JP2000217039A - Point defect detection method and point defect pixel value correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a point defect detection method by which a point defect can be detected without the need for any exclusive circuit and that is used for a picture signal processor. SOLUTION: A digital still camera picks up a light emitted from a color viewer (processing 16). A CPU 10 divides picture data into a plurality of blocks and divides each block by each color of complementary group color filters provided to an entire face of each pixel of a CCD (processing 17). Comparison between a mean value of a block to which a target pixel belongs and a pixel value of the target pixel is made to all pixels of the picture data, and when the pixel value of the target pixel is smaller than the mean value by 20% or over (YES in processing 19), a count of a detected number counter (not shown) is incremented by one (processing 20) and a temporary storage memory 7 temporarily stores a pixel position (address) of a detected pixel (point defect) (processing 21).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a point defect detection method and a point defect pixel value correction method, and more particularly to a point defect detection method and a point defect pixel value correction method used in an image signal processing device.

[0002]

2. Description of the Related Art A solid-state imaging device represented by a CCD (Charge Coupled Device) is one of sensors for converting optical information into an electric signal. It is necessary to select an image sensor.
Taking a CCD, which is a typical solid-state imaging device, as an example, items that determine the quality of the CCD include the presence or absence of dip points (black points) and peak points (bright points) called point defects.

[0003] When the output level of the solid-state image pickup device is quantized, if the above-mentioned point defects (dip point and peak point) are present, the image quality is significantly impaired as a result. For this reason, the output level of each pixel when a uniform amount of light is given to the solid-state imaging device is determined in advance as a standard, and a solid-state imaging device including a pixel having an output level that affects image quality is excluded from the product. . However, in recent years, in the field of video signal processing devices, the number of pixels of the solid-state imaging device has been increased, and the above management method significantly reduces the yield.

[0004] Techniques for solving this problem are disclosed in Japanese Patent Application Laid-Open Nos. 61-222381 and 61-222.
382. In the video signal processing devices disclosed in these publications, a dedicated circuit for detecting a point defect of the solid-state imaging device is provided to detect the point defect and correct the pixel value of the point defect position.
As a result, the solid-state imaging device can be used without being selected.

[0005]

However, the above-described video signal processing apparatus requires a dedicated circuit for detecting a point defect. For this reason, the cost of the video signal processing device itself is increased, which hinders the cost reduction of the video signal processing device due to the cost reduction of the solid-state imaging device itself, which is one of the effects of solid-state imaging device non-selection.

It is also important to accurately detect a point defect without being affected by shading by a lens.

Further, when a plurality of color filters are provided on the front surface of the solid-state image sensor, the point defect can be accurately obtained without being affected by the difference in the output of the solid-state image sensor due to the difference in the color of the color filter. It is also important to detect

[0008] The present invention has been made to solve the above-described problems, and its purpose is to eliminate the need for a dedicated circuit,
An object of the present invention is to provide a point defect detection method and a point defect pixel value correction method used in an image signal processing device capable of detecting a point defect.

Another object of the present invention is to provide a point defect detection method used in an image signal processing device capable of detecting a point defect without being affected by shading.

Still another object of the present invention is to provide a point defect detection apparatus used in an image signal processing apparatus capable of detecting a point defect without being affected by a difference in output of a solid-state image sensor due to a difference in color filter. Is to provide a way.

[0011]

According to a first aspect of the present invention, there is provided a method for detecting a point defect, comprising: receiving a light incident through a lens; and converting the received light into an analog electric signal. A solid-state imaging device; an A / D converter for converting an analog electric signal obtained from the solid-state imaging device into digital signal image data; and a first connected to the A / D converter for storing the image data. , A second memory for storing the position of a point defect, and a CPU connected to the first and second memories for detecting a point defect among pixel values of image data. Used in image signal processing devices. The point defect detection method receives uniform light,
Converting the received light into an analog electrical signal;
Converting the analog electric signal into image data of a digital signal; dividing the image data into a plurality of blocks of a predetermined size; and for each of the plurality of blocks, a pixel value of a pixel included in the block. From the step of obtaining a value representative of the block, and for each pixel included in the image data, comparing the pixel value of the pixel and the value representative of the block to which the pixel belongs,
If the two have a predetermined relationship, determining the pixel as a point defect and storing the position of the pixel in the second memory.

The process of detecting a point defect is executed by a CPU provided in the image signal processing device. Therefore, it is possible to detect a point defect without providing special hardware. Accordingly, it is possible to suppress an increase in cost of the image signal processing device. Further, the detection of the point defect is performed for each block obtained by dividing the image data into a plurality. Therefore, it is possible to detect a point defect without being affected by shading by the lens.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the image signal processing apparatus further includes a plurality of types of color filters provided on a front surface of the solid-state imaging device. Dividing the image data into a plurality of blocks of a predetermined size, and dividing each of the plurality of blocks into a plurality of blocks each including a pixel provided with a color filter of the same color. Performing the steps.

Each of the plurality of filters is further divided into different pixels of the color filter. Therefore, the point defect can be detected without being affected by the difference in the output of the solid-state imaging device due to the difference in the color filter.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the step of obtaining a value representative of a block includes the steps of:
Calculating a mean value of the pixel values of the pixels included in the block.

According to a fourth aspect of the present invention, there is provided a method for correcting a point defect pixel value, comprising: a lens; a solid-state imaging device for receiving light incident through the lens and converting the received light into an analog electric signal; An A / D converter for converting an analog electric signal obtained from the element into image data of a digital signal; a first memory connected to the A / D converter for storing the image data; A second memory for storing the position, connected to the first and second memories;
It is used in an image signal processing apparatus including a CPU for correcting a pixel value of a point defect among pixel values of image data. The point defect pixel value correction method includes a step of receiving incident light by a solid-state connection element and converting the received light into an analog electric signal, and converting the analog electric signal into digital signal image data by an A / D converter. The step of converting includes the step of correcting the pixel value of the point defect from the pixel value of a pixel having a predetermined positional relationship with the point defect by the CPU.

The correction of the pixel value of the point defect is executed by a CPU provided in the image signal processing device. Therefore, the pixel value of the point defect can be corrected without providing special hardware for correcting the pixel value of the point defect. Therefore, an increase in cost of the image signal processing device can be suppressed.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the step of correcting the pixel value of the point defect includes the step of correcting the pixel value of the point defect and a predetermined positional relationship with the point defect. A step of calculating a median of pixel values of a certain pixel; and a step of replacing a pixel value of a point defect with a median.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital still camera according to one embodiment of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, digital still camera 1
3 receives the lens 1 and the light imaged by the lens 1,
An interline type CCD 2 using a complementary color filter for converting received light into an analog electric signal, and a CCD
2, a CCD driving unit 6 for driving the CCD 2, an amplifier 3 connected to the output of the CCD 2 for amplifying an analog electric signal, and an amplified analog electric signal connected to the output of the amplifier 3. A / D (Analog to Digital) for converting image data into digital signal image data
A converter 4, a signal processing unit 5 for obtaining a luminance signal and a color difference signal from image data stored in a temporary storage memory 7 described later or image data output from the A / D converter 4, and A / D conversion A temporary storage memory 7 for receiving and temporarily storing the image data output from the device 4 via the signal processing unit 5 and a JPEG (Jo) for the luminance signal and the color difference signal.
int Photographic Experts Group) JPEG processing unit 9 for performing compression processing to obtain compressed data and performing JPEG expansion processing on the compressed data to obtain luminance signals and color difference signals, and image storage memory 1 for storing compressed data.
1, a video encoder 8 for converting a luminance signal and a color difference signal obtained by performing JPEG decompression processing by a JPEG processing unit 9 into a video signal, and a video signal output from the video encoder 8 for display. A display device (not shown) and a CPU for executing processing for detecting a point defect and correcting the pixel value of the point defect
(Central Processing Unit) 10, a control program / adjustment data storage memory 12 for storing a control program executed by the CPU 10, and adjusting data used for correcting a pixel value of a point defect, and a signal Processing unit 5, temporary storage memory 7, video encoder 8, JP
A bus for interconnecting the EG processing unit 9, the CPU 10, the image storage memory 11, and the control program / adjustment data storage memory 12 is included.

The number of effective pixels of the image data is 1290 × 96
6 pixels, and the number of pixels of data to be actually captured is 12
It is 88 × 963 pixels.

Referring to FIG. 2, a point defect detection device for detecting point defects and obtaining adjustment data is a color viewer 15 that emits light with a uniform light amount over the entire surface and a light that is emitted by color viewer 15 in close-up. The digital still camera 13 includes a digital still camera 13 disposed at a position, and a host computer 14 connected to the color viewer 15 and the digital still camera 13 for controlling the color viewer 15 and the digital still camera 13.

Referring to FIG. 3, each part of the point defect detection device operates as follows. In accordance with an instruction from the host computer 14, the color viewer 15 emits light with a predetermined light amount. Further, the digital still camera 13 captures light emitted by the color viewer 15 in accordance with an instruction from the host computer 14. At this time, the shutter speed is predetermined so that the analog electric signal output from the CCD 2 is not saturated. The aperture value is set to the maximum value in order to suppress the influence of shading by the lens 1. C
The analog electric signal output from the CD 2 is amplified by the amplifier 3 and converted into 10-bit digital signal image data by the A / D converter 4. The image data is stored in the temporary storage memory 7 (process 16).

The CPU 10 divides the image data stored in the temporary storage memory 7 into blocks having a size as shown in FIG. The number of divisions is a total of 2 blocks of 16 blocks each
There are 56 blocks. Further, each block is divided for each color of a complementary color filter as shown in FIG. 5 provided in front of each pixel of the CCD 2. As complementary color filters,
There are four types, G (green), Mg (magenta), Ye (yellow), and Cy (cyan), and the image data stored in the temporary storage memory 7 is finally divided into 1024 blocks (processing 17). .

The average value of the pixel values in each block of the 1024 blocks divided in the process 17 is obtained (process 18). For all the pixels of the image data, the average value of the block to which the pixel of interest belongs is compared with the pixel value of the pixel of interest, and whether the pixel value of the pixel of interest is at least 20% smaller than the average value Is determined (process 19). If the pixel value of the pixel of interest is at least 20% smaller than the average value (YES in process 19), the value of the detected number counter (not shown) is incremented by one (process 20), and the detected pixel (dip point) Is temporarily stored in the temporary storage memory 7 (process 21). After the processing 21 is completed, or when the pixel value is 20 times smaller than the average value.
If it is not smaller than% (NO in step 19), it is determined whether or not all pixels included in the image data have been compared with the average value (step 22). If there is a pixel for which comparison processing has not been performed (NO in processing 22), comparison processing is performed for a pixel for which comparison processing has not been performed (processing 19).
Perform

If the comparison process has been completed for all the pixels (YES in process 23), it is determined whether the value of the detected number counter is within a predetermined standard value (process 23). If the value of the detected number counter is within the standard value (YES in step 23), the pixel position (address) of the dip point temporarily stored in the temporary storage memory 7 is stored in the control program / adjustment data storage memory 12 (flash memory). (Process 24), and the process ends. If the value of the detected number counter is larger than the standard value (N in step 23)
O), it is determined that the CCD 2 is a nonstandard product (process 2).
5) The CPU 10 transmits data to the host computer 14 that the CCD 2 is a nonstandard product (process 26). The peak point is detected according to the same procedure except that it is determined in step 19 whether the pixel value of the target pixel is larger than the average value by 20% or more.

Next, a method of correcting the pixel value of the dip point when an image is photographed by the digital still camera 13 will be described with reference to FIG.

The captured image is captured, and the digitized image data is stored in the temporary storage memory 7 (process 27). The CPU 10 reads the pixel position of the dip point from the control program / adjustment data storage memory 12 (process 28). The CPU 10 determines whether or not there is data at the pixel position of the dip point (process 29). If it is determined that the data at the pixel position of the dip point exists (YES in the process 29), one of the dip points is selected and the pixel value of the pixel is read from the temporary storage memory 7. Further, a pixel value of a filter pixel having the same color as the dip point and adjacent to the dip point of interest is read from the temporary storage memory 7 (process 30). For example, when the dip point is a green complementary color filter pixel, the arrangement of adjacent pixels is 8 as shown in FIG.
One pixel. However, when the dip point is located at the end of the image data, only five pixels may be obtained as shown in FIG. 7B.

The read dip points and the pixel values of the adjacent pixels are sorted in descending order (process 31). When the total number of dip points and adjacent pixels is N, (N / 2 + 1)
The next largest pixel value (that is, the median value) is selected as interpolation data (processing 32), and the pixel value of the dip point is processed as processing
Replace with the interpolation data selected in step 1 (process 33). It is determined whether or not pixel value interpolation has been performed for all dip points (process 34). If there are more dip points to be interpolated (NO in process 34), processes 31 to 31 are performed to perform the interpolation process on the dip points that have not been interpolated.
Repeat 33.

If there are no more dip points to be interpolated (YES in step 34), or if there are no dip points in the original (NO in step 29), the signal processing unit 5 outputs a luminance signal and a color difference from the interpolated image data. A signal is obtained (process 35).
The JPEG processing unit 9 performs JPEG compression processing on the obtained luminance signal and color difference signal (processing 36). The compressed data is written to the image storage memory 11 (process 37),
A series of processing ends. The correction of the pixel value at the peak point is performed according to the same procedure.

As described above, according to the present embodiment, the existing digital still camera can be used without providing hardware for newly detecting a dip point and hardware for correcting the pixel value of the dip point. The use of the camera 13 enables detection of a dip point and correction of the pixel value of the dip point. Therefore, an increase in the cost of the digital still camera 13 can be suppressed. In addition, by increasing the allowable range for selecting the non-defective products of the CCD 2, it is possible to improve the yield and reduce the cost in manufacturing the CCD 2.

A dip point is detected for each block obtained by dividing the image data into a plurality. Therefore, it is possible to detect a point defect without being affected by shading by the lens.

Further, the color filters applied to the pixels included in each block have the same color. Therefore, the point defect can be detected without being affected by the difference in the output of the CCD 2 due to the difference in the color filter.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital still camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a point defect detection device.

FIG. 3 is a flowchart of a dip point detection process.

FIG. 4 is a diagram illustrating image data after being divided into a plurality of blocks.

FIG. 5 is a diagram showing an arrangement of complementary color filters.

FIG. 6 is a flowchart of a pixel value correction process for a dip point.

FIG. 7 is a diagram illustrating adjacent pixels of the same color.

[Explanation of symbols]

 Reference Signs List 1 lens 2 CCD 3 amplifier 4 A / D converter 5 signal processing unit 6 CCD driving unit 7 temporary storage memory 8 video encoder 9 JPEG processing unit 10 CPU 11 image storage memory 12 control program / adjustment data storage memory

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5B047 AB02 AB04 CB30 DA06 DC06 5C024 AA01 BA01 CA09 DA01 EA04 EA08 FA01 GA16 HA08 HA12 HA14 HA18 HA23 HA24 5C065 AA03 BB23 CC03 CC08 CC09 DD07 DD17 EE07 EE10 EE12 GG13 GG17 GG32

Claims (5)

[Claims] 1. A lens, a solid-state imaging device for receiving light incident through the lens, and converting the received light into an analog electric signal, and a digital signal for converting the analog electric signal obtained from the solid-state imaging device. An A / D converter connected to the A / D converter, a first memory for storing the image data, and a second memory for storing the position of the point defect A point defect detection method used in an image signal processing device, comprising: a memory; and a CPU connected to the first and second memories and configured to detect a point defect among pixel values of image data, Receiving uniform light, converting the received light into an analog electric signal, converting the analog electric signal into digital signal image data, and converting the image data to a predetermined size. Dividing each block into a plurality of blocks; obtaining a value representative of the block from the pixel values of the pixels included in the block for each of the plurality of blocks; Comparing the value with a value representative of a block to which the pixel belongs, and if the two have a predetermined relationship, determining the pixel as a point defect and storing the position of the pixel in the second memory. Including, point defect detection method. 2. The image signal processing apparatus further includes a plurality of types of color filters provided on a front surface of the solid-state imaging device, and the step of dividing the image data into a plurality of blocks includes a step of dividing the image data into a predetermined size. 2. The point defect detection method according to claim 1, further comprising: dividing the plurality of blocks into a plurality of blocks each including a pixel provided with a color filter of the same color. . 3. The point according to claim 1, wherein the step of obtaining a value representing the block includes the step of obtaining, for each of the plurality of blocks, an average value of pixel values of pixels included in the block. Defect detection method. 4. A lens, a solid-state imaging device for receiving light incident through the lens, and converting the received light into an analog electric signal, and a digital signal for converting the analog electric signal obtained from the solid-state imaging device. An A / D converter connected to the A / D converter for storing image data; and a second memory connected to the A / D converter for storing the position of the point defect. A memory connected to the first and second memories for correcting a pixel value of a point defect among pixel values of image data;
A point defect pixel value correction method used in an image signal processing device including a PU, wherein the solid-state connection element receives incident light, and converts the received light into an analog electric signal; A step of converting an analog electric signal into digital signal image data by a D converter; and a step of correcting a pixel value of a point defect from a pixel value of a pixel having a predetermined positional relationship with the point defect by the CPU. , Point defect pixel value correction method. 5. The method of correcting a pixel value of a point defect, comprising: calculating a pixel value of the point defect and a median of pixel values of pixels having a predetermined positional relationship with the point defect; The point defect pixel value correcting method.