JP2011101419A - Image processing apparatus, computer-readable storage medium and digital imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speedily correct gain variance which is based on the sensitivity of a solid-state imaging device for each pixel of a photographed image, by using a correction table corresponding to the solid-state imaging device to be used, in a system where a plurality of solid-state X-ray imaging devices are used while being switched. <P>SOLUTION: Image data 30 obtained by radiating X-rays while no subject are stored in a storage device 39 as a value of a gain table. This is performed on each of a plurality of solid-state imaging devices. One of a plurality of stored gain tables is read out in accordance with the solid-state imaging device to be used, and written in a gain table 45. A subject is then placed and irradiated with X-rays and obtained image data 30 of the subject are gain-corrected using the gain table 45 in a computing element 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus suitable for use in an X-ray digital imaging apparatus using a solid-state imaging apparatus, a computer-readable storage medium, and a digital imaging apparatus.

For X-ray imaging for the purpose of medical diagnosis, a film screen system in which an intensifying screen and an X-ray photographic film are combined is often performed. According to this method, the X-rays that have passed through the subject contain internal information of the subject, which is converted into visible light proportional to the intensity of the X-rays by the intensifying screen to expose the X-ray photographic film, An image is formed on the film.
Recently, an X-ray digital imaging device is used that converts X-rays into visible light proportional to the intensity of X-rays using a phosphor, converts them into electrical signals using photoelectric conversion elements, and converts them into digital signals. Being started. As this photoelectric conversion element, there is one using amorphous silicon, and a two-dimensional sensor is configured by arranging the photoelectric conversion elements in a matrix.

  Each photoelectric conversion element of the two-dimensional sensor forms one pixel. However, since the sensitivity (gain) of the photoelectric conversion element differs from pixel to pixel, it is necessary to correct this sensitivity difference. In addition, since X-rays are output radially from the X-ray generator, there is a difference in the X-ray intensity incident on the pixel depending on the location. As these correction methods, X-rays are irradiated without placing a subject in front of the imaging apparatus, and the gain corresponding to the image size obtained by normalizing other pixels with the maximum value of the pixel value being 1 from the image obtained at that time Make a table. Then, each pixel value of the X-ray image taken by placing the subject is divided by a value corresponding to each pixel of the gain table. As an actual method, there are a method in which a photographed X-ray image is calculated in software by a CPU, and a method in hardware as shown in FIG.

  In FIG. 4, the gain table 11 in the image capturing device 10 is controlled by the controller 12, and in the state where the buffer 13 is enabled so as to write data, first, X-rays are exposed without placing a subject. To get. The image data is input from the image input line 14. This image data is LOG-converted through a lookup table 15 for LIN / LOG conversion, and is written in the gain table 11 as a gain value G through the buffer 13. Next, with the buffer 13 disabled, the subject is placed and X-rays are emitted to obtain the subject image. The image data input from the image input line 14 is LOG-transformed through the lookup table 15 and input to the calculator 16.

  The controller 12 reads the gain table 11 at the same timing when the X-ray image is input to the calculator 16, and the read data is input to the calculator 16. The computing unit 16 performs subtraction for each pixel between the gain value G from the gain table 11 and the subject image. The output of the arithmetic unit 16 is LIN-converted through a look-up table 17 for LOG / LIN conversion, and is output from the interface 18 as a corrected image.

  Here, when G is the gain value of the gain table output and X is the pixel value of the subject image, log (G / X) = logG−logX is converted into X / G * C in the lookup table 17. The table has been written. That is, C * (10 to the power of −i) (i is an input value to the lookup table 17 = log (G / X)). At this time, C is a constant determined in advance so that X / G is an integer equal to or greater than 1. For example, if the maximum value of the gain value G is 12 bits at most, C = 2 12 = 4096.

  Next, some photoelectric conversion elements (defective pixels) that do not function normally exist due to manufacturing problems. It is difficult to manufacture a solid-state imaging device having no defective pixels at all with the current technology. Normally, defective pixels are interpolated by guessing from surrounding pixels. As an actual method, there are a method in which a photographed X-ray image is calculated in software by a CPU, and a method in hardware as shown in FIG.

  In FIG. 5, the defective pixel table 21 in the image capturing device 20 is controlled by the controller 22. First, in a state where the buffer 23 is enabled so as to write data, an X-ray is emitted without placing a subject to acquire an image. The image data is input from the image input line 24. The defect determination unit 25 determines that the input image data value is less than a certain value as a defective pixel, writes “1” in the defect pixel table 21 via the buffer 23, and determines that a certain value or more is a normal pixel. Determination is made and “0” is written in the defective pixel table 21. At this time, the input image data is input to the calculator 26 as it is.

  Next, with the buffer 23 disabled, the subject is placed and X-rays are emitted to obtain the subject image. The image data input from the image input line 24 passes through the defect determination unit 25 and is input to the calculator 26. The controller 22 reads the defective pixel table 21 at the same timing when the subject image is input to the calculator 26, and the read data D is input to the calculator 26. In the arithmetic unit 26, when the defective pixel table value D is “1”, the pixel is invalid, the defective pixel is interpolated by using the previous pixel, and the corrected image is output through the interface 27. .

  However, the resolution and size of the solid-state imaging device have been improved day by day. At present, the number of pixels of 2000 × 2000 or more has come out, and the total number of pixels becomes 4M pixels or more. In the case of using software, since processing time is required to some extent, it has become a bottleneck for immediately displaying a photographed X-ray image. In addition, it is conceivable that an X-ray sensor unit including two or more solid-state imaging devices is connected, and these X-ray sensor units are switched and used. It was difficult because of the need to expose the line. In other words, in the hardware correction method described above, in order to write a gain value in the gain table 11, the number of X-ray exposure circuits must be increased. The above has the same problem with the defective pixel table.

  In the image processing apparatus according to the present invention, correction means for correcting input image data using a correction table, storage means for storing the correction table, and the correction means for reading out the stored correction table. And a control means for performing control given to.

  In another image processing apparatus according to the present invention, correction means for correcting input image data using a correction table, storage means for storing the correction table, and a correction table connected to the storage means. General-purpose bus means for rewriting and control means for reading out the stored correction table and giving control to the correction means are provided.

  In a computer-readable storage medium according to the present invention, a procedure for storing a correction table, a procedure for reading out the stored correction table and giving it to a correction unit, and input image data for correction by the correction unit A program for executing a correction procedure using a table is stored.

  In another computer-readable storage medium according to the present invention, a procedure for storing a correction table in a storage unit, a procedure for reading out the stored correction table and giving it to the correction unit, and input image data A program for executing a procedure for correcting using the correction table of the correction means and a procedure for rewriting the correction table of the storage means through a general-purpose bus is stored.

  The digital photographing device according to the present invention has a solid-state imaging device, and the image capturing device has a correction table necessary for correcting an image obtained from the solid-state imaging device. Arbitrary data can be written from a processing device connected to the bus and connected to the general-purpose bus, and connected to a controller that reads the correction table for correcting the image.

  The correction table is for correcting a gain difference for each pixel in the imaging apparatus for obtaining image data, or correcting a defective pixel in the imaging apparatus for obtaining image data.

  According to the present invention, the gain table and the defective pixel table are stored in advance and can be rewritten, so that the stored gain values and defective pixels can be stored even when the imaging unit such as the X-ray sensor unit is replaced. It can respond promptly by writing the table value. In particular, in the case of X-ray imaging, even if the X-ray sensor unit is replaced, it can be handled without exposing X-rays.

  The rewriting can be performed by a processing device through a general-purpose bus.

It is a block diagram which shows the 1st Embodiment of this invention. It is a block diagram which shows the 2nd Embodiment of this invention. It is a block diagram which shows embodiment of the whole X-ray imaging system by this invention. It is a block diagram which shows a prior art example. It is a block diagram which shows another prior art example.

  FIG. 3 is a diagram showing an embodiment of an X-ray imaging apparatus using the present invention. In FIG. 3, X-rays output from the X-ray generator 1 pass through the subject 2 and enter the X-ray sensor unit 3 attached to the gantry 9. The incident X-ray includes internal information of the subject 2 and is converted into visible light proportional to the intensity of the X-ray by the phosphor 5 of the solid-state imaging device 4 inside the X-ray sensor unit 3 to be subjected to photoelectric conversion. The device 6 converts it into a charge proportional to the visible light. Then, it is digitized by AD conversion and transferred to the control unit 7. Here, AD conversion may be performed inside the X-ray sensor unit 3 or may be performed by the control unit 7. The transferred image data is displayed on the display unit 8. The control unit 7 is connected with an imaging unit composed of 101 to 106 and 109 similar to the above 1 to 6 and 9, and switching of imaging is possible.

  FIG. 1 shows a first embodiment of the control unit 7 and relates to the above-described gain correction. In FIG. 1, image data 30 transferred from the X-ray sensor unit 3 or 103 in FIG. 3 enters an image capturing device 31, a lookup table 32 for LIN / LOG conversion, a calculator 33, a buffer 34, and a lookup. The data is transferred to and stored in a storage device 39 as a storage means managed by a CPU 38 (control means) as a processing device via a general-purpose bus interface IF 37 through a table 35 and a buffer 36. Here, the bus of FIG. 1 and the general-purpose bus interface IF 37 constitute general-purpose bus means, and the calculator 33 and the gain table 45 (correction table) constitute correction means.

  In order to obtain the gain value G, first, the CPU 38 disables the buffer 34, enables the buffer 40, sets the data direction of the buffer 36 to α, and sets the LIN / LIN conversion table in the lookup table 35 so that the data passes through. Write. At this time, the controller 41 generates a control signal LUT0_cont for the lookup table 35. Next, the CPU 38 sets the buffer 34 to be valid, the buffer 40 is invalid, the data direction of the buffer 36 is β, and the arithmetic unit 33 is set so that the data passes.

  Then, an image is acquired by exposing X-rays without placing a subject. This image data 30 is LOG-converted through a lookup table 32, passes through the computing unit 33, buffer 34, lookup table 35, and buffer 36, and is transferred to the storage device 39 managed by the CPU 38 via the general-purpose bus interface IF 37. And saved as a gain value. Next, the CPU 38 writes the gain value acquired in the gain table 45 with the buffer 42 disabled, the buffer 43 enabled, and the data direction of the buffer 44 as α. At this time, the controller 41 generates a control signal TBL_cont for the gain table 45.

  Next, the buffer 34 is disabled, the buffer 40 is enabled, the data direction of the buffer 36 is α, and C * (10 to the power of −i) shown in the conventional example in the lookup table 35 (i is the lookup table 35). Write a conversion table such that input value = log (G / X)). The buffers 34 and 42 are enabled, the buffers 40 and 43 are disabled, the data direction of the buffers 36 and 44 is β, and the calculator 33 is set so that the gain table output and the subject image are subtracted for each pixel. .

  Next, the subject is placed and X-rays are emitted to obtain a subject image. The image data 30 is LOG-transformed through a lookup table 32 and input to the calculator 33. The controller 41 reads the gain table 45 at the same timing when the subject image is input to the calculator 33, and the read data is input to the calculator 33. The computing unit 33 performs subtraction for each pixel between the gain table output and the subject image. The output of the computing unit 33 is LIN-converted through the lookup table 35, output as a corrected image, transferred to the storage device 39 managed by the CPU 38 via the general-purpose bus interface IF 37, and stored.

  As described above, all gain tables of the plurality of X-ray sensor units 3 and 103 to be connected are acquired in the storage device 39 in advance, and each time the X-ray sensor units 3 and 103 are changed, the X-ray sensors are acquired. Write to the gain table 45 from the storage device 39 according to the unit.

  Note that the ROM 46 and the storage device 39 in FIG. 1 constitute a storage medium according to the present invention. That is, the ROM 46 stores a program for executing the above-described processing procedure, and the storage device 39 stores a plurality of gain tables. As these storage media, a semiconductor memory, an optical disk, a magneto-optical disk, a magnetic medium, or the like is used.

  Next, a second embodiment relating to the defective pixel table will be described. Here, it is assumed that the X-ray image is captured as shown in FIG. 3 as in the first embodiment. FIG. 2 shows a second embodiment of the control unit 7 of FIG. 2, image data 50 transferred from the X-ray sensor unit 3 or 103 in FIG. 3 enters the image capturing device 51, passes through the arithmetic unit 52 and the buffer 53, and functions as a processing device via the general-purpose bus interface 54. The data is transferred to and stored in a storage device 56 as storage means managed by the CPU 55 (control means). Here, the bus of FIG. 2 and the general-purpose bus interface IF 54 constitute general-purpose bus means, and the calculator 52 and the defective pixel table 60 (correction table) constitute correction means.

  In order to acquire the defective pixel determination bit, first, the CPU 55 sets the buffer 53 to be valid, sets the data direction of the buffer 57 to α, and sets the calculator 52 so that the data passes through. Then, X-rays are emitted without placing a subject to acquire image data 50, pass through the computing unit 52 and buffer 53, and are transferred to the storage device 56 managed by the CPU 55 via the general-purpose bus interface IF 54. Saved.

  Then, the CPU 55 determines that a value less than or equal to a certain value from this data is a defective pixel, sets the defect pixel table value at that time to “1”, sets the value above a certain value as a normal pixel, and sets the defect pixel table value to “0” "In the storage device 56. When the determination is completed for all the pixels, the buffers 58 and 53 are disabled, the buffer 57 is enabled, the data direction of the buffer 57 is α, and the completed defective pixel table is written in the defective pixel table 60. At this time, the controller generates a control signal TBL_cont for the defective pixel table 60. Then, the buffers 53 and 58 are enabled, the buffers 57 and 59 are disabled, and the calculator 52 is set so that defective pixel interpolation is performed.

  Next, the subject is placed and X-rays are emitted, and the subject image data 50 is input to the calculator 52. The controller 61 reads the defective pixel table 60 at the same timing when the subject image is input to the calculator 52, and the read data is input to the calculator 52. In the arithmetic unit 52, when the defective pixel table value = 1, the pixel is invalid, and the defective pixel is interpolated by using the previous pixel and transferred to the storage device 56 via the general-purpose bus interface IF54. Saved.

  As described above, all defective pixel tables of the plurality of X-ray sensor units 3 and 103 to be connected are acquired in the storage device 56 in advance, and written to the defective pixel table 60 every time the X-ray sensor unit is changed. I do. The ROM 62 and the storage device 56 in FIG. 2 constitute a storage medium according to the present invention in the same manner as the ROM 46 and the storage device 39 in FIG.

DESCRIPTION OF SYMBOLS 1,101 X-ray generator 2,102 Subject 3,103 X-ray sensor part 4,104 Solid-state imaging device 5,105 Phosphor 6,106 Photoelectric converter 7,107 Control part 30,50 Image data 31,51 Image capture Device 32, 35 Look-up table 33, 52 Calculator 38, 55 Processing device (CPU)
39, 56 Storage device 41, 61 Controller 46, 62 ROM

Claims (14)

Correction means for correcting input image data using a correction table;
Storage means for storing the correction table;
An image processing apparatus comprising: a control unit that reads out the stored correction table and applies the control to the correction unit. Correction means for correcting input image data using a correction table;
Storage means for storing the correction table;
General-purpose bus means connected to the storage means for rewriting the correction table;
An image processing apparatus comprising: a control unit that reads out the stored correction table and applies the control to the correction unit.   The image processing apparatus according to claim 1, wherein the correction table is for correcting a gain difference for each pixel in an imaging apparatus for obtaining the image data.   The image processing apparatus according to claim 1, wherein the correction table is for correcting defective pixels in an imaging apparatus for obtaining the image data.   The storage means stores a plurality of correction tables corresponding to a plurality of switchable imaging apparatuses used to obtain the image data, and the control means includes a correction table corresponding to the selected imaging apparatus. The image processing apparatus according to claim 1, wherein the image processing device is read from the storage unit. A procedure for storing a correction table;
A procedure for reading the stored correction table and giving it to the correction means;
A computer-readable storage medium storing a program for causing a computer to execute a procedure for correcting input image data using a correction table of the correction means. A procedure for storing the correction table in the storage means;
A procedure for reading the stored correction table and giving it to the correction means;
A procedure for correcting the input image data using a correction table of the correction means;
A computer-readable storage medium storing a program for causing a computer to execute a procedure for rewriting the correction table of the storage means through a general-purpose bus.   8. The computer-readable storage medium according to claim 6 or 7, wherein the stored correction tables are a plurality of correction tables corresponding to a plurality of imaging devices for obtaining the image data.   8. The computer-readable storage medium according to claim 6, wherein the correction table is for correcting a gain difference for each pixel in an imaging apparatus for obtaining the image data.   The computer-readable storage medium according to claim 6 or 7, wherein the correction table is for correcting a defective pixel in an imaging apparatus for obtaining the image data.   In a digital imaging device having a solid-state imaging device, the image capturing device has a correction table necessary for correcting an image obtained from the solid-state imaging device, and the correction table is connected to a general-purpose bus, and the general-purpose bus A digital photographing device characterized in that data can be written from a processing device connected to the digital camera and is connected to a controller that reads the correction table for correcting the image.   12. The digital imaging apparatus according to claim 11, wherein the solid-state imaging device is sensitive to X-rays, and an image obtained from the solid-state imaging device is an X-ray image.   12. The digital photographing apparatus according to claim 11, wherein the correction table is for correcting a gain difference for each pixel of the solid-state imaging device.   12. The digital photographing apparatus according to claim 11, wherein the correction table is for correcting defective pixels of the solid-state imaging device.

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