A method for determining the focal spot half-energy width for X-ray focusing mirror

Abstract

The present invention relates to an X-ray focusing mirror, and in particular to a method for determining the half-energy width of a focal spot of an X-ray focusing mirror, which solves the technical problem of low precision of the existing method for determining the half-energy width of a focal spot. The present invention proposes a single-ring energy encirclement function, which measures and records the total number of photons within a single ring encirclement formed by concentric circles of different sizes that are divided from the focal spot center point to the edge of the detector format, and draws a single-ring energy encirclement function curve, which complements the standard energy encirclement function, and can accurately determine the boundary position of the focal spot of the X-ray focusing mirror, thereby determining the 100% energy range of the focal spot of the X-ray focusing mirror, and determining the 50% energy range of the focal spot of the X-ray focusing mirror through the energy encirclement function curve, and then determining the half-energy width.

Description

Technical Field

[0001] The invention relates to a calibration method for an X-ray focusing mirror, and in particular to a method for determining a focal spot half energy width of an X-ray focusing mirror. Background Art

[0002] An X-ray focusing mirror is an optical device that focuses and detects X-ray photons based on the principle of grazing incidence of X-rays and uses a multi-layer nested structure. Its key technical indicators include aperture, focal length, effective area and angular resolution.

[0003] In recent years, the development trend of X-ray focusing mirrors shows that ultra-large effective area and ultra-high angular resolution have become the main development goals of the next generation of X-ray focusing mirrors. As a result, higher requirements are put forward for the hardware calibration facilities and software calculation methods of X-ray focusing mirrors.

[0004] In the process of testing and calibrating the angular resolution of an X-ray focusing mirror, it is generally necessary to accurately calibrate the focal spot half-energy width of the X-ray focusing mirror through the energy enclosing function, and solve the numerical relationship between the angular resolution and the half-energy width to obtain a high-precision angular resolution. However, the smaller focal spot size will be affected by the background noise of the larger-format detector during the calculation of the angular resolution, resulting in lower calculation accuracy. The main reason is that due to the existence of background noise, the full-size focal spot range cannot be accurately determined, and thus the half-energy width of the focal spot cannot be accurately determined, which affects the calculation accuracy of the angular resolution. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem of low precision of the existing method for determining the half-energy width of a focal spot, and to provide a method for determining the half-energy width of a focal spot for an X-ray focusing mirror.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for determining the focal spot half energy width of an X-ray focusing mirror is characterized in that it comprises the following steps:

[0008] Step 1, measuring the focal spot of the X-ray focusing mirror, determining the focal position of the X-ray focusing mirror, and obtaining the focal spot image of the X-ray focusing mirror at the focal position of the X-ray focusing mirror;

[0009] Step 2, measuring the grayscale value of the X-ray focusing mirror focal spot or the number of deposited photons in a pixel, and determining the center point of the X-ray focusing mirror focal spot image based on the grayscale value of the X-ray focusing mirror focal spot or the number of deposited photons in a pixel;

[0010] Step 3: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, the total number of photons within the concentric circles of different radii is measured and recorded, and a statistical graph of the total number of photons within the concentric circles as the concentric circles vary with the concentric circles is drawn to obtain an energy encirclement function curve from the center of the focal spot to the edge of the detector;

[0011] Step 4: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, and the total number of photons in a single circular ring surrounded by two adjacent concentric circles is measured and recorded, and a statistical graph of the total number of photons in the single circular ring surrounded by a single circular ring as the single circular ring surrounded by the single circular ring changes is drawn to obtain a single circular ring energy surrounding function curve from the center of the focal spot to the edge of the detector;

[0012] Step 5, determining the energy range of 100% of the X-ray focusing mirror focal spot according to the inflection point of the single-ring energy encirclement function curve;

[0013] Step 6: According to the 100% energy range of the X-ray focusing mirror focal spot determined in step 5, the 50% energy range of the X-ray focusing mirror focal spot is determined by the energy enclosing function curve obtained in step 3, and its diameter is the half energy width.

[0014] Furthermore, step 5 is specifically as follows:

[0015] When the inflection point of the single-ring energy enclosing function curve is unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range at the unique inflection point is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the concentric circles at the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot;

[0016] When the inflection point of the single-ring energy enclosing function curve is not unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range with the least total number of photons within the single-ring range is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the concentric circles of the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot.

[0017] Furthermore, in step 2, a non-counting detector is used to measure the grayscale value of the focal spot of the X-ray focusing mirror, or a counting detector is used to measure the number of deposited photons in a pixel.

[0018] Furthermore, in step 2, the center point of the X-ray focusing mirror focal spot image is determined based on the grayscale value of the X-ray focusing mirror focal spot or the number of deposited photons in a pixel as follows:

[0019] If the grayscale value of the X-ray focusing mirror focal spot is the largest or the pixel point with the largest number of deposited photons in the pixel is unique, then the coordinate point corresponding to the pixel point with the largest grayscale value of the X-ray focusing mirror focal spot or the largest number of deposited photons in the pixel is selected as the center point of the X-ray focusing mirror focal spot image;

[0020] If the pixel point with the largest grayscale value of the X-ray focusing mirror focal spot or the largest number of deposited photons in the pixel is not unique, then the coordinate point corresponding to the average value of the coordinates of the pixel points with the largest grayscale value of all X-ray focusing mirror focal spots or the largest number of deposited photons in the pixel is selected as the center point of the X-ray focusing mirror focal spot image.

[0021] Furthermore, in step 1, a visible light system or an X-ray system is used to measure the focal spot of the X-ray focusing mirror.

[0022] Furthermore, in step 4, the radii of the concentric circles from the center point to the edge of the X-ray detector format increase in an arithmetic progression.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention provides a method for determining the half-energy width of an X-ray focusing mirror focal spot, and proposes a single-ring energy enclosing function to provide a guiding standard for accurately determining the boundary of the X-ray focusing mirror focal spot. The single-ring energy enclosing function complements the standard energy enclosing function and can accurately determine the 100% energy position and 50% energy position of the X-ray focusing mirror spot, and then accurately determine the 100% energy range and 50% energy range of the X-ray focusing mirror focal spot, thereby accurately determining the angular resolution of the X-ray focusing mirror focal spot. Compared with the traditional direct background noise subtraction, it avoids the occurrence of background virtual subtraction or over-subtraction caused by inconsistent format noise of the X-ray detector, thereby improving the accuracy of the X-ray focusing mirror angular resolution calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the focal spot of the X-ray focusing mirror;

[0026] Figure 2 A schematic diagram of the energy width range of the focal spot energy enclosing function of the X-ray focusing mirror;

[0027] Figure 3 Schematic diagram of the energy width of a single circular ring energy enclosing function of a focal spot of an X-ray focusing mirror in an embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the energy encirclement function of the focal spot and the energy encirclement function of a single circular ring of an X-ray focusing mirror in an embodiment of the present invention;

[0029] The following are the descriptions of the reference numerals:

[0030] 21- half energy width range of the focal spot of the X-ray focusing mirror, 22- 100% energy width range of the focal spot of the X-ray focusing mirror, 23- the innermost circle in the single-ring energy encirclement function, 24- the third ring in the single-ring energy encirclement function, 25- the outermost ring in the single-ring energy encirclement function, 31- energy encirclement function curve, 32- single-ring energy encirclement function curve. DETAILED DESCRIPTION

[0031] The following is a detailed description of a method for determining the focal spot half energy width for an X-ray focusing mirror proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0032] In order to meet the requirements for the calculation accuracy of the angular resolution of the focusing mirror, the present invention proposes a single-ring energy enclosing function based on the energy enclosing function to supplement the energy enclosing function, so that the half-energy width range of the focal spot can be accurately determined, thereby further improving the calculation accuracy of the angular resolution of the focal spot of the X-ray focusing mirror.

[0033] The present invention provides a method for determining the focal spot half energy width for an X-ray focusing mirror, comprising the following steps:

[0034] Step 1: Measure the focal spot of the X-ray focusing mirror, determine the focal position of the X-ray focusing mirror, and obtain the following Figure 1 The focal spot image of the X-ray focusing mirror is shown.

[0035] Step 2: Use a non-counting detector to measure the grayscale value of the focal spot of the X-ray focusing mirror or use a counting detector to measure the number of deposited photons in the pixel. If the grayscale value of the focal spot of the X-ray focusing mirror is the largest or the pixel with the largest number of deposited photons in the pixel is unique, then select the coordinate point corresponding to the pixel with the largest grayscale value of the focal spot of the X-ray focusing mirror or the pixel with the largest number of deposited photons in the pixel as the center point of the X-ray focusing mirror focal spot image; if there is no less than one pixel with the largest grayscale value of the focal spot of the X-ray focusing mirror or the pixel with the largest number of deposited photons in the pixel, then select the coordinate point corresponding to the average value of the coordinates of all the pixel points with the largest grayscale value of the focal spot of the X-ray focusing mirror or the pixel with the largest number of deposited photons in the pixel as the center point of the X-ray focusing mirror focal spot image.

[0036] Step 3: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, the total number of photons within the concentric circles of different radii is measured and recorded, and a statistical graph of the total number of photons within the concentric circle encirclement as the concentric circle encirclement range changes is drawn, that is, an energy encirclement function curve from the center of the focal spot to the edge of the detector.

[0037] like Figure 2 As shown in FIG. 1 , it is a schematic diagram of the energy width range of the energy enclosing function. In the figure, the diameter of the half-energy width range 21 of the X-ray focusing mirror is the half-energy width; the diameter of the 100% energy width range 22 of the X-ray focusing mirror is the full size of the focusing mirror spot. The energy enclosing function curve is drawn as shown in FIG. Figure 4 As shown in curve 31 in , the horizontal axis is the concentric circle encirclement range, and the vertical axis is the total number of photons within the encirclement range. As the concentric circle encirclement range increases, the total number of photons within the concentric circle encirclement range also increases accordingly, so the energy encirclement function curve presents a monotonically increasing trend.

[0038] Step 4: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, and the radius of the concentric circles increases in an arithmetic progression. The total number of photons within the encirclement of a single circle is measured and recorded, and a statistical graph of the total number of photons within the encirclement of a single circle as it changes with the encirclement of a single circle is drawn, that is, a single circle energy encirclement function curve from the center of the focal spot to the edge of the detector.

[0039] In this embodiment, the radii of the concentric circles of different sizes increase in an arithmetic progression. In other embodiments, the radii of the concentric circles of different sizes may be selected using other rules or without rules.

[0040] like Figure 3 As shown in the figure, it is a schematic diagram of the energy width of the single-ring energy encirclement function of the focal spot of the X-ray focusing mirror. In the figure, the number of photons enclosed within the encirclement of the innermost circle 23 in the single-ring energy encirclement function is the number of photons in the first ring; the number of photons enclosed within the encirclement of the third ring 24 in the single-ring energy encirclement function is the number of photons in the third ring; the number of photons enclosed within the encirclement of the outermost ring 25 in the single-ring energy encirclement function is the number of photons in the outermost ring. The drawn single-ring energy encirclement function curve is shown in Figure 4 As shown in curve 32, the horizontal axis is the single-circle enclosing range, and the vertical axis is the number of photons within the single-circle enclosing range. The single-circle energy enclosing function will show an increasing trend both within and outside the focal spot of the X-ray focusing mirror due to the increase of the enclosing area, and will show a decreasing trend at the focal spot boundary of the X-ray focusing mirror due to the significant reduction of the photon density. Therefore, the single-circle energy enclosing function curve will have a relatively obvious inflection point at the edge of the focal spot.

[0041] Step 5: determine the 100% energy range of the X-ray focusing mirror focal spot according to the inflection point of the single-ring energy enclosing function curve; the position of the single-ring outer circle corresponding to the single-ring enclosing range at the inflection point of the single-ring energy enclosing function curve is the boundary position of the X-ray focusing mirror focal spot; and the enclosing range of the boundary position of the X-ray focusing mirror focal spot is the 100% energy range of the X-ray focusing mirror focal spot.

[0042] When the inflection point of the single-ring energy enclosing function curve is unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range at the unique inflection point is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the concentric circles at the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot; when the inflection point of the single-ring energy enclosing function curve is not unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range with the least total number of photons within the single-ring range is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot.

[0043] like Figure 4 As shown in curve 32, there are two inflection points on the single-ring energy enclosing function curve. At the first inflection point, the total number of photons within the single-ring enclosing range is the least. Therefore, the position of the single-ring outer circle corresponding to the single-ring enclosing range is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot.

[0044] Step 6: According to the 100% energy range of the X-ray focusing mirror focal spot determined in step 5 and the energy enclosing function curve obtained in step 3, determine the 50% energy range of the X-ray focusing mirror focal spot, whose diameter is the half energy width.

[0045] According to the obtained half-energy width, combined with the numerical relationship between the half-energy width and the angular resolution, the precise value of the angular resolution of the X-ray focusing mirror is calculated, and the production and manufacturing process of the X-ray focusing mirror is guided.

[0046] The method for accurately determining the half-energy width of the X-ray focusing mirror focal spot of the present invention proposes a single-ring energy enclosing function, which provides a guiding standard for accurately determining the boundary of the X-ray focusing mirror focal spot. The single-ring energy enclosing function and the standard energy enclosing function algorithm complement each other and can accurately determine the 100% energy position and 50% energy position of the X-ray focusing mirror spot, and then accurately determine the 100% energy range and 50% energy range of the X-ray focusing mirror focal spot, thereby accurately determining the angular resolution of the X-ray focusing mirror focal spot.

Claims

1. A method for determining the focal spot half-energy width of an X-ray focusing mirror, characterized in that: The following steps are involved: Step 1, measuring the focal spot of the X-ray focusing mirror, determining the focal position of the X-ray focusing mirror, and obtaining the focal spot image of the X-ray focusing mirror at the focal position of the X-ray focusing mirror; Step 2, measuring the grayscale value of the X-ray focusing mirror focal spot or the number of deposited photons in a pixel, and determining the center point of the X-ray focusing mirror focal spot image based on the grayscale value of the X-ray focusing mirror focal spot or the number of deposited photons in a pixel; Step 3: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, the total number of photons within the concentric circles of different radii is measured and recorded, and a statistical graph of the total number of photons within the concentric circles as the concentric circles vary with the concentric circles is drawn to obtain an energy encirclement function curve from the center of the focal spot to the edge of the detector; Step 4: Based on the center point of the X-ray focusing mirror focal spot image determined in step 2, the focal spot image is divided into concentric circles of different radii from the center point to the edge of the X-ray detector format, and the total number of photons in a single circular ring surrounded by two adjacent concentric circles is measured and recorded, and a statistical graph of the total number of photons in the single circular ring surrounded by a single circular ring as the single circular ring surrounded by the single circular ring changes is drawn to obtain a single circular ring energy surrounding function curve from the center of the focal spot to the edge of the detector; Step 5, determining the energy range of 100% of the X-ray focusing mirror focal spot according to the inflection point of the single-ring energy encirclement function curve; Step 6: According to the 100% energy range of the X-ray focusing mirror focal spot determined in step 5, the 50% energy range of the X-ray focusing mirror focal spot is determined by the energy enclosing function curve obtained in step 3, and its diameter is the half energy width.

2. The method for determining the focal spot half energy width of an X-ray focusing mirror according to claim 1, characterized in that: Step 5 is as follows: When the inflection point of the single-ring energy enclosing function curve is unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range at the unique inflection point is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the concentric circles at the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot; When the inflection point of the single-ring energy enclosing function curve is not unique, the position of the single-ring outer circle corresponding to the single-ring enclosing range with the least total number of photons within the single-ring range is the boundary position of the X-ray focusing mirror focal spot, and the enclosing range of the concentric circles of the boundary position of the X-ray focusing mirror focal spot is 100% of the energy range of the X-ray focusing mirror focal spot.

3. The method for determining the focal spot half energy width of an X-ray focusing mirror according to claim 2, characterized in that: In step 2, a non-counting detector is used to measure the grayscale value of the focal spot of the X-ray focusing mirror, or a counting detector is used to measure the number of deposited photons in a pixel.

4. The method for determining the focal spot half energy width of an X-ray focusing mirror according to claim 3, characterized in that: In step 2, the center point of the X-ray focusing mirror focal spot image is determined based on the gray value of the X-ray focusing mirror focal spot or the number of deposited photons in the pixel as follows: If the grayscale value of the X-ray focusing mirror focal spot is the largest or the pixel point with the largest number of deposited photons in the pixel is unique, then the coordinate point corresponding to the pixel point with the largest grayscale value of the X-ray focusing mirror focal spot or the largest number of deposited photons in the pixel is selected as the center point of the X-ray focusing mirror focal spot image; If there is at least one pixel point with the largest grayscale value of the X-ray focusing mirror focal spot or the largest number of deposited photons in the pixel, the coordinate point corresponding to the average value of the coordinates of the pixel points with the largest grayscale value of the X-ray focusing mirror focal spot or the largest number of deposited photons in the pixel is selected as the center point of the X-ray focusing mirror focal spot image.

5. The method for determining the focal spot half energy width of an X-ray focusing mirror according to claim 4, characterized in that: In the step 1, a visible light system or an X-ray system is used to measure the focal spot of the X-ray focusing mirror.

6. The method for determining the focal spot half-energy width for an X-ray focusing mirror according to any one of claims 1 to 5, characterized in that: In step 4, the radii of the concentric circles from the center point to the edge of the X-ray detector format increase in an arithmetic progression.

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