JP5300312B2 - Solid-state imaging device, control method for solid-state imaging device, and information device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device capable of avoiding a black level depression phenomenon. <P>SOLUTION: The solid-state imaging device includes an image sensor 101 capable of reading a plurality of pixels, a CDS circuit 102 which performs correlation double sampling with an output signal of the image sensor 101, and a clamp circuit 103 for clamping black level of the output signal of the CDS circuit 102. It also includes an AD conversion part 104 which performs analogue-digital conversion with the output signal clamped by the clamp circuit 103, and an image signal processing part 106 for image-processing the output signal of the AD conversion part 104. It further includes a brightness addition processing part 107 which makes addition in vertical direction with the brightness data of a frame image processed with the image signal processing part 106, and a brightness change amount detecting part 108 which detects change amount of the output data of the brightness addition processing part 107. It further includes an image sensor drive control part 105 which changes a pixel addition reading method of the image sensor 101 according to the output of the brightness change amount detecting part 108. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a solid-state imaging device, a control method for the solid-state imaging device, and information equipment.

  2. Description of the Related Art Conventionally, solid-state imaging devices that incorporate an imaging element such as a CCD have been proposed. FIG. 12 is a block diagram illustrating a schematic configuration of a conventional solid-state imaging device.

  In FIG. 12, an image pickup device 1 such as a CCD is for taking light as an electric signal. A CDS (Coated Double Sampling) circuit 2 removes a clock component included in an electric signal output from the image sensor 1. The clamp circuit 3 clamps the output signal of the CDS circuit 2 to a predetermined reference voltage.

  The AD converter 4 converts the clamp output signal output from the clamp circuit 3 from an analog signal to a digital signal. The image sensor drive control unit 5 controls the operation timing of the image sensor 1, the CDS circuit 2, the clamp circuit 3, and the AD converter 4 and driving of the image sensor 1. The image signal processing unit 6 converts the digital data sent from the AD conversion unit 4 into image signal data.

In the produced conventional solid-state image pickup measures as described above, since it takes time Reading all pixels of the solid-state imaging device, it is carried out pixel-addition reading as a method for displaying a live image by reducing the pixel to be read .

  Hereinafter, a 4-pixel addition method will be described as an example of pixel addition in the pixel addition reading.

  Each pixel of the solid-state imaging device 1 has a color filter. As shown in FIG. 4, red, green, and blue (hereinafter referred to as R, G, and B) color filters are installed by the pixel 401.

The result of pixel addition is read out as pixel 402 in FIG. In FIG. 4, R1 pixel, R2 pixel, R3 pixel, and R4 pixel of the pixel 401 of the image sensor are added and read out as one R pixel. Further, G1 pixel, G2 pixel, G3 pixel and G4 pixel are added and read as one G pixel. Thus, a reading method for reducing the reading amount is a four-pixel addition reading method (see Patent Documents 1 and 2).
JP 2003-174594 A JP 2003-324659 A

  Recently, solid-state image sensors have evolved and the number of pixels has increased. At this time, in order to display a large number of frames of a live image, an increasing number of solid-state imaging devices are configured to be read at high speed by increasing the number of added pixels.

  However, if the number of added pixels is increased, the amount of charge as one pixel increases. As a result, there is a problem that when high-intensity light is input to the light-receiving surface of the solid-state imaging device, the high-intensity part causes darkening as described later. Further, the conventional configuration has a problem that the configuration for detecting the black sun phenomenon is complicated.

  The principle of causing this black sun set when a CCD is used as the solid-state imaging device will be briefly described with reference to FIG.

  FIG. 13 is a diagram illustrating the configuration of the final stage of the horizontal transfer path that is the final output of the CCD, which is a solid-state imaging device.

  In the final stage of the horizontal transfer path, the horizontal transfer paths H1 and H2 are a floating diffusion amplifier (FD amplifier) that functions as a capacitor that changes signal charges into voltage, a reset gate for resetting the FD amplifier section, It consists of a drain that discharges.

  In (a), charge is transferred to H2 at the rise of H1. In the state of (b), surplus charges that exceed the storage capacity of H2 flow out to the FD amplifier unit. When the reset gate is on, the excess charge that has flowed out is discarded to the drain portion. In the state (c), the reset gate is off, and the excess charge that has flowed out remains in the FD amplifier section. In such a state, the feedthrough portion sinks and a black sun phenomenon occurs.

  An object of the present invention is to provide a solid-state imaging device, a control method for the solid-state imaging device, and an information device that can avoid the black sun phenomenon.

In order to achieve the above object, a solid-state imaging device according to claim 1, a solid-state imaging device capable of adding and reading a plurality of pixels, correlated double sampling means for correlated double sampling of an output signal of the solid-state imaging device, Clamp means for clamping the black level of the output signal of the correlated double sampling means, analog-digital conversion means for analog-digital conversion of the output signal clamped by the clamp means, and output signal of the analog-digital conversion means Image signal processing means for performing image processing, luminance addition processing means for adding luminance data of the frame image processed by the image signal processing means in the vertical direction, and change in output data of the luminance addition processing means in the horizontal direction a luminance variation detection means for detecting an amount, that a rapid change in the output data of said luminance addition processing means When the luminance variation detection unit detects, wherein a rapid change the stored position in the horizontal direction so as to reduce the number of pixels in performing pixel addition read from the solid-solid-state imaging The pixel addition reading method of the element is changed, and the stored amount before the change in the stored horizontal position in the output data of the luminance addition processing means obtained after the change is changed to the number of pixels. Control means for returning the number of pixels when performing pixel addition readout from the solid-state imaging device to the number of pixels before the change when the amount of change in position in the horizontal direction is equivalent to To do.

5. The solid-state imaging device control method according to claim 4, wherein the solid-state imaging device includes a plurality of solid-state imaging devices capable of adding and reading pixels. A clamp step for clamping a black level of an output signal of the correlated double sampling step, an analog-digital conversion step for analog-digital conversion of the output signal clamped by the clamp step, and the analog-digital conversion step An image signal processing step for image processing of the output signal, a luminance addition processing step for adding the luminance data of the frame image processed in the image signal processing step in the vertical direction, and a horizontal direction of the output data of the luminance addition processing step luminance variation detection scan for detecting the amount of change in And-up, if that there is a rapid change in the output data at the luminance addition processing step has been detected by the luminance variation detection step, and storing the position in the horizontal direction with the sharp change The pixel addition readout method of the solid-state imaging device is changed so as to reduce the number of pixels when pixel addition readout is performed from the solid-state imaging device , and the storage in the output data in the luminance addition processing step performed after the change When the amount of change in the position in the horizontal direction is equal to the stored amount of change in the position in the horizontal direction before changing the number of pixels, when performing pixel addition reading from the solid-state imaging device And a control step of returning the number of pixels to the number of pixels before the change .

  An information device according to a seventh aspect mounts the solid-state imaging device according to the first aspect.

  The solid-state imaging device and the control method of the solid-state imaging device of the present invention can avoid the black sun phenomenon.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of the solid-state imaging device according to the first embodiment of the present invention.

  In the solid-state imaging device 100 of FIG. 1, an imaging device (a solid-state imaging device capable of adding and reading a plurality of pixels) 101 captures light as an electrical signal.

  A CDS circuit (correlated double sampling means for performing correlated double sampling on the output signal of the solid-state imaging device) 102 removes a clock component included in the electrical signal output from the imaging device 101.

  A clamp circuit (clamp means for clamping the black level of the output signal of the correlated double sampling means) 103 clamps the output signal of the CDS circuit 102 to a predetermined reference voltage.

  An AD conversion unit (analog-digital conversion means for analog-to-digital conversion of the output signal clamped by the clamp means) 104 converts a clamp output signal output from the clamp circuit 103 from an analog signal to a digital signal.

  The image sensor drive control unit 105 controls the operation timing of the image sensor 101, the CDS circuit 102, the clamp circuit 103, and the AD conversion unit 104 and driving of the image sensor 101.

  An image signal processing unit (image signal processing unit that performs image processing on the output signal of the analog-digital conversion unit) 106 performs a conversion process on the digital data sent from the AD conversion unit 104 into image signal data.

  A luminance addition processing unit (luminance addition processing unit that adds the luminance data of the frame image processed by the image processing unit in the vertical direction) 107 is the luminance data of the image signal data for one frame processed by the image signal processing unit 106. Are added vertically.

  A luminance change amount detection unit (luminance change amount detection unit that detects a change amount of output data of the luminance addition processing unit) 108 calculates a change amount of the luminance addition data output from the luminance addition processing unit 107 and performs a predetermined change. It is detected whether it is larger than the amount, and is compared with the stored change amount.

  The luminance addition processing unit 107 and the luminance change amount detection unit 108 are blocks that are digitally software processed in the system control unit 210 shown in FIG.

  The image sensor 101 can read and add a plurality of pixels under the control of the image sensor drive control unit 105.

  Here, the image sensor drive control unit 105 as a control unit changes the pixel addition reading method of the image sensor 101 according to the output of the luminance change amount detection unit 108.

  Further, the image sensor drive control unit 105 changes the operation timing of the CDS circuit 102 according to the result of comparing the outputs of the luminance change amount detection unit 108 before and after the pixel addition reading method of the image sensor 101 is changed.

  FIG. 2 is a block diagram showing a schematic configuration of a digital camera as an information device according to the embodiment of the present invention on which the solid-state imaging device of FIG. 1 is mounted.

  As described above, the luminance addition processing unit 107 and the luminance change amount detection unit 108 in the solid-state imaging device 100 are digitally software processed in the system control unit 210.

  The lens 201 forms an optical image of the subject on the image sensor 101. The aperture / shutter 202 has a shutter function and also serves as an aperture for controlling the amount of light that has passed through the lens 201.

  The optical system driving unit 208 drives the lens 201 and the aperture / shutter 202. The system control unit 210 controls the entire digital camera and performs various calculations. The memory 211 is used as a work memory or an image memory for images when the system control unit 210 performs processing.

  The recording medium 212 is a semiconductor memory or the like for recording or reading captured image data or audio data. The power supply unit 213 supplies power to all blocks of the digital camera.

  The switch unit 214 is a main switch for turning on / off the power of the digital camera, a release switch for supporting photographing, or the like. The image display unit 215 is an LCD or the like that displays display data sent from the system control unit 210.

  FIG. 3 is a flowchart showing a procedure of photographing (imaging) processing executed by the digital camera of FIG.

  This process is executed under the control of the system control unit 210 in FIG.

  When the main switch in the switch unit 214 is turned on (step S301), the power source unit 213 starts operation and supplies main power and control system power. It is determined whether the mode is shooting or playback (step S302). If the mode is shooting mode, the shooting sequence is entered.

  If the playback mode is set, the playback sequence is entered, image data is read from the recording medium 212 (step S303), signal processing for output to the image display unit 215 is performed, and the image is displayed (step S304).

  Thereafter, the image is displayed until the main switch is turned off. When the main switch is turned off (step S305), the image display is stopped and the power is turned off.

  If it is determined in step S302 that the imaging sequence is entered, the power of the solid-state imaging device 100 is turned on, and the solid-state imaging device 100 is driven in a pixel addition mode for processing a live image (step S306).

  The lens 201 is driven to the reset position (step S307), and the aperture / shutter 202 is first opened by a signal from the optical system driving unit 208 under the control of the system control unit 210 (step S308).

  Thereafter, the AF sequence is entered, and image data obtained by processing the signal passing through the image sensor 101 by the solid-state imaging device 100 is input to the system control 210, where an AF / AE control value is calculated (step S309).

  In accordance with this calculation result, the system control 210 controls the aperture and shutter 202 (step S310). It is determined whether the release switch in the switch unit 214 is pressed (step S311).

  If the release switch has not been pressed, the process returns to the AF / AE processing sequence (step S309). If the release switch is pressed, the solid-state imaging device 100 is changed to the all-pixel readout mode for photographing (step S312).

  Then, photographing is performed, and the photographed data is processed by the system control 210 and recorded in the recording medium 212 (step S313). The solid-state imaging device 100 is driven again in the pixel addition mode for processing the live image (step S314), and the process returns to the AF / AE processing sequence (step S309).

  When the main switch is turned off, the power of the solid-state imaging device 100 is turned off, each mechanism of the optical block returns to a predetermined position, and the main power is turned off.

  4 is an explanatory diagram of 4-pixel addition reading in the solid-state imaging device of FIG. 1, and FIG. 5 is an explanatory diagram of 9-pixel addition reading in the solid-state imaging device of FIG.

  The pixel of the image sensor 101 has a color filter, and R, G, and B color filters are provided depending on the pixel, such as the pixel 401 in FIG. 4 and the pixel 501 in FIG. 5. The result of pixel addition is read as the pixel 402 in FIG. 4 or the pixel 502 in FIG.

  Since the 4-pixel addition readout method shown in FIG. 4 has been described above, a duplicate description is omitted.

  In FIG. 5, the R1 pixel, R2 pixel, R3 pixel, R4 pixel, R5 pixel, R6 pixel, R7 pixel, R8 pixel, and R9 pixel of the pixel 501 of the image sensor are added and read as one R pixel. In addition, the G1, G2, G3, G4, G5, G6, G7, G8, and G9 pixels are added and read as one G pixel. Thus, readout for reducing the readout amount is 9-pixel addition readout.

  FIG. 6 is a flowchart showing a procedure of control processing executed by the solid-state imaging device of FIG.

  When a normal live image is displayed, the readout amount is reduced and n-pixel addition readout driving is performed, and the operation is performed with a reduced amount of data (step S601). An n-pixel read signal output from the image sensor 101 is processed by the CDS circuit 102, the clamp circuit 103, the AD conversion unit 104, and the image signal processing unit 106 to create an image signal.

  7 is an explanatory diagram (1) of the luminance addition processing of the luminance addition processing unit in FIG. 1, and FIG. 8 is an explanatory diagram (2) of the luminance addition processing of the luminance addition processing unit in FIG.

  As shown in FIG. 7, the luminance signal is added in the vertical direction of one field by the luminance addition processing unit 107 in each field of the image signal (step S602). The luminance change amount detection unit 108 calculates the horizontal luminance change amount for one field from the added data as shown in FIG. 8 (step S603).

  The presence / absence of a change that is steeper than the predetermined change amount in the luminance change amount is detected (step S604). If there is no steep change in step S604, it is determined that there is no black sun phenomenon (step S605). The readout method of the image sensor 101 is returned to the n-pixel addition readout mode (step S601).

  If a steep change is detected in step S604, the horizontal position where the steep change appears is stored (step S606). The image sensor drive control unit 105 changes the control from the n pixel addition readout of the image sensor 101 to the nm pixel addition readout (step S607).

  A signal read from the image sensor 101 after the read change is processed by the CDS circuit 102, the clamp circuit 103, the AD conversion unit 104, and the image signal processing unit 106, thereby generating an image signal of nm pixel reading.

  The luminance data for one frame of the image signal read from nm pixels is added in the vertical direction by the luminance addition processing unit 107 (step S608). The luminance change amount detection unit 108 calculates the horizontal luminance change amount for one field from the added data (step S609).

  The luminance change amount at the horizontal position where the luminance change amount stored in step S606 is steep is compared with the luminance change amount calculated in step S609 (step S610). As a result of the comparison in step S610, if the amount of change in luminance is the same, it is determined that there is no black sun phenomenon (step S611). The readout method of the image sensor 101 is returned to the n-pixel addition readout mode (step S601).

  As a result of the comparison in step S610, if there is no luminance change amount, it is determined that the black sun phenomenon has occurred (step S612). If it is determined that the black sun phenomenon has occurred, the image pickup device 101 is set to the n pixel addition reading mode by the black sun countermeasure operation (step S613).

  Next, an example of the black sun set countermeasure operation will be described with reference to FIG.

  FIG. 9 is a diagram illustrating an output signal of the image sensor of FIG.

  As an output signal for one pixel of the image sensor 101, a reset period 902 shown in a signal 901 in FIG. 5, a feedthrough output period 903 having no signal, and an output signal period 904 are repeatedly output.

  In normal operation, the CDS circuit 102 samples and holds the signal level of the output signal period 904 and the level of the feedthrough output period 903 according to the timing given from the image sensor drive control unit 105 to the CDS circuit 102. Then, a signal level 905 that is a difference level is output from the CDS circuit 102 as an output signal.

  In the black sun countermeasure operation, the CDS circuit 102 samples and holds the signal level of the output signal period 904 and the level of the reset period 902 according to the timing given from the image sensor drive control unit 105 to the CDS circuit 102. Then, a signal level 906 that is a difference level is output from the CDS circuit 102 as an output signal. Thereafter, the image signal processing unit 106 subtracts a value corresponding to the offset level 907.

  By such digital software processing, it is possible to easily detect the black sun phenomenon without providing a special circuit.

  FIG. 10 is a block diagram showing a schematic configuration of a solid-state imaging apparatus according to the second embodiment of the present invention.

  In the solid-state imaging device according to the second embodiment, the same blocks as those of the solid-state imaging device according to the first embodiment in FIG.

  In the solid-state imaging device of the second embodiment, in addition to the configuration of the solid-state imaging device of the first embodiment, a wider range is projected than the imaging range of the imaging element 801, and the number of pixels is extremely large compared to the imaging element 801. A small luminance detection unit (area sensor, area detection step) 1001 is provided. The luminance detection unit 1001 can detect the luminance of the projected area.

  Here, the imaging element drive control unit 105 as a control unit changes the pixel addition reading method of the imaging element 101 when the output value of the area sensor 1001 exceeds a predetermined value. Further, the image sensor drive control unit 105 changes the operation timing of the CDS circuit 102 according to the result of comparing the outputs of the luminance change amount detection unit 108 before and after the pixel addition reading method of the image sensor 101 is changed.

  FIG. 11 is a flowchart illustrating a procedure of control processing executed by the solid-state imaging device of FIG.

  In the flowchart of FIG. 11, the same processing parts as those in the flowchart of FIG.

  In the flowchart of FIG. 11, after the n-pixel addition reading drive in step S601, the output value of the luminance detection unit (area sensor) 1001 is compared with a predetermined value stored for each AE value (step S1101). ).

  If the output value of the luminance detection unit (area sensor) 1001 is larger than a predetermined value, the image signal processed by the image signal processing unit 106 is converted by the luminance addition processing unit 107 into the vertical direction of one field. Addition processing is performed (step S602). Thereafter, the same processing as in FIG. 6 is developed.

  As described above, unless the output value of the luminance detection unit (area sensor) 1001 is larger than a predetermined value, the processing after step S602 is not performed, so the amount of processing is small and the black sun phenomenon can be easily detected. It becomes.

1 is a block diagram illustrating a schematic configuration of a solid-state imaging device according to a first embodiment of the present invention. It is a block diagram which shows schematic structure of the digital camera as an information equipment which concerns on embodiment of this invention carrying the solid-state imaging device of FIG. 3 is a flowchart illustrating a procedure of photographing (imaging) processing executed by the digital camera of FIG. 2. 4 is an explanatory diagram of 4-pixel addition reading in the solid-state imaging device of FIG. 1. FIG. It is explanatory drawing of 9 pixel addition reading in the solid-state imaging device of FIG. It is a flowchart which shows the procedure of the control processing performed by the solid-state imaging device of FIG. It is explanatory drawing (1) of the luminance addition process of the luminance addition process part in FIG. It is explanatory drawing (2) of the luminance addition process of the luminance addition process part in FIG. It is a figure which shows the output signal of the image pick-up element of FIG. It is a block diagram which shows schematic structure of the solid-state imaging device which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the control processing performed by the solid-state imaging device of FIG. It is a block diagram which shows schematic structure of the conventional solid-state imaging device. It is a figure which shows the structure of the last stage of the horizontal transfer path used as the final output of CCD which is a solid-state image sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Solid-state image sensor 102 CDS circuit 103 Clamp circuit 104 AD conversion part 105 Image sensor drive control part 106 Image signal process part 107 Luminance addition process part 108 Luminance change amount detection part

Claims (7)

A solid-state image sensor capable of adding and reading a plurality of pixels;
Correlated double sampling means for correlated double sampling of the output signal of the solid-state imaging device;
Clamping means for clamping the black level of the output signal of the correlated double sampling means;
Analog-to-digital conversion means for analog-to-digital conversion of the output signal clamped by the clamping means;
Image signal processing means for image processing the output signal of the analog-digital conversion means;
Luminance addition processing means for adding the luminance data of the frame image processed by the image signal processing means in the vertical direction;
Luminance change amount detecting means for detecting a change amount in a horizontal direction of output data of the luminance addition processing means;
When the luminance change amount detecting means detects that there is a steep change in the output data of the luminance addition processing means , the position in the horizontal direction where the steep change is detected is stored, and the pixel from the solid-state imaging device is stored. The pixel addition readout method of the solid-state imaging device is changed so as to reduce the number of pixels when performing addition readout , and the stored horizontal position in the output data of the luminance addition processing means obtained after the change Is equal to the stored amount of change in the horizontal position before changing the number of pixels, the number of pixels when performing pixel addition reading from the solid-state imaging device is changed. A solid-state imaging device comprising: control means for returning to the previous number of pixels . Wherein, prior SL depending on the result of comparing the outputs of the front and rear of the luminance variation detection means for changing the pixel addition reading method, and changing the operation timing of the correlated double sampling means according Item 2. The solid-state imaging device according to Item 1. An area sensor that detects the brightness of an area in which a wider range than the imaging range of the solid-state imaging device is projected;
Wherein, the output value of the area sensor changes the pre-outs containing addition reading method when exceeds a predetermined value, before the output of the front and rear of the luminance variation detection means for changing the Kiga-containing addition reading method The solid-state imaging device according to claim 1, wherein the operation timing of the correlated double sampling means is changed according to a result of comparing the two. In a control method of a solid-state imaging device including a solid-state imaging device capable of reading and adding a plurality of pixels,
A correlated double sampling step for correlated double sampling of the output signal of the solid-state imaging device;
A clamping step for clamping the black level of the output signal of the correlated double sampling step;
An analog-to-digital conversion step for analog-to-digital conversion of the output signal clamped by the clamping step;
An image signal processing step for image processing the output signal of the analog-digital conversion step;
A luminance addition processing step of adding the luminance data of the frame image processed in the image signal processing step in the vertical direction;
A luminance change amount detecting step for detecting a change amount in the horizontal direction of the output data of the luminance addition processing step;
When the output data in the luminance addition processing step is detected to have a steep change in the luminance change amount detection step , the position in the horizontal direction in which the steep change is detected is stored, and the solid-state imaging device The pixel addition readout method of the solid-state imaging device is changed so as to reduce the number of pixels when the pixel addition readout is performed , and the stored horizontal direction in the output data in the luminance addition processing step performed after the change When the amount of change in the position at is equal to the stored amount of change in the horizontal direction before changing the number of pixels, the number of pixels when performing pixel addition reading from the solid-state imaging device is calculated. A control step of returning to the number of pixels before the change . The control step, before SL depending on the result of comparing the output of the luminance variation detection step before and after changing the pixel addition reading method, and changing the operation timing of the correlated double sampling step according Item 5. A control method for a solid-state imaging device according to Item 4. An area detection step of detecting the brightness of an area in which a wider range than the imaging range of the solid-state imaging device is projected;
The control step, the output value of the area detection step changes the pre-outs containing addition reading method when exceeds a predetermined value, before the luminance variation detection step before and after changing the Kiga-containing addition reading method 5. The control method for a solid-state imaging device according to claim 4, wherein the operation timing of the correlated double sampling step is changed according to a result of comparing outputs.   An information device equipped with the solid-state imaging device according to claim 1.

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