JP4356311B2 - Solid-state imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state imaging device in which a plurality of pixels having a light receiving region that generates a signal charge according to light incident on a light receiving surface is two-dimensionally arranged.
[0002]
[Prior art]
Conventionally, solid-state imaging devices in which a plurality of pixels are two-dimensionally arranged are used for various purposes.
Such a solid-state imaging device includes an OLPF (Optical Low Pass) that removes a predetermined spatial frequency component in order to reduce aliasing caused by aliasing of the Nyquist frequency and false color that is noticeable in the case of an imaging device having a plurality of color filters. Some filters are provided with an optical low-pass filter.
[0003]
Further, Patent Document 1 invented by the present inventor is known as a solid-state imaging device having rectangular pixels.
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-23171
[Problems to be solved by the invention]
However, the conventional solid-state imaging device provided with the OLPF has a problem in that the sharpness is remarkably reduced as compared with the solid-state imaging device not provided with the OLPF.
[0005]
Further, in a solid-state imaging device used in an apparatus such as an electronic camera that involves image processing, a plurality of pixels are arranged two-dimensionally, and a plurality of OLPFs are used to uniformly blur incident light in a plurality of directions. It is necessary to provide. For example, to realize a square aperture by uniformly blurring the incident light in the vertical and horizontal directions, an OLPF that blurs the incident light in the vertical direction and an OLPF that blurs the incident light in the horizontal direction are required. Become.
[0006]
Therefore, in the conventional solid-state imaging device, by providing a plurality of OLPFs, the cost increases, the interface in the optical path increases, flare increases, the thickness of the entire OLPF increases, and the aberration characteristic of the optical system increases. Problems such as deterioration and increased space have occurred.
[0007]
Therefore, in the present invention, a solid that can reduce the false color and prevent the reduction of sharpness in a well-balanced manner and can minimize the number of optical members that blur incident light (including multiplexing). An object is to provide an imaging device.
[0008]
Another object of the present invention is to receive light from each pixel in the solid-state imaging device (specifically, a solid-state imaging device having pixels having an extremely rectangular shape with a pixel aspect ratio of “2: 1”). It is to provide a technique for enhancing the characteristics.
[0009]
[Means for Solving the Problems]
The solid-state imaging device according to claim 1 has a rectangular light receiving region that individually generates a signal charge according to light incident on the light receiving surface, and the light receiving region has a short side direction with respect to the short side direction of the light receiving region. A plurality of pixels that are two-dimensionally offset by 1/2 of the pixel pitch in the long side direction , and a zigzag shape in the short side direction according to the configuration of the offset arrangement of the plurality of pixels, and A CCD electrode provided for each light receiving region and supplied with a pulse signal for controlling reading of the signal charge to the CCD transfer path, and a scanning means for scanning the signal charge to the outside by supplying the pulse signal to the CCD electrode And a single optical member that is provided on the light receiving surface side of the plurality of pixels and divides the light incident on the light receiving surface into the pixel pitch in the short side direction. These light receiving areas have a rectangular shape whose aspect ratio is approximated to “2: 1”. The plurality of pixels are separated for each pixel group arranged in one direction of the light receiving surface, and signal charges are sequentially transferred in one direction of the light receiving surface, and the scanning unit transfers the plurality of pixels to one of the light receiving surfaces. Driving is performed for each pixel group arranged in a direction orthogonal to one direction, and signal charges are scanned by a frame transfer method.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
However, in the following description, a frame transfer type monochrome solid-state imaging device will be described as an example of the solid-state imaging device of the present invention.
[0013]
<< Description of First Embodiment >>
FIG. 1 is a diagram illustrating a schematic configuration of a solid-state imaging apparatus corresponding to the first embodiment. In FIG. 1, the solid-state imaging device 1 includes a housing 12 whose opening is closed by a glass substrate 11, an OLPF 13 stacked on the glass substrate 11, and a light receiving surface that faces the glass substrate 11. 12 and an imaging chip 14 provided internally.
[0014]
In FIG. 1, a plurality of pixels 141 are two-dimensionally arranged on the imaging chip 14. Each pixel 141 is a rectangle whose length ratio between the long side direction and the short side direction is approximated to “2: 1”. For the short side direction, 1/1 of the pixel pitch in the long side direction. They are offset by two and are arranged in a zigzag, and are arranged substantially in a straight line with respect to the long side direction.
[0015]
The OLPF 13 divides incident light by the pixel pitch in the short side direction with respect to the short side direction of the pixel 141.
As a result, as shown in FIG. 2, the equivalent aperture of each pixel 141 is enlarged in the short side direction of the pixel 141 to become a square shape, and the pixels 141 adjacent to each other in the short side direction overlap each other. . However, in FIG. 2, the apertures of the odd-numbered pixels 141 are indicated by solid lines and the even-numbered pixel 141 apertures are indicated by dotted lines with the short side direction as a reference.
[0016]
The sample points for each pixel 141 are as shown in FIG.
By the way, when the solid-state imaging device 1 is a frame transfer type solid-state imaging device, most of each pixel 141 is occupied by a light receiving region (a region for generating a signal charge corresponding to incident light).
[0017]
FIG. 4 is a diagram illustrating a configuration of a light receiving region in the first embodiment.
In FIG. 4, each light receiving region 142 (indicated by a dotted line) has a length ratio of “2: 1” between the long side direction and the short side direction, similarly to the pixel 141 shown in FIG. 1. A rectangle to be approximated (strictly, the length in the short side direction is the length from the center of the channel stop to the center of the adjacent channel stop), and for the short side direction, it is 1/2 of the pixel pitch in the long side direction. They are offset one by one and are arranged in a zigzag, and are arranged on a substantially straight line in the long side direction.
[0018]
Further, in FIG. 4, a channel stop 143 is provided for each column (pixel group) of the light receiving regions 142 arranged in the vertical transfer direction of the light receiving surface (corresponding to the long side direction of the light receiving region). A two-phase transparent electrode 144 is provided for each light receiving region 142 (pixel group) arranged in a zigzag direction (corresponding to the short side direction of the light receiving region). Such transparent electrodes 144 are supplied with pulse signals φ1A and φ2A for signal charge transfer.
[0019]
According to the configuration shown in FIG. 4, a plurality of light receiving regions 142 are separated for each column arranged in the vertical transfer direction of the light receiving surface by the channel stop 143, and are generated in the light receiving region 142 provided with the common transparent electrode 144. Can be transferred simultaneously in the vertical transfer direction of the light receiving surface. Therefore, similarly to the existing frame transfer type solid-state imaging device, it is possible to scan the signal charges by the frame transfer method via the storage unit and the horizontal reading unit (not shown).
[0020]
As described above, in the first embodiment, only the single OLPF 13 that blurs the incident light by the pixel pitch in the short side direction with respect to the short side direction of the light receiving region 142 (substantially coincides with the pixel 141) is provided. An equivalent aperture as shown in FIG. 2 is obtained. Therefore, it is possible to reduce the false color due to the Nyquist frequency aliasing while minimizing the reduction in sharpness, and at the same time, the conventional problem (cost increase, which has occurred by providing a plurality of optical members that blur incident light) Increase in flare, deterioration of aberration characteristics of the optical system, increase in space, etc.) can be avoided.
[0021]
In the first embodiment, the transparent electrode 144 is formed in a zigzag shape as shown in FIG. 4 to realize the pixel arrangement of FIG. 1 (1/2 offset in alternating rows).
[0022]
In the first embodiment, as shown in FIG. 4, the light receiving regions 142 (in the first embodiment, the pixels 141 are arranged so that the long side direction of each light receiving region 142 coincides with the vertical transfer direction of the light receiving surface. However, as shown in FIG. 5, the light receiving region 142 may be arranged so that the long side direction coincides with the horizontal transfer direction of the light receiving surface.
[0023]
However, when the light receiving region 142 is arranged as shown in FIG. 5, in order to realize signal charge scanning by the frame transfer method, the channel stop 143 is set in the vertical transfer direction of the light receiving surface (corresponding to the short side direction of the light receiving region). Are provided for each column of the light receiving regions 142 arranged in a zigzag manner, and the transparent electrode 144 is disposed in the horizontal transfer direction of the light receiving surface (corresponding to the long side direction of the light receiving region) (dotted line) It is necessary to provide a common area for each of the areas surrounded by When transferring in two phases, a two-phase electrode is assigned to each light receiving area.
[0024]
Further, when the light receiving region 142 is arranged as shown in FIG. 5, the short side direction of the pixel 141 coincides with the vertical transfer direction of the light receiving surface, so that incident light is blurred with respect to the short side direction of the pixel 141. In this case, it is necessary to change the blurring direction of the incident light by the OLPF 13 to the vertical transfer direction of the light receiving surface.
[0025]
<< Description of Second Embodiment >>
FIG. 6 is a diagram illustrating a schematic configuration of a solid-state imaging apparatus corresponding to the second embodiment.
In FIG. 6, the solid-state imaging device 2 is similar to the solid-state imaging device 1 corresponding to the first embodiment shown in FIG. 1, and a housing 22 whose opening is closed by a glass substrate 21, and a glass substrate 21. And an imaging chip 24 provided in the housing 22 so that the light receiving surface faces the glass substrate 21.
[0026]
In FIG. 6, a plurality of pixels 241 are two-dimensionally arranged on the imaging chip 24. Each pixel 241 is a rectangle whose length ratio between the long side direction and the short side direction is approximated to “2: 1”. For the short side direction, 1/1 of the pixel pitch in the long side direction. They are offset by two and are arranged in a zigzag, and are arranged substantially in a straight line with respect to the long side direction.
[0027]
However, in FIG. 6, unlike FIG. 1, each pixel 241 is inclined 45 degrees with respect to the horizontal transfer direction and the vertical transfer direction of the light receiving surface.
The OLPF 23 divides incident light by the pixel pitch in the short side direction with respect to the short side direction of the pixel 241.
As a result, as shown in FIG. 7, the aperture of each pixel 241 expands in the short side direction of the pixel 241 to have a square shape, and overlaps between the pixels 241 adjacent in the short side direction.
[0028]
Also, the sample points for each pixel 241 are as shown in FIG.
FIG. 9 is a diagram illustrating a configuration of a light receiving region in the second embodiment.
In FIG. 9, each light receiving region 242 (region surrounded by a dotted line) has a length ratio of “2: 1” between the long side direction and the short side direction, similarly to the pixel 241 shown in FIG. 6. It is a rectangle that is approximated, and is arranged in a zigzag manner offset by 1/2 of the pixel pitch in the long side direction with respect to the short side direction, and is arranged substantially in a straight line with respect to the long side direction. .
[0029]
However, in FIG. 9, a channel stop 243 is provided for each column (pixel group) of the light receiving regions 242 arranged zigzag along the vertical transfer direction of the light receiving surface, and in the case of two-phase driving, the horizontal transfer direction of the light receiving surface. A two-phase transparent electrode 244 is provided for each light receiving region 242 (pixel group) arranged in a zigzag pattern. Such transparent electrodes 244 are supplied with pulse signals φ1A and φ2A for transferring signal charges.
[0030]
According to the configuration as shown in FIG. 9, a plurality of light receiving regions 242 are separated by a column stop 243 into columns arranged in a zigzag manner along the vertical transfer direction of the light receiving surface, and a light receiving device provided with a common transparent electrode 244 is provided. Signal charges generated in the region 242 (corresponding to the light receiving regions 242 arranged in a zigzag manner along the horizontal transfer direction of the light receiving surface) can be simultaneously transferred in the vertical transfer direction of the light receiving surface. Therefore, similarly to the existing frame transfer type solid-state imaging device, it is possible to scan the signal charges by the frame transfer method via the storage unit and the horizontal reading unit (not shown).
[0031]
As described above, in the second embodiment, the aperture as shown in FIG. 7 is obtained only by including the single OLPF 23 that divides incident light by the pixel pitch in the short side direction with respect to the short side direction of the light receiving region 242. can get. Therefore, as in the first embodiment, aliasing due to Nyquist frequency aliasing can be reduced while minimizing the reduction in sharpness, and a plurality of optical members that blur incident light are provided. The conventional problem can be avoided.
[0032]
In the second embodiment, the shape of the channel stop 243 and the transparent electrode 244 is zigzag as shown in FIG. 9 even if the shape and arrangement of each light receiving region 242 are different from those of the existing frame transfer type solid-state imaging device. By doing so, it is possible to easily realize signal charge scanning by the frame transfer method.
Further, in the second embodiment, the sample points for each pixel 241 are square lattice sample points as shown in FIG.
[0033]
In each of the above-described embodiments, the frame transfer type solid-state imaging device has been described as an example of the solid-state imaging device of the present invention. By adopting such a frame transfer method, it is possible to use most of the rectangular pixels as an effective light receiving area even though the pixel aspect ratio is an extreme rectangular pixel of about “2: 1”. As a result, it is possible to realize a solid-state imaging device having excellent light receiving efficiency while adopting a rectangular pixel having an extreme pixel aspect ratio.
[0034]
The present invention is not limited to such a frame transfer method. For example, it is possible to adopt an interline transfer method. However, when the above configuration is realized in the interline transfer format, since the pixel aspect ratio of the light receiving region is an extreme value, problems such as sensitivity deterioration due to a decrease in aperture ratio are likely to occur.
Conventionally, in order to increase the light receiving efficiency of this interline transfer method, it is often performed to provide a microlens for each pixel. However, since the solid-state imaging device of the present invention has an extreme pixel aspect ratio of “2: 1”, it is very difficult to design an appropriate microlens.
[0035]
For example, when the microlens is formed in accordance with a pixel shape having a side length of about “2: 1”, an elliptical microlens as shown in FIG. However, when an elliptical lens is used as a microlens on a rectangular light-receiving part, the light collection characteristics differ between the long side direction and the short side direction, resulting in problems such as no blurring.
[0036]
In order to avoid such a problem, it is preferable to arrange two microlenses in the long side direction of the pixel (light receiving region) as shown in FIG. By providing a compound eye type microlens for the rectangular light receiving region in this way, the light condensing characteristics of each pixel become substantially isotropic even though the pixel has an extremely rectangular pixel aspect ratio.
[0037]
Furthermore, by providing a light shielding portion in the boundary region between the plurality of microlenses, it is possible to block light from an irregular direction, and it is possible to further increase the isotropic property of the light collecting characteristics of the rectangular pixels.
[0038]
Further, in FIG. 10B, a common storage unit is provided under the compound-eye microlens. Therefore, the signal charges generated by the incident light of the compound-eye microlens can be accumulated and added together in units of rectangular pixels. As a result, it is easy to simplify the transfer sequence of the solid-state imaging device by omitting the sequence operation for pixel addition.
[0039]
In the solid-state imaging devices 1 and 2 corresponding to each of the above-described embodiments, the OLPFs 13 and 23 are provided. As the OLPF, for example, light incident on the light receiving surface is received as a light receiving region like a diffraction grating. Any optical member may be provided as long as the optical member can be blurred in the short side direction.
[0040]
Furthermore, in the solid-state imaging devices 1 and 2 corresponding to the above-described embodiments, the openings of the housings 12 and 22 are closed by the glass substrates 11 and 21, but the OLPF 13 and the glass substrates 11 and 21 are not provided. 23 may close the openings of the casings 12 and 22.
[0041]
In each of the above-described embodiments, a monochrome solid-state imaging device not provided with a color filter has been described. However, the present invention can be similarly applied to a color solid-state imaging device having a plurality of color filters. False color generated by aliasing can be reduced.
For example, in the solid-state imaging device 1 corresponding to the first embodiment, three color filters of R, G, and B are arranged in an array as shown in FIG. , B in an array in which the color filters are alternately arranged to form a stripe), the apertures are as shown in FIG. 11B.
[0042]
Such an aperture is used in a two-plate type solid-state image pickup device (a solid-state image pickup device having an image pickup element provided with only a G color filter and an image pickup element provided with R and B color filters in a checkered pattern). This is equivalent to an aperture in which two image sensors are shifted by 1/2 pixel pitch, and is effective for a color solid-state imaging device.
[0043]
Note that the color filter provided in each pixel is not limited to the three colors R, G, and B, and may be any color type such as four colors of Ye, Mg, Cy, and G. The arrangement is not limited to 11 (1).
[0044]
【The invention's effect】
As described above, according to the solid-state imaging device of the present invention, even if the number of optical members that blur incident light (including when multiplexed) is one, defects due to aliasing caused by aliasing of the Nyquist frequency are eliminated. Appropriate suppression is possible, and a reduction in sharpness can be minimized. In the case of a color image sensor, it is possible to reduce the false color and prevent the sharpness from being lowered with a good balance. Further, conventional problems (such as an increase in cost, an increase in flare, a deterioration in aberration characteristics of the optical system, an increase in space, etc.) that have occurred by providing a plurality of optical members that blur incident light can be avoided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a solid-state imaging apparatus corresponding to a first embodiment.
FIG. 2 is a diagram showing an aperture state in the first embodiment.
FIG. 3 is a diagram showing sample points in the first embodiment.
FIG. 4 is a diagram illustrating a configuration of a light receiving region in the first embodiment.
FIG. 5 is a diagram showing another configuration of the light receiving region in the first embodiment.
FIG. 6 is a diagram illustrating a schematic configuration of a solid-state imaging apparatus corresponding to a second embodiment.
FIG. 7 is a diagram showing an aperture in the second embodiment.
FIG. 8 is a diagram showing sample points in the second embodiment.
FIG. 9 is a diagram illustrating a configuration of a light receiving region in the second embodiment.
FIG. 10 is a diagram illustrating a configuration example of a pixel when a microlens is provided.
FIG. 11 is a diagram illustrating a state of an aperture when a color filter is provided.
[Explanation of symbols]
1, 2 Solid-state imaging device 11, 21 Glass substrate 12, 22 Housing 13, 23 OLPF
14, 24 Imaging chip 141, 241 Pixel 142, 242 Light receiving area 143, 243 Channel stop 144, 244 Transparent electrode

Claims (1)

Each pixel has a rectangular light receiving region that generates a signal charge in response to light incident on the light receiving surface, and each half of the pixel pitch in the long side direction of the light receiving region with respect to the short side direction of the light receiving region. A plurality of pixels offset and arranged two-dimensionally;
A pulse signal that is provided in each light receiving region in a zigzag manner in the short side direction in accordance with the offset arrangement form of the plurality of pixels and that controls reading of the signal charges to the CCD transfer path is provided. A CCD electrode to be supplied;
Scanning means for scanning the signal charge and supplying it to the outside by supplying the pulse signal to the CCD electrode;
A plurality of pixels provided on the light receiving surface side, and a single optical member that divides the light incident on the light receiving surface into pixel pitches in the short side direction, and
The light receiving area is a rectangle whose aspect ratio is approximated to “2: 1”;
The plurality of pixels are separated for each pixel group arranged in one direction of the light receiving surface, and sequentially transfer the signal charges in one direction of the light receiving surface,
The scanning means drives the plurality of pixels for each pixel group arranged in a direction orthogonal to one direction of the light receiving surface, and scans the signal charges by a frame transfer method. apparatus.

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