A resolution plate, a resolution test system and a method of measuring resolution capability

Abstract

The application discloses a resolution plate, a resolution test system and a method for measuring resolution capability, wherein the resolution plate comprises a plate body, at least one slit group is arranged on the plate body, the slit group comprises two parallel slits which are arranged on the plate body along a path, the slit has a width in a direction perpendicular to the path, the slit has a uniform width along the path, the two slits have a consistent shape and width, the two slits are arranged at intervals, and the interval of the two slits is equal to the width of the slit. By arranging at least one slit group with two slits on the plate body made of tungsten material, high-energy X rays can form at least one image with two strips on the imaging plate through the slit group, and the corresponding curve can be obtained through simple measurement and multiple tests, so that the resolution capability of the ray point source under the corresponding magnification ratio and the slit width can be intuitively and accurately reflected.

Description

Technical Field

[0001] This invention relates to the field of resolution testing technology, and in particular to a resolution board, a resolution testing system, and a method for measuring resolution. Background Technology

[0002] Currently, there are generally two methods for measuring the resolution of high-energy X-ray point sources. One method is to obtain the line spread function (LSF) through single-slit imaging, and then obtain the optical modulation transfer function (MTF) through one-dimensional Fourier transform. The vertical axis represents the modulation degree, and the horizontal axis represents the spatial frequency, i.e., the resolution. It is generally believed that the spatial frequency corresponding to a modulation degree of 0.05 is the limiting resolution. The other method is to obtain an edge-blurred image through a cylindrical tungsten step, which is the edge spread function (ESF). The LSF is obtained through differentiation, and the subsequent steps are the same as the first method.

[0003] In fact, although the two measurement methods mentioned above are quite different, their ultimate goal is to measure the resolving power of a point source in imaging an object. When using the single slit or cylindrical step method to measure resolution, there is a drawback that the calculation data is relatively cumbersome. Moreover, when using the first method to measure resolution, in most cases, the standard distribution function form cannot be obtained, but it is simplified into these distribution functions to calculate MTF, which will cause errors in resolution measurement. Summary of the Invention

[0004] The purpose of this invention is to provide a resolution board, a resolution testing system, and a method for measuring resolution capability, so as to overcome the shortcomings of existing methods that involve cumbersome calculations and result in resolution measurement errors.

[0005] A resolution board, the resolution board comprising:

[0006] A plate body, wherein at least one set of slits is provided on the plate body, the slits comprising two parallel slits that pass through the plate body along a path, the slits having a width in a direction perpendicular to their opening path, the slits being of equal width along their opening path, the two slits having the same shape and width, the two slits being spaced apart, and the distance between the two slits being equal to the width of the slits.

[0007] In some embodiments of the resolution panel, the panel body is provided with four sets of slit groups, each slit group including two slits, and the width of the slits corresponding to the four sets of slit groups increases sequentially from low to high.

[0008] In some embodiments of the resolution panel, the four sets of slits are arranged on the panel in order of increasing or decreasing width of the corresponding slits.

[0009] In some embodiments of the resolution panel, the slit includes two symmetrically arranged sub-slits. The sub-slits are opened on the panel along a semi-circular trajectory, with the first end of one end serving as the first end. The first ends of the two sub-slits and the other end are respectively opposite to each other and spaced apart.

[0010] In some embodiments of the resolution panel, the slits corresponding to the four sets of slit groups are arranged concentrically on the panel body.

[0011] In some embodiments of the resolution panel, a set of straight slits, including two straight slits, is further provided on the panel inside the slit with the smallest radius. The width of the straight slits is the same as the width of the slit with the smallest radius.

[0012] In some embodiments of the resolution panel, the widths of the four sets of slits are 0.2 mm, 0.25 mm, 0.3 mm, and 0.5 mm, respectively, from smallest to largest.

[0013] On the other hand, embodiments of the present invention provide a resolution testing system, comprising:

[0014] Imaging plate, made of scintillator; and

[0015] The resolution board described above.

[0016] This invention also provides a method for measuring resolution capability using the resolution testing system described above, comprising the following steps:

[0017] The resolution plate is placed between the ray point source and the imaging plate. The distance between the resolution plate and the ray point source is set to x1, and the distance between the resolution plate and the imaging plate is set to x2, so that the magnification ratio M = (x1 + x2) / x1 is obtained.

[0018] A point source of X-rays is directed toward the resolution plate to irradiate high-energy X-rays to form at least one set of images on the imaging plate, the set of images comprising two stripes of equal width with grayscale.

[0019] The light intensity ratio f1 / f2 is calculated by measuring the gray value f2 at the center position of the two strips in the same image group and the gray value f1 at the center position of the region between the two strips.

[0020] The width of the slit is set to d, and a curve is plotted based on the relationship between the light intensity ratio, the width of the slit, and the magnification ratio.

[0021] In some embodiments of the method for measuring resolution, the step of setting the slit width to d and plotting a curve based on the relationship between the light intensity ratio, the slit width, and the magnification ratio includes:

[0022] The product of the slit width and the magnification ratio, d*(M / M-1), is obtained. The value of the product is used as the abscissa, and the value of the light intensity ratio corresponding to the value of the product is used as the ordinate to obtain a coordinate point on a two-dimensional coordinate system.

[0023] By changing the magnification ratio, multiple coordinate points are obtained on a two-dimensional coordinate system, and the multiple coordinate points are connected in sequence to form the curve.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] This invention provides a resolution plate, a resolution testing system, and a method for measuring resolution capability. At least one set of slits with two slits is set on a plate made of tungsten material. High-energy X-rays passing through the slits form at least one image with two stripes on the imaging plate. The intensity ratio is determined by the ratio of the gray value at the center of the region between the two stripes to the gray value at the center of the strip. The magnification ratio can be obtained from the distance between the X-ray source and the plate, and the distance between the plate and the imaging plate. With a fixed slit width, the intensity ratio changes by changing the magnification ratio. Using the product of the magnification ratio and the slit width as the abscissa and the intensity ratio as the ordinate, corresponding points are formed in a two-dimensional coordinate system. By repeatedly changing the magnification ratio, a series of coordinate points can be obtained in the coordinate system. Connecting each coordinate point sequentially with a curve yields a resolution curve. Therefore, without cumbersome calculations, the corresponding curve can be obtained through simple measurements and multiple experiments. The operation is simple and can intuitively and accurately reflect the resolution capability of the X-ray source at corresponding magnification ratios and slit widths. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a resolution testing system provided in an embodiment of the present invention.

[0027] Figure 2 A flowchart of a method for measuring resolution provided in an embodiment of the present invention.

[0028] In the diagram, 1 is the plate; 11 is the slit group; 111 is the slit; 12 is the linear slit group; 121 is the linear slit; and 2 is the imaging plate. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] like Figure 1 As shown, this invention discloses a resolution testing system capable of measuring the resolution of high-energy X-rays. The system includes an imaging plate 2 and a resolution plate. The resolution plate transmits high-energy X-rays, and the imaging plate 2 is used for imaging high-energy X-rays transmitted through the resolution plate. It should be noted that to clearly display high-energy X-rays on the imaging plate 2, the high-energy X-rays irradiating the imaging plate 2 need to be converted into visible light. In this embodiment, the imaging plate 2 is made of an LSO scintillator based on the fluorescence diffusion effect. The conversion principle of this scintillator is that when high-energy X-rays pass through the resolution plate and irradiate the imaging plate 2, the stronger the intensity of the irradiated rays, the darker the color displayed on the imaging plate 2; the weaker the intensity of the rays, the whiter the color displayed on the imaging plate 2. This principle allows the determination of the ray intensity on the imaging plate 2. It is worth mentioning that the grayscale value of the image formed by high-energy X-ray irradiation from the imaging plate 2 can be read using existing computer software. A higher grayscale value indicates a higher irradiation intensity, and vice versa.

[0032] The resolution plate includes a plate body 1, which can be made of tungsten. Tungsten not only effectively blocks high-energy X-rays, but its shielding performance against high-energy X-rays is also better than that of plates made of lead or iron. Tungsten is also reasonably priced, so manufacturing costs are not a concern. At least one set of slits 11 is provided on the plate body 1. Each slit set 11 includes two parallel slits 111 that run along a path through the plate body 1. High-energy X-rays irradiate the imaging plate 2 through the slits 111. Each slit 111 has a predetermined width perpendicular to its path. The widths of the slits 111 are equal along the path, and the two slits 111 have the same shape and width. The two slits 111 are spaced apart, and the distance between the two slits 111 is equal to the width of the slit 111.

[0033] By setting at least one set of slits 11 on the plate 1, with each slit 11 having two slits 111, during imaging, the resolution plate is placed between the high-energy X-ray source and the imaging plate 2. The source illuminates the plate 1, and the high-energy X-rays can pass through the slits 111 on the plate 1 to form two grayscale stripes on the imaging plate 2. Existing software can measure the grayscale value at the middle position of the stripes; this grayscale value is the maximum grayscale value of the entire strip and is therefore defined as the strongest grayscale value f2. Existing software can also measure the grayscale value at the middle position of the region between the two stripes; this grayscale value is defined as the minimum grayscale value f1. Whether the stripes formed on the imaging plate 2 by the X-ray point source passing through the slits 111 on the plate 1 can be clearly distinguished, and the degree of clarity of the distinction, i.e., the resolution energy, essentially depends on the ratio between the minimum grayscale value and the strongest grayscale value, also known as the light intensity ratio f1 / f2. Define the distance between the ray point source and plate 1 as x1, and the distance between plate 1 and imaging plate 2 as x2. Then the magnification ratio M = (x1 + x2) / x1 can be determined. It can be seen that any change in the parameters x1 and x2 can lead to a change in the magnification ratio. The change in magnification ratio and / or the change in the width of slit 111 can affect the magnitude of the light intensity ratio. Specifically, through multiple experiments, it was found that under the same ray point source irradiation, each product of magnification ratio and width corresponds to a light intensity ratio.

[0034] By setting at least one set of slits 11 with two slits 111 on a plate 1 made of tungsten material, high-energy X-rays can form at least one image with two stripes on an imaging plate 2 through the slits 111. The light intensity ratio is determined by the ratio of the gray value at the center of the region between the two stripes on the imaging plate 2 to the gray value at the center of the strip. When the width of the slits 111 is constant, the light intensity ratio changes by changing the distance between the X-ray source and the plate 1 and / or the distance between the plate 1 and the imaging plate 2, i.e., changing the magnification. The product of the magnification and the width of the slits 111 is used as the abscissa, and the light intensity ratio is used as the ordinate, so that corresponding points can be formed in a two-dimensional coordinate system. By changing the value of the magnification multiple times, a series of coordinate points can be obtained in the coordinate system. Connecting each coordinate point with a curve in sequence yields a resolution curve. It should be noted that the resolving power of the same X-ray source is constant, and the final corresponding curve remains unchanged regardless of whether the width of the slits 111 or the magnification is changed. With the above settings, without complicated calculation steps, the curve can be obtained through simple measurement and multiple experiments. The operation is simple and can intuitively and accurately reflect the resolution of the X-ray point source at a certain magnification ratio and slit width of 111.

[0035] In one specific embodiment, please refer to Figure 1 The plate 1 has multiple sets of slit groups 11, which can be two, three, or four groups, etc. In this embodiment of the invention, four sets of slit groups 11 are provided, and each slit group 11 includes two slits 111 with the same shape and width. It is worth mentioning that the width of the slits 111 corresponding to the four sets of slit groups 11 increases sequentially from low to high. In this embodiment of the invention, the width of the slits 111 from small to large is 0.2mm, 0.25mm, 0.3mm, and 0.5mm, respectively. According to the reciprocal relationship between spatial frequency and the width of the slits 111, the highest resolution that the slits 111 on the plate 1 can measure is 1 / 0.2 = 5lp / mm, which is sufficient for measuring the resolution of high-energy X-rays. If the width of the slits 111 is too small, it will not only be difficult to process and shape on the plate 1, but it will also be difficult to sample and measure the image formed on the imaging plate 2 by high-energy X-rays passing through the slits 111. If the width of slit 111 is too large, the clarity of the image formed by high-energy X-rays passing through slit 111 on the imaging plate 2 will be very low, affecting the acquisition of the strongest and weakest gray values. Therefore, in this application, the lower limit of the width of slit 111 is 0.2 mm and the upper limit is 0.5 mm.

[0036] By setting multiple sets of slits 11 on the plate 1, with each set having a different slit width, and given a fixed distance between the X-ray source and the plate 1, and a fixed distance between the plate 1 and the imaging plate 2, four different minimum and maximum grayscale values ​​can be obtained in a single experiment. This means four coordinate points can be obtained in one experiment. Compared to obtaining only one coordinate point at a time, this significantly reduces the number of experiments required to obtain the data needed for plotting the graph, making graph plotting faster and greatly reducing experimental time.

[0037] It should be noted that the slit 111 can have various shapes, such as straight lines or circles. Depending on the shape of the slit 111, the four sets of slits 11 can be arranged on the plate 1 in ascending or descending order of width. For example, in a specific embodiment, the shape of the slit is preferably circular, but the slit 111 cannot be a complete circle on the plate 1, as this would cause the portion of the plate 1 surrounded by the slit 111 to detach from the plate 1. Accordingly, the slit 111 is configured to include two symmetrically arranged sub-slits, each a semicircle of equal size. The sub-slits begin at one end of the plate 1 and extend along a semi-circular trajectory. The end of the sub-slit furthest from the beginning is the end. Two sub-slits of the same slit 111 are spaced apart on the plate 1, with their beginning and end points facing each other. This connects the two sub-slits through the plate 1. Simply put, a circular slit 111 is cut along a diameter, and the two cut parts are positioned a distance apart in a direction perpendicular to the cut diameter. It should be noted that the radii of the four sets of slits 111 increase sequentially, and all four sets are concentric on the plate 1. The slit 111 with the smallest radius is located at the center, and the other three slits 111 are nested around the central slit 111 in ascending order of radius. By setting the shape of the slit 111 to be circular, the high-energy X-rays irradiating the slit 111 have uniform radiation characteristics. That is, the gray values ​​of the image irradiated by the high-energy X-rays through the slit 111 onto the imaging plate 2 are uniformly distributed. Thus, the gray values ​​obtained at any position on the image on the imaging plate 2 are the same, thereby effectively avoiding sampling measurement errors caused by different gray values.

[0038] It is worth mentioning that a set of straight slits 12 is also provided inside the slit 111 with the smallest radius on the plate 1. The straight slits 12 include two parallel straight slits 121, and the width of the straight slits 121 is set to be the same as the width of the slit 111 with the smallest radius. When acquiring the gray values ​​of multiple images formed on the imaging plate 2, a small arc length needs to be measured on the circular image. The arc length acquired on each image is equal. This results in the curvature of the image formed through the slit 111 with the smallest radius being greater than that of the other sets of arc lengths when acquiring the same arc length. When measuring gray values, the curvature needs to be as small as possible. When the curvature is large, it is inconvenient to process, making it difficult to obtain the strongest and weakest gray values ​​of the strips formed on the imaging plate 2. However, the strips imaged on the imaging plate 2 through the straight slits have a larger curvature, making it easier to obtain gray values.

[0039] On the other hand, please refer to Figure 2 The present invention also provides a method for measuring resolution capability using the above-described resolution testing system, specifically including the following steps:

[0040] S100. Place the resolution plate between the ray point source and the imaging plate, set the distance between the resolution plate and the ray point source to x1, and set the distance between the resolution plate and the imaging plate to x2, so as to obtain the magnification ratio M = (x1 + x2) / x1.

[0041] S200. High-energy X-rays are irradiated from a point source toward a resolution plate to form at least one image group on the imaging plate, the image group comprising two stripes of equal width with grayscale.

[0042] S300. Measure the gray value f2 at the center position of two strips in the same image group and the gray value f1 at the center position of the region between the two strips, and calculate the light intensity ratio f1 / f2.

[0043] Whether the stripes formed by high-energy X-rays passing through the slit on the imaging plate can be clearly distinguished, and the degree of clarity of the distinction, essentially depends on the ratio of gray value f1 to gray value f2, which is called the light intensity ratio f1 / f2 in this embodiment. The magnitude of the light intensity ratio is related to the magnification ratio and the width of the slit. For example, with slits of the same width, when the imaging plate is attached to the side of the plate facing away from the X-ray source, that is, when x2 is 0, the magnification ratio M = 1. At this time, the gray value f2 reaches its maximum, while the gray value f1 reaches its minimum, resulting in the minimum light intensity ratio. As x2 gradually increases, the magnification ratio M also gradually increases. The slit gradually diffuses the light intensity distribution of high-energy X-rays towards both ends of the width direction. At this time, the light intensity at the center of the strip formed on the imaging plate through the slit becomes smaller and smaller, while the light intensity at the center between the two strips becomes larger and larger. This causes the value of f1 to gradually approach f2. When f1 = f2, the two strips on the imaging plate and the position between the strips can no longer be distinguished. This makes the high-energy X-rays passing through a set of slits form a whole strip on the imaging plate without any distinction between light and dark. At this time, the limit resolution of high-energy X-rays is reached.

[0044] Furthermore, when the magnification ratio is constant, changing the slit width can also alter the light intensity ratio. A wider slit makes resolution easier; conversely, a smaller light intensity ratio and a narrower slit result in the grayscale value f1 at the center of the two bands formed on the imaging plate through the slit approaching the grayscale value f2 at the center of the bands. This continues until the slit width decreases to a certain value where f1 = f2, at which point the limit of resolution is reached. Since the slit width is relatively small, repeatedly changing it is difficult. Therefore, the experiment used a method of changing the magnification ratio. By analyzing the corresponding data between the magnification ratio, slit width, and light intensity ratio at different magnification ratios, a curve reflecting the resolution can be plotted.

[0045] S400. Set the slit width to d, and plot a curve based on the relationship between the light intensity ratio, the slit width, and the magnification ratio.

[0046] Specifically, in one particular embodiment, step S400 includes:

[0047] S410. Derive the product formula d*(M / M-1) of the slit width and magnification ratio. Use the value of the product formula as the abscissa and the value of the light intensity ratio corresponding to the value of the product formula as the ordinate to obtain a coordinate point on the two-dimensional coordinate system.

[0048] S420. Change the magnification ratio to obtain multiple coordinate points on the two-dimensional coordinate system, and connect the multiple coordinate points in sequence to form a curve.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for measuring resolution capability using a resolution testing system, characterized in that, The resolution testing system includes: an imaging plate (2) made of a scintillator; and a resolution plate; The resolution panel includes: a panel body (1), on which at least one set of slits (11) is provided, the slits (11) including two parallel slits (111) that pass through the panel body along a path, the slits (111) having a width in a direction perpendicular to their opening path, the slits (111) being of equal width along their opening path, the two slits (111) having the same shape and width, the two slits (111) being spaced apart, and the distance between the two slits (111) being equal to the width of the slits (111); The method includes: The resolution plate is placed between the ray point source and the imaging plate. The distance between the resolution plate and the ray point source is set to x1, and the distance between the resolution plate and the imaging plate is set to x2, so that the magnification ratio M = (x1 + x2) / x1 is obtained. A point source of X-rays is directed toward the resolution plate to irradiate high-energy X-rays to form at least one set of images on the imaging plate, the set of images comprising two stripes of equal width with grayscale. The light intensity ratio f1 / f2 is calculated by measuring the gray value f2 at the center position of the two strips in the same image group and the gray value f1 at the center position of the region between the two strips. The width of the slit is set to d, and a curve is plotted based on the relationship between the light intensity ratio, the width of the slit, and the magnification ratio. The step of setting the width of the slit to d and plotting a curve based on the relationship between the light intensity ratio, the width of the slit, and the magnification ratio includes: The product of the slit width and the magnification ratio, d*(M / M-1), is obtained. The value of the product is used as the abscissa, and the value of the light intensity ratio corresponding to the value of the product is used as the ordinate to obtain a coordinate point on a two-dimensional coordinate system. By changing the magnification ratio, multiple coordinate points are obtained on a two-dimensional coordinate system, and the multiple coordinate points are connected in sequence to form the curve.

2. The method for measuring resolution capability using the resolution testing system according to claim 1, characterized in that, The plate (1) is provided with four sets of slit groups (11), each slit group (11) includes two slits (111), and the width of the slits (111) corresponding to the four sets of slit groups (11) increases sequentially from low to high.

3. The method for measuring resolution capability using the resolution testing system according to claim 2, characterized in that, The four groups of slits (11) are arranged on the plate (1) in order of increasing or decreasing width of the corresponding slits (111).

4. The method for measuring resolution capability using the resolution testing system according to claim 2, characterized in that, The slit (111) includes two symmetrically arranged sub-slits. The sub-slits are opened on the plate (1) along a semi-circular trajectory, with one end of the plate (1) serving as the starting end. The starting ends of the two sub-slits and the other end are respectively opposite to each other and spaced apart.

5. The method for measuring resolution capability using the resolution testing system according to claim 4, characterized in that, The four groups of slits (11) are arranged with the slits (111) at the same center on the plate (1).

6. The method for measuring resolution capability using the resolution testing system according to claim 5, characterized in that, On the plate (1), inside the slit (111) with the smallest radius, there is also a set of straight slits (12). The straight slits (12) include two straight slits (121). The width of the straight slits (121) is the same as the width of the slit (111) with the smallest radius.

7. The method for measuring resolution capability using the resolution testing system according to any one of claims 2-6, characterized in that, The widths of the four slits (111) are 0.2 mm, 0.25 mm, 0.3 mm and 0.5 mm, respectively, from smallest to largest.

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