阅读说明：本技术 一种带有辐射检测器和准直器的图像传感器 (Image sensor with radiation detector and collimator ) 是由 曹培炎 刘雨润 于 2019-03-29 设计创作，主要内容包括：本文公开一种方法,其包括：通过以下方式将准直器(2000)与图像传感器(9000)的多个辐射检测器(100)对准：沿第一方向(799X)移动所述辐射检测器(100)；沿垂直于所述第一方向(799X)的第二方向(799Y)移动所述准直器(2000)；围绕垂直于所述第一方向(799X)和所述第二方向(799Y)的轴线(799Z)旋转所述准直器(2000)；其中,所述多个辐射检测器(100)被配置为分别在不同的图像捕获位置处捕获场景(50)的部分的图像(51A,51B和51C),并且通过拼接所述部分的所述图像(51A,51B和51C)来形成所述场景(50)的图像。(Disclosed herein is a method comprising: aligning a collimator (2000) with a plurality of radiation detectors (100) of an image sensor (9000) by: moving the radiation detector (100) in a first direction (799X); moving the collimator (2000) in a second direction (799Y) perpendicular to the first direction (799X); rotating the collimator (2000) about an axis (799Z) perpendicular to the first direction (799X) and the second direction (799Y); wherein the plurality of radiation detectors (100) are configured to capture images (51A, 51B and 51C) of portions of a scene (50) at different image capture positions, respectively, and to form an image of the scene (50) by stitching the images (51A, 51B and 51C) of the portions.)

1. A method, comprising:

aligning a collimator with a plurality of radiation detectors of an image sensor by:

moving the radiation detector in a first direction;

moving the collimator in a second direction perpendicular to the first direction;

rotating the collimator about an axis perpendicular to the first and second directions;

wherein the plurality of radiation detectors are configured to capture images of portions of a scene at different image capture locations, respectively, and form an image of the scene by stitching the images of the portions.

2. The method of claim 1, wherein the image capture locations are displaced from each other along the first direction.

3. The method of claim 1, wherein the collimator comprises a plurality of radiation transmissive regions and a radiation blocking region, and

wherein, when the collimator is aligned with the radiation detector, the radiation blocking region substantially blocks radiation that would otherwise be incident on a blind area of the image sensor, and the radiation transmitting region allows transmission of at least a portion of the radiation that would otherwise be incident on an active area of the image sensor.

4. The method of claim 2, further comprising moving the plurality of radiation detectors between the image capture locations.

5. The method of claim 1, wherein at least some of the plurality of radiation detectors are arranged in staggered rows.

6. The method of claim 1, wherein the active areas of the plurality of radiation detectors subdivide the scene at the image capture location.

7. The method of claim 1, wherein the images of portions of the scene at different ones of the image capture locations have a spatial overlap.

8. The method of claim 1, wherein the plurality of radiation detectors comprises a first radiation detector and a second radiation detector, the first and second radiation detectors each comprise a plane configured to receive radiation from a radiation source, and the plane of the first radiation detector and the plane of the second radiation detector are not parallel.

9. An image sensor, comprising:

a plurality of radiation detectors;

a collimator; and

an actuator configured to:

moving the radiation detector in a first direction;

moving the collimator in a second direction perpendicular to the first direction;

rotating the collimator about an axis perpendicular to the first and second directions;

wherein the plurality of radiation detectors are configured to capture images of portions of a scene at different image capture locations, respectively, and form an image of the scene by stitching the images of the portions.

10. The image sensor of claim 9, wherein the image capture locations are displaced from each other along the first direction.

11. The image sensor of claim 9 wherein the collimator comprises a plurality of radiation transmissive regions and a radiation blocking region, and

wherein, when the collimator is aligned with the radiation detector, the radiation blocking region substantially blocks radiation that would otherwise be incident on a blind area of the image sensor, and the radiation transmitting region allows transmission of at least a portion of the radiation that would otherwise be incident on an active area of the image sensor.

12. The image sensor of claim 9, wherein at least some of the plurality of radiation detectors are arranged in staggered rows.

13. The image sensor of claim 9 wherein the active areas of the plurality of radiation detectors subdivide the scene at the image capture location.

14. The image sensor of claim 9, wherein the images of portions of the scene at different ones of the image capture locations have a spatial overlap.

15. The image sensor of claim 9, wherein the plurality of radiation detectors comprises a first radiation detector and a second radiation detector, the first and second radiation detectors each comprise a plane configured to receive radiation from a radiation source, and the planes of the first and second radiation detectors are non-parallel.

16. The image sensor of claim 15 wherein the relative position of the first radiation detector with respect to the second radiation detector remains the same.

17. A radiation computed tomography system, comprising: the image sensor of claim 9, and a radiation source.

[ background of the invention ]

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

Radiation detectors are useful in many applications, one important application being imaging. Radiography is a radiographic technique that can be used to reveal the internal structure of objects of non-uniform composition and opacity, such as the human body.

Early radiation detectors used for imaging included photographic negative and photographic film. The photographic negative may be a glass plate with a photosensitive emulsion coating. Although photographic negatives are replaced by photographic film, they can still be used in special cases due to the excellent quality and extreme stability they provide. The photographic film may be a plastic film such as a strip or sheet having a photosensitive emulsion coating.

In the 80's of the 20 th century, photostimulable phosphor plates (PSP plates) began to become available. The PSP board contains a phosphor material having a color center in its crystal lattice. When the PSP plate is exposed to radiation, electrons excited by the radiation are trapped in the color center until they are stimulated by the laser beam scanned over the surface of the PSP plate. When the laser scans the PSP plate, the captured excited electrons emit light, which is collected by a photomultiplier tube, and the collected light is converted into a digital image. Compared with photographic negatives and photographic films, PSP plates are reusable.

Another type of radiation detector is a radiation image intensifier. The components of the radiation image intensifier are typically sealed in a vacuum. In contrast to photographic negatives, photographic films, and PSP plates, radiation image intensifiers can produce real-time images, i.e., do not require post-exposure processing to produce an image. The radiation first strikes the input phosphor (e.g., cesium iodide) and is converted to visible light. Visible light then strikes the photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes electron emission. The number of emitted electrons is proportional to the intensity of the incident radiation. The emitted electrons are projected through electron optics onto the output phosphor and cause the output phosphor to produce a visible light image.

The scintillator operates somewhat similarly to a radiation image intensifier 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, visible light is diffused and scattered in all directions, thereby reducing spatial resolution. Reducing the scintillator thickness helps to improve spatial resolution, but also reduces absorption of radiation. Therefore, the scintillator must achieve a compromise between absorption efficiency and resolution.

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

[ summary of the invention ]

Disclosed herein is a method comprising: aligning a collimator with a plurality of radiation detectors of an image sensor by: moving the radiation detector in a first direction; moving the collimator in a second direction perpendicular to the first direction; rotating the collimator about an axis perpendicular to the first and second directions; wherein the plurality of radiation detectors are configured to capture images of portions of a scene at different image capture locations, respectively, and form an image of the scene by stitching the images of the portions.

According to an embodiment, the image capturing positions are displaced from each other along the first direction.

According to an embodiment, the collimator comprises a plurality of radiation transmitting areas and a radiation blocking area, and wherein, when the collimator is aligned with the radiation detector, the radiation blocking area substantially blocks radiation that would otherwise be incident on a blind area of the image sensor, and the radiation transmitting area allows transmission of at least a portion of the radiation that would be incident on an active area of the image sensor.

According to an embodiment, the method further comprises moving the plurality of radiation detectors between the image capture locations.

According to an embodiment, at least some of the plurality of radiation detectors are arranged in staggered rows.

According to an embodiment, the active areas of the plurality of radiation detectors subdivide the scene at the image capture location.

According to an embodiment, the images of the portions of the scene at different said image capture locations have a spatial overlap.

According to an embodiment, the plurality of radiation detectors includes a first radiation detector and a second radiation detector, the first and second radiation detectors each include a plane configured to receive radiation from a radiation source, and the planes of the first and second radiation detectors are non-parallel.

Disclosed herein is an image sensor, comprising: a plurality of radiation detectors; a collimator; and an actuator configured to: moving the radiation detector in a first direction; moving the collimator in a second direction perpendicular to the first direction; rotating the collimator about an axis perpendicular to the first and second directions; wherein the plurality of radiation detectors are configured to capture images of portions of a scene at different image capture locations, respectively, and form an image of the scene by stitching the images of the portions.

According to an embodiment, the image capturing positions are displaced from each other along the first direction.

According to an embodiment, the collimator comprises a plurality of radiation transmitting areas and a radiation blocking area, and wherein, when the collimator is aligned with the radiation detector, the radiation blocking area substantially blocks radiation that would otherwise be incident on a blind area of the image sensor, and the radiation transmitting area allows transmission of at least a portion of the radiation that would be incident on an active area of the image sensor.

According to an embodiment, at least some of the plurality of radiation detectors are arranged in staggered rows.

According to an embodiment, the active areas of the plurality of radiation detectors subdivide the scene at the image capture location.

According to an embodiment, the images of the portions of the scene at different said image capture locations have a spatial overlap.

According to an embodiment, the plurality of radiation detectors includes a first radiation detector and a second radiation detector, the first and second radiation detectors each include a plane configured to receive radiation from a radiation source, and the planes of the first and second radiation detectors are non-parallel.

According to an embodiment, the relative position of the first radiation detector with respect to the second radiation detector remains the same.

Also disclosed herein is a radiation computed tomography system comprising: the image sensor and a radiation source.

[ description of the drawings ]

Fig. 1 schematically shows a cross-sectional view of a part of an image sensor according to an embodiment.

Fig. 2A schematically shows a cross-sectional view of a radiation detector according to an embodiment.

Fig. 2B schematically shows a detailed cross-sectional view of the radiation detector according to an embodiment.

Fig. 2C schematically shows an alternative detailed cross-sectional view of the radiation detector according to an embodiment.

Fig. 3 schematically illustrates that the radiation detector may have an array of pixels according to an embodiment.

Fig. 4A schematically illustrates a top view of a package including a radiation detector and a Printed Circuit Board (PCB).

FIG. 4B schematically shows a cross-sectional view of the detector, wherein the multiple packages of FIG. 4A are mounted to another PCB.

Fig. 5 schematically shows a movement of a radiation detector of the image sensor relative to a radiation source according to an embodiment.

Fig. 6 schematically shows one collimator of the image sensor according to an embodiment.

Fig. 7 schematically shows a functional block diagram of the image sensor according to an embodiment.

FIG. 8 schematically illustrates that an image of an object may be formed by stitching images of multiple different portions of the object, according to one embodiment.

Fig. 9A to 9D schematically show an arrangement of the radiation detector in the image sensor according to an embodiment.

Fig. 10 schematically shows a flow chart of a method of calibrating the device according to an embodiment.

Fig. 11A and 11B each show a component diagram of an electronic system of the radiation detector in fig. 2A, 2B, and 2C, according to an embodiment.

Fig. 12 schematically shows a temporal variation of the current (upper curve) and a corresponding temporal variation of the electrode voltage (lower curve) caused by carriers generated by radiation particles incident on the radiation absorbing layer, flowing through the electrodes of the diode or through the electrical contacts of the resistor of the radiation absorbing layer exposed to the radiation, according to an embodiment.

[ detailed description ] embodiments

Fig. 1 schematically illustrates 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 100 (e.g., a first radiation detector 100A, a second radiation detector 100B). The radiation detectors 100 can be spaced apart from each other in the image sensor 9000. The image sensor 9000 may have a support 107. The support 107 may be provided with a curved surface 102. The plurality of radiation detectors 100 may be arranged on the support 107, for example, on the curved surface 102 as shown in the example of fig. 1. The first radiation detector 100A may have a first planar surface 103A configured to receive radiation from the radiation source 109. The second radiation detector 100B may have a second planar surface 103B configured to receive the radiation from the radiation source 109. The first planar surface 103A and the second planar surface 103B may be non-parallel. The radiation from the radiation source 109 may have passed through a scene 50 (e.g., a portion of a human body) before reaching the first radiation detector 100A or the second radiation detector 100B.

Fig. 2A schematically shows a cross-sectional view of one radiation detector 100 of the image sensor 9000 according to an embodiment. The radiation detector 100 may include a radiation absorbing layer 110 and an electronics layer 120 (e.g., ASIC) for processing or analyzing electrical signals generated in the radiation absorbing layer 110 by incident radiation. In an embodiment, the radiation detector 100 does not comprise a scintillator. The radiation absorbing layer 110 may comprise a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof. The semiconductor may have a high mass attenuation coefficient for radiation generated by the radiation source 109.

As shown in the detailed cross-sectional view of the radiation detector 100 in fig. 2B, the radiation absorbing layer 110 according to an embodiment may comprise one or more diodes (e.g., p-i-n or p-n) consisting of one or more discrete regions 114 of first and second doped regions 111, 113. The second doped region 113 may be separated from the first doped region 111 by an optional intrinsic region 112. The discrete regions 114 are separated from each other by the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 have opposite type doping (e.g., the first doped region 111 is p-type and the second doped region 113 is n-type, or the first doped region 111 is n-type and the second doped region 113 is p-type). In the example of fig. 2B, each discrete region 114 of the second doped region 113 constitutes a diode together with the first doped region 111 and the optional intrinsic region 112. That is, in the example of fig. 2B, the radiation absorption layer 110 includes a plurality of diodes having the first doped region 111 as a common electrode. The first doped region 111 may also have discrete portions.

When a radiation particle strikes the radiation absorbing layer 110, which includes a diode, the radiation particle may be absorbed and generate one or more carriers by several mechanisms. One radiation particle can generate 10 to 100000 carriers. The carriers may drift under the electric field towards the electrode of one of the diodes. The electric field may be an external electric field. The electrical contacts 119B may comprise discrete portions, each of which is in electrical contact with the discrete region 114. In an embodiment, the carriers may drift in different directions such that the carriers generated by a single radiating particle are substantially not 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 one of the discrete regions 114 that is different from the rest of the carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete regions 114 are substantially not shared by the other of the discrete regions 114. One pixel 150 associated with one discrete region 114 may be a surrounding region of the discrete region 114 to which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by the radiation particles incident therein 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 out of the pixel.

As shown in the alternate detailed cross-sectional view of the radiation detector 100 in FIG. 2C, the radiation absorbing layer 110 according to embodiments may include resistors of semiconductor material (such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof) but not diodes. The semiconductor may have a high mass attenuation coefficient for radiation generated by the radiation source 109.

When a radiation particle strikes the radiation absorbing layer 110, which includes a resistor but does not include a diode, the radiation particle may be absorbed and generate one or more carriers by several mechanisms. One radiation particle can generate 10 to 100000 carriers. The carriers may drift under the electric field toward the electrical contact 119A and the electrical contact 119B. The electric field may be an external electric field. The electrical contacts 119B include discrete portions. In an embodiment, the carriers may drift in different directions, such that the carriers generated by a single radiating particle are substantially not 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 discrete portions of a different group than the rest of the carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete portions of electrical contact 119B are substantially not shared by the other discrete portion of electrical contact 119B. One pixel 150 associated with one of the discrete portions of the electrical contact 119B may be a surrounding region of the discrete portion to which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by the radiation particles incident therein flow to 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 carriers flow out of the pixel.

The electronics layer 120 may include an electronic system 121, the electronic system 121 being adapted to process or interpret 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 memory. The electronic system 121 may include components that are common to the pixels or components that are dedicated to individual pixels. For example, the electronic system 121 may include an amplifier dedicated to each of the pixels and a microprocessor shared among all the pixels. The electronic system 121 may be electrically connected to the pixels through vias 131. The space between the vias may be filled with a filler material 130, which may increase the mechanical stability of the connection of the electronic device layer 120 to the radiation absorbing layer 110. Other bonding techniques are possible to connect the electronic system 121 to the pixels without using vias.

Fig. 3 schematically shows that the radiation detector 100 may have an array of the pixels 150. The array may be a rectangular array, a honeycomb array, a hexagonal array, or any other suitable array. Each of the pixels 150 may be configured to detect a radiation particle incident thereon, measure an energy of the radiation particle, or both. For example, each pixel 150 may be configured to count the number of radiation particles incident thereon over a period of time that have energy falling in multiple bins. All of the pixels 150 may be configured to count the number of radiation particles in the plurality of energy bins incident thereon over the same period of time. Each pixel 150 may have its own analog-to-digital converter (ADC) 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 of the pixels 150 may be configured to measure its dark current, e.g. before or at the same time as each radiation particle is incident thereon. Each of the pixels 150 may be configured to subtract the contribution of the dark current from the energy of the radiation particle incident thereon. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 measures an incident radiation particle, another pixel 150 may be waiting for a radiation particle to arrive. The pixels 150 may, but need not, be individually addressable.

Fig. 4A schematically illustrates that one or more radiation detectors 100 may be mounted on a Printed Circuit Board (PCB) 400. The term "PCB" as used herein is not limited to a particular material. For example, the PCB may include a semiconductor. For clarity, wiring between the radiation detector 100 and the PCB 400 is not shown. The PCB 400 and the radiation detector 100 mounted thereon may be referred to as a package 200. The PCB 400 may have areas not covered by the radiation detector 100 (e.g., areas for receiving solder wires 410). Each of the radiation detectors 100 may have an active area 190, which is where the pixel 150 is located. Each of the radiation detectors 100 may have a peripheral region 195 near an edge. The peripheral region 195 has no pixels and no radiation particles incident on the peripheral region 195 are detected.

Fig. 4B schematically illustrates that the image sensor 9000 may have a system PCB 450 on which a plurality of packages 200 are mounted. The image sensor 9000 may comprise one or more of such system PCBs 450. The electrical connection between the PCB 400 and the system PCB 450 in the package 200 may be accomplished by solder wires 410. To accommodate the solder lines 410 on the PCB 400, the PCB 400 has a region 405 that is not covered by the radiation detector 100. To accommodate the solder lines 410 on the system PCB 450, there is a gap between the packages 200. The active areas 190 of the radiation detector 100 in the image sensor 9000 are collectively referred to as the active area of the image sensor 9000. Other regions of the image sensor 9000 into which radiation incident thereon cannot be detected by the image sensor 9000, such as the peripheral regions 195, regions 405, or gaps between packages 200, are collectively referred to as blind regions of the image sensor 9000. The radiation detector 100A and the radiation detector 100B as shown in fig. 1 may be embodiments of the radiation detector 100 and mounted on respective PCBs 400 in a similar manner as shown in fig. 4A, and the support 107 may be part of the PCB 400 in one embodiment and part of the system PCB 450 in another embodiment.

Fig. 5 schematically illustrates movement of the radiation detector 100 (e.g., 100A and 100B) relative to the radiation source 109, in accordance with an embodiment. In the example of fig. 5, only a portion of an image sensor 9000 having a first radiation detector 100A and a second radiation detector 100B is shown. The first radiation detector 100A and the second radiation detector 100B may be arranged on the support 107. The relative position of the first radiation detector 100A with respect to the second radiation detector 100B remains the same at a plurality of positions. The relative position of the first radiation detector 100A with respect to the second radiation detector 100B may, but need not, remain the same when the first radiation detector 100A and the second radiation detector 100B are moved from one position to another of the plurality of positions.

As shown in the example of fig. 5, the first radiation detector 100A and the second radiation detector 100B are translated in a first direction 504 from a position 506A to a position 506B with respect to the radiation source 109. The first radiation detector 100A and the second radiation detector 100B are translatable along a second direction 505. The second direction 505 is different from the first direction 504. For example, the second direction 505 may be perpendicular to the first direction 504. As shown in the example of fig. 5, the first radiation detector 100A and the second radiation detector 100B may be translated in a second direction 505 from a position 506A to a position 506C. The first direction 504 or the second direction 505 may be parallel to either of the first planar surface 103A and the second planar surface 103B, or to both, or not parallel to either of the two. For example, the first direction 504 may be parallel to the first planar surface 103A, but not parallel to the second planar surface 103B.

Fig. 6 schematically illustrates that the image sensor 9000 may comprise a collimator 2000. According to an embodiment, the collimator 2000 comprises a plurality of radiation transmissive regions 2002 and one radiation blocking region 2004. The radiation blocking regions 2004 substantially block radiation that would otherwise be incident on the blind regions 9004 of the image sensor 9000, and the radiation transmissive regions 2002 allow at least a portion of the radiation incident on the active regions 9002 of the image sensor 9000 to pass through. The radiation transmissive region 2002 may be a hole through the collimator 2000, and the rest of the collimator 2000 may serve as the radiation blocking region 2004. The collimator 2000 may be arranged close to the radiation detector 100 or remote from the radiation detector 100. For example, the scene 50 may be between the collimator 2000 and the radiation detector 100. The radiation transmissive regions 2002 can have different sizes or locations than the active regions 9002.

The relative positions of the collimator 2000 and the radiation detector 100 may not be fixed. For example, if the radiation from the radiation source 109 is not parallel rays, it may be desirable for the collimator 2000 and the radiation detector 100 to have different relative positions when the image sensor 9000 is located at different positions relative to the radiation source 109 to align the radiation transmissive region 2002 with the active region 9002.

In an embodiment, the radiation detector 100 of the image sensor 9000 is movable to a plurality of positions ("image capture positions") relative to the radiation source 109. The image sensor 9000 may capture images of portions of the scene 50 from the radiation source 109 at the plurality of locations, respectively, using the radiation detector 100 and with the radiation. The image sensor 9000 can stitch these images to form an image of the entire scene 50. The image sensor 9000 according to an embodiment as shown in fig. 7 may comprise an actuator 500, the actuator 500 being configured to move the radiation detector 100 to a plurality of positions. The actuator 500 may include a controller 600. The actuator 500 may move the radiation detector 100 to change its position relative to the collimator 2000 and may move the collimator 2000 to change its position and orientation relative to the radiation detector 100. The position and orientation may be determined by the controller 600. After the radiation detector 100 is moved to one of the image capturing positions, the collimator 2000 and the radiation detector 100 may be aligned. For example, as shown in fig. 6, the collimator 2000 and the radiation detector 100 may be aligned by moving the radiation detector 100 in a first direction 799X and moving the collimator 2000 in a second direction 799Y perpendicular to the first direction 799X. Rotating the collimator 2000 about an axis 799Z perpendicular to the first direction 799X and the second direction 799Y. The image capture positions may be shifted from each other along the first direction 799X. In an embodiment, during the operation of capturing an image of a scene, the locations may be selected such that the active area of the image sensor 9000 collectively subdivides the entire scene at multiple locations.

Fig. 8 schematically illustrates that the image sensor 9000 is capable of capturing an image of a portion of the scene 50. In the example shown in fig. 8, the radiation detector 100 is moved to three positions A, B and C, for example, by using an actuator 500. The image sensor 9000 captures images 51A, 51B and 51C of portions of the scene 50 at the image capture locations A, B and C, respectively. The image sensor 9000 can stitch the images 51A, 51B, and 51C of the portions into an image of the scene 50. These partial images 51A, 51B and 51C may be superimposed on each other to facilitate stitching. Each portion of the scene 50 appears at least in one of the images captured when the radiation detector is in a plurality of positions. That is, when stitched together, the images of the portions may cover the entire scene 50.

The radiation detector 100 may be arranged in the image sensor 9000 in various ways. Fig. 9A schematically shows an arrangement according to an embodiment, wherein the radiation detectors 100 are arranged in staggered rows. For example, the radiation detector 100J and the radiation detector 100K are in the same row, aligned in the Y direction, and uniform in size; the radiation detector 100C and the radiation detector 100D are aligned in the Y direction in the same row, and are uniform in size. The radiation detectors 100J and 100K are interleaved in the X direction with respect to the radiation detectors 100C and 100D. According to an embodiment, the distance X2 between two adjacent radiation detectors 100J and 100K in the same row is larger than the width X1 (i.e. the X-direction dimension, i.e. the direction of extension of the row) of one radiation detector in the same row and smaller than twice the width X1. The radiation detector 100J and the radiation detector 100E are in the same column, aligned in the X direction, and uniform in size; the distance Y2 between two adjacent radiation detectors 100J and 100E in the same column is smaller than the width Y1 (i.e., the Y-direction dimension) of one radiation detector in the same column.

Fig. 9B schematically shows another arrangement according to an embodiment, wherein the radiation detectors 100 are arranged in a rectangular grid. For example, the radiation detector 100 may include precisely aligned radiation detectors 100J, 100K, 100E, and 100F as in fig. 9A, without the radiation detectors 100C, 100D, 100G, or 100H of fig. 9A.

Other arrangements are also possible. For example, in fig. 9C, the radiation detectors 100 may span the entire width of the image sensor 9000 in the X-direction, with the distance Y2 between two adjacent radiation detectors 100 being 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, an image of the scene may be obtained by stitching images of two portions of the scene captured at two locations spaced apart in the Y-direction.

According to an embodiment, the radiation source 109 and the image sensor 9000 may be jointly rotatable around the object around a plurality of axes.

The radiation detector 100 in the image sensor 9000 can have any suitable size and shape. According to an embodiment (e.g., in fig. 9A-9C), at least some of the radiation detectors 100 are rectangular in shape. According to an embodiment, at least some of the radiation detectors are hexagonal in shape, as shown in fig. 9D. In such a radiation detector, the radiation detector and the corresponding collimator aligned therewith may have the same shape.

Fig. 10 schematically shows a flow chart of a method for aligning the collimator 2000 and the radiation detector 100 according to an embodiment. In step 1102, the radiation detector 100 is moved along a first direction (e.g., the direction 799X in FIG. 6). The first direction may be in a plane in which the radiation detector 100 is arranged. In step 1104, the collimator 2000 is moved in a second direction (e.g., the direction 799Y in fig. 6) perpendicular to the first direction. The second direction may be in a plane in which the radiation detector 100 is arranged. In step 1106, the collimator 2000 is rotated about an axis (e.g., the axis 799Z in fig. 6) perpendicular to the first and second directions. In optional step 1108, the radiation detector 100 is moved relative to the radiation source 109, for example, to one of the image capture positions.

Fig. 11A and 11B each show a component diagram of an 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, a voltmeter 306, and a controller 310.

The first voltage comparator 301 is configured to compare the voltage of the electrode of the diode 300 with a first threshold value. The diode may be one formed by the first doped region 111, one of the discrete regions 114 of the second doped region 113 and the optional intrinsic region 112. Alternatively, the first voltage comparator 301 is configured to compare the voltage of the electrical contact (e.g., a discrete portion of the electrical contact 119B) to 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 diode or electrical contact 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 enabled and monitor the voltage. The first voltage comparator 301 configured as a successive comparator reduces the chance that the system 121 misses the signal generated by the incident radiation particles. Said first voltage comparator 301 configured as a continuous comparator is particularly suitable when the intensity of the incident radiation is relatively high. The first voltage comparator 301 may be a clocked comparator, which has the advantage of lower power consumption. The first voltage comparator 301, which is configured as a clocked comparator, may cause the system 121 to miss signals generated by some incident radiation particles. When the intensity of the incident radiation is low, the chance of missing an incident radiation particle is low, because the time interval between two consecutive radiation particles is relatively long. Therefore, the first voltage comparator 301 configured as a clocked comparator is particularly suitable when the incident radiation intensity is relatively low. The first threshold may be 5-10%, 10-20%, 20-30%, 30-40% or 40-50% of the maximum voltage of one incident radiation particle generated in the diode or the resistor. The maximum voltage may depend on the energy of the incident radiation particles (i.e., the wavelength of the incident radiation), the material of the radiation absorbing layer 110, and other factors. For example, the first threshold may be 50mV, 100mV, 150mV, or 200 mV.

The second voltage comparator 302 is configured to compare the voltage to 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 the diode or the 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 activated or deactivated 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 a non-negative value of x regardless of its sign. That is to say that the first and second electrodes,the second threshold may be 200% -300% of the first threshold. For example,the second threshold may be 100mV, 150mV, 200mV, 250mV, or 300 mV. 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 a voltage to two different thresholds at different times.

The first voltage comparator 301 or the second voltage comparator 302 may include one or more operational amplifiers or any other suitable circuitry. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the system 121 to operate with a high flux of incident radiation particles. However, having high speed is usually at the cost of power consumption.

The counter 320 is configured to record at least a number of radiation particles incident on the pixel 150 including the electrical contact 119B. The counter 320 may be a software component (e.g., a number stored in a computer memory) or a hardware component (e.g., 4017IC and 7490 IC).

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

The control 310 may be configured to start the second voltage comparator during the time delay (which includes a start and an expiration). In an embodiment, the controller 310 is configured to start the second voltage comparator at the beginning of the time delay. The term "activate" means to bring a component into an operational state (e.g., by sending a signal such as a voltage pulse or logic level, by providing power, etc.). The term "disable" means to bring a component into a non-operational state (e.g., by sending a signal such as a voltage pulse or logic level, by cutting power, etc.). The operating state may have a higher power consumption (e.g., 10 times higher, 100 times higher, 1000 times higher) than the non-operating state. The controller 310 itself may be deactivated 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 to activate the controller 310.

If, during the time delay, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold, the controller 310 may be configured to increment the number recorded by the counter 320 by one.

The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay. The controller 310 may be configured to connect the electrodes to electrical ground to reset the voltage and discharge any carriers accumulated on the electrodes. In an embodiment, the electrode is connected to electrical ground after the time delay expires. In an embodiment, the electrode is connected to electrical ground for a limited reset period. The controller 310 may connect the electrode to the electrical ground by controlling the switch 305. The switch may be a transistor such as a Field Effect Transistor (FET).

In an embodiment, the system 121 does not have an analog filter network (e.g., an RC network). In an embodiment, the system 121 has no analog circuitry.

The voltmeter 306 can feed the voltage it measures to the controller 310 as an analog or digital signal.

The system 121 may include an integrator 309 electrically connected to the electrode or electrical contact of the diode 300, wherein the integrator is configured to collect carriers from the electrode. The integrator may comprise a capacitor in the feedback path of the amplifier. An amplifier so configured is referred to as a capacitive transimpedance amplifier (CTIA). CTIA has a high dynamic range by preventing the amplifier from saturating and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. The carriers from the electrodes are present over a period of time ("integration period") (e.g., at time t, as shown in fig. 12)₀And time t₁In between, or at time t₁And time t₂In between) is accumulated on the capacitor. After the integration period expires, the capacitor voltage is sampled and then reset by a reset switch. The integrator may comprise a capacitor directly connected to the electrodes.

Fig. 12 schematically shows the temporal variation of the current (upper curve) and the corresponding temporal variation of the voltage of the electrode (lower curve) caused by the carriers generated by the radiation particles incident on the diode or the resistor, flowing through the electrode. The voltage may be an integral of the current with respect to time. At time t₀The radiation particles hit the diode or the resistor, carriers start to be generated in the diode or the resistor, current starts to flow through the electrodes of the diode or the resistor, and the absolute value of the voltage of the electrodes or the electrical contacts starts to increase. At time t₁The first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1, the controller 310 activates a time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 when the TD1 starts. If the controller 310 is at time t₁Previously deactivated, at time t₁The controller 310 is activated. During the TD1, the controller 310 activates the second voltage comparator 302. The term "during" a time delay as used herein means any time between the beginning and expiration (i.e., ending) and in the middle. For example, the controller 310The second voltage comparator 302 may be enabled upon expiration of the TD 1. If during the TD1, the second voltage comparator 302 determines at time t₂The absolute value of the voltage equals or exceeds the absolute value of the second threshold, the controller 310 increases the number recorded by the counter 320 by one. At time t_eAll carriers generated by the radiation particles drift out of the radiation absorbing layer 110. At time t_sThe time delay TD1 expires. In the example of FIG. 12, time t_sAt time t_eThen; that is, TD1 expires after all carriers generated by the radiation particles drift out of the radiation absorbing layer 110. At time t_sThe rate of change of voltage is therefore substantially zero. The controller 310 may be configured to expire at TD1 or at time t₂Or any time in between, disables the second voltage comparator 302.

The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay TD 1. In an embodiment, the controller 310 causes the voltmeter 306 to measure the voltage after the time delay TD1 expires and the rate of change of the voltage becomes substantially zero. The voltage at this time is proportional to the number of carriers generated by the radiation particles, which is related to the energy of the radiation particles. The controller 310 may be configured to determine the energy of the radiation particles based on the voltage measured by the voltmeter 306. One way to determine the energy is by binning the voltage. The counter 320 may have a sub-counter for each bin. When the controller 310 determines that the energy of the radiation particle falls into one bin, the controller 310 may increase the number recorded in the sub-counter of the bin by one. Thus, the system 121 is able to detect radiation images and to resolve the radiation energy of each radiation particle.

After the expiration of TD1, the controller connects the electrode to electrical ground for a reset period RST to allow the carriers accumulated on the electrode to flow to ground and reset the voltage. After RST, the system 121 is ready to detect another incident radiation particle. Implicitly, in the example of fig. 12, the rate of incident radiation particles that the system 121 can handle is limited to 1/(TD1+ RST). If the first voltage comparator 301 has been disabled, the controller 310 may enable it at any time prior to the expiration of RST. If the controller 310 has been deactivated, it may be activated before the RST expires.

The image sensor 9000 as described above can be used for different detection systems, such as, but not limited to, medical imaging such as dental radiography; a cargo scanning or non-intrusive inspection (NII) system that may be used to inspect and identify cargo in a transportation system, such as containers, vehicles, ships, baggage, etc.; a whole-body scanner system; a radiation computed tomography (radiation CT) system; an electron microscope; a system for performing energy dispersive radiation spectroscopy (EDS).

The image sensor 9000 may also have other applications, such as radiation telescopes, mammography, industrial radiation defect detection, radiation microscopy or radiation microscopy, radiation casting inspection, radiation non-destructive inspection, radiation welding inspection, radiation digital subtraction angiography, and the like. The image sensor 9000 is used in place of a photographic negative, photographic film, PSP film, radiation image intensifier, scintillator, or another semiconductor radiation detector.

While 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 purposes of illustration and not limitation, and their true scope and spirit should be determined by the claims herein.