JP2004304282A - Digital camera and pixel information forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera which efficiently corrects defective pixels of an imaging device, using a few information, compared with the number of photodetectors. <P>SOLUTION: The digital camera 100 comprises an imaging device 120 having an imaging region composed of a plurality of pixels and two kinds of photodetectors different in light receiving sensitivity and light receiving saturation level per pixel. An EEPROM 230 has stored a correction table taking the pixel with at least one photodetector being defective as a defective pixel. A digital signal processor 150 corrects the output signal of the defective pixel in processing imaging signals, based on the correction table. Since the output signal of the defective pixel is corrected, based on one correction table, this effectively corrects them using a few information, compared with the number of photodetectors of the imaging device 120, and reduces the capacity of the EEPROM 230. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera including an imaging device having two types of light receiving elements with different light receiving sensitivities and received light signal saturation levels for each pixel, and a pixel information creation method for an imaging device mounted on the digital camera.
[0002]
[Prior art]
An imaging device using a CCD (Charge Coupled Device) or the like forms a light receiving region by integrating a large number of minute light receiving elements such as hundreds of thousands to millions, so that a defective light receiving element, that is, a defective pixel is formed. It is difficult to produce something that does not exist at all. Therefore, the presence or absence (defect data) of each pixel of the imaging device is acquired in advance, a data table indicating whether or not each pixel is defective is created, and the data table is digitally mounted with the corresponding imaging device. Recorded in the camera's non-volatile memory, and when processing the imaging signal, the digital camera refers to the data table recorded in the non-volatile memory and replaces the signal of the defective pixel with the signal of the adjacent normal pixel Such correction processing is performed. (See Patent Document 1)
[0003]
[Patent Document 1]
Japanese Patent Publication No. 1-29455 [0004]
[Problems to be solved by the invention]
However, the wide dynamic range imaging device having two types of light receiving elements with different light receiving sensitivity and light receiving signal saturation level for each pixel inevitably increases the number of light receiving elements. In this case, it is created for the accumulated charge (standard signal) of the light receiving element responsible for low brightness, the accumulated charge of the light receiving element responsible for high brightness (high brightness signal), and the mixed output of the standard signal and high brightness signal, respectively. If the data table is recorded in the non-volatile memory, a non-volatile memory having a large recording capacity is required, and the correction process is complicated.
[0005]
The present invention was devised in view of such problems of the prior art, and an object thereof is an image pickup device having two types of light receiving elements having different light receiving sensitivities and light receiving signal saturation levels for each pixel. Is to provide a digital camera having a function of efficiently correcting information using information that is small relative to the number of light receiving elements, and a method for creating image information used in the digital camera.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a digital camera of the present invention has an imaging region composed of a plurality of pixels, and an imaging device having two types of light receiving elements each having different light receiving sensitivity and light receiving signal saturation level for each pixel. A memory storing pixel information in which at least one light receiving element has a defective pixel, and a correction processing circuit for correcting an output signal of the defective pixel based on the pixel information It is equipped with.
[0007]
This digital camera corrects the output signal of the defective pixel based on pixel information in which at least one light receiving element has a defect as a defective pixel. Therefore, the digital camera efficiently corrects using information that is less than the number of light receiving elements. be able to.
[0008]
In addition, the pixel information creation method of the present invention is an image pickup device that has an imaging region composed of a plurality of pixels and has first and second light receiving elements having different light receiving sensitivities and light receiving signal saturation levels for each pixel. A method of creating pixel information, the step of reading out an output signal of the first light receiving element for each pixel and creating information indicating whether each pixel is defective, and an output of the second light receiving element A signal is read out for each pixel, information indicating whether or not each pixel is defective, and a logical sum of the information generated in the above steps are calculated, and a pixel whose result is 1 is defective. Creating pixel information as pixels.
[0009]
According to this method, it is possible to accurately create pixel information in which a pixel having a defect in at least one light receiving element is a defective pixel.
[0010]
In another pixel information creation method of the present invention, the imaging device has an imaging region composed of a plurality of pixels, and each pixel has first and second light receiving elements having different light receiving sensitivities and light receiving signal saturation levels. The pixel information creating method of the above, wherein the output signal of the first light receiving element and the output signal of the second light receiving element are simultaneously read out for each pixel, and information indicating whether each pixel is defective or not A step of creating, reading out an output signal of the first light receiving element for each pixel, creating information indicating whether each pixel is defective, and an output signal of the second light receiving element as a pixel A step of creating information indicating whether or not each pixel is defective and a logical sum of a plurality of pieces of information created in the above steps and calculating a pixel whose result is 1 as a defective pixel Create pixel information as Has a step that, a.
[0011]
According to this method, pixel information in which a pixel having a defect in at least one light receiving element is a defective pixel can be created accurately and in a shorter time.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0013]
Here, the principle and configuration example of the imaging device mounted on the digital camera of the present invention will be described.
[0014]
The imaging device has a limit in the amount of light that can be photoelectrically converted, and when the amount of received light reaches a certain level, the output signal (light reception signal) is saturated as shown in FIG. This is a phenomenon common to imaging devices in general.
[0015]
Therefore, two types of light receiving elements having different light receiving sensitivities (hereinafter, a relatively high sensitivity light receiving element is referred to as a main pixel and a low sensitivity light receiving element is referred to as a sub pixel) are mixed in the same imaging device. The saturation level of the pixel is set to be equal to or greater than the sensitivity reduction rate. For example, the sensitivity of the sub-pixel is set to 1/16 and the saturation level is set to 1/4 with respect to the main pixel. Then, as shown in FIG. 2, photoelectric conversion can be performed up to four times the amount of light of the main pixel, that is, imaging can be performed. The dynamic range has been expanded by 400%.
[0016]
FIG. 3 shows a configuration example of an imaging device mounted on the digital camera of the present invention. In the imaging region PS, a plurality of pixels PIX are arranged at every other column in each row and at every other row in each column to form a so-called honeycomb structure. The vertical charge transfer path 6 is arranged to meander in the vicinity of each column.
[0017]
A vertical charge transfer drive circuit 2 that drives the vertical transfer electrode EL is disposed on the right side of the imaging region PS. A horizontal charge transfer path 3 that receives charges from the vertical charge transfer path 6 and transfers them in the horizontal direction (left direction) is disposed below the imaging region PS. An output amplifier 4 is connected to the left end of the horizontal charge transfer path 3.
[0018]
FIG. 4A is a partial plan view of the imaging region, and shows two adjacent pixels PIX in the imaging region PS. Each pixel PIX has a main pixel 21 and a sub-pixel 22 each made of a photodiode. The main pixel 21 has a relatively large area, and the sub-pixel 22 has a relatively small area. Vertical charge transfer paths 6 are disposed on the left and right sides of the pixel PIX.
[0019]
As indicated by dotted lines, polysilicon electrodes 14, 15, 18,..., 19 (EL) for four-phase driving are disposed above the vertical charge transfer path 6. For example, when the transfer electrode is formed of two-layer polysilicon, the transfer electrodes 14 and 18 are formed of, for example, a first layer of polysilicon, and the transfer electrodes 15 and 19 are formed of a second layer of polysilicon. The transfer electrode 14 also controls charge reading from the sub-pixel 22 to the vertical charge transfer path 6. The transfer electrode 15 also controls charge reading from the main pixel 21 to the vertical charge transfer path 6.
[0020]
4 (b) and 4 (c) are cross-sectional views taken along line IB and IC in FIG. 4 (a), respectively. As shown in FIG. 4B, a p-type well 17 is formed on the surface of the n-type semiconductor substrate 16. Two n-type regions are formed in the surface region of the p-type well 17, and these constitute a main pixel 21 and a sub-pixel 22. The p + type region 27 is a channel stop region for performing electrical separation of the pixel PIX, the vertical charge transfer path 6 and the like.
[0021]
As shown in FIG. 4C, the n-type region constituting the vertical charge transfer path 6 is disposed in the vicinity of the n-type region constituting the main pixel 21. A p-type well 17 between them forms a read transistor.
[0022]
An insulating layer such as a silicon oxide film is formed on the surface of the n-type semiconductor substrate 16, and a transfer electrode EL formed of polysilicon is formed thereon. The transfer electrode EL is disposed so as to cover the vertical charge transfer path 6. An insulating layer such as silicon oxide is further formed on the transfer electrode EL, and a light shielding film 12 having an opening on the upper side is formed of tungsten or the like so as to cover the vertical charge transfer path 6 and the like. An interlayer insulating film 13 made of phosphosilicate glass or the like is formed so as to cover the light shielding film 12, and the surface thereof is flattened.
[0023]
A color filter layer 10 is formed on the interlayer insulating film 13. The color filter layer 10 includes three or more color regions such as a red region 25 and a green region 26, for example. On the color filter layer 10, microlenses 11 are formed of a resist material or the like corresponding to each pixel PIX.
[0024]
As shown in FIG. 4B, one microlens 11 is formed on each pixel PIX, and two types of color filters 25 and 26 are disposed below the microlens 11. The light transmitted through the color filter 25 enters the main pixel 21. The light transmitted through the color filter 26 is mainly incident on the sub-pixel 22. The microlens 11 collects light incident from above on the opening of the light shielding film 12.
[0025]
Next, the pixel information creation method of the present invention will be described.
[0026]
FIG. 5 is a flowchart showing a procedure for creating pixel information for correcting a defective pixel of the imaging device.
First, a light shielding condition, that is, a condition in which light does not enter the imaging region of the imaging device is set (S1). In this state, the output signal of the main pixel (hereinafter referred to as a standard signal) is read for each pixel (S2), and is compared with a previously measured scratch level to indicate whether each pixel is defective. A table (1) is created (S3). Subsequently, an output signal of the sub-pixel (hereinafter referred to as a high luminance signal) is read for each pixel (S4), and is compared with a scratch level measured in advance, thereby indicating whether or not each pixel is defective. Table (2) is created (S5).
[0027]
Next, whether or not each pixel is defective by irradiating the imaging region of the imaging device with the standard white level light (S6), reading the standard signal for each pixel (S7), and comparing it with the scratch level measured in advance. A scratch data table {circle over (3)} indicating whether or not is created (S8).
[0028]
Next, while irradiating the imaging region of the imaging device with high-intensity white level light (S9), the high-intensity signal is read out for each pixel (S10) and compared with the scratch level measured in advance. A scratch data table {circle over (4)} indicating whether or not there is present is created (S11).
[0029]
Thereafter, the logical sum of the data tables {circle over (1)} to {circle around (4)} is calculated, and a correction table (pixel information) is created in which the pixel whose result is 1 is a defective pixel (S12).
[0030]
FIG. 6 is a flowchart showing another procedure for creating pixel information.
First, the light shielding condition is set (S21). In this state, the standard signal and the high-intensity signal are mixed and read for each pixel (S22), and compared with a scratch level measured in advance, a scratch data table (1) indicating whether each pixel is defective or not. Is created (S23).
[0031]
Next, whether or not each pixel is defective by irradiating the imaging region of the imaging device with the standard white level light (S24), reading the standard signal for each pixel (S25), and comparing it with the scratch level measured in advance. A scratch data table {circle over (2)} indicating whether or not is created (S26).
[0032]
Next, while irradiating the imaging region of the imaging device with high brightness white level light (S27), the high brightness signal is read out for each pixel (S28), and compared with the scratch level measured in advance. A scratch data table {circle over (3)} indicating whether or not there is present is created (S29).
[0033]
Thereafter, the logical sum of the data tables {circle over (1)} to {circle around (3)} is calculated, and a correction table (pixel information) is created in which the pixel whose result is 1 is a defective pixel (S30).
[0034]
According to the procedure of FIG. 6, since the standard signal and the high luminance signal are simultaneously read out for the signal at the time of shading caused by crystal defects, the defect data is acquired and corrected in a shorter time than the case of FIG. A table can be created.
[0035]
FIG. 7 is a flowchart showing still another procedure for creating pixel information.
First, the light shielding condition is set (S31). In this state, the standard signal and the high-intensity signal are mixed and read for each pixel (S32), and compared with a scratch level measured in advance, thereby a scratch data table (1) indicating whether each pixel is defective or not. Is created (S33).
[0036]
Next, whether or not each pixel is defective by irradiating the imaging region of the imaging device with the standard white level light (S34), reading the standard signal for each pixel (S35), and comparing it with the scratch level measured in advance. A scratch data table {circle over (2)} indicating whether or not is created (S36). Subsequently, a high-intensity signal is read out for each pixel (S37), and compared with a scratch level measured in advance, a scratch data table (3) indicating whether or not each pixel is defective is created (S38).
[0037]
Thereafter, the logical sum of the data tables {circle over (1)} to {circle around (3)} is calculated, and a correction table (pixel information) is created in which the pixel whose result is 1 is a defective pixel (S39).
[0038]
FIG. 8 is a flowchart showing still another procedure of pixel information.
First, the light shielding condition is set (S41). In this state, the standard signal and the high-intensity signal are mixed and read for each pixel (S42), and a scratch table (1) indicating whether or not each pixel is defective by comparing with a previously measured scratch level is obtained. Create (S43).
[0039]
Next, while irradiating the imaging region of the imaging device with the standard white level light (S44), the standard signal and the high luminance signal are mixed and read for each pixel (S45), and compared with the scratch level measured in advance. A scratch data table {circle around (2)} indicating whether each pixel is defective is created (S46).
[0040]
Thereafter, the logical sum of the flaw data tables {circle around (1)} and {circle around (2)} is calculated, and a correction table (pixel information) is created in which the pixel whose result is 1 is a defective pixel (S47).
[0041]
According to the procedures of FIGS. 7 and 8, defect data can be acquired and a correction table can be created in a shorter time than in the case of FIG.
[0042]
FIG. 9 is a block diagram showing a configuration example of a digital camera according to the present invention. The digital camera 100 includes an optical system 110, an imaging device 120, an analog signal processing unit 130, an A / D conversion unit 140, a digital signal processing unit 150, a buffer memory 160, a compression / decompression processing unit 170, a YC → RGB conversion unit 180, A media driver 190, an LCD driver 200, a monitor LCD (Liquid Crystal Display) 210, an operation unit 220, an EEPROM (Electrically Erasable Programmable Random Access Memory) 230, a CPU (Central Processing Unit) 240, and the like.
[0043]
The optical system 110 includes a lens 111, a diaphragm 112, a shutter 113, and the like, and forms a subject image on the imaging region PS of the imaging device 120. The shutter 113 is provided in order to prevent light from entering the imaging region PS and generating smear when signals are read from the imaging device 120, but is not necessarily required depending on the configuration of the imaging device 120. .
[0044]
The imaging device 120 is the wide dynamic range imaging device illustrated in FIG. 3, and outputs an image signal corresponding to the amount of light incident on the imaging region PS to the analog signal processing unit 130.
[0045]
The analog signal processing unit 130 performs predetermined analog signal processing such as noise reduction processing, white balance processing, and γ processing on the input image signal, and outputs the processed signal to the A / D conversion unit 140. The A / D converter 140 converts the input analog signal into a digital image signal and outputs the digital image signal to the digital signal processor 150.
[0046]
The digital signal processing unit 150 performs predetermined digital processing such as filter processing and defective pixel correction processing on the output signal from the A / D conversion unit 140.
[0047]
An output signal from the digital signal processing unit 150 is sent to the YC → RGB conversion unit 180, the compression / decompression processing unit 170, the LCD driver 200, and the like via the buffer memory 160. The compression / decompression processing unit 170 compresses the image data stored in the buffer memory 160 by a predetermined compression method such as the JPEG method, and records the data on the portable recording medium 191 or reads it from the portable recording medium 191. Decompress image data. The YC → RGB conversion unit 180 converts the uncompressed image data sent to the compression / decompression processing unit 170 into luminance data Y and color difference data Cr and Cb. The YC → RGB conversion unit 180 converts the YC separation signal into a luminance signal and the color difference signal into an RGB signal when displaying the image data (captured image) recorded on the portable recording medium 191 on the monitor LCD 210. When the LCD driver 200 drives the monitor LCD 210 based on the RGB signals, a color image is displayed on the monitor LCD 210.
[0048]
As the portable recording medium 191, a small memory card or the like equipped with a flash memory is used. Writing / reading of image data to / from the portable recording medium 191 is performed via the media driver 190.
[0049]
The operation unit 220 is provided with various operators including a release button. The release button is an operator for instructing the digital camera 100 to start shooting. When the release button is pressed halfway, focus control and aperture control of the optical system 110 are performed, and shooting is performed when the release button is completely pressed. The imaging signal is captured by the device 120, the analog signal processing unit 130, and the A / D conversion unit 140. At that time, the optical system 110 is controlled by a photometry / ranging CPU (not shown), and the imaging device 120, the analog signal processing unit 130, and the A / D conversion unit 140 are controlled by an imaging system control circuit (not shown).
[0050]
The EEPROM 230 stores programs and data for realizing various functions of the digital camera 100. The data stored in the EEPROM 230 includes a correction table for the imaging device 120 created by any one of the procedures shown in FIGS. The CPU 240 performs overall control of the digital camera 100 by executing a program stored in the EEPROM 230.
[0051]
In this digital camera 100, when processing an imaging signal, the digital signal processing unit 150 refers to a correction table stored in the EEPROM 230 and replaces a signal of a defective pixel of the imaging device 120 with a signal of an adjacent normal pixel. The defective pixel correction process is performed. As a result, the imaging device 120 having a scratch can be used.
[0052]
At this time, since the output signal of the defective pixel can be corrected based on one correction table, correction can be performed efficiently using information that is small relative to the number of light receiving elements of the imaging device 120. In addition, the capacity of the EEPROM 230 for recording the correction table can be reduced.
[0053]
In the above-described embodiment, a honeycomb structure imaging device using a CCD is described as an example of a wide dynamic range imaging device. However, a CMOS (Complementary Metal Oxide Semiconductor) type imaging device or a matrix structure imaging device is used. In this case, the present invention is also effective.
[0054]
Note that the order of reading standard signals, high luminance signals, etc. in FIGS. 5 to 8 can be changed as appropriate. In addition, the setting order of conditions such as light shielding, standard white level light irradiation, and high brightness white level light irradiation can be changed as appropriate.
[0055]
Further, in the above example, the defective pixel correction process is performed by the digital signal processing unit 150, but it goes without saying that the CPU 240 may perform this process.
[0056]
Further, it is not always necessary to have pixel information as a table. That is, the data structure of the pixel information may be an array structure, a list structure, or another data structure.
[0057]
【The invention's effect】
As described above, the digital camera of the present invention corrects the output signal of a defective pixel based on pixel information in which at least one light receiving element has a defective pixel as a defective pixel, so the number of light receiving elements is small. The information can be used for efficient correction.
[0058]
Further, according to the correction table creation method of the present invention, it is possible to accurately create a correction table in which a pixel having a defect in at least one light receiving element is a defective pixel.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a relationship (sensitivity curve) between an incident light amount and an output signal amount in a general imaging device.
FIG. 2 is a diagram illustrating the principle of an imaging device having a main pixel and a sub-pixel for each pixel.
FIG. 3 is a conceptual diagram illustrating a configuration example of an imaging device to which the defect correction method of the present invention is applied.
FIG. 4A is a partial plan view of an imaging region. (B) is sectional drawing along the IB line in (a). (C) is sectional drawing along the IC line in (a).
FIG. 5 is a flowchart showing a procedure for creating pixel information according to the method of the present invention;
FIG. 6 is a flowchart showing another procedure for creating pixel information according to the method of the present invention;
FIG. 7 is a flowchart showing still another creation procedure of pixel information according to the method of the present invention.
FIG. 8 is a flowchart showing still another procedure for creating pixel information according to the method of the present invention;
FIG. 9 is a block diagram illustrating a configuration example of a digital camera according to the present invention.
[Explanation of symbols]
PIX: Pixel PS: Imaging region 2: Vertical charge transfer drive circuit 3: Horizontal charge transfer path 4: Output amplifier 6: Vertical charge transfer path 21: Main pixel (light receiving element)
22: Sub-pixel (light receiving element)
100: Digital camera 110: Optical system 120: Imaging device 150: Digital signal processing unit (correction processing circuit)
230: EEPROM (memory)

Claims (3)

A digital camera having an imaging device having an imaging region composed of a plurality of pixels and having two types of light receiving elements with different light receiving sensitivity and light receiving signal saturation level for each pixel,
A memory storing pixel information in which at least one light receiving element has a defective pixel as a defective pixel;
A correction processing circuit for correcting an output signal of the defective pixel based on the pixel information;
A digital camera characterized by having A pixel information creation method for an imaging device having an imaging region composed of a plurality of pixels and having first and second light receiving elements with different light receiving sensitivities and light receiving signal saturation levels for each pixel,
Reading out an output signal of the first light receiving element for each pixel, and creating information indicating whether each pixel is defective;
Reading an output signal of the second light receiving element for each pixel, and creating information indicating whether each pixel is defective;
Calculating a logical sum of a plurality of pieces of information created in the above steps, and creating pixel information in which a pixel whose result is 1 is a defective pixel;
A pixel information creation method characterized by comprising: A method for creating pixel information of an imaging device having an imaging region composed of a plurality of pixels, and each pixel having first and second light receiving elements having different light receiving sensitivities and light receiving signal saturation levels,
Simultaneously reading out the output signal of the first light receiving element and the output signal of the second light receiving element for each pixel to create information indicating whether each pixel is defective;
Reading out an output signal of the first light receiving element for each pixel, and creating information indicating whether each pixel is defective;
Reading an output signal of the second light receiving element for each pixel, and creating information indicating whether each pixel is defective;
Calculating a logical sum of a plurality of pieces of information created in the above steps, and creating pixel information in which a pixel whose result is 1 is a defective pixel;
A pixel information creation method characterized by comprising:

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