JP2004056407A - Solid-state electronic imaging device and solid-state electronic imaging unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent shading based on signal electric charges obtained from an aperture with light incident thereon. <P>SOLUTION: The apertures 4 are formed on vertical transfer lines 3 adjacent to photodiodes 2 in a honeycomb CCD1 wherein each photodiode 2 is placed on an even number row as to an odd number column, and on an odd number row as to an even number column. The sizes of the apertures 4 are increased from the center of the CCD1 toward the peripheral parts. When a lens is placed in front of the CCD1, although the luminous quantity made incident on the peripheral parts of the CCD1 differs from the luminous quantity made incident on the center on the basis of the curved face of the lens, since the sizes of the apertures 4 differ between the center part and the peripheral parts, the quantity of signal electric charges stored in each aperture 4 is kept constant. Thus, the shading is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
【Technical field】
The present invention relates to a solid-state electronic imaging device and a solid-state electronic imaging apparatus.
[0002]
BACKGROUND OF THE INVENTION
A solid-state electronic image pickup device such as a CCD is used in a digital still camera or the like. An imaging lens is provided in front of the solid-state electronic imaging element. Since the imaging lens is spherical, the photoelectric conversion element positioned at the center of the imaging lens has higher light incidence efficiency than the photoelectric conversion element positioned at the periphery of the imaging lens. The output signal level from the photoelectric conversion element positioned at the center of the imaging lens increases, and the output signal level from the photoelectric conversion element positioned at the periphery of the imaging lens decreases. For this reason, so-called shading may occur.
[0003]
DISCLOSURE OF THE INVENTION
One type of solid-state electronic image sensor is called a honeycomb array. In the honeycomb arrangement, photoelectric conversion elements are arranged in even rows for odd columns, odd rows for even columns, or odd rows for odd columns, and even rows for even columns. It is. In order to effectively use the region between the photoelectric conversion elements in such a honeycomb arrangement, it is considered to form an opening in the region.
[0004]
So-called shading may also occur in an image represented by image data obtained by light entering the aperture.
[0005]
An object of the present invention is to prevent shading based on a signal charge obtained when light enters the aperture.
[0006]
The solid-state electronic image pickup device according to the first invention is arranged in even rows for odd columns, arranged in odd rows for even columns, or arranged in odd rows for odd columns, and even rows for even columns. A large number of photoelectric conversion elements arranged in a light-shielding area adjacent to the photoelectric conversion elements, located adjacent to the photoelectric conversion elements, and increasing in size from the periphery of the solid-state electronic image sensor toward the center. The first signal charge accumulated in the photoelectric conversion element and the second signal charge generated when light enters from the opening are respectively transferred in the row direction. A vertical transfer path is provided.
[0007]
According to the first invention, the photoelectric conversion elements have a so-called honeycomb arrangement, in which odd columns are arranged in even rows, even columns are arranged in odd rows, or odd columns are arranged in odd rows. , Even columns are arranged in even rows. A light-shielded vertical transfer path is formed adjacent to the photoelectric conversion element. On this vertical transfer path, an opening is formed at a position adjacent to the photoelectric conversion element. The size of the opening decreases from the periphery toward the center. For this reason, the amount of signal charge obtained based on the opening increases in the peripheral part and decreases in the central part.
[0008]
When the imaging lens is arranged in front of the solid-state electronic imaging device, the amount of signal charge obtained based on the opening located in the center is increased, and obtained based on the opening located in the periphery of the imaging lens. The amount of signal charge that is generated is reduced. However, according to the present invention, as described above, since the size of the opening decreases from the periphery toward the center, the amount of signal charge obtained based on the opening varies depending on the position. Is prevented. It is possible to prevent so-called shading from occurring due to the signal charge obtained based on the opening.
[0009]
According to a second aspect of the present invention, there is provided a solid-state electronic image pickup device comprising: the first image data obtained based on the first solid-state image pickup element and the first signal charge output from the vertical transfer path of the solid-state electronic image pickup element; , And a correction device for correcting using the second image data obtained based on the second signal charge.
[0010]
According to the second invention, the first image data obtained based on the first signal charge accumulated in the photoelectric conversion element is corrected by the second image data obtained by light entering the aperture. Is done. A high-quality image can be represented. In particular, since the second image data obtained by the light entering the opening prevents the occurrence of shading as described above, a higher quality image can be obtained.
[0011]
A solid-state electronic imaging device according to a third aspect of the invention generates the main pixel based on the above-described solid-state electronic imaging device, the first signal charge output from the vertical transfer path of the solid-state electronic imaging device, and the second pixel. A pixel generation device that generates an interpolation pixel based on the signal charge of the pixel, and an image generation device that generates an image between the main pixel and the interpolation pixel generated by the pixel generation means. And
[0012]
According to the third aspect, the main pixel is generated based on the first signal charge, and the interpolation pixel is generated based on the second signal charge. The generated interpolation pixel has high image quality because shading is prevented as described above.
[0013]
[Explanation of Examples]
FIG. 1 shows an embodiment of the present invention and is a schematic diagram of a CCD.
[0014]
The CCD 1 is provided with a light receiving region 5 on substantially the entire surface.
[0015]
In the light receiving region 5, a large number of octagonal photodiodes 2 are provided in the column direction and the row direction. The photodiodes 2 are arranged in even rows in odd columns and in odd rows in even columns. However, the photodiodes 2 may be arranged in odd rows in odd columns and in even rows in even columns.
[0016]
Adjacent to the right side of the photodiode 2 is formed a vertical transfer path 3 for transferring signal charges in the vertical direction (row direction). The vertical transfer path 3 is shielded from light.
[0017]
An opening 4 is formed in the vertical transfer path 3 at a position on the right side of the photodiode 2. As will be described in detail later, the size of the opening 4 increases from the center to the periphery of the light receiving region 5 (in FIG. 1, the size of the opening 4 is constant for convenience. See FIG. 2). ). Light enters from these openings 4.
[0018]
At the lower end of the light receiving area 5, a horizontal transfer path 6 for transferring signal charges in the horizontal direction is provided.
[0019]
An amplifier circuit 7 is provided on the output side (left side) of the horizontal transfer path 6.
[0020]
The signal charge accumulated in the photodiode 2 is shifted to the vertical transfer path 3 when a shift pulse is applied to the photodiode 2. The signal charge shifted to the vertical transfer path 3 is transferred in the vertical direction when a vertical transfer pulse is applied to the vertical transfer path 3. The signal charge is input from the vertical transfer path 3 to the horizontal transfer path 6 and transferred in the horizontal direction. The signal charge is amplified by the amplifier circuit 7 and output from the CCD 1 as a video signal.
[0021]
Further, when light enters the opening 4 of the light receiving region 50, signal charges are generated in the vertical transfer path 3. The generated signal charge is transferred in the vertical direction when a vertical transfer pulse is applied to the vertical transfer path 3. Similar to the signal charge stored in the photodiode 2 described above, the signal charge is output as a video signal via the vertical transfer path 3, the horizontal transfer path 6 and the amplifier circuit 7.
[0022]
FIG. 2 is a schematic diagram in which the photodiode 2 is omitted from the CCD 1.
[0023]
As described above, the size of the opening 4 gradually increases from the center to the periphery. For this reason, the light incident efficiency is higher in the peripheral opening 4 than in the central opening 4.
[0024]
In a digital still camera, when the CCD 1 is used as an imaging device, an imaging lens is often provided in front of the CCD 1. Since the imaging lens is spherical, the amount of light transmitted through the central lens portion is larger than the amount of light transmitted through the peripheral lens portion. In this embodiment, as described above, since the size of the opening 4 gradually increases from the center to the periphery, the amount of light incident on the opening 4 is substantially constant regardless of the position of the opening 4. . It is possible to prevent shading from occurring when an image is generated using a signal charge obtained by light entering the opening 4.
[0025]
In the embodiment described above, the shape of the photodiode 2 is an octagon, but it is not limited to an octagon, and may be other shapes. In addition, the opening 4 is a circle for convenience, but it is needless to say that the opening 4 is not limited to a circle but may be an octagon or other shapes.
[0026]
FIG. 3 is a block diagram showing an electrical configuration of the digital still camera.
[0027]
The overall operation of the digital still camera is controlled by the CPU 19.
[0028]
The digital still camera includes shutters 20 including a shutter release button, a mode setting switch, and the like. Various command signals output from the shutters 20 are input to the CPU 19.
[0029]
The digital still camera includes a strobe 11 for strobe photography. The light emission of the strobe 11 is controlled by the drive circuit 12.
[0030]
Further, a clock signal, other control signals, and the like are output from the drive circuit 12 and are supplied to the zoom lens 13, the mechanical shutter and diaphragm 14, the CCD 1, and the analog signal processing circuit 15.
[0031]
Light representing the subject image is collected by the zoom lens 13. The light that has passed through the shutter and the diaphragm 14 forms an image on the light receiving area 5 of the CCD 1. When an imaging mode is set by a mode setting switch included in the switches 20, a video signal representing a subject image is output from the CCD 1 and input to the analog signal processing circuit 15. In the analog signal processing circuit 15, predetermined analog processing such as correlated double sampling is performed. The video signal output from the analog signal processing circuit 15 is converted into digital image data in the analog / digital conversion circuit 16.
[0032]
The digital image data converted by the analog / digital conversion circuit 16 is input to the digital signal processing circuit 17. In the digital signal processing circuit 17, predetermined digital signal processing such as gamma correction and white balance adjustment is performed. The image data output from the digital signal processing circuit 17 is given to the image display device 22, whereby the subject image obtained by imaging is displayed on the display screen of the image display device 22. When an external display device or the like is connected to the communication interface 23, the image data is also given to the external display device via the communication interface 23. The subject image is displayed on the display screen of the external display device.
[0033]
When the shutter release button is pressed, the image data output from the digital signal processing circuit 17 is temporarily stored in the memory 18 as described above. Image data is read from the memory 18 and applied to the memory card interface 21. By connecting the memory card to the memory card interface 21, image data is recorded on the memory card.
[0034]
FIG. 4 is a time chart when a video signal is output from the CCD 1.
[0035]
First, the mechanical shutter and the mechanical shutter of the diaphragm 14 are opened. When the imaging mode is set using the mode setting switch at time t1, the CCD 1 is driven and the subject is imaged at a constant period Δt. Image data representing a subject image is output from the CCD 1 at a certain period Δt (so-called electronic shutter). At time t2, the electronic shutter operation is stopped and exposure to the CCD 1 is started. When the mechanical shutter is closed at time t3, exposure to the CCD 1 is completed (exposure time: t2 to t3). During this exposure time, signal charges are accumulated in the photodiode 2 and the opening 4 of the vertical transfer path 3, respectively.
[0036]
When the exposure of the CCD 1 is completed, a horizontal transfer pulse is applied to the horizontal transfer path 6 from time t3 to t4, and unnecessary charges remaining in the horizontal transfer path 6 are swept out. Thereafter, a vertical transfer pulse is applied to the vertical transfer path 3 from time t5. The signal charge accumulated in the opening 4 portion of the vertical transfer path 3 is transferred in the vertical direction. At time t6, a horizontal transfer pulse is applied to the horizontal transfer path 6, and the signal charge accumulated in the opening 4 portion of the vertical transfer path 3 is output as a video signal until time t7. As described above, the size of the opening 4 gradually increases from the central portion to the peripheral portion. Therefore, even if the incident light amount differs between the central portion and the peripheral portion of the zoom lens 13 as described above. The amount of signal charge (video signal level) obtained for each opening 4 is substantially constant. Shading can be prevented from occurring.
[0037]
At time t8, a shift pulse is applied to the photodiode 2. The signal charge accumulated in the photodiode 2 is shifted to the vertical transfer path 3. A vertical transfer pulse is applied to the vertical transfer path 3. Then, the signal charge shifted to the vertical transfer path 3 is transferred in the vertical direction and applied to the horizontal transfer path 6. At time t9, a horizontal transfer pulse is applied to the horizontal transfer path 6, and the signal charge accumulated in the photodiode 2 is output as a video signal until time t10.
[0038]
The video signal (image data) obtained based on the signal charge accumulated in the photodiode 2 in this way and the video signal (image data) obtained based on the signal charge accumulated in the opening 4 portion of the vertical transfer path 3 are obtained. ) Can be used to obtain an image with a wide dynamic range as follows. The output of the analog / digital conversion circuit 16 is assumed to be 8 bits.
[0039]
FIG. 5 shows the incident light quantity to the photodiode 2 -output image data Y (output of the analog / digital conversion circuit 16) characteristic, and FIG. 6 shows the image data Y obtained based on the signal charges accumulated in the photodiode 2. And the characteristics of the image data Z after gamma correction are shown.
[0040]
The output image data Y increases in proportion to the amount of incident light until the amount of incident light on the photodiode 2 reaches the amount of light X. When the incident light quantity exceeds the light quantity X, the output image data Y is saturated (at a level of 255). As described above, the digital signal processing circuit 17 performs gamma correction on the output image data Y according to the gamma correction curve shown in FIG. By performing gamma correction, image data Z after gamma correction is obtained according to the level of output image data Y.
[0041]
FIG. 7 shows the incident light quantity to the opening 4 -output image data y (output of the analog / digital conversion circuit 16) characteristics, and FIG. 8 shows the image data y obtained based on the signal charge accumulated in the opening 4 portion. And the characteristics of the image data z after gamma correction are shown.
[0042]
As in the case of the photodiode 2, the output image data y increases in proportion to the amount of incident light until the amount of light incident on the opening 4 reaches the amount of light x. When the incident light quantity exceeds the light quantity x, the output image data y is saturated (level 63). Gamma correction is performed on the output image data y according to the gamma correction curve shown in FIG. By performing gamma correction, image data z after gamma correction is obtained according to the level of output image data y. In the case of the opening 4, since the area of the opening 4 is smaller than the area of the photodiode 2, the image data Y obtained based on the signal charge accumulated in the photodiode 2 is saturated with a light amount x greater than the light amount X that is saturated. To do. Image data y representing a level finer than the image data Y obtained based on the photodiode 2 is obtained. Therefore, image data z after gamma correction representing a finer level than the image data Z after gamma correction obtained based on the photodiode 2 is obtained.
[0043]
When the image data representing the image of one frame is generated from the image data Z after the first gamma correction and the image data z after the second gamma correction obtained in this way according to Equation 1, the generated image data The image represented by I has a wide dynamic range.
[0044]
I = (Z + z) / (255 + 63) × 255 Formula 1
[0045]
Further, by using the signal charge obtained based on the opening 4, an interpolation pixel between pixels (main pixels) represented by the signal charge accumulated in the photodiode 2 can be generated in the digital signal processing circuit 17. Needless to say. The digital signal processing circuit 17 may perform an addressing operation so that the generated interpolation pixel is displayed between the pixels represented by the signal charges accumulated in the photodiode 2.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a CCD.
FIG. 2 is a schematic diagram of a CCD in which a photodiode is omitted.
FIG. 3 is a block diagram showing an electrical configuration of a digital still camera.
FIG. 4 is a time chart when a video signal is output from a CCD.
FIG. 5 shows the characteristics of incident light quantity and output image data.
FIG. 6 shows gamma correction characteristics.
FIG. 7 shows the characteristics of incident light quantity and output image data.
FIG. 8 shows gamma correction characteristics.
[Explanation of symbols]
1 CCD
2 Photodiode 3 Vertical transfer path 4 Aperture 5 Light receiving area 6 Horizontal transfer path 17 Digital signal processing circuit 19 CPU

Claims (3)

A number of photoelectric conversion elements arranged in even rows for odd columns, arranged in odd rows for even columns, or arranged in odd rows for odd columns, and arranged in even rows for even columns;
An opening is formed adjacent to the photoelectric conversion element so as to be shielded from light, and is located adjacent to the photoelectric conversion element and decreases in size from the periphery of the solid-state electronic imaging element toward the center. And a vertical transfer path for transferring the first signal charge accumulated in the photoelectric conversion element and the second signal charge generated when light enters from the opening in the row direction,
A solid-state electronic imaging device. The first image data obtained based on the first signal charge output from the vertical transfer path of the solid-state electronic image pickup device according to claim 1 and the solid-state electronic image pickup device is converted into the second signal charge. Corrector using the second image data obtained based on
A solid-state electronic imaging device. The solid-state electronic image pickup device according to claim 1,
A pixel generation device that generates the main pixel based on the first signal charge output from the vertical transfer path of the solid-state electronic image sensor and generates an interpolated pixel based on the second signal charge, and the pixel An image generation device for generating an image between the main pixel and the interpolation pixel generated by the generation unit;
A solid-state electronic imaging device.

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