Imaging system with image sensor with multiple radiation detectors

Abstract

An imaging system is disclosed herein, the imaging system comprising: an image sensor comprising: a system printed circuit board (system PCB); M group printed circuit boards (group PCB(i), i = 1,..., M) mounted on a mounting surface of the system PCB; and for i = 1,..., M, Ni radiation detectors mounted on the group PCB(i), wherein M and Ni are integers greater than 1, wherein i = 1,..., M, wherein the image sensor is configured to scan a scene in a scan direction, and wherein for each group PCB(i), there is no plane that (A) is parallel to a normal direction of the mounting surface of the system PCB, (B) is parallel to the scan direction, (C) divides all active areas of the Ni radiation detectors into two groups of active areas, and (D) does not intersect any active area of all active areas of the Ni radiation detectors.

Description

BACKGROUND

[0001] A radiation detector is a device that measures properties of radiation. Examples of properties can include intensity, phase, and spatial distribution of polarization of the radiation. The radiation can be radiation that has interacted with an object. For example, the radiation measured by the radiation detector can be radiation that has penetrated an object. The radiation can be electromagnetic radiation, such as infrared light, visible light, ultraviolet light, X-rays, or gamma rays. The radiation can also be other types, such as alpha and beta rays. An imaging system can include an image sensor with multiple radiation detectors. SUMMARY

[0002] Disclosed herein is an imaging system comprising: an image sensor comprising: a system printed circuit board (system PCB); M group printed circuit boards (group PCB(i), i = 1,..., M) mounted on a mounting surface of the system PCB; and for i = 1,..., M, Ni radiation detectors mounted on the group PCB(i), wherein M and Ni are integers larger than 1, wherein i = 1,..., M, wherein the image sensor is configured to scan a scene in a scan direction, and wherein for each group PCB(i), there is no plane that (A) is parallel to a normal direction of the mounting surface of the system PCB, (B) is parallel to the scan direction, (C) divides all active areas of the Ni radiation detectors into two groups of active areas, and (D) does not intersect any active area of all active areas of the Ni radiation detectors.

[0003] In an aspect, all Ni are the same, wherein i = 1,..., M.

[0004] In an aspect, the M group PCBs and the system PCB comprise a semiconductor.

[0005] In an aspect, each of the M group PCBs has a rectangular shape.

[0006] In an aspect, the M group PCBs are arranged as a row extending in the scan direction.

[0007] In an aspect, all active areas of all the Ni radiation detectors overlap in the normal direction, wherein i = 1,..., M, such that all active areas of all the Ni radiation detectors form a piece of active area in the normal direction, wherein i = 1,..., M.

[0008] In an aspect, the imaging system further comprises a radiation source configured to generate a radiation beam whose boundaries do not intersect any of all active areas of the Ni radiation detectors when the image sensor scans the scene, where i = 1,..., M.

[0009] In an aspect, the radiation of the radiation beam is aimed at a point of all active areas of the Ni radiation detectors, where i = 1,..., M.

[0010] In an aspect, the imaging system further comprises a mask that allows some radiation of the radiation source to pass through the mask, thereby resulting in the radiation beam.

[0011] In an aspect, for each group PCB(i), no two active areas of the Ni radiation detectors overlap in the normal direction, where i = 1,..., M.

[0012] In an aspect, for each group PCB(i), (A) the Ni radiation detectors of the group PCB(i) overlap in the normal direction, thereby making a piece of active area in the normal direction out of all active areas of the Ni radiation detectors, and (B) a plane parallel to the normal direction and perpendicular to the scan direction intersects all active areas of the Ni radiation detectors, where i = 1,..., M.

[0013] In an aspect, the M groups of PCBs overlap in the normal direction, thereby making a piece of printed circuit board in the normal direction out of all the M groups of PCBs, and a plane parallel to the normal direction and parallel to the scan direction intersects all the M groups of PCBs.

[0014] In an aspect, the imaging system further comprises an input / output port on each of the M groups of PCBs.

[0015] In an aspect, an input / output port on a first group of PCBs of the M groups of PCBs is sandwiched between the first group of PCBs and a second group of PCBs of the M groups of PCBs.

[0016] In an aspect, an input / output port on a first group of PCBs of the M groups of PCBs overlaps in the normal direction with an active area on a second group of PCBs of the M groups of PCBs.

[0017] In an aspect, for each group PCB(i), each of the Ni radiation detectors on the group PCB(i) comprises: (A) a radiation-absorbing layer and (B) an electronics layer comprising a plurality of application-specific integrated circuits (ASICs), where i = 1,..., M.

[0018] In an aspect, the radiation absorbing layer and the electronics layer are electrically connected to each other by a via.

[0019] In an aspect, the radiation absorbing layer comprises a plurality of diodes.

[0020] In an aspect, the radiation absorbing layer comprises a semiconductor.

[0021] In an aspect, the electronics layer comprises an electronic system configured to process a signal generated by radiation incident on the radiation absorbing layer. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A radiation detector according to an embodiment is schematically illustrated.

[0023] Figure 2A and Figure 2B A simplified diagram of a radiation detector according to an embodiment is schematically illustrated.

[0024] Figure 2C A detailed cross-sectional view of a radiation detector according to an embodiment is schematically illustrated.

[0025] Figure 2D A detailed cross-sectional view of a radiation detector according to an alternative embodiment is schematically illustrated.

[0026] Figures 3A to 3C A radiation detector package comprising a plurality of radiation detectors according to different embodiments is schematically illustrated.

[0027] Figure 4A and Figure 4B An image sensor according to an embodiment comprising a plurality of radiation detector packages is schematically illustrated.

[0028] Figure 4C A perspective view of an imaging system according to an embodiment is schematically illustrated.

[0029] Figure 5 An image sensor according to an alternative embodiment is illustrated. Figure 4A and Figure 4B An image sensor according to an alternative embodiment is illustrated.

[0030] Figure 6 An image sensor according to yet another alternative embodiment is illustrated. Figure 4A and Figure 4B An image sensor according to yet another alternative embodiment is illustrated. DETAILED DESCRIPTION

[0031] A radiation detector

[0032] As an example, Figure 1A radiation detector 100 is schematically illustrated. The radiation detector 100 can comprise an array of pixels 150 (also referred to as sensing elements 150). The array can be a rectangular array (as shown), a honeycomb array, a hexagonal array, or any other suitable array. Figure 1 In an example, the array of pixels 150 has 4 rows and 7 columns; however, in general, the array of pixels 150 can have any number of rows and any number of columns. Figure 1 In an example, the array of pixels 150 has 4 rows and 7 columns; however, in general, the array of pixels 150 can have any number of rows and any number of columns.

[0033] Each pixel 150 can be configured to detect radiation incident thereon from a radiation source (not shown) and can be configured to measure a characteristic of the radiation (e.g., energy, wavelength, and frequency of a particle). The radiation can comprise particles, such as photons and subatomic particles. Each pixel 150 can be configured to count, over a period of time, the number of radiation particles incident thereon that fall in a plurality of energy bins. All pixels 150 can be configured to count, over the same period of time, the number of radiation particles incident thereon within a plurality of energy bins. When the incident radiation particles have similar energies, the pixels 150 can simply be configured to count, over a period of time, the number of radiation particles incident thereon without measuring the energy of each radiation particle.

[0034] Each pixel 150 can have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of an incident radiation particle into a digital signal or to digitize an analog signal representing the total energy of a plurality of incident radiation particles into a digital signal. The pixels 150 can be configured to operate in parallel. For example, while one pixel 150 is measuring an incident radiation particle, another pixel 150 can be waiting for a radiation particle to arrive. The pixels 150 can not necessarily be individually addressable.

[0035] The radiation detector 100 described herein can be applied, for example, to X-ray telescopes, X-ray mammography, industrial X-ray defect detection, X-ray microscopy or micro radiography, X-ray casting inspection, X-ray non-destructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. It can also be suitable to use this radiation detector 100 instead of photographic plates, photographic films, PSP plates, X-ray image intensifiers, scintillators, or other semiconductor X-ray detectors.

[0036] Figure 2A A radiation detector 100 is schematically illustrated. The radiation detector 100 can comprise an array of pixels 150 (also referred to as sensing elements 150). The array can be a rectangular array (as shown), a honeycomb array, a hexagonal array, or any other suitable array. Figure 1The radiation detector is shown in a simplified cross-sectional view along line 2A-2A. More specifically, the radiation detector 100 may include a radiation absorbing layer 110 and an electronic device layer 120 (e.g., including one or more ASICs 122 or application-specific integrated circuits) for processing or analyzing the electrical signals generated in the radiation absorbing layer 110 by incident radiation. The radiation detector 100 may or may not include a scintillator (not shown). The radiation absorbing layer 110 may contain a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof. The semiconductor material may have a high-quality attenuation coefficient for the radiation of interest. Figure 2B The illustration schematically shows an embodiment. Figure 2A A top view of the radiation detector 100. Figure 2B As an example, the electronics layer 120 of the radiation detector 100 may include six ASICs 122. Typically, the electronics layer 120 of the radiation detector 100 may include one or more ASICs 122.

[0037] As an example, Figure 2C schematically shown Figure 1 A detailed cross-sectional view of the radiation detector 100 along line 2A-2A. More specifically, the radiation absorption layer 110 may include one or more diodes (e.g., pin or pn) formed by one or more discrete regions 114 of a first doped region 111 and a second doped region 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 may be separated from each other by either the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 may have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). Figure 2C In the example, each discrete region 114 of the second doped region 113 forms a diode with the first doped region 111 and an optional intrinsic region 112. That is, in Figure 2C In the example, the radiation-absorbing layer 110 has multiple diodes (more specifically, 7 diodes correspond to...). Figure 1 In the array, each row has 7 pixels, 150. For simplicity, Figure 2C Only two pixels 150 are marked in the image. Multiple diodes may have an electrode 119A as a common electrode. The first doped region 111 may also have discrete portions.

[0038] Electronics layer 120 may include electronic systems 121 suitable for processing or interpreting signals generated by radiation incident on radiation-absorbing layer 110. Electronic systems 121 may include analog circuitry such as filter networks, amplifiers, integrators, and comparators, or digital circuitry such as microprocessors and memories. Electronic systems 121 may include one or more ADCs (analog-to-digital converters). Electronic systems 121 may include components shared by pixels 150 or components dedicated to a single pixel 150. For example, electronic systems 121 may include amplifiers dedicated to each pixel 150 and microprocessors shared among all pixels 150. Electronic systems 121 may be electrically connected to pixels 150 via vias 131. The space between vias may be filled with filler material 130, which may increase the mechanical stability of the connection between electronics layer 120 and radiation-absorbing layer 110. Other bonding techniques may connect electronics 121 to pixels 150 without using vias 131.

[0039] When radiation from a radiation source (not shown) impacts the radiation-absorbing layer 110 of a diode, the radiation particles can be absorbed and generate one or more charge carriers (e.g., electrons, holes) through various mechanisms. These charge carriers can drift to an electrode of one of the diodes under an electric field. This electric field can be an external electric field. Electrical contacts 119B can include discrete portions, each of which is in electrical contact with a discrete region 114. The term "electrical contact" is used interchangeably with the term "electrode." In embodiments, charge carriers can drift in various directions such that charge carriers generated by a single radiation particle are substantially not shared by two different discrete regions 114 (here, "substantially not shared" means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow to a different discrete region 114 compared to the remaining charge carriers). Charge carriers generated by radiation particles incident around a coverage area of ​​one of these discrete regions 114 are substantially not shared with the other of these discrete regions 114. Pixel 150 associated with discrete region 114 can be a region surrounding discrete region 114 in which substantially all (greater than 98%, greater than 99.5%, greater than 99.9%, or greater than 99.99%) of the charge carriers generated by incident radiating particles flow to discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of these charge carriers flow through pixel 150.

[0040] Figure 2D A schematic illustration is shown according to an alternative embodiment. Figure 1A detailed cross-sectional view of the radiation detector 100 along line 2A-2A. More specifically, the radiation absorbing layer 110 may comprise resistors of semiconductor materials such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof, but not diodes. This semiconductor material may have a high-quality attenuation coefficient for the radiation of interest. In an embodiment, Figure 2D The electronic device layer 120 is similar in structure and function to Figure 2C The electronic device layer 120.

[0041] When radiation impacts the radiation-absorbing layer 110, which includes resistors but not diodes, it can be absorbed and generate one or more charge carriers through various mechanisms. The radiating particles can generate 10 to 100,000 charge carriers. These charge carriers can drift to electrical contacts 119A and 119B under an electric field. This electric field can be an external electric field. Electrical contact 119B can include discrete portions. In embodiments, charge carriers can drift in various directions such that charge carriers generated by a single radiating particle are substantially not shared by the two distinct discrete portions of electrical contact 119B (here, "substantially not shared" means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow to a different discrete portion compared to the remaining charge carriers). Charge carriers generated by radiating particles incident on the coverage area of ​​one of these discrete portions of electrical contact 119B are substantially not shared with the other of these discrete portions of electrical contact 119B. Pixel 150 associated with a discrete portion of electrical contact 119B can be a region surrounding the discrete portion, in which substantially all (greater than 98%, greater than 99.5%, greater than 99.9%, or greater than 99.99%) of the charge carriers generated by incident radiant particles flow toward the discrete portion of electrical contact 119B. That is, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow through a pixel associated with a discrete portion of electrical contact 119B.

[0042] Radiation detector packaging

[0043] Figure 3AA schematic top view of a radiation detector package 300 according to an embodiment is shown. Specifically, the radiation detector package 300 may include a set of printed circuit boards (set PCB) 310 and four radiation detectors 100 mounted on the set PCB 310. Typically, the radiation detector package 300 may include any number of radiation detectors 100. The term "PCB" as used herein is not limited to a particular material. For example, a PCB may include semiconductors. For clarity, wiring between the four radiation detectors 100 and the set PCB 310 is not shown. The set PCB 310 may have a rectangular shape. Typically, the set PCB 310 may have any shape.

[0044] The PCB group 310 may have an area 305 not covered by the radiation detector 100 (e.g., for accommodating input / output ports 320). Each radiation detector 100 in the radiation detector package 300 may have a pixel 150. Figure 1 The effective area 190 is where the radiation detector 100 is located. Each radiation detector 100 of the radiation detector package 300 may have a peripheral area 195 near its edge. The peripheral area 195 of the radiation detector 100 has no pixels 150, and therefore does not detect radiation particles incident on it. Figure 3B The illustration schematically shows an embodiment. Figure 3A A cross-sectional view of the radiation detector package 300 along line 3B-3B.

[0045] In an embodiment, Figure 3A The radiation detector 100 can be rotated counterclockwise to obtain... Figure 3C The radiation detector is packaged in a 300-type package. Figure 3C In the diagram, for the sake of simplicity, only the effective area 190 of the radiation detector 100 is shown.

[0046] Image sensor

[0047] Figure 4A A schematic top view of an image sensor 490 according to an embodiment is shown. Specifically, the image sensor 490 may include a system PCB 410 and a mounting surface 412 on the system PCB 410. Figure 3C The image sensor 490 comprises three radiation detector packages 300. Typically, the image sensor 490 may include any number of radiation detector packages 300, and each radiation detector package 300 may have any number of radiation detectors 100. In other words, the number of radiation detectors 100 in each radiation detector package 300 does not need to be the same. For simplicity, only the effective area 190 of the radiation detector 100 is shown. For clarity, the electrical connections between the system PCB 410 and the three radiation detector packages 300 are not shown.

[0048] In an embodiment, such asFigure 4A As shown, the effective regions 190 of each radiation detector package 300 of the image sensor 490 may not overlap in the normal direction (not shown) perpendicular to the mounting surface 412 of the system PCB 410. In other words, for each radiation detector package 300 of the image sensor 490, two effective regions 190 of the radiation detector 100 of the radiation detector package 300 do not overlap in the normal direction. Figure 4A In the middle, the mounting surface 412 is parallel to the page; and the normal direction is perpendicular to the page.

[0049] In an embodiment, such as Figure 4A and Figure 4B As shown, the three radiation detector packages 300 can overlap in the normal direction. Specifically, the left portion of the middle radiation detector package 300 (including the input / output port 320) can be below the left radiation detector package 300 and is not shown for simplicity. Similarly, the left portion of the right radiation detector package 300 (including the input / output port 320) can be below the middle radiation detector package 300 and is not shown for simplicity. Figure 4B The illustration schematically shows an embodiment. Figure 4A The image detector 490 is a cross-sectional view along line 4B-4B.

[0050] In the embodiments, reference is made to Figure 4A and Figure 4B The dead zone 488 of the image sensor 490 can include any area of ​​the image sensor 490 that is not covered by the effective area 190 of the radiation detector 100. The dead zone 488 cannot detect incident radiation. However, the image sensor 490 can capture multiple partial images of an object or scene (not shown) one by one, and these captured partial images can then be stitched together to form a complete image of the object or scene.

[0051] In an embodiment, the image sensor 490 can translate (i.e., move such that all parts of the image sensor 490 travel in the same direction without rotation or change in shape) while scanning an object or scene (i.e., capturing multiple partial images of the object or scene one by one). This translation direction of the image sensor 490 can be referred to as the scanning direction. In an embodiment, such as Figure 4A As shown, the image sensor 490 can be configured to scan in the eastward direction (i.e., the 3 o'clock direction), and the three groups of PCBs 310 can be arranged in rows extending in the scanning direction (i.e., in the eastward direction).

[0052] In an embodiment, such as Figure 4A and Figure 4BAs shown, the three groups of PCBs 310 can overlap in the normal direction, so that all three groups of PCBs 310 form a single printed circuit board in the normal direction, and a plane parallel to the normal direction and parallel to the scanning direction (i.e., eastward) intersects all three groups of PCBs. Here, "the groups of PCBs 310 forming a single printed circuit board in the normal direction" means that there are no gaps between them when viewed along the normal direction.

[0053] In an embodiment, such as Figure 4B As shown, the input / output ports 320 on the middle group PCB 310 can be sandwiched between the middle group PCB 310 and the left group PCB 310. In an embodiment, as... Figure 4B As shown, the input / output ports 320 on the middle group PCB 310 can overlap with the effective area 190 on the left group PCB 310 in the normal direction.

[0054] In summary, the above describes an image sensor (e.g., Figure 4A and Figure 4B The image sensor 490 includes: (A) a system PCB (e.g., system PCB 410); and (B) M group PCBs, including group PCBs (i) mounted on a mounting surface (e.g., mounting surface 412) of the system PCB, i = 1, ..., M (e.g., ...). Figure 4A and Figure 4B Group PCB(1), Group PCB(2) and Group PCB(3)); and (C) for i = 1, ..., M, Ni radiation detectors are installed on Group PCB(i) (e.g., N1 = 4 radiation detectors 100 are installed on Group PCB(1); N2 = 4 radiation detectors 100 are installed on Group PCB(2); and N3 = 4 radiation detectors 100 are installed on Group PCB(3)).

[0055] Furthermore, in the embodiments, the image sensor can be configured to scan the scene in a scanning direction (e.g., the scanning direction can be eastward, i.e., at the 3 o'clock position).

[0056] Furthermore, for each group PCB(i) (e.g., Figure 4A and Figure 4B Group PCB (1), Group PCB (2), and Group PCB (3) do not have a plane (A) that is parallel to the normal direction of the mounting surface of the system PCB (e.g., perpendicular to the normal direction). Figure 4A(A) The orientation of the page, (B) Parallel to the scanning direction (e.g., eastward), (C) Dividing all effective areas of the Ni radiation detectors (e.g., 4 effective areas 190) into two groups of effective areas, and (D) Not intersecting with any effective area of ​​all the effective areas of the Ni radiation detectors. This condition (i.e., there is no such plane that...) ensures that when the image sensor 490 scans the scene in the scanning direction, the effective area 190 of each radiation detector package 300 of the image sensor 490 can scan a region without leaving any unscanned areas in that region.

[0057] This can be referenced. Figure 3C The following explanation is provided. If the scanning direction is at the 2 o'clock position (arrow 330), then the gap 340 between the four effective regions 190 of the radiation detector package 300 will result in unscanned areas existing in the area swept by the four effective regions 190. This situation occurs when the above condition is not met (i.e., there is no such plane, ...). Alternatively, if the scanning direction is at the 3 o'clock position (arrow 350), then there will be no unscanned areas in the area swept by the four effective regions 190. This alternative situation occurs when the above condition is met (i.e., there is no such plane, ...).

[0058] Figure 4C A perspective view of an imaging system 400 according to an embodiment is schematically shown. Specifically, the imaging system 400 may include... Figure 4A and Figure 4B The image sensor 490, radiation source 450, and mask 470 are included. Figure 4C For simplicity, details of the image sensor 490 are not shown. In this embodiment, for radiation from the radiation source 450 incident on the mask 470, only radiation incident on the mask window 472 of the mask 470 is allowed to pass through the mask 470, thereby obtaining a radiation beam 452 with a beam boundary 452b.

[0059] In an embodiment, the imaging system 400 may be arranged such that, when the image sensor 490 scans a scene (which may include object 460), the beam boundary 452b of the radiation beam 452 does not intersect with any effective region 190 of all effective regions 190 of the image sensor 490. In an embodiment, as... Figure 4C As shown, the radiation beam 452 can be aimed at every point in all effective areas 190 of the image sensor 490. In other words, every point in all effective areas 190 of the image sensor 490 is targeted by the radiation beam 452.

[0060] In the embodiments, reference is made to Figure 5In each of the three radiation detector packages 300 of the image sensor 490, the effective regions 190 may overlap in the normal direction. In an embodiment, as... Figure 5 As shown, the effective regions 190 of each radiation detector package 300 of the image sensor 490 can overlap, such that all effective regions 190 of each radiation detector package 300 form a single effective region in the normal direction. Here, all effective regions 190 forming a single effective region in the normal direction means that there are no gaps between the effective regions 190 when viewed along the normal direction. Furthermore, in the embodiment, as... Figure 5 As shown, for each radiation detector package 300 of the image sensor 490, a plane (not shown) parallel to the normal direction and perpendicular to the scanning direction intersects all effective areas 190 of the radiation detector 100 of the radiation detector assembly 300.

[0061] In an embodiment, Figure 5 The three radiation detectors in the 300 package can be arranged more compactly together, thus obtaining... Figure 6 The image sensor 490. In Figure 6 For simplicity, only the effective area 190 of the three radiation detector packages 300 of the image sensor 490 is shown. In an embodiment, as... Figure 6 As shown, all 12 effective regions 190 of the three radiation detector packages 300 form an effective region in the normal direction.

[0062] 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 illustrative purposes and are not intended to be limiting; the true scope and spirit are indicated by the appended claims.

Claims

1. An imaging system, comprising: an image sensor, comprising: a system printed circuit board (system PCB); and M radiation detector packages i, i = 1,..., M, mounted on a mounting surface of the system PCB, each radiation detector package i comprising a group printed circuit board (group PCB(i)) and Ni radiation detectors mounted on the group PCB(i), wherein M and Ni are integers greater than 1, wherein i = 1,..., M, wherein the image sensor is configured to scan a scene in a scan direction, and wherein, for each radiation detector package i, there is no plane that (A) is parallel to a normal direction of the mounting surface of the system PCB, (B) is parallel to the scan direction, (C) divides all active areas of the Ni radiation detectors into two groups of active areas, and (D) does not intersect any active area of all active areas of the Ni radiation detectors.

2. The imaging system of claim 1, wherein, All Ni are the same, wherein i = 1,..., M.

3. The imaging system of claim 1, wherein, The M group PCBs and the system PCB comprise a semiconductor.

4. The imaging system of claim 1, wherein, Each of the M group PCBs has a rectangular shape.

5. The imaging system of claim 1, wherein, The M group PCBs are arranged in a row extending in the scan direction.

6. The imaging system of claim 1, wherein, All active areas of all the Ni radiation detectors overlap in the normal direction, wherein i = 1,..., M, such that all active areas of all the Ni radiation detectors form a piece of active area in the normal direction, wherein i = 1,..., M.

7. The imaging system of claim 1, further comprising a radiation source configured to generate a radiation beam whose boundary does not intersect any active area of all active areas of the Ni radiation detectors when the image sensor scans the scene, wherein i = 1,..., M.

8. The imaging system of claim 7, wherein, Radiation of the radiation beam aims at respective points of all active areas of all the Ni radiation detectors, wherein i = 1,..., M.

9. The imaging system of claim 7, further comprising a mask that allows some radiation of the radiation source to pass through the mask, thereby resulting in the radiation beam.

10. The imaging system of claim 1, wherein, For each group PCB(i), no two active areas of the Ni radiation detectors overlap in the normal direction, wherein i = 1,..., M.

11. The imaging system of claim 1, wherein, For each group PCB(i), (A) the Ni radiation detectors of the group PCB(i) overlap in the normal direction, such that all active areas of the Ni radiation detectors form a piece of active area in the normal direction, and (B) a plane parallel to the normal direction and perpendicular to the scan direction intersects all active areas of the Ni radiation detectors, wherein i = 1,..., M.

12. The imaging system of claim 1, wherein the M group PCBs overlap in the normal direction, such that all the M group PCBs form a piece of printed circuit board in the normal direction, and the system PCB overlaps all the M group PCBs in the normal direction, such that the system PCB and all the M group PCBs form a piece of printed circuit board in the normal direction. wherein a plane parallel to the normal direction and parallel to the scan direction intersects all of the M group PCBs.

13. The imaging system of claim 12, further comprising an input / output port on each of the M group PCBs.

14. The imaging system of claim 13, wherein, The input / output port on a first group PCB of the M group PCBs is sandwiched between the first group PCB and a second group PCB of the M group PCBs.

15. The imaging system of claim 13, wherein, The input / output port on a first group PCB of the M group PCBs overlaps in the normal direction with an active area on a second group PCB of the M group PCBs.

16. The imaging system of claim 1, wherein, For each group PCB (i), each of the Ni radiation detectors on the group PCB (i) comprises: (A) a radiation-absorbing layer and (B) an electronics layer comprising a plurality of application-specific integrated circuits (ASICs), where i = 1, …, M.

17. The imaging system of claim 16, wherein, The radiation-absorbing layer and the electronics layer are electrically connected to each other by a via.

18. The imaging system of claim 16, wherein, The radiation-absorbing layer comprises a plurality of diodes.

19. The imaging system of claim 16, wherein, The radiation-absorbing layer comprises a semiconductor.

20. The imaging system of claim 16, wherein, The electronics layer comprises an electronic system configured to process signals generated by radiation incident on the radiation-absorbing layer.

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