JP5276423B2 - Image shooting device - Google Patents

Description

  The present invention relates to an image capturing apparatus, and more particularly to a data correction process in an X-ray image capturing apparatus.

  An X-ray imaging apparatus using a flat detector is known. There are various types of flat detectors. For example, there is known a flat detector that detects X-rays by using amorphous silicon or polysilicon formed and formed on a glass substrate as a material and two-dimensionally arranging photoelectric conversion elements and TFTs. In such a flat panel detector, charges are read out by performing matrix driving using TFTs on the charges photoelectrically converted by the photoelectric conversion elements.

  In addition, flat detectors that can capture moving images as well as still images have been developed (see, for example, Patent Document 1).

  A flat detector usually has a defective pixel. There is a problem that the image quality of the photographed image deteriorates due to the presence of the defective pixel. For this reason, it is necessary to correct defective pixels. Defect information such as defective pixel positions in the flat detector is detected and stored in advance, and defect correction is performed based on the defect information during imaging. In the defect correction, the value of the defective pixel is generally corrected with a value obtained by interpolating from the peripheral pixels of the defective pixel, for example.

  In the X-ray imaging apparatus, recursive filter processing having a motion detection function is used when displaying or saving an image read from a flat detector. This is to suppress X-ray moving image capturing at a low dose when capturing an X-ray moving image, and to suppress noise caused by the reduction in dose.

  A method related to a recursive filter having a motion detection function is disclosed in Patent Document 2, for example. According to Patent Document 2, the image data of the current frame is subjected to spatial filter processing, and the image data of the previous frame is stored in the frame memory. Motion detection is performed from the relationship between the image data of the current frame and the image data of the previous frame. When motion is detected, the current frame image is switched to image data that has undergone spatial filtering. The motion detection function determines that it has moved when the local average value of the image data of the previous frame and the image data of the current frame exceeds a predetermined value.

  A schematic block diagram of a conventional X-ray imaging apparatus is shown in FIG.

  The X-ray imaging apparatus is roughly composed of a plane detection unit 20 having the plane detector 1 and an image processing unit 21 that processes image data transferred from the plane detection unit 20. The plane detection unit 20 includes a defect correction unit 30 and a transmission unit 2 in addition to the plane detector 1. On the other hand, the image processing unit 21 includes a reception unit 3, a transfer error detection unit 4, a transfer error correction unit 31, and a recursive filter unit 32.

  The flat detector 1 is a flat detector in which photoelectric conversion elements and TFTs are two-dimensionally arranged as described above.

  FIG. 6 is a diagram for explaining an example of data correction processing performed by the defect correction unit 30. In the figure, x is a defective pixel, and a, b, c, and d are normal pixels. For example, the defect correction unit 30 corrects the defective pixel using four pixels around the defective pixel. In this case, the corrected pixel x ′ of the defective pixel x is expressed by the following equation.

      x '= (a + b + c + d) / 4 (1)

  In the case of an X-ray imaging apparatus, since the plane detection unit 20 and the image processing unit 21 are often separated from each other in distance, the transmission unit 2 is necessary. The transmission unit 2 adds an error detection code to the data read from the flat detector 1 and transfers the data to the image processing unit 21. The error detection code is a code for making it possible to determine whether data corruption has occurred during data transfer. There are various error detection codes. For example, CRC (Cyclic Redundancy Check Character) is used.

  The reception unit 3 receives the data transmitted from the transmission unit 2, and the transfer error detection unit 4 determines from the added error detection code whether the data is garbled during data transfer.

  When the transfer error detection unit 4 detects a transfer error, the transfer error correction unit 31 corrects the data transfer error. The transfer error correction unit 31 has the same structure as that of the defect correction unit 30, and a pixel in which a data transfer error has occurred is corrected using normal pixels around it.

  FIG. 7 is a diagram illustrating an example of data correction processing performed by the transfer error correction unit 31. In the figure, e1, e2, and e3 are pixels having a data transfer error, and a and c are pixels having no data transfer error. When the transfer error correction unit 31 corrects four pixels around the pixel in which the data transfer error has occurred, the pixel e2 in which the data transfer error has occurred is corrected using only the pixels a and c in which the data transfer has not occurred. . In this case, the corrected pixel e2 'of the defective pixel e2 is expressed by the following equation.

      e2 '= (a + c) / 2 (2)

  e1 and e3 are similarly corrected.

  The corrected data is subjected to a recurve filter process by a recursive filter unit 32 having a motion detection function, and the processed data is displayed on a display device (not shown) or stored in a storage unit.

JP2003-078124 Japanese Unexamined Patent Publication No. 06-047036

  However, in order to correct defective pixels and data transfer errors, the conventional X-ray imaging apparatus requires a defect correction unit 30 in the plane detection unit 20, a transfer error correction unit 31 in the image processing unit 21, and two correction units. there were. Therefore, the conventional X-ray imaging apparatus has a problem that the cost becomes high.

  In order to avoid this high cost, a method of omitting the transfer error correction unit 31 can be considered, but in this case, a pixel in which a data transfer error has occurred enters the recursive filter unit 32 having a motion detection function. As described above, the recursive filter unit 32 generates a data transfer error in order to determine that it has moved when the local average value of the image data of the previous frame and the image data of the current frame exceeds a predetermined value. It is determined that the pixel is a motion. If it is determined that the image is moving, the image of the current frame in which a data transfer error has occurred is switched to the spatially filtered data, so that abnormal pixel values are displayed on the display unit or stored in the storage unit. There is a problem that it ends up.

  An object of the present invention is to provide an X-ray imaging apparatus capable of correcting a defect of a flat panel detector and a data transfer error with a simpler configuration.

According to one aspect of the present invention, a receiving means for receiving data of each pixel read from the flat surface detector, a detector for detecting transmission errors of the received data, defective pixels of the flat panel detector A first storage means for preliminarily storing the position of the first pixel, and a first pixel based on a predetermined peripheral pixel of the defective pixel in accordance with a relationship between the position of the pixel where the transfer error is detected by the detection means and the position of the defective pixel A correction unit that corrects the defective pixel data by selecting one defective pixel correction method or a second defective pixel correction method using the current frame data and the previous frame data; Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can correct | amend the defect of a plane detector and a data transmission error with a simpler structure is provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, It shows only the specific example advantageous for implementation of this invention. In addition, not all combinations of features described in the following embodiments are indispensable as means for solving the problems of the present invention.

  FIG. 1 is a block diagram showing a configuration of an X-ray imaging apparatus which is an image imaging apparatus in the present embodiment.

  As shown in FIG. 1, the X-ray imaging apparatus according to the present embodiment includes a plane detection unit 10 and an image processing unit 11. The plane detection unit 10 and the image processing unit 11 are substantially the same as the plane detection unit 20 and the image processing unit 21 in the conventional example shown in FIG. 5, but the plane detection unit 10 of FIG. The image processing unit 11 includes a defect correction unit 5 instead of the transfer error correction unit 31. The recursive filter unit 6 is different from the conventional recursive filter unit 32.

  Accordingly, the plane detection unit 10 includes a plane detector 1 in which pixels including detection elements that detect incident X-rays are two-dimensionally arranged, and a transmission unit 2 that transmits data read from the plane detector 1. The The image processing unit 11 includes a receiving unit 3, a transfer error detecting unit 4, a defect correcting unit 5, and a recursive filter unit 6. Note that the plane detector 1, the transmission unit 2, the reception unit 3, and the transfer error detection unit 4 are the same as those in the conventional example, and therefore, the same reference numerals are used and description thereof is omitted.

  The transfer error detection unit 4 detects a data transfer error based on an error detection code such as CRC, and if there is a data transfer error, outputs information (41) on the position where the data transfer error has occurred. The data received by the receiving unit 3 is output (40).

  The defect correction unit 5 corrects the data (40) input to the defect correction unit 5 based on the defective pixel of the flat detector 1 and the data transfer error position information (41) output from the transfer error detection unit 4. To output (50). However, since the defect correction unit 5 cannot correct all of the defective pixels of the flat panel detector 1 and the pixels in which the data transfer error has occurred, if there is a pixel that could not be corrected, the position information (51) is obtained. Output.

  The recursive filter unit 6 corrects and outputs (60) the recursive filter process and the data (50) that cannot be corrected by the defect correcting unit 5 using the position information (51).

  Data (60) output from the recursive filter unit 6 is displayed on a display device (not shown) or stored in a storage unit.

  FIG. 2 is a block diagram showing the configuration of the defect correction unit 5.

  The defect correction unit 5 includes a first storage unit 52, a second storage unit 53, a determination unit 54, a third storage unit 55, and a correction unit 56. The first storage unit 52 stores in advance information on the position of the defective pixel of the flat detector 1. The second storage unit 53 stores information (41) of the position where the data transfer error has occurred, transmitted from the transfer error detection unit 4.

  As illustrated in FIG. 6, the defect correction unit 5 corrects the defective pixel using a predetermined number of peripheral pixels (for example, four peripheral pixels) of the defective pixel that is the target pixel. Specifically, the data of the pixel of interest is replaced with the average value of the peripheral pixels by the above-described equation (1).

  Further, as shown in FIG. 7, there may be a case where a transfer error or a defective pixel is included in the peripheral pixels of the defective pixel which is the target pixel. In this case, the defect correcting unit 5 replaces the data of the target pixel with an average value of normal data among a predetermined number of peripheral pixels of the target pixel as in the above-described equation (2).

  The determination unit 54 determines whether or not an abnormal pixel can be corrected based on the position information of the defective pixel stored in the first storage unit 52 and the position information stored in the second storage unit 53. When a pixel of interest is a defective pixel and is corrected from a predetermined number of peripheral pixels, if a data transfer error as shown in FIG. 7 occurs, it is determined that correction can be made using equation (2).

  FIG. 4 is a diagram illustrating a case where the correction unit 56 determines that correction cannot be performed.

  In FIG. 4, x1 and x2 indicate defective pixels of the flat detector 1, and e1, e2, and e3 indicate data transfer error pixels. The target pixel e2 is a pixel in which a transfer error is detected. The surrounding four pixels are defective pixels x1 and x2, and data transfer error pixels e1 and e3. For this reason, it is determined that the pixel of the target pixel e2 cannot be corrected.

  Information on the position of the pixel determined by the correction unit 56 to be uncorrectable is stored in the third storage unit 55 and output (51) to the next recursive filter unit 6. Further, the data (40) entered in the defect correction unit 5 enters the correction unit 56, and the pixels determined to be correctable by the determination unit 56 are corrected by the correction unit 56 and output (50). Data that could not be corrected by the defect correction unit 5 enters the next recursive filter unit 6.

  FIG. 3 is a block diagram showing the configuration of the recursive filter unit 6.

  The recursive filter unit 6 performs a process for reducing noise by adding a weighted previous frame image to the current frame image obtained from the data output from the defect correction unit 5. Specifically, the recursive filter unit 6 includes a motion detection unit 61, a spatial filter unit 62, a frame memory unit 63, a switching unit 64, and a recursive filter calculation unit 65.

  The motion detector 61 detects motion from the relationship between the current frame image and the previous frame image. The spatial filter unit 62 performs spatial filtering on the current frame image to suppress noise in the current frame image. The frame memory unit 63 stores the data of the previous frame image.

  The switching unit 64 switches the connection with the recursive filter calculation unit 65 to the spatial filter unit 62 when the motion detection unit 61 detects a motion. On the other hand, when the motion detection unit 61 does not detect a motion, the connection is switched to the frame memory unit 63.

  Further, the switching unit 64 also receives information (51) on the position that could not be corrected by the defect correcting unit 5. When the target pixel in the recursive filter calculation unit 65 becomes a pixel at a position that cannot be corrected by the defect correction unit 5, the switching unit 64 forcibly switches the connection with the recursive filter calculation unit 65 to the frame memory unit 63. .

  The recursive filter calculation unit 65 uses the current frame image and the image input via the switching unit 64 to perform calculation according to the following equation for each pixel.

Po _n (x, y) = (1-a) · Pi _n (x, y) + a · Po _n-1 (x, y) (3)

Here, a is a recursive filter coefficient, Pi _n (x, y) is pixel data at positions x and y in the current frame image, and Po _n−1 (x, y) is a position input via the switching unit 64. It is pixel data of x and y. Then, the recursive filter calculation unit 65 outputs the recursive filter output data Po _n (x, y) calculated by the equation (3). However, the pixel at the position (51) that could not be corrected by the defect correction unit 5 is replaced with the data of the pixel of the previous frame with the recursive filter coefficient a being 1.

  Accordingly, when a pixel at a position that cannot be corrected by the defect correction unit 5 becomes a target pixel, the switching unit 64 is switched to the frame memory, and the recursive filter coefficient a of the recursive filter calculation unit 65 is set to 1. For this reason, it becomes equal to the pixel of the previous frame, and a pixel that cannot be corrected by the defect correction unit 5 can be corrected.

  In the above-described embodiment, the defect correction unit 5 corrects from defective pixels or normal pixels around the four pixels around the pixel in which the data transfer error has occurred. However, the present invention is not limited to this. For example, a method of correcting from normal pixels of the surrounding 8 pixels may be used. Note that the determination method of the determination unit 54 varies depending on the correction method.

  Further, in the first storage unit 52, the second storage unit 53, and the third storage unit 55, there are various methods for storing the positions of abnormal values. As a typical example, there is a method of storing pixels having abnormal values in xy coordinates, but the present invention is not limited to this method.

  Although the error detection code has been described as CRC, there are various methods for error detection code. For example, there are a method of adding an error detection code in units of several bits and a method of adding an error detection code for every several tens of pixels. Therefore, for example, instead of CRC, for example, an RS code (Reed Solomon Coding) that is an error correction code may be used as the error detection code.

  There are various transmission methods in the transmission unit 2 and the reception unit 3. For example, there are a method in which data is transmitted as an electrical signal, a method in which data is converted into an optical signal and transmitted, a method in which data is transmitted in parallel, and a method in which data is transmitted in serial. Any of these transmission schemes can be used in the present invention. Furthermore, the distance between the transmission unit 2 and the reception unit 3 is not limited in the present invention.

  In addition, as the motion detection method of the motion detection unit 61, in the above-described embodiment, motion detection is performed from the relationship between the image data of the current frame and the image data of the previous frame. However, the present invention is not limited to this. For example, motion detection may be performed from the image data subjected to the spatial filter by the spatial filter unit 62 and the image data stored in the frame memory unit 63.

  The flat detector 1 is a flat detector that detects X-rays, but is not limited thereto. For example, a flat detector that detects visible light may be used.

It is a block diagram which shows the structure of the X-ray imaging apparatus in embodiment. It is a block diagram which shows the structure of the defect correction part in embodiment. It is a block diagram which shows the structure of the recursive filter part in embodiment. It is a figure explaining the case where it determines with the correction | amendment part in embodiment not being able to correct | amend. It is a block diagram which shows the structure of the conventional X-ray imaging apparatus. It is a figure explaining the example of the data correction process with respect to the defective pixel of a plane detector. It is a figure explaining the example of the data correction process which concerns on a transfer error.

Explanation of symbols

1: Plane detector 2: Transmission unit 3: Reception unit 4: Transfer error detection unit 5: Defect correction unit 6: Recursive filter unit 10: Plane detection unit 11: Image processing unit

Claims (8)

A receiving means for receiving data of each pixel read from the flat surface detector,
Detecting means for detecting a transfer error of the received data;
First storage means for storing in advance the positions of defective pixels of the flat panel detector;
A first defective pixel correction method based on a predetermined peripheral pixel of the defective pixel or a current frame of the current frame in accordance with the relationship between the position of the pixel where the transfer error is detected by the detection means and the position of the defective pixel A correction means for correcting the data of the defective pixel by selecting a second defective pixel correction method using the data and the data of the previous frame ;
An image photographing apparatus comprising: When the predetermined peripheral pixel of the defective pixel is occupied by at least one of a pixel in which a transfer error is detected by the detection unit and another defective pixel, the data of the defective pixel is used as the first defective pixel. And a determination means for determining that the correction cannot be performed by the correction method.
The correction unit selects the second defective pixel correction method when the determination unit determines that the data of the defective pixel cannot be corrected by the first defective pixel correction method; The image capturing apparatus according to claim 1, wherein a correction method for the first defective pixel is selected . Second storage means for storing a position of a pixel in which a transfer error is detected by the detection means;
Third storage means for storing a position of a defective pixel determined to be uncorrectable by the determination means by the correction method of the first defective pixel;
The image photographing device according to claim 2 , further comprising: Recursive filter means for realizing the second defective pixel correction method by performing recursive filter processing on the current frame image,
The image photographing apparatus according to claim 3 , wherein the correction unit corrects data of a defective pixel at a position stored in the third storage unit using the recursive filter unit . The recursive filter means includes:
Motion detection means for detecting motion of the current frame image relative to the previous frame image;
Spatial filter means for performing spatial filter processing on the current frame image;
A frame memory for storing data of the previous frame image;
A calculation means for performing a recursive filter calculation by inputting a current frame image and a current frame image subjected to the spatial filter processing by the spatial filter means or a previous frame image read from the frame memory;
And switching means for switching to either one of said frame memory and said spatial filter means as an input to said computing means,
Including
At the position where front Symbol motion detection means detects motion switched to the spatial filter means, at a position where the motion detecting means does not detect motion Rutotomoni switched to the frame memory, stored in the third memory means 5. The image according to claim 4, wherein the data of a defective pixel which is determined to be uncorrectable by the determination unit by the correction method of the first defective pixel is corrected by switching to the frame memory at a predetermined position. Shooting device. The calculating means includes
a is the recursive filter coefficient, Pi _n (x, y) is the pixel data at the position x, y of the current frame image, Po _n-1 (x, y) is the position x, y input via the switching means Pixel data, Po _n (x, y) is the recursive filter output data of the pixel at position x, y in the current frame image,
Po _n (x, y) = (1-a) ・ Pi _n (x, y) + a ・ Po _n-1 (x, y)
Is to calculate
Position no motion is detected by said motion detection means, and the third in the stored position in a storage unit, an image according to claim 5, wherein the benzalkonium be between 1 recursive filter coefficients a Shooting device. A method for controlling an image capturing device,
A receiving step in which the receiving means receives data of each pixel read from the flat detector;
A detecting step for detecting a transfer error of the received data;
The correcting means is based on a predetermined peripheral pixel of the defective pixel in accordance with the relationship between the position of the pixel where the transfer error is detected in the detection step and the position of the defective pixel stored in advance in the first storage means. A correction step of selecting the first defective pixel correction method or the second defective pixel correction method using the current frame data and the previous frame data, and correcting the defective pixel data;
A control method for an image capturing apparatus, comprising: The program for functioning a computer as each means which the image imaging device of any one of Claims 1 thru | or 6 has.

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