Coordinate calibration device and method based on distributed ray source imaging system

Abstract

The present disclosure provides a coordinate calibration device and method based on a distributed ray source imaging system. The coordinate calibration device comprises a ray source and a detector. The ray source is configured to emit X-rays. The detector comprises a detection part and a marking part. The detection part is configured to be disposed within a target area; the detection part and the ray source are respectively arranged on two sides of an object to be measured; and the detection part is configured to receive the X-rays. The marking part is located between the detection part and the ray source; and the relative position of the marking part and the detection part is fixed, wherein at least two marking points are spaced apart on the marking part, the at least two marking points are configured to perform coordinate calibration on X-ray imaging, and the coordinate calibration and the X-ray imaging are performed using the same data. The known parameters on the marking part are used to correct the relative coordinates between the ray source and the detector, and the calculation of the relative coordinates between the ray source and the detector is assisted by relying on the mechanical positioning of the system, thereby reducing the calculation amount of coordinate estimation, improving the relative position accuracy or realizing real-time position calibration, and avoiding secondary capturing, and thus realizing convenient three-dimensional imaging.

Description

Coordinate calibration device and calibration method based on distributed X-ray source imaging system Technical Field

[0001] This disclosure relates to the field of medical clinical diagnosis, and in particular to a coordinate calibration device, calibration method and imaging system based on a distributed X-ray source imaging system. Background Technology

[0002] Digital tomosynthesis (DT) is an X-ray imaging technique characterized by requiring only a small angle of projection to obtain tomographic images parallel to the detector direction, enabling the acquisition of depth information within objects. Traditional digital radiography (DR) acquires superimposed images of object structures; when lesions are obscured by this superimposed image, misdiagnosis is possible. DT, however, can obtain depth information within objects, improving diagnostic success rates. Compared to traditional CT, DT offers advantages such as lower radiation dose and higher resolution. In a DT system, the relative geometrical coordinate accuracy of the light source and detector has a crucial impact on the quality of the reconstructed image.

[0003] Common geometric calibration methods include visible light calibration, phantom calibration, and triangulation calibration. Visible light calibration deduces the relative coordinates of the detector and the X-ray source based on the principle of structured light. Phantom geometric calibration inverts the relative coordinates of the source and detector based on the characteristics of specific calibration materials on the phantom in the projection diagram. Triangulation calibration calculates the relative relationship between the source and detector by combining a device capable of transmitting and receiving signals (RF transceiver, electromagnetic coil, etc.) with a corresponding induction signal device.

[0004] Existing phantom calibration methods are all based on coordinate calibration methods for mobile single-point source systems. These methods require calculating the spatial relative coordinates of the source and probe at each point of the light source, resulting in a large amount of coordinate calculation and low efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a coordinate calibration device, calibration method, and imaging system based on a distributed X-ray source imaging system. This system can improve relative position accuracy or achieve real-time position calibration, avoid secondary imaging, and enable more convenient three-dimensional imaging.

[0006] According to one aspect of the inventive concept of this disclosure, a coordinate calibration device based on a distributed X-ray source imaging system is provided, comprising:

[0007] The radiation source is configured to emit X-rays;

[0008] Detectors, including:

[0009] The detector is configured to be positioned on both sides of the target to be measured, respectively, and the detector is configured to receive the X-rays to image the target to be measured.

[0010] A first marking section is located between the detector section and the X-ray source. The first marking section includes a region of interest and a non-region of interest disposed outside the region of interest. The image of the target under test after exposure is located in the region of interest. A plurality of first marking points with three-dimensional geometric shapes are disposed on the first marking section. The image of the first marking points after exposure is located in the first marking section for coordinate calibration of X-ray imaging.

[0011] The coordinate calibration includes calculating the relative positional relationship between the detector and the radiation source using the shapes of multiple first marker points and the imaging shapes of multiple first marker points. The coordinate calibration uses the same set of data as X-ray scanning of the object and performing three-dimensional imaging.

[0012] According to some embodiments of this disclosure, each of the first marker points includes a marker symbol or a marker graphic, and different marker symbols or marker graphics have a predetermined relative positional relationship.

[0013] According to some embodiments of this disclosure, at least one of the first marker points, after exposure, is located in the region of non-interest for coordinate calibration of X-ray imaging; and / or, at least one of the first marker points, after exposure, is located in the region of interest for coordinate calibration of X-ray imaging.

[0014] According to some embodiments of this disclosure, the first marker point is dot-shaped, filament-shaped, strip-shaped, L-shaped columnar, or S-shaped columnar.

[0015] According to some embodiments of this disclosure, the number of the first marker points is less than or equal to four.

[0016] According to some embodiments of this disclosure, the first marker point is embedded on the top of the first marker portion on the side away from the detector portion.

[0017] According to some embodiments of this disclosure, the detection unit and the first marking unit are located on the same side of the target to be tested, and the target to be tested, the first marking unit, and the detection unit are sequentially attached to each other.

[0018] According to some embodiments of this disclosure, the coordinate calibration device further includes:

[0019] The first support has one end connected to the detector and the other end connected to the radiation source. The first support is a rigid structure to keep the relative positions of the detector and the radiation source unchanged.

[0020] According to some embodiments of this disclosure, the coordinate calibration device further includes:

[0021] The second bracket has one end connected to the detection unit and the other end connected to the first marking unit. The detection unit and the first marking unit are located on opposite sides of the target to be tested. The second bracket is a rigid structure to keep the relative positions of the detection unit and the first marking unit unchanged.

[0022] According to some embodiments of this disclosure, the other end of the second bracket extends away from the detector and is connected to the radiation source. The second bracket is adapted to maintain the relative positions of the radiation source, the detector, and the first marker unchanged.

[0023] According to some embodiments of this disclosure, the first marker and the detector are located on opposite sides of the target to be measured, and the coordinate calibration device further includes:

[0024] The third support has one end connected to the first marking part and the other end connected to the radiation source. The third support is a rigid structure to keep the relative positions of the first marking part and the radiation source unchanged.

[0025] According to some embodiments of this disclosure, the coordinate calibration device further includes:

[0026] The second marking part is located between the detection part and the target to be tested, and the two opposite sides of the second marking part are respectively attached to the target to be tested and the detection part. The top of the second marking part is provided with a second marking point on the side away from the detection part.

[0027] According to some embodiments of this disclosure, the coordinate calibration device further includes:

[0028] The second marking part and the detection part are respectively located on both sides of the target to be tested, and a second marking point is embedded on the top side of the second marking part away from the detection part;

[0029] The fourth bracket is connected at one end to the detection unit and at the other end to the second marking unit. The fourth bracket is a rigid structure to keep the relative positions of the detection unit and the second marking unit unchanged.

[0030] According to some embodiments of this disclosure, the thickness of the first marking portion and the second marking portion ranges from 1-3 mm or 2-15 mm.

[0031] According to some embodiments of this disclosure, the radiation source is a distributed multi-point source array.

[0032] According to some embodiments of this disclosure, both ends of the first bracket are connected to the detection unit and the radiation source by magnetic attraction, respectively; and / or,

[0033] The two ends of the second bracket are connected to the detection unit and the first marking unit respectively by magnetic attraction; and / or,

[0034] The two ends of the third bracket are respectively connected to the first marking part and the radiation source by magnetic attraction; and / or,

[0035] The two ends of the fourth bracket are connected to the detection unit and the second marking unit by magnetic attraction, respectively.

[0036] According to some embodiments of this disclosure, the relative positional relationship between the detector and the radiation source includes the flip angle and offset angle of the detector relative to the radiation source, as well as the distance between the detector and the radiation source.

[0037] According to some embodiments of this disclosure, the target to be tested is a tooth, torso, or the entire human body.

[0038] According to another aspect of the inventive concept of this disclosure, an imaging system is provided, comprising:

[0039] The coordinate calibration device described above;

[0040] A data conversion device is configured to convert the detection signal generated by the detection unit of the coordinate calibration device into digital data; and

[0041] An image processing apparatus configured to perform imaging based on the digital data.

[0042] According to another aspect of the inventive concept of this disclosure, a coordinate calibration method based on a distributed X-ray source imaging system is provided, applicable to the coordinate calibration device described in the above embodiments; the coordinate calibration method includes:

[0043] S01: Determine the relative position of at least one of the detector and the radiation source with respect to the first marker;

[0044] S02: Fix the detector in the target area, so that the detector and the radiation source are located on opposite sides of the target to be tested;

[0045] S03: Guide the rays emitted from the ray source to the detection unit; and

[0046] S04: The image data acquired by the detection unit is calibrated according to the coordinate position data of at least one of the detection unit and the radiation source with the first mark point on the first mark unit;

[0047] The first marker point has a three-dimensional geometric shape. Using the shape of the first marker point and its imaging coordinates, the spatial coordinates of the radiation source and the detector are calculated to obtain the relative positional relationship between the radiation source and the detector.

[0048] According to some embodiments of this disclosure, step S01 above includes:

[0049] The detector is fixed within the target area such that the detector and the first marker are located on the same side of the target to be tested, and the target to be tested, the first marker, and the detector are sequentially attached; or,

[0050] The detector is fixed within the target area, such that the first marker and the detector are located on opposite sides of the target to be tested.

[0051] According to some embodiments of this disclosure, the relative positional relationship between the radiation source and the detector is expressed as a functional relationship between the spatial coordinates of each focal point of the radiation source and each pixel of the detector.

[0052] According to some embodiments of this disclosure, the steps for obtaining the focal points of the radiation source include:

[0053] S11: Establish a spatial coordinate system with the center point of the detector as the origin, define the coordinates of the first focus of the ray source as (x, y, z), and derive the spatial coordinates of the first marker point based on the coordinates of the ray source or the detector.

[0054] S12: Simulate the emitted beam based on the first focal coordinates, the first marker point, and the geometric relationship of the detector to obtain a simulated projection image;

[0055] S13: Extract the features of the marked points in the simulated projection image, and define them as simulated features f. i (x,y,z), (i=1,2,…,n); calculate the features of the corresponding marker points in the real projected image, defined as g i (x,y,z),(i=1,2,…,n);

[0056] S14: Obtain the simulated coordinates of the first focus by solving the objective function, wherein the objective function is:

[0057] S15: Sequentially switch all focal points of the X-ray source and repeat steps S11 to S14 until the simulated coordinates of all focal points are calculated.

[0058] According to the coordinate calibration device of the distributed X-ray source imaging system according to the embodiments of this disclosure, the relative coordinates of the source probe are corrected by using known parameters on the marker part, the flip angle and offset angle of the marker part are calculated by using the shape of the marker point and the imaging, and the imaging of the detector part is corrected. Relying on the advantages of the system's mechanical positioning, the relative coordinates of the source probe are calculated, the amount of calculation for coordinate estimation is reduced, the relative position accuracy can be improved or real-time position calibration can be achieved, secondary shooting is avoided, and more convenient three-dimensional imaging is achieved. Attached Figure Description

[0059] Figure 1 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to an exemplary embodiment of the present disclosure;

[0060] Figure 2 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0061] Figure 3 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0062] Figure 4 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0063] Figure 5 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0064] Figure 6 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0065] Figure 7 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure;

[0066] Figure 8 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system applied to a whole-body human scan according to another exemplary embodiment of the present disclosure.

[0067] Figure 9 is a flowchart of a coordinate calibration method based on a distributed X-ray source imaging system according to an exemplary embodiment of the present disclosure;

[0068] Figure 10 is a flowchart of the steps for obtaining the focal points of a radiation source in a coordinate calibration method based on a distributed radiation source imaging system according to an exemplary embodiment of the present disclosure.

[0069] Explanation of reference numerals in the attached diagram: 1. Detector, 2. X-ray source, 3. First marking unit, 3'. Second marking unit, 4. First marking point, 4'. Second marking point, 5. First support, 6. Second support, 7. Third support, 8. Fourth support, 9. Coordinate calibration device. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0071] However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments of this disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure.

[0072] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0073] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0074] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0075] In embodiments of this disclosure, known parameters on the phantom are used to correct the relative coordinates of the source probes. In some exemplary embodiments of this disclosure, for coordinate calibration of distributed multi-point source systems, the relative coordinates of each point source in the distributed point source system are highly accurate. The advantages of the system's mechanical positioning can be relied upon to assist in calculating the relative coordinates of the source probes, and the computational workload of coordinate estimation can be greatly reduced.

[0076] The embodiments disclosed herein mainly propose an innovative calibration scheme for the relative positional relationship between the source and probe in a distributed multi-point source system. Since the positions of each point source in a distributed multi-point source system are fixed, this prior information can be fully utilized to locate the relative positional relationship between the source and probe. On the other hand, the probe usually needs to be disassembled, assembled, and positioned in the target area. There are usually devices such as supports between it and the point sources for positioning to determine the relative positional relationship. However, the relative positioning accuracy of the source and probe achieved by mechanical structures is poor. For example, in 2D perspective imaging such as dental X-ray machines, it does not affect the image clarity, but in 3D tomographic imaging, since data synthesis from multiple perspectives is required, insufficient positioning accuracy will significantly affect the 3D imaging quality. Moreover, there is usually a certain coordinate error generated during the disassembly of the probe. Therefore, the relative coordinates between the point source and the probe still need to be corrected by a calibration method to improve the relative positional accuracy or achieve real-time position calibration. Meanwhile, embodiments of this disclosure also propose using a detector with special markings, using fewer marking points, such as one or two, to complete the calibration and scanning imaging of the source-detector relative position in a single shot, avoiding secondary shooting, achieving more convenient three-dimensional imaging, and correcting the effects of marking part skew / flipping during bonding and fixing.

[0077] The embodiments of this disclosure provide a coordinate calibration device, calibration method and imaging system based on a distributed X-ray source imaging system, which can improve the relative position accuracy or realize real-time position calibration, avoid secondary shooting and realize more convenient three-dimensional imaging.

[0078] Figure 1 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to an exemplary embodiment of the present disclosure.

[0079] According to one aspect of the inventive concept of this disclosure, a coordinate calibration device based on a distributed X-ray source imaging system is provided. As shown in FIG1, the coordinate calibration device may include a detector and a X-ray source 2. The detector includes a detection unit 1 and a marking unit 3. In this embodiment, the marking unit 3 is configured to calibrate the relative positional relationship between the X-ray source 2 and the detection unit 1. Therefore, the marking unit 3 can be regarded as a coordinate calibration device or a part of a coordinate calibration device.

[0080] For example, in embodiments of this disclosure, the X-ray source 2 can be a distributed X-ray source, which may include multiple target points, such as multiple X-ray target points. For example, in Figures 1-7, the multiple small rectangular black dots in the X-ray source 2 can be regarded as multiple target points of the distributed X-ray source. In a distributed X-ray source, a target point refers to the emission point or focal point of the X-ray source 2. Specifically, high-energy electrons are emitted from the cathode and bombard the metal anode target, thereby generating X-rays. The energy of the emitted X-rays depends on the material of the anode target, while the intensity of the X-rays depends on the electron flux and electron energy bombarding the anode target. In a distributed X-ray source, multiple cathodes correspond one-to-one with multiple target points, so that multiple target points receive electron beams from multiple cathodes to generate multiple X-ray beams. This design enables the distributed X-ray source to achieve the effect of generating more X-ray radiation sources using fewer cathode assemblies, improving system stability, reducing the number of cathode assemblies used, and lowering the production cost of the equipment.

[0081] In imaging systems utilizing distributed X-ray sources, multiple projection datasets can be acquired from various angles by combining multiple target points and activating them in a predetermined order at different angles. These projection datasets can be configured for computer reconstruction algorithms to generate high-quality cross-sectional images. One advantage of using distributed X-ray sources is the reduction of artifacts and improved image quality. By using multiple target points, the emission positions of the X-ray beam are more uniformly distributed, providing more projection angles and data, reducing artifacts in reconstructed images, and providing more accurate anatomical information. In other words, target points in a distributed X-ray source refer to the points or regions that emit X-ray beams, and their distribution contributes to obtaining high-quality projection data configured for image reconstruction.

[0082] In embodiments of this disclosure, multiple target points in a distributed radiation source can be arranged along a predetermined first direction. For example, the predetermined first direction can be a straight line or an arc. Embodiments of this disclosure do not impose any particular limitation on the arrangement of target points in a distributed radiation source.

[0083] In some exemplary embodiments of this disclosure, the detection unit 1 may include a plurality of detection units arranged in a one-dimensional or two-dimensional manner.

[0084] For example, the detection unit may include at least one detector crystal. For instance, the detection unit may include one detector crystal. As another example, the detection unit may include multiple detector crystals arranged in a one-dimensional direction, or multiple detector crystals arranged in a two-dimensional direction.

[0085] It should be understood that each detector crystal is a basic unit of the detector, capable of absorbing radiation (e.g., X-rays) and converting it into other forms of energy, such as light or electrical signals. For example, the materials of detector crystals may include oxides and halides (e.g., iodides and fluorides). According to some optional embodiments of this disclosure, the coordinate calibration device can be applied to the calibration of dental tomographic imaging systems. It should be noted that, in this document, the various concepts of this disclosure are illustrated using a dental tomographic imaging system as an example; however, the embodiments of this disclosure are not limited thereto, and the coordinate calibration device provided in the embodiments of this disclosure can be applied to other scanning imaging systems without departing from the spirit and principles of this disclosure.

[0086] According to some embodiments of this disclosure, the detector 1 is configured to be placed in the target area and disposed on both sides of the target to be tested, respectively, along with the radiation source 2. The detector 1 is configured to receive radiation, such as X-rays, to image the target to be tested. For example, the target to be tested is a tooth, and the target area may be inside the oral cavity.

[0087] According to some optional embodiments of this disclosure, the probe 1 and the first marker 3 are located on the same side of the target to be tested, and the target to be tested, the first marker 3, and the probe 1 are sequentially fitted together. The probe 1 is configured to be placed inside the oral cavity and fitted together with the tooth to be imaged. It should be noted that "fitted together" here includes the following situations: the probe 1 is tightly fitted to the inner surface of the tooth; the probe 1 is set inside the oral cavity through a fitting component, and the probe 1 can be a certain distance or gap from the inner surface of the tooth, which is usually small.

[0088] According to some embodiments of this disclosure, the first marking part 3 may be disposed between the detection part 1 and the radiation source 2, and the relative position of the first marking part 3 and the detection part 1 is fixed.

[0089] According to some embodiments of this disclosure, the first marking unit 3 includes a region of interest and a non-region of interest disposed outside the region of interest. The image of the target under test after exposure is located within the region of interest. The first marking unit 3 is provided with a plurality of first marking points 4 having three-dimensional geometric shapes. The image of the first marking points 4 after exposure is located on the first marking unit 3 for coordinate calibration of the X-ray imaging. Coordinate calibration includes calculating the relative positional relationship between the detector unit 1 and the X-ray source 2 using the shapes of the plurality of first marking points 4 and the imaging shapes of the plurality of first marking points 4.

[0090] According to some embodiments of this disclosure, the coordinate calibration and X-ray imaging use the same set of data.

[0091] According to some embodiments of this disclosure, each first marker point 4 includes a marker symbol or marker graphic, and different marker symbols or marker graphics have a predetermined relative positional relationship.

[0092] It should be noted that, in this embodiment, the marking symbols can be English letters, Greek letters, Arabic numerals, etc., and the marking graphics can be circles, squares, triangles, etc.

[0093] According to some embodiments of this disclosure, at least one first marker point 4 is located in a region of non-interest after exposure of the image, so as to perform coordinate calibration of the X-ray imaging.

[0094] According to some embodiments of this disclosure, at least one first marker point 4 is located in the region of interest after exposure to the image, so as to perform coordinate calibration for X-ray imaging.

[0095] It should be noted that in this embodiment, when the exposed image of the first marker point 4 is located within the region of interest, the first marker point 4 will overlap with the exposed image of the target to be tested, and it is necessary to remove the first marker point 4 from the exposed image of the target to be tested. Specifically, the removal of the first marker point 4 from the exposed image can be achieved by extracting the first marker point 4 from the exposed image and performing interpolation.

[0096] According to some embodiments of this disclosure, the relative positional relationship between the detector 1 and the radiation source 2 includes the flip angle and offset angle of the detector 1 relative to the radiation source 2, as well as the distance between the detector 1 and the radiation source 2.

[0097] In this embodiment, the relative coordinates of the source and detector are corrected using known parameters on the marker 3. The spatial coordinates of the X-ray source 2 and the detector 1 are calculated using the shape of the first marker point 4 and the imaging coordinates of the first marker point 4 to obtain the relative positional relationship between the X-ray source 2 and the detector 1. The imaging of the detector 1 is then corrected. The system's mechanical positioning advantage assists in calculating the relative coordinates of the source and detector, reducing the computational load of coordinate estimation. This can improve the accuracy of the relative position or achieve real-time position calibration, avoid secondary imaging, and achieve more convenient intraoral three-dimensional imaging.

[0098] According to some optional embodiments of this disclosure, the first marker point 4, the first marker portion 3, and the detector portion 1 may be tightly bound together and cannot be disassembled. The first marker portion 3 and the detector portion 1 are fixedly connected, for example, they are glued together, and the first marker point 4 is fixedly disposed on the first marker portion 3.

[0099] According to some embodiments of this disclosure, the first marker point 4 is configured to correct geometric errors caused by the disassembly and movement of the detector 1.

[0100] According to some optional embodiments of this disclosure, the first marker point 4 is disposed on the top side of the first marker portion 3 away from the detector portion 1. The thickness of the first marker portion 3 is a known parameter, that is, the distance between the first marker point 4 and the detector portion 1 is a known parameter. Furthermore, due to the fixed connection between the first marker portion 3 and the detector portion 1, the distance between the first marker point 4 and the detector portion 1 remains constant; for example, it will not change due to different positions of the first marker portion 3 and the detector portion 1 within the target oral cavity.

[0101] According to some alternative embodiments of this disclosure, the first marking part 3 is detachably disposed on the detection part 1. That is, one set of first marking points 4 and first marking parts 3 can correspond to one detection part 1, or one set of first marking points 4 and first marking parts 3 can be removed from one detection part module and installed on different detection parts 1 to form a new detection part module, improving applicability and facilitating subsequent cleaning and sterilization. According to some optional embodiments of this disclosure, the above-mentioned coordinate calibration device is suitable for medical imaging systems. Further optionally, the above-mentioned coordinate calibration device is suitable for dental tomographic imaging systems.

[0102] According to some alternative embodiments of this disclosure, the number of the first marker points 4 is less than or equal to four.

[0103] Figure 2 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure.

[0104] According to some alternative embodiments of this disclosure, as shown in FIG2, the coordinate calibration device further includes a first support 5, one end of which is connected to the detector 1 and the other end is connected to the radiation source 2. The first support 5 is a rigid structure to keep the relative positions of the detector 1 and the radiation source 2 unchanged.

[0105] In this embodiment, the detector 1 is fixedly connected to the first support 5, and the radiation source 2 is fixedly connected to the first support 5 to ensure that the relative position and relative distance between the detector 1 and the radiation source 2 remain unchanged, thereby improving the calibration accuracy. The two ends of the first support 5 are connected to the detector 1 and the radiation source 2 respectively via magnetic attraction.

[0106] According to some optional embodiments of this disclosure, the first marker point 4, the first marker portion 3, and the probe portion 1 can be tightly bound and cannot be disassembled. The first marker portion 3 and the probe portion 1 are fixedly connected, for example, they are bonded together, and the first marker point 4 is fixedly disposed on the first marker portion 3. The thickness of the first marker portion 3 is a known parameter, that is, the distance between the first marker point 4 and the probe portion 1 is a known parameter, and due to the fixed connection between the first marker portion 3 and the probe portion 1, the distance between the first marker point 4 and the probe portion 1 remains constant, for example, it will not change due to different positions of the first marker portion 3 and the probe portion 1 within the target oral cavity.

[0107] According to some alternative embodiments of this disclosure, the first marking part 3 is detachably disposed on the detection part 1. That is, one set of first marking points 4 and first marking parts 3 can correspond to one detection part 1, or one set of first marking points 4 and first marking parts 3 can be removed from one detection part module and installed on different detection parts 1 to form a new detection part module, thereby improving applicability and facilitating subsequent cleaning and disinfection.

[0108] Figure 3 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure.

[0109] According to some optional embodiments of this disclosure, as shown in FIG3, the coordinate calibration device further includes a second support 6. One end of the second support 6 is connected to the probe 1, and the other end is connected to the first marking part 3. The probe 1 and the first marking part 3 are respectively located on both sides of the tooth to be imaged. The second support 6 is a rigid structure to keep the relative positions of the probe 1 and the marking part 3 unchanged.

[0110] In this embodiment, the X-ray source 2 is in a free state and is not fixed to the marking module by a support. The first marking point 4 and the first marking part 3 in the marking module are coupled in relative position by a rigid support.

[0111] Figure 4 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure.

[0112] According to some alternative embodiments of this disclosure, as shown in FIG4, the other end of the second bracket 6 extends away from the detector 1 and is connected to the radiation source 2. The second bracket 6 is configured to keep the relative positions of the radiation source 2, the detector 1 and the first marker 3 unchanged.

[0113] In this embodiment, the first marker point 4, the first marker part 3, and the detector part 1 in the marking module are coupled in relative position by a rigid bracket. During calibration and imaging, only the impact of disassembling the detector part 1 on the coordinates needs to be considered, resulting in high relative geometric coordinate stability. The two ends of the second bracket 6 are connected to the detector part 1 and the first marker part 3 respectively via magnetic attraction.

[0114] According to some embodiments of this disclosure, the X-ray source 2 is a distributed multi-point source array.

[0115] According to some optional embodiments of this disclosure, the first marker point 4 is dot-shaped, filament-shaped, strip-shaped, L-shaped column-shaped, or S-shaped column-shaped.

[0116] In this embodiment, when the detector 1 is in contact with the target, it may flip or shift, leading to inaccurate target imaging. Therefore, the flip angle and shift angle of the detector 1 are calculated using the shape of the first marker point 4 and the imaging shape of the first marker point 4, and then the imaging is corrected using the flip angle and shift angle.

[0117] According to some optional embodiments of this disclosure, for example, the first marker point 4 is a cube with a side length of a. Under normal circumstances, when there is no flipping or shifting, the image of the first marker point 4 is a square of a*a. If the image of the first marker point 4 is a rectangle of √2a*a, it means that the detector 1 has shifted by 45°. Based on this, the image of the target to be tested is also corrected and adjusted accordingly.

[0118] According to some embodiments of this disclosure, as shown in Figures 1 to 4, the detector and the first marker point 4 form a marker, and the spatial coordinates of the marker are derived from the detector coordinates.

[0119] Figure 5 is a schematic diagram of the structure of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure.

[0120] According to some embodiments of this disclosure, as shown in FIG5, the first marker point 4 is bound to the X-ray source 2, and the size and position of the first marker point 4 are adjusted according to the source-detector relationship so that it is located in the region of non-interest in the exposed image.

[0121] In this embodiment, the spatial coordinates of the marker are derived based on the coordinates of the ray source 2.

[0122] Figure 6 is a schematic diagram of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure. Figure 7 is a schematic diagram of a coordinate calibration device based on a distributed X-ray source imaging system according to another exemplary embodiment of the present disclosure.

[0123] According to some embodiments of this disclosure, as shown in FIG6, the coordinate calibration device further includes a third support 7 and a second marking part 3'. One end of the third support 7 is connected to the first marking part 3, and the other end is connected to the radiation source 2. The third support 7 is a rigid structure to keep the relative positions of the first marking part 3 and the radiation source 2 unchanged. The second marking part 3' is located between the detection part 1 and the target to be measured, and the opposite sides of the second marking part 3' are respectively attached to the target to be measured and the detection part 1. A second marking point 4' is embedded on the top side of the second marking part 3' away from the detection part 1. That is, the first marking part 3 and the second marking part 3' are provided and bound to the radiation source 2 and the detection part 1 respectively. The first marking part 3 and the second marking part 3' are respectively provided with a first marking point 4 and a second marking point 4'.

[0124] In this embodiment, the spatial coordinates of the marker are derived based on the coordinates of the X-ray source 2 and the detector, respectively. A first marker point 4 (bound to the X-ray source 2) and a second marker point 4' (bound to the detector 1) are defined. To address the issue of poor spatial resolution of the first marker point 4, only the centroid of the first marker point 4 can be used for calculation (i.e., the center point of the side length is discarded). This scheme not only solves the coordinate error in the source-detector distance direction but also solves the coordinate estimation error caused by insufficient spatial resolution, greatly improving the coordinate estimation accuracy.

[0125] According to some embodiments of this disclosure, as shown in FIG7, the coordinate calibration device further includes a third support 7, a second marking part 3', and a fourth support 8. The second marking part 3' and the detector part 1 are located on opposite sides of the target to be measured. A second marking point 4' is embedded on the top side of the second marking part 3' away from the detector part 1. One end of the fourth support 8 is connected to the detector part 1, and the other end is connected to the second marking part 3'. The fourth support 8 is a rigid structure to maintain the relative position of the detector part 1 and the second marking part 3'. The two ends of the third support 7 are connected to the first marking part 3 and the radiation source 2 respectively by magnetic attraction. The two ends of the fourth support 8 are connected to the detector part 1 and the second marking part 3' respectively by magnetic attraction.

[0126] According to some embodiments of this disclosure, the first marker point 4 can be installed between the probe unit 1 and the tooth or between the tooth 1 and the light source, depending on the selection of two probe unit modules. The probe unit 1 is placed in an area that does not affect tooth imaging. When the first marker point 4 is placed between the probe unit 1 and the tooth, there should be a certain distance between the first marker point 4 and the probe unit 1, and the middle can be filled by the first marker unit 3 of known thickness. At this time, the first marker point 4, the first marker unit 3 and the probe unit 1 are integrated, and are simultaneously placed into or removed from the oral cavity during scanning. When the first marker point 4 is installed between the tooth and the light source, the probe unit 1 and the first marker unit 3 can be connected by a rigid bracket to fix the relative coordinates of the probe unit 1 and the first marker point 4.

[0127] According to some optional embodiments of this disclosure, the first marking portion 3 and the second marking portion 3' are made of a material that is easily penetrated by rays, such as plastic, PMMA, etc.

[0128] According to some optional embodiments of this disclosure, when the coordinate calibration device is applied to a dental tomographic imaging system, that is, when the target to be measured is a tooth, the thickness of the first marking part 3 and the second marking part 3' is 1 to 3 mm. Alternatively, when the coordinate calibration device is applied to a general medical imaging system, that is, when the target to be measured is a limb joint, etc., the thickness of the marking part 3 is 2 to 15 mm.

[0129] According to some embodiments of this disclosure, the implementation shown in Figures 1 and 3 adopts a split structure. By separating the detector 1 from the radiation source 2, it is possible to make more detailed and accurate adjustments for different application scenarios, with higher degrees of freedom, more flexible positioning, and easier and more accurate positioning of small and concealed targets to be detected.

[0130] Figure 8 is a structural schematic diagram of a coordinate calibration device based on a distributed X-ray source imaging system applied to a whole-body human scan, according to yet another exemplary embodiment of the present disclosure.

[0131] According to some embodiments of this disclosure, in the implementation shown in FIG8, the target to be measured is teeth, torso, or the entire human body. In other words, the coordinate calibration device 9 of this embodiment can also be applied to the calibration of geometric coordinates for a full-body human scan. The coordinate calibration device 9 includes a detector containing a plurality of first marker points 4 and / or a plurality of second marker points 4'.

[0132] According to another aspect of the inventive concept of this disclosure, an imaging system is provided, including the coordinate calibration device, data transformation device and image processing device as described above.

[0133] According to some embodiments of this disclosure, the data conversion device is configured to convert the detection signal generated by the detection unit 1 of the coordinate calibration device into digital data.

[0134] According to some embodiments of the present disclosure, the image processing apparatus is configured to perform imaging based on digital data.

[0135] Figure 9 is a flowchart of a coordinate calibration method based on a distributed X-ray source imaging system according to an exemplary embodiment of the present disclosure.

[0136] According to another aspect of the inventive concept of this disclosure, a coordinate calibration method based on a distributed X-ray source imaging system is provided, which is applicable to the coordinate calibration device described in the above embodiments. As shown in FIG9, the coordinate calibration method includes steps S01 to S04.

[0137] According to some embodiments of this disclosure, step S01 includes: determining the relative position of at least one of the detector 1 and the radiation source 2 with the first marker 3.

[0138] According to some embodiments of this disclosure, step S02 includes: fixing the detector 1 within the target area, such that the detector 1 and the radiation source 2 are located on opposite sides of the target to be tested. Optionally, the target to be tested is a tooth or a limb joint.

[0139] According to some embodiments of this disclosure, step S03 includes: guiding the rays emitted from the ray source 2 to the detection unit 1.

[0140] According to some embodiments of this disclosure, step S04 includes: performing coordinate calibration on the image data acquired by the detection unit 1 based on the relative position data of at least one of the detection unit 1 and the radiation source 2 with the first mark point 4 on the first mark unit 3.

[0141] According to some embodiments of this disclosure, the first marker point 4 has a three-dimensional geometric shape. Using the shape of the first marker point 4 and the imaging coordinates of the first marker point 4, the spatial coordinates of the X-ray source 2 and the detector 1 are calculated to obtain the relative positional relationship between the X-ray source 2 and the detector 1.

[0142] It should be noted that in this embodiment, the first marking part 3 can be bound to the detector part 1, or the first marking part 3 can also be bound to the radiation source 2.

[0143] According to some embodiments of this disclosure, step S01 includes fixing the detector 1 in the target area, such that the detector 1 and the first marker 3 are located on the same side of the target to be tested, and the target to be tested, the first marker 3 and the detector 1 are sequentially attached.

[0144] In embodiments of this disclosure, step S01 may also include fixing the detector 1 within the target area, such that the first marker 3 and the detector 1 are located on opposite sides of the target to be measured. According to some embodiments of this disclosure, the relative positional relationship between the X-ray source 2 and the detector 1 is expressed as a functional relationship between the spatial coordinates of each focal point of the X-ray source 2 and each pixel of the detector 1.

[0145] Figure 10 is a flowchart of the steps for obtaining the focal points of a radiation source in a coordinate calibration method based on a distributed radiation source imaging system according to an exemplary embodiment of the present disclosure.

[0146] According to some embodiments of this disclosure, the calibration method involves establishing a spatial coordinate system with the center point of the detector 1 as the origin, and solving for the coordinates of all focal points of the distributed radiation source. Specifically, as shown in FIG10, the steps for obtaining each focal point of the radiation source 2 include steps S11 to S15.

[0147] According to some embodiments of this disclosure, S11 includes: establishing a spatial coordinate system with the center point of the detector 1 as the origin, defining the coordinates of the first focus of the ray source 2 as (x, y, z), and deriving the spatial coordinates of the first marker point 4 based on the coordinates of the ray source 2 or the coordinates of the detector 1.

[0148] According to some embodiments of this disclosure, S12 includes: simulating the emission of a beam based on the geometric relationship between the first focal coordinates, the first marker point 4, and the detector 1, thereby obtaining a simulated projection image.

[0149] According to some embodiments of this disclosure, S13 includes: extracting features of marked points in the simulated projection image, defining them as simulated features f. i (x,y,z), (i=1,2,…,n); calculate the features of the corresponding marker points in the real projected image, defined as g i (x,y,z), (i=1,2,…,n). Optionally, the characteristics of the marker point include the coordinates of the center point of the marker point's side length, the coordinates of the marker point's centroid, etc.

[0150] According to some embodiments of this disclosure, S14 includes: obtaining the simulated coordinates of the first focus by solving an objective function, wherein the objective function is...

[0151] Here, norm() represents the norm for calculating the difference between features, and can be selected as 2-norm, 1-norm, infinite norm, etc. Argmin represents finding the minimum value of the objective function.

[0152] According to some embodiments of this disclosure, S15 includes: sequentially switching all focal points of the X-ray source 2, repeating steps S11 to S14, until the simulated coordinates of all focal points are calculated.

[0153] According to some embodiments of this disclosure, in S15, since the actual geometric relationship between each focus is known, the solution of the focus coordinates is explained by taking the linear relationship between the coordinates of each focus as an example: the simulated coordinates are fitted (least square method, etc.) to obtain the coordinates of the point closest to the simulated coordinates of the focus on the fitted line, which is the focus coordinate.

[0154] According to some embodiments of this disclosure, before performing intraoral dental tomography or limb joint imaging, the probe module is installed as required: the first marker point 4 of the cube can be made of a radiation-permeable material and placed in an area that does not affect the imaging quality of the target tooth / limb joint. The main function of the first marker 3 is to fix the positional relationship between the first marker point 4 and the probe 1, so as not to affect the imaging quality of the target tooth / limb joint.

[0155] According to some embodiments of this disclosure, when the first marker 4 is installed between the tooth and the probe 1, the first marker 4 is embedded in the first marker 3. The first marker 3 should be tightly attached to the surface of the probe 1 and can be detachable or non-detachable. The non-detachable first marker 3 is bound to the probe 1 and cannot be separated; the detachable first marker 3 can be freely removed from and installed on the probe 1 to form a new probe module as needed.

[0156] According to some embodiments of this disclosure, when the first marker point 4 is installed between the tooth and the radiation source 2, the first marker part 3 and the detector part 1 are connected by a rigid bracket. At this time, the distributed point source and the detector part module can be connected to each other by the rigid bracket, or they can be separated so that the point source is in a relatively free state.

[0157] According to some embodiments of this disclosure, after the phantom is installed, each point source emits beams in sequence. The coordinates of the detector 1 relative to the point source are deduced based on the features of the first marker point 4 on the projection map, and then 3D tomography is performed.

[0158] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. Furthermore, the definitions of the various components described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0159] It should also be noted that, in the specific embodiments of this disclosure, unless otherwise stated otherwise, the numerical parameters in this specification and the appended claims are approximate values ​​and can be changed according to the desired characteristics obtained from the content of this disclosure. Specifically, all numbers used in the specification and claims to indicate dimensions, range conditions, etc., of the composition should be understood to be modified by the term "about" in all cases. Generally, this means that there may be variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0160] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0161] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A coordinate calibration device based on a distributed X-ray source imaging system, comprising: The radiation source is configured to emit X-rays; Detectors, including: The detector is configured to be positioned on both sides of the target to be measured, respectively, and the detector is adapted to receive the X-rays to image the target to be measured. A first marking section is located between the detector section and the X-ray source. The first marking section includes a region of interest and a non-region of interest disposed outside the region of interest. The image of the target under test after exposure is located in the region of interest. A plurality of first marking points with three-dimensional geometric shapes are disposed on the first marking section. The image of the first marking points after exposure is located in the first marking section for coordinate calibration of X-ray imaging. The coordinate calibration includes calculating the relative positional relationship between the detector and the radiation source using the shapes of multiple first marker points and the imaging shapes of multiple first marker points. The coordinate calibration uses the same set of data as X-ray scanning of the object and performing three-dimensional imaging.

2. The coordinate calibration device according to claim 1, wherein, Each of the first marker points includes a marker symbol or a marker graphic, and different marker symbols or marker graphics have a predetermined relative positional relationship.

3. The coordinate calibration device according to claim 1, wherein, At least one of the first marker points is located in the region of non-interest after exposure, so as to perform coordinate calibration of the X-ray imaging; And / or, An image of at least one of the first marker points after exposure is located in the region of interest to perform coordinate calibration for X-ray imaging.

4. The coordinate calibration device according to claim 1, wherein, The first marker point can be dot-shaped, filament-shaped, strip-shaped, L-shaped columnar, or S-shaped columnar.

5. The coordinate calibration device according to claim 1, wherein, The number of the first marker points is less than or equal to four.

6. The coordinate calibration device according to claim 1, wherein, The first marker point is embedded on the top of the first marker part on the side away from the detector part.

7. The coordinate calibration device according to claim 6, wherein, The detection unit and the first marking unit are located on the same side of the target to be tested, and the target to be tested, the first marking unit, and the detection unit are sequentially attached to each other.

8. The coordinate calibration device according to claim 7, wherein, The coordinate calibration device further includes: The first support has one end connected to the detector and the other end connected to the radiation source. The first support is a rigid structure to keep the relative positions of the detector and the radiation source unchanged.

9. The coordinate calibration device according to claim 1, wherein, The coordinate calibration device further includes: The second bracket has one end connected to the detection unit and the other end connected to the first marking unit. The detection unit and the first marking unit are located on opposite sides of the target to be tested. The second bracket is a rigid structure to keep the relative positions of the detection unit and the first marking unit unchanged.

10. The coordinate calibration device according to claim 9, wherein, The other end of the second bracket extends away from the detector and is connected to the radiation source. The second bracket is configured to keep the relative positions of the radiation source, the detector and the first marker unchanged.

11. The coordinate calibration device according to claim 1, wherein, The first marker and the detector are located on opposite sides of the target to be measured, and the coordinate calibration device further includes: The third support has one end connected to the first marking part and the other end connected to the radiation source. The third support is a rigid structure to keep the relative positions of the first marking part and the radiation source unchanged.

12. The coordinate calibration device according to claim 11, wherein, The coordinate calibration device further includes: The second marking part is located between the detection part and the target to be tested, and the two opposite sides of the second marking part are respectively attached to the target to be tested and the detection part. The top of the second marking part is provided with a second marking point on the side away from the detection part.

13. The coordinate calibration device according to claim 11, wherein, The coordinate calibration device further includes: The second marking part and the detection part are respectively located on both sides of the target to be tested, and a second marking point is embedded on the top side of the second marking part away from the detection part; The fourth bracket is connected at one end to the detection unit and at the other end to the second marking unit. The fourth bracket is a rigid structure to keep the relative positions of the detection unit and the second marking unit unchanged.

14. The coordinate calibration device according to claim 1, wherein, The thickness of the first marking portion and the second marking portion ranges from 1-3 mm or 2-15 mm.

15. The coordinate calibration device according to claim 1, wherein, The radiation source is a distributed multi-point source array.

16. The coordinate calibration device according to claim 1, wherein, The two ends of the first bracket are connected to the detection unit and the radiation source respectively by magnetic attraction; and / or, The two ends of the second bracket are connected to the detection unit and the first marking unit respectively by magnetic attraction; and / or, The two ends of the third bracket are respectively connected to the first marking part and the radiation source by magnetic attraction; and / or, The two ends of the fourth bracket are connected to the detection unit and the second marking unit by magnetic attraction, respectively.

17. The coordinate calibration device according to claim 1, wherein, The relative positional relationship between the detector and the radiation source includes the flip angle and offset angle of the detector relative to the radiation source, as well as the distance between the detector and the radiation source.

18. The coordinate calibration device according to claim 1, wherein, The target to be tested is a tooth, torso, or the entire human body.

19. An imaging system, comprising: The coordinate calibration device as described in any one of claims 1 to 18; A data conversion device is configured to convert the detection signal generated by the detection unit of the coordinate calibration device into digital data; and An image processing apparatus configured to perform imaging based on the digital data.

20. A coordinate calibration method based on a distributed X-ray source imaging system, applicable to the coordinate calibration device described in any one of claims 1-18; The coordinate calibration method includes: S01: Determine the relative position of at least one of the detector and the radiation source with respect to the first marker; S02: Fix the detector in the target area, so that the detector and the radiation source are located on opposite sides of the target to be tested; S03: Guide the rays emitted from the ray source to the detection unit; and S04: The image data acquired by the detection unit is calibrated according to the coordinate position data of at least one of the detection unit and the radiation source with the first mark point on the first mark unit; The first marker point has a three-dimensional geometric shape. Using the shape of the first marker point and its imaging coordinates, the spatial coordinates of the radiation source and the detector are calculated to obtain the relative positional relationship between the radiation source and the detector.

21. The coordinate calibration method based on a distributed X-ray source imaging system according to claim 20, wherein, Step S01 includes: The detector is fixed within the target area such that the detector and the first marker are located on the same side of the target to be tested, and the target to be tested, the first marker, and the detector are sequentially attached; or, The detector is fixed within the target area, such that the first marker and the detector are located on opposite sides of the target to be tested.

22. The coordinate calibration method based on a distributed X-ray source imaging system according to claim 20, wherein, The relative positional relationship between the X-ray source and the detector is expressed as a functional relationship between the spatial coordinates of each focal point of the X-ray source and each pixel of the detector.

23. The coordinate calibration method based on a distributed X-ray source imaging system according to claim 22, wherein, The steps for obtaining each focal point of the X-ray source include: S11: Establish a spatial coordinate system with the center point of the detector as the origin, define the coordinates of the first focus of the ray source as (x, y, z), and derive the spatial coordinates of the first marker point based on the coordinates of the ray source or the detector. S12: Simulate the emitted beam based on the first focal coordinates, the first marker point, and the geometric relationship of the detector to obtain a simulated projection image; S13: Extract the features of the marked points in the simulated projection image, and define them as simulated features f. i (x,y,z), (i=1,2,…,n); calculate the features of the corresponding marker points in the real projected image, defined as g i (x,y,z),(i=1,2,…,n); S14: Obtain the simulated coordinates of the first focus by solving the objective function, wherein the objective function is: S15: Sequentially switch all focal points of the X-ray source and repeat steps S11 to S14 until the simulated coordinates of all focal points are calculated.

Images