JPH05224159A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent the lowering of image quality by restraining an intensive ring-like flare from being generated on an optical low-pass filter provided with a diffraction grating. CONSTITUTION:The grating forming surface 2a of the optical low-pass filter 2 is arranged so as to face a solid-state image pickup element 4, and a shielding member 10 for shielding light reaching the almost whole parts of areas 8 and 9 other than the image pickup surface 4a of the solid-state image pickup element 4 is arranged between the image pickup lens 1 and the optical low-pass filter 2, or between the optical low-pass filter 2 and the solid-state image pickup element 4, or a shielding film functioning the same as the shielding member 10 is formed on the optical low-pass filter 2. Thus, the intensive ring-like flare is restrained from being generated when spot light is reflected on the areas 8 and 9 other than the image pickup surface 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device having an optical low pass filter made of a diffraction grating.

[0002]

2. Description of the Related Art A color image pickup device using a single-plate type solid-state image pickup device is provided with a color filter array to obtain a color signal from an object including a high frequency component corresponding to the pitch of the color filter array. Generates a false color signal. Further, the solid-state image pickup device has pixels arranged discontinuously and regularly, and a false signal due to aliasing is generated from an object including a high frequency component corresponding to the pixel pitch. Therefore, the optical system of such a color image pickup device is provided with an optical low-pass filter for preventing generation of a false color signal and a false signal. As an optical low-pass filter, an optical low-pass filter having three or more crystal plates and one infrared cutoff filter bonded together is used, but an optical low-pass filter having a laminated structure is inferior in mass productivity and expensive. There is a problem that is.

In order to solve the above problems, an optical low pass filter provided with a diffraction grating has been proposed. An example of an imaging device using such a diffraction grating is shown in FIG. In FIG. 10, the imaging device includes an imaging lens 31 and an optical low-pass filter 3 from the light incident side (subject side).
2 and the solid-state image sensor 34 are arranged in this order, and the grating forming surface 32 a of the optical low-pass filter 32 is directed to the solid-state image sensor 34. Solid-state image sensor 34
Are housed in a package 35, the optical low-pass filter 32 is attached to the front surface of the package 35, and is also used as a protective glass of the solid-state image sensor 4.

[0004]

When spotlight is photographed by using the image pickup device having the optical low-pass filter 32, a ring-shaped flare (hereinafter referred to as "ring-shaped flare") around the spotlight image. ) Occurs. For example, it occurs when a headlight of a car or an illumination light is photographed, which is a factor that deteriorates the image quality.

As a result of the present inventors' research on the above-mentioned ring-shaped flare, the following facts were found. (1) The main cause of the ring-shaped flare is that the reflected light from the surface of the solid-state imaging device 34 is the surface 32b on the opposite side of the grating forming surface 32a of the optical low-pass filter 32.
This is because the light is totally reflected at and is folded back toward the solid-state imaging device. (2) Since the metal film such as aluminum is formed on the surface of the area other than the image pickup surface of the solid-state image pickup element 34, the area other than the image pickup surface has a higher reflectance than the image pickup surface. When the spot light is incident on this area, a high intensity ring-shaped flare is generated.

The object of the present invention has been made in view of the above fact (2), in which spot light is prevented from entering an area other than the image pickup surface, and the image quality is remarkably deteriorated due to high intensity ring-shaped flare. To prevent.

[0007]

In order to achieve the above object, in an image pickup device of the present invention, an optical low-pass filter having a diffraction grating is arranged between an image pickup lens and a solid-state image pickup device, and In the imaging device in which the grating formation surface is directed to the solid-state imaging device side, a blocking member that blocks light reaching almost the entire area other than the imaging surface of the solid-state imaging device includes the imaging lens and the optical It is arranged between the low-pass filter and the optical low-pass filter and the solid-state image sensor.

Further, in another image pickup apparatus of the present invention, the optical low-pass filter is formed with a blocking film that blocks light reaching almost the entire area of the solid-state image pickup element other than the image pickup surface.

[0009]

According to the present invention, the blocking member or the blocking film prevents the spot light from entering the area other than the image pickup surface of the solid-state image pickup element, so that the phenomenon that a ring-shaped flare with high intensity occurs is prevented. Does not happen. Since there is a space between the image pickup lens and the optical low-pass filter, the blocking member can be easily arranged between them. When the blocking member is arranged between the optical low-pass filter and the solid-state image sensor, the position of the blocking member approaches the solid-state image sensor, so that the blocking region on the solid-state image sensor can be set accurately. Further, when the blocking film is provided on the optical low-pass filter, the structure becomes simpler than when the blocking member is arranged as a separate component.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an image pickup apparatus according to the first embodiment of the present invention. In the figure, an optical low-pass filter 2 is arranged between the imaging lens 1 and the solid-state imaging device 4, and its lattice forming surface 2a is directed to the solid-state imaging device 4 side. In the case of a color imaging device, the solid-state imaging device 4
The color filter array 6 is arranged in front of the. The solid-state image sensor 4 and the color filter array 6 are housed in a package 5, and the front surface of the package 5 is covered with a protective glass 3. The imaging lens 1 and the optical low pass filter 2
A blocking member 10 according to the present invention is disposed between and, and is supported by a frame (not shown) together with the imaging lens 1, the optical low pass filter 2 and the package 5.

The optical low-pass filter 2 has a transparent substrate 21 having a diffraction grating 22 extending in one direction or in two directions intersecting with each other in a plane orthogonal to the optical axis P.

The solid-state image pickup device 4 is arranged so that its image pickup surface 4a is orthogonal to the optical axis P. As shown in FIG. 2, the solid-state imaging device 4 has a rectangular image pickup surface 4a surrounded by a long side having a length x and a short side having a length y, in a horizontal direction H.
And a large number of photodetection elements 7 arranged along the vertical direction V. An area called an optical black 8 for obtaining a clear image by subtracting a dark current generated in the solid-state image pickup device 4 is provided on the outer circumference of the image pickup surface 4a of the solid-state image pickup device 4. A metal film such as aluminum is usually formed on the surface of the area 9, that is, the surface of the area other than the imaging surface 4a.

Next, the cause of the ring-shaped flare will be described with reference to FIG. Since the solid-state imaging device 4 has Si constituting the surface and Al used for wiring, the light reflectance of the surface is slightly high. Therefore, the imaging surface 4
A part of the light that has reached a is reflected by the imaging surface 4 a to become the reflected light 15, and the diffraction grating 22 of the optical low-pass filter 2
The light is diffracted by and is incident on the optical low-pass filter 2 and then reaches the transparent substrate surface 2b of the optical low-pass filter 2 at an incident angle θ, and is transmitted and reflected. The light reflected by the substrate surface 2b reaches the imaging surface 4a after being diffracted by the diffraction grating 22 of the optical low-pass filter 2 again.

Of the light incident on the substrate surface 2b, light whose incident angle θ is greater than or equal to the critical angle determined by the refractive index of air and the refractive index of the substrate 21 causes total reflection, so that the substrate surface 2b is below the critical angle. The intensity of the reflected light reaching the image pickup surface 4a is higher than that of the light incident on the. As a result, this strongly reflected light appears as a ring flare in the image. FIG. 5 shows the spot light image 11 and the ring-shaped flare 12 on the imaging surface 4 a. The ring-shaped flare 12 appears as a circle having a radius R around the spot light image.

As described above, the solid-state image pickup device 4 of FIG.
Since the metal film is formed on the surfaces of the regions 8 and 9 other than the imaging surface 4a, the reflectance of these regions 8 and 9 is higher than that of the imaging surface 4a. In particular, since a metal film having a large film thickness is formed on the entire surface of the optical black 8 of the solid-state imaging device 4 shown in FIG. 2 in order to make the light transmittance almost zero, the reflectance is further high. Therefore, when the spot light is incident on the areas 8 and 9 other than the imaging surface 4a, the strong reflected light 1
6 is generated, and the reflected light 16 generates a ring-shaped flare with extremely high intensity, which significantly deteriorates the image quality.

Therefore, in the present invention, the image pickup lens 1 shown in FIG.
The blocking member 10 is arranged between the optical low-pass filter 2 and the optical low-pass filter 2 to block the light reaching almost the entire regions 8 and 9 other than the imaging surface 4a.

The blocking member 10 has, for example, the shape shown in FIG. 5, and has an opening of an opaque plate such as metal or opaque plastic, the opening having a size corresponding to the area projected on the image pickup surface 4a of the solid-state image pickup device 4. It is formed by etching 13 and is also formed by patterning a metallic paint that blocks light on a transparent substrate such as glass or transparent plastic.

The size of the opening 13 is determined by the F number of the image pickup lens 1 of FIG. 1 and the distance D between the blocking member 10 and the image pickup surface 4a. In order to maximize the amount of light on the screen, the solid state image pickup of the opening 13 is performed. It is desirable that the projected area when projected onto the incident surface (including the image pickup surface 4a) of the element 4 be larger than that of the image pickup surface 4a. However, when the F number of the image pickup lens 1 is large, or when the distance D between the blocking member 10 and the image pickup surface 4a is short, there is a practical problem even if the projected area of the opening 13 is made the same as the size of the image pickup surface 4a. There is no. Even when the opening 13 is set large, the optical black 8 of FIG.
In order to suppress the amount of incidence on the region (FIG. 2), the opening 13
It is preferable that the projected area of the image is less than or equal to the size including the image pickup surface 4a and 1/2 of the area of the optical black 8.

According to the above structure, the blocking member 10 shown in FIG. 1 prevents the spot light from entering the area other than the image pickup surface 4a of the solid-state image pickup device 4, so that the ring-shaped flare of high strength shown in FIG. It does not generate 12. Also,
Since there is a space between the image pickup lens 1 and the optical low-pass filter 2, the blocking member 10 can be easily arranged in this space.

The blocking member 10 may be arranged between the optical low-pass filter 2 and the solid-state image sensor 4 as in the second embodiment shown in FIG. In this way, the blocking member 10
Since the position of is close to the solid-state imaging device 4, even if the position of the blocking member 10 is slightly deviated in the direction orthogonal to the optical axis P, the deviation of the position projected on the incident surface of the solid-state imaging device 4 is small. The blocking areas 8 and 9 on the incident surface can be set accurately.

FIG. 7 shows a third embodiment. In the figure,
The imaging surface 4a of the solid-state imaging device 4 is provided on the substrate surface 2b, which is the surface opposite to the grating formation surface 2a of the optical low-pass filter 2.
A blocking film 10A that blocks the light reaching almost the entire area other than the areas 8 and 9 is formed. This blocking film 10A is shown in FIG.
After vacuum-depositing a metal film such as aluminum or chrome on the substrate surface 2b of the optical low-pass filter 2 having a shape as shown in FIG. 2, a portion corresponding to the size projected on the imaging surface 4a is etched. It is created by removing it, and also created by printing an opaque paint.

According to the third embodiment, as compared with the first and second embodiments in which the blocking member 10 is arranged as a separate part, the structure is simplified by the number of parts being reduced.

FIG. 9 shows a fourth embodiment. In the figure,
The solid-state imaging device 4 with the color filter array 6 installed in the package 5 and the optical low-pass filter 2 provided with the blocking film 10A are integrated by an adhesive 19 via a rectangular frame-shaped spacer 18. The image pickup unit U is formed. The opening of the package 5 is covered with the protective glass 3. The spacer 18 is, for example, a metal film patterned by etching.

The positional relationship between the optical low-pass filter 2 and other elements including the solid-state image sensor 4 is important in order to exert the false color signal / fake signal suppressing function which is a feature of the optical low-pass filter 2. However, according to the fourth embodiment, since the relative positional relationship between the optical low-pass filter 2 and the imaging surface 4a is accurately set at the time of manufacturing by the spacer 18, the false color signal / false The signal suppressing function is effectively exerted.

The solid-state image pickup device 4 and the optical low-pass filter 2 may be integrated by screwing, bonding, encapsulation, or integral molding. Unlike the frame type, the spacer 18 may have a flat plate shape in which transparent resin films such as polyethylene terephthalate are stacked, or a photosensitive resin may be used as one of the solid-state image sensor 4 and the optical low-pass filter 2. Both may be photo-patterned. Further, a structure in which beads, rods, etc. having a certain diameter are included in the adhesive to form a spacer, and the distance between the solid-state imaging device 4 and the optical low-pass filter 2 is accurately maintained by these beads, rods, etc. May be

The blocking film 10A shown in FIGS. 7 to 9 is
It may be formed on the grating forming surface 2a of the optical low-pass filter 2.

[0027]

As described above, according to the present invention,
While the optical low-pass filter effectively blocks false signals and false color signals, the blocking member or blocking film prevents the spot light from entering an area other than the image pickup surface of the solid-state image pickup element, and thus creates a strong ring flare. It is possible to suppress the deterioration of image quality due to the occurrence of. In addition, because there is a space between the image pickup lens and the optical low-pass filter,
In the meantime, the blocking member can be easily arranged, and when the blocking member is arranged between the optical low-pass filter and the solid-state image sensor, the position of the blocking member approaches the solid-state image sensor. The blocking area can be set accurately. Further, when the blocking film is provided on the optical low-pass filter, the structure becomes simpler than when the blocking member is arranged as a separate component.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a solid-state imaging device of the same embodiment.

FIG. 3 is a side view showing an optical low-pass filter and a solid-state image sensor according to the same embodiment.

FIG. 4 is a front view showing an image pickup surface of the solid-state image pickup element of the embodiment.

FIG. 5 is a perspective view showing a blocking member of the embodiment.

FIG. 6 is a schematic configuration diagram showing an imaging device according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing an image pickup apparatus according to a third embodiment of the present invention.

FIG. 8 is a perspective view showing a blocking film of the third embodiment.

FIG. 9 is a vertical sectional side view showing a main part of an image pickup apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing a conventional imaging device.

[Explanation of symbols]

1 ... Imaging lens, 2 ... Optical low-pass filter, 2a ...
Lattice forming surface, 4 ... Solid-state imaging device, 4a ... Imaging surface, 5 ... Package, 6 ... Color filter array, 8, 9 ... Area other than imaging surface, 10 ... Blocking member, 10A ... Blocking film.

Claims (3)

[Claims] 1. An optical low-pass filter having a diffraction grating is arranged between an imaging lens and a solid-state imaging device,
In the image pickup apparatus whose lattice forming surface faces the solid-state image pickup device side, a blocking member that blocks light reaching almost the entire area of the solid-state image pickup device other than the image pickup surface includes the image pickup lens and the optical low-pass filter. An imaging device, which is arranged between the filter and the filter. 2. An optical low-pass filter having a diffraction grating is arranged between an imaging lens and a solid-state imaging device,
In the image pickup device whose lattice forming surface faces the solid-state image pickup device side, a blocking member that blocks light reaching almost the entire region other than the image pickup surface of the solid-state image pickup device includes the optical low-pass filter and the solid-state image pickup device. An image pickup apparatus, which is arranged between image pickup elements. 3. An optical low-pass filter having a diffraction grating is arranged between an imaging lens and a solid-state imaging device,
In the image pickup device whose lattice forming surface faces the solid-state image pickup device side, a blocking film that blocks light reaching almost the entire region of the solid-state image pickup device other than the image pickup surface is formed in the optical low-pass filter. An imaging device characterized by the above.