JP2021056138A - Radiation imaging device, method for radiation imaging, and program - Google Patents

Abstract

To provide a method for precisely performing an offset correction by using output of a light-shielding pixel.SOLUTION: The radiation imaging device of the present invention includes: a detection unit having a first pixel 303 with a conversion element which converts an electromagnetic wave to an electric signal, a second pixel 304 with a conversion element shielded from light, and a third pixel 305 with an opening for receiving light narrowed for the first pixel; and a processing unit for correcting the output of the second pixel by a signal acquired on the basis of the output of the second pixel and the output of one of the first pixel and the third pixel, the processing unit correcting the output of the first pixel on the basis of the corrected output of the second pixel.SELECTED DRAWING: Figure 4

Description

The present invention relates to a radiation imaging device, a radiation imaging method and a program.

As a radiation imaging device used for medical image diagnosis and non-destructive inspection by radiation, a radiation imaging device using a matrix substrate having a pixel array combining a switch such as a TFT (thin film) and a conversion element such as a photoelectric conversion element has been put into practical use. Has been done.

In a photoelectric conversion device in which a plurality of photoelectric conversion elements are arranged, the value of the output (that is, offset output) when no irradiation is performed (zero irradiation) is set due to the difference in environment such as the temperature placed for each pixel. There is some variation.

In Patent Document 1, as a method of performing offset correction, in addition to a conversion element for acquiring a radiation signal for each pixel, a light-shielded light-shielding area for acquiring an offset signal is provided, and a light-shielding area within the effective pixel area is provided. It is disclosed that the electric charge is directly read from the light-shielding pixel of the above and the black level of the entire effective pixel is grasped.

Japanese Unexamined Patent Publication No. 2007-019820

However, the upper part of the light receiving light of the light-shielding pixel is shielded by a metal light-shielding film, and there may be a case where the light-receiving component cannot be completely shielded by a wraparound component due to oblique incident of radiation. If the light-shielding pixels are not completely shaded and a leaking electromagnetic wave is incident, the signal level in the light-shielding region fluctuates, so there is a problem that the offset value obtained from the signal in the light-shielding region and the actual offset fluctuation value occur. is there.

To solve this problem, a method of prohibiting the use of the output of the light-shielding pixel when a leaked electromagnetic wave is generated is assumed. When this method is used, in a situation where leakage electromagnetic waves are generated and the offset fluctuates due to temperature changes or the like, it is not possible to correct the offset fluctuation of the effective pixel. Therefore, the effective pixel output is black due to the decrease in the offset value. Crushing etc. will occur. Further, in radiography, the irradiation dose is generally managed by automatic brightness control (ABC: Auto Brightness Control). Since the automatic brightness control (ABC) manages the irradiation dose by referring to the average output of effective pixels, leakage electromagnetic waves (hereinafter, also referred to as “leakage light”) are generated, and the offset fluctuation of the effective pixel output due to temperature changes or the like occurs. If it does occur, it can cause problems such as the inability to properly control the actual dose.

In view of the above problems, the present invention provides a radiation imaging technique capable of accurately performing offset correction using the output of light-shielding pixels even when the offset fluctuates due to the generation of leaked light, temperature changes, and the like. The purpose is to provide.

The radiation imaging device according to one aspect of the present invention has a first pixel having a conversion element that converts an electromagnetic wave into an electric signal, a second pixel in which the conversion element is shielded from light, and an opening that receives light from the first pixel. A detection means having a narrowed third pixel, and
The processing means includes a processing means for correcting the output of the second pixel by a signal acquired based on the output of the second pixel and the output of the first pixel or the output of the third pixel. The output of the first pixel is corrected based on the corrected output of the second pixel.

In the radiation imaging method according to another aspect of the present invention, a first pixel having a conversion element that converts an electromagnetic wave into an electric signal, a second pixel in which the conversion element is shielded from light, and the first pixel receive light. It is a radiation imaging method in a radiation imaging device that captures a radiation image using a detection means having a third pixel with a narrowed opening.
A step of correcting the output of the second pixel by a signal acquired based on the output of the second pixel and the output of the first pixel or the output of the third pixel.
It is characterized by having a step of correcting the output of the first pixel based on the corrected output of the second pixel.

According to the present invention, it is possible to provide a radiation imaging technique capable of performing offset correction with high accuracy.

The figure which shows the whole structure example of the X-ray image pickup apparatus which concerns on Embodiment 1. FIG. The flowchart explaining the flow of processing from the start to the end of shooting of a subject using an X-ray imaging apparatus. The figure which showed the structural example of the X-ray detection part which concerns on Embodiment 1. FIG. An enlarged view of the area 306 of FIG. The flowchart explaining the flow of the leakage light correction and offset correction processing of an image processing unit. The figure which shows an example of the structure of the X-ray detection part which concerns on Embodiment 1. FIG. The figure which shows an example of the structure of the X-ray detection part which concerns on Embodiment 1. FIG. The figure which shows an example of the structure of the X-ray detection part which concerns on Embodiment 1. FIG. The figure which showed the effect of the leakage light correction when the irradiation dose was changed. The figure which showed the effect of the leakage light correction when the opening degree of a collimator was changed and the irradiation field was changed. The figure illustrating the statistical processing method of Embodiment 2 exemplarily.

Hereinafter, preferred embodiments to which the present invention is applied will be described in detail with reference to the accompanying drawings. In the embodiment of the present invention, radiation is not limited to generally used X-rays, but also other rays such as α-rays, β-rays, and γ-rays, which are beams produced by particles (including photons) emitted by radioactive decay. , Beams with similar or higher energies (eg particle rays, cosmic rays, etc.) are also included.

In the following description of each embodiment of the present invention, a case where the radiation imaging device according to the present invention is applied to an X-ray imaging device that captures X-ray image data of a subject using X-rays will be described. Further, in the present invention, the present invention is not limited to this X-ray imaging device, and can be applied to, for example, a radiation imaging device that captures a radiation image of a subject using radiation such as α rays.

(Embodiment 1)
The first embodiment of the present invention will be described. FIG. 1 is a diagram showing an overall configuration example of the X-ray imaging apparatus 10 according to the first embodiment. In FIG. 1, the X-ray irradiation unit 101 irradiates the subject P with X-rays. In the first embodiment, the subject P is a human body, and the X-ray imaging apparatus 10 can photograph, for example, the upper digestive tract of the subject P. The X-ray irradiation unit 101 includes an X-ray generation unit (tube or radiation tube) that generates X-rays, and a collimator that defines the spread angle of the generated X-ray beam and determines the irradiation field of the X-ray beam. Have.

The imaging control unit 104 controls the X-ray generation by the X-ray irradiation unit 101 based on the imaging conditions set by the imaging condition setting unit 103.

The X-ray detection unit 102 is an FPD (Flat Panel Detector), and has an arrangement structure in which a plurality of pixels are two-dimensionally arranged in an array. The X-ray detection unit 102 includes, as a plurality of pixels, an effective pixel (first pixel) having a conversion element that converts an electromagnetic wave into an electric signal, a light-shielding pixel (second pixel) in which the conversion element is shielded from light, and an effective pixel (effective pixel). It has an opening pixel (third pixel) in which the opening that receives light is narrowed with respect to the first pixel). Here, the aperture pixel (third pixel) is an image having the same or smaller sensitivity to electromagnetic waves than the effective pixel (first pixel). The output signal read from each pixel is amplified, converted into a digital signal, and then transmitted to the image processing unit 105.

The image processing unit 105 corrects the output signal (X-ray image data) of the first pixel based on the output signal of each pixel transmitted from the X-ray detection unit 102, and obtains the corrected X-ray image data. It is transmitted to the image display unit 106. The image display unit 106 outputs the X-ray image data transmitted from the image processing unit 105 to a display device such as a monitor.

FIG. 3 is a diagram showing a configuration example of the X-ray detection unit 102. The X-ray detection unit 102 has a plurality of pixels arranged in a pixel array 300 that constitutes a plurality of rows and a plurality of columns. The plurality of pixels are an effective pixel 303 (first pixel) for acquiring an X-ray image based on an electric signal corresponding to an X-ray, and a light-shielding pixel 304 (a light-shielding pixel 304 for acquiring an offset signal included in the X-ray image). A second pixel: also referred to as an optical black pixel 304) and an opening pixel 305 (third pixel) having a narrowed opening for receiving X-rays with respect to the effective pixel 303.

The outputs of the effective pixel 303 (first pixel), the light-shielding pixel 304 (second pixel), and the aperture pixel 305 (third pixel) are read out by the reading unit 301 for each row selected by the row selection unit 302. Each pixel signal is amplified by the signal amplification unit 301-1 of the reading unit 301, and the A / D converter 301-2 (signal conversion circuit) converts the analog signal amplified by the signal amplification unit 301-1 into a digital signal. And output to the image processing unit 105.

The effective pixel 303 and the aperture pixel 305 may be composed of a scintillator that converts X-rays into electromagnetic waves (visible light) and a photoelectric conversion element that converts electromagnetic waves (visible light) into electrical signals. The scintillator is generally arranged in a sheet shape so as to cover the pixel array 300, and can be shared by a plurality of pixels. Alternatively, the effective pixel 303 and the aperture pixel 305 may be composed of a conversion element that directly converts X-rays into an electric signal.

(Flow of shooting process)
FIG. 2 is a flowchart illustrating a processing flow from the start to the end of photographing a subject using the X-ray imaging apparatus 10.

In S201, the operator inputs imaging condition information such as tube voltage, tube current, and irradiation time by the imaging condition input unit provided in the imaging condition setting unit 103. The input shooting condition information is transmitted to the shooting control unit 104.

In S202, the imaging control unit 104 controls the X-ray irradiation unit 101 based on the received imaging condition information, and irradiates the subject P with X-rays.

In S203, the reading unit 301 reads a signal from the effective pixel 303, the light-shielding pixel 304, and the opening pixel 305, and converts the analog signal amplified by the signal amplification unit 301-1 into a digital signal by the A / D converter 301-2. It is converted and output to the image processing unit 105.

In S204, the image processing unit 105 corrects the leaked light signal included in the output of the light-shielding pixel 304. The image processing unit 105 can correct the leaked light signal by using the output of the effective pixel 303 or the output of the aperture pixel 305.

The image processing unit 105 determines whether the output of the effective pixel 303 (output of the first pixel) is saturated, and when the output of the effective pixel 303 (output of the first pixel) is saturated, the light-shielding pixel 304 (the output of the first pixel) The output of the light-shielding pixel 304 (second pixel) is corrected by the signal (signal Ln of the leakage light component) acquired based on the output of the second pixel) and the output of the opening pixel 305 (third pixel). Further, when the output of the effective pixel 303 (output of the first pixel) is not saturated, the image processing unit 105 receives the output of the light-shielding pixel 304 (second pixel) and the output of the effective pixel 303 (output of the first pixel). The output of the light-shielding pixel 304 (second pixel) is corrected by the signal (signal Ln of the leakage light component) acquired based on the output. That is, the image processing unit 105 corrects the output of the light-shielding pixel 304 by subtracting the signal of the leaked light component from the output of the light-shielding pixel 304 (second pixel). Then, the image processing unit 105 corrects the output of the effective pixel 303 by using the output of the light-shielding pixel 304 after correcting the leaked light signal (the output of the light-shielding pixel after correction). After the correction processing is completed, the image processing unit 105 outputs the output of the effective pixel 303 to the image display unit 106.

In S205, the image display unit 106 outputs the output of the effective pixels 303 received from the image processing unit 105 to a display device such as a monitor.

(Correction of leaked light signal)
Next, the details of the signal correction processing of the leaked light component described in S204 will be described with reference to FIG. 4, which is an enlarged view of the region 306 of FIG. Considering the case where the X-ray irradiation region is the region 401, the X-rays incident on the region of the light-shielding pixel 304 and its vicinity are converted into light by the scintillator. The converted light cannot be completely shielded by the light-shielding portion of the light-shielding pixel 304, and when the wraparound component due to oblique incidence enters the light-shielding pixel 304 as leaked light, the output of the light-shielding pixel 304 is increased. On the other hand, the effective pixel 303 and the aperture pixel 305 arranged in the vicinity of the light-shielding pixel 304 can detect the X-rays incident on the light-shielding pixel 304 according to the aperture ratio A. Here, the ratio of the leaked light to the components incident from the opening of the aperture pixel 305 is indicated by α as the leak light rate, and the output an of the light-shielding pixel 304 and the output bn of the aperture pixel 305 or the output cn of the effective pixel 303. And, the signal (leakage light amount) Ln of the leakage light component of the light-shielding pixel 304 can be calculated by the following equations (1) and (2).

Ln = (an−bn) × A / 100 × α / 100 ・ ・ ・ (1)
Ln = (an-cn) x A / 100 x α / 100 ... (2)
The image processing unit 105 corrects the output an of the light-shielding pixel 304 based on the calculated signal (leakage light amount) Ln of the leakage light component. Here, since the output signal of the light-shielding pixel 304 is the sum of the signal of the leakage light component (leakage light amount) and the offset signal, the image processing unit 105 receives the signal of the leakage light component (leakage) from the output signal of the light-shielding pixel 304. The output an of the light-shielding pixel 304 is corrected by subtracting the amount of light). That is, an offset signal (an-Ln) obtained by removing the signal of the leaked light component (leakage light amount) from the output an of the light-shielding pixel 304 is acquired. Then, the image processing unit 105 corrects the output of the entire surface of the effective pixel 303 by using the output (offset signal) of the corrected light-shielding pixel 304. That is, the image processing unit 105 performs the correction process by subtracting the output (offset signal) of the corrected light-shielding pixel 304 from the output cn of the effective pixel 303.

In addition to estimating the signal (leakage light amount) Ln of the leakage light component using the equations (1) and (2), the leakage light amount is acquired by performing a linear approximation to the outputs of the aperture pixels having a plurality of aperture ratios. Although it is possible, the calculation method using the above equation has a high calculation speed and is suitable for real-time image processing.

The aperture pixel 305 has a horizontally long rectangle in order to reduce the influence of the X-ray grid and estimate the amount of leaked light more accurately. In the example shown in FIG. 4, the opening width in the y direction (second direction) is formed wider than the opening width in the x direction (first direction).

A plurality of aperture pixels 305 are arranged in a small area in which a plurality of pixels are grouped together. The opening pixel 305 (third pixel) is arranged in the plane of the pixel array in the X-ray detection unit 102 at a position shifted in a direction (y direction) perpendicular to the grid direction (x direction) of the radiation grid. There is.

In the example shown in FIG. 4, three opening pixels 305 are arranged in the x direction (first direction), and six opening pixels 305 are arranged in the y direction (second direction). An arrangement example of 414 is shown. Similarly, in the light-shielding pixel 304, a 3 × 6 small area group in which three opening pixels 305 are arranged in the x direction (first direction) and six opening pixels 305 are arranged in the y direction (second direction). An arrangement example of 421 to 424 is shown.

The image processing unit 105 acquires the output of the aperture pixel 305 (third pixel) arranged in the vicinity region of the light-shielding pixel 304 (second pixel), and corrects the output of the light-shielding pixel 304 (second pixel). Is possible. By periodically arranging the aperture pixels 305 on a substantially straight line, it is not necessary to store the position information of all the aperture pixels in the storage area of the image processing unit 105, and the load on the image processing unit 105 is reduced. Will be possible. The image processing unit 105 acquires the output of the aperture pixel 305 (third pixel) periodically arranged on a substantially straight line, and corrects the output of the light-shielding pixel 304 (second pixel). Further, in consideration of the influence on the acquired X-ray image, the light-shielding pixel 304 (second pixel) and the opening pixel 305 (third pixel) are effective in which the effective pixel 303 (first pixel) is arranged two-dimensionally. It is arranged not inside the pixel area but in the peripheral area of the effective pixel area.

(Processing flow of image processing unit 105)
Next, the processing flow of the image processing unit 105 based on the above calculation method will be described with reference to FIG. Here, an example in which the median is used as an example of statistically processing the outputs from a plurality of pixels arranged in the small area group will be described, but in addition, an average value can also be used. FIG. 5 is a flowchart illustrating a flow of processing for leakage light correction and offset correction of the image processing unit 105 according to the first embodiment.

In the flowchart of FIG. 5, N indicates the total number of small area groups, and the image processing unit 105 executes the processing of S501 to S506 in each small area group for all the small area groups. The image processing unit 105 uses the statistical values acquired from the outputs of the plurality of light-shielding pixels 304 (second pixel) and the outputs of the plurality of effective pixels 303 (first pixel) in a small area in which a plurality of pixels are grouped together. The output of the second pixel is corrected by the signal (signal Ln of the leakage light component) acquired based on the acquired statistical value or the statistical value acquired from the output of the plurality of aperture pixels 305 (third pixel).

In S501, the image processing unit 105 calculates the median value an of the small region group (for example, 421 to 424 in FIG. 4) of the light-shielding pixel 304 as the output an of the light-shielding pixel 304.

Next, in S502, in order to perform leakage light correction on the output signal of the light-shielding pixel 304, the image processing unit 105 uses either the effective pixel 303 ((2) formula) or the aperture pixel 305 ((1) formula). Determine if to use. When the X-ray signal incident on the effective pixel 303 is very large, the output cn of the effective pixel 303 converted to a digital value by A / D conversion is the maximum value of the digital value that can be handled by the A / D converter 301-2. It may become saturated.

In such a case, the X dose incident on the light-shielding pixel 304 cannot be correctly estimated using the output cn of the effective pixel 303. Therefore, when the output of the effective pixel 303 is saturated (S502-Yes), in S503-1, the image processing unit 105 sets the output bn of the aperture pixel 305 in the equation (1) as the median value of the small region group. The bn is calculated, and if it is not saturated (S502-No), in S503-2, the image processing unit 105 calculates the median value cn of the small region group as the output cn of the effective pixel 303 in the equation (2). To do. Here, the image processing unit 105 can arbitrarily select a small area group for obtaining the median value of the effective pixel 303 within the effective pixel area in which the effective pixel 303 is two-dimensionally arranged.

In S504, the image processing unit 105 calculates the leakage light amount Ln using the equation (1) or (2). When the median value bn of the aperture pixel 305 was calculated in S503-1, the image processing unit 105 calculated the leakage light amount Ln based on the equation (1), and calculated the median value cn of the effective pixel 303 in S503-2. In this case, the image processing unit 105 calculates the leakage light amount Ln based on the equation (2).

In S505, the image processing unit 105 corrects the median value an of the small region group of the light-shielding pixel 304 by using the calculated leakage light amount Ln. The image processing unit 105 calculates the corrected median value an'by subtracting the signal of the leaked light component (leakage light amount Ln) from the median value an of the small region group of the light-shielding pixel 304 (an'= an-Ln). ).

In S506, the image processing unit 105 sequentially adds the corrected median value an'calculated for each small region group (for example, 421 to 424 in FIG. 4) (sum = sum + an').

The image processing unit 105 repeats the processes from S501 to S506 according to the number N of the small area group, and calculates the total value (sum) of the corrected median values an'.

In S507, the image processing unit 105 calculates the average value (Ave) of the median value an'based on the calculated total value (sum) and the number N of the small area group.

In S508, the image processing unit 105 corrects the entire output of the effective pixel 303 using the calculated average value (Ave). The image processing unit 105 performs correction processing by subtracting the average value (Ave) of the output of the corrected light-shielding pixel 304 from the output cn of the effective pixel 303.

In the processing flow of FIG. 5, the setting of the small area group regarding the effective pixel 303, the light-shielding pixel 304, and the aperture pixel 305 is arbitrary. Further, the statistical processing of the small region group in S501, S503-1, and S503-2 is not limited to the median calculation, and the statistical processing of S507 is not limited to the calculation of the average value.

The geometric arrangement of the light-shielding pixel 304 and the aperture pixel 305, the aperture ratio of the aperture pixel 305, and the shape of the aperture are not limited to the configuration shown in FIG. The aperture ratio of the aperture pixel 305 does not have to be constant in each aperture pixel 305, so that the plurality of aperture pixels 305 (third pixel) arranged in the X-ray detection unit 102 have a plurality of aperture ratios. It is also possible to configure.

Further, the arrangement of the opening pixels 305 may be such that the opening pixels 305 are periodically arranged in the oblique direction, for example, as shown in FIG. As shown in FIG. 6, a light-shielding pixel 304 (second pixel) and an aperture pixel 305 (third pixel) are arranged in a small area 601 composed of 3 × 6 pixels. In FIG. 6, the aperture pixels 305 are formed into a set of 6 pixels, and the set is periodically arranged in the oblique direction so that the aperture pixels 305 are periodically arranged in the oblique direction.

Further, as shown in FIG. 7, the opening pixels 305 may be arranged only on the left and right ends. In the pixel arrangement structure of the X-ray detection unit 102, the light-shielding pixels 304 (second pixels) are arranged at least on the outer edge of the arrangement structure.

Further, as shown in FIG. 8, the aperture ratio of the opening pixel 305 may be the same as that of the effective pixel 303. As shown in FIG. 8, a light-shielding pixel 304 (second pixel) is arranged in a small area 801 composed of 3 × 6 pixels, and an aperture pixel 305 (third pixel) is arranged in the vicinity of the small area 801. ..

Further, the arrangement of pixels in the X-ray detection unit 102 is not limited to the configuration shown in FIGS. 4, 6 to 8, and can be deformed within a range that does not deviate from the present invention.

FIG. 9 is a diagram showing the effect of light leakage correction when the X-ray irradiation dose is changed, and FIG. 10 is a diagram showing the effect of light leakage correction when the opening degree of the collimator is changed to change the irradiation field. It is a figure which showed.

As shown in FIG. 9, when the leakage light correction is not performed, the average output of the light-shielding pixel region shown by the solid line 901 also tends to increase as the X-ray dose applied to the light-shielded image region increases. On the other hand, when the leakage light correction is performed, the average output of the light-shielding pixel region shown by the broken line 902 tends to be constant even if the X-ray dose applied to the light-shielded image region increases.

Further, as shown in FIG. 10, when the leakage light correction is not performed, the average output of the light-shielding pixel region shown by the solid line 1001 also tends to increase as the opening degree of the collimator increases. On the other hand, when the leakage light correction is performed, the average output of the light-shielding pixel region shown by the broken line 1002 tends to be constant even if the opening degree of the collimator increases.

As a result, the offset correction of the output of the effective pixel can be stably performed regardless of the X-ray dose and the collimator opening degree, so that blackout of the effective pixel output occurs when the offset pixel value decreases due to a temperature change or the like. It becomes possible to suppress. In addition, it becomes possible to perform accurate dose control by ABC.

According to the first embodiment, in the radiation imaging apparatus, even when the offset fluctuates due to the generation of leaked light, a temperature change, or the like, the offset correction can be performed with high accuracy by using the output of the light-shielding pixel.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. The second embodiment is different from the first embodiment in the statistical processing when calculating the representative values of the aperture pixel and the light-shielding pixel in the leakage light correction. The image processing unit 105 has a frequency distribution of output values of a plurality of light-shielding pixels 304 (second pixel) and an output of a plurality of aperture pixels 305 (third pixel) for each small area in which a plurality of pixels are grouped together. Get the frequency distribution of values. Further, the image processing unit 105 acquires the output value of the first ratio from the lower rank in the frequency distribution of the output value of the light-shielding pixel 304 (second pixel) as a representative value of the output of the light-shielding pixel 304 (second pixel). The output value of the second highest ratio in the frequency distribution of the output value of the opening pixel 305 (third pixel) is acquired as a representative value of the output of the opening pixel 305 (third pixel).

Then, the image processing unit 105 obtains a signal (leakage light component signal Ln) based on the representative value of the output of the light-shielding pixel 304 (second pixel) and the representative value of the output of the opening pixel 305 (third pixel). ) Corrects the output of the light-shielding pixel 304 (second pixel).

In the following description, only the difference from the first embodiment will be described in order to avoid duplication of description. FIG. 11 is a diagram illustrating an exemplary method of statistical processing according to the second embodiment. In the second embodiment, as shown in FIG. 11, the image processing unit 105 acquires a frequency distribution with respect to the output value based on the output of the light-shielding pixel 304 and the output of the aperture pixel 305 for each small area. As shown in FIG. 11, the image processing unit 105 uses an output value corresponding to the first ratio (for example, the lower 30%) in the frequency distribution of the light-shielding pixels 304 as a representative value of the light-shielding pixels 304, and the opening pixel 305. The output value corresponding to the second ratio (for example, the top 15%) in the frequency distribution of is used as the representative value of the aperture pixel 305. The image processing unit 105 calculates the signal (leakage light amount) Ln of the leakage light component by performing the calculation of the equation (1) using the representative value of the aperture pixel 305 and the representative value of the light-shielding pixel 304. That is, the image processing unit 105 acquires an output value corresponding to the first ratio (for example, the lower 30%) in the frequency distribution of the light-shielding pixel 304 as the output an of the light-shielding pixel 304, and the second in the frequency distribution of the opening pixel 305. The output value corresponding to the ratio of 2 (for example, the top 15%) is acquired as the output bn of the opening pixel 305, and the leakage light amount Ln is calculated based on the calculation of the equation (1). The upper 15% and the lower 30% are exemplary ratios when calculating the representative values of the aperture pixel 305 and the light-shielding pixel 304, and the present invention is not limited to this example.

As a result, even if the arrangement of the opening pixels 305 and the light-shielding pixels 304 is random, it is not necessary to store the arrangements of the opening pixels 305 and the light-shielding pixels 304 in the image processing unit 105, and the image processing unit 105 It becomes possible to reduce the load.

According to the second embodiment, in the radiation imaging apparatus, even when the offset fluctuates due to the generation of leaked light, a temperature change, or the like, the offset correction can be performed with high accuracy by using the output of the light-shielding pixel.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

101: X-ray irradiation unit, 102: X-ray detection unit, 103: imaging condition setting unit,
104: Shooting control unit, 105: Image processing unit, 106: Image display unit,
300: Pixel array, 301: Read unit, 301-1: Signal amplification unit,
301-2: A / D converter, 302: row selection unit, 303: effective pixel,
304: Light-shielding pixel (optical black pixel), 305: Aperture pixel

Claims (16)

A detection means having a first pixel having a conversion element for converting an electromagnetic wave into an electric signal, a second pixel in which the conversion element is shielded from light, and a third pixel having a narrowed opening for receiving light from the first pixel. When,
A processing means for correcting the output of the second pixel by a signal acquired based on the output of the second pixel and the output of the first pixel or the output of the third pixel is provided.
The processing means is a radiation imaging apparatus characterized in that the output of the first pixel is corrected based on the corrected output of the second pixel. The radiation imaging apparatus according to claim 1, wherein the third pixel has the same or smaller sensitivity to the electromagnetic wave as compared with the first pixel. The radiation according to claim 1 or 2, wherein the processing means acquires the output of the third pixel arranged in the vicinity region of the second pixel and corrects the output of the second pixel. Imaging device. Any one of claims 1 to 3, wherein the processing means acquires the output of the third pixel, which is periodically arranged on a substantially straight line, and corrects the output of the second pixel. The radiation imaging apparatus according to. The detection means has an arrangement structure in which the first pixel, the second pixel, and the third pixel are arranged in an array.
The radiation imaging apparatus according to any one of claims 1 to 4, wherein the second pixel is arranged at least on the outer edge of the arrangement structure. According to any one of claims 1 to 5, the third pixel is arranged at a position shifted in a direction perpendicular to the grid direction of the radiation grid in the plane of the detection means. The radiation imaging apparatus described. The radiation imaging apparatus according to any one of claims 1 to 6, wherein the plurality of third pixels arranged in the detection means have a plurality of aperture ratios. The processing means has a statistical value acquired from the outputs of the plurality of second pixels, a statistical value acquired from the outputs of the plurality of first pixels, or a plurality of the above-mentioned statistical values in a small area in which a plurality of pixels are grouped together. The radiation imaging apparatus according to any one of claims 1 to 7, wherein the output of the second pixel is corrected by a statistical value acquired from the output of the third pixel and a signal acquired based on the statistical value. .. The radiation imaging apparatus according to claim 8, wherein the processing means acquires a median value or an average value as the statistical value and corrects the output of the second pixel. The processing means acquires the frequency distribution of the output values of the plurality of the second pixels and the frequency distribution of the output values of the plurality of the third pixels for each of the small regions.
The output value of the first ratio from the bottom in the frequency distribution of the output value of the second pixel is acquired as a representative value of the output of the second pixel.
The output value of the second highest ratio in the frequency distribution of the output value of the third pixel is acquired as a representative value of the output of the third pixel.
The radiation according to claim 8, wherein the output of the second pixel is corrected by a signal acquired based on the representative value of the output of the second pixel and the representative value of the output of the third pixel. Imaging device. The radiation imaging apparatus according to any one of claims 8 to 10, wherein the second pixel and the third pixel are arranged in the small area. The radiation imaging apparatus according to any one of claims 8 to 10, wherein the second pixel is arranged in the small area, and the third pixel is arranged in the vicinity of the small area. The processing means determines whether the output of the first pixel is saturated, and determines whether or not the output of the first pixel is saturated.
When the output of the first pixel is saturated, the output of the second pixel is corrected by the signal acquired based on the output of the second pixel and the output of the third pixel.
A claim characterized in that, when the output of the first pixel is not saturated, the output of the second pixel is corrected by a signal acquired based on the output of the second pixel and the output of the first pixel. Item 2. The radiation imaging apparatus according to any one of Items 1 to 12. The second pixel and the third pixel are according to any one of claims 1 to 13, wherein the first pixel is arranged in a peripheral region of a region in which the first pixel is two-dimensionally arranged. Radiation imaging device. A detection means having a first pixel having a conversion element for converting an electromagnetic wave into an electric signal, a second pixel in which the conversion element is shielded from light, and a third pixel having a narrowed opening for receiving light with respect to the first pixel. This is a radiation imaging method in a radiation imaging device that captures a radiation image using
A step of correcting the output of the second pixel by a signal acquired based on the output of the second pixel and the output of the first pixel or the output of the third pixel.
A step of correcting the output of the first pixel based on the corrected output of the second pixel, and
A radiation imaging method comprising. A program that causes a computer to execute each step of the radiation imaging method according to claim 15.

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