JP2001284561A - Solid-state imaging device - Google Patents

Abstract

(57) [Problem] To reduce the thickness of an optical low-pass filter provided between an imaging lens and an imaging device by using a birefringent plate as a cover glass of a solid-state imaging device, and to reduce the thickness of the imaging lens and the imaging device. Allow more space between them. A flat solid-state imaging device is embedded in a bottom surface of a concave portion of a casing. A lithium niobate (LN) plate 15 having birefringence is fitted into a step portion 14 formed on the periphery of the concave portion 12 and bonded with an adhesive. Nitrogen is sealed in the casing 11. LN board 15
A quartz plate 16 is attached to the surface of the solid-state imaging device 13 using an ultraviolet curable resin. Outer surface 15 of LN plate 15
An infrared cut coat is applied to s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for suppressing a moire generated as a pseudo signal when a stripe pattern of a subject and a pixel pitch of an image sensor are close to each other in an image pickup apparatus provided in a digital camera or a video camera, for example. The present invention relates to a low-pass filter mounting structure.

[0002]

2. Description of the Related Art Conventionally, there is known an apparatus using an image pickup apparatus such as a digital camera in which an optical low-pass filter (spatial frequency filter) is provided between an image pickup lens and the image pickup apparatus. The optical low-pass filter is a filter for preventing a moiré caused by a beat between a pixel pitch of an image sensor and a spatial frequency of a subject, and restricts a spatial frequency of light incident on the image sensor to obtain an image obtained by an imaging device. Image quality can be improved.

According to the configuration in which the optical low-pass filter is provided, a space corresponding to the thickness of the optical low-pass filter must be provided between the imaging lens and the imaging device, which is a great obstacle in optical design.

[0004]

SUMMARY OF THE INVENTION The present invention reduces the thickness of an optical low-pass filter provided between an image pickup lens and an image pickup device, and mounts the optical low-pass filter so that a wider space can be secured between the image pickup lens and the image pickup device. The purpose is to obtain the structure at low cost.

[0005]

A solid-state imaging device according to the present invention is an imaging device having a solid-state imaging device provided in a casing, wherein a first birefringent plate for a cover for covering the solid-state imaging device is provided in the casing. It is characterized in that the space between the periphery of the first birefringent plate and the casing is sealed so that the inside of the casing is shielded from the outside air.

For example, a second birefringent plate is provided on the first birefringent plate on the side of the solid-state imaging device. Accordingly, the effect of the optical low-pass filter can be improved without taking a space for the optical low-pass filter between the imaging lens and the imaging device. At this time, preferably, the second birefringent plate is adhered to the surface of the first birefringent plate on the solid-state imaging device side with an ultraviolet curable resin. Further, the second birefringent plate has a first birefringent plate.
It is preferably a flat plate member smaller than the birefringent plate. The second birefringent plate is formed from, for example, a quartz plate.
Still further, between the first birefringent plate and the second birefringent plate,
For example, an infrared cut filter is provided.

For example, a third birefringent plate is provided on the opposite side of the first birefringent plate from the solid-state imaging device. At this time, for example, an infrared cut filter is provided between the first birefringent plate and the third birefringent plate in close contact with the first birefringent plate and the third birefringent plate. This makes it possible to more effectively remove infrared light from light incident on the solid-state imaging device, and to prevent deterioration of the infrared cut filter due to moisture absorption.

For example, instead of an infrared cut filter, an infrared cut coat is applied to at least one surface of the birefringent plate. The infrared cut coat can remove infrared rays from light incident on the solid-state imaging device without taking up space.

Preferably, each of the birefringent plates is provided in parallel with the solid-state imaging device. The first birefringent plate is preferably made of lithium niobate, and the second and third birefringent plates are also made of lithium niobate, for example. Thereby, the birefringent plate for the cover can be made thin.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 and 2 show an image pickup apparatus using an optical low-pass filter mounting structure using lithium niobate. In addition, FIG.
It is sectional drawing which follows the II-II line.

The casing 11 of the image pickup apparatus has a flat box shape made of, for example, a ceramic material and has a thin flat plate-shaped concave portion 12. A flat solid-state imaging device 13 is embedded in the bottom surface of the concave portion 12. A step 14 is formed on the periphery of the recess 12 so as to surround the entire recess 12. The step portion 14 is made of a transparent lithium niobate (L) having birefringence in place of a commonly used cover glass.
(N) A plate (first birefringent plate) 15 is fitted and covers the solid-state imaging device 13. The peripheral portion of the cover LN plate 15 is fixed to the step portion 14 with an adhesive, whereby the space between the peripheral portion of the cover LN plate 15 and the casing 11 is sealed. That is, the inside of the casing 11 is shut off from the outside air by the cover LN plate 15, and nitrogen is sealed therein.

A quartz plate (second birefringent plate) 16 is adhered to a surface of the cover LN plate 15 on the side of the solid-state image sensor 13. The cover LN plate 15 also plays a role as an optical low-pass filter together with the quartz plate 16. Crystal plate 16
Is mounted on the cover LN plate 15 with an adhesive made of an ultraviolet curable resin applied to the entire surface thereof, and is fixed to the cover LN plate 15 by irradiating ultraviolet rays.

The crystal plate 16 is a plate-like member having substantially the same size as the solid-state imaging device 13 and is opposed to the solid-state imaging device 13 in parallel. The surface of the quartz plate 16 has a cover L
It is slightly smaller than the N plate 15. Between the quartz plate 16 and the solid-state imaging device 13, a gap having substantially the same size as the thickness of the quartz plate 16 is formed.

An infrared cut coat for absorbing light in an infrared wavelength range is applied to a surface 15s on the outer side (the imaging lens side) of the cover LN plate 15. The light transmitted through the imaging lens enters the imaging device via the infrared cut coat applied to the surface 15s of the cover LN plate 15, and the solid-state imaging device 13
Is received at. At this time, light in the infrared wavelength region is absorbed by the infrared cut coat, and the solid-state imaging device 13 can detect an image of the subject with a more natural color.

The shape and size of the quartz plate 16 and the size of the gap between the quartz plate 16 and the solid-state image sensor 13 are determined by:
Needless to say, it can be changed as needed.

As described above, according to the first embodiment of the present invention, by using the lithium niobate plate 15 having birefringence and functioning as an optical low-pass filter, instead of the ordinary cover glass, Space for the thickness of the cover glass can be saved. In addition, an infrared cut coat is applied to the outer surface 15s of the cover LN plate 15, and there is no need to separately provide an infrared cut filter between the imaging lens and the imaging device. Therefore, a wider space can be secured between the imaging lens and the imaging device, and the degree of freedom in design increases. This also simplifies the configuration.

As a method for saving the space corresponding to the thickness of the cover glass, an infrared cut filter may be used as the cover glass. However, the infrared cut filter generally does not easily adhere to the casing 11 and has a low yield. Therefore, there is a problem that the cost increases. But,
Since the lithium niobate plate does not have such a problem, a space corresponding to the thickness of the cover glass can be saved without increasing the manufacturing cost.

Next, a second embodiment of the present invention will be described with reference to FIG. Since the configuration of the second embodiment is substantially the same as that of the first embodiment, only portions different from the first embodiment will be described.

In the second embodiment, an infrared cut filter 20 is used instead of the infrared cut coat applied to the outer surface 15s of the cover LN plate 15 in the first embodiment. It is stuck on the outer surface, and substantially the same effect as in the first embodiment can be obtained in the second embodiment. In the second embodiment, a space corresponding to the thickness of the infrared cut filter 20 is required between the imaging lens and the imaging device as compared with the first embodiment. However, it also has a high performance of absorbing infrared rays and can sufficiently improve the quality of a captured image.

FIG. 4 shows a third embodiment of the present invention. A third embodiment will be described with reference to FIG.

In the third embodiment, an LN plate (third plate) is provided on the outer surface of the infrared cut filter 20 in the second embodiment.
(Birefringent plate) 30 is stuck. LN plate 3
0, so that the cover LN plate 15 and the quartz plate 16 integrally function as an optical low-pass filter.
The N plates 15 and 30 are also arranged such that the directions of image shift due to their birefringence are different from each other.

In the third embodiment, substantially the same effects as those in the first and second embodiments can be obtained, but since a plurality of LN plates are used for the optical low-pass filter, the performance of the entire optical low-pass filter is improved. And higher image quality can be obtained.

Next, a fourth embodiment will be described with reference to FIG. The fourth embodiment is different from the third embodiment in that
The crystal plate 16 is removed, and other configurations are the same as those of the third embodiment. In the fourth embodiment, substantially the same effects as in the third embodiment can be obtained.
Unlike the first to third embodiments, it is not necessary to attach the crystal plate 16 inside the casing 11, so that the manufacturing process can be simplified and the manufacturing cost can be reduced.

In the third and fourth embodiments,
The infrared cut filters are the cover LN plate 15 and LN plate 30
, The deterioration of optical characteristics due to moisture absorption of the infrared cut filter can be prevented, and the thickness can be reduced.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, the infrared cut filter 20 is removed from the fourth embodiment, and a quartz plate 16 ′ is directly attached to the outer surface of the cover LN plate 15. Also, instead of the infrared cut filter 20, an infrared cut coat is applied to the outer surface 16s 'of the quartz plate 16'. At this time, the cover LN plate 15 and the quartz plate 16 'cooperate to play a role as an optical low-pass filter. Therefore, in the fifth embodiment, substantially the same effect as in the fourth embodiment can be obtained, but a space corresponding to the thickness of the infrared cut filter is set between the imaging lens and the imaging device as compared with the fourth embodiment. Can be secured.

In the second and third embodiments,
Each of the quartz plates 16 and 16 ′ is composed of several or one LN
You may comprise a board.

In the first and fourth embodiments, the infrared cut coat is applied to the outer surface of the cover LN plate 15 and the quartz plate 16 ′.
May be applied to the surface on the side of the solid-state imaging device 13.

Next, a sixth embodiment of the present invention will be described with reference to FIG. In the sixth embodiment, the infrared cut filter 20 is attached to the inner surface of the cover LN plate 15, and the LN plate 30 is further attached to the surface of the infrared cut filter 20 on the solid-state imaging device 13 side. Since the infrared cut filter 20 and the LN plate 30 are arranged in the casing 11, a wider space between the imaging lens and the imaging device can be secured. Also, the infrared light included in the incident light is
It is efficiently absorbed by the infrared cut filter 20. Further, since the infrared cut filter 20 is shielded from the outside air, the problem of deterioration of optical characteristics due to moisture absorption can be prevented.

[0029]

As described above, according to the present invention, the thickness of the optical low-pass filter provided between the imaging lens and the imaging device can be reduced, and the space between the imaging lens and the imaging device can be secured more widely. Mounting structure can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an image pickup apparatus using an optical low-pass filter mounting structure according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a diagram schematically illustrating a cross section of an imaging device using an optical low-pass filter mounting structure according to a second embodiment;

FIG. 4 is a diagram schematically showing a cross section of an imaging device using an optical low-pass filter mounting structure according to a third embodiment.

FIG. 5 is a diagram schematically illustrating a cross section of an imaging device using an optical low-pass filter mounting structure according to a fourth embodiment.

FIG. 6 is a diagram schematically illustrating a cross section of an imaging device using an optical low-pass filter mounting structure according to a fifth embodiment.

FIG. 7 is a diagram schematically illustrating a cross section of an imaging device using an optical low-pass filter mounting structure according to a sixth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Casing 13 Solid-state image sensor 15 LN plate for cover 16 Quartz plate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H01L 31/02 H01L 27/14 D 5F088 H04N 101: 00 31/02 BF Term (Reference) 2H048 CA12 CA17 CA24 2H049 BA01 BA42 BB66 BC21 4M118 AA05 AA10 AB01 FA06 GC11 GC20 HA02 5C022 AA13 AB13 AB39 AC42 5C024 BX01 CY37 CY48 EX22 EX23 EX24 EX51 GY01 5F088 BA20 BB03 EA04 JA13 JA20

Claims (11)

[Claims] 1. An imaging apparatus having a solid-state imaging device provided in a casing, wherein a first birefringent plate for a cover that covers the solid-state imaging device is attached to the casing, and the inside of the casing is shielded from outside air. A solid-state imaging device, wherein a space between a peripheral portion of the first birefringent plate and a casing is sealed. 2. The solid-state imaging device according to claim 1, wherein a second birefringent plate is provided on a side of the first birefringent plate on the solid-state imaging device side. 3. The solid-state imaging device according to claim 2, wherein the second birefringent plate is affixed to a surface of the first birefringent plate on a solid-state imaging device side with an ultraviolet curable resin. . 4. The solid-state imaging device according to claim 2, wherein the second birefringent plate is a flat member smaller than the first birefringent plate. 5. The solid-state imaging device according to claim 2, wherein the second birefringent plate is formed from a quartz plate. 6. The solid-state imaging device according to claim 2, wherein an infrared cut filter is provided between the first birefringent plate and the second birefringent plate. 7. The solid-state imaging device according to claim 1, wherein a third birefringent plate is provided on a side of the first birefringent plate opposite to the solid-state imaging device. 8. An infrared cut filter is provided between the first birefringent plate and the third birefringent plate in close contact with the first birefringent plate and the third birefringent plate. The solid-state imaging device according to claim 7, wherein: 9. At least one of the birefringent plates,
The solid-state imaging device according to claim 3, wherein one surface thereof is provided with an infrared cut coat. 10. The solid-state imaging device according to claim 3, wherein each of the birefringent plates is provided in parallel with the solid-state imaging device. 11. The solid-state imaging device according to claim 1, wherein the birefringent plate is made of lithium niobate.