JP2007020118A - Photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photographing apparatus capable of preventing a color change due to color mixture at horizontal transfer. <P>SOLUTION: The imaging apparatus includes a CCD image sensor, which has a line memory 12 located between vertical CCDs and a horizontal CCD 13. When the setting value of the ISO sensitivity is greater than a prescribed value, first signal electric charges of G (Green) among signal electric charges of R (Red), G (Green), B (Blue) by one line transferred from the vertical CCDs to the line memory 12 are outputted to the horizontal CCD 13 and horizontally transferred up to a floating diffusion amplifier (FDA) 14. Then the signal electric charges of R are outputted to horizontal CCD 13 and horizontally transferred up to the floating diffusion amplifier (FDA) 14, and thereafter the signal electric charges of B are outputted to horizontal CCD 13 and horizontally transferred up to the floating diffusion amplifier (FDA) 14. The color separation transfer is carried out by each line to prevent a color change due to color mixture. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus equipped with a solid-state imaging device.

  2. Description of the Related Art A CCD image sensor is known as a solid-state imaging device mounted on a photographing device such as a digital camera or a camera-equipped mobile phone. The CCD image sensor is two-dimensionally arranged in a matrix, and is provided for each of a plurality of photoelectric conversion elements (photodiodes) that convert incident light into signal charges corresponding to the amount of light, and for each vertical column of photoelectric conversion elements. A plurality of vertical CCDs that vertically transfer signal charges from the photoelectric conversion elements, and a horizontal CCD that horizontally transfers signal charges for one line (row) transferred from the vertical CCDs. The corresponding imaging signal is output.

In order to obtain a color image, a single-plate CCD image sensor using RGB (or CMY) color filters is generally used. Signal charges corresponding to R, G, and B colors are transferred to the output circuit by the vertical CCD and horizontal CCD. Various methods for transferring the signal charge have been proposed particularly from the viewpoint of speeding up (see, for example, Patent Documents 1 and 2).
JP 2002-112119 A JP 2004-28966 A

  In the single-plate CCD image sensor as described above, color mixing due to mixing of signal charges of respective colors during transfer becomes a problem. In a vertical CCD, color separation can be performed by interline readout. In this case, in the horizontal CCD, for example, “GGGG...” And “RBRB.

  However, since R and B have a large degree of color modulation, a color change is likely to occur when colors are mixed due to transfer defects. In particular, when the photographing apparatus is set to the high sensitivity mode, the influence of color mixture becomes significant.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus that can prevent color change due to color mixing during horizontal transfer.

  In order to achieve the above object, a photographing apparatus of the present invention is provided for each of a plurality of types of photoelectric conversion elements that photoelectrically convert light of a specific color and each vertical column of the photoelectric conversion elements, and from each of the photoelectric conversion elements A plurality of vertical CCDs that vertically transfer the signal charges, a line memory that temporarily accumulates and outputs signal charges for one line transferred from the vertical CCDs, and a horizontal transfer of the signal charges output from the line memories In a photographing apparatus equipped with a solid-state image sensor having a horizontal CCD that outputs and an output circuit that outputs an image signal corresponding to the signal charge transferred by the horizontal CCD, the signal charge stored in the line memory is classified for each color. And a control means for performing color separation transfer for horizontal transfer after output to the horizontal CCD.

  The ISO sensitivity setting means and a signal amplifying means for amplifying the imaging signal output from the output circuit based on the ISO sensitivity set by the setting means, and the color separation transfer is performed with the ISO sensitivity. It is preferable to operate when the set value is larger than a predetermined value. The photoelectric conversion elements are preferably two-dimensionally arranged in a honeycomb shape.

  The imaging apparatus according to the present invention causes the solid-state imaging device to perform color separation transfer in which the signal charges accumulated in the line memory are output to the horizontal CCD for each color and then transferred horizontally, thereby preventing color change due to color mixing. it can.

  In FIG. 1, a CCD image sensor 2 is provided for each vertical column of a plurality of photoelectric conversion elements (PD) 10 and PDs 10 that convert incident light into signal charges corresponding to the amount of light, and store them. A plurality of vertical CCDs (VCCDs) 11 that vertically transfer the signal charges of one line, a line memory (LM) 12 that temporarily accumulates and outputs (transfers) signal charges for one line transferred from the VCCD 11, and outputs from the LM 12 A horizontal CCD (HCCD) 13 for horizontally transferring the signal charge to be transferred, and a floating diffusion amplifier (FDA) 14 as an output circuit for converting the signal charge transferred by the HCCD 13 into a signal voltage (imaging signal) and outputting it. .

  The PD 10 is formed so that its outer shape is an octagon, and is two-dimensionally arranged in a honeycomb shape at a predetermined pitch. A color filter and a microlens (not shown) are stacked on the PD 10, and the PD 10 photoelectrically converts light of a specific color. Note that RGB notation in the figure indicates the arrangement of red, green, and blue by color filters, PD10 with R added red light, PD10 with G added green light, and B added. The PD 10 photoelectrically converts blue light. This color arrangement is a so-called Bayer arrangement inclined 45 ° with respect to the transfer direction. In this color arrangement, the signal charges accumulated in the R and B PDs 10 and the signal charges accumulated in the G PDs 10 are transferred by different VCCDs 11.

  The VCCD 11 transfers signal charges (reads out all pixels) by four-phase driving by vertical transfer pulses supplied from the CCD driver 40 (see FIG. 2). As indicated by dotted arrows in the figure, the VCCD 11 receives signal charges from the PDs 10 via transfer gates (not shown), and sequentially transfers the signal charges from the top to the bottom in the figure.

  The LM 12 is connected to the last stage of the VCCD 11 and accumulates signal charges for one line transferred from each VCCD 11. The LM 12 selectively outputs a signal charge to the HCCD 13 according to the color from the signal charge for one line by the line memory pulse supplied from the CCD driver 40.

  The HCCD 13 is connected to the LM 12 in parallel. Based on the horizontal transfer pulse supplied from the timing generator 30 (see FIG. 2), the HCCD 13 shifts the signal charge received from the LM 12 from the right side to the left side in the drawing as indicated by the dotted arrow. Transfer serially to FDA14.

  In FIG. 2, a digital camera 20 on which the CCD image sensor 2 is mounted as a solid-state imaging device is controlled overall by a CPU (control means) 22 via a bus 21. The digital camera 20 includes an optical system 23, an analog signal processing circuit 24, an A / D conversion circuit (A / D) 25, a buffer memory 26, a compression / decompression processing circuit 27, a YC processing circuit 28, a photometry / ranging circuit 29, and It consists of a timing generator (TG) 30 and the like.

  The optical system 23 includes an imaging lens 31 including a focus lens and a zoom lens and a diaphragm 32. A lens motor 33 and an iris motor 34 are connected to the imaging lens 31 and the diaphragm 32. These motors 33 and 34 are stepping motors, and their operations are controlled by drive pulses transmitted from a motor driver 35 connected to the photometry / ranging circuit 29.

  The lens motor 33 moves the zoom lens of the imaging lens 31 to the wide side or the tele side. Further, the focus lens of the image pickup lens 31 is moved in accordance with zooming magnification of the zoom lens, etc., and the focus adjustment is performed so that the shooting conditions are optimized. The iris motor 34 operates the aperture 32 to adjust exposure. The focus adjustment and the exposure adjustment by the motors 33 and 34 are performed based on the photometry / distance measurement result of the subject by the photometry / distance measurement circuit 29.

  The analog signal processing circuit 24 includes a signal amplification circuit (signal amplification means) and a correlated double sampling circuit, and performs analog signal processing such as amplification and correlated double sampling on the imaging signal output from the CCD image sensor 2. And output to A / D 25. The signal amplification circuit in the analog signal processing circuit 24 amplifies the imaging signal based on a set value of ISO sensitivity described later.

  The A / D 25 converts the analog signal input from the analog signal processing circuit 24 into a digital image signal and outputs the digital image signal to the buffer memory 26. The buffer memory 26 temporarily stores the image signal digitized by the A / D 25.

  The compression / decompression processing circuit 27 compresses the image data stored in the buffer memory 26 by a predetermined compression method, for example, the JPEG method, and decompresses the compressed image data to restore the original data. The image data compressed by the compression / decompression processing circuit 27 is stored in the memory card 37 via the card I / F 36.

  The YC processing circuit 28 converts the image data stored in the buffer memory 26 into a luminance signal Y and color difference signals Cr and Cb. The image data YC converted by the YC processing circuit 28 is converted into an analog composite signal by the LCD driver 38 and displayed on the LCD 39 as a through image.

  The photometry / ranging circuit 29 detects the luminance of the subject and the distance to the subject, and drives and controls the motor driver 35 so as to obtain an appropriate focal length and exposure amount based on the detection result.

  The timing generator (TG) 30 is connected to the CCD driver 40 together with the analog signal processing circuit 24 and the A / D 25 described above. The TG 30 transmits timing signals (clock pulses) to these units. Based on the timing signal transmitted from the TG 30, the CCD driver 40 supplies the CCD image sensor 2 with a vertical transfer pulse for driving the VCCD 11, a line memory pulse for driving the LM 12, and the like. Further, the TG 30 supplies a horizontal transfer pulse for driving the HCCD 13 to the CCD image sensor 2.

  A release button 41, an operation unit 42, and an EEPROM 43 are connected to the CPU 22. The release button 41 is a two-stage push switch. When the release button 41 is lightly pressed (half-pressed), various photographing preparation processes such as automatic exposure adjustment (AE) and automatic focus adjustment (AF) are performed. In this state, when the release button 41 is pressed once more (fully pressed), the imaging signal for one screen subjected to the imaging preparation processing is converted into image data, and then the above-described YC processing and compression processing are performed. And stored in the memory card 37.

  The operation unit (setting means) 42 is a zoom operation button for zooming the zoom lens to the wide side or the tele side, a menu button operated when displaying a menu screen on the LCD 39 or determining a selection, and a menu screen And a mode dial for switching the operation mode of the digital camera 20 (still image shooting mode, moving image shooting mode, playback mode, setting mode, etc.). The operation unit 42 can set the ISO sensitivity in the setting mode during the operation mode. The CPU 22 operates each unit of the digital camera 20 based on the release button 41 and the operation input signal from the operation unit 42 described above.

  In the EEPROM 43, various control programs and setting information are recorded. The CPU 22 reads out this information from the EEPROM 43 to the built-in RAM, and executes various processes.

  Next, the operation of the digital camera 20 having the above configuration will be described. First, when shooting a subject with the digital camera 20, the power switch of the operation unit 42 is operated to turn on the digital camera 20, and the mode dial is operated to set the still image shooting mode or the moving image shooting mode. select.

  Under the photographing mode, the subject light incident through the imaging lens 31 and the diaphragm 32 enters the CCD image sensor 2. In the CCD image sensor 2, the subject light that has passed through the microlens and the color filter is converted into signal charges by the PD 10, and the signal charges from each PD 10 are transferred to the LM 12 via the VCCD 11 under the control of the CCD driver 40. FIG. 3 shows a state in which signal charges for one line are accumulated in the LM 12, and the notation in which R, G, and B are circled indicates signal charges corresponding to each color. The subsequent signal charge output and horizontal transfer method from the LM 12 to the HCCD 13 differs depending on the ISO sensitivity set in the EEPROM 43 and is controlled by the CPU 22.

  The CPU 22 determines whether or not the ISO sensitivity set in the EEPROM 43 is greater than a predetermined value (for example, ISO 800). When the ISO sensitivity setting value is smaller than the predetermined value, first, the G (green) signal charge is transferred to the HCCD 13 as shown in FIG. The G signal charge transferred to the HCCD 13 is horizontally transferred to the FDA 14. Next, as shown in FIG. 4B, the R (red) and B (blue) signal charges remaining in the LM 12 are transferred to the HCCD 13 and then horizontally transferred to the FDA 14. A similar transfer operation is performed for each line, and the signal charge transferred to the FDA 14 is converted into a signal voltage (imaging signal) and input to the analog signal processing circuit 24.

  On the other hand, when the ISO sensitivity setting value is larger than the predetermined value, color separation transfer is performed. First, as shown in FIG. 5A, after the G signal charge is transferred to the HCCD 13 and horizontally transferred to the FDA 14, as shown in FIG. 5B, the R and B signal charges remaining in the LM 12 are used. The R signal charge is transferred to the HCCD 13 and horizontally transferred to the FDA 14. Thereafter, as shown in FIG. 5C, the B signal charge remaining in the LM 12 is transferred to the HCCD 13 and transferred horizontally to the FDA 14. The same color transfer operation is performed for each line, and the signal charge transferred to the FDA 14 is converted into a signal voltage (imaging signal) and input to the analog signal processing circuit 24.

  In the analog signal processing circuit 24, various analog signal processes are performed on the imaging signal. The image signal processed by the analog signal processing circuit 24 is converted into a digital image signal by the A / D 25 and temporarily stored in the buffer memory 26.

  The image data stored in the buffer memory 26 is read out to the YC processing circuit 28, converted into the luminance signal Y and the color difference signals Cr and Cb, and then displayed as a through image on the LCD 39 via the LCD driver 38. . When the release button 41 is pressed halfway in this state, the operation of each unit is controlled by the CPU 22 based on the detection result of the photometry / ranging circuit 29, and photographing preparation processing is performed.

  When shooting is executed by fully pressing the release button 41 after shooting preparation processing, the image data currently recorded in the buffer memory 26 is compressed by the compression / decompression processing circuit 27 in the still image shooting mode, and the card Stored in the memory card 37 via the I / F 36

  On the other hand, under the moving image shooting mode, the same processing as described above is performed at a constant frame rate (for example, 30 frames / second) until the release button 41 is fully pressed again, and moving image data is created. At the same time, ambient sounds are recorded via a microphone (not shown). The sound recorded by the microphone is stored in the memory card 37 in association with the moving image data.

  As described above, in the high sensitivity mode in which the ISO sensitivity setting value is larger than the predetermined value, the signal charge stored in the LM 12 is divided into three times for each color and output to the HCCD 13 for horizontal transfer. Since color separation transfer is performed, even if transfer deterioration occurs and signal charges are mixed, the same color is not a big problem, and color change due to color mixture can be prevented. Further, in the low sensitivity mode in which the ISO sensitivity setting value is lower than the predetermined value, the influence of color mixture is small, so horizontal transfer is performed twice for G, R, and B, and in the high sensitivity mode. We are trying to increase the speed.

  In the above-described embodiment, in the low sensitivity mode, after the G signal charge is horizontally transferred, the R and B signal charges are horizontally transferred. However, the present invention is not limited to this, and the R and B signal charges are transferred. After the charges are horizontally transferred, the G signal charges may be horizontally transferred.

  In the above embodiment, the signal charges are horizontally transferred in the order of G, R, and B in the high sensitivity mode. However, the present invention is not limited to this, and the transfer order for this color is appropriately changed. The order may be changed for each line.

  In the above embodiment, the CCD image sensor 2 in which the PDs 10 are arranged in a honeycomb shape is described as an example. However, the PDs 10 may be arranged in a square array and the color arrangement of the color filters may be a so-called Bayer array. Further, a CMY color filter may be used instead of the RGB color filter. The arrangement and color arrangement of the PD 10 do not limit the present invention.

  Furthermore, in the above-described embodiment, the digital camera 20 has been described as an example of the photographing device. However, the present invention is not limited to this and can be applied to other photographing devices such as a camera-equipped mobile phone. .

It is the schematic which shows the structure of a CCD image sensor. It is a block diagram which shows the internal structure of a digital camera. It is a figure which shows a mode that the signal charge for 1 line was accumulate | stored in the line memory. It is explanatory drawing which shows the horizontal transfer operation | movement at the time of a low sensitivity mode. It is explanatory drawing which shows the horizontal transfer operation | movement at the time of a high sensitivity mode.

Explanation of symbols

2 CCD image sensor 10 Photoelectric conversion element (PD)
11 Vertical CCD (VCCD)
12 line memory (LM)
13 Horizontal CCD (HCCD)
14 Floating diffusion amplifier (FDA)
20 Digital camera 22 CPU
24 Analog signal processing circuit 30 Timing generator (TG)
40 CCD driver

Claims (3)

A plurality of types of photoelectric conversion elements that photoelectrically convert light of a specific color; a plurality of vertical CCDs that are provided for each vertical column of the photoelectric conversion elements and that vertically transfer signal charges from the photoelectric conversion elements; A line memory for temporarily storing and outputting signal charges for one line transferred from the vertical CCD, a horizontal CCD for horizontally transferring the signal charges output from the line memory, and a signal charge transferred by the horizontal CCD. In an imaging device equipped with a solid-state imaging device having an output circuit for outputting a corresponding imaging signal,
An imaging apparatus comprising: control means for performing color separation transfer in which signal charges accumulated in the line memory are output to the horizontal CCD for each color and then transferred horizontally.   ISO sensitivity setting means and signal amplification means for amplifying the imaging signal output from the output circuit based on the ISO sensitivity set by the setting means, and the color separation transfer is a set value of the ISO sensitivity. The photographing apparatus according to claim 1, wherein the photographing apparatus is operated when is larger than a predetermined value. The photographing apparatus according to claim 1, wherein the photoelectric conversion elements are two-dimensionally arranged in a honeycomb shape.

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