JP2001008107A - Image processor, image processing system, its method, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor capable of improving the quality of a photographed image by surely correcting defective pixels. SOLUTION: An initial defect correction means 202 correct digital image information by using initial defective pixel position information previously known at the time of shipment from a plant or the like. A defective position extraction means 204 extracts defective pixel position information from image information obtained after correcting defective pixels by the means 202. The defective pixel position information obtained by the extraction is the positional information of defective pixels increased during the period of using a plane sensor by a user and the increased defective pixel position information also can be used for correcting an image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for correcting a defective pixel when a digital image is collected by a flat sensor composed of a plurality of pixels. The present invention relates to an image processing apparatus, an image processing system, an image processing method, and a storage medium in which a computer stores processing steps for executing the image processing method.

[0002]

2. Description of the Related Art Conventionally, for example, X-ray photography for medical diagnosis is often performed by a film screen system using a combination of an intensifying screen and an X-ray photographic film. In the above system, the X-rays (including the internal information of the subject) that have passed through the subject are converted into visible light proportional to the intensity of the X-rays by an intensifying screen, and the visible light is used to expose the X-ray photographic film. Thus, an X-ray image is formed on an X-ray photographic film.

In recent years, X-rays have been converted into visible light in proportion to the intensity of the X-rays by a phosphor, and the visible light has been converted into an electric signal using a flat sensor composed of a plurality of pixels. By digitizing the analog electric signal with an analog / digital (A / D) converter,
X-ray digital imaging devices for obtaining X-ray digital images are beginning to be used. In such an X-ray digital imaging apparatus, since some of the pixels constituting the flat sensor include defective pixels, the defective pixels are generally corrected.

[0004]

By the way, as for the defective pixels on the flat sensor as described above, it is desirable that those recognized as defective pixels at the time of shipment from the factory do not increase at all thereafter. However, there are defective pixels on the shipping user side that increase while the user is using the flat sensor. For this reason, in the above-mentioned conventional X-ray digital photographing apparatus and the like, the defective pixels recognized at the time of factory shipment are to be corrected, but the defective pixels that have increased during use are not to be corrected. Image quality had deteriorated.

Accordingly, the present invention has been made to eliminate the above-mentioned drawbacks, and an image processing apparatus, an image processing system, and an image processing method that improve the quality of an output image by reliably correcting defective pixels. It is an object of the present invention to provide an image processing method and a storage medium in which processing steps for executing the image processing method are readable by a computer.

[0006]

For such a purpose,
According to a first aspect, defective pixel position information is obtained from correction image information obtained prior to collection of image information, and a defective pixel correction process is performed on the image information using the defective pixel position information. An initial defect correcting unit that performs a defective pixel correction process using previously obtained initial defective pixel position information with respect to the correction image information; and A defect position extracting means for extracting defective pixel position information from the image information subjected to the defective pixel correction processing; and a defective pixel correcting process for the image information using the defective pixel position information obtained by the defect position extracting means. And a defect correction unit for performing the correction.

[0007] A second invention is the first invention, wherein
The defect position extracting means includes a defect position synthesizing means for executing the defective pixel position information extracting process for a designated number of times of execution and sequentially synthesizing the defective pixel position information obtained for each execution.

[0008] In a third aspect based on the first aspect,
The defect position extracting means executes the defective pixel position information extracting process for a designated number of times of execution, and sequentially combines the defective pixel position information obtained for each execution, and a defect position synthesizing means. And an initial defect position synthesizing unit for synthesizing the defective pixel position information for the designated number of times of execution and the initial defective pixel position information.

In a fourth aspect based on the second or third aspect, the defect position synthesizing means stores defect position information for holding the synthesis result up to this time for the synthesizing process at the time of executing the next process. It is characterized by including means.

In a fifth aspect based on the second or third aspect, there is provided pixel information storage means capable of storing defective pixel determination count information for each pixel in association with the defective pixel position information, The synthesizing means is characterized in that when synthesizing the defective pixel position information, the processing of adding the number of times of determination is performed.

In a sixth aspect based on the second or third aspect, the defect position extracting means performs the synthesizing processing by the defect position synthesizing means or the initial defect position synthesizing means after executing the processing for the designated number of times of execution. With respect to the result of (1), the position information of the pixel determined and extracted as a defective pixel exceeding the number of determinations specified within the specified number of executions is determined as the defective pixel position information.

According to a seventh aspect of the present invention, in the first aspect,
The image processing apparatus further includes a pixel gain correction unit that performs the pixel gain correction process at the time of shooting for collecting the image information prior to the process by the defect correction unit.

According to an eighth aspect based on the first aspect,
The image information is information obtained by digitizing image information obtained by radiation imaging.

A ninth aspect of the present invention is an image processing system in which a plurality of devices are connected so as to be able to communicate with each other, wherein at least one of the plurality of devices is any one of claims 1 to 8. Characterized by having the function of the image processing apparatus of (1).

[0015] A tenth invention is an image processing method for collecting defect position information prior to collecting image information, and performing defective pixel correction of the image information using the defect position information. An initial defect correction step of executing a defective pixel correction process using the previously collected initial defective pixel position information with respect to the correction image information obtained by capturing to collect the defect position information, A defect position extracting step of collecting defective pixel position information from the image information subjected to the defective pixel correction processing in the initial defect correcting step.

In an eleventh aspect based on the tenth aspect, an execution step of executing the process of collecting the defective pixel position information a specified number of times is provided, and the defective pixel position information is executed for each execution of the execution step. A defect position synthesizing step for synthesizing the information, and the defective pixel position information obtained by the defect position synthesizing step at the time of this execution are used as defect position information for the synthesizing process at the defect position synthesizing step at the next execution. Storing the defect position information stored in the storage means.

In a twelfth aspect based on the tenth aspect, an execution step of executing the process of collecting the defective pixel position information for a designated number of times, and, for each execution of the execution steps, A defect position synthesizing step for synthesizing the information, and the defective pixel position information obtained by the defect position synthesizing step at the time of this execution are used as defect position information for the synthesizing process at the defect position synthesizing step at the next execution. Storing the defect position information stored in the storage means, the defective pixel position information stored in the defect position information storage means, and the initial defect position information after completion of the synthesizing process by the defect position synthesizing step for the designated number of times. And synthesizing the initial defect position.

According to a thirteenth aspect, in the eleventh or twelfth aspect, after the completion of the combining process in the defect position combining step for the designated number of times, the combining process in the defect position combining step or the initial defect position combining step is performed. The method includes a step of determining, as the defective pixel position information, position information of a pixel determined as a defective pixel exceeding the number of determinations specified within the specified number of times.

In a fourteenth aspect based on the tenth aspect, the pixel gain correction processing at the time of shooting for collecting the image information is performed prior to the defective pixel correction processing using the defective pixel position information. The method includes a gain correction step.

In a fifteenth aspect based on the tenth aspect, the image information is digitized image information obtained by radiography.

In a sixteenth aspect based on the eleventh aspect or the twelfth aspect, in the combining process in the defect location combining step, it is determined that the defect is provided corresponding to each pixel of the defect location information storage means. And a step of performing a number-of-judgments processing step of performing a count-up process on a storage unit for holding the number of times the data has been stored.

According to a seventeenth aspect of the present invention, a computer executes a processing step for collecting defect position information prior to collecting image information and performing defective pixel correction of the image information using the defect position information. A storage medium readablely stored, wherein the processing steps include the respective steps of the image processing method according to any one of claims 10 to 16.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

The present invention is applied to, for example, an X-ray imaging apparatus 100 as shown in FIG. The X-ray imaging apparatus 100 includes an X-ray tube 101 that generates X-rays, an X-ray aperture 102 of the X-ray tube 101, and an X-ray tube 102 from the X-ray tube 101.
A solid-state image sensor (plane sensor) 107 on which a line is incident;
A grid 104 and a scintillator 106 provided between the ray tube 101 and the solid-state image sensor 107, and an A / A for outputting the output of the solid-state image sensor 107 as a digital image signal
A D converter 108, an image reading unit 109 that performs various processes on the digital image signal from the A / D converter 108 to output a screen display, and the like, and generates X-rays in the X-ray tube 101. And an X-ray generation controller 126 for controlling.

The image reading unit 109 includes the solid-state imaging device 107
And an image reading control unit 1 that executes various processes including an operation control of the X-ray generation control unit 126 and the like and an image correction process described later.
10, a RAM 111 that stores various data and the like and is also used for work, a ROM 112 that stores various processing programs and the like to be executed by the apparatus, and an external network (here, “LAN”). LAN / IF 113 as an interface unit, and DISK / IF 11 as an interface unit with an external portable medium recording device
4, an NVRAM 115 that is a nonvolatile RAM, a nonvolatile storage unit 116 such as a hard disk, a user interface (IF) unit 117, and a C that controls the operation of the entire apparatus by executing a processing program in the ROM 112.
The PU 118 is connected via a bus 119 to exchange data with each other. The image reading unit 10
9 is provided with an exposure button 125, and the output of the exposure button 125 is supplied to the X-ray generation control unit 126 by the image reading control unit 110 switching and controlling the exposure permission switch 124. It has been made like that. The user IF unit 117 includes a display 120 such as a CRT.
And an operation unit 121 such as a keyboard and a mouse.

[A series of operations of the X-ray imaging apparatus 100]

First, the operator selects the subject 103 to be photographed.
Is disposed between the solid-state imaging device 107 and the X-ray tube 101. Next, the operator prepares for shooting by using the operation unit 121.
This is performed using For example, the imaging part of the subject 103 is selected by the operation unit 121. This operation information is taken into the image reading unit 109 via the user interface 117.

When the preparation for photographing by the operator as described above is completed, the image reading control unit 1
Reference numeral 10 denotes applying a voltage to the solid-state image sensor 107 using a solid-state image sensor drive control signal.
However, a preparation is made to be in a state where an image input of the subject 103 can be made at any time (a state where X-rays from the X-ray tube 102 can be imaged).

Next, the operator adjusts the aperture amount using the aperture instruction unit (not shown) of the operation unit 121 so that the target portion of the subject 103 to be imaged enters the imaging area. The adjustment information of the aperture amount is transmitted to the user interface 117.
Is input into the image reading unit 109 via the.

In the image reading section 109, the image reading control section 110 transmits an aperture signal 2 based on the aperture amount adjustment information from the user interface 117 to the X-ray generation control section 1.
26. The X-ray generation control unit 126 converts the stop signal 3 based on the stop signal 2 from the image reading control unit 110 into an X-ray.
The light is supplied to the line stop 102. Thus, the X-ray aperture 102 opens and closes.

Here, the X-ray aperture 102 is rectangular.
The opening and closing amounts in both the vertical and horizontal directions can be adjusted by the aperture signal 3 from the X-ray generation controller 126. Also, the subject 10 specified by the operator
Appropriate irradiation by the X-ray stop 102 to the portion 3 can be adjusted by lamp light.

Next, the operator operates the exposure button 125. The exposure button 125 is a trigger for generating X-rays with the X-ray tube 101, and generates an exposure signal 1 when operated (pressed down) by an operator. The exposure signal 1 generated from the exposure button 125 is temporarily supplied to the image reading control unit 110 in the image reading unit 109. Upon receiving this, the image reading control unit 110 operates the solid-state imaging device 10.
After confirming whether or not the apparatus 7 is in a state where it can be imaged when receiving X-rays from the X-ray tube 101, based on the state of the drive notification signal generated by the solid-state imaging device 107, an exposure permission signal is emitted. Occurs for the permission switch 124. The irradiation permission signal turns on the irradiation permission switch 124 and makes the irradiation signal 1 generated from the irradiation button 125 conductive to the irradiation signal 2 to the X-ray generation control unit 126. Note that a switch called a second switch of the exposure button 125 is used for the exposure signal.

The X-ray generation controller 126 controls the X-ray tube 101 based on the X-ray signal 2 generated as described above.
As soon as the preparation for generating the X-ray is completed, the exposure signal 3 is transmitted to the X-ray tube 101.
Occurs for As a result, X-ray
Lines occur.

On the other hand, after receiving the above-mentioned exposure, the X-ray of the X-ray tube 101 is
And the scintillator 106 sequentially pass through the subject 103
Is formed on the imaging surface of the solid-state imaging device 107 as a transmitted light image of the solid-state imaging device 107, and is output from the solid-state imaging device 107 as an image signal by photoelectric conversion in the solid-state imaging device 107. The A / D converter 108 digitizes the image signal output from the solid-state imaging device 107 and supplies the digitalized image signal to the image reading unit 109 as a digital image signal.

The image reading unit 109 includes an A / D converter 108
Is temporarily expanded on the RAM 111, and various processes including an image correction process, which will be described later, are performed by the image reading control unit 110.
To display on screen or output on film. Such operation control is performed by the CPU 118.

[Image Correction Processing Configuration in X-Ray Image Shooting Apparatus 100]

First, in the X-ray imaging apparatus 100, for example, calibration imaging is performed. The calibration shooting is an operation for collecting information for image calibration (correction) performed prior to the normal shooting, so that an image at the time of the normal shooting (hereinafter referred to as a “photographed raw image”) is obtained. This is an imaging method in which work of collecting pixel gain information for performing pixel gain correction and collecting position information of defective pixels (hereinafter, referred to as “calibration work”) is performed. In calibration photography, photography is performed a plurality of times, so that average information can be collected. At this time, how many times of photographing is repeated in one calibration work can be set in advance,
Further, while the operator repeats the shooting, the desired shooting can be set as the last shooting. Therefore, in order to collect pixel gain information and defective pixel position information used in the image correction process, as a process before photographing (process immediately before actual photographing), the solid-state image sensor ( Hereafter, the imaging is performed such that the output of, for example, the center 256 × 256 pixels on the imaging surface (sensor surface) of the 107 is about 2048 out of 4096 tones. Image information obtained by this photographing (hereinafter, referred to as “dark current image information”) is automatically collected.

Therefore, the image reading control section 110 includes, for example, an image correcting section 200 as shown in FIG.
The image correction unit 200, as shown in FIG. 2, subtracts the dark current image information collected immediately before the shooting from the raw image information obtained by the normal shooting operation.
01, an initial defect correction unit 202 that performs a defect correction process on the image information from the dark current subtraction unit 201 using the initial defect position information collected before factory shipment, and the like. An image checking unit 203 for checking the adequacy of the obtained initial defect correction image, and an initial defect correcting unit 20 based on the check result of the image checking unit 203.
A pixel gain information addition unit 205 that integrates the initial defect correction image for each shooting obtained in Step 2; a pixel gain information temporary storage unit 206 for temporarily storing information being processed by the pixel gain information addition unit 205; And a pixel gain information holding unit 207 for storing the processing result in the pixel gain information adding unit 205. Further, the image correction unit 200 uses the initial defect correction image information obtained by the initial defect correction unit 202 to extract the position information of the defective pixel increased by the user at the defect position extraction unit 204.
A defect position synthesizing unit 208 for synthesizing defect pixel position information for each image obtained by the defect position extracting unit 204; and a defect position information temporary storage for temporarily storing information during processing by the defect position synthesizing unit 208. The storage unit 209, an increased defect position information holding unit 212 for storing the processing result of the defect position combining unit 208, and the initial defective position information combined with the increased defective pixel obtained by the defect position combining unit 208. An initial defect position synthesizing unit 210 and a defect position information holding unit 211 for storing the processing result of the initial defect position synthesizing unit 210 are provided. In addition, as each of the above-described storage units and holding units, for example, a nonvolatile storage unit 116 (see FIG. 1 described above) is used.

In the image correction unit 200 as described above,
First, the dark current subtraction unit 201 performs a dark current correction process by subtracting dark current image information from photographed raw image information. The initial defect correction unit 202 performs a defect pixel correction process on the image information obtained by the dark current subtraction unit 201 using initial defect position information collected before shipment from a factory or the like. An image obtained as a result of this correction processing is called an “initial defect correction image”.

The image checker 203 uses the initial defect correction image information from the initial defect corrector 202 to output about 2048 of the 4096 gradations at the center of the plane sensor 107.
Then, it is determined whether or not the gray scale is reached.
Here, the plane sensor 107 has 2688 × 2688 pixels (pixels), and the image check unit 203 determines the X-ray dose in the calibration imaging based on the average pixel value of the central 256 × 256 pixel portion of the plane sensor 107. Is determined. For example, when the average pixel value of the central portion of the sensor is 1500 or more and less than 2500, it is determined that the X-ray dose in the calibration imaging is appropriate, and otherwise, it is determined to be inappropriate. When the image check unit 203 determines that the X-ray dose in the calibration imaging is inappropriate, the imaging at this time is cancelled, and a message to restart the imaging is given to the display 120 or the like via the user interface unit 117. Can be This allows
The operator recognizes the photographing again and performs the calibration photographing again.

When the image checking unit 203 determines that the X-ray dose in the calibration imaging is appropriate, the pixel gain information addition unit 205 integrates the initial defect correction image information for each imaging from the initial defect correction unit 202. I do.

Specifically, first, when the photographing is performed for the first time during the calibration work, the initial defect correcting unit 202 is used.
The temporary defect correction image received temporarily from the pixel defect information temporary storage unit 2 as pixel gain information as it is.
06.

When the photographing is not the first photographing during the calibration work, that is, the photographing is the second or later photographing, the information stored in the pixel gain information temporary storage unit 206 and the information received from the initial defect correcting unit 202 are received. The initial defect correction image is added to each pixel, and the addition result is stored in the pixel gain information temporary storage unit 206 again.

If it is the last photographing during the calibration work, the pixel gain information temporary storage unit 20
6 and the initial defect correction image received from the initial defect correction unit 202 are added for each pixel, and the result of the addition is divided by the number of times of photographing to obtain the average value of the pixel gain information. Is calculated. Then, the calculation result is stored in the pixel gain information holding unit 207.

When the calibration photographing is performed once, the pixel gain information temporary storage unit 206
The processing is equivalent to the pixel gain information once collected to be passed to the pixel gain information holding unit 207 as it is. Since information in the pixel gain information holding unit 207 is required at the time of normal photographing, a nonvolatile storage medium is used as the pixel gain information holding unit 207.

On the other hand, the initial defect correction image obtained by the initial defect correction unit 202 is also supplied to a defect position extraction unit 204. The initial defect correction image supplied to the defect position extracting unit 204 is in a state where a defect image (initial defect image) checked in advance at the time of factory shipment has been corrected. Therefore, the defect position extraction unit 204 extracts the position information of the defective pixel that has increased at the user destination. The details of the defect extraction algorithm for this will be described later.

The defect position synthesizing unit 208 synthesizes the defective pixel position information for each photographing obtained by the defect position extracting unit 204.

Specifically, first, when the photographing is performed for the first time during the calibration work, the defect position extracting unit 204
Is temporarily stored in the defect position information temporary storage unit 209 as temporary defective pixel information as it is.
Here, the defect position information temporary storage unit 209 has a mechanism capable of storing the number of times each pixel has been determined to be a defective pixel (hereinafter, referred to as a “determination number storage mechanism”). For the pixel, the number of determinations is “1”.
Is added. Therefore, “1” is set to the pixel determined to be a defective pixel in this case.

In the case where the photographing is not the first photographing during the calibration work, that is, the photographing is performed for the second time or later, the information stored in the defect position information temporary storage unit 209 and the defect The pixel position information is combined with the pixel position information, and the combined result is stored in the defect position information temporary storage unit 209 again. At this time, in the defect position information temporary storage unit 209,
For a pixel determined to be a defective pixel, “1” is added to the number of determinations.

In the case of the last photographing during the calibration work, the information stored in the defect position information temporary storage unit 209 and the defective pixel position information from the defect position extraction unit 204 are combined. The combination result is stored in the increased defect position information holding unit 212 as increased defective pixel position information, and is also supplied to the initial defect position combining unit 211. At this time, after adding “1” to the number of determinations for a pixel determined as a defective pixel by the determination number storage mechanism described above, only when the addition result exceeds a preset number of defect determinations , The pixel is treated as a defective pixel. For example, since calibration photography is generally performed about four times, the number of defect determinations in such a case is:
"2" which is a half value of the number of times of photographing is set (decimal points are rounded down). Therefore, in this case, a pixel determined as a defective pixel more than twice, three or four times is determined as a defective pixel. Initial defect position synthesis unit 211
Synthesizes the initial defect position information collected in advance at the time of factory shipment and the like with the increased defective pixel position information from the defect position synthesizing unit 208, and stores the synthesis result in the defect position information holding unit 211.
To memorize.

When the calibration shooting is performed once and the number of times of pixel determination is “0”, the same processing as when the collected defect position information is passed to the defect position information holding unit 211 as it is.

As described above, the pixel gain information held in the pixel gain information holding unit 207 and the defective pixel position information held in the defect position information holding unit 211 are used for pixel gain correction during normal photographing, which will be described later. Used for processing and defective pixel correction processing.

[Defective Pixel Position Extraction Algorithm Executed by Defect Position Extraction Unit 204]

As the defective pixel position extraction algorithm, a plurality of algorithms such as the following methods (1) to (3) can be selected, and an algorithm selected from these algorithms is selected in advance. The setting is made for the X-ray imaging apparatus 100. Further, the defective pixel position extraction algorithm here can be used, for example, when obtaining initial defective pixel position information at the time of factory shipment.

(Method 1) This algorithm is shown by the conceptual diagram of FIG. 3 and the flowchart of FIG.

First, the upper left of the area on the sensor surface is set as the start pixel of the target pixel Pij (step S301). Next, the average A and the standard deviation σ of all the pixels are calculated from the initial defective pixel correction image obtained by the initial defect correction unit 202, and the standard deviation σ is multiplied by a predetermined magnification N (step S1). S302). Next, it is determined whether or not the absolute value of the difference between the target pixel Pij and the average A of all pixels is larger than the above-described integration result (step S303). As a result of this determination, if “absolute value> integration result”, the target pixel Pij is determined as a defective pixel (step S304). Thereafter, the process proceeds to the next step S305. On the other hand, if “absolute value> integration result” is not satisfied, the process directly proceeds to step S305. In step S305, it is determined whether or not the processing from step S303 has been completed for all the pixels in the area on the sensor surface, and if not completed, the target pixel Pij
Is advanced to the next pixel (step S306), the process returns to step S303, and the subsequent processing steps are repeatedly executed. Then, when the processing from step S303 is completed for all the pixels in the area on the sensor surface, this processing ends.

That is, in this algorithm, | Pij-A (all pixels) |> σ (all pixels) × N Pij: target pixel A (all pixels): average of all pixels σ (all pixels): standard deviation of all pixels N : The target pixel Pij having the relationship of the specified magnification is determined as a defective pixel.
Note that when image shading is present during X-ray imaging, the output value is reduced due to the shading even though the pixel is not a defective pixel, and the pixel may be determined as a defective pixel. For this reason, it is preferable to use this algorithm when the calculation time is high and the shading is small.

(Method 2) This algorithm is shown by the conceptual diagram of FIG. 5 and the flowchart of FIG. First,
In the above (method 1), the average A of all pixels on the sensor surface
And the standard deviation σ, the present algorithm determines the defective pixel based on the average and standard deviation of the vicinity of the target pixel Pij, for example, 256 × 256 pixels around the target pixel Pij. Do.

That is, first, the upper left of the area on the sensor surface is set as the start pixel of the target pixel Pij (step S31).
1). Next, from the initial defect correction image obtained by the initial defect correction unit 202, an average A and a standard deviation σij of 256 × 256 pixels in the vicinity of the target pixel Pij are calculated, and a magnification specified in advance for the standard deviation σij N is integrated (step S312). Next, it is determined whether or not the absolute value of the difference between the target pixel Pij and the average Aij of all 256 × 256 pixels near the target pixel Pij is larger than the above integration result (step S313). As a result of this determination, if “absolute value> integration result”, the target pixel Pij is determined as a defective pixel (step S314). Then, the next step S315
Proceed to. On the other hand, if “absolute value> integration result” is not satisfied, the process directly proceeds to step S315. Step S3
At 15, it is determined whether or not the processing from step S312 has been completed for all the pixels in the area on the sensor surface, and if not, the target pixel Pij is advanced to the next pixel. (Step S316), Step S312
And the subsequent processing steps are repeatedly executed. Then, when the processing from step S312 has been performed on all the pixels in the area on the sensor surface, this processing ends.

According to the present algorithm as described above, X
The influence of shading by radiography is reduced,
More accurate defective pixel determination can be performed. Note that, for example, as shown in FIG. 7, when there are a plurality of A / D converters for reading an image from a flat sensor, the A / D converters may have large variations. In this case, when a neighboring rectangular area is taken so as to straddle two AD converters, for example, A
If the output of the D converter is small, it may be erroneously determined as a defective pixel due to the small output. For this reason, it is preferable to use this algorithm when the plane sensor used is a small sensor and there is only one AD converter.

(Method 3) This algorithm is shown by the conceptual diagram of FIG. 7 and the flowchart of FIG. In the present algorithm, the horizontal direction of the area on the sensor surface is divided by a band according to the AD converter 108 for reading the image from the flat sensor 107, and the vertical direction is also divided by the band so as to further reduce the X-ray shading characteristics. In this way, the area on the sensor surface is vertically and horizontally divided into a grid pattern, and the above-described (method 1) algorithm is executed for the rectangular area where the target pixel Pij exists.

That is, first, a rectangular area divided at the upper left of the area on the sensor surface is set as a target rectangular area (step S321). Next, the upper left of the target rectangular area is set as the start pixel of the target pixel Pij (step S322). Next, the average A and the standard deviation σij of the target rectangular area are calculated from the initial defect correction image obtained by the initial defect correction unit 202, and the magnification N specified in advance for the standard deviation σij is calculated.
Are integrated (step S323). Next, the target pixel Pij
It is determined whether or not the absolute value of the difference between the sum and the average A of all pixels is larger than the above-described integration result (step S324). As a result of this determination, if “absolute value> integration result”, the target pixel P
ij is determined as a defective pixel (step S325). Thereafter, the process proceeds to the next step S326. On the other hand, “absolute value>
If the result is not “integration result”, step S326 is performed as it is.
Proceed to. In step S326, it is determined whether or not the processing from step S324 has been performed on all the pixels in the target rectangular area, and if not, the target pixel Pij is advanced to the next pixel. (Step S32
7), the process returns to step S324, and thereafter, the processing steps are repeatedly executed. When the processing from step S324 is completed for all the pixels in the target rectangular area, the target rectangular area is advanced to the next rectangular area (step S328). Then, it is determined whether or not the processing from step S322 has been completed for all the rectangular areas of the sensor area (step S329). If not, the procedure returns to step S322, and the subsequent processing is performed. Repeat the step. This processing ends when the processing from step S322 is completed for all the rectangular areas of the sensor area.

According to the present algorithm as described above, A
Even when there are a plurality of D converters, it is possible to more accurately determine a defective pixel. In particular, even when a large flat sensor is configured by combining a plurality of flat sensors having a small area, the boundary between the combinations of the flat sensors is used as a boundary.
By dividing the sensor area vertically and horizontally, more accurate determination of a defective pixel can be performed. In this algorithm,
Since the influence of shading by X-ray imaging is reduced and there is no need to follow a combination of AD converters and sensors, the present invention can be used in various configurations regardless of the configuration.

[Extraction of defective pixel position while changing X-ray dose]

First, in general, the output behavior of a pixel obtained from a flat sensor includes a pixel that does not output at all, a pixel that always outputs a digitally large signal, and a pixel that outputs an intermediate value. Of the digital gray scales 4096 described above, in shooting aimed at around 2000 gray scales,
There are cases where the output value of a defective pixel is included in the output of the flat sensor.

Therefore, here, as shown in the flowchart of FIG. 9, the X-ray dose (irradiation dose) is variously changed,
The above-described calibration imaging is performed at each X-ray dose, and defective pixel position information is collected.

That is, first, the number of times of photographing with an X-ray dose (allowable number of times of photographing) such that the average of 256 × 256 pixels at the center of the flat sensor 107 is in the range of 500 to 1000 gradations.
Nl (low), the number of times of imaging with an X-ray dose in the range of 1500 to 2500 gradations Nm (mid), 3000 to
Number of times of imaging N at X-ray dose to be in the range of 3500 gradations
h (high) are set respectively (step S40)
1). Here, since Nl = 4, Nm = 4, and Nh = 4, 256 × 25 at the center of the plane sensor 107 is set.
X-ray imaging is performed four times so that the average of six pixels is in the range of 500 to 1000 gray scales, and imaging is performed four times with an X-ray amount so as to be in the range of 1500 to 2500 gray scales.
The imaging with the X-ray dose in the range of 000 to 3500 gradations is performed four times.

Next, the center 256.times.
Extraction of the defective pixel position as described above is performed the number of times indicated by Nl with respect to image information obtained by imaging with X-ray dose such that the average of 256 pixels is in the range of 500 to 1000 gradations ( Step S402). Next, the average of the 256 × 256 pixels at the center of the flat sensor 107 is 1500
Extraction of the defective pixel position as described above is performed by the number of times indicated by Nm with respect to image information obtained by imaging with an X-ray dose in a range of ２2500 gradations. At this time, pixel gain information is also collected for the number of times indicated by Nm (step S403). Next, the plane sensor 107
The average of the 256 × 256 pixels at the center of the
The extraction of the defective pixel position as described above is performed the number of times indicated by Nh with respect to the image information obtained by the imaging with the X-ray dose within the range of 0 gradation (step S40).
4).

For the extraction of the defective pixel position in steps S402 to S404 described above, any of the above-described (method 1) to (method 3) defective pixel position extraction algorithms can be used depending on the environment such as the type of sensor to be used. The important point is that
Because the exposure intensity is different, when shooting at a lower exposure dose, a pixel that maintains a relatively intermediate gradation as a defective pixel is
Since the absolute value of the difference between the defective pixel and the average of all pixels deviates greatly from the value obtained by multiplying the standard deviation by a predetermined magnification, it can be captured as a defective pixel. Therefore, by extracting the defective pixel position while variously changing the X-ray dose as described above, a pixel that greatly deviates from the variation in the output of the plane sensor 107 in imaging at each X-ray dose is determined as a defective pixel. Since the output behavior is determined, it is possible to accurately determine the defective pixel even for a pixel whose output behavior is not output at all, a pixel which always outputs a digitally large signal, and a pixel which outputs an intermediate value. It can be carried out.

If the X-ray dose falls outside the respective ranges, the photographing is performed again.

[Configuration of Pixel Gain Correction Processing and Defective Pixel Correction Processing]

As described with reference to FIGS. 2 to 8, when the collection of the defective pixel position information and the pixel gain information is completed, the pixel gain correction process using the information and the defective pixel Correction processing is performed. For this reason, the image correction unit 200 shown in FIG.
For example, as shown in FIG. 10, a pixel gain correction unit 221 that performs a pixel correction process using the pixel gain information stored in the pixel gain information storage unit 207, and an output of the pixel gain correction unit 221 and a defect position information storage unit The configuration further includes a defective pixel correction unit 222 that performs a defective pixel correction process using the defective pixel position information held in the 211.

First, the pixel gain correction unit 221 performs pixel correction processing on the photographed raw image information obtained by the normal photographing using the pixel gain information of the pixel gain information holding unit 207. Here, the pixel gain correction processing means that first, pixel gain information is obtained by taking pixels (input pixels) Pij of photographed raw image information so that the center of the image is close to 1.0, and Nij = Pij / (Average of 256 × 256 pixels in the central part of the image) is normalized by the following expression to obtain normalized pixel gain information Nij.

Then, as shown in the equation Oij = Pij / Nij, the input pixel Pij is divided by the normalized pixel gain information Nij of the pixel, and
A corrected pixel gain value (pixel gain correction value) Oij is obtained.

The above pixel gain correction value Oij is clipped so that the calculation result has 4095 gradations.
The overflow is 4095 gradations. Here, the calculation is performed by subtraction through a Log table using a Log operation formula of Log (Oij) = Log (Pij) −Log (Nij). The output value of this result is returned to "Oij" using an exponent table.

Here, when the above-described pixel gain correction processing is performed, the above calculation outputs a value that has no meaning at all with respect to the defective pixel. This is because the input photographed raw image is also stored in the pixel gain information holding unit 2 as described above.
This is because the pixel gain information held at 09 is also a meaningless value for the defective pixel. However, since the defective pixel portion is corrected by the defective pixel correction process in the defective pixel correction unit 222 that is performed subsequent to the pixel gain correction process, it is possible to obtain a captured image in which both the pixel gain and the defective pixel are corrected. it can. For example, the defective pixel correction unit 222 includes the pixel gain correction unit 2
The image information after the pixel gain correction processing obtained at 21 is used to determine the pixels around the defective pixel by using the defective pixel position information (including the defective pixel position information increased by the user) of the defect position information holding unit 211. Is corrected to overwrite the average value of the defective pixel value with the defective pixel value. Therefore, after the defective pixel correction processing by the defective pixel correction unit 222, the captured image finally obtained is a high-quality image in which both the pixel gain and the defective pixel have been corrected. In addition, since the above-described pixel gain information includes a defective pixel increased at the user's site, even if only the pixel gain information can be obtained, the defective pixel extraction processing according to the present embodiment can be performed. Thus, it is possible to reliably extract the defective pixels that have increased, which is convenient in terms of service.

Although the present embodiment has been described as being implemented by software for easier implementation and easier description, the present invention is not limited to this, and may be implemented by hardware. It is possible. In this case, the processing can be executed at higher speed.

In the present embodiment, the present invention is applied to X-ray imaging. However, the present invention is not limited to this, and can be applied to other imaging, for example, imaging using visible light.

Further, an object of the present invention is to supply a storage medium storing program codes of software for realizing the functions of the host and the terminal of the above-described embodiment to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) reading and executing a program code stored in a storage medium. In this case, the program code itself read from the storage medium implements the functions of the present embodiment, and the storage medium storing the program code constitutes the present invention. ROM, as a storage medium for supplying the program code,
Floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape,
A non-volatile memory card or the like can be used. By executing the program code read out by the computer, not only the functions of the present embodiment are realized, but also the OS and the like running on the computer perform actual processing based on the instructions of the program code. It goes without saying that a part or all of the above is performed, and the processing realizes the function of the present embodiment. Further, after the program code read from the storage medium is written to a memory provided in an extension function board inserted into the computer or a function extension unit connected to the computer, the function extension is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the present embodiment.

[0080]

As described above, according to the present invention, for example, at the time of calibration imaging (imaging for collecting information for image correction prior to normal imaging) of an X-ray digital imaging apparatus, at the time of factory shipment, etc. The digital image information collected by the shooting at this time is corrected (corrected) using the information on the initial defective pixel position (defective pixel position in the pixels configuring the flat sensor) which is known in advance, and then the corrected The defective pixel position information is extracted from the digital image information. The defective pixel position information obtained by this extraction is defective pixel position information that has increased on the user side of the shipping destination (position information of defective pixels that has increased while the user is using the flat sensor). If the increased defective pixel position information is to be subjected to image correction at the time of normal shooting, it is necessary to correct the increased defective pixel increased by the user in addition to the initial defective pixel known in advance at the time of factory shipment or the like. Can be. At this time, the defective pixel information may be collected a plurality of times, and in each pixel, only the pixels determined as defective more than the designated number of times may be determined as defective pixels. This can prevent an erroneous determination that a pixel that is not a defective pixel is treated as a defective pixel when electric noise or the like is superimposed on image output in normal shooting. Further, in normal photographing, pixel gain correction may be performed, and thereafter, defective pixel correction may be performed using the defective pixel information that has been increased by the user. Thereby, at the time of pixel gain correction, since the correction data includes a defective pixel increased at the user's site, the correction result is not correct for the defective pixel, but in the above-described defective pixel correction subsequent to the pixel gain correction, It will be corrected. Therefore, a defective pixel is not visible on a digital image obtained by normal photographing. Therefore, according to the present invention, regarding the defective pixels that increase while the user is using the flat sensor,
By performing the daily calibration work, the correction can be made surely, and a defective pixel which is not affected by electrical noise or the like can be obtained, so that a high quality captured image can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an X-ray imaging apparatus to which the present invention is applied.

FIG. 2 is a block diagram illustrating a configuration of an image correction unit of an image reading control unit of the X-ray imaging apparatus.

FIG. 3 is a diagram for explaining an example (method 1) of a defective pixel position extraction process in the image correction unit.

FIG. 4 is a flowchart for explaining the defective pixel position extraction processing (method 1).

FIG. 5 is a diagram for explaining an example (method 2) of a defective pixel position extraction process in the image correction unit.

FIG. 6 is a flowchart for explaining the defective pixel position extraction processing (method 2).

FIG. 7 is a diagram for explaining an example (method 3) of a defective pixel position extraction process in the image correction unit.

FIG. 8 is a flowchart for explaining the defective pixel position extraction processing (method 3).

FIG. 9 is a flowchart illustrating a process of extracting a defective pixel position while changing an X-ray dose in the image correction unit.

FIG. 10 is a block diagram illustrating a configuration of a pixel gain correction process and a defective pixel correction process in the image correction unit.

[Explanation of symbols]

 100 X image photographing device 118 CPU 110 Image reading control unit 200 Image correction unit 201 Dark current subtraction unit 202 Initial defect correction unit 203 Image check unit 204 Defect position extraction unit 205 Pixel gain information addition unit 206 Pixel gain information temporary storage unit 207 Pixel Gain information storage unit 208 Defect position synthesis unit 209 Defect position information temporary storage unit 210 Initial defect position synthesis unit 211 Defect position information storage unit 212 Increased defect position information storage unit 221 Pixel gain correction unit 222 Defective pixel correction unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H04N 5/32 A61B 6/00 350Z F-term (Reference) 4C093 AA01 AA26 CA01 EA12 EB12 EB24 FC11 FC16 FD01 FD03 FD11 FD13 FF01 FG05 FH06 GA06 5B047 AA17 AB02 BB04 DA06 5C024 AA12 AA14 BA02 CA09 HA10 HA14 HA17 HA21 HA24 5C061 BB11 CC09

Claims (17)

[Claims] 1. A method for acquiring defective pixel position information from correction image information obtained prior to collecting image information, and performing a defective pixel correction process on the image information using the defective pixel position information. An initial defect correction unit for performing a defective pixel correction process on the correction image information using previously obtained initial defective pixel position information; Defect position extracting means for extracting defective pixel position information from the image information subjected to the pixel correction processing; and defective pixel correction processing for the image information using the defective pixel position information obtained by the defect position extracting means. An image processing apparatus comprising: 2. The defect position extracting means includes a defect position synthesizing means for executing the defective pixel position information extracting process for a designated number of times of execution and sequentially synthesizing defective pixel position information obtained at each execution. The image processing apparatus according to claim 1, wherein: 3. The defect position extracting means executes the defective pixel position information extracting process for a designated number of times, and sequentially synthesizes defective pixel position information obtained each time the defect position extracting means executes the defective pixel position information extracting process. 2. The image processing apparatus according to claim 1, further comprising: a synthesis result of the defective pixel position information for the designated number of times of execution obtained by the position synthesizing means; and an initial defect position synthesizing means for synthesizing the initial defective pixel position information. apparatus. 4. The defect position synthesizing means includes a defect position information storing means for holding a synthesis result up to this time for synthesizing processing at the time of next processing execution. The image processing apparatus according to any one of the preceding claims. 5. A pixel information storage unit capable of storing information on the number of times of determination of a defective pixel in correspondence with the defective pixel position information for each pixel, wherein the defect position synthesizing unit is adapted to combine the defective pixel position information. 4. The image processing apparatus according to claim 2, wherein an addition process of the number-of-determinations information is performed. 6. The method according to claim 1, wherein the defect position extracting unit determines a result of the combining process performed by the defect position combining unit or the initial defect position combining unit after executing the process for the designated number of executions within the designated execution number. 4. The image processing apparatus according to claim 2, wherein the position information of the pixel which is determined as a defective pixel and exceeds the designated number of determinations is determined as the defective pixel position information. 7. An image according to claim 1, further comprising a pixel gain correction means for performing the pixel gain correction processing at the time of photographing for collecting the image information prior to the processing by the defect correction means. Processing equipment. 8. The image processing apparatus according to claim 1, wherein said image information is information obtained by digitizing image information obtained by radiography. 9. An image processing system in which a plurality of devices are connected to be able to communicate with each other, wherein at least one of the plurality of devices is the image processing apparatus according to claim 1. An image processing system having the following functions. 10. An image processing method for collecting defect position information prior to collecting image information, and performing defective pixel correction of the image information using the defect position information, the image processing method comprising: An initial defect correction step of performing a defective pixel correction process using previously collected initial defective pixel position information on correction image information obtained by photographing to collect information; A defect position extracting step of collecting defective pixel position information from the image information subjected to the defective pixel correction processing in the step. 11. An execution step of executing the process of collecting the defective pixel position information for a designated number of times, a defect position synthesizing step of synthesizing the defective pixel position information for each execution of the execution step, A defect position information storing step of holding the defective pixel position information obtained by the defect position synthesizing step at the time of executing the defect position information storing means for a synthesizing process in the defect position synthesizing step at the next execution. The image processing method according to claim 10, further comprising: 12. An execution step of executing the process of collecting the defective pixel position information a specified number of times, a defect position synthesizing step of synthesizing the defective pixel position information for each execution of the execution step, A defect position information storing step of holding the defective pixel position information obtained by the defect position synthesizing step at the time of executing the defect position information storing means for a synthesizing process in the defect position synthesizing step at the next execution. After the completion of the synthesizing process in the defect position synthesizing step for the specified number of times, an initial defect position synthesizing step of synthesizing the defective pixel position information held in the defect position information storage means and the initial defect position information. The image processing method according to claim 10, wherein: 13. After the completion of the synthesizing process in the defect position synthesizing step for the specified number of times, the result of the synthesizing process in the defect position synthesizing step or the initial defect position synthesizing step is designated within the specified number of times. 13. The image processing method according to claim 11, further comprising: determining position information of a pixel determined as a defective pixel exceeding the number of determinations as the defective pixel position information. 14. A pixel gain correcting step for performing the pixel gain correcting process at the time of photographing for collecting image information prior to the defective pixel correcting process using the defective pixel position information. Item 11. The image processing method according to Item 10. 15. The image processing method according to claim 10, wherein the image information is information obtained by digitizing image information obtained by radiography. 16. In the defect position synthesizing step, when performing the synthesizing process in the defect position synthesizing step, the defect position information storage means is provided with a count for a storage unit for holding the number of times of determining that the pixel is defective. 13. The method according to claim 11, further comprising the step of performing a number-of-determinations process for performing an up process.
The image processing method described in the above. 17. A computer readable storage for processing steps for collecting defect position information prior to collecting image information and performing a defective pixel correction of the image information using the defect position information. A storage medium according to claim 10, wherein said processing steps include each step of the image processing method according to any one of claims 10 to 16.