JP2010278664A - Solid-state imaging sensor and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lowering of light quantity at a peripheral part of a picked up image in treatment on an imaging element side with a relatively simple configuration. <P>SOLUTION: The imaging element includes: a photodetector evenly spaced arrangement part 11a; a photodetector extension arrangement part 11b; and an output part for outputting photodetector signals accumulated in photodetectors arranged in both arrangement parts as imaging signals. The photodetector evenly spaced arrangement part 11a arranges photodetectors at regular intervals in horizontal and vertical directions, areas of light receiving regions of the respective photodetectors are equal in the first area and arranged almost in the center. The photodetector extension arrangement part 11b is arranged at a peripheral position symmetrical with respect to the photodetector evenly spaced arrangement part 11a as a center. As a configuration of the photodetector extension arrangement part 11b, it is arranged at wider intervals than regular intervals in the photodetector evenly spaced arrangement part 11a and areas of light receiving regions of the respective photodetector are increasingly larger than the first area as the photodetectors go away from the photodetector evenly spaced arrangement part. Extension of the area is designed on the basis of aperture efficiency of a lens system, for example. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device suitable for application to various imaging devices such as a CCD type imager and a CMOS type imager, and an imaging device including the solid-state imaging device.

  Conventionally, a solid-state imaging device such as a CCD (Charge Coupled Device) type imager or a CMOS (Complementary Metal Oxide Semiconductor) type imager has pixels arranged in a uniform state at regular intervals. That is, for example, as shown in FIG. 7, in the pixel arrangement portion 91 of the solid-state imaging device 90, the horizontal pixel spacing is made constant and the vertical pixel spacing is also made constant so that each pixel is arranged in a matrix. Are arranged in succession. Here, the pixel is a portion where a light receiving element that receives incident light is disposed. In FIG. 7, for simplification of explanation, the horizontal and vertical directions are simplified with about a dozen pixels. However, in actuality, the pixels of the solid-state imaging device that obtain image signals are shown. The number is composed of hundreds of thousands of pixels to millions of pixels or more.

  A signal received by each pixel of such a solid-state imaging device is transferred and read out in a predetermined order, thereby obtaining one (one frame) imaging signal. Conventionally, the size of each pixel arranged in one solid-state imaging device is basically the same size.

JP 2000-56407 A JP 2004-64796 A JP-A-1-94777

By the way, the imaging signal obtained by imaging using such a solid-state imaging device has a problem that the periphery of one image becomes dark due to a problem such as a lens provided in the imaging apparatus. That is, when imaging is performed through a lens, when the angle θ formed with the optical axis at the center of the lens is determined, the peripheral light quantity is reduced by the cosine fourth law [cos ⁴ θ] due to the relationship between the incident angle and the illuminance. It is known to do. The decrease in the amount of ambient light leads to a decrease in the brightness of the periphery of the image obtained by imaging with the solid-state image sensor as it is, leading to a decrease in the quality of the captured image.
For example, when θ is 10 °, cos 10 ° ≈98 and cos θ = 0.94, and it is known that there is a corresponding decrease.

Conventionally, as a technique for correcting the decrease in the peripheral light amount with a solid-state imaging device, for example, as a so-called on-chip lens (OCL) configuration in which a minute lens is disposed in a light receiving portion of each pixel, a lens disposed in a peripheral pixel is used. There is a technique for ensuring the amount of received light at the periphery by shifting.
As another technique, a technique is known in which a lens system that guides light to a solid-state imaging device intentionally generates distortion, thereby reducing the area of a peripheral spot and increasing the amount of light.

Each of these technologies has a problem that optimization is difficult. In other words, with an on-chip lens configuration, it is very difficult to optimize the shift of the lens to increase the amount of light at the peripheral portion, and a scattered light beam is generated, which is insufficient as a method for uniformity of sensitivity.
Even when distortion is intentionally generated in the lens system, it is very difficult to match the distortion to the actual decrease in the amount of peripheral light according to the cosine fourth law described above, and optimization is difficult.

Further, as a technique for correcting the decrease in the amount of peripheral light with the pixel size of the solid-state imaging device, for example, those described in Patent Documents 1, 2, and 3 have been proposed.
Japanese Patent Application Laid-Open No. 2004-228561 describes that shading correction is performed by gradually reducing the size of the opening, which is the light receiving region of each pixel of the solid-state imaging device, from the peripheral part toward the center.
Patent Document 2 describes a configuration in which the pixel area gradually increases from the center toward the periphery as the pixel layout of the electronic imaging device.
In Patent Document 3, in order to correct pincushion-like image distortion due to lens distortion, pixels of the image sensor are arranged in a pincushion shape, and each area increases from the center to the periphery. Is described.

As described in each of these patent documents, by gradually increasing the pixel area from the center to the periphery, the amount of received light to each pixel in the peripheral part is increased from the central part, so that the peripheral part of the image Various ideas have already been proposed to compensate for the decrease in light intensity.
However, gradually increasing the area of each pixel as it goes from the center to the peripheral part means that the arrangement interval of each pixel is different between the horizontal direction and the vertical direction. The pixel interval of the output imaging signal is not constant.

  On the other hand, when an image signal obtained by imaging with an image sensor is used as an image signal for display on a display or the like, it is necessary to set the interval between pixels to a constant image signal. For this reason, if all the pixels on the image sensor are arranged at different intervals, a circuit for converting the image signals to a constant pixel interval is used to perform pixel position conversion such as interpolation for almost all pixel signals. Processing is required. Such a conversion circuit requires a large-scale conversion process, and there is a problem that the burden on the circuit system is very large.

  The present invention has been made in view of the above points, and an object of the present invention is to prevent a decrease in the amount of light at the peripheral portion of a captured image with a relatively simple configuration.

The imaging device of the present invention includes a light receiving element equidistant arrangement unit, a light receiving element expansion arrangement unit, and an output unit that outputs a light reception signal accumulated in the light receiving elements arranged in both arrangement units as an imaging signal.
The light receiving element equidistant arrangement portion is arranged with the light receiving elements arranged at a constant interval in the horizontal direction and at a constant interval in the vertical direction, and the area of the light receiving region of each light receiving element is equal to the first area. , And is arranged at substantially the center of the substrate constituting the image sensor.
The light receiving element expansion arrangement portion is arranged at a peripheral position that is symmetrical about the light receiving element equal interval arrangement portion. As the configuration of the light receiving element expansion arrangement portion, the light receiving elements are arranged at intervals wider than the constant interval in the light receiving element equal interval arrangement portion. The area was gradually larger than the area.

  Moreover, the imaging device of this invention is provided with the image pick-up element of this invention mentioned above. Then, among the imaging signals output from the imaging element, the imaging signal read from the light receiving element in the light receiving element equidistant arrangement portion and the imaging signal read from the light receiving element expansion arrangement portion are taken as an imaging signal having a constant pixel interval. The conversion part which converts into is provided. Furthermore, the imaging signal processing part which processes the imaging signal converted by the conversion part was provided.

According to the present invention, by arranging the light receiving element expansion arrangement portion in which the area of the light receiving region of the light receiving element is enlarged, the amount of received light increases in the peripheral portion of the image sensor, and the amount of peripheral light caused by the problem of the lens system is increased. The decrease can be corrected.
In this case, the signal read from the light receiving element equidistant arrangement section becomes a signal having a constant pixel interval, and the signal output from the output section can be processed in the same manner as the output image pickup signal of a normal image pickup element. Then, correction processing such as interpolation is required for signals output from the output unit after being read from the light receiving element enlargement / arrangement unit around the image sensor in accordance with the change in the interval. Therefore, the region where the correction process is performed on the output imaging signal is limited only to the peripheral light receiving element enlarged arrangement portion.

  According to the present invention, the area where correction processing is performed on the image pickup signal output from the output unit of the image pickup device is limited to only the peripheral light receiving element enlarged arrangement unit, and special processing is performed in the equally spaced arrangement unit. Is no longer necessary. Accordingly, it is possible to correct a decrease in the amount of peripheral light caused by the problem of the lens system with a configuration in which the burden on the processing system for converting the pixel interval is small.

It is explanatory drawing which shows the pixel arrangement example of the image pick-up element by the 1st Embodiment of this invention. 1 is a block diagram illustrating a configuration example of an imaging apparatus according to a first embodiment of the present invention. It is explanatory drawing which showed the concept of the aperture efficiency of a lens. It is explanatory drawing which showed the example which combined the optical system of the aspherical lens with the image pick-up element by the 1st Embodiment of this invention. It is explanatory drawing which showed the example of generation | occurrence | production of a distortion aberration. It is explanatory drawing which shows the pixel arrangement example of the image pick-up element by the 2nd Embodiment of this invention. It is explanatory drawing which showed the example of pixel arrangement | positioning of the conventional image sensor.

Hereinafter, examples of embodiments of the present invention will be described in the following order.
1. Configuration example of entire imaging apparatus according to first embodiment (FIG. 2)
2. Pixel arrangement example of the image sensor of the first embodiment (FIG. 1)
3. Description of conditions for determining the pixel size in the first embodiment (FIGS. 3 to 5)
4). Pixel arrangement example of the image sensor of the second embodiment (FIG. 6)
5). Modification of each embodiment

[1. Configuration example of entire imaging apparatus according to first embodiment (FIG. 2)]
The example of the first embodiment of the present invention is an imaging apparatus using a CCD (Charge Coupled Device) type imager as an imaging element. As the imaging apparatus, an imaging apparatus that performs various imaging such as a video camera that mainly captures moving images and a digital still camera that mainly captures still images can be applied.

FIG. 2 is a diagram illustrating an overview of the entire imaging apparatus according to the example of the present embodiment.
The image light obtained through the lens system 1 composed of a plurality of lenses is imaged on the pixel array unit 11 of the CCD image sensor 10 that is an image sensor. A diaphragm 2 is disposed in the middle of the lens system 1. The pixel configuration of the pixel array unit 11 will be described later.

  The light reception signal of each pixel obtained in the pixel array unit 11 of the CCD image sensor 10 is sequentially transferred by a register (not shown) in the image sensor 10 in synchronization with the drive signal supplied from the drive circuit 26. The output circuit 21 outputs the image signal. A driving clock is also supplied from the driving circuit 26 to the output circuit 21 and processed at a timing synchronized with the clock. The imaging signal output from the output circuit 21 is supplied to the delay circuit 22 and the interpolation circuit 23. In the interpolation circuit 23, interpolation processing for pixel position correction described later is performed. The delay circuit 22 is for synchronizing the timing with the interpolation processing in the interpolation circuit 23.

Then, the image pickup signal delayed by the delay circuit 22 and the image pickup signal interpolated by the interpolation circuit 23 are supplied to the changeover switch 24, and either one of the signals is selected and supplied to the image pickup signal processing unit 25. . Switching by the changeover switch 24 is performed in synchronization with a clock supplied from the drive circuit 26. Details of the processing state switched by the selector switch 24 will be described later.
The imaging signal processing unit 25 processes the supplied imaging signal and converts it into an image signal (video signal) in a predetermined format. The image signal converted by the imaging signal processing unit 25 is supplied to the recording system circuit 27 and recorded (stored) in various media. Alternatively, the image signal converted by the imaging signal processing unit 25 is supplied to the display system circuit 28 and displayed on a display or the like. Alternatively, the image signal converted by the imaging signal processing unit 25 is supplied to the output terminal unit 29 and output to the outside.

[2. Example of Pixel Arrangement of Image Sensor of First Embodiment (FIG. 1)]
Next, the pixel arrangement state of the pixel arrangement unit 11 of the CCD image sensor 10 will be described with reference to FIG. Note that the pixel array shown in FIG. 1 is shown in an emphasized manner for explaining the principle of the present embodiment, and the number of pixels is also shown in a simplified manner. In FIG. 1, the states of the two pixels are enlarged.
As shown in FIG. 1, in the pixel array unit 11 of the CCD image sensor 10, a predetermined number of light receiving portions of light receiving elements constituting each pixel are arranged vertically and horizontally. A transfer register is arranged beside the light receiving unit constituting each pixel, and signal charges obtained by receiving light from the light receiving unit are sent to the transfer register, and a drive circuit 26 (FIG. 2) is provided in the prepared transfer register. ) In synchronization with the clock supplied from () and supplied to the output circuit 21.

In the present embodiment, as shown in FIG. 1, the pixel array unit 11 is divided into a central pixel unit 11a and a peripheral pixel unit 11b. The center pixel portion 11a is a light receiving element equidistant arrangement portion as will be described. The peripheral pixel portion 11b is a light receiving element enlarged arrangement portion in which the light receiving elements are arranged at non-constant intervals.
In FIG. 1, the pixel area of the central pixel portion 11a is indicated by hatching, and the pixels arranged around the top, bottom, left, and right of the central pixel portion 11a are the peripheral pixel portion 11b. The peripheral pixel portion 11b is arranged in a symmetrical positional relationship when viewed from the central pixel portion 11a side, and is also arranged in a symmetrical positional relationship in the vertical direction. In this example, a range set from about 1/3 to about 1/2 of the length from the center position to the edge of the pixel array unit 11 is used as the center pixel unit 11a, and the light receiving elements are arranged at equal intervals. . The remaining area is a peripheral pixel portion 11b. The peripheral pixel portion 11b is a peripheral portion where the received light amount falls to a certain extent in terms of aperture efficiency, which will be described later.

  Each pixel in the center pixel portion 11a has a constant pixel arrangement interval in the horizontal direction and a constant interval in the vertical direction. The areas of the light receiving regions of the light receiving elements included in the pixels are also equal in the center pixel portion 11a. That is, as shown in FIG. 1, each pixel in the central pixel portion 11a has a vertical width v1 and a horizontal width h1 as the pixel size.

  In FIG. 1, one pixel in the central pixel portion 11a is shown enlarged. Of the width v1 in the vertical direction of one pixel in the central pixel portion 11a × the width h1 in the horizontal direction, the width v0 in the horizontal direction is the width of the transfer register 13. The remaining horizontal width h1 ′ and vertical width v1 determine the area of the light receiving region 12a of each pixel. As for the central pixel portion 11a, the pixel arrangement interval is constant, and the areas of the light receiving regions 12a of all the pixels in the central pixel portion 11a are equal.

The peripheral pixel unit 11b is configured to gradually increase the area of one pixel from the position in contact with the central pixel unit 11a toward the edge of the pixel array unit 11. Specifically, as shown in FIG. 1, the pixels in contact with the left and right ends of the central pixel portion 11a have a horizontal width that is wider than the width h1, and one pixel at a time from the pixel position. As the process proceeds, the horizontal widths h3 and h4 are set. Here, h1 <h2 <h3 <h4.
In addition, the pixels in contact with the upper and lower ends of the central pixel portion 11a have a width in the vertical direction that is wider than the width v1, and the width in the vertical direction increases as the pixel position advances from the pixel position. , Width v3. Here, v1 <v2 <v3.

In FIG. 1, one pixel in the peripheral pixel portion 11b is also shown enlarged. One pixel in the enlarged peripheral pixel portion 11b shown in FIG. 1 is a pixel at the left end, a pixel having a vertical width v4 × horizontal width h1, and a horizontal width v0. Is the width of the transfer register 13. The remaining horizontal width h4 ′ and vertical width v1 determine the area of the light receiving region 12b of the pixel.
Here, the width of the transfer register 13 is equal between the pixels in the central pixel portion 11a and the pixels in the peripheral pixel portion 11b.
The transfer register 13 shown in FIG. 1 is a vertical transfer register, and a horizontal transfer register (not shown) is connected to the end of the vertical transfer register. Is transferred.

  The signal charge accumulated in the light receiving region of the light receiving element of each pixel in the pixel array shown in FIG. 1 is read out as an imaging signal by the output circuit 21 shown in FIG. Here, since the image pickup signal of each pixel in the center pixel portion 11a is a signal in which pixels are arranged at a constant interval, it may be output as it is in synchronization with a clock with a fixed period from the drive circuit 26. For this reason, with respect to the changeover switch 24 shown in the configuration of the imaging apparatus in FIG. 2, the output of the delay circuit 23 is supplied to the imaging signal processing unit 25 as it is in the section where the signal of each pixel in the central pixel unit 11a is output. do it.

  On the other hand, since the imaging signals of the respective pixels in the peripheral pixel unit 11b are signals obtained with pixel arrangements having different intervals, the adjacent pixel signals of the interpolation circuit 22 are added at a ratio corresponding to the pixel position at that time. Then, it is converted into an imaging signal having the same pixel interval as that of the central pixel portion 11a. As the signal of the adjacent pixel, for example, the signal of the pixel adjacent in the horizontal direction and the signal of the pixel adjacent in the vertical direction are used. In the case of a pixel position where it is not necessary to use signals of pixels adjacent in the vertical direction, interpolation may be performed using only signals of pixels adjacent in the horizontal direction. The image pickup signal interpolated by the interpolation circuit 22 is selected by the changeover switch 24. As for the timing of the interpolation processing in the interpolation circuit 22 and the switching timing in the changeover switch 24, for example, non-uniformly spaced pixel clocks corresponding to the unequally spaced pixel arrangement in the peripheral pixel unit 11b are generated in the drive circuit 26. In synchronization with the pixel clock.

[3. Description of conditions for determining the pixel size in the first embodiment (FIGS. 3 to 5)]
Next, conditions for determining the pixel size of the imaging device having the central pixel portion 11a and the peripheral pixel portion 11b shown in FIG. 1 will be described.
As described above, the reason why the area of the light receiving region of the pixel in the peripheral pixel portion 11b is enlarged is to compensate for a decrease in the amount of light incident on the peripheral portion due to the influence of the lens system.
In the case of this example, the amount of light to the peripheral light receiving part is obtained based on the following equation.
Peripheral light quantity = Center light quantity × Aperture efficiency × cos ⁴ θ (1)
Here, θ is an incident angle of light passing through the lens system.

In the peripheral pixel unit 11b, the area of the light receiving region of each pixel is set to be enlarged so as to compensate for the shortage of the light amount obtained from the equation (1).
Specifically, for example, if the incident angle is 10 °,
cos10 ° ≈0.98
cos ⁴ θ = 0.94.
Furthermore, when the aperture efficiency is set to 90% and the expression (1) is obtained, the peripheral light amount is reduced to 85%.
Therefore, by increasing the area of the light receiving region at the corresponding pixel position by about 15% so as to compensate for the 15% decrease at the peripheral light amount of 85%, the received light amount can be made substantially equal to the central pixel. . The enlargement of about 15% is expressed by the size of the pixel. When both the vertical and horizontal directions are enlarged, the enlargement may be about 4% of one side. For example, if the size (interval) of one side of one pixel in the central pixel unit 11a is 1.55 μm, for example, the size of one side of one pixel is slightly over 1.60 μm in the peripheral pixel unit 11b. Can be dealt with by expanding to

Here, the aperture efficiency will be described with reference to FIG.
As shown in FIG. 3, when a lens and a diaphragm are arranged in front of the pixel array unit 11 of the CCD image sensor 10, the light incident on the pixel Pc at the center position of the pixel array unit 11 has an aperture amount S0. Let it be light. At this time, the light incident on the pixel Pe at the edge of the pixel array portion 11 becomes light having an aperture amount S1 that is narrower than the aperture amount S0. The ratio between the opening amount S0 and the opening amount S1 is the opening efficiency. As described above, when the opening amount S0 is 100%, the opening amount S1 when the incident angle θ is 10 ° is reduced to about 90%.
In the case of the present embodiment, not only the cos θ fourth law, which is generally said to be the cause of the decrease in the amount of light in the peripheral portion, but also the change in the amount of light due to the lens system, including the decrease in the amount of peripheral light due to the aperture efficiency. The correction is performed as follows. For this reason, it is possible to more accurately correct the amount of light at the peripheral portion.

Further, in the case of the present embodiment, the central pixel portion 11a of the pixel array portion 11 of the CCD image sensor 10 has pixels arranged at regular intervals in both the horizontal and vertical directions, and the amount of light changes. The configuration is such that no correction is performed. For this reason, the center pixel unit 11a of the pixel array unit 11 does not perform correction of the light amount decrease by the lens system, but the center pixel unit 11a is a region where the decrease in the light amount change is small, and correction is performed by increasing the amount of received light. Even if it is not, the decrease in the amount of light does not stand out from the captured image.
The boundary between the central pixel portion 11a and the peripheral pixel portion 11b shown in FIG. 1 is based on a position where the peripheral light amount obtained by the above-described equation (1) is lower than a predetermined value. It may be set.

  The CCD image sensor 10 of the present embodiment configured as described above can achieve a high effect even when combined with an optical system having an aspheric lens. That is, for example, as shown in FIG. 4, when a plurality of lenses 1 a to 1 f are provided as an optical system arranged on the front surface of the pixel array unit 11 of the CCD image sensor 10, the lenses 1 a to 1 f are included. One or a plurality of lenses may be provided with an aspheric lens. This aspherical lens is mainly for correcting spherical aberration, and the aberration is reduced with a small number of lenses. However, the aspheric lens corrects light emitted from one point on the optical axis, and does not correct light emitted from one point outside the optical axis. That is, no correction is made for the direction in which the peripheral light amount decreases.

  Therefore, as shown in FIG. 4, the peripheral light quantity correction by using the aspheric lens by combining the CCD image sensor 10 of the present embodiment with the imaging device using the lens systems 1a to 1f provided with the aspheric lens. Can be performed by the image sensor 10, and the correction effect is high. That is, the peripheral light amount correction processing with higher accuracy is performed by adding the peripheral light amount correction by the aspherical lens to the peripheral light amount obtained by the above-described formula (1) and expanding the light receiving area of the peripheral pixel. Can be done.

In addition, distortion may occur as a lens system included in the imaging apparatus. This distortion will be described with reference to FIG. 5. As the distortion, a barrel-shaped distortion occurs as shown in FIG. 5 (a), and a pincushion as shown in FIG. 5 (b). Mold distortion may occur.
Even when the CCD image sensor 10 of the present embodiment is combined with an image pickup apparatus using a lens system that generates distortion, the image sensor 10 can perform peripheral light amount correction by the distortion, and the correction effect is high. That is, by adding the peripheral light amount correction due to distortion to the peripheral light amount obtained by the above-described equation (1), and performing the process of enlarging the light receiving area of the peripheral pixels, a more accurate peripheral light amount correction process is performed. Yes. In the case of distortion, the pincushion distortion shown in FIG. 5B is generated in the direction in which the peripheral light amount decreases, so that the light receiving area of the peripheral pixel is further expanded. On the other hand, the barrel-shaped distortion shown in FIG. 5A is generated in the direction in which the peripheral light amount increases. Therefore, the light receiving area of the peripheral pixel is determined by the correction amount obtained by the expression (1). Will be reduced from.

[4. Example of Pixel Arrangement of Image Sensor of Second Embodiment (FIG. 6)]
Next, an example of the second embodiment of the present invention will be described with reference to FIG.
Also in the second embodiment, as in the example of the first embodiment described above, an imaging device using a CCD type imager as an imaging device is used, and an imaging device that performs various imaging can be applied. It is. For example, the configuration illustrated in FIG. 2 can be applied to the configuration of the entire imaging apparatus.

In the present embodiment, the pixel array section of the CCD image sensor 10 described in the first embodiment is the pixel array section 31 shown in FIG. Note that the pixel arrangement shown in FIG. 6 is shown in an emphasized manner for explaining the principle of the present embodiment, and the number of pixels is also shown in a simplified manner. In FIG. 6, the states of the two pixels are shown enlarged.
As shown in FIG. 6, in the pixel array part 31 of the CCD image sensor, a predetermined number of light receiving parts of the light receiving elements constituting the respective pixels are arranged. A transfer register is arranged beside the light receiving unit constituting each pixel, and signal charges obtained by receiving light from the light receiving unit are sent to the transfer register, and a drive circuit 26 (FIG. 2) is provided in the prepared transfer register. ) In synchronization with the clock supplied from () and supplied to the output circuit 21.

In the present embodiment, as shown in FIG. 6, the pixel array unit 31 is divided into a central pixel unit 31a and a peripheral pixel unit 31b. The center pixel portion 31a is a light receiving element equidistant arrangement portion. The peripheral pixel portion 31b is a light receiving element enlarged arrangement portion in which the light receiving elements are arranged at non-constant intervals.
In FIG. 6, the pixel area of the central pixel portion 11a is indicated by hatching, and the pixels arranged around the left and right of the central pixel portion 31a are the peripheral pixel portion 31b. The peripheral pixel portion 31b is arranged in a symmetrical position when viewed from the central pixel portion 31a side. In the case of this example, unlike the example of FIG. 1, the peripheral pixel portion 31b is not arranged in the vertical direction of the central pixel portion 31a. The central pixel portion 31a is a relatively large region in the central portion of the pixel array portion 31, and the peripheral pixel portion 31b is a relatively small region in the peripheral portion where the amount of received light falls to a certain extent in terms of aperture efficiency. is there.

  Each pixel in the central pixel portion 31a has a constant pixel arrangement interval in the horizontal direction and a constant interval in the vertical direction. The areas of the light receiving regions of the light receiving elements included in the pixels are also equal in the central pixel portion 31a. That is, as shown in FIG. 6, each pixel in the central pixel portion 31a has a vertical width v11 and a horizontal width h11 as the pixel size.

  FIG. 6 shows an enlarged view of one pixel in the central pixel portion 31a. Of the vertical width v11 × horizontal width h11 of one pixel in the central pixel portion 31a, the horizontal width v0 is the width of the transfer register 33. The remaining horizontal width h11 ′ and vertical width v11 determine the area of the light receiving region 32a of each pixel. As for the central pixel portion 31a, the pixel arrangement interval is constant, and the areas of the light receiving regions 32a of all the pixels in the central pixel portion 31a are equal.

The peripheral pixel unit 31b is configured to gradually increase the area of one pixel in the horizontal direction from the position in contact with the central pixel unit 31a toward the edge of the pixel array unit 31. Specifically, as shown in FIG. 1, for the pixels in contact with the left and right end portions of the central pixel portion 31a, the horizontal width is set to a width h12 wider than the width h11, and one pixel at a time from the pixel position. As the process proceeds, the horizontal widths h13 and h14 are set. Here, h11 <h12 <h13 <h14.
Further, in both the central pixel portion 31a and the peripheral pixel portion 31b, the vertical widths of the respective pixels are made equal as the width v11.

In FIG. 6, one pixel in the peripheral pixel portion 31b is also shown enlarged. One pixel in the enlarged peripheral pixel portion 31b shown in FIG. 6 is a pixel at the left end, is a pixel having a vertical width v11 × a horizontal width h14, and a horizontal width v0. Is the width of the transfer register 33. The remaining horizontal width h14 'and vertical width v11 determine the area of the light receiving region 32b of the pixel.
The width of the transfer register 33 is equal between the pixels in the central pixel portion 31a and the pixels in the peripheral pixel portion 31b.

  In the process of gradually increasing the area of the light receiving region in the pixel in the peripheral pixel portion 31b in the horizontal direction, the light amount at each pixel position is obtained from the peripheral light amount of the above-described equation (1), and the decrease in the peripheral light amount is reduced. The area to be corrected may be set. Therefore, the correction is performed in consideration of the aperture efficiency.

  Signal charges accumulated in the light receiving region of the light receiving element of each pixel in the pixel array shown in FIG. 6 are read out as an imaging signal by the output circuit 21 shown in FIG. 2, for example. Here, since the image pickup signal of each pixel in the center pixel portion 31a is a signal in which pixels are arranged at a constant interval, it may be output as it is in synchronization with a clock of a fixed cycle from the drive circuit 26. For this reason, with respect to the changeover switch 24 shown in the configuration of the imaging device in FIG. 2, the output of the delay circuit 23 is supplied to the imaging signal processing unit 25 as it is in the section where the signal of each pixel in the central pixel unit 31a is output. do it.

  On the other hand, since the imaging signals of the respective pixels in the peripheral pixel unit 31b are signals obtained with pixel arrangements having different intervals, the adjacent pixel signals are added by the interpolation circuit 22 at a ratio corresponding to the pixel position at that time. Then, it is converted into an imaging signal having the same pixel interval as that of the central pixel portion 31a. For example, only the signal of the pixel adjacent in the horizontal direction may be used as the signal of the adjacent pixel, but the signal of the pixel adjacent in the vertical direction is also used to improve the accuracy of the signal obtained by interpolation. May be. The image pickup signal interpolated by the interpolation circuit 22 is selected by the changeover switch 24. As for the timing of the interpolation processing in the interpolation circuit 22 and the switching timing in the changeover switch 24, for example, non-equally spaced pixel clocks corresponding to the unequally spaced pixel array in the peripheral pixel unit 11b are generated in the drive circuit 26. In synchronization with the pixel clock.

According to the second embodiment configured as described above, it is possible to correct a decrease in the amount of light of the peripheral pixels as in the image sensor of the first embodiment described above. In the case of the second embodiment shown in FIG. 6, only the light amount is reduced at the left and right ends, and correction is not performed at the upper and lower ends. Since the aspect ratio of the imaging surface (screen) is relatively long like 9:16, good correction is possible. In other words, the peripheral light intensity drop due to the lens system occurs by drawing a circle equidistant from the center position, so the light quantity reduction does not occur so much at the top and bottom edges, and a relatively large light quantity reduction occurs at the left and right edges. There is a high possibility of doing. Therefore, by correcting with the configuration shown in FIG. 6, the relatively large light amount decrease is corrected, and good imaging can be performed.
In the case of the present embodiment, since only the interval in which the pixels are arranged in the horizontal direction is changed, the pixel interval in the vertical direction is the same for all the pixels, and the configuration as an image sensor is simple accordingly. In addition, the processing system for processing the output image pickup signal of the image pickup device is simplified.

[5. Modification of each embodiment]
In the first and second embodiments described above, the example applied to the CCD image sensor has been described. However, the present invention may be applied to a solid-state imaging device having another configuration such as a CMOS imager. Of course. In other words, as long as the light receiving element constituting each pixel arranged in the solid-state image sensor can be arranged according to the principle shown in FIG. 1 or FIG. 6, it can be applied to various types of image sensors.

  In the second embodiment, the peripheral pixel portion is arranged only in the left-right direction of the central pixel portion, and the area of the light receiving region is enlarged in the peripheral pixel portion, but only in the vertical direction of the central pixel portion. A peripheral pixel portion may be arranged in the peripheral pixel portion, and the area of the light receiving region may be enlarged in the peripheral pixel portion. However, since a general imaging element has a horizontally long imaging region, the configuration in which the peripheral pixel portion is arranged only in the left-right direction of the central pixel portion described in the second embodiment is preferable.

  DESCRIPTION OF SYMBOLS 1 ... Lens system, 2 ... Diaphragm, 10 ... CCD image sensor, 11 ... Pixel arrangement part, 11a ... Center pixel part, 11b ... Peripheral pixel part, 12a, 12b ... Light-receiving area, 13 ... Transfer register part, 21 ... Output circuit , 22 ... delay circuit, 23 ... interpolation circuit, 24 ... changeover switch, 25 ... imaging signal processing unit, 26 ... drive circuit, 27 ... recording system circuit, 28 ... display system circuit, 29 ... output terminal unit, 31 ... pixel array Part, 31a ... center pixel part, 31b ... peripheral pixel part, 32a, 32b ... light receiving area, 33 ... transfer register part

Claims (10)

The light receiving elements are arranged at regular intervals in the horizontal direction and at regular intervals in the vertical direction, and the areas of the light receiving regions of the respective light receiving elements are equal to each other in the first area, and A light receiving element equidistantly arranged portion disposed substantially at the center;
Arranged at peripheral positions that are symmetric with respect to the light receiving element equidistant arrangement part, and arranged at a wider interval than the constant interval in the horizontal direction and / or the constant interval in the vertical direction in the light receiving element equidistant arrangement part. A light receiving element expansion arrangement portion in which the area of the light receiving region of each light receiving element is gradually larger than the first area as the distance from the light receiving element equal interval arrangement portion increases;
A light receiving signal accumulated in the light receiving elements arranged in the light receiving element equidistantly arranged portion and an output unit for outputting the light received signals accumulated in the light receiving elements arranged in the light receiving element enlarged arrangement portion as imaging signals; Image sensor. Increasing the area of the light receiving region of the light receiving element in the light receiving element expansion arrangement portion,
It is obtained by multiplying the central light quantity by the aperture efficiency of the lens system that transmits the light that reaches the light receiving element and cos ⁴ θ when the angle between the central optical axis of the lens system and the peripheral light is θ. The image pickup device according to claim 1, wherein the image pickup element is an area expansion corresponding to correcting a light amount decrease. The width of a register for transferring only a light receiving region of the light receiving element and transferring a light receiving signal accumulated in the light receiving element is not changed in response to an increase in an arrangement interval of the light receiving elements of the light receiving element expanding arrangement portion. Image sensor. The light receiving element expansion arrangement part is arranged at the upper, lower, left and right peripheral positions of the light receiving element equidistant arrangement part, and the area of the light receiving region of each light receiving element is separated from the light receiving element equidistant arrangement part in the vertical direction. The imaging device according to claim 1, wherein the area is gradually larger than the first area, and is gradually larger than the first area as the distance from the light receiving element equidistant arrangement portion is increased in the horizontal direction. The light receiving element expansion arrangement portion is arranged at the left and right peripheral positions of the light receiving element equal interval arrangement portion, and the area of the light receiving region of each light receiving element is increased as the distance from the light receiving element equal interval arrangement portion increases in the horizontal direction. Make the area gradually larger than the first area,
The imaging device according to claim 1, wherein the light receiving element enlarged arrangement portion is not arranged at upper and lower peripheral positions of the light receiving element equal interval arrangement portion. The light receiving elements are arranged at regular intervals in the horizontal direction and at regular intervals in the vertical direction, and the areas of the light receiving regions of the respective light receiving elements are equal to each other in the first area, and A light receiving element equidistantly arranged portion disposed substantially at the center;
Arranged at peripheral positions that are symmetric with respect to the light receiving element equidistant arrangement part, and arranged at a wider interval than the constant interval in the horizontal direction and / or the constant interval in the vertical direction in the light receiving element equidistant arrangement part. A light receiving element expansion arrangement portion in which the area of the light receiving region of each light receiving element is gradually larger than the first area as the distance from the light receiving element equal interval arrangement portion increases;
Imaging having a light receiving signal accumulated in a light receiving element arranged in the light receiving element equidistantly arranged portion and an output unit for outputting the light receiving signal accumulated in the light receiving element arranged in the light receiving element enlarged arrangement portion as an imaging signal Elements,
Among the imaging signals output from the output unit of the imaging element, an imaging signal read from the light receiving element in the light receiving element equidistantly arranged portion and an imaging signal read from the light receiving element enlarged arrangement portion are fixed pixels. A conversion unit for converting to an imaging signal at an interval;
An imaging apparatus comprising: an imaging signal processing unit that processes the imaging signal converted by the conversion unit. Increasing the area of the light receiving region of the light receiving element in the light receiving element enlarged arrangement portion of the image pickup element,
It is obtained by multiplying the central light quantity by the aperture efficiency of the lens system that transmits the light that reaches the light receiving element and cos ⁴ θ when the angle between the central optical axis of the lens system and the peripheral light is θ. The imaging apparatus according to claim 6, wherein the area is enlarged corresponding to correcting a light amount decrease. The imaging element expands only the light receiving area of the light receiving element in response to the increase in the arrangement interval of the light receiving elements in the light receiving element expanding arrangement portion, and does not change the width of the register for transferring the light receiving signal accumulated in the light receiving element. The imaging device according to claim 6. The light receiving element expansion arrangement portion of the imaging element is arranged at the upper, lower, left and right peripheral positions of the light receiving element equidistant arrangement portion, and the area of the light receiving area of each light receiving element is perpendicular to the light receiving element equidistant arrangement portion. The area gradually larger than the first area as the distance from the first area increases, and the area gradually larger than the first area as the distance from the light receiving element equidistantly arranged portion in the horizontal direction increases. Imaging device. The image pickup element and the light receiving element expansion arrangement portion are arranged at the left and right peripheral positions of the light receiving element equal interval arrangement portion, and the areas of the light receiving regions of the respective light receiving elements are separated from the light receiving element equal interval arrangement portion in the horizontal direction. And gradually increasing the area to be larger than the first area,
The imaging apparatus according to claim 6, wherein the light receiving element enlarged arrangement portion is not arranged at upper and lower peripheral positions of the light receiving element equal interval arrangement portion.

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