringent structure is formed directly on the surface of both the first birefringent region and the second birefringent region, and the birefringent structure is formed. The first birefringent region and the second birefringent region are joined by a surface activation junction.

Therefore, when the birefringent structures are formed on the surfaces of both birefringent regions, the surfaces of the two birefringent structures are joined by surface activated bonding, so that the processing at the time of manufacturing is easy and even a thin one is used. It is possible to provide a high-performance optical filter that can be manufactured at low cost.

Further, in the present invention, the first birefringent region and the second birefringent region are made of lithium niobate.

Therefore, the first birefringent region and the second birefringent region are formed using quartz or the like. Thus, it is possible to provide a high-performance optical filter that can be formed thinner than in the case where it is manufactured, is easy to process at the time of manufacture, and can be manufactured at low cost even if it is thin.

Further, the present invention is characterized in that an infrared power filter is joined to the first birefringent region or the second birefringent region.

Therefore, it is possible to provide a high-performance optical filter that can cut infrared rays, can be easily processed at the time of manufacturing, and can be manufactured at a low cost even if it is thin. Angle formed by a first axis that projects the optical axis of the birefringent region onto a plane perpendicular to the direction of travel of the light wave, and a second axis that projects the optical axis of the second birefringent region onto the plane. Is approximately a right angle, and the axis that projects the optical axis of the third birefringent region onto the plane is (45 degrees + 111 X 9) with respect to the first axis and the second axis. (0 degree) ± 15 degrees in the angle range (m is an integer).

Therefore, it is easy to process at the time of manufacture, and even if it is thin, it can be manufactured at low cost, and it is possible to provide an optical filter having high performance without practical problems.

Further, the invention is characterized in that the third birefringent region separates the incident light wave by polarization.

Therefore, by separating the incident light wave by polarization, the optical filter can exhibit a filtering function, and can be easily processed at the time of manufacture, and even if it is thin, it is a high-performance optical filter that can be manufactured at low cost. Can be provided. Further, in the present invention, in the third birefringent region, a product of a difference between a refractive index of ordinary light and a refractive index of extraordinary light and an optical path length of the birefringent region is an odd number that is approximately one quarter of a wavelength used. It is formed so as to be twice as large and converts the polarization state of the incident light wave from linearly polarized light to substantially circularly polarized light.

Therefore, by converting the linearly polarized light of the incident light wave into a substantially circularly polarized light, the optical filter can exhibit a filtering function, and can be easily processed at the time of manufacture, and can be manufactured at a low cost even if it is thin. Providing high performance optical filters it can. '

Also, in the present invention, the third birefringent region includes a first birefringent portion and a second birefringent portion, and the optical axis of the first birefringent portion is projected on the plane. The direction and the direction of the axis obtained by projecting the optical axis of the second birefringent region portion onto the plane are substantially 180 degrees, and the second birefringent portion is formed of the first birefringent portion. The traveling direction of the separated light wave is changed by transmitting through the birefringent portion, and the separation distance between the light waves separated by the first birefringent portion is reduced.

Therefore, it is possible to suppress the separation of the light wave in the third birefringent region, and to provide a high-performance optical filter that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin. .

Further, the present invention provides an imaging lens on which a light wave is incident, an imaging device for receiving the light wave incident on the imaging lens and generating an electric signal, and disposed between the imaging lens and the imaging device; An image pickup apparatus comprising: an optical filter configured to filter a predetermined spatial frequency component of the light wave, wherein the optical filter includes a first birefringent region and a second birefringence, each of which separates an incident light wave into two light waves. A third birefringent region for converting a vibration direction of a light wave incident from the first birefringent region between the regions, wherein the third birefringent region has a birefringent structure whose birefringent structure is the first birefringent region. And at least one surface of the second birefringent region is formed directly on the surface.

Therefore, the birefringent structure is directly formed as a third birefringent region on at least one surface of the first birefringent region and the second birefringent region. It is possible to provide an imaging device having a high-performance optical filter that can be easily manufactured at a low cost even if it is thin.

Further, the present invention provides a third birefringent region for converting a vibration direction of an incident light wave between a first birefringent region and a second birefringent region for separating an incident light wave into two light waves, respectively. A light for filtering a predetermined spatial frequency component of the light wave

) Manufacturing method, wherein the third birefringent region is replaced with the first birefringent region And forming a birefringent structure directly on at least one surface of the second birefringent region.

Therefore, on at least one of the first birefringent region and the second birefringent region, a birefringent structure is directly formed as a third birefringent region on the surface, which facilitates processing during manufacturing. It is possible to manufacture even a thin optical filter at low cost. Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of an optical low-pass filter 70 according to the present invention, and FIG. 2 is a diagram specifically explaining the function of the optical low-pass filter 70 described in FIG. Figure 3 is a view showing a deposition method for depositing a birefringent plate 7 2 to the first birefringent film portion 71 and the second birefringent film portion 7 1 _2, Fig. 4, FIG. 1 FIG. 5 is a diagram showing an example of the relationship between the wavelength of a light wave and the intensity of transmitted light in the birefringent film 71 shown in FIG. 5, and FIG. FIG. 6 is a diagram for explaining a method of integrating the plates 73, FIG. 6 is a diagram showing a structure of a birefringent plate 75 according to the second embodiment, and FIG. 7 is a diagram shown in FIG. and is a diagram showing an example of a relationship between the wavelength and the transmitted light intensity at the birefringent structure, FIG. 8 is one birefringent plate 7 5 i or birefringent plate 7 5 ₂ having birefringence structure on the surface FIG. 9 is a diagram illustrating the function of an optical low-pass filter 70 according to the third embodiment. FIG. 10 is a diagram illustrating a birefringent film on a birefringent plate 72. FIG. 11 is a view for explaining a vapor deposition method for vapor-depositing 76. FIG. 11 is a diagram showing an example of joining or bonding a birefringent film 76 processed on the surface of a birefringent plate 72 and a birefringent plate 73. FIG. 12 is a diagram for explaining the Eich method, FIG. 12 is a diagram showing a configuration of an imaging device 200 having the optical low-pass filter described in Embodiment 1, 2, or 3, and FIG. FIG. 14 is a diagram illustrating a schematic configuration of a conventional imaging device. FIG. 14 is a diagram illustrating the principle of light beam separation of the optical low-pass filter 40. FIG. 15 is a diagram illustrating the conventional optical low-pass filter 40. FIG. 16 is a diagram showing a configuration of the optical low-pass filter 40 shown in FIG. 15 (b), and FIG. Is 4 minutes FIG. 4 is a diagram showing an example of the relationship between the incident light wavelength and the transmitted light intensity in the one-wavelength plate 41 of FIG. BEST MODE FOR CARRYING OUT THE INVENTION

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the accompanying drawings, preferred embodiments of an optical filter according to the present invention, an imaging device provided with the optical filter, and a method of manufacturing the optical filter will be described in detail below. FIG. 2 is a diagram showing a configuration of such an optical low-pass filter 70. This optical low-pass filter 70 is used in place of the optical low-pass filter 40 shown in FIG.

As shown in FIG. 1 (a), this optical low-pass filter 70 has A R (

Antireflection) Coat 7 4 birefringent plate 7 2 (first birefringent region), birefringent film 7 1 (third birefringent region), birefringent plate 7 3 (second birefringent region) and AR coating G 7 4 ₂ are laminated.

AR coating 7 and 7 4 ₂ is a coated membrane suppress reflection of incident light P i. The birefringent plates 72 and 73 are quartz, which is one of the birefringent crystals, and are cut out at a predetermined angle with respect to the crystal axis.

Here, the birefringent plates 72 and 73 are formed from quartz, but the birefringent plates 72 and 73 may be formed using lithium niobate. By using lithium niobate, the optical low-pass filter 70 can be realized even thinner than in the case of quartz.

The birefringent plates 72 and 73 are designed such that when the respective optical axes are projected on a plane perpendicular to the traveling direction of the light wave, the angle between the projected optical axes is 90 degrees. Placed in

The principle of light separation of the birefringent plates 72 and 73 is the same as that described with reference to FIG. In FIG. 13, between the cutout angle 0 of the birefringent plate 1 with respect to the crystal axis 2 and the separation angle φ between the ordinary light Pa and the extraordinary light P,

Holds. Where n. Is the refractive index for the ordinary light P a, n _e is the refractive index for the extraordinary light P b.

Furthermore, between the separation angle φ and the thickness (optical path length) d of the birefringent plate 1 and the separation distance X between the ordinary light Pa and the extraordinary light Pb, tan ^ = — (2)

d

Holds.

Therefore, the separation distance X is determined so as to conform to the distance between the light receiving elements in the area sensor 50, and the thickness d and the cutout angle Θ satisfy the relational expressions of the expressions (1) and (2). Thus, the optical low-pass filter 40 having a desired function can be manufactured. ,

When it is desired to manufacture the optical low-pass filter 70 at low cost, a commercially available birefringent plate 1 having a cutout angle 0 of 38 degrees or 26 degrees may be used, but is not limited to this. Instead, the birefringent plate 1 satisfying the expressions (1) and (2) and having various cutting angles Θ can be used.

The birefringent film 71 is a thin layer having a function of converting linearly polarized light of a light wave transmitted through the birefringent plate 72 into circularly polarized light and transmitting the birefringent plate 73. The birefringent film 71 is formed by depositing a metal oxide on at least one surface of the birefringent plate 72 or the birefringent plate 73 using an oblique evaporation method.

The oblique deposition method is a method of forming a birefringent deposited film by depositing a metal oxide on a substrate in an oblique direction. (Reference: Motohiro, T. and Taga, Y .: APPLIED OPTICS , Vol. 28, No. 13, 1 July 1989, pp2466).

When the birefringent plate 7 2 or 7 3 are formed in the crystal is chosen as the metal oxide depositing dioxide Kei element (S i 0 _2). This is achieved by using a metal oxide having a refractive index similar to that of the birefringent plates 72 and 73. This is for suppressing the reflection of the light wave at the interface.

When the birefringent plate 7 2 or 7 3 are formed by lithium niobate, for the same reason, - Gosani匕tantalum having O Bed lithium and similar refractive index (T a ₂ o ₅₎ Is selected as the metal oxide to be deposited.

As shown in FIG. 1 (b), in the optical low-pass filter 70 having the birefringent film 71, the optical axis of the birefringent plate 72 is projected in the direction of the axis projected onto a plane perpendicular to the traveling direction of the light wave. is an X-direction 6 i, the direction of the axis projected in the plane perpendicular to the traveling direction of the light wave to the optical axis of the birefringent plate 7 3 is the y direction 6 _2. The birefringent film 71 has a function of converting linearly polarized light of the light wave transmitted through the birefringent plate 72 into circularly polarized light.

Each of the incident light P i transmitted through the birefringent plate 72 and separated by the birefringent plate 73 is further separated by the birefringent plate 73, and each light receiving element 5 of the area sensor 50 has a square spatial separation pattern. Detected at 1 i to 5 l _n respectively.

As described above, since the birefringent film 71 is directly formed by depositing a metal oxide on at least one surface of the birefringent plate 72 or the birefringent plate 73, even an extremely thin birefringent film 71 can be easily formed. The optical low-pass filter 70 can be manufactured at low cost.

FIG. 2 is a diagram specifically illustrating the function of the light port one-pass filter 70 described in FIG. As shown in FIG. 2 (a), this optical low-pass filter 70 has a birefringent plate 72 on which a birefringent film 71 is deposited and a birefringent plate 71 on which a birefringent film 71 is deposited. The birefringent plate 73 is joined.

Further birefringent film 71 is composed of a first birefringent film portion 71 i and the second birefringent film portion 7 1 _2. The first birefringent film portion 71 second birefringent film portion 7 1 ₂ is equal thickness d / 2, each having a function as a wave plate 8 minutes, two are combine In this way, it is configured to function as a quarter-wave plate.

That is, the first birefringent film portion 7 1 i (' ^-n .)' = ^m ^ (3) A film is formed with a thickness that satisfies the relational expression, and a film that functions as an eighth wavelength plate is formed. Where _ne and n. Is the refractive index of the extraordinary light and ordinary light in the first birefringent film portion 7 1, m is an odd integer, and L is the wavelength used for the light wave (for example, 3 8 0 to 780 nm, etc.).

Also, the thickness of the second birefringent film portion 7 1 ₂ satisfies the expression (3).

. That is, _ne and n. Is the second birefringence J3, the refractive index of the extraordinary light and the ordinary light in the portion 71, m is an odd integer, and λ is the wavelength used for the light wave, the thickness satisfying the formula (3) I do.

By Rukoto to laminate the first birefringent film portion 7 1 i and the second birefringent film portion 7 1 _2, _lambda

( _ne −n ₀ ) −d = m− (4) is satisfied, and the birefringent film 71 functioning as a quarter-wave plate can be formed.

When laminating the first birefringent film portion 7 1 i and the second birefringent film portion 7 1 ₂ , when the respective optical axes are projected on a plane perpendicular to the _Z axis, Are deposited so that the angle between them becomes 180 degrees. This is to prevent the birefringent film 71 itself from separating a light wave into two, and to have only a function of converting linearly polarized light into circularly polarized light.

Here, it is assumed that depositing a first birefringent film portion 71 of the second and birefringent film portion 7 1 ₂ birefringent plate 7 2, the first birefringent film portion 7 1 i Alternatively, the second birefringent film portion 7 1 and ₂ may be deposited on the birefringent plate 73.

Further, the first birefringent film portion 7 1 ₁ was deposited on the birefringent plate 7 2, and the second birefringent film portion 7 1 ₂ was deposited on the birefringent plate 7 3. The birefringent plate 72 and the birefringent plate 73 may be joined.

In Equation (4), if the value of the odd integer m is small, such as 1, the thickness is d is a very small value. When the thickness of the birefringent film 71 is extremely small as described above, it is extremely difficult to separately form the birefringent film 71 and bond it to the birefringent plate 72, etc. By using the oblique deposition method, a birefringent film 71 having such a thickness can be easily formed.

Figure 3 is a view showing a deposition method for depositing a birefringent plate 7 2 to the first birefringent film portion 71 i and the second birefringent film unit content of 7 1 _2. Here, it is assumed that the _Z direction coincides with the traveling direction of the light wave.

As shown in the figure, first, a first birefringent film portion 71 is vapor-deposited on the surface of the birefringent plate 72, and then a second birefringent film portion 71 is deposited on the surface of the deposited birefringent film portion 71. The birefringent film portion 7 1 ₂ is deposited.

Specifically, when the first birefringent film portion 71 is deposited, the irradiation direction of the metal oxide forms an angle of about 670 ° with the z-axis direction, and the birefringent plate 7 Optical axis direction 2 and the direction in which the irradiation direction of the metal oxide is 45 degrees when projected on a plane perpendicular to the z-axis (irradiation source 1) Is irradiated.

Then, when depositing the _second birefringent film portion 71, the metal oxide is irradiated from the opposite direction (irradiation source 2) to the case where the first birefringent film portion 71 is deposited. That is, the irradiation direction of the metal oxide is opposite to the direction in which the first birefringent film portion 7 is deposited, and forms an angle of about 600 ° with the z-axis direction. When the optical axis direction 2 of 2 and the irradiation direction of the metal oxide are projected on a plane perpendicular to the z-axis, the metal oxide is irradiated from a direction having an angle of 45 degrees.

Accordingly, when the respective optical axes of the first birefringent film portion 7 1 i and the second birefringent film portion 7 1 ₂ are projected on a plane perpendicular to the z axis, since the angle a 1 8 0 degrees, varying by the traveling direction of the light wave separated by passing through the first birefringent film portion 71 is transmitted through the second birefringent film portion 7 1 ₂ Then, the separated light waves are integrated again.

Returning to the explanation of FIG. 2, as shown in FIG. 2 (b), the light wave transmitted through the birefringent plate 72 and separated into two is transmitted by the birefringent film 71, Vibration direction condition The light is converted from linearly polarized light to circularly polarized light, passes through the birefringent plate 73, and is separated into four light waves in a square shape.

FIG. 4 is a diagram showing an example of the relationship between the wavelength of a light wave and the intensity of transmitted light in the birefringent film 71 shown in FIG. Here, the intensity of the incident light P i is set to 1, and the incident light P i is separated into two before entering the birefringent film 71, so that the transmitted light intensity is 0.5 at the maximum. . Further, this example shows a case where the value of m is set to 1 in the equation (4), that is, a case where the birefringent film 71 is formed very thin.

As shown in the figure, by forming the birefringent film 71 very thin while satisfying the expression (4), it is possible to reduce the fluctuation of the transmitted light intensity of the light wave transmitted through the birefringent film 71. Therefore, a high-performance optical low-pass filter with low manufacturing cost can be realized.

FIG. 5 is a view for explaining a method of integrating the birefringent plate 72 or the birefringent plate 73 with the birefringent film 71 processed on the surface. FIG. 5 (a) shows that the first birefringent portion 7 1 i and the second birefringent film portion 7 1 ₂ are continuously deposited on the birefringent plate 7 2, and then the adhesive 4 4 This is a method of bonding a birefringent plate 72 and a birefringent plate 73 on which a vapor deposition process has been performed by using the method.

Here, “adhesion” means a state in which two surfaces are bonded by using an adhesive as a medium, and more specifically, by using an adhesive as a medium and by using chemical or physical force or both. This is the state where the surfaces are connected. The term “joining” refers to a state in which two surfaces are joined without using an adhesive, and more specifically, a state in which two surfaces are joined by physical force without using an adhesive. That is.

The term “integrated” means that each of the birefringent plates 72 or 73 or, if necessary, an infrared cut filter or the like is formed as one member by bonding or joining. The infrared cut filter refers to a filter having a function of reflecting infrared light, a function of absorbing infrared light, or a function of both.

Figure 5 (b), the first being birefringent film portion 7 1 S deposited on the birefringent plate 7 2, also, the second birefringent film portion 7 1 ₂ is deposited on the birefringent plate 7 3, then The glue 4 4 Used, the birefringent plate 7 2 first birefringent film portion 71 E is deposited is a method in which the second birefringent film portion 7 1 ₂ to bond the birefringent plate 7 3 deposited .

Fig. 5 (c) shows that the first birefringent film portion 71 and the second birefringent film portion 71 ₂ are successively deposited on the birefringent plate 72, and then directly bonded or room temperature bonded. Thus, the birefringent plate 7 having been subjected to the vapor deposition process and the birefringent plate 73 are joined. The direct bonding performs hydrophilic treatment of the second birefringent film portion 7 1 ₂ Oyopi birefringent plate 7 3 of the surface as a bonding surface, a second birefringent film portion 7 1 ₂ and the birefringent plate This is a method in which the two are joined by performing heat treatment after occupying 73 with the shellfish.

The room-temperature bonding, a second birefringent film portion 7 1 ₂ and the surface of the birefringent plate 7 3 serving as a bonding surface, the surface chestnut and one Jung a beam of inert gas such as argon and irradiated at room temperature, This is a method of joining both by overlapping in a vacuum. This method is also called surface active junction.

FIG. 5 (d) shows that the first birefringent film portion 71 S is vapor-deposited on the birefringent plate 72, and the second birefringent film portion 71 ₂ is vapor-deposited on the birefringent plate 73. The first birefringent film part 7 1! This is a method in which the birefringent plate 72 on which the second birefringent film portion 71 is deposited and the birefringent plate 73 on which the _second birefringent film portion 72 is deposited are joined. An infrared cut filter for energizing infrared rays may be further joined or bonded to the optical low-pass filter 70 thus formed. Since CCDs and CM〇Ss sense infrared light, the generation of noise due to infrared light can be suppressed by joining an infrared cut filter. The infrared power filter is formed of a substrate such as an infrared absorbing glass or an infrared reflective coat of a multilayer film. As described above, in the first embodiment, the birefringent plate 72 or the birefringent plate 73 is used. At least one surface was processed by oblique deposition to form a birefringent film 71 that converts the vibration state of the light wave transmitted through the birefringent plate 72 from linearly polarized light to circularly polarized light. It is possible to provide a high-performance optical low-pass filter 70 that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin. (Embodiment 2)

By the way, in the first embodiment, the birefringent film having the same function as the quarter-wave plate is formed by the oblique vapor deposition method. Instead of using the oblique vapor deposition method, the first birefringent plate is used. In addition, irregularities may be formed on at least one surface of the second birefringent plate to provide a birefringent structure having a function equivalent to that of a quarter-wave plate. Therefore, in Embodiment 2, a case will be described in which a birefringent structure is provided by forming irregularities on at least one surface of the first birefringent plate and the second birefringent plate.

FIG. 6 is a diagram showing a structure of a birefringent plate 75 according to the second embodiment. As shown in the same figure (a), this birefringent plate 75 has its surface processed to form irregularities, and the concave and convex forms a birefringent structure having the same function as a quarter-wave plate. ing.

Specifically, by photolithography, irregularities are formed on the surface of the birefringent plate 75 in the form of stripes at intervals smaller than the wavelength used. At this time, the direction along the irregular stripes and the direction of the optical axis 2 of the birefringent plate 75 should be at an angle of 45 degrees when projected on a plane perpendicular to the traveling direction of the light wave. .

As a result, the direction of the optical axis of the birefringent structure formed on the surface of the birefringent plate 75 and the direction of the optical axis 2 of the birefringent plate 75 are determined when projected onto a plane perpendicular to the traveling direction of the light wave. The angle is 45 degrees.

By processing the surface of the birefringent plate 75 in this way, structural birefringence, which becomes the refractive index ellipsoid 3 as shown in FIG. 6 (b), is generated and formed on the surface of the birefringent plate 75. The birefringent structure can exhibit the same function as a quarter-wave plate.

For example, in the example of FIG. 6 (c), the birefringent plate 75 is made of lithium niobate, the thickness of the body of the birefringent plate 75 is 0.27 μm, and the width of the concave portion is ◦. μm. The height of the convex portion formed on the surface of the birefringent plate 75 is d, and the total width of the concave portion and the convex portion is e.

In principle, the refractive index n _e and extraordinary And the refractive index n of ordinary light. The difference 11 _e — n. Is determined by the ratio of the width of the recess to e (in this case, 0.066 / e). And the refractive index difference n _e — n. And the height d of the convex part is 4

By setting the height to satisfy the above, a birefringent structure having a function equivalent to that of a quarter-wave plate can be formed. Here, λ is the use wavelength of the light wave, and m is an odd integer.

In Equation (5), when the value of the odd integer m is small, such as 1, the thickness d is a very small value. When the thickness of the birefringent structure is extremely small as described above, it is extremely difficult to separately form the birefringent structure and bond it to the birefringent plate as in the past. If used, a birefringent structure having such a thickness can be easily formed.

FIG. 7 is a diagram showing an example of the relationship between the wavelength of a light wave and the intensity of transmitted light in the birefringent structure shown in FIG. Here, the intensity of the incident light P i is set to 1, and the incident light P i is split into two before entering the birefringent structure, so that the transmitted light intensity becomes 0.5 at the maximum. Also, this example shows a case where the value of m in Equation (5) is 1, that is, a case where the birefringent structure is formed very thin.

As shown in the figure, by forming the birefringent structure to be very thin while satisfying the expression (5), it is possible to reduce the fluctuation of the transmitted light intensity of the light wave transmitted through the birefringent structure. A low-cost, high-performance optical aperture one-pass filter can be realized.

8 is a diagram illustrating an integrated method of the birefringent plate 7 5 i or birefringent plate 7 5 ₂ having birefringence structure on the surface. FIG. 8 (a) shows a birefringent structure in which a birefringent structure having the function of a quarter-wave plate is formed on a birefringent plate 75, and then the birefringent structure is formed using an adhesive 44. This is a method of bonding the refraction plate 75 and the birefringence plate 73.

FIG. 8 (b) shows that the first birefringent structure is formed on the birefringent plate 75e. The second form birefringence structure to the plate 7 5 _2, then, by using an adhesive agent 4 4 by bonding a birefringent plate 7 5 i and the birefringent plate 7 5 _2, quarter wavelength This is a method of forming a birefringent structure having the function of a plate. However, the irregularities are formed such that the directions of the stripes of the irregularities of the first birefringent structure and the second birefringent structure match.

The convex portion of the first birefringent structure and the convex portion of the second birefringent structure are formed so as to exhibit the function of a quarter-wave plate by joining them. Specifically, when the sum of the heights of the projections of both is d, the surface is processed so as to have a total height d that satisfies Equation (5). Thus, a birefringent structure having the following function can be formed.

FIG. 8 (b) shows a case where the height of the convex portion of the first birefringent structure is equal to the height of the convex portion of the second birefringent structure. Should be such that satisfies equation (5). The case where the heights of the two birefringent structures are equal means that each birefringent structure has the function of a 1/8 wave plate. Fig. 8 (c) shows that the birefringent plates 75 A birefringent structure having the function of a single-wavelength plate is formed, and then the birefringent plate 75 with the birefringent structure formed thereon and the birefringent plate 73 by direct bonding or room-temperature bonding. is there.

Figure 8 (d) is to form a first birefringent structure birefringent plate 7 5 E, also forming a second birefringent structure birefringent plate 7 5 _2, then direct bonding or cold by joining, joining the birefringent plate 7 5 and the birefringent plate 7 5 _2, it is a method of forming a birefringent structure having the function of a quarter wave plate.

The optical low-pass filter 70 thus formed may be further joined with an infrared cut filter for applying infrared light, and may be bonded to reduce noise due to infrared light. .

The optical axis of the birefringent structure formed on the first birefringent plate 7 5 and the second surface of the birefringent plate 7 5 _2, Les such become parallel to the traveling direction of the light wave, the case, carried As described in Embodiment 1, the light wave is split into two in the birefringent structure. To suppress them, when the direction of the first birefringent plate 7 5 and the second birefringent plate 7 5 ₂ optical axis is projected on a plane perpendicular to the traveling direction of the light wave, the two optical axes combining the first birefringent plate 7 5 i and the second Fuku屈folded plate 7 5 ₂ such as the angle of the direction is 1 8 0 degrees, Yo Le is also possible to form an optical low-pass filter 7 0, ₀

As described above, in the second embodiment, the irregularities formed by processing the first birefringent plate 7 5 i or second at least one surface of the birefringent plate 7 5 _2, a quarter Since a birefringent structure having the same function as that of the wavelength plate is formed, high-performance light that can be easily processed at the time of manufacture and can be manufactured at low cost even in the case of the thin film as in the first embodiment. A low-pass filter 70 can be provided.

(Embodiment 3)

By the way, in the first or second embodiment, at least one surface of the first birefringent plate or the second birefringent bending plate is processed to have a function equivalent to that of a quarter-wave plate. A region was formed, and the direction of vibration of the incident light wave was converted from linearly polarized light to circularly polarized light or elliptically polarized light.However, the birefringence region was configured so that the incident light wave was separated by polarized light. I'm sorry.

Therefore, in Embodiment 3, a case will be described in which a birefringent region between the first birefringent plate and the second birefringent plate is formed so as to convert the angle of linearly polarized light of an incident light wave.

FIG. 9 is a diagram for explaining the function of the optical low-pass filter 70 according to the third embodiment. As shown in FIG. 9 (a), this optical low-pass filter 70 has a birefringent film 72 deposited on a birefringent plate 72, and a birefringent plate 72 on which a birefringent film 76 is deposited. The bending plate 73 is joined. Here, the birefringent film 76 is deposited on the birefringent plate 72, but the birefringent film 76 may be deposited on the birefringent plate 73.

When depositing the birefringent film 76, when the optical axis of the birefringent film 76 and the optical axis of the birefringent plate 72 are projected into a plane perpendicular to the traveling direction of the light wave, 45 ° Make an angle. By depositing the birefringent film 76 in this way, as shown in FIG. 9 (b), the light wave transmitted through the birefringent plate 72 and separated into two is transmitted through the birefringent film 76. Then, the vibration direction is rotated by 45 degrees, and the light is incident on the birefringent plate 73 whose optical axis direction differs from the birefringent plate 72 by 90 degrees.

Metal Sani匕物to be deposited, when the birefringent plate 7 2 or 7 3 are formed in the crystal, the silicon (S i 0 ₂₎ dioxide ίΚ birefringent plate 7 2 or 7 3 niobate lithium in the case of being formed, tantalum pentoxide (T a ₂ 0 ₅₎ is selected. This is because the use of metal oxides having a refractive index similar to that of the birefringent plates 72 and 73 suppresses the reflection of light waves at the interface between them. However, when the light wave passes through the birefringent film 76, each light wave separated into two by the birefringent plate 72 is further separated into two. Then, each light wave is further separated into two by the birefringent plate 73, and one incident light Pi is separated into a total of eight light waves.

By forming the birefringent film 76 as a thin film, the separation distance of the light waves in the birefringent film 76 can be reduced, and the square shown in FIG. A 4-point separation pattern of the mold can be obtained. The thin birefringent film 76 can be easily realized by using an oblique evaporation method.

FIG. 10 is a view for explaining a vapor deposition method for vapor-depositing a birefringent film 76 on a birefringent plate 72. Here, it is assumed that the z direction coincides with the traveling direction of the light wave. As shown in the figure, when depositing the birefringent film 76 on the birefringent plate 72, the irradiation direction of the metal oxide forms an angle of about 60 to 70 degrees with the _Z- axis direction, and The direction in which the optical axis direction 2 of the birefringent plate 72 and the irradiation direction of the metal oxide are projected at an angle of 45 degrees when projected on a plane perpendicular to the _Z axis (irradiation source) Irradiate the dagger.

Thereby, the birefringent film 76 can rotate the vibration direction of the light wave 72 incident on the birefringent plate 72 by 45 degrees, and the optical low-pass filter 70 described in FIG. Can be realized.

FIG. 11 shows a birefringent film 76 and a birefringent plate 73 formed on the surface of a birefringent plate 72. FIG. 4 is a view for explaining a method of joining or adhering the two. FIG. 11 (a) shows a birefringent film 72 deposited on a birefringent plate 72, and then a birefringent plate 72 with a birefringent film 76 deposited thereon using an adhesive 44. This is a method of bonding the refraction plate 73.

Fig. 11 (b) shows a birefringent film 72 deposited on a birefringent plate 72, and then birefringent with a birefringent plate 72 on which the birefringent film 76 is deposited by direct bonding or room temperature bonding. This is a method of joining the plate 73.

An infrared cut filter for cutting infrared rays may be further joined or adhered to the optical low-pass filter 70 formed in this way so as to reduce noise due to infrared rays.

As described above, in the third embodiment, the birefringent film 76 having a function of separating the light wave transmitted through the birefringent plate 72 in the direction of 45 degrees is formed by the birefringent plate 7 by an oblique evaporation method. Since it is formed directly on the birefringent plate 73 or the birefringent plate 73, it is possible to provide a high-performance optical low-pass filter 70 that can be easily processed at the time of manufacturing and can be manufactured at low cost even if it is thin.

In the third embodiment, the birefringent film 76 having a function of separating the light wave transmitted through the birefringent plate 72 in the direction of 45 degrees is formed by an oblique deposition method. However, it is also possible to form the birefringent structure having irregularities as shown in the second embodiment on a birefringent plate using one photolithography technique to realize the same function. Also in this case, the thickness of the birefringent film 76 can be easily reduced.

(Embodiment 4)

By the way, in the first, second or third embodiment, the optical low-pass filter for directly processing the surface of the birefringent plate to change the polarization state of the incident light wave has been described. An imaging device can be configured using a CCD, a CMOS, or a CMOS area sensor.

Therefore, in the fourth embodiment, an imaging device configured using the optical low-pass filter described in the first, second, or third embodiment, a lens, an area sensor, and the like is described. Will be explained.

FIG. 12 is a diagram illustrating a configuration of an imaging device 200 having the light-port one-pass filter described in Embodiment 1, 2, or 3. As shown in the figure, the image pickup apparatus 2 0 0 have area sensor 5 0, the optical low-pass filter 7 0, lens 8 0, an IR cut filter 9 0, the force per 1 0 0 i and 1 0 0 ₂ .

The area sensor 50 is a sensor in which a plurality of CCDs or CMOSs are two-dimensionally arranged vertically and horizontally in correspondence with the pixels, and the optical aperture one-pass filter 70 is provided by any one of the first to third embodiments. This is the optical low-pass filter described above.

The lens 80 is a lens that collects incident light from the imaging target and guides the light to the optical low-pass filter 70, and the infrared cut filter 90 is a filter for filtering infrared light.

Cover 1 0 0 and 1 0 0 ₂ lens 8 0, the optical low-pass filter 7 0, a cover for supporting the infrared Katsuhito filter 9 0 and the area sensor 5 0, cover l OO i and 1 0 0 ₂ A It is adhered and fixed by the adhesive 110.

Here, Rukoto using other methods such as the cover 1 0 0 and the 1 0 0 _2, it is assumed that bonding by the adhesive 1 1 0, without the use of adhesives 1 1 0, fixed with nails You can do it.

As described above, in the fourth embodiment, the imaging device 200 having the lens 80 and the area sensor 50 is configured using the optical low-pass filter described in the first, second, or third embodiment. Therefore, by incorporating a high-performance optical low-pass filter 70 that is easy to process at the time of manufacturing and can be manufactured at low cost even if it is thin, an imaging device with low manufacturing cost can be provided.

In the first to fourth embodiments, quartz or lithium ebobate is used as the material of the birefringent plate. However, the present invention is not limited to this, and various other birefringences may be used. The materials shown can be used. In this case, the embodiment

In 1 or 3, the metal oxide deposited on the birefringent plate can be appropriately selected according to the material of the birefringent plate. In the first to fourth embodiments, the optical axis direction of the birefringent region formed on the surface of the birefringent plate and the direction of the optical axis of the birefringent plate are projected on a plane perpendicular to the traveling direction of the light wave. In this case, the birefringent region is formed so as to have an angle of 45 degrees. However, the present invention is not limited to this, and the angle between the two optical axes is 45 degrees ± 1. It may be within the range of 5 degrees. This is because within this range, the difference between the transmitted light intensities of the two light waves transmitted through the formed birefringent region is small, and does not pose a problem in practical use.

Further, in Embodiments 1 to 4, various values and shapes such as angles and dimensions are shown, but in practice the values and shapes are not strict, and each part of the optical filter is There is a possibility that an error may occur due to a problem of accuracy in manufacturing the device. (Effect of the present invention)

As described above, the first birefringent region, which separates the incident light wave into two light waves, and the third birefringent region, which converts the vibration direction of the light wave incident between the second birefringent region and the second birefringent region. An optical filter for filtering a predetermined spatial frequency component of a light wave, wherein the third birefringent region has at least one of a first birefringent region and a second birefringent region. Since one surface is formed directly on the surface, there is an effect that it is possible to provide a high-performance optical filter that can be easily processed at the time of manufacturing and that can be manufactured at a low cost even if it is thin. Further, according to the present invention, an imaging lens into which a light wave is incident, an imaging element that receives the light wave incident on the imaging lens to generate an electric signal, and is disposed between the imaging lens and the imaging element, An imaging device comprising an optical filter for filtering a predetermined spatial frequency component of a light wave, wherein the optical filter includes a first birefringent region and a second birefringent region for separating an incident light wave into two light waves, respectively. A third birefringent region for converting a vibration direction of a light wave incident from the first birefringent region between the first birefringent region and the second birefringent region. Since at least one of the refraction areas is formed directly on the surface, the This makes it possible to provide an imaging device provided with a high-performance optical filter that can be easily manufactured and that can be manufactured at a low cost even if it is thin.

Further, according to the present invention, the third birefringent region for converting the vibration direction of the light wave incident between the first birefringent region and the second birefringent region for separating the incident light wave into two light waves, respectively. A method of manufacturing an optical filter, comprising: a first birefringent region; and a second birefringent region, wherein the third birefringent region is provided with a first birefringent region and a second birefringent region. Since the birefringent structure is formed directly on at least one of the surfaces, it is possible to easily perform processing at the time of manufacturing, and it is possible to manufacture even a thin optical filter at low cost. Play. Industrial applicability

As described above, the method of manufacturing an optical filter, an imaging device, and an optical filter according to the present invention is attached to a digital still camera, a camera for a mobile phone, or the like for the purpose of suppressing generation of false colors. The present invention is suitable for an optical filter, an imaging device using the optical filter, and a method of manufacturing the optical filter.

Claims

The scope of the claims

1. Between the first birefringent region and the second birefringent region that separate the incident light wave into two light waves, a third birefringent region having a different traveling speed depending on the vibration direction of the incident light wave is provided. An optical filter / filter that filters a predetermined spatial frequency component of the light wave,

The third birefringent region, wherein a birefringent structure is formed on at least one surface of the first birefringent region and the second birefringent region on the surface.

2. The birefringent structure is characterized in that at least one surface of the first birefringent region and the second birefringent region has irregularities formed in stripes at intervals equal to or less than the wavelength used. The optical filter according to claim 1, wherein

3. The birefringent structure, wherein an obliquely deposited film is deposited on at least one surface of the first birefringent region and the second birefringent region. An optical filter according to the item.

4. The birefringent structure is formed on the surface of either the first birefringent region or the second birefringent region, and the first birefringent region where the birefringent structure is formed Alternatively, the surface of the birefringent structure of the second birefringent region and the surface of the first birefringent region or the surface of the second birefringent region where the birefringent structure is not formed are bonded with an adhesive. 2. The optical filter according to claim 1, wherein the optical filter is integrated.

5. The birefringent structure includes a first birefringent region and a second birefringent region. The surfaces of the birefringent structures of the first birefringent region and the second birefringent region formed on the surfaces on both surfaces and having the birefringent structure formed thereon are integrated by an adhesive. The light according to claim 1, characterized in that:

6. The birefringent structure is formed on the surface of the first birefringent region or the second birefringent region, which is different from the surface of the second birefringent region. A surface of the birefringent structure of the first birefringent region or the second birefringent region; and a surface of the first birefringent region or the second birefringent region where the birefringent structure is not formed. Are bonded by superposing the surface of the birefringent structure that has been hydrophilized and the surface of the first birefringent region or the second birefringent region that has been hydrophilized. Light according to claim 1, characterized by:

7. The birefringent structure is formed on both surfaces of the first birefringent region and the second birefringent region, and the birefringent structure formed in the first birefringent region. And the surface of the birefringent structure formed in the second birefringent region is hydrophilized, and the two birefringent structures that have been hydrophilized are joined by overlapping. Light as described in range 1:

8. The birefringent structure is formed on the surface of either the first birefringent region or the second birefringent region, and the first birefringent region on which the birefringent structure is formed. Alternatively, the second birefringent region and the first birefringent region or the second birefringent region where the birefringent structure is not formed are joined by a surface activation junction. The optical filter according to claim 1, wherein

9. The birefringent structure is formed on both surfaces of the first birefringent region and the second birefringent region, and the first birefringent on which the birefringent structure is formed. The region and the second birefringent region are joined by a surface activated junction. 2. The optical filter according to claim 1, wherein:

10. The optical filter according to claim 1, wherein the first birefringent region and the second birefringent region are made of lithium niobate.

11. The optical filter according to claim 1, wherein an infrared power filter is formed or integrated in the first birefringent region or the second birefringent region.

1 2. A first axis that projects the optical axis of the first birefringent region onto a plane perpendicular to the traveling direction of the light wave, and a second axis that projects the optical axis of the second birefringent region onto the plane. The angle formed by the second axis is substantially a right angle, and the axis obtained by projecting the optical axis of the third birefringent region onto the plane is (45 degrees) with respect to the first axis and the second axis. The optical filter according to any one of claims 1 to 11, wherein the optical filter forms an angle within a range of (+11190 degrees) ± 15 degrees (m is an integer).

13. The light according to claim 12, wherein the third birefringent region spatially separates an incident light wave by polarization.

1 4. In the third birefringent region, the product of the difference between the refractive index of ordinary light and the refractive index of extraordinary light and the optical path length of the birefringent region is an odd multiple of approximately one quarter of the wavelength used. 13. The optical filter according to claim 12, wherein the optical filter is formed as described above, and converts a polarization state of the incident light wave from linearly polarized light to substantially circularly polarized light.

15. The third birefringent region includes a first birefringent portion and a second birefringent portion, and a direction of an axis that projects an optical axis of the first birefringent portion onto the plane, The direction of the axis obtained by projecting the optical axis of the second birefringent region onto the plane is approximately 180 degrees. The second birefringent portion changes the traveling direction of the light wave separated by transmitting through the first birefringent portion, and the light wave separated by the first birefringent portion. 15. The optical finoleter according to claim 14, wherein a separation distance between the optical fins is reduced.

16. An imaging lens into which a light wave is incident, an imaging device that receives the light wave incident on the imaging lens and generates an electric signal, and is disposed between the imaging lens and the imaging device. An imaging apparatus comprising an optical filter for filtering predetermined predetermined spatial frequency components,

The optical filter travels between a first birefringent region and a second birefringent region, each of which separates an incident light wave into two light waves, according to a vibration direction of the light wave incident from the first birefringent region. A third birefringent region having a different speed, wherein the third birefringent region has a birefringent structure on at least one of the first birefringent region and the second birefringent region. Being formed in,

An imaging device characterized by the above-mentioned.

1 7. The birefringent structure, wherein at least one of the first birefringent region and the second birefringent region has a surface formed by depositing an obliquely deposited film. Item 17. The imaging device according to Item 16.

18. Between the first birefringent region and the second birefringent region that separates each of the incident light waves into two light waves, a third birefringent region with a different traveling speed depending on the vibration direction of the incident light wave is provided. A method for manufacturing an optical filter for filtering a predetermined spatial frequency component of the light wave,

An optical filter, wherein a birefringent structure is formed on the surface of at least one of the first birefringent region and the second birefringent region. Manufacturing method.

19. The method for manufacturing an optical filter according to claim 18, wherein the birefringent structure is formed by depositing an obliquely deposited film.