JP2000059690A - Electronic camera and signal correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic camera and a signal correcting method with which a white flaw increased/decreased corresponding to exposure time can be appropriately corrected. SOLUTION: This camera has a CCD 1 having plural pixels, memory 9 for storing information on the defective pixel of the CCD 1 and control circuit 8 for detecting whether a concerned pixel is defective or not by comparing information on the concerned pixel with prescribed information. Therefore, by correcting the pixel defect based on the previously stored information on the defective pixel at the time of short-time exposure, for example, such correction can be speedily performed. At the time of long-time exposure, on the other hand, the defective pixel is detected by the control circuit 8 so that information on the defective pixel to be stored can be reduced. Therefore, since a small storage capacity is enough for the memory 9, the cost of the digital still camera can be suppressed low, and further, data sampling time concerning the defective pixel in the production process of the digital still camera is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for detecting a defective pixel of a solid-state imaging device and correcting an output signal from the defective pixel in an electronic camera having the solid-state imaging device.

[0002]

2. Description of the Related Art A solid-state imaging device provided in an electronic camera converts an optical image of a subject formed on a pixel into a charge (electric signal) by using a large number of pixels arranged two-dimensionally and outputs the charge. It has the function to do. By the way, some of such pixels may not be able to output a normal signal because they have a defect (pixel defect) based on dust adhesion, crystal defect or the like. For such a pixel defect, a signal that is obtained by adding an extra signal component to an output signal that should be output in accordance with the luminance of the subject is output, and a white flaw that makes the image whitish, There is a black flaw that outputs a signal obtained by subtracting a certain signal component from an output signal that should be output in accordance with the luminance, thereby making an image blackish.

[0003] When many pixel defects occur, there is a possibility that the image quality will be remarkably deteriorated when reproducing an image picked up using such a solid-state image pickup device. On the other hand, since a solid-state imaging device that has recently been used has at least several hundred thousand pixels, it can be said that it is actually difficult to manufacture a solid-state imaging device having no pixel defect. Therefore, it is required to use a solid-state imaging device on the assumption that a certain amount of pixel defects always exist.

[0004] On the basis of such a premise, an electronic camera which has a correction circuit for correcting an electric signal output from a pixel having a pixel defect by post-processing to improve the image quality has already been developed. According to such an electronic camera, in a production process of the electronic camera, a pixel having a pixel defect (defective pixel) of the solid-state imaging device is detected using a pixel defect inspection device, and the position is mounted on the electronic camera, for example. RO
By storing the information in M, the output signal from the defective pixel is appropriately corrected at the time of actual imaging.

[0005]

However, it has been found that the above-mentioned white flaw is a pixel defect based on a crystal defect, and may increase depending on the use environment of the solid-state imaging device. For example, white flaws tend to increase as the exposure time increases. In such a case, since a new defective pixel is generated at a position different from the position of the defective pixel detected under a certain condition in the production process of the electronic camera, sufficient correction may not be performed. On the other hand, by performing long-time exposure during inspection in the production process of the electronic camera, defective pixel information is obtained in advance,
It is also conceivable to correct the signal of the defective pixel based on such information when actually photographing.

[0006] However, the number of defective pixels caused by white flaws increases dramatically as the exposure time increases, and their positions are not necessarily unchanged. Therefore, the position (coordinates) of such pixels and the exposure time are reduced. In order to store the information indicating the relationship, a large storage capacity is required in the ROM of the electronic camera. Also, in the production process of an electronic camera, when performing long-time exposure and collecting data on defective pixels, the same must be repeated, for example, taking an average value of three times. Therefore, assuming that the long-time exposure is 4 seconds at the maximum, the time required for data collection is only 12 hours.
This means that seconds are required, and the conventional data collection time is 1 second or less, which takes 10 times or more.

An object of the present invention is to provide an electronic camera and a signal correction method capable of appropriately correcting white flaws that increase or decrease according to the exposure time in view of the problems of the related art.

[0008]

In order to achieve the above object, an electronic camera according to the present invention comprises: a solid-state imaging device having a plurality of pixels; storage means for storing information on defective pixels of the solid-state imaging device; Detecting means for detecting whether or not the pixel of interest is a defective pixel by comparing information on the pixel of interest with predetermined information.

According to the electronic camera of the present invention, a solid-state imaging device having a plurality of pixels, storage means for storing information on defective pixels of the solid-state imaging device, and information on a pixel of interest are compared with predetermined information. Detecting means for detecting whether or not the pixel of interest is a defective pixel, and identifying a defective pixel from information on the defective pixel stored in the storage means, based on information on the exposure time at the time of shooting, or Determining means for determining whether to detect a defective pixel by the detecting means.

A signal correction method according to the present invention is a signal correction method for an electronic camera having a solid-state imaging device, wherein the exposure time of the electronic camera is one of a first exposure time and a second exposure time. Determining whether the exposure time is the first exposure time, and identifying a defective pixel based on information about the defective pixel of the solid-state imaging device stored in advance, while the exposure time is the first exposure time. When the exposure time is 2, the method includes a step of comparing the information on the target pixel with predetermined information to detect a defective pixel, and a step of correcting an output signal from the detected defective pixel. Features.

[0011]

According to the electronic camera of the present invention, a solid-state image sensor having a plurality of pixels, storage means for storing information on defective pixels of the solid-state image sensor, and information on a target pixel are compared with predetermined information. Accordingly, since the detection unit detects whether or not the pixel of interest is a defective pixel, for example, at the time of short-time exposure, the pixel defect is corrected based on the information on the defective pixel stored in advance. Then, such correction processing can be performed quickly. On the other hand, at the time of long-time exposure, if a defective pixel is detected by the detection means, the information on the defective pixel to be stored is reduced, and the storage capacity of the storage means is small. Can be suppressed, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

According to the electronic camera of the present invention, the solid-state imaging device having a plurality of pixels, storage means for storing information on defective pixels of the solid-state imaging device, and information on the target pixel are compared with predetermined information. Thus, based on the information on the exposure time at the time of photographing, whether the target pixel is a defective pixel or not, based on the information on the defective pixel, Or a determining means for determining whether to detect a defective pixel by the detecting means. For example, at the time of short-time exposure, it is possible to correct a pixel defect based on information about a defective pixel stored in advance. Correction processing can be performed quickly. On the other hand, at the time of long exposure, if the determining means determines that the defective pixel is detected by the detecting means, the information on the defective pixel to be stored is reduced, and therefore the storage capacity of the storage means is small. In addition, the cost of the electronic camera can be kept low, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

According to the signal correction method of the present invention, it is determined whether the exposure time of the electronic camera is either the first exposure time or the second exposure time; When the exposure time is, the defective pixel is specified based on the previously stored information on the defective pixel of the solid-state imaging device. On the other hand, when the exposure time is the second exposure time, the information on the pixel of interest is Since the method includes a step of detecting a defective pixel by comparing with predetermined information and a step of correcting an output signal from the detected defective pixel, for example, the first exposure time is determined to be short and stored in advance. If the output signal from the defective pixel is corrected based on the information on the defective pixel, the correction process can be performed quickly. On the other hand, if the second exposure time is determined to be a long exposure time and the information on the pixel of interest is compared with predetermined information to detect defective pixels, the information on defective pixels to be stored is reduced. Since the storage capacity of the means is small, the cost of the electronic camera can be kept low, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a digital still camera as an electronic camera according to the first embodiment. In FIG. 1, a CCD (Charge Coupled De) as a solid-state imaging device is shown.
image) The image sensor 1 performs so-called photoelectric conversion, which converts an optical image of a subject formed on the pixel into an electric signal (generates a charge), and the drive circuit 2 generates a transfer pulse. It is a circuit that generates and supplies it to the CCD 1. The CCD 1 outputs an analog electric signal based on the transfer pulse generated by the drive circuit 2.

The CDS (correlated double sampling) circuit 3 is a circuit for reducing noise, and is driven based on a driving pulse output from the driving circuit 2. The A / D conversion circuit 4 converts an input analog signal into a digital signal and outputs the digital signal. In the A / D conversion circuit 4 according to the present embodiment, it is assumed that the higher the intensity of the light incident on the pixels on the CCD 1, the larger the value of the light is converted to a digital signal. Image data for each pixel of the CCD 1 obtained through the A / D conversion circuit 4 is temporarily
It is stored in the image memory 5.

The image data stored in the image memory 5 is subjected to various types of image processing by the CPU 6, and is finally stored in a recording unit 7 composed of a recording medium such as a memory card, a magneto-optical disk, or the like.

Here, the various types of image processing include a process of correcting image data of defective pixels of the CCD 1. As will be described later, the CPU 6 detects a defective pixel and corrects the image data of the defective pixel in a manner corresponding to the exposure time as described later. Note that various data used for detecting a defective pixel is also stored in the memory 9.

The liquid crystal display device 10 displays a captured image, necessary operation information, and the like. On the front surface of the CCD 1, a lens 11 for imaging light from a subject on a pixel, an aperture 12 for adjusting the amount of incident light, and a CCD
And a temperature sensor 13 for detecting the temperature of the temperature sensor 1. The detection signal of the temperature sensor 13 is input to the control circuit 8.

Further, a distance measuring means (not shown) to the subject is provided, and the control circuit 8 drives the lens driving circuit 14 to move the lens 11 to a focus position by a signal from the distance measuring means. It has become. Further, a power switch 15 and a mode switch 16 (mode selection means) for selecting a detection mode for detecting a pixel defect are provided, and a signal based on the operation of the switch is input to the control circuit 8. Has become. On the other hand, the timer 17
Are connected to the control circuit 8. Timer 17 is a CCD
The exposure time at the time of imaging 1 is detected, and a signal corresponding to the exposure time is output to the control circuit 8. The diffuser plate 21 is used when detecting a black flaw, and is not used when detecting a white flaw.

Next, detection of a white defect as a defective pixel will be described. The white flaw detection is performed in the production process of the digital still camera, and the obtained detection result is stored in the memory 9 of the control circuit, and the detection result is used for white flaw correction at the time of actual imaging. It has become. However, if the mode switch 16 is turned on in order to cope with white spots that increase with time, the detection may be performed each time the power is turned on, and the detection result may be updated.

A description will be given of an aspect of white defect detection in the production process of a digital still camera. First, mode switch 1
When the power switch 15 is turned on with the switch 6 turned on, the switch signal is input to the control circuit 8, and the control circuit 8 drives the aperture 12 (light amount adjusting means) to be fully closed. An image is taken for one screen while limiting the incident light (control means). C by such imaging
The output from the CD 1 is stored in the image memory 5,
U6 compares a threshold value (reference data) for white defect determination stored in the memory 9 in advance with image data of each pixel, that is, an output signal. Note that the reference data can be obtained by averaging the peripheral data of the pixel to be detected, using captured image data.

The method for obtaining the reference data will be described below with reference to the drawings. First, consider a case where four color filters as shown in FIG. 2 are arranged for each pixel. FIG. 3 is a diagram showing a state in which the color filters are two-dimensionally arranged, but only the color A is displayed for easy understanding.

In FIG. 3, for reference pixel AA, reference data is calculated using data of 24 pixels of the same color (color A) in the target pixel in an area of nine surrounding pixels. . First, a data average value of 24 pixels is obtained. This average value is used as first reference data for this pixel. The data of the pixel of interest is compared with the first reference data, a difference between them is obtained, and this difference is set as a defect level. If the flaw level exceeds a predetermined range, the flaw is recognized as a flaw and its position information is stored in a memory. Similar processing is performed for the other colors (B, C, and D colors). Similar processing is performed for all pixels.

At this time, the flaw level to be detected is not limited to the same range for all the image data. Instead, a certain area may be divided and detected by a different standard for each area. For example, dividing the screen into a central part and a peripheral part,
The central part is less than 5%, the peripheral part is less than 10%,
The conditions for flaw detection can be changed. The percentage at this time is the ratio of the defect level to the data average value of the 24 pixels around the target pixel.

When a plurality of single-color filters are used as the color filters, all the pixels adjacent to the target pixel can be used in the same manner as in the case of a monochrome image sensor. FIG. 4 is a diagram showing this example. For example,
All parts of B can be used for the target pixel BB. In the calculation, similarly, the data average value of the peripheral pixels may be obtained, and this may be used as the first reference data. In the case of detecting white spots during long-time exposure, the processing speed can be improved by limiting the peripheral pixels to be compared to, for example, five pixels around the target pixel. Further, the range of the peripheral pixels may be a rectangle (for example, 5 × 9 pixels) instead of a square.

In this manner, the reference data, ie, the threshold value, is obtained. However, according to the above-described imaging, since the incident light does not reach the pixels of the CCD 1, as long as the pixels are normal, the output signals from the pixels are not affected. Should be less than the threshold. Therefore, when the output signal is equal to or larger than the threshold, it is determined that there is a defect corresponding to a white defect. The white defect is detected by such a comparison. If a white defect is detected, the position information (two-dimensional coordinates) of the corresponding defective pixel is stored in the memory 9 (storage means) of the control circuit 8.

If the detection of white flaws is automatically performed each time the power switch 15 is turned on, the latest white flaw position information is stored in the memory 9. Can be corrected in accordance with the change of.

When the exposure time is, for example, 1/8 second or less, the position of the white flaw is relatively small.
Even if a white flaw is detected in the production process of the digital still camera and such a position is stored in the memory 9, the storage capacity is small. However, if the exposure time is longer than 1/8 second, white flaws increase dramatically,
In the production process of the digital still camera, there is a problem that it takes a long time to detect a white defect, and a problem that a large storage capacity is required because the position of the white defect is stored in the memory 9.

Therefore, in the present embodiment, in the production process of the digital still camera, white flaws are detected only when the exposure time is 1/8 second or less. I remember. Further, when the exposure time during actual imaging is 1/8 second or less, the memory 9
In the case where the exposure time exceeds 1/8 second, the detection and correction of flaws are performed while processing the image data obtained by imaging. Like that. Note that ideally, before and after imaging, C
It is desirable to detect the white flaw by restricting the light incident on the CD 1, but it is also possible to detect the white flaw from the image data. In the present embodiment, such a detection mode is adopted. If attention is paid only to the periphery of the target pixel, there is no significant change in the data between the pixels. Therefore, a defect can be detected by comparing the average of the peripheral pixels with the data of the target pixel. More specifically, the operation of the present embodiment will be described.

FIG. 5 is a flowchart showing a process for actually photographing a subject using the electronic camera according to the present embodiment, and FIG. 6 is a subroutine for performing signal processing and flaw correction processing.

First, in step S101 of FIG.
When the user turns on the power switch 15 (power ON), the flow starts. The switch SW1 is turned on (ON) when the user half-presses a shutter button (not shown), and the switch SW2 is turned on (ON) when the user fully presses the shutter button.

In step S102, the switch SW
When the switch 1 is not turned on, the electronic camera is maintained in a standby state. However, when the switch SW1 is turned on, in the next step S103, the exposure control by the control circuit 8 is performed, and the necessary aperture value and shutter speed are determined. , Exposure time T
Is determined.

In the following step S104, the control circuit 8 obtains the distance to the object by a distance measuring circuit (not shown), and drives the lens 11 to the in-focus position by the lens driving circuit 14.

In step S105, when the switch SW2 is not turned on (that is, the shutter button is not fully pressed), the digital still camera is kept in a standby state. In, the shutter is driven by the control circuit 8, and the exposure is performed for the exposure time T.

After the charges are accumulated in the CCD 1 by the exposure, the charges are transferred in step S107. The charges transferred in this manner are stored as image data for each pixel in the A / D converted image memory 5.

In step S108, it is determined whether the exposure time T is longer than 1/8 second. If the exposure time T is longer than 1/8 second, the flow moves to step S109,
The subroutine of signal processing and flaw correction processing shown in FIG. 6 is started. First, in step S109a, the stored image data is read in a 5 × 5 pixel area. In the following step S109b, a flaw is detected. More specifically, the difference between the pixel signal of the target pixel (the center of the 5 × 5 pixel area) and the pixel signal of the peripheral pixel is obtained. In step S109c, if the difference is larger than the threshold value, it is determined that the pixel of interest is a defective pixel (that is, there is a flaw). If there is a flaw, flaw correction is performed in step S109d in a manner described later. On the other hand, if there is no flaw, the signal processing is performed as it is (step S109e). The above processing is performed while sequentially changing the pixel area (step S109).
g) If it is determined that the detection has been completed for the last data after performing for all the pixels (step S109)
f), the flow is returned to step S112 in FIG. In addition, since white flaw detection and correction are performed while processing image data, the time until completion of white flaw correction is relatively long, but the user should be fully aware of long exposure. It is thought that even if the processing time is long, it does not matter much.

On the other hand, in step S108 of FIG.
If it is determined that the exposure time T is 秒 second or less, the data as the detection result of the corresponding white flaw is stored in the memory 9, and such data is read to correct the white flaw. (Step S110). Such correction is performed quickly because the pixels to be corrected are stored in advance. Thereafter, in step S111, signal processing is performed on the pixel data.

In step S112, the image data subjected to the signal processing as described above is compressed. The control circuit 8 finally records an image in the recording unit 7 in step S113, and thereafter returns the flow to step S102.

Next, the manner of correcting white spots in steps S109d (FIG. 6) and step 110 (FIG. 5) will be described. The control circuit 8 determines in step S10
9b (FIG. 6) or the charge amount in the image data stored in the image memory 5 corresponding to the defective pixel specified in step S110 (FIG. 5) is corrected in a manner described later.

In the correction of the image data in the present embodiment, the charge amount of the defective pixel is newly obtained by averaging the charge amounts of the pixels adjacent to the defective pixel. . However,
It is also possible to correct image data by adding, subtracting, multiplying, and multiplying a correction value with respect to a charge amount from a defective pixel, or by multiplying and multiplying a correction term.

First, as shown in FIG. 7, the color mosaic filters provided in the CCD 1 in advance are A, B, C, D
In the case of four color filters (for example, Ye, Cy, G, and Mg), the control circuit 8 controls the defective pixels A _{n, n}
Is calculated based on one of the following formulas. The symbols A _{n and n} described later mean the amounts of charges applied to the filter color A (that is, Ye) of the pixel in the n-th column and the n-th row.

(I) First Calculation Formula _{An, n} = (A _{n−2, n−2} + A _{n−2, n} + A _{n−2, n + 2} + A _{n, n−2} + A _{n, n + 2} + _{An + 2, n-2} + _{An + 2, n} + _{An + 2, n + 2} ) / 8 (1) (ii) Second calculation formula _{An, n} = ( _{An-2, n} + A) _{n, n−2} + A _{n, n + 2} + A _{n + 2, n} ) / 4 (2) (iii) Third calculation formula _{An, n} = (A _{n, n−2} + A _{n, n + 2} ) / 2 or ( _{An-2, n} + _{An + 2, n} ) / 2 (3)

According to the average of the above equation (1), within the 5 × 5 pixel area centered on the defective pixel, the average value of the charge amounts of the eight pixels provided with the color filters of the same color as the defective pixel is calculated as:
Since the charge amount of the defective pixel is replaced with the charge amount of the defective pixel, the change in the charge amount of such a pixel and the charge amount of an adjacent pixel become natural, whereby the image quality can be improved.

According to the average of the above equation (2), a pixel provided with a color filter of the same color as the defective pixel in a 5 × 5 pixel area centered on the defective pixel and having the same column as the defective pixel In addition, the average value of the charge amounts of the four pixels in the same row is replaced with the charge amount of the defective pixel, and it is possible to achieve harmony between improvement in image quality and improvement in processing speed.

According to the average of the above equation (3), a pixel provided with a color filter of the same color as the defective pixel in a 5 × 5 pixel area centered on the defective pixel, and having the same column as the defective pixel Alternatively, the average value of the charge amounts of the two pixels in the same row is replaced with the charge amount of the defective pixel, so that the processing speed can be improved. Note that the correction processing is similarly performed for the filter colors B, C, and D other than A.

On the other hand, as shown in FIG. 8, the color mosaic filter is a filter of three colors A, B, and C (for example, R, G, and B), and pixels relating to filter colors B and C are defective pixels. In such a case, the charge amount can be replaced by using the expressions (1) to (3). on the other hand,
When the pixel related to the filter color A is a defective pixel, the calculation can be performed based on any of the following formulas.

(I) First Calculation Formula _{An, n} = (A _{n−1, n−1} + A _{n−1, n + 1} + A _{n + 1, n−1} + A _{n + 1, n + 1} ) / 4 (4) (ii) Second calculation formula _{An, n} = ( _{An-2, n-2} + _{An-2, n} + _{An-2, n + 2} + _{An-1, n-1)} + _{An-1, n + 1} + _{An, n-2} + _{An, n + 2} + _{An + 1, n-1} + _{An + 1, n + 1} + _{An + 2, n-2} + _{An + 2, n} + A _{n + 2, n + 2} ) / 12 (5)

According to the average of the above equation (4), within the 3 × 3 pixel area centered on the defective pixel, the charge amount of the four pixels at the four corners where the same A color filter as the defective pixel is provided is provided. Since the average value is replaced by the charge amount of the defective pixel, it is possible to achieve harmony between improvement in image quality and improvement in processing speed.

On the other hand, according to the average of the above equation (5), within the 5 × 5 pixel area centered on the defective pixel, the average value of 12 pixels provided with the same A color filter as the defective pixel is calculated as The charge amount of the defective pixel is replaced, and the image quality can be improved.

Further, when a three-plate CCD as shown in FIG. 9 is used, A, B, C (for example, R, G, B) color filters are provided for each CCD, so that defective pixels When correcting the charge amounts of the pixels _{An and n} , the calculation can be performed based on any of the following formulas.

(I) First calculation formula _{An, n} = (A _{n−1, n−1} + A _{n−1, n} + A _{n−1, n + 1} + A _{n, n−1} + A _{n, n + 1} + _{An + 1, n-1} + _{An + 1, n} + _{An + 1, n + 1} ) / 8 (6) (ii) Second calculation formula _{An, n} = ( _{An-1, n- 1} + A _{n−1, n + 1} + A _{n + 1, n−1} + A _{n + 1, n + 1} ) / 4 (7) (iii) Third formula: _{An, n} = (A _{n−1, n} + _{An, n-1} + _{An, n + 1} + _{An + 1, n} ) / 4 (8) (iv) Fourth calculation formula _{An, n} = ( _{An-1, n} + _{An + 1, n} ) / 2 (9) (v) Fifth calculation formula _{An, n} = ( _{An, n-1} + _{An, n + 1} ) / 2 (10) (vi) Sixth calculation formula _{An, n} = (A _{n−1, n−1} + A _{n + 1, n + 1} ) / 2 (11) (vii) Seventh calculation formula _{An, n} = (A _{n−1, n + 1} + A _{n +) 1, n-1} ) / 2 (12)

The calculation based on the equation (6) is to calculate the average value of the electric charges of eight pixels adjacent to the defective pixel.
The calculation based on the expression (7) is 3 × 3 around the defective pixel.
The average value of the charge amounts of the four pixels at the four corners in the pixel area is obtained.

The calculation based on the equation (8) is to calculate the average value of the electric charges of the four pixels above, below, left and right adjacent to the defective pixel. The calculation based on the equation (9) is based on the two pixels above and below the defective pixel. Is to calculate the average value of the charge amounts.

The calculation based on the expression (10) is to calculate the average value of the electric charge amounts of two pixels on the left and right adjacent to the defective pixel. The calculation based on the expression (11) is the upper left and lower right adjacent to the defective pixel. The calculation based on the expression (12) is to calculate the average value of the charge amounts of the two upper right and lower left pixels adjacent to the defective pixel. Such a calculation formula may be appropriately selected from required image quality and processing speed.

As described above, according to the present embodiment,
When the exposure time is short, the correction of the white defect is performed using the data of the white defect stored in the memory 9, so that the correction can be performed quickly. On the other hand, when the exposure time is long, white flaw detection is performed after imaging, so that it is not necessary to store data relating to white flaws in the memory 9, thereby efficiently performing inspection in the production process of the digital still camera. In addition to this, the storage capacity of the memory 9 can be reduced.

FIG. 10 is a diagram showing a second embodiment of the digital still camera. According to the configuration shown in FIG. 10, it is possible to detect a defective pixel and correct the charge amount corresponding to the defective pixel in the same manner as in the first embodiment. In the second embodiment, the same elements as those in the configuration of FIG.

In FIG. 10, the signal processing section 41 to which the digital signal converted by the A / D conversion circuit 4 is output includes a signal processing circuit 42, a pixel defect detection circuit 43 as pixel defect detection means, and a pixel defect detection circuit. A pixel defect correction circuit 44 as defect correction means is provided.

The signal processing circuit 42 is a circuit which performs a luminance process and a color process and converts it into, for example, a luminance signal and a digital video signal as a color difference signal. The pixel defect detection circuit 43 is a circuit that detects a defective pixel having a white defect in the same manner as in the first embodiment, and the position information (two-dimensional coordinates) of the defective pixel detected by the pixel defect detection circuit 43 is It is stored in the memory 9.

The pixel defect correction circuit 44 corrects the amount of charge applied to the defective pixel based on the position information (two-dimensional coordinates) of the defective pixel stored in the memory 9 and the image data based on the corrected amount of charge To the signal processing circuit 42.

Although the present invention has been described with reference to the embodiments, it should be understood that the present invention should not be construed as being limited to the above-described embodiments, and that modifications and improvements can be made as appropriate. is there. For example, in this embodiment,
The processing mode is changed depending on whether or not the exposure time is 1/8 second or less. However, since the time varies with the type of the imaging device, it may be changed according to the actual pixel defect. In the case of an ordinary digital still camera, it should fall within the range of about 1/8 second to 1/2 second.

[0061]

According to the electronic camera of the present invention, a solid-state imaging device having a plurality of pixels, storage means for storing information on defective pixels of the solid-state imaging device, and information on a pixel of interest stored in predetermined information and Since it has a detecting means for detecting whether or not the pixel of interest is a defective pixel by comparison, a pixel defect is corrected based on the information on the defective pixel stored in advance, for example, during short-time exposure. By doing so, such correction processing can be performed quickly. On the other hand, at the time of long-time exposure, if a defective pixel is detected by the detection means, the information on the defective pixel to be stored is reduced, and the storage capacity of the storage means is small. Can be suppressed, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

According to the electronic camera of the present invention, the solid-state imaging device having a plurality of pixels, the storage means for storing information on defective pixels of the solid-state imaging device, and the information on the target pixel are compared with predetermined information. Thus, based on the information on the exposure time at the time of photographing, whether the target pixel is a defective pixel or not, based on the information on the defective pixel, Or a determining means for determining whether to detect a defective pixel by the detecting means. For example, at the time of short-time exposure, it is possible to correct a pixel defect based on information about a defective pixel stored in advance. Correction processing can be performed quickly. On the other hand, at the time of long exposure, if the determining means determines that the defective pixel is detected by the detecting means, the information on the defective pixel to be stored is reduced, and therefore the storage capacity of the storage means is small. In addition, the cost of the electronic camera can be kept low, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

According to the signal correction method of the present invention, it is determined whether the exposure time of the electronic camera is one of the first exposure time and the second exposure time, and the exposure time is determined by the first exposure time. When the exposure time is, the defective pixel is specified based on the previously stored information on the defective pixel of the solid-state imaging device. On the other hand, when the exposure time is the second exposure time, the information on the pixel of interest is Since the method includes a step of detecting a defective pixel by comparing with predetermined information and a step of correcting an output signal from the detected defective pixel, for example, the first exposure time is determined to be short and stored in advance. If the output signal from the defective pixel is corrected based on the information on the defective pixel, the correction process can be performed quickly. On the other hand, if the second exposure time is determined to be a long exposure time and the information on the pixel of interest is compared with predetermined information to detect defective pixels, the information on defective pixels to be stored is reduced. Since the storage capacity of the means is small, the cost of the electronic camera can be kept low, and the time for collecting data on defective pixels in the production process of the electronic camera can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital still camera as an electronic camera according to a first embodiment.

FIG. 2 is a diagram illustrating an example of a four-color filter.

FIG. 3 is a diagram showing a state in which the filters of FIG. 2 are two-dimensionally arranged.

FIG. 4 is a diagram showing a state in which a monochromatic filter is arranged.

FIG. 5 is a flowchart illustrating a process when an image of a subject is actually captured using the electronic camera according to the embodiment;

FIG. 6 is a subroutine for performing signal processing and flaw correction processing.

FIG. 7 is a diagram schematically showing a color mosaic filter attached to a CCD.

FIG. 8 is a diagram schematically illustrating a color mosaic filter different from FIG. 7;

FIG. 9 is a diagram schematically showing a color mosaic filter attached to a three-plate CCD.

FIG. 10 is a diagram showing a second embodiment of the digital still camera.

[Explanation of symbols]

 Reference Signs List 1 CCD 2 drive circuit 3 CDS circuit 4 A / D conversion circuit 5 image memory 6 CPU 7 storage unit 8 control circuit 9 memory 10 liquid crystal display device 11 lens 12 aperture 13 temperature sensor 14 lens drive circuit 15 power switch 16 mode switch 17 Timer 21 Diffusion plate 41 Signal processing unit 42 Signal processing circuit 43 Pixel defect detection circuit 44 Pixel defect correction circuit

Claims (11)

[Claims] 1. A solid-state imaging device having a plurality of pixels, a storage unit for storing information on defective pixels of the solid-state imaging device, and comparing information on a pixel of interest with predetermined information, so that the pixel of interest is An electronic camera comprising: a detection unit configured to detect whether the pixel is a defective pixel. 2. A solid-state imaging device having a plurality of pixels; storage means for storing information on defective pixels of the solid-state imaging device; and comparing the information on the pixel of interest with predetermined information, so that the pixel of interest is Detecting means for detecting whether or not the pixel is a defective pixel, and identifying a defective pixel from information on the defective pixel stored in the storage means based on information on an exposure time at the time of photographing, or A determination unit for determining whether to detect a defective pixel. 3. An output signal from a defective pixel specified from information on the defective pixel stored in the storage means,
3. The electronic camera according to claim 1, further comprising a correction unit configured to correct an output signal from the defective pixel detected by the detection unit. 4. The electronic camera according to claim 1, wherein the storage unit stores information on defective pixels corresponding to a plurality of exposure times. 5. The electronic camera according to claim 1, wherein the predetermined information is obtained from data of peripheral pixels located around the pixel of interest. 6. The method according to claim 1, wherein the determining unit determines that the defective pixel is detected by the detecting unit when determining that the image capturing is a long-time exposure based on information on an exposure time at the time of image capturing. The electronic camera according to any one of claims 1 to 5, wherein 7. The long-time exposure means that the exposure time is 1/8
7. The electronic camera according to claim 6, wherein the time is longer than seconds. 8. A signal correction method for an electronic camera having a solid-state imaging device, the method comprising: determining whether an exposure time of the electronic camera is one of a first exposure time and a second exposure time. When the exposure time is the first exposure time, a defective pixel is specified based on information on a defective pixel of the solid-state imaging device stored in advance, while the exposure time is the second exposure time. A signal correction method comprising the steps of: detecting a defective pixel by comparing information on a target pixel with predetermined information; and correcting the output signal from the detected defective pixel. . 9. The signal correction method according to claim 8, wherein the predetermined information is obtained from data of peripheral pixels located around the target pixel. 10. The signal correction method according to claim 8, wherein the first exposure time is equal to or shorter than a predetermined time, and the second exposure time is longer than the predetermined time. 11. The predetermined time is from 1/8 second to 1/2.
The signal correction method according to claim 10, wherein the time is any time up to seconds.