JP2005064760A - Detector and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of image quality by difference in level of image signals among regions when reading the image signals from the image pickup element by dividing them into a plurality of regions. <P>SOLUTION: An amount of charge mixture caused when an image signal from each imaging region of an image pickup element 103 having a plurality of imaging regions corresponding to a plurality of output terminals is detected by a means 133A and 133B for detecting the amount of charge mixture, a correction value for correcting a charge mixture component included in the image signal from the respective imaging regions is obtained by an operation means 145 on the basis of detection results by the means for detecting the amount of charge mixture. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a detection apparatus that reads out an image signal from an image sensor while dividing it into a plurality of regions, and a control method therefor.

  In recent years, with the advancement of digital signal processing technology and semiconductor technology, a digital video camera in which a recording / playback device for digitally recording a moving image signal of a standard television system, for example, an NTSC system or a PAL system, and an imaging device has been commercialized. Some digital video cameras have a still image recording function by taking advantage of the feature of digital recording. Some have a digital I / F for connection to a computer or the like, and have a function of taking a captured image into the computer. Furthermore, there are some which have a plurality of recording media and can select the recording media according to the purpose of use of the image.

  In the above-described apparatus, when a recorded image is reproduced by connecting to a television, the image size is determined by the digital video standard, for example, 720 × 480 pixels, but there is no problem, but the digital I / F When transferring an image to other media via the network, a larger number of pixels may be required due to image quality problems.

Accompanying the increase in the number of pixels of the image sensor, it is necessary to drive the image sensor at a higher frequency in order to read out information of all the pixels of the image sensor, leading to S / N degradation and increased power consumption.
As one method for increasing the data rate of imaging information while keeping the driving frequency of the imaging device low, the imaging surface is divided into a plurality of regions, and independent charge transfer units, amplifiers, and output terminals are provided in each region. There is a method of reading the imaging signals in parallel. An example of such an image sensor is shown in FIG. In the figure, the imaging surface of the imaging device 1400 is divided into two regions on the left and right, 1401 and 1402 are photoelectric conversion and vertical transfer units in each region, 1403 and 1404 are horizontal transfer units in each region, 1405 and 1406, respectively. Are amplifiers in each region, and 1407 and 1408 are output terminals in each region. By using the imaging device having such a structure, there is an advantage that imaging information having a data rate twice as high as the driving frequency of the imaging device can be obtained.

  However, as a drawback of the above-described method, when an image is generated by combining a plurality of areas due to non-uniform characteristics of the charge transfer unit or amplifier in each area, a boundary line is generated due to a difference in signal level between the areas. There was a problem that image quality degradation occurred. When a CCD area sensor, which is a typical image sensor, is taken as an example, one of the factors that cause a difference in signal level between regions is a decrease in transfer efficiency in the charge transfer unit. In the CCD area sensor, when transfer efficiency decreases in the vertical or horizontal transfer unit, signal charges are mixed into pixels adjacent to the transfer direction, causing image quality deterioration such as color mixing and color shading. The transfer efficiency decrease of the vertical transfer unit is a level difference for each column and cannot be a factor of the level difference between the regions. However, the transfer efficiency decrease of the horizontal transfer unit is a factor of the level difference between the regions.

  In order to solve this problem, for example, in Patent Document 1, in a multi-divided readout sensor, an unbalance amount between a plurality of regions is calculated, and a step difference correction between the plurality of regions is performed according to the calculation result. Is described.

JP 2000-253305 A

  If the transfer efficiency of the output gate unit 1502 decreases due to an experiment or the like this time, the amount of signal charge mixed into the adjacent pixel becomes constant in the region without depending on the number of transfer stages, causing uniform color mixture on the screen. In the case of the above-described region-divided readout image sensor, the image quality deterioration occurs in different amounts between the regions, and thus a problem has been found that a boundary line is generated on the composite screen.

  The present invention has been made in view of the above-mentioned problems, and compensates for signal charge mixture in other pixels in the region and prevents image degradation of the composite image due to the level difference of the image signal between the regions. It is an object of the present invention to provide a detection device that can output a value and a control method thereof.

  The detection device of the present invention detects a charge mixing amount generated when an image signal from each imaging region of an imaging device having a plurality of imaging regions corresponding to a plurality of output terminals is transferred within the imaging device. Detection result by the charge mixing amount detection means, and correction values respectively corresponding to the plurality of output terminals for correcting charge mixing components included in the image signals from the respective imaging regions. And calculating means for calculating based on the above.

  The control method of the detection apparatus according to the present invention includes a charge mixing amount detection step of detecting a charge mixing amount generated when an image signal is transferred from each imaging region of an imaging element having a plurality of imaging regions corresponding to a plurality of output terminals. And a calculation step of calculating a correction value for correcting the charge mixing component included in the transferred image signal based on the detection result in the charge mixing amount detection step.

  According to the present invention, it is possible to detect the amount of signal charge mixed into adjacent pixels generated in each area when the image signal from the image sensor is divided into a plurality of areas and read. For this reason, it is possible to prevent image quality deterioration such as color mixing or color shading due to a difference in level of an image signal between regions, or a boundary line between regions in a synthesized image.

(First embodiment)
FIG. 1 is a block configuration diagram of an imaging apparatus equipped with a detection apparatus according to the first embodiment of the present invention.
In the figure, the image that has passed through the lens 101 is formed on the image sensor 103. In this embodiment, a CCD area sensor is applied as the image sensor. The image signal formed on the CCD area sensor 103 is converted into an electrical signal, and then read out for each of the left and right areas obtained by dividing the imaging surface of the CCD area sensor 103, and the output signal in the left half area is buffered 105A. The output signal in the right half region is output to the buffer 105B.

FIG. 2 is a schematic diagram showing a specific example of the CCD area sensor 103.
The imaging surface of the CCD area sensor 103 is divided into a left half area 201A and a right half area 201B. Here, in each of the areas 201A and 201B, imaging area dummy data including a plurality of pixels that generate image signals is arranged. Further, optical black portions 203A and 203B are disposed at both ends of the imaging surface of the CCD area sensor 103, respectively. The images that have been sequentially vertically transferred from the areas 201A and 201B are respectively output to the horizontal transfer sections 205A and 205B provided for each area, and the horizontal transfer section 205A in the left half area 201A has the left direction in FIG. The horizontal transfer unit 205B in the right half area 201A performs horizontal transfer in the right direction in the figure, and then converts the voltage into voltage by the read amplifiers 207A and 207B for each area and outputs them to the output terminals 209A and 209B, respectively. .

FIG. 3 is a schematic diagram showing the output timing of the image signal of the CCD area sensor 103.
301A and 301B shown in FIG. 3 indicate one horizontal period in the image signal of the left half area 201A and the right half area 201B of the imaging surface in the CCD area sensor 103 shown in FIG. In FIG. 3A, the horizontal axis is time. The image signals in the left and right regions in the same horizontal period are read out in the same horizontal period, and the reading order is read from the outside to the inside of the imaging surface, so the optical black portions 203A and 203B are read first. Subsequently, an image is read from the pixel located on both sides toward the pixel located at the center. Thereafter, after the readout of the image of the pixel of one horizontal line is finished, the horizontal transfer pulse is continuously applied until the image signal of the image of the next one horizontal line is transferred to the horizontal transfer unit, Dummy data is read out. Here, FIG. 3B shows an enlarged view of reading out the dummy data.

As shown in FIG. 3B, an example in which a primary color filter is applied as the dummy data portion of this embodiment will be described below.
When the primary color checkered filter is used, the GBGB color filter and the RGRG color filter are alternately attached to each line. In the figure, an example in the case of the GB line is shown. After sequentially reading GBGB as the image signal 301A of the left half region, dummy data is read as DM1A, DM2A,. On the other hand, since the image signal 301B of the right half area is read from the right end, the order of G and B is reversed from that of the image signal 301A of the left half area described above, and after being read as BGBG. The dummy data is read as DM1B, DM2B,.

Next, returning to FIG.
Output signals from the buffers 105A and 105B are output to the CDSs 109A and 109B, respectively, and the CDS 109A and 109B removes low frequency noise by applying correlated double samples to the CCD output waveforms on the left and right imaging surfaces, respectively. Subsequently, the respective output signals are converted from analog signals to digital signals by the A / D conversion means 111A and 111B, the outputs are transferred to the dummy data detection means 133A and 133B, and the detection results are stored in the storage means 163. . The calculation means 145 reads from the storage means 163 and performs processing. Then, the correction value is output to the charge mixing correction means 113A and 113B.

  Here, the mixing of signal charges into adjacent pixels that occur in a certain amount within each region is considered to be due to charges being mixed into adjacent pixels adjacent to one pixel as shown in FIG. Specifically, as shown in FIG. 4A, the charge mixing amount “G1A leak” in the pixel G1A is mixed into the adjacent pixel B1A, and the charge mixing amount “B1A leak” in the pixel B1A is adjacent. It is mixed in a certain pixel G2A. Since the charge mixing amount (Leak) is considered to be constant for a signal (Signal) of a certain signal level, the charge mixing amount from the pixel B2A adjacent to the dummy data DM1A is the signal amount of the dummy data DM1A. It is obtained by measuring.

  The dummy data detection means 133A and 133B in the present embodiment correspond to charge mixing amount detection means, and the dummy data detection means 133A and 133B are dummy data DM1A which is the first pixel of the dummy data portion shown in FIG. Is integrated. One dummy first pixel exists in each of the left and right channels in each horizontal period. Then, the integration result in the dummy data is read by the calculation means 145 as a detection value. Also, as shown in FIG. 4B, when the input light quantity changes and the signal level of the image signal changes, the charge mixing amount mixed into the adjacent pixels also changes.

  FIG. 5 is a characteristic diagram schematically showing the charge mixing amount (Leak) in the first dummy pixel with respect to the signal level (Signal) of the image signal of the imaging apparatus according to the present embodiment. According to the actual measurement, the charge mixing amount (Leak) is steep at the initial stage with respect to the signal level (Signal), and thereafter becomes gentle as the signal level increases.

Therefore, control processing of the detection device (S1 to S3) or the imaging device (S1 to S4) as shown in FIG. 6 is performed. FIG. 6 is a flowchart illustrating a control method of the detection device (S1 to S3) or the imaging device (S1 to S4) in the first embodiment.
First, in step S <b> 1, the exposure control unit 157 changes the luminance of the light amount input to the imaging surface of the CCD area sensor 103.

  Subsequently, in step S2, the dummy data detection unit 133A, 133B detects the charge mixing amount of the first dummy pixel with respect to the luminance of each input light amount, and the detection result is stored in the storage unit 163.

  Subsequently, in step S3, the charge mixture component included in the output signal of the pixel in each region on the imaging surface is corrected based on the detection result of the charge mixture amount of the first dummy pixel in each dummy data detection unit 133A, 133B. A correction value to be obtained is obtained by the calculation means 145. The correction value obtained by the calculation unit 145 may be the measured amount of dummy data detected for each signal level of the input light amount. For example, if the relationship shown in the characteristic diagram of FIG. And a function separated into non-linear components.

  Note that steps S1 to S3 are performed by a detection apparatus including exposure control means 157, dummy data detection means 133A, 133B, calculation means 145, and storage means 163.

  Subsequently, in step S4, based on the correction value obtained by the calculation unit 145, the charge mixture correction unit 113A, 113B corrects the charge mixture component included in the output signal of the pixel in each region of the imaging surface. Thereafter, the outputs of the charge mixing correction units 113A and 11B are output to the linearity correction units 123A and 123B, and the linearity is corrected. At this time, since the linearity is different for each CCD and analog front end, the linearity is measured using the exposure control unit 157 and the measurement result is externally attached to the calculation unit 145 in the same manner as the compensation of charge mixture between adjacent pixels. The data is stored in the storage unit 163, read out from the storage unit 163 by the calculation unit 145 and processed, and the linearity correction units 123A and 123B correct the linearity.

  Thereafter, the output signals of the linearity correction units 123A and 123B are output to the gain correction units 129A and 129B. The gain correction means 129A and 129B (for the right channel not shown) have two roles. First, the first role is to increase the gain electrically when the brightness is insufficient even when the aperture is opened, and the second role is to match the left and right gains. Conventionally, there is an analog amplifier in the analog front end, and gain is increased by setting a decibel gain from the microcomputer to the analog amplifier. However, in the case of the divided readout CCD as shown in this embodiment, an analog amplifier is used. With gain increase, the gain between channels cannot be guaranteed against temperature, voltage, aging, etc., so the analog amplifier is abolished, and instead, the A / D conversion accuracy in the analog front end is increased, For example, the conventional 12 bits are changed to 14 bits, and the gain is increased by digital multiplication.

  After that, the left and right images whose gains have been corrected by the gain correction units 129A and 129B are combined by the combining unit 147 and output to the camera signal processing unit 149 as a single screen signal similar to the conventional one. A large image obtained by the pixel CCD is subjected to various processes such as a reduction process to match the DVC digital video standard, a camera shake correction process, a γ correction, a color separation, a brightness outline enhancement, and the like as an image signal to the output terminal 151. Is output. Steps S1 to S4 are performed by an imaging device configured as shown in the block configuration diagram of FIG.

In addition, using the detection device controlled as in S1 to S3, a timing table of correction values calculated by detecting the charge mixing amount before factory shipment is generated and stored in the imaging device, for example. If the image pickup apparatus is configured to perform image correction using this correction value, a high-quality image without image quality deterioration can be obtained. Further, in this configuration, since the charge mixing amount is not detected during imaging, the processing speed can be increased. Furthermore, the configuration may be such that the detection device portion is provided in the imaging device (the detection device portion is not used during imaging after factory shipment), or is not provided inside the imaging device, but is provided in the imaging device at the time of factory shipment. It may be connected to detect the charge mixing amount.
Further, as in S1 to S4, the imaging apparatus may be configured to detect the charge mixing amount and correct the charge mixing for each imaging.

(Second Embodiment)
FIG. 7 is a block configuration diagram of an imaging apparatus equipped with the detection apparatus according to the second embodiment of the present invention. Here, the description of the same configuration as that of the imaging device in the first embodiment is omitted.
In FIG. 6, analog signals are converted into digital signals by A / D conversion means 111A and 111B, and their outputs are output to dummy data detection means 133A and 133B, image signal detection means 135A and 135B, and charge mixture correction means 113A and 113B. The

  In this embodiment, the dummy data detection means 133A, 133B and the image signal detection means 135A, 135B correspond to charge mixing amount detection means, and the dummy data detection means 133A, 133B are the dummy data portion shown in FIG. The dummy data DM1A which is the first pixel is integrated. One dummy first pixel exists in each of the left and right channels in each horizontal period. Further, the image signal detection means 135A and 135B integrate the luminance level of the previous pixel 305A which gives a leak to the dummy data DM1A. The dummy data of the adjacent first pixel is also present in each pixel in the left and right channels in each horizontal period. Then, the integration result in the dummy data is read by the calculation means 145 as a detection value.

  In the control method of the image pickup apparatus in the present embodiment, as in the flowchart shown in FIG. 6, first, the exposure control means 157 changes the luminance of the light amount input to the image pickup surface of the CCD area sensor 103 (step S1) The dummy data detection means 133A, 133B detects the charge mixing amount of the first dummy pixel with respect to the luminance of each input light quantity, and the detection result is stored in the storage means 163 (step S2). Subsequently, based on the detection result of the charge mixing amount of the first dummy pixel in each dummy data detection unit 133A, 133B, correction for correcting the charge mixing component included in the output signal of the pixel in each region of the imaging surface A value is obtained by the calculation means 145 (step S3). Here, the correction value obtained by the computing means 145 is obtained according to the amount of dummy data at the signal level of a plurality of input light amounts. Thereafter, based on the correction amount obtained by the calculation means 145, the charge mixture correction means 113A and 113B correct the charge mixture component included in the output signal of the pixel in each region of the imaging surface (step S4).

In addition, using the detection device controlled as in steps S1 to S3, a timing table of correction values calculated by detecting the charge mixing amount before shipment from the factory is generated, and stored in the imaging device, for example, If the imaging apparatus is configured to perform image correction using this correction value at the time, a high-quality image without image quality deterioration can be obtained. Further, in this configuration, since the charge mixing amount is not detected during imaging, the processing speed can be increased. Furthermore, the configuration may be such that the detection device portion is provided in the imaging device (the detection device portion is not used during imaging after factory shipment), or is not provided inside the imaging device, but is provided in the imaging device at the time of factory shipment. It may be connected to detect the charge mixing amount.
Further, as in S1 to S4, the imaging apparatus may be configured to detect the charge mixing amount and correct the charge mixing for each imaging.

  As described above, in the present embodiment, the correction value can be obtained according to the dummy data amount at the signal level of the plurality of input light amounts, so that a higher quality image can be obtained.

(Third embodiment)
FIG. 8 is a block configuration diagram of an imaging apparatus equipped with the detection apparatus according to the third embodiment of the present invention. Here, the description of the same configuration as that of the imaging device in the first embodiment is omitted.
The imaging apparatus of the present embodiment is provided with a temperature measuring unit 171 that measures the temperature of the CCD area sensor 103, and outputs temperature information measured by the temperature measuring unit 171 to the calculating unit 145.

  FIG. 9 is a characteristic diagram schematically illustrating a temperature change of the charge mixing amount (Leak) to the first dummy pixel with respect to the signal level (Signal) of the image signal of the imaging apparatus according to the present embodiment. According to actual measurement, the charge mixing amount (Leak) increases and decreases with the temperature change of the CCD area sensor 103, and the charge mixing amount decreases as the temperature increases.

Therefore, the following control process of the imaging apparatus is performed.
In the control method for the imaging apparatus according to the third embodiment, the processes in steps S1 and S2 illustrated in FIG. 6 are performed under a plurality of conditions having different temperatures. The temperature condition of the CCD area sensor 103 at this time is measured by the temperature measuring means 171.

  Subsequently, in step S3, the charge mixture component included in the output signal of the pixel in each region on the imaging surface is corrected based on the detection result of the charge mixture amount of the first dummy pixel in each dummy data detection unit 133A, 133B. A correction value to be obtained is obtained by the calculation means 145. The correction value obtained by the calculation means 145 is a correction amount obtained from the temperature information at the time of measurement and a dummy data amount corresponding to the temperature.

  Subsequently, in step S4, the temperature of the CCD area sensor 103 at the time of imaging is measured by the temperature measuring unit 171 and associated with the temperature information stored in the storage unit 145, and the charge mixture correcting unit 113A is based on the corresponding correction value. , 113B corrects the charge mixture component included in the output signal of the pixel in each area of the imaging surface. Here, when the temperature of the CCD area sensor 103 and the temperature information stored in the storage means 145 do not match, an interpolation calculation is performed from the correction amount corresponding to the plurality of stored temperature information to the temperature of the CCD area sensor 103. After the calculation means 145 performs the correction process.

In addition, using the detection device controlled as in steps S1 to S3, a timing table of correction values calculated by detecting the charge mixing amount before shipment from the factory is generated, and stored in the imaging device, for example, If the imaging apparatus is configured to perform image correction using this correction value at the time, a high-quality image without image quality deterioration can be obtained. Further, in this configuration, since the charge mixing amount is not detected during imaging, the processing speed can be increased. Furthermore, the configuration may be such that the detection device portion is provided in the imaging device (the detection device portion is not used during imaging after factory shipment), or is not provided inside the imaging device, but is provided in the imaging device at the time of factory shipment. It may be connected to detect the charge mixing amount.
Further, as in steps S1 to S4, the imaging apparatus may be configured to detect the charge mixing amount and correct the charge mixing for each imaging.

  As described above, in the present embodiment, the correction value can be obtained from the temperature information. Therefore, it is possible to perform correction adapted to the characteristic that the charge mixing amount decreases as the temperature increases.

It is a block block diagram of the imaging device in the 1st Embodiment of this invention. It is the schematic which shows the specific example of a CCD area sensor. It is the schematic which showed the output timing of the image signal of a CCD area sensor. It is a schematic diagram for demonstrating the mode of the electric charge mixing into an adjacent pixel. FIG. 6 is a characteristic diagram schematically illustrating a charge mixing amount (Leak) in a first dummy pixel with respect to a signal level (Signal) of an image signal of the imaging apparatus according to the first embodiment. It is a flowchart which shows the control method of an imaging device. It is a block block diagram of the imaging device in the 2nd Embodiment of this invention. It is a block block diagram of the imaging device in the 3rd Embodiment of this invention. FIG. 10 is a characteristic diagram schematically illustrating a temperature change of a charge mixing amount (Leak) to a first dummy pixel with respect to a signal level (Signal) of an image signal of an imaging apparatus according to a third embodiment. It is the schematic which shows the specific example of the conventional CCD area sensor. It is a schematic diagram of the horizontal transfer part in an imaging device.

Explanation of symbols

101 Lens 103 CCD area sensor (imaging device)
105A, 105B Buffer 109A, 109B CDS
111A, 111B A / D conversion means 113A, 113B Charge mixing correction means 123A, 123B Linearity correction means 129A, 129B Gain correction means 133A, 133B Dummy data detection means 145 Calculation means 147 Synthesis means 149 Camera signal processing means 151 Output terminal 157 Exposure Control means 163 Storage means

Claims (8)

Charge mixing amount detecting means for detecting a charge mixing amount generated when an image signal from each of the imaging regions of an imaging device having a plurality of imaging regions corresponding to a plurality of output terminals is transferred within the imaging device; ,
Calculating means for calculating a correction value corresponding to each of the plurality of output terminals based on a detection result of the charge mixing amount detecting means for correcting a charge mixing component included in an image signal from each imaging region; A detection apparatus comprising:   The image pickup device includes a transfer unit that transfers an image signal, and the charge mixing amount detection unit is configured to transfer the transfer unit without a signal in the transfer unit after the image signal is read from the transfer unit. The detection apparatus according to claim 1, wherein the charge mixing amount is detected from the dummy data read from the transfer unit by driving.   The detection apparatus according to claim 2, wherein the dummy data is read out immediately after the image signal is read out.   The detection device according to claim 1, wherein a direction in which an image signal of a pixel generated in the imaging region is transferred is a horizontal direction. A storage means for storing the detection result of the charge mixing amount detection means;
5. The detection apparatus according to claim 1, wherein the calculation unit calculates the correction value based on the detection result read from the storage unit. Exposure amount control means for continuously varying the exposure amount to the image sensor;
6. The charge mixing amount detection unit performs detection of the charge mixing amount in correspondence with a level of an image signal at each exposure amount varied by the exposure amount control unit. The detection apparatus according to item 1. A temperature measuring means for measuring the temperature of the image sensor;
The charge mixing amount detection means detects the charge mixing amount under a plurality of predetermined temperature conditions,
The calculation means performs the calculation of the correction value based on a detection result detected by the charge mixing amount detection means according to a temperature change based on a measurement result by the temperature measurement means. Item 7. The detection device according to any one of Items 1 to 6. A charge mixing amount detection step for detecting a charge mixing amount that occurs when an image signal is transferred from each imaging region of an imaging device having a plurality of imaging regions corresponding to a plurality of output terminals;
And a calculation step of calculating a correction value for correcting a charge mixture component contained in the transferred image signal based on a detection result in the charge mixture amount detection step.

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