Imaging system and imaging method

Abstract

The invention relates to an imaging system and an imaging method. The imaging system comprises a radiation source; and an image sensor; wherein the image sensor comprises a first radiation detector and a second radiation detector, each comprising a planar surface configured to receive radiation from the radiation source; wherein the planar surface of the first radiation detector is not parallel to the planar surface of the second radiation detector; wherein the image sensor is configured to capture an image of the scene by using the first radiation detector and the second radiation detector and using the radiation; wherein the radiation source is located outside the scene, and the radiation has passed through the scene before reaching at least one of the first radiation detector and the second radiation detector.

Description

[0001] This application is a divisional application of a patent application with application number 201880096886.0, whose application date is September 7, 2018 and invention name is “An image sensor with radiation detectors with different orientations”. [Technical field]

[0002] The present invention relates to an imaging system and an imaging method. [Background technology]

[0003] A radiation detector is a device that can be used to measure the flux, spatial distribution, spectrum, or other properties of radiation.

[0004] Radiation detectors can be used in many applications, one important of which is imaging. Radiation imaging is a radiographic technique that can be used to reveal the internal structure of objects of inhomogeneous composition and opaque objects, such as the human body.

[0005] Early radiation detectors used for imaging included photographic plates and photographic films. Photographic plates can be glass plates with a light-sensitive emulsion coating. Although photographic plates have been replaced by photographic films, they are still used in special cases because of the superior quality and extreme stability they offer. Photographic films can be plastic films such as strips or sheets with a light-sensitive emulsion coating.

[0006] In the 1980s, photoexcitable phosphor plates (PSP plates) became available. PSP plates contain phosphor materials with color centers in their crystal lattices. When the PSP plates are exposed to radiation, the electrons excited by the radiation are trapped in the color centers until they are stimulated by a laser beam scanned over the surface of the PSP plates. When the laser scans the PSP plates, the trapped excited electrons emit light that is collected by a photomultiplier tube, which is converted into a digital image. In contrast to photographic plates and photographic films, PSP plates are reusable.

[0007] Another type of radiation detector is a radiation image intensifier. The components of a radiation image intensifier are usually sealed in a vacuum. Compared to photographic plates, photographic films, and PSP plates, radiation image intensifiers can produce real-time images, that is, no post-exposure processing is required to produce an image. The radiation first hits the input phosphor (e.g., cesium iodide) and is converted into visible light. The visible light then hits the photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes electron emission. The number of electrons emitted is proportional to the intensity of the incident radiation. The emitted electrons are projected onto the output phosphor through an electron optic and cause the output phosphor to produce a visible light image.

[0008] Scintillators operate somewhat similarly to radiation image intensifiers in that the scintillator (e.g., sodium iodide) absorbs radiation and emits visible light, which can then be detected by a suitable image sensor. In the scintillator, the visible light diffuses and scatters in all directions, which reduces spatial resolution. Reducing the scintillator thickness helps improve spatial resolution, but also reduces the absorption of radiation. Therefore, scintillators must achieve a compromise between absorption efficiency and resolution.

[0009] Semiconductor radiation detectors largely overcome the above problems by converting radiation directly into electrical signals. A semiconductor radiation detector may include a semiconductor layer that absorbs radiation at a wavelength of interest. When a radiation particle is absorbed in the semiconductor layer, a plurality of carriers (e.g., electrons and holes) are generated and swept toward electrical contacts on the semiconductor layer under an electric field. The cumbersome thermal management required in currently available semiconductor radiation detectors (e.g., Medipix) may make semiconductor radiation detectors with larger areas and a large number of pixels difficult or impossible to produce. [Summary of the invention]

[0010] According to one aspect of the present invention, an imaging system is disclosed, which includes: a radiation source; and an image sensor; wherein the image sensor includes a first radiation detector and a second radiation detector, each of which includes a planar surface, and the planar surface is configured to receive radiation from the radiation source; wherein the planar surface of the first radiation detector is not parallel to the planar surface of the second radiation detector; wherein the image sensor is configured to capture an image of a scene by using the first radiation detector and the second radiation detector and utilizing the radiation; wherein the radiation source is located outside the scene, and the radiation has passed through the scene before reaching at least one of the first radiation detector and the second radiation detector.

[0011] According to an embodiment, the first radiation detector and the second radiation detector are disposed on a bracket, the bracket has a curved surface, and the first radiation detector and the second radiation detector are arranged on the curved surface of the bracket.

[0012] According to an embodiment, the radiation source emits a cone of radiation.

[0013] According to an embodiment, the first radiation detector and the second radiation detector are configured to move to multiple positions relative to the radiation source, the image sensor is configured to capture images of multiple parts of the scene at the multiple positions respectively by using the first radiation detector and the second radiation detector and utilizing the radiation, and is configured to form an image of the scene by stitching the images of the multiple parts.

[0014] According to an embodiment, the relative position of the first radiation detector with respect to the second radiation detector remains the same in the plurality of positions.

[0015] According to an embodiment, the first radiation detector and the second radiation detector are configured to move relative to the radiation source by rotating about a first axis relative to the radiation source.

[0016] According to an embodiment, the first axis is parallel to the planar surface of the first radiation detector and the planar surface of the second radiation detector.

[0017] According to an embodiment, the first radiation detector and the second radiation detector are configured to move relative to the radiation source by rotating relative to the radiation source around a second axis, the second axis being different from the first axis.

[0018] According to an embodiment, the radiation source is located on the first axis.

[0019] According to an embodiment, the first radiation detector and the second radiation detector are configured to move relative to the radiation source by translating along a first direction relative to the radiation source.

[0020] According to an embodiment, the first direction is parallel to the planar surface of the first radiation detector and the planar surface of the second radiation detector.

[0021] According to an embodiment, the first direction is parallel to the planar surface of the first radiation detector but not parallel to the planar surface of the second radiation detector.

[0022] According to an embodiment, the first radiation detector and the second radiation detector are configured to move relative to the radiation source by translating relative to the radiation source along a second direction, the second direction being different from the first direction.

[0023] According to an embodiment, the first radiation detector and the second radiation detector each comprise a pixel array.

[0024] According to another aspect of the present invention, an imaging method is also disclosed, including: by using a first radiation detector and a second radiation detector and utilizing radiation from a radiation source, when the first radiation detector and the second radiation detector are located at a first position relative to the radiation source, capturing a first image of a first part of the scene; by using the first radiation detector and the second radiation detector and utilizing the radiation from the radiation source, when the first radiation detector and the second radiation detector are located at a second position relative to the radiation source, capturing a second image of a second part of the scene; forming an image of the scene by stitching the first image and the second image; wherein the first radiation detector and the second radiation detector each include a planar surface, the planar surface being configured to receive radiation from the radiation source; wherein the planar surface of the first radiation detector is not parallel to the planar surface of the second radiation detector, wherein the radiation source is located outside the scene, and the radiation has passed through the scene before reaching at least one of the first radiation detector and the second radiation detector.

Brief Description of the Drawings

[0025] Figure 1 A cross-sectional view schematically illustrates a portion of an image sensor according to an embodiment.

[0026] Figure 2A A cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0027] Figure 2B A detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0028] Figure 2C An alternative detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0029] Figure 3 The schematic diagram shows that a radiation detector according to an embodiment may have a pixel array.

[0030] Figure 4A Schematically illustrates carriers generated in a plurality of pixels when radiation particles pass through a radiation absorbing layer at an oblique incident angle.

[0031] Figure 4B Schematically illustrates the charge carriers generated in a single pixel when a radiation particle passes through a radiation absorbing layer at an incident angle of 0°.

[0032] Figure 5 A functional block diagram of an image sensor according to an embodiment is schematically shown.

[0033] Fig. 6A and Figure 6BThe movements of the radiation detector of the image sensor according to the embodiments relative to the radiation source are respectively schematically illustrated.

[0034] Figure 7 It is schematically shown that an image sensor according to an embodiment captures images of multiple parts of a scene.

[0035] Figure 8A-8C Schematically illustrates an arrangement of radiation detectors in an image sensor according to some embodiments.

[0036] Fig. 9 An image sensor with a plurality of hexagonal radiation detectors according to an embodiment is schematically illustrated.

[0037] Fig.10 A flow chart schematically illustrates a method for forming a scene image according to an embodiment, wherein the method forms the scene image by stitching images of multiple parts of a scene captured at multiple locations.

[0038] Fig.11 A system including an image sensor as described herein according to an embodiment is schematically shown, the system being suitable for medical imaging, such as chest radiation radiography, abdominal radiation radiography, etc.

[0039] Fig.12 A system comprising an image sensor as described herein according to an embodiment is schematically illustrated, the system being suitable for dental radiation radiography.

[0040] Fig.13 A cargo scanning or non-intrusive inspection (NII) system including an image sensor as described herein is schematically illustrated according to an embodiment.

[0041] Fig.14 Another cargo scanning or non-intrusive inspection (NII) system including the image sensor described herein according to an embodiment is schematically illustrated.

[0042] Fig.15 A whole body scanning system including the image sensor described herein according to an embodiment is schematically illustrated.

[0043] Fig.16 A radiation computed tomography (radiation CT) system including an image sensor as described herein according to an embodiment is schematically illustrated.

[0044] Fig.17 An electron microscope including the image sensor described herein according to an embodiment is schematically illustrated.

[0045] Fig.18A and Fig.18B Schematically illustrate the following embodiments Figure 2A , Figure 2B and Figure 2C FIG. 1 is a diagram of the electronic system components of a radiation detector shown in FIG.

[0046] Fig.19 Schematic diagram of the time variation of the current flowing through the electrode of the diode or through the electrical contact of the resistor exposed to the radiation absorbing layer according to the embodiment (upper curve), the current caused by the carriers generated by the radiation particles incident on the radiation absorbing layer, and the corresponding time variation of the electrode voltage (lower curve). [Specific implementation method]

[0047] Figure 1 Schematically shows a cross-sectional view of a portion of an image sensor 9000 according to an embodiment. The image sensor 9000 may have a plurality of radiation detectors, for example, a first radiation detector 100A, a second radiation detector 100B. The image sensor 9000 may have a support 107 with a curved surface 102. The plurality of radiation detectors may be arranged on the support 107, for example, Figure 1 An example of is shown on curved surface 102. First radiation detector 100A may have a first planar surface 103A configured to receive radiation from radiation source 109. Second radiation detector 100B may have a second planar surface 103B configured to receive radiation from radiation source 109. First planar surface 103A and second planar surface 103B may not be parallel. Radiation source 109 emits conical radiation. In some embodiments, radiation source 109 may emit radiation of other shapes, such as linear radiation, fan-shaped radiation, parallel radiation, etc. Radiation source 109 is located outside of scene 50, and radiation from radiation source 109 may have passed through scene 50 (e.g., a portion of a human body) before reaching at least one of first radiation detector 100A and second radiation detector 100B.

[0048] Figure 2A A cross-sectional view of a radiation detector 100 according to an embodiment is schematically shown. The radiation detector 100 can be used in an image sensor 9000. The radiation detector 100 may include a radiation absorbing layer 110 and an electronic layer 120 (e.g., an ASIC) for processing or analyzing an electrical signal of incident radiation generated in the radiation absorbing layer 110. In one embodiment, the radiation detector 100 does not include a scintillator. The radiation absorbing layer 110 may include a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the radiation energy of interest. The planar surface 103 of the radiation absorbing layer 110 at the distal end of the electronic layer 120 is configured to receive radiation.

[0049] like Figure 2BAs shown in the detailed cross-sectional view of the radiation detector 100 in FIG. 1 , the radiation absorbing layer 110 according to an embodiment may include one or more diodes (e.g., pin or pn) composed of one or more discrete regions 114 of a first doping region 111, a second doping region 113. The second doping region 113 may be separated from the first doping region 111 by an optional intrinsic region 112. The discrete regions 114 are separated from each other by the first doping region 111 or the intrinsic region 112. The first doping region 111 and the second doping region 113 have opposite types of doping (e.g., the first doping region 111 is p-type and the second doping region 113 is n-type, or the first doping region 111 is n-type and the second doping region 113 is p-type). Figure 2B In the example of FIG. 1 , each discrete region 114 of the second doped region 113 forms a diode together with the first doped region 111 and the optional intrinsic region 112. Figure 2B In the example of FIG. 1 , the radiation absorbing layer 110 includes a plurality of diodes having the first doping region 111 as a common electrode. The first doping region 111 may also have discrete portions.

[0050] When a radiation particle strikes the radiation absorbing layer 110 including the diode, the radiation particle may be absorbed and generate one or more carriers through several mechanisms. One radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward the electrode of one of the diodes under an electric field. The electric field may be an external electric field. The electrical contact 119B may include discrete portions, each of which is in electrical contact with the discrete region 114. In one embodiment, the carriers may drift in different directions so that the carriers generated by a single radiation particle are not substantially shared by two different discrete regions 114 ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to a discrete region 114 different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete regions 114 are not substantially shared by another discrete region 114. A pixel 150 associated with a discrete region 114 may be a region surrounding the discrete region 114, where substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by radiation particles incident therein at an incident angle of 0° flow toward the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of the carriers flow outside the pixel.

[0051] like Figure 2C As shown in an alternative detailed cross-sectional view of the radiation detector 100 in FIG. 1 , the radiation absorbing layer 110 according to an embodiment may include a resistor having a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof, but does not include a diode. The semiconductor may have a high mass attenuation coefficient for the radiation energy of interest.

[0052] When a radiation particle strikes the radiation absorption layer 110 including a resistor but not a diode, the radiation particle may be absorbed and generate one or more carriers through several mechanisms. A radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward the electrical contact 119A and the electrical contact 119B under an electric field. The electric field may be an external electric field. The electrical contact 119B includes discrete portions. In one embodiment, the carriers may drift in different directions so that the carriers generated by a single radiation particle are not substantially shared by two different discrete portions of the electrical contact 119B ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to a discrete portion that is different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete portions of the electrical contact 119B are not substantially shared by another discrete portion of the electrical contact 119B. A pixel 150 associated with one of the discrete portions of the electrical contact 119B may be a region surrounding the discrete portion where substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by radiation particles incident therein at an incident angle of 0° flow toward the discrete portion of the electrical contact 119B. That is, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of the charge carriers flow outside the pixel.

[0053] The electronic layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation particles incident on the radiation absorbing layer 110. The electronic system 121 may include analog circuits such as filter networks, amplifiers, integrators, comparators, or digital circuits such as microprocessors and memories. The electronic system 121 may include components shared by pixels or components dedicated to a single pixel. For example, the electronic system 121 may include an amplifier dedicated to each pixel and a microprocessor shared among all pixels. The electronic system 121 may be electrically connected to the pixel through a through hole 131. The space between the through holes may be filled with a filling material 130, which may increase the mechanical stability of the connection between the electronic layer 120 and the radiation absorbing layer 110. Other bonding technologies may connect the electronic system 121 to the pixel without using a through hole.

[0054] Figure 3The schematic diagram shows that the radiation detector 100 may have an array of pixels 150. The array may be a rectangular array, a honeycomb array, a hexagonal array, or any other suitable array. Each pixel 150 may be configured to detect radiation particles incident thereon, measure the energy of the radiation particles, or both. For example, each pixel 150 may be configured to count the number of radiation particles incident thereon over a period of time, whose energy falls into a plurality of bins. All pixels 150 may be configured to count the number of radiation particles in a plurality of energy bins incident thereon over the same period of time. Each pixel 150 may have its own analog-to-digital converter (ADC), which is configured to digitize an analog signal representing the energy of the incident radiation particles into a digital signal. The ADC may have a resolution of 10 bits or more. Each pixel 150 may be configured to measure its dark current, for example, before or at the same time as each radiation particle is incident thereon. Each pixel 150 may be configured to subtract the contribution of the dark current from the energy of the radiation particles incident thereon. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 is measuring an incoming radiation particle, another pixel 150 may be waiting for a radiation particle to arrive. The pixels 150 may, but need not, be individually addressable.

[0055] The spatial resolution of the image sensor 9000 may depend on the angle of incidence of the radiation incident on the image sensor 9000. The spatial resolution when the angle of incidence is oblique (e.g., >45°) may be lower than the spatial resolution when the angle of incidence is 0°. For example, when the angle of incidence at the center is 0° and the angle of incidence at the edge is oblique, the spatial resolution at the edge of the image sensor 9000 may be lower than the spatial resolution at the center of the image sensor 9000. If the field of view of the image sensor 9000 is large (e.g., 0.5π or greater) or the thickness of the radiation absorbing layer 110 in the radiation detector of the image sensor 9000 is comparable to or greater than the size of the pixel 150, the reduction in spatial resolution from the center to the edge may be significant. The field of view of the image sensor 9000 is the solid angle through which the image sensor 9000 is sensitive to radiation. Figure 4A It is schematically shown that when radiation particles pass through the radiation absorbing layer 110 at an oblique angle of incidence, carriers may be generated in pixels associated with multiple discrete portions of the electrical contact 119B. Figure 4B It is schematically shown that when a radiation particle passes through the radiation absorbing layer 110 at an incident angle of 0°, charge carriers may be generated in a pixel associated with a single discrete portion of the electrical contact 119B.

[0056] In one embodiment, radiation detectors 100 (e.g., 100A and 100B) of image sensor 9000 may be moved to multiple positions relative to radiation source 109. Image sensor 9000 may use radiation detectors 100 and utilize radiation to capture images of multiple portions of scene 50 from radiation source 109 at multiple positions, respectively. Image sensor 9000 may stitch these images together to form an image of the entire scene 50. Figure 5 The image sensor 9000 according to the embodiment shown may include an actuator 500 configured to move the radiation detector 100 to a plurality of positions. The actuator 500 may include a controller 600. The image sensor may include a collimator 200 that allows radiation to reach only an active area of ​​the radiation detector 100. The active area of ​​the radiation detector 100 is an area where the radiation detector 100 is sensitive to radiation. The actuator 500 may move the collimator 200 together with the radiation detector 100. The position may be determined by the controller 600.

[0057] Fig. 6A and Figure 6B Each schematically illustrates the movement of a radiation detector 100 (eg, 100A and 100B) relative to a radiation source 109 according to an embodiment. Fig. 6A and Figure 6B In the example of , only a portion of the image sensor 9000 having the first radiation detector 100A and the second radiation detector 100B is shown. The first radiation detector 100A and the second radiation detector 100B may be arranged on a bracket 107. The relative position of the first radiation detector 100A with respect to the second radiation detector 100B remains the same at multiple positions. When the first radiation detector 100A and the second radiation detector 100B are moved from one position to another position in the multiple positions, the relative position of the first radiation detector 100A with respect to the second radiation detector 100B may, but does not necessarily, remain the same. The first radiation detector 100A and the second radiation detector 100B may rotate around the first axis 501 relative to the radiation source 109. As shown Fig. 6A As shown in the example of , the first radiation detector 100A and the second radiation detector 100B are rotated from position 503A to position 503B relative to the radiation source 109 around the first axis 501. The first axis 501 may be parallel to the first planar surface 103A of the first radiation detector 100A and the second planar surface 103B of the second radiation detector 100B. The radiation source may be on the first axis 501. The first radiation detector 100A and the second radiation detector 100B may be rotated around the second axis 502 relative to the radiation source 109. The second axis 502 is different from the first axis 501. For example, the second axis 502 may be perpendicular to the first axis 501. Fig. 6AAs shown in the example of FIG. 5 , the first radiation detector 100A and the second radiation detector 100B may be rotated about the second axis 502 from a position 503A to a position 503C. The radiation source 109 may be on the second axis 502 .

[0058] like Figure 6B As shown in the example of FIG. 1 , the first radiation detector 100A and the second radiation detector 100B are translated from position 506A to position 506B along the first direction 504 relative to the radiation source 109. The first radiation detector 100A and the second radiation detector 100B can be translated along the second direction 505. The second direction 505 is different from the first direction 504. For example, the second direction 505 can be perpendicular to the first direction 504. Figure 6B As shown in the example of FIG. 5 , the first radiation detector 100A and the second radiation detector 100B may be translated from position 506A to position 506C along the second direction 505. The first direction 504 or the second direction 505 may be parallel to either the first planar surface 103A or the second planar surface 103B, or parallel to both, or not parallel to either. For example, the first direction 504 may be parallel to the first planar surface 103A, but not parallel to the second planar surface 103B.

[0059] Figure 7 The schematic diagram shows that the image sensor 9000 can capture images of multiple parts of the scene 50. Figure 7 In the example shown, the radiation detector 100 is moved to three positions A, B and C, for example, by using the actuator 500. The image sensor 9000 captures images 51A, 51B and 51C of multiple parts of the scene 50 at positions A, B and C, respectively. The image sensor 9000 can stitch the images 51A, 51B and 51C of the multiple parts into an image of the scene 50. The images 51A, 51B and 51C of the multiple parts can overlap each other for easy stitching. Each part of the scene 50 appears in at least one of the images captured when the radiation detector is in multiple positions. That is, when stitched together, the images of the multiple parts can cover the entire scene 50.

[0060] The radiation detectors 100 may be arranged in various ways in the image sensor 9000 . Fig. 8AAn arrangement according to an embodiment is schematically illustrated, in which radiation detectors 100 are arranged in staggered rows. For example, radiation detector 100A and radiation detector 100B are in the same row, aligned in the Y direction, and are of uniform size; radiation detector 100C and radiation detector 100D are in the same row, aligned in the Y direction, and are of uniform size. Radiation detector 100A and radiation detector 100B are staggered in the X direction relative to radiation detector 100C and radiation detector 100D. According to an embodiment, a distance X2 between two adjacent radiation detectors 100A and radiation detector 100B in the same row is greater than a width X1 (i.e., the X-direction dimension, i.e., the direction in which the row extends) of one radiation detector in the same row and is less than twice the width X1. Radiation detector 100A and radiation detector 100E are in the same column, aligned in the X direction, and are of uniform size; a distance Y2 between two adjacent radiation detectors 100A and radiation detector 100E in the same column is less than a width Y1 (i.e., the Y-direction dimension) of one radiation detector in the same column. This arrangement allows for Figure 7 The scene is imaged as shown, and an image of the scene can be obtained by stitching images of three portions of the scene taken at three positions spaced apart in the X direction.

[0061] Figure 8B Schematically shows another arrangement according to an embodiment, in which the radiation detectors 100 are arranged in a rectangular grid. For example, the radiation detectors 100 may include Fig. 8A The radiation detectors 100A, 100B, 100E and 100F are precisely arranged in a Fig. 8A The radiation detectors 100C, 100D, 100G or 100H in FIG. 100A and 100B are arranged in a manner that allows imaging of a scene by taking images of portions of the scene at six locations. For example, three locations spaced apart in the X direction, and another three locations spaced apart in the X direction and spaced apart from the first three locations in the Y direction.

[0062] Other arrangements are possible. For example, Figure 8C In the embodiment, the radiation detector 100 may span the entire width of the image sensor 9000 in the X direction, and the distance Y2 between two adjacent radiation detectors 100 is less than the width Y1 of one radiation detector. Assuming that the width of the radiation detector in the X direction is greater than the width of the scene in the X direction, the image of the scene can be obtained by stitching images of two parts of the scene taken at two positions spaced apart in the Y direction.

[0063] The radiation detector 100 as above has any suitable size and shape. Figure 7 ), at least some of the radiation detectors are rectangular in shape. According to an embodiment, Fig. 9As shown, at least some of the radiation detectors are hexagonal in shape.

[0064] Fig.10 A flow chart of a method according to an embodiment is schematically illustrated. In step 151, a first image of a first portion of a scene 50 is captured using radiation from a radiation source 109 by means of a first radiation detector 100A and a second radiation detector 100B, while the first radiation detector 100A and the second radiation detector 100B are located at a first position relative to the radiation source 109. In an optional step 152, the first radiation detector 100A and the second radiation detector 100B are moved from the first position to the second position. Moving the first radiation detector 100A and the second radiation detector 100B from the first position to the second position may be performed by rotating the first radiation detector 100A and the second radiation detector 100B around a first axis 501 relative to the radiation source 109, and may optionally be further performed by rotating the first radiation detector 100A and the second radiation detector 100B around a second axis 502 relative to the radiation source 109. Moving the first radiation detector 100A and the second radiation detector 100B from the first position to the second position may be performed by translating the first radiation detector 100A and the second radiation detector 100B along the first direction 504 relative to the radiation source 109, and may optionally be further performed by translating the first radiation detector 100A and the second radiation detector 100B along the second direction 505 relative to the radiation source 109. In step 153, a second image of a second portion of the scene 50 is captured by the first radiation detector 100A and the second radiation detector 100B using radiation from the radiation source 109, while the first radiation detector 100A and the second radiation detector 100B are located at the second position relative to the radiation source 109. In step 154, an image of the scene 50 is formed by stitching the first image and the second image.

[0065] The image sensor 9000 described above may be used in various systems as described below.

[0066] Fig.11 A system is schematically shown, which includes Figures 1 to 9 The image sensor 9000 is described in the embodiment of the present invention. The system can be used for medical imaging, such as chest radiation radiography, abdominal radiation radiography, etc. The system includes a radiation source 1201. The radiation emitted from the radiation source 1201 penetrates an object 1202 (e.g., a human body part such as a chest, a limb, an abdomen), is attenuated to varying degrees by the internal structure of the object 1202 (e.g., bones, muscles, fat, organs, etc.), and is projected to the image sensor 9000. The image sensor 9000 forms an image by detecting the intensity distribution of the radiation.

[0067] Fig.12A system is schematically shown, which includes Figures 1 to 9 The image sensor 9000 described in. The system can be used for medical imaging such as dental radiation radiography. The system includes a radiation source 1301. Radiation emitted from the radiation source 1301 penetrates an object 1302 that is part of the oral cavity of a mammal (e.g., a human). The object 1302 may include a maxillary bone, a maxillary bone, a tooth, a mandibular bone, or a tongue. The radiation is attenuated to varying degrees by different structures of the object 1302 and is projected onto the image sensor 9000. The image sensor 9000 forms an image by detecting the intensity distribution of the radiation. Teeth absorb more radiation than caries, infections, and periodontal ligaments. The radiation dose received by dental patients is usually very small (approximately 0.150 mSv for a full mouth series).

[0068] Fig.13 A cargo scanning or non-intrusive inspection (NII) system is schematically shown, which includes Figures 1 to 9 The image sensor 9000 described in the embodiment of the present invention can be used to inspect and identify cargo in a transportation system, such as containers, vehicles, ships, luggage, etc. The system includes a radiation source 1401. Radiation emitted from the radiation source 1401 can be backscattered from an object 1402 (e.g., a transportation container, a vehicle, a ship, etc.) and projected to the image sensor 9000. Different internal structures of the object 1402 can backscatter radiation differently. The image sensor 9000 forms an image by detecting the intensity distribution of the backscattered radiation and / or the energy of the backscattered radiation particles.

[0069] Fig.14 Another cargo scanning or non-intrusive inspection (NII) system is schematically shown, the system includes Figures 1 to 9 The image sensor 9000 described in the embodiment of the present invention can be used for luggage inspection at public transportation stations and airports. The system includes a radiation source 1501. Radiation emitted from the radiation source 1501 can penetrate a piece of luggage 1502, be attenuated to varying degrees by the contents of the luggage, and be projected to the image sensor 9000. The image sensor 9000 forms an image by detecting the intensity distribution of the transmitted radiation. The system can reveal the contents of the luggage and identify prohibited items on public transportation, such as firearms, narcotics, sharp objects, and flammable items.

[0070] Fig.15 A whole body scanner system is schematically shown, which includes Figures 1 to 9The image sensor 9000 described in. The whole body scanner system can detect objects on the human body for security inspection without physically removing clothing or making physical contact. The whole body scanner system is capable of detecting non-metallic objects. The whole body scanner system includes a radiation source 1601. Radiation emitted from the radiation source 1601 can be backscattered from the inspected person 1602 and objects thereon, and projected to the image sensor 9000. Objects and the human body can backscatter radiation differently. The image sensor 9000 forms an image by detecting the intensity distribution of the backscattered radiation. The image sensor 9000 and the radiation source 1601 can be configured to scan a person in a linear or rotational direction.

[0071] Fig.16 Schematic diagram of a radiation computed tomography (radiation CT) system. Radiation CT systems use computer-processed radiation to produce tomographic images (virtual "slices") of specific areas of the object being scanned. The tomographic images can be used for diagnostic and therapeutic purposes in various medical disciplines, or for flaw detection, failure analysis, metrology, assembly analysis, and reverse engineering. Radiation CT systems include Figures 1 to 9 The image sensor 9000 and the radiation source 1701 described in the figure can be configured to rotate synchronously along one or more circular or spiral paths.

[0072] Fig.17 An electron microscope is schematically shown. The electron microscope includes an electron source 1801 (also called an electron gun) configured to emit electrons. The electron source 1801 can have various emission mechanisms, such as a thermal ion, a photocathode, a cold emission, or a plasma source. The emitted electrons pass through an electron optical system 1803, which can be configured to shape, accelerate, or focus the electrons. The electrons then reach a sample 1802, and an image detector can form an image therefrom. The electron microscope may include, for example, Figures 1 to 9 The image sensor 9000 described in the invention is used to perform energy dispersive radiation spectroscopy (EDS). EDS is an analytical technique used for elemental analysis or chemical characterization of a sample. When electrons are incident on a sample, they cause the sample to emit characteristic radiation. The incident electrons can excite electrons in the inner shells of atoms in the sample, ejecting them from the shells while creating electron holes where the electrons were previously located. Electrons from the outer, higher energy shells then fill the holes, and the energy difference between the higher energy shell and the lower energy shell can be released in the form of radiation. The amount and energy of the radiation emitted from the sample can be measured by the image sensor 9000.

[0073] Here the image sensor 9000 may have other applications, such as radiation telescopes, mammography, industrial radiation defect detection, radiation microscopes or radiation microphotography, radiation casting inspection, radiation nondestructive testing, radiation weld inspection, radiation digital subtraction angiography, etc. It may be suitable to use the image sensor 9000 instead of a photographic plate, a photographic film, a PSP film, a radiation image intensifier, a scintillator, or another semiconductor radiation detector.

[0074] Fig.18A and Fig.18B Each shows a component diagram of the electronic system 121 according to an embodiment. The electronic system 121 may include a first voltage comparator 301 , a second voltage comparator 302 , a counter 320 , a switch 305 , an optional voltmeter 306 , and a controller 310 .

[0075] The first voltage comparator 301 is configured to compare the voltage of at least one electrical contact 119B with a first threshold. The first voltage comparator 301 may be configured to monitor the voltage directly, or to calculate the voltage by integrating the current flowing through the electrical contact 119B over a period of time. The first voltage comparator 301 may be controllably activated or deactivated by the controller 310. The first voltage comparator 301 may be a continuous comparator. That is, the first voltage comparator 301 may be configured to be continuously activated and continuously monitor the voltage. The first voltage comparator 301 may be a clocked comparator. The first threshold may be 1-5%, 5-10%, 10%-20%, 20-30%, 30-40% or 40-50% of the maximum voltage that an incident radiation particle can generate on the electrical contact 119B. The maximum voltage may depend on the energy of the incident radiation particle, the material of the radiation absorbing layer 110, and other factors. For example, the first threshold may be 50mV, 100mV, 150mV or 200mV.

[0076] The second voltage comparator 302 is configured to compare the voltage with a second threshold. The second voltage comparator 302 may be configured to monitor the voltage directly, or to calculate the voltage by integrating the current flowing through a diode or an electrical contact over a period of time. The second voltage comparator 302 may be a continuous comparator. The second voltage comparator 302 may be controllably enabled or disabled by the controller 310. When the second voltage comparator 302 is disabled, the power consumption of the second voltage comparator 302 may be less than 1%, less than 5%, less than 10%, or less than 20% of the power consumption when the second voltage comparator 302 is enabled. The absolute value of the second threshold is greater than the absolute value of the first threshold. As used herein, the term "absolute value" or "modulus" |x| of a real number x is the non-negative value of x regardless of its sign. That is, The second threshold value may be 200%-300% of the first threshold value. For example, the second threshold value may be 100mV, 150mV, 200mV, 250mV, or 300mV. The second voltage comparator 302 and the first voltage comparator 301 may be the same component. That is, the system 121 may have one voltage comparator that may compare the voltage to two different threshold values ​​at different times.

[0077] The first voltage comparator 301 or the second voltage comparator 302 may include one or more operational amplifiers or any other suitable circuits. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the system 121 to operate under a high flux of incident radiation particles. However, having a high speed usually comes at the expense of power consumption.

[0078] Counter 320 is configured to record at least a number of radiation particles incident on pixel 150 including electrical contact 119B. Counter 320 may be a software component (eg, a number stored in computer memory) or a hardware component (eg, 4017 IC and 7490 IC).

[0079] The controller 310 may be a hardware component such as a microcontroller and a microprocessor. The controller 310 is configured to start a time delay when the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value (e.g., the absolute value of the voltage increases from an absolute value below the first threshold value to a value equal to or exceeding the absolute value of the first threshold value) from the first voltage comparator 301. The absolute value is used here because the voltage can be negative or positive, depending on whether the cathode voltage or the anode voltage of the diode is used or which electrical contact is used. The controller 310 may be configured to keep the second voltage comparator 302, the counter 320, and any other circuits not required in the operation of the first voltage comparator 301 disabled before the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value. The time delay may expire before or after the voltage becomes stable (i.e., the rate of change of the voltage is approximately zero). The phrase "the rate of change is approximately zero" means that the time change is less than 0.1% / ns. The phrase "the rate of change is approximately non-zero" means that the time change of the voltage is at least 0.1% / ns.

[0080] The control 310 may be configured to start the second voltage comparator during the time delay (which includes the start and expiration). In one embodiment, the controller 310 is configured to start the second voltage comparator at the start of the time delay. The term "start" means to put a component into an operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by providing power, etc.). The term "disable" means to put a component into a non-operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by cutting off power, etc.). The operating state may have a higher power consumption than the non-operating state (e.g., 10 times higher, 100 times higher, 1000 times higher). The controller 310 itself may be disabled until the absolute value of the output voltage of the first voltage comparator 301 equals or exceeds the absolute value of the first threshold value before starting the controller 310.

[0081] If during the time delay, the second voltage comparator 302 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold, the controller 310 may be configured to increase at least one of the numbers recorded by the counter 320 by one.

[0082] The controller 310 may be configured to cause the optional voltmeter 306 to measure the voltage when the time delay expires. The controller 310 may be configured to cause the electrical contact 119B to be connected to electrical ground to reset the voltage and discharge any carriers accumulated on the electrical contact 119B. In one embodiment, the electrical contact 119B is connected to electrical ground after the time delay expires. In one embodiment, the electrical contact 119B is connected to electrical ground for a limited reset period. The controller 310 may cause the electrical contact 119B to be connected to electrical ground by controlling the switch 305. The switch may be a transistor, such as a field effect transistor (FET).

[0083] In one embodiment, system 121 has no analog filter networks (eg, RC networks). In one embodiment, system 121 has no analog circuits.

[0084] The voltmeter 306 may feed its measured voltage to the controller 310 as an analog or digital signal.

[0085] System 121 may include an integrator 309 electrically connected to electrical contact 119B, wherein the integrator is configured to collect current from electrical contact 119B. Integrator 309 may include a capacitor in the feedback path of an operational amplifier. An operational amplifier configured in this way is called a capacitive transimpedance amplifier (CTIA). CTIA has a high dynamic range by preventing operational amplifier saturation, and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. Carriers from electrical contact 119B accumulate on the capacitor over a period of time ("integration period"). After the integration period expires, the capacitor voltage is sampled by ADC 306 and then reset by a reset switch. Integrator 309 may include a capacitor directly connected to electrical contact 119B.

[0086] Fig.19 Schematically illustrates the temporal variation of the current flowing through the electrical contact 119B caused by the carriers generated by the radiation particles incident on the pixel 150 including the electrical contact 119B (upper curve) and the corresponding temporal variation of the voltage of the electrical contact 119B (lower curve). The voltage can be the integral of the current with respect to time. At time t 0 , the radiation particles hit pixel 150, carriers begin to be generated in pixel 150, current begins to flow through electrical contact 119B, and the absolute value of the voltage at electrical contact 119B begins to increase. At time t 1 , the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value V1, the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. 1 was previously deactivated at time t 1 The controller 310 is started. During TD1, the controller 310 starts the second voltage comparator 302. As used herein, the term "during" the time delay means the beginning and the expiration (i.e., the end) and any time in between. For example, the controller 310 may start the second voltage comparator 302 at the expiration of TD1. If during TD1, the second voltage comparator 302 determines that at time t 2 If the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold value V2, the controller 310 waits for the voltage to stabilize. e Stable, at this time all the carriers generated by the radiation particles drift out of the radiation absorption layer 110. s , time delay TD1 expires. At time t e At or after the time, the controller 310 causes the voltmeter 306 to digitize the voltage and determine in which bin the energy of the radiation particle falls. The controller 310 then increases the number recorded by the counter 320 corresponding to the bin by one. Fig. 9 In the example, time t s At time te That is, TD1 expires after all carriers generated by the radiation particles drift out of the radiation absorption layer 110. If the time t cannot be easily measured e , TD1 can be selected empirically to allow sufficient time to collect substantially all of the carriers generated by the radiation particle, but TD1 cannot be too long, otherwise there is a risk that another carrier generated by the incident radiation particle will be collected. That is, TD1 can be selected empirically so that time t s At time t e After that. Time t s Not necessarily at time t e Afterwards, since once V2 is reached, the controller 310 may ignore TD1 and wait for time t e Therefore, the rate of change of the difference between the voltage and the dark current contribution to the voltage is e is substantially zero. The controller 310 may be configured to 2 or any time in between, the second voltage comparator 302 is disabled.

[0087] At time t e The voltage of is proportional to the number of carriers generated by the irradiated particle, which is related to the energy of the irradiated particle. The controller 310 may be configured to use the voltmeter 306 to determine the energy of the irradiated particle.

[0088] After TD1 expires or is digitized by the voltmeter 306 (whichever is later), the controller connects the electrical contact 119B to the electrical ground 310 for a reset period RST to allow the accumulated carriers on the electrical contact 119B to flow to the ground and reset the voltage. After RST, the system 121 is ready to detect another incident radiation particle. If the first voltage comparator 301 is disabled, the controller 310 can activate it at any time before the expiration of RST. If the controller 310 is disabled, it can be activated before the expiration of RST.

[0089] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and the true scope and spirit of the invention should be determined by the claims herein.

Claims

1. An imaging system, comprising: Radiation sources; as well as Image sensor; wherein the image sensor comprises a first radiation detector and a second radiation detector, each of which comprises a planar surface, the planar surface being configured to receive radiation from the radiation source; wherein the planar surface of the first radiation detector is not parallel to the planar surface of the second radiation detector; wherein the image sensor is configured to capture an image of a scene by using the first radiation detector and the second radiation detector and utilizing the radiation; The radiation source is located outside the scene, and the radiation has passed through the scene before reaching at least one of the first radiation detector and the second radiation detector.

2. The imaging system of claim 1, wherein: The first radiation detector and the second radiation detector are disposed on a bracket having a curved surface, and the first radiation detector and the second radiation detector are arranged on the curved surface of the bracket.

3. The imaging system of claim 1, wherein: The radiation source emits a cone of radiation.

4. The imaging system of claim 1, wherein: The first radiation detector and the second radiation detector are configured to move to a plurality of positions relative to the radiation source, The image sensor is configured to capture images of multiple parts of the scene at the multiple positions respectively by using the first radiation detector and the second radiation detector and utilizing the radiation, and is configured to form an image of the scene by stitching the images of the multiple parts.

5. The imaging system of claim 4, wherein: The relative position of the first radiation detector with respect to the second radiation detector remains the same at the plurality of locations.

6. The imaging system of claim 4, wherein: The first radiation detector and the second radiation detector are configured to move relative to the radiation source by rotating about a first axis relative to the radiation source.

7. The imaging system of claim 6, wherein: The first axis is parallel to the planar surface of the first radiation detector and the planar surface of the second radiation detector.

8. The imaging system of claim 6, wherein: The first radiation detector and the second radiation detector are configured to move relative to the radiation source by rotating relative to the radiation source about a second axis, the second axis being different from the first axis.

9. The imaging system of claim 6, wherein: The radiation source is located on the first axis.

10. The imaging system of claim 4, wherein: The first radiation detector and the second radiation detector are configured to move relative to the radiation source by translating along a first direction relative to the radiation source.

11. The imaging system of claim 10, wherein: The first direction is parallel to the planar surface of the first radiation detector and the planar surface of the second radiation detector.

12. The imaging system of claim 10, wherein: The first direction is parallel to the planar surface of the first radiation detector but is not parallel to the planar surface of the second radiation detector.

13. The imaging system of claim 10, wherein: The first radiation detector and the second radiation detector are configured to move relative to the radiation source by translating relative to the radiation source along a second direction, the second direction being different from the first direction.

14. The imaging system of any one of claims 1 to 13, wherein: The first radiation detector and the second radiation detector each include a pixel array.

15. An imaging method comprising: capturing a first image of a first portion of a scene using radiation from a radiation source using a first radiation detector and a second radiation detector when the first radiation detector and the second radiation detector are located at a first position relative to the radiation source; capturing a second image of a second portion of the scene using the first radiation detector and the second radiation detector and utilizing the radiation from the radiation source when the first radiation detector and the second radiation detector are located at a second position relative to the radiation source; forming an image of the scene by stitching the first image and the second image; wherein the first radiation detector and the second radiation detector each include a planar surface, the planar surface being configured to receive radiation from a radiation source; wherein the planar surface of the first radiation detector is not parallel to the planar surface of the second radiation detector, The radiation source is located outside the scene, and the radiation has passed through the scene before reaching at least one of the first radiation detector and the second radiation detector.

Images