JP2008199483A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device capable of setting up an amplification rate for each of photographed pixel signals and obtaining a proper photographed image. <P>SOLUTION: An analog front end apparatus 4 comprises a first gain adjustment circuit 42a to a sixth gain adjustment circuit 42f for performing gain adjustment processing for a signal for each pixel constituting an analog image signal outputted from a CDS circuit 41, a single column conversion circuit 43 for selecting and outputting an output signal from each of the gain adjustment circuits 42a-42f to output one-column output signals, an AD conversion circuit 46 for converting the analog image signal into a digital image signal, and an amplification rate storage apparatus 44 in which an amplification rate corresponding to each of two or more kinds of pixel signals is stored. Using an amplification rate corresponding to each pixel signal and stored in the amplification rate storage apparatus 44, each of the gain adjustment circuits 42a-42f performs signal amplification processing for each pixel signal constituting an analog image array signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an amplification process of an analog image signal.

  In recent years, imaging devices such as digital cameras have become widespread. A conventional imaging device 100 is shown in FIG. The imaging apparatus 100 includes a lens 102, an imaging element 103 configured by a CCD, a CMOS sensor, or the like, an analog front end device 104, an image signal processing device 105, a storage device 106, a display device 107, and an operation device 108. In the image sensor 103, R, G, and B color filters 111 corresponding to each pixel are arranged in a Bayer arrangement format in which, for example, two each are repeatedly arranged in the row direction and the column direction. The image sensor 103 operates according to the drive pulse transmitted from the analog front end device 104.

  The imaging apparatus 100 converts information of light incident through the lens 102 into an analog image signal by the image sensor 103 performing photoelectric conversion, and the analog front-end device 104 uniformly converts all the pixels to this image signal. After performing a CDS process, a gain adjustment process, etc., it inputs into the image signal processing apparatus 105, and produces | generates captured image data by performing various signal processes. The generated captured image data is displayed on the display device 107 or stored in the storage device 106.

  As shown in FIG. 5, the analog front-end device 104 performs a CDS circuit 121 that performs CDS processing, a gain adjustment circuit 122 that performs gain adjustment processing, and an analog image signal on pixel signals constituting the analog image signal. It has an AD conversion circuit 123 that converts it into a digital image signal, and performs correction processing of the image signal using a uniform amplification factor for all the pixels of the pixel signal constituting the analog image signal. The analog front-end device 104 further includes a timing generation unit (not shown) that generates a driving pulse for driving the image sensor 103 in order to drive the image sensor 103.

  The analog image signal output from the image sensor 103 has a signal amount of each pixel constituting the analog image signal due to the driving method of the image sensor 103, the low charge transfer efficiency accompanying the miniaturization, the signal deterioration due to the substrate pattern, and the like. There may be differences. If there is a difference in the signal amount of each pixel, if the pixel arrangement of this image signal is used as it is, vertical lines are generated on the captured image, or if the pixel arrangement of this image signal is rearranged, A horizontal line may occur on the captured image. As a result, a good captured image may not be obtained.

  With respect to the above problem, Patent Document 1 and Patent Document 2 can set an amplification factor for each color filter of the pixel signal for the pixel signal, and provide a gain adjustment circuit based on the set amplification factor. An imaging apparatus that performs amplification processing of pixel signals using the same is disclosed. Patent Documents 3 and 4 disclose an imaging apparatus that can switch the amplification factor of an image signal to a plurality of predetermined values. However, in the imaging devices of Patent Literature 1 to Patent Literature 4, since it is not possible to set the amplification factor for each of the captured pixel signals, it may be impossible to obtain a good captured image.

By the way, Patent Document 5 discloses an imaging apparatus in which a gain adjustment circuit sequentially performs gain adjustment processing on pixel signals output from a plurality of imaging elements. However, even the imaging device of Patent Document 5 cannot solve the above problem.
JP 2001-28716 A JP 2002-165225 A JP 2002-199283 A JP 2002-57945 A JP 2004-40515 A

  The present invention has been made to solve the above-described problem, and provides an imaging apparatus capable of setting an amplification factor for each captured pixel signal and obtaining a good captured image. For the purpose.

  In order to achieve the above object, according to the first aspect of the present invention, color filters of R, G, and B colors are arranged corresponding to each pixel, and the charge signal of the subject image projected by the lens is controlled by vertical transfer drive control. An image sensor that performs photoelectric conversion and outputs an analog image signal, and a drive pulse for controlling the vertical transfer drive of the image sensor, in a charge signal array that realizes each setting mode such as a still mode and a liquid crystal display mode. A timing generation unit to be generated, a CDS processing unit for performing a CDS process for obtaining a difference between a reset level value and a data level value of an analog image signal output from the image sensor, and extracting only an actual signal portion, and the CDS A gain adjustment unit that performs gain adjustment processing on the analog image array signal output from the processing unit, and an analog after gain adjustment processing by the gain adjustment unit An analog front end unit that has an AD conversion unit that converts an image array signal into a digital image signal, and performs various image signal processing on the digital image signal output from the analog front end unit, An image signal processing unit that outputs data, a storage unit that stores captured image data output from the image signal processing unit, a display unit that displays captured images and various messages, and a user-operated operation The analog image array signal is an RG pixel array that is a two-pixel array, a GB pixel array, or a GGBR pixel that is a four-pixel array in a certain horizontal period depending on each setting mode. In an imaging device configured with an array, or a GGGRBR pixel array or a GGGBRB pixel array that is a 6-pixel array, The number of gain adjustment units included in the analog front end unit is the same as the number of pixel signals constituting the analog image arrangement signal, and the analog front end unit is provided for each of the pixel signals constituting the analog image arrangement signal. An amplification factor storage unit that stores a corresponding amplification factor; and a single-row conversion processing unit that outputs a single-row output signal by selecting and outputting an output signal from each gain adjustment unit; and Each gain adjustment unit performs signal amplification processing on each of the pixel signals constituting the analog image array signal at an amplification factor corresponding to each pixel signal stored in the amplification factor storage unit. is there.

  According to the second aspect of the present invention, a plurality of color filters are arranged corresponding to each pixel, and the charge signal of the subject image projected by the lens is charged to realize a still mode or a liquid crystal display mode by vertical transfer drive control. An image sensor that performs photoelectric conversion and outputs an analog image signal in a signal arrangement, a timing generation unit that generates a drive pulse for controlling vertical transfer drive of the image sensor, and an analog image output from the image sensor A CDS processing unit that obtains a difference between a signal reset level value and a data level value and extracts only an actual signal portion, and a gain adjustment process for an analog image array signal output from the CDS processing unit A gain adjusting unit that performs the gain adjustment, and an AD conversion that converts the analog image array signal after the gain adjustment processing by the gain adjusting unit into a digital image signal. An analog front-end unit, and an image signal processing unit that performs various image signal processing on the digital image signal output from the analog front-end unit and outputs captured image data, In the imaging device configured with a plurality of pixels, the analog image array signal has the same number of gain adjustment units as the analog front end unit as the number of pixel signals that configure the analog image array signal, The analog front end unit selects and outputs an amplification factor storage unit storing an amplification factor corresponding to each of the pixel signals constituting the analog image array signal and an output signal from each gain adjustment unit. And a single-row conversion processing section for outputting a single-row output signal, and each gain adjusting section is stored in the amplification factor storage section. And an amplification factor corresponding to each of the pixel signals, and performs amplification processing of a signal for each of the pixel signals constituting the analog image array signals.

  According to a third aspect of the present invention, in the imaging apparatus according to the second aspect, a storage unit that stores data of the captured image output from the image signal processing unit, and a display for displaying the captured image and various messages And an operation unit that gives an instruction to the apparatus when operated by a user.

  According to the present invention, it is possible to set an amplification factor for each of the captured pixel signals, and each gain adjustment unit is an analog image with an amplification factor corresponding to each pixel signal stored in the amplification factor storage unit. A signal amplification process is performed on each of the pixel signals constituting the array signal. Therefore, it is possible to precisely amplify each of the captured pixel signals and obtain a good captured image.

  Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows the configuration of the imaging device 1, and FIG. 2 shows the configuration of an analog front end device (analog front end unit) 4.

  The imaging device 1 performs photoelectric conversion on the charge signal of the subject image projected by the lens 2 and outputs an analog image signal. The imaging device 1 controls the imaging device 3 and outputs an analog image signal output from the imaging device 3. And an analog front end device 4 that performs various processes, converts the digital image signal into a digital image signal, and outputs the digital image signal.

  The imaging device 1 also performs various image signal processing such as luminance / color difference signal processing, contour correction processing, and white balance processing on the digital image signal output from the analog front end device 4. A storage device (storage unit) 6 that stores data of the captured image output from the image signal processing device 5, a display device (display unit) 7 for displaying the captured image and various messages, and a user operation. And an operation device (operation unit) 8 that gives instructions to the device.

  The image pickup device 3 converts the charge signal of the subject image projected by the lens 2 into a charge signal array that realizes each setting mode such as a still mode and a liquid crystal mode by vertical transfer drive control, performs photoelectric conversion, and performs analog conversion. It is composed of a CCD that can output signals. This vertical transfer drive control operates according to the drive pulse generated by the timing generator 49 (see FIG. 2) of the analog front-end device 4. In the image sensor 3, color filters 11 of R (red), G (green), and B (blue) colors corresponding to each pixel are arranged. The still mode is an all-pixel reading mode, and the liquid crystal display mode is a mode in which pixels are read out.

  An analog image array signal composed of analog image signals output from the image sensor 3 is an RG pixel array, a GB pixel array, or a two-pixel array in a certain horizontal period depending on each setting mode such as a still mode or a liquid crystal mode. It is composed of a GGBR pixel array that is a 4-pixel array, or a GGGRBR pixel array or a GGGBRB pixel array that is a 6-pixel array. The analog image array signal is not limited to these configuration examples, and may be composed of an array of 6 pixels or more by driving and controlling the image sensor 3.

  As shown in FIG. 2, the analog front-end device 4 includes a timing generation unit 49 that generates a driving pulse for transfer driving control of the image sensor 3, and a reset level value of the analog image signal output from the image sensor 3. And a data level value, a CDS circuit (CDS processing unit) 41 that performs a CDS process for extracting only a real signal portion, and a gain adjustment process for an analog image array signal output from the CDS circuit 41 By selecting and outputting the output signals from the first gain adjustment circuit (gain adjustment unit) 42a to the sixth gain adjustment circuit (gain adjustment unit) 42f and each of the gain adjustment circuits 42a to 42f, one row of output signals is obtained. An output single-row conversion circuit (single-row conversion processing unit) 43 and an analog image array signal output from the single-row conversion circuit 43 are converted into digital image signals. Having an AD converter (AD conversion unit) 46, a setting image mode switching circuit 47 for selecting each gain adjusting circuit 42a~42f use by each setting mode, and a changeover switch (SW) 48a to 48d to be. Here, an example in which the analog front-end device 4 has six gain adjustment circuits is shown, but the analog front-end device 4 has the same number of gain adjustment circuits as the number of pixel signals constituting the analog image array signal. Just do it.

  Further, the analog front-end device 4 has an amplification factor storage device (amplification factor storage unit) 44 in which amplification factors corresponding to each of the pixel signals constituting the analog image array signal are stored, and a single row conversion circuit 43. It further has a selection signal generation device 45 that outputs a selection signal for instructing to select output signals from the gain adjustment circuits 42a to 42f.

  When the setting mode of the imaging apparatus 1 is set to the still mode, the analog image arrangement signal is only the RG pixel arrangement or the GB pixel arrangement, and therefore, only the first gain adjustment circuit 42a and the second gain adjustment circuit 42b may be used. Therefore, the setting image mode switching circuit 47 turns off the SWs 48a to 48d of the third gain adjustment circuit 42c to the sixth gain adjustment circuit 42f.

  A pixel clock signal (pixel CLK in FIG. 2) is input as a clock signal to the amplification factor storage device 44 and the selection signal generation device 45, and output from the CDS circuit 41 to each gain adjustment circuit 42 a to 42 f. The analog image array signal and an amplification factor corresponding to each of the pixel signals constituting the analog image array signal stored in the amplification factor storage device 44 are input.

  Each gain adjustment circuit 42a to 42f uses the amplification factor corresponding to each pixel signal stored in the amplification factor storage device 44, and constitutes the analog image array signal input to each gain adjustment circuit 42a to 42f. Signal amplification processing is performed on each of the signals. The amplification factor storage device 44 stores in advance optimum amplification factors for the respective pixel signals constituting the analog image array signal.

  Next, the processing of each of the gain adjustment circuits 42a to 42f when the setting mode configured by the “GGGRBR” pixel array in which the analog image array signal is a 6-pixel array is set will be described. The first gain adjustment circuit 42a performs an amplification process of a pixel signal corresponding to the first G color of the analog image array signal “GGGRBR”. The second gain adjustment circuit 42 b performs an amplification process on a pixel signal corresponding to the second G color of the analog image array signal “GGGRBR”. The third gain adjustment circuit 42c performs an amplification process on a pixel signal corresponding to the third G color of the analog image arrangement signal “GGGRBR”. The fourth gain adjustment circuit 42d amplifies the pixel signal corresponding to the fourth R color of the analog image array signal “GGGRBR”. The fifth gain adjustment circuit 42e performs amplification processing of the pixel signal corresponding to the fifth B color of the analog image arrangement signal “GGGRBR”. The sixth gain adjustment circuit 42f performs an amplification process of a pixel signal corresponding to the sixth R color of the analog image arrangement signal “GGGRBR”.

  Next, signals output from the single-row conversion circuit 43 will be described with reference to FIG. FIG. 3 shows a time chart of the analog image array signal 53 (gain output in FIG. 3) output as a result of the single row conversion circuit 43 sequentially selecting signals output from the gain adjustment circuits 42a to 42f. . Here, the gain corresponding to each of the pixel signals by the gain adjustment circuits 42a to 42f is, for example, 1 time for the first gain adjustment circuit 42a, 0.6 times for the second gain adjustment circuit 42b, The gain adjustment circuit 42c is 0.7 times, the fourth gain adjustment circuit 42d is 0.9 times, the fifth gain adjustment circuit 42e is 1.3 times, and the sixth gain adjustment circuit 42f is 1.4 times. The timing of the operation of the selection signal generation device 45 and the switching timing of the amplification factor values input from the amplification factor storage device 44 to the gain adjustment circuits 42a to 42f are the pixel clock signal 51 (pixel CLK in FIG. 3). Is determined based on A signal input to each of the gain adjustment circuits 42a to 42f is an analog image array signal (CDS output in FIG. 3) 52.

  The one-row conversion circuit 43 corresponds to a predetermined one pixel signal among the output signals 61 to 66 (gain 1 to gain 6 in FIG. 3) output from the first gain adjustment circuit 42a to the sixth gain adjustment circuit 42f. Select the output signal to be used. The one-column conversion circuit 43 selects a pixel signal in accordance with the timing when the selection 1 signal 71 to the selection 6 signal 76 become low level.

  When the selection signal 71a in the selection 1 signal 71 is received, the one-column conversion circuit 43 selects the output signal 61a in the output signal 61 output from the first gain adjustment circuit 42a, and receives the selection signal 71b. The output signal 61b is selected. When the selection signal 72a in the selection 2 signal 72 is received, the one-row conversion circuit 43 selects the output signal 62a in the output signal 62 output from the second gain adjustment circuit 42b, and receives the selection signal 72b. The output signal 62b is selected.

  When the selection signal 73a in the selection 3 signal 73 is received, the one-row conversion circuit 43 selects the output signal 63a in the output signal 63 output from the third gain adjustment circuit 42c, and receives the selection signal 73b. The output signal 63b is selected. When the selection signal 74a in the selection 4 signal 74 is received, the one-column conversion circuit 43 selects the output signal 64a in the output signal 64 output from the fourth gain adjustment circuit 41d and receives the selection signal 74b. The output signal 64b is selected.

  When the selection signal 75a in the selection 5 signal 75 is received, the one-row conversion circuit 43 selects the output signal 65a in the output signal 65 output from the fifth gain adjustment circuit 42e, and receives the selection signal 75b. The output signal 65b is selected. When the selection signal 76a of the selection 6 signal 76 is received, the one-row conversion circuit 43 selects the output signal 66a in the output signal 66 output from the sixth gain adjustment circuit 42f, and receives the selection signal 76b. The output signal 66b is selected.

  As described above, the single-row conversion circuit 43 outputs a signal selected from the output signals 61 to 66 as a single-row output signal (gain output in FIG. 3) 53. The output signal 61a is the signal 53a in the gain output 53, the output signal 62a is the signal 53b in the gain output 53, the output signal 63a is the signal 53c in the gain output 53, and the output signal 64a is the signal 53d in the gain output 53. The output signal 65a corresponds to the signal 53e in the gain output 53, and the output signal 66a corresponds to the signal 53f in the gain output 53.

  The output signal 61b is a signal 53g in the gain output 53, the output signal 62b is a signal 53h in the gain output 53, the output signal 63b is a signal 53i in the gain output 53, and the output signal 64b is in the gain output 53. The output signal 65 b corresponds to the signal 53 j, the output signal 65 b corresponds to the signal 53 k in the gain output 53, and the output signal 66 b corresponds to the signal 53 l in the gain output 53.

  The analog image array signal output from the one-row conversion circuit 43 is converted into a digital image signal through the AD conversion circuit 46 and output from the analog front end device 4.

  As described above, according to the imaging device 1 according to the present embodiment, the amplification factor can be set for each of the pixel signals constituting the analog image array signal, and each of the gain adjustment circuits 42a to 42f Signal amplification processing is performed on each of the pixel signals using the amplification factor corresponding to each of the pixel signals constituting the analog image array signal stored in the rate storage device 44. For this reason, each pixel signal can be precisely amplified, and a good captured image can be obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the above-described embodiment, an example in which the analog image arrangement signal is configured by pixel signals arranged in the row direction in the order of GGGRBR by transfer drive control has been described. It may be composed of any number of types of pixel signals arranged in the row direction in the color and in any order.

1 is a block diagram showing a schematic configuration of an imaging apparatus according to an embodiment of the present invention. The block diagram which shows the internal structure of the analog front end apparatus of the said imaging device. 4 is a timing chart of output signals output from a single-row conversion circuit in the imaging apparatus. FIG. 10 is a block diagram illustrating a schematic configuration of a conventional imaging apparatus. The block diagram which shows schematic structure of the analog front end apparatus of the said imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Lens 3 Imaging element 4 Analog front end apparatus (analog front end part)
5 Image signal processing device (image signal processing unit)
6 Storage device (storage unit)
7 Display device (display unit)
8 Operation device (operation unit)
11 Color filter 41 CDS circuit (CDS processing unit)
42a First gain adjustment circuit (gain adjustment circuit)
42b Second gain adjustment circuit (gain adjustment circuit)
42c Third gain adjustment circuit (gain adjustment circuit)
42d Fourth gain adjustment circuit (gain adjustment circuit)
42e Fifth gain adjustment circuit (gain adjustment circuit)
42f Sixth gain adjustment circuit (gain adjustment circuit)
43 Single row conversion circuit (Single row conversion processing unit)
44 Amplification rate storage device (amplification rate storage unit)
46 AD converter (AD converter)
49 Timing generator

Claims (3)

Color filters for each color R, G, and B are arranged corresponding to each pixel, and the charge signal of the subject image projected by the lens realizes each setting mode such as still mode and liquid crystal display mode by vertical transfer drive control A charge signal array that performs photoelectric conversion and outputs an analog image signal; and
A timing generator for generating a drive pulse for vertical transfer drive control of the image sensor; and a difference between a reset level value and a data level value of the analog image signal output from the image sensor; A CDS processing unit for performing only CDS processing, a gain adjusting unit for performing gain adjustment processing on the analog image array signal output from the CDS processing unit, and an analog image array after gain adjustment processing by the gain adjusting unit An analog front end unit having an AD conversion unit for converting a signal into a digital image signal;
An image signal processing unit that performs various types of image signal processing on the digital image signal output from the analog front end unit and outputs captured image data;
A storage unit for storing captured image data output from the image signal processing unit;
A display unit for displaying captured images and various messages;
An operation unit that gives an instruction to the apparatus by being operated by a user;
The analog image array signal may be an RG pixel array, a GB pixel array, a 4-pixel array, a GGGRBR pixel array, a GGGBRB, or a 6-pixel array in a certain horizontal period, depending on each setting mode. In an imaging device composed of a pixel array,
The number of gain adjustment units included in the analog front end unit is the same as the number of pixel signals constituting the analog image array signal,
The analog front end is
An amplification factor storage unit in which amplification factors corresponding to each of the pixel signals constituting the analog image array signal are stored;
A single-row conversion processing section that outputs a single-row output signal by selecting and outputting an output signal from each gain adjustment section;
Each gain adjustment unit performs signal amplification processing on each of the pixel signals constituting the analog image array signal at an amplification factor corresponding to each of the pixel signals stored in the amplification factor storage unit. An imaging apparatus characterized by the above. Multiple color filters are arranged corresponding to each pixel, and the charge signal of the subject image projected by the lens is converted into a charge signal array that realizes a still mode and a liquid crystal display mode by vertical transfer drive control, and photoelectric conversion An image sensor that outputs an analog image signal,
A timing generator for generating a drive pulse for vertical transfer drive control of the image sensor; and a difference between a reset level value and a data level value of the analog image signal output from the image sensor; A CDS processing unit for performing only CDS processing, a gain adjusting unit for performing gain adjustment processing on the analog image array signal output from the CDS processing unit, and an analog image array after gain adjustment processing by the gain adjusting unit An analog front end unit having an AD conversion unit for converting a signal into a digital image signal;
An image signal processing unit that performs various types of image signal processing on the digital image signal output from the analog front end unit and outputs captured image data;
The analog image array signal is an imaging device composed of a plurality of pixels.
The number of gain adjusting units included in the analog front end unit is the same as the number of pixel signals constituting the analog image array signal,
The analog front end is
An amplification factor storage unit in which amplification factors corresponding to each of the pixel signals constituting the analog image array signal are stored;
A single-row conversion processing section that outputs a single-row output signal by selecting and outputting an output signal from each gain adjustment section;
Each gain adjustment unit performs signal amplification processing on each of the pixel signals constituting the analog image array signal at an amplification factor corresponding to each of the pixel signals stored in the amplification factor storage unit. An imaging apparatus characterized by the above. A storage unit for storing data of the captured image output from the image signal processing unit;
A display unit for displaying captured images and various messages;
The imaging apparatus according to claim 2, further comprising an operation unit that gives an instruction to the apparatus when operated by a user.

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