JP2007104178A - Imaging element and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging element capable of generating an image signal having an excellent balance between a luminance signal and a color signal, while improving sensitivity in the imaging element provided with plural types of color filters and luminance filters, and to provide an imaging device. <P>SOLUTION: The imaging element having a plurality of pixels arrayed into a two-dimensional matrix shape is provided with plural types of color pixels in which plural types of color filters are arranged corresponding to a plurality of the pixels, a plurality of white pixels in which the luminance filters are arranged corresponding to a plurality of the pixels, and a transfer for transferring signal electric-charges read out from the color pixels or the white pixels. The size of the transfer for transferring the signal electric-charges read out from the white pixels is made larger than that of the transfer for transferring the signal electric-charges read out from the color pixels. Alternatively, a size of a photoelectric converter provided to the white pixel is made smaller than that of a photoelectric converter provided to the color pixel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging element and an imaging apparatus, and more particularly to an imaging element and an imaging apparatus that improve the S / N of an image.

  2. Description of the Related Art In recent years, imaging devices such as digital cameras and digital video cameras are required to have high-resolution and high-definition performance of image pickup devices typified by CCD (Charge Coupled Device) as multi-functionality and high image quality progress. As a result, higher pixels and higher density are accelerating.

  On the other hand, in an image sensor with a high pixel density, the photoelectric conversion amount per pixel decreases due to a decrease in the area per pixel, that is, the sensitivity decreases and the signal level of the image signal decreases, and S / N The ratio (Signal / Noise) is lowered. The reduction in the S / N ratio has a great influence on the image reproducibility and the image quality. Therefore, it is necessary to improve the sensitivity in order to realize high-quality image formation. In the field of image sensors, various techniques for improving sensitivity have been studied.

For example, in a solid-state imaging device having photodiodes arranged vertically and horizontally, a luminance filter Y having a high light transmittance, such as a transparent filter and a white filter, is arranged on each photodiode arranged in a checkered pattern. Other photodiodes have a filter configuration in which conventional color filters R, G, and B are arranged, and signal charges generated by the photodiode in which a high-sensitivity luminance filter Y is arranged are used as luminance signals. There is a technique for improving the luminance resolution that is not influenced by the color information of the subject when used (for example, see Patent Document 1).
JP 2003-318375 A (see paragraph number 0014, etc.)

  As described above, various techniques for an image sensor for improving sensitivity have been studied.

  In the solid-state imaging device disclosed in Patent Document 1, in addition to the conventional color filters R, G, and B, a luminance filter Y with high light transmittance is arranged to obtain a luminance signal with high sensitivity. ing. However, when the pixel structure of the white pixel and the color pixel is made the same, the difference in sensitivity between the white pixel and the color pixel becomes very large. Here, the photodiode in which the luminance filter Y is disposed is referred to as a white pixel, and the photodiode in which the color filters R, G, and B are disposed is referred to as a color pixel. Specifically, this will be described with reference to FIG. FIG. 4A is a diagram illustrating a filter configuration of the solid-state imaging device 50 disclosed in Patent Document 1. In FIG. FIG. 4B is a schematic diagram illustrating an outline of a pixel structure of the solid-state imaging device 50 in which a broken line region in FIG.

  As shown in FIG. 4A, the solid-state imaging device 50 includes a plurality of pixels 501 arranged in a two-dimensional matrix. Each pixel 501 generates a signal charge by photoelectrically converting a subject light image. A plurality of photodiodes 502 are provided. In the photodiode 502, luminance filters Y are arranged in a checkered pattern in addition to the color transmission filters of R (red) light, G (green) light, and B (blue) light.

  As shown in FIG. 4B, the pixel structure of the solid-state imaging device 50 having such a filter configuration is a photodiode PD-R in which color filters R, G, and B are arranged in each pixel 501. , PD-G, PD-B, and a photodiode PD-Y in which a luminance filter Y is disposed are provided. Further, a vertical transfer path 505 for transferring signal charges generated by the photodiodes PD-R, PD-G, PD-B, and PD-Y in the vertical direction is provided between the columns. As shown in FIG. 4B, the photodiodes PD-R, PD-G, and PD-B and the photodiode PD-Y have the same size structure. However, the light transmittances of the color filters R, G, B and the luminance filter Y are greatly different, and the light transmittance of the luminance filter is about four times larger than that of the normal color filter. That is, although the transmittance of the filter is greatly different, the difference in sensitivity between the white pixel and the color pixel becomes very large because the photodiodes have the same size structure.

  When the solid-state imaging device having such a pixel structure is subjected to exposure control under the same conditions, the signal charge generated in the white pixel is saturated, and the signal charge generated in the color pixel becomes very small, An image signal with a good balance between the luminance signal and the color signal cannot be obtained, and it becomes difficult to form a high-quality image.

  The present invention has been made in view of the above problems, and in an imaging device including a color pixel in which a plurality of types of color filters are arranged and a white pixel in which a luminance filter is arranged, the sensitivity is improved, and white An object of the present invention is to provide an imaging device and an imaging apparatus capable of generating an image signal having a good balance between luminance signals and color signals obtained from pixels and color pixels.

  The object is achieved by the invention described in any one of (1) to (7) below.

(1) An imaging device that is arranged in a two-dimensional matrix and has a plurality of pixels that photoelectrically convert a subject optical image to generate signal charges,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A color pixel transfer unit that transfers the signal charges read from the color pixels;
A white pixel transfer unit that transfers the signal charges read from the white pixels,
The size of the white pixel transfer unit is larger than the size of the color pixel transfer unit.

(2) An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels,
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel.

(3) An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A color pixel transfer unit that transfers the signal charges read from the color pixels;
A white pixel transfer unit that transfers the signal charges read from the white pixels,
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel,
And,
The image sensor according to (1) or (2), wherein the size of the white pixel transfer unit is larger than the size of the color pixel transfer unit.

(4) An image sensor that is arranged in a two-dimensional matrix and has a plurality of pixels that photoelectrically convert a subject optical image to generate signal charges,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A white pixel driving unit that is provided adjacent to the white pixel and controls reading of the signal charge generated by the white pixel;
A color pixel driving unit that is provided adjacent to the color pixel and controls reading of signal charges generated by the color pixel;
The size of the white pixel driving unit is larger than the size of the color pixel driving unit.

(5) An imaging device that is arranged in a two-dimensional matrix and has a plurality of pixels that photoelectrically convert a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A white pixel driving unit that is provided adjacent to the white pixel and controls reading of the signal charge generated by the white pixel;
A color pixel driving unit that is provided adjacent to the color pixel and controls reading of signal charges generated by the color pixel;
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel,
And,
The size of the white pixel driving unit is larger than the size of the color pixel driving unit.

  (6) The imaging device according to any one of (1) to (5), wherein the pixel has a square shape.

  (7) An image pickup apparatus comprising the image pickup device according to any one of (1) to (6) above.

  In the inventions described in (1), (2), and (3) above, the size of the transfer unit that transfers the signal charges read from the white pixels is set to the transfer that transfers the signal charges read from the color pixels. The structure is larger than the size of the part. In other words, by increasing the transfer path for transferring signal charges generated by white pixels with high sensitivity and a large amount of signal, it is possible to prevent transfer defects such as overexposure without saturating the signal charges in the transfer path. Will be able to.

  In addition, the size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel. That is, by reducing the photoelectric conversion unit of the white pixel having high sensitivity, the sensitivity difference between the white pixel and the color pixel is reduced, and an image signal having a good balance between the luminance signal and the color signal can be generated. .

  In the inventions described in the above (4) and (5), for example, in the CMOS type solid-state imaging device, the size of the driving unit that performs read control of the signal charge generated in the white pixel is generated in the color pixel. The structure is larger than the size of the drive unit that performs signal charge readout control. That is, it is possible to prevent overexposure without saturating the signal charge in the drive unit by increasing the drive unit that performs readout control of the signal charge generated by the white pixel having a high sensitivity and a large signal amount. It becomes like.

  In the invention described in (7) above, the image pickup device includes the image pickup device described in any one of (1) to (6) above, thereby forming a high-quality image with a good S / N ratio. To be able to.

Hereinafter, embodiments of an imaging device and an imaging apparatus according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol shows the same or an equivalent part, and the overlapping description is abbreviate | omitted.
The numerical values indicating the size of the photodiode, vertical transfer path, drive unit, etc. used in the following description are only examples, and can be appropriately changed according to the size of the image sensor, the number of pixels, and the like. Of course.
[Embodiment 1] The configuration of a CCD area sensor according to Embodiment 1 of an image sensor according to the present invention will be described with reference to FIG. FIG. 1A is a diagram showing a filter configuration of a CCD area sensor 60 according to the present invention. FIG. 1B is a schematic diagram showing an outline of the pixel structure of the CCD area sensor 60 in which the area of the broken line in FIG. Although FIG. 1A shows only the range of 8 rows and 8 columns, the arrangement shown in FIG. 1A is actually repeated.

  As shown in FIG. 1A, a CCD area sensor 60 (hereinafter abbreviated as “CCD 60”) has a plurality of pixels 601 arranged in a two-dimensional matrix, and each pixel 601 receives a subject light image. A plurality of photodiodes 602 corresponding to the photoelectric conversion unit in the present invention are provided by photoelectric conversion to generate signal charges. The photodiodes 602 provided in the odd-numbered color pixels are provided with color-transmitting color filters of R (red) light, G (green) light, B (blue) light, and G (green) light. A luminance filter Y is arranged in the photodiode 602 provided in the white pixel, and the color filters R, G, B and the luminance filter Y are repeated every two columns. The brightness filter Y corresponds to an ND filter, a transparent filter, a white filter, a gray filter, etc., but a configuration in which light is directly incident on the photodiode surface without providing anything on the surface of the photodiode 602 is also provided with a transparent filter. It corresponds to the configuration.

  Next, the pixel structure of the CCD 60 having such a filter configuration will be described. As shown in FIG. 1B, each pixel 601 includes a photodiode PD-R (not shown), PD-G, PD-B, and luminance filter Y in which color filters R, G, and B are arranged. A photodiode PD-Y is provided. Further, between each column, a vertical transfer path C606 for transferring signal charges generated by the photodiodes PD-R, PD-G, and PD-B in the vertical direction, and a signal charge generated by the photodiode PD-Y. Is provided in the vertical transfer path Y605. As described above, the vertical transfer path C606 and the vertical transfer path Y605 function as a color pixel transfer unit and a white pixel transfer unit in the image sensor according to the present invention, respectively.

  Here, the structure of the photodiode 602 will be described. In the present invention, the size of the light receiving surface of each of the photodiodes PD-R, PD-G, and PD-B in which the color filters R, G, and B having low light transmittance are arranged is shown in FIG. As shown in FIG. 2, the size of the light receiving surface of the photodiode PD-Y on which the luminance filter Y having a high light transmittance is arranged is 2.5 μm × 2.0 μm, and the size is 2.5 μm × 1.5 μm. In this way, the size of the light receiving surface of the photodiode PD-Y of the white pixel with high sensitivity is made larger than the size of the light receiving surface of the photodiodes PD-R, PD-G, and PD-B of the color pixels with low sensitivity. By reducing the size, the sensitivity difference between the white pixel and the color pixel is reduced, and an image signal having a good balance between the luminance signal and the color signal can be generated.

  Here, the sensitivity of white pixels and color pixels of the CCD 60 will be described with reference to FIG. FIG. 2A is a relationship diagram illustrating an example of the relationship between the amount of light incident on each pixel of the conventional solid-state imaging device 50 and the amount of signal charge. FIG. 2B is a relationship diagram showing an example of the relationship between the amount of light incident on each pixel of the CCD 60 and the amount of signal charge in the present invention.

  In the conventional solid-state imaging device 50, as described above, the photodiodes PD-R, PD-G, PD-B provided in the color pixels and the photodiode PD-Y provided in the white pixels have the same size. 2A, the difference in sensitivity between the white pixel and the color pixel is very large as shown in FIG. 2A, and the amount of signal charge generated in each pixel is about four times as large. There is. On the other hand, in the CCD 60 of the present invention, the size of the light receiving surface of the photodiode PD-Y provided in the white pixel is set to the size of the light receiving surface of the photodiodes PD-R, PD-G, and PD-B provided in the color pixel. As shown in FIG. 2B, the sensitivity difference between the white pixel and the color pixel is reduced, and the amount of signal charge generated in each pixel is about three times as shown in FIG. It can confirm that it has shrunk to.

  Next, the structure of the vertical transfer path C606 and the vertical transfer path Y605 of the CCD 60 will be described. In the present invention, the width of the vertical transfer path C606 for transferring the signal charges generated by the photodiodes PD-R, PD-G, and PD-B in the vertical direction is set to 0, for example, as shown in FIG. The width of the vertical transfer path C606 of the photodiode PD-Y is 1.0 μm. In this way, by increasing the width of the vertical transfer path Y605 for transferring the signal charge generated by the photodiode PD-Y provided in the white pixel having a high sensitivity and a large signal amount, the signal charge in the transfer path is increased. It becomes possible to prevent overexposure without saturation.

  Here, the transfer capacity of the vertical transfer path of the CCD 60 will be described with reference to FIG. FIG. 3 is a relationship diagram showing an example of the relationship between the transfer path width and transfer capacity of the vertical transfer path. As shown in FIG. 3, it can be confirmed that the number of transferable electrons (transfer capacity) increases as the width of the vertical transfer path becomes wider.

  Thus, in the image sensor according to the present invention, the size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel. That is, by reducing the photoelectric conversion unit of the white pixel having high sensitivity, the sensitivity difference between the white pixel and the color pixel is reduced, and an image signal having a good balance between the luminance signal and the color signal can be generated. .

Further, the size of the transfer unit that transfers the signal charge read from the white pixel is larger than the size of the transfer unit that transfers the signal charge read from the color pixel. That is, by increasing the transfer path for transferring the signal charge generated by the white pixel having a high sensitivity and a large signal amount, it is possible to prevent overexposure without causing the signal charge to be saturated in the transfer path. become.
[Embodiment 2] The configuration of a CMOS solid-state image pickup device according to Embodiment 2 of the image pickup device according to the present invention will be described with reference to FIG. FIG. 5A is a diagram showing a filter configuration of the CMOS solid-state imaging device 70 according to the present invention. FIG. 5B is a schematic diagram showing an outline of the pixel structure of the CMOS solid-state imaging device 70 in which the broken line region in FIG. 5A is enlarged. Although FIG. 5A shows only the range of 8 rows and 8 columns, the arrangement shown in FIG. 5A is actually repeated.

  As shown in FIG. 5A, a CMOS type solid-state imaging device 70 (hereinafter abbreviated as a CMOS sensor 70) has a plurality of pixels 701 arranged in a two-dimensional matrix. A plurality of photodiodes 702 corresponding to the photoelectric conversion unit in the present invention are provided by photoelectrically converting a subject light image to generate signal charges. The photodiodes 702 provided in the odd-numbered color pixels are provided with color-transmitting color filters of R (red) light, G (green) light, B (blue) light, and G (green) light. A luminance filter Y is arranged in the photodiode 702 provided in the white pixel, and the color filters R, G, B and the luminance filter Y are repeated every two columns. The brightness filter Y corresponds to an ND filter, a transparent filter, a white filter, a gray filter, etc., but a configuration in which light is directly incident on the photodiode surface without providing anything on the surface of the photodiode 602 is also provided with a transparent filter. It corresponds to the configuration.

  Next, the pixel structure of the CMOS sensor 70 having such a filter configuration will be described. As shown in FIG. 5B, each pixel 701 includes a photodiode PD-R (not shown), PD-G, PD-B, and luminance filter Y in which color filters R, G, and B are arranged. A photodiode PD-Y is provided. Further, between each row, a driving unit G706 that performs reading control of the signal charge generated by the photodiode PD-G, a driving unit B707 that performs reading control of the signal charge generated by the photodiode PD-B, and the photodiode. A drive unit Y705 is provided that performs read control of the signal charges generated by the PD-Y. Although not shown in the figure, there is of course also provided a drive unit R that performs read control of the signal charge generated by the photodiode PD-R. In this manner, the drive units R, G706, B707, and the drive unit Y705 function as a color pixel drive unit and a white pixel drive unit in the image sensor according to the present invention, respectively.

  Here, the structure of the photodiode 702 will be described. In the present invention, the sizes of the light receiving surfaces of the photodiodes PD-R (not shown), PD-B and PD-G in which the color filters R, B and G having low light transmittance are arranged are shown in FIG. As shown in b), the size of the light receiving surface of the photodiode PD-Y, which is 2.1 μm × 2.5 μm and 2.0 μm × 2.5 μm, respectively, and in which the luminance filter Y having a high light transmittance is arranged, is set. 1.5 μm × 2.5 μm. In this way, the size of the light receiving surface of the photodiode PD-Y of the white pixel with high sensitivity is made larger than the size of the light receiving surface of the photodiodes PD-R, PD-G, and PD-B of the color pixels with low sensitivity. By reducing the size, the sensitivity difference between the white pixel and the color pixel is reduced, and an image signal having a good balance between the luminance signal and the color signal can be generated.

  Next, the structure of the drive unit R (not shown), the drive unit G706, the drive unit B707, and the drive unit Y705 of the CMOS sensor 70 will be described. In the present invention, a driver R (not shown), a driver B707, and a driver G706 that perform readout control of signal charges generated by the photodiodes PD-R (not shown), PD-B, and PD-G. 5b, for example, as shown in FIG. 5 (b), 0.4 μm × 2.5 μm and 0.5 μm × 2.5 μm, respectively, and the readout control of the signal charge generated by the photodiode PD-Y is performed. The size of the drive unit Y705 to be performed is 1.0 μm × 2.5 μm. In this way, by increasing the size of the drive unit Y705 that performs the read control of the signal charge generated by the photodiode PD-Y provided in the white pixel having a high sensitivity and a large signal amount, the signal in the drive unit is increased. Overexposure and the like can be prevented without charge saturation.

  Here, the configuration of the drive unit of the CMOS sensor 70 will be described with reference to FIG. FIG. 6 is a circuit diagram illustrating an example of a schematic configuration of the drive unit. As shown in FIG. 6, the drive unit includes a read transistor Tr1 that reads the signal charge generated by the photodiode PD1, a reset transistor Tr2 that resets the read signal charge, and an output transistor Tr3 that outputs the read signal charge. And a row selection transistor Tr4 and the like, and performs a drive control operation for reading the signal charge generated by the photodiode PD1 to a transfer path (not shown). In the present invention, the sizes of the transistors Tr1 to Tr4 that constitute the drive unit Y705 that controls the readout of the signal charges generated by the photodiode PD-Y provided in the white pixel having a high sensitivity and a large signal amount. , A photo diode photodiode PD-R (not shown) provided in a low-sensitivity color pixel, a drive unit R (not shown) that performs read control of signal charges generated by PD-B and PD-G, drive It is larger than the transistors Tr1 to Tr4 constituting the part B707 and the driving part G706. Therefore, it becomes possible to drive without saturating the signal charge having a large charge amount.

  Thus, in the image sensor according to the present invention, the size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel. That is, by reducing the photoelectric conversion unit of the white pixel having high sensitivity, the sensitivity difference between the white pixel and the color pixel is reduced, and an image signal having a good balance between the luminance signal and the color signal can be generated. .

Further, the size of the drive unit that performs the read control of the signal charge generated in the white pixel is larger than the size of the drive unit that performs the read control of the signal charge generated in the color pixel. That is, it is possible to prevent overexposure without saturating the signal charge in the drive unit by increasing the drive unit that performs readout control of the signal charge generated by the white pixel having a high sensitivity and a large signal amount. It becomes like.
[Embodiment 3] As a specific embodiment of the image pickup apparatus according to the present invention, a digital camera is typical, but a mobile phone with a camera, a digital video camera, and the like are also included. The appearance of a digital camera that is one of the representative embodiments of the imaging apparatus according to the present invention will be described with reference to FIG. FIG. 7A is a side view of the digital camera 1 according to the present invention, and FIG. 7B is a rear view. As shown in FIG. 7A, the digital camera 1 includes a camera body 2 and a lens unit 3.

  The lens unit 3 includes a photographing lens having a macro zoom (not shown), a diaphragm, a shutter, and the like.

  The camera main body 2 includes an LCD monitor 211 formed of an LCD (Liquid Crystal Display), an EVF (Electronic View Finder) 210, and external connection terminals for connecting the digital camera 1 to a personal computer (not shown). The image signal captured by the CCD area sensor 60 described later is subjected to predetermined signal processing, image display on the LCD monitor 211 and EVF 210, and image recording on a recording medium such as a memory card 277 described later, Alternatively, processing such as image transfer to a personal computer is performed.

  As shown in FIG. 7A, a built-in flash 212 that is hopped up when necessary is provided on the upper surface of the camera body 2.

  Further, as shown in FIG. 7B, an LCD for displaying a photographed image, reproducing a recorded image, or displaying a GUI such as a menu screen or various statuses is displayed at a substantially central portion on the back of the camera body 2. A monitor 211 and an EVF 210 are provided.

  As shown in FIG. 7B, a shutter setting button 203 for setting the operation mode of the digital camera 1 is provided near the shutter button 201 on the upper surface of the camera body 2. . The operation mode of the digital camera 1 set by the mode setting dial 203 includes “still image mode”, “moving image mode”, “reproduction mode”, and the like.

  For example, the still image mode is a mode in which a still image is shot from the shooting standby state (live view state) to the shooting through the exposure control process, and the moving image mode is the CCD in the shooting standby state (live view state). In this mode, moving image shooting is performed based on the moving image signal read from the area sensor 60. The playback mode is a mode in which the captured image recorded on the memory card 277 is played back and displayed on the LCD monitor 211 or EVF 210.

  Further, as shown in FIG. 7B, a main switch 202 and a digital zoom button 209 for changing the zoom magnification of digital zoom are provided near the main switch 202 at the upper back of the camera body 2. ing.

  Further, as shown in FIG. 7B, a menu button 207 for displaying a menu on the LCD monitor 211 and an image on the LCD monitor 211 are displayed near the menu button 207 at the lower back of the camera body 2. Is provided with a quick view button 208.

  Further, a selection / determination button 206 for performing various settings is provided at a substantially central portion on the back surface of the camera body 2. The selection / determination button 206 includes a jog dial (cross key) 204 for selecting various settings and a determination button 205 for confirming the setting selected by the jog dial (cross key) 204.

  Next, the control system of the digital camera 1 will be described with reference to FIG. FIG. 8 is a block diagram of a control system of the digital camera 1 according to the present invention. In FIG. 8, the same members as those shown in FIG.

  In the digital camera 1 of the present invention, either the CCD 60 described in the above [Embodiment 1] or the CMOS sensor 70 described in [Embodiment 2] can be used as an image sensor. A control system of the digital camera 1 provided with the CCD 60 will be described.

  The timing generator 246 generates a drive control signal for the CCD 60 based on a reference clock transmitted from a reference clock generator 271 described later. The drive control signal generated by the timing generator 246 includes, for example, an integration start / end timing signal for controlling the exposure start and end timings in the CCD 60, and a readout control signal (horizontal synchronization signal, vertical synchronization) of the light reception signal of each pixel. Clock signals such as signals, transfer signals, and the like. When these clock signals are supplied to the CCD 60, the CCD 60 performs drive control corresponding to each clock signal.

  The signal processing circuit 242 includes a CDS circuit 243 and an AGC circuit 244, and a predetermined process is performed on the image signal via these components. Hereinafter, a predetermined process for the image signal performed by the signal processing circuit 242 will be described.

  A CDS (Correlated Double Sampling) circuit 243 corrects the black level by reducing noise generated when the image signal read from the CCD 60 is read or by performing an OB clamping operation.

  An AGC (automatic gain control) circuit 244 adjusts the gain of the image signal processed by the CDS circuit 243.

  The A / D converter 245 converts each pixel signal constituting the image signal input from the AGC circuit 244 into a digital signal. The A / D converter 245 converts each pixel signal of an analog signal into, for example, a 14-bit digital signal based on the A / D conversion clock input from the reference clock generation unit 271.

  Here, the output signal waveform of the CDS circuit 243 will be described with reference to FIG. FIG. 9A is a schematic diagram showing an output signal waveform of the CDS circuit 243 when the above-described conventional solid-state imaging device 50 or the like is used. FIG. 9B is a schematic diagram showing an output signal waveform of the CDS circuit 243 in the present invention. 9 (a) and 9 (b) are both one-line CDS circuits in which signal charges generated by, for example, the color pixel photodiode PD-G and the white pixel photodiode PD-Y are alternately output. 243 shows the output signal waveform.

  The output signal waveform of the CDS circuit 243 when the conventional solid-state imaging device 50 is used has a large amplitude of the signal waveform as shown in FIG. 9A due to a large sensitivity difference between the color pixel and the white pixel. It has become a thing. As a result, due to the response characteristics of the CDS circuit 243, the signal waveform becomes a large waveform, and the signal level of the white pixel shown in the A portion and the signal level of the color pixel shown in the B portion are both less in the flat portion. . Originally, the signal waveform is ideally a rectangular wave, as indicated by a broken line in FIG. 9A, but due to the response characteristic of the CDS circuit 243, the waveform becomes distorted as the amplitude of the signal waveform increases. As described above, when the A / D converter 245 performs the A / D conversion on the signal that has become larger and has less flat portions, it is difficult to perform a highly accurate and stable A / D conversion operation. It is.

  On the other hand, in the present invention, since either one of the CCD 60 or the CMOS sensor 70 described above in which the sensitivity difference between the color pixel and the white pixel is reduced is provided, the output signal waveform of the CDS circuit 243 is as shown in FIG. As shown in b), the amplitude of the signal waveform is smaller than that in FIG. 9A, and the signal level of the white pixel shown in part A and the signal level of the color pixel shown in part B are both large in the flat part. It has become. Accordingly, it is possible to perform a highly accurate and stable A / D conversion operation.

  In this way, the image signal read by the CCD 60 is subjected to predetermined processing by the signal processing circuit 242 and converted into a digital image signal. The digitized image signal is captured by the image processing CPU 261 and subjected to predetermined processing.

  The image processing CPU 261 is composed of a microcomputer, and comprehensively controls image signal processing operations performed by the digital camera 1. In the following, processing for a digital image signal performed by the image processing CPU 261 will be described.

  First, the image signal captured by the image processing CPU 261 is written into the image memory 275 in synchronization with the reading of the image signal output from the CCD 60. That is, the digital image signal used for the processing performed by the image processing CPU 261 is once recorded in the image memory 275, taken out from the image memory 275, and used for processing in each block.

  As shown in FIG. 8, the image processing CPU 261 includes, for example, a black level correction unit 263, a pixel interpolation unit 264, a resolution conversion unit 265, a white balance control unit 266, a gamma correction unit 267, a matrix calculation unit 268, a shading correction unit 269, The image processing unit 262 includes an image compression unit 270 and the like, a reference clock generation unit 271, and the like. The image processing unit 262 performs known image signal processing on the digital image signal extracted from the image memory 275. Then, the digital image signal that has been subjected to the predetermined processing in these parts is stored in the image memory 275 again.

  The reference clock generation unit 271 is a circuit that generates a reference clock used for driving control of the digital camera 1 and supplies the reference clock to each circuit. Specific examples of the reference clock in the present invention include a reference clock used for the timing generator 246, an A / D conversion clock used for the A / D converter 245, and the like. Generate a clock.

  Next, the LCD monitor 211 performs display of the image signal captured by the CCD 60 and GUI display.

  The LCD drive circuit 279 includes a buffer memory (VRAM) that temporarily stores an image signal read from the image memory 275 by the image processing CPU 261, and displays the image signal on the LCD monitor 211 as a field image.

  Next, the camera control CPU 291 is composed of a microcomputer, and controls the drive of each member of the camera body 2 and the lens unit 3 sequentially based on switch signals generated by switch operations of a switch group 295 to be described later. The overall shooting operation of 1 is controlled.

  As described above, in the digital camera 1, the image processing CPU 261 performs the signal processing as described above on the image signal captured from the CCD 60, and records the image signal subjected to these processing in the image memory 275. .

  The digital camera 1 according to the present invention records the image signal captured from the CCD 60 under the mode set by the mode setting dial 203 in the image memory 275 or displays it on the LCD monitor 211 or EVF 210.

  In a shooting standby state (for example, a state in which the mode setting dial 203 is set to “still image mode”), an image signal is captured by the image processing CPU 261 from the CCD 60 via the signal processing circuit 242 at a predetermined interval such as every 1/30 seconds. ing. As described above, the captured image signal is subjected to predetermined signal processing at a portion from the black level correction unit 263 to the shading correction unit 269 of the image processing unit 262 in the image processing CPU 261, and then as a digital image signal. It is recorded in the image memory 275. Then, the image signal recorded in the image memory 275 is read out, and the read image signal is displayed on the LCD monitor 211 or EVF 210 as a field image via the LCD drive circuit 279 or EVF drive circuit 280.

  Further, at the time of image recording, the image signal is compressed by the image compression unit 270 of the image processing unit 262 in the image processing CPU 261 to obtain an image of the set recording resolution, and the obtained compressed image is a memory card driver 276. To the memory card 277.

In the reproduction mode (the state in which “reproduction mode” is set by the mode setting dial 203), the image signal read from the memory card 277 is subjected to predetermined signal processing by the image processing CPU 261, and is driven by the LCD drive circuit 279 or EVF drive. The switch group 295 in FIG. 8 includes the shutter button 201, the main switch 202, the mode setting dial 203, the selection / decision button 206, the menu button 207, Switches corresponding to the quick view button 208, the digital zoom button 209, and the like.

  As described above, the imaging apparatus according to the present invention can form a high-quality image with a good S / N ratio by providing an imaging device with improved sensitivity and a balanced luminance signal and color signal. I can do it. Furthermore, since an image signal in which the luminance signal and the color signal are balanced is output from the image sensor, complicated processing such as correction is not required in subsequent signal processing, and the processing can be simplified. It becomes like.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be changed or improved as appropriate. For example, in the CCD 60 described in the first embodiment, R (red) light, G (green) light, B (blue) light, and G (green) light are provided to the photodiodes 602 provided in the odd-numbered color pixels. In the photodiodes 602 provided in the even-numbered white pixels, the luminance filter Y is arranged, and the color filters R, G, B and the luminance filter Y are repeated every two columns. As shown in FIG. 10, white pixels in which the luminance filter Y is arranged are provided in a checkered pattern, and color pixels in which the color filters R, G, and B are arranged are provided in a line-sequential manner. Alternatively, the configuration may be a Bayer array. Note that the arrows in the figure indicate the readout direction of the signal charge generated by the photodiode 602.

It is a schematic diagram which shows schematic structure of the CCD area sensor by Embodiment 1 of this invention. It is a relationship figure which shows one example of the relationship between the incident light quantity to the various pixels of the CCD area sensor by Embodiment 1 of this invention, and an output. FIG. 6 is a relationship diagram illustrating an example of a relationship between a transfer path width and a transfer capacity of a vertical transfer path of the CCD area sensor according to the first embodiment of the present invention. It is a schematic diagram which shows schematic structure of the conventional solid-state image sensor. It is a schematic diagram which shows schematic structure of the CMOS sensor by Embodiment 2 of this invention. It is a circuit diagram which shows schematic structure of the drive part of the CMOS sensor by Embodiment 2 of this invention. It is a schematic diagram which shows the external appearance of the digital camera by Embodiment 3 of this invention. It is a circuit block block diagram which shows schematic structure of the circuit block of the digital camera by Embodiment 3 of this invention. It is a schematic diagram which shows the CDS output signal of the digital camera by Embodiment 3 of this invention. It is a schematic diagram which shows schematic structure of the CCD area sensor of a Bayer arrangement by Embodiment 1 of this invention.

Explanation of symbols

1 Digital Camera 2 Camera Body 201 Shutter Button 202 Main Switch 203 Mode Setting Dial 204 Jog Dial (Cross Key)
205 OK button 206 Select / OK button 207 Menu button 208 Quick view button 209 Digital zoom button 210 Electronic viewfinder (EVF)
211 LCD monitor 212 Built-in flash 242 Signal processing circuit 243 CDS circuit 244 AGC circuit 245 A / D converter 246 Timing generator 247 Aperture / shutter drive circuit 248 Focus / zoom motor drive circuit 261 Image processing CPU
262 Image processing unit 263 Black level correction unit 264 Pixel complementation unit 265 Resolution conversion unit 266 White balance control unit 267 Gamma correction unit 268 Matrix calculation unit 269 Shading correction unit 270 Image compression unit 271 Reference clock generation unit 275 Image memory 276 Memory card driver 277 Memory card 278 External communication I / F
279 LCD drive circuit 280 EVF drive circuit 291 Camera control CPU
292 Flash control circuit 295 Switch group (shutter button, etc.)
3 Lens unit 351 Focus / zoom motor 352 Aperture 50 Solid-state imaging device 60 CCD area sensor 501, 601, 701 Pixel 502, 602, 702 Photodiode 505 Vertical transfer path 605 Vertical transfer path Y
606 Vertical transfer path C
70 CMOS sensor 705 Drive unit Y
706 Drive G
707 Drive B

Claims (7)

An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A color pixel transfer unit that transfers the signal charges read from the color pixels;
A white pixel transfer unit that transfers the signal charges read from the white pixels,
The size of the white pixel transfer unit is larger than the size of the color pixel transfer unit. An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels,
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel. An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A color pixel transfer unit that transfers the signal charges read from the color pixels;
A white pixel transfer unit that transfers the signal charges read from the white pixels,
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel,
And,
The image pickup device according to claim 1, wherein a size of the white pixel transfer unit is larger than a size of the color pixel transfer unit. An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A white pixel driving unit that is provided adjacent to the white pixel and controls reading of the signal charge generated by the white pixel;
A color pixel driving unit that is provided adjacent to the color pixel and controls reading of signal charges generated by the color pixel;
The size of the white pixel driving unit is larger than the size of the color pixel driving unit. An image sensor having a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge,
A plurality of types of color pixels in which a plurality of types of color filters are arranged corresponding to the plurality of pixels;
A plurality of white pixels in which luminance filters are arranged corresponding to the plurality of pixels;
A white pixel driving unit that is provided adjacent to the white pixel and controls reading of the signal charge generated by the white pixel;
A color pixel driving unit that is provided adjacent to the color pixel and controls reading of signal charges generated by the color pixel;
The size of the photoelectric conversion unit provided in the white pixel is smaller than the size of the photoelectric conversion unit provided in the color pixel,
And,
The size of the white pixel driving unit is larger than the size of the color pixel driving unit. The image sensor according to claim 1, wherein the pixel has a square shape. An imaging apparatus comprising the imaging device according to claim 1.

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