image sensor

Abstract

Disclosed herein is an image sensor comprising: a plurality of X-ray detectors; an actuator configured to move the plurality of X-ray detectors along a direction to a plurality of positions, wherein the image sensor is configured to capture images of portions of a scene at the positions respectively by using the detectors; wherein each image of the portions has at least one edge that is at an angle to the direction; and wherein the image sensor is configured to form an image of the scene by stitching the images of the portions.

Description

BACKGROUND

[0001] An x-ray detector can be a device for measuring the flux, spatial distribution, spectrum, or other properties of radiation.

[0002] X-ray detectors can be used for many applications. One important application is imaging. Radiographic imaging is a radiographic technique and can be used to reveal the internal structure of an opaque object of non-uniform composition, such as the human body.

[0003] Early x-ray detectors for imaging included photographic plates and photographic film. Photographic plates can be glass plates with a photosensitive emulsion coating. Although photographic plates have been replaced by photographic film, they can still be used for special cases due to the superior quality they provide and their extreme stability. Photographic film can be plastic film (e.g., a strip or sheet) with a photosensitive emulsion coating.

[0004] In the 1980s, photo-stimulable phosphor plates (PSP plates) became available. A PSP plate can contain a phosphor material with color centers in its crystal lattice. When a PSP plate is 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 plate. When the plate is scanned by the laser, the trapped excited electrons emit light, which is collected by a photomultiplier tube. The collected light is converted into a digital image. Compared to photographic plates and photographic film, PSP plates can be reused.

[0005] Another x-ray detector is a radiation image intensifier. The components of a radiation image intensifier are typically sealed in a vacuum. Compared to photographic plates, photographic film, and PSP plates, a radiation image intensifier can produce real-time images, i.e., no post-exposure processing is needed to produce the image. Radiation first hits an input phosphor (e.g., cesium iodide) and is converted into visible light. The visible light then hits a 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 an output phosphor and cause the output phosphor to produce a visible light image.

[0006] A scintillator operates somewhat similarly to a radiation image intensifier in that a scintillator (e.g., sodium iodide) absorbs radiation and emits visible light, which can then be detected by an image sensor suitable for visible light. In a scintillator, the visible light diffuses and scatters in all directions, thereby reducing the spatial resolution. Reducing the thickness of the scintillator helps improve the spatial resolution, but also reduces the absorption of radiation. Thus, a scintillator must strike a compromise between absorption efficiency and resolution.

[0007] Semiconductor X-ray detectors largely overcome this problem by directly converting the radiation into electrical signals. A semiconductor X-ray detector can include a semiconductor layer that absorbs radiation of a wavelength of interest. When an X-ray photon is absorbed in the semiconductor layer, multiple charge carriers (e.g., electrons and holes) are generated and swept under an electric field toward an electrical contact on the semiconductor layer. The cumbersome thermal management required in currently available semiconductor X-ray detectors (e.g., Medipix) can make it difficult or impossible to produce detectors with large areas and large numbers of pixels. SUMMARY

[0008] An image sensor is disclosed herein, the image sensor comprising: a plurality of X-ray detectors; an actuator configured to move the plurality of X-ray detectors along a direction to a plurality of positions, wherein the image sensor is configured to capture images of portions of a scene at the positions respectively by using the detectors; wherein each image of the portions has at least one edge that is at an angle to the direction; and wherein the image sensor is configured to form an image of the scene by stitching the images of the portions.

[0009] According to an embodiment, the plurality of X-ray detectors are spaced apart.

[0010] According to an embodiment, the image sensor further comprises a mask having a plurality of X-ray transmissive regions.

[0011] According to an embodiment, the X-ray transmissive regions are configured to form a spatially discontinuous exposure area on the image sensor; wherein the X-ray intensity outside the exposure area is substantially zero.

[0012] According to an embodiment, an active area of the image sensor is within the exposure area.

[0013] According to an embodiment, a variation in X-ray intensity across a perimeter of the exposure area is smooth.

[0014] According to an embodiment, the actuator is configured to move the mask so that the X-ray detectors are kept in alignment with the exposure area at the positions.

[0015] According to an embodiment, at least some of the plurality of X-ray detectors are arranged in staggered rows.

[0016] According to an embodiment, the X-ray detectors in a same row are uniform in size; wherein a distance between two adjacent X-ray detectors in the same row is greater than a width of one X-ray detector in the same row in a direction of extension of the row, and less than twice the width.

[0017] According to an embodiment, the actuator comprises a robotic arm.

[0018] According to embodiments, at least some of the plurality of X-ray detectors comprise multi-layer detectors.

[0019] According to embodiments, at least some of the plurality of X-ray detectors are rectangular shaped.

[0020] According to embodiments, at least some of the plurality of X-ray detectors are hexagonal shaped.

[0021] According to embodiments, at least some of the plurality of X-ray detectors are right trapezoidal shaped.

[0022] According to embodiments, the actuator comprises a control unit configured to determine the position.

[0023] Disclosed herein is a system comprising any of the above image sensors and an X-ray source. BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1A An image sensor according to embodiments is schematically illustrated.

[0025] FIG. 1B A cross-sectional view of an image sensor according to an embodiment is schematically illustrated.

[0026] FIG. 2 A plurality of images of a portion of a scene captured by an image sensor according to embodiments is schematically illustrated.

[0027] FIGS. 3A-3C An arrangement of X-ray detectors in an image sensor according to some embodiments is schematically illustrated.

[0028] FIG. 4 An image sensor with a plurality of hexagonal or right trapezoidal shaped X-ray detectors according to embodiments is schematically illustrated.

[0029] FIG. 5 An X-ray detector has a pixel array according to embodiments is schematically illustrated.

[0030] FIG. 6A A cross-sectional view of an X-ray detector according to embodiments is schematically illustrated.

[0031] FIG. 6B A detailed cross-sectional view of an X-ray detector according to embodiments is schematically illustrated.

[0032] FIG. 6C An alternative detailed cross-sectional view of an X-ray detector according to embodiments is schematically illustrated.

[0033] FIG. 7A andFIG. 7B Each illustrates an embodiment. FIG. 6A , FIG. 6B and FIG. 6C A component diagram of the electronic system of the X-ray detector.

[0034] FIG. 8 The diagram schematically illustrates the time-varying current (upper curve) flowing through the electrode or electrical contact of a diode or resistor exposed to radiation in an embodiment, and the corresponding time-varying voltage of the electrode (lower curve), the current being caused by charge carriers generated by X-ray photons incident on the radiation-absorbing layer.

Detailed Implementation Methods

[0035] FIG. 1A An image sensor 9000 according to an embodiment is schematically shown. The image sensor 9000 may be located at multiple positions along direction 951 (e.g., FIG. 1A The image sensor 9000 captures images of a portion of scene 50 at positions 910 and 920. The image sensor 9000 may include multiple X-ray detectors (e.g., ...). FIG. 1A The first X-ray detector 100A, the second X-ray detector 100B, the mask 600, and the actuator ( FIG. 1B (In the middle). The image sensor 9000 may include a support 107, which may be a system printed circuit board (PCB). A plurality of X-ray detectors 100 (e.g., 100A and 100B) may be arranged on a flat surface of the support 107. The plurality of X-ray detectors (e.g., 100A and 100B) may be configured to receive X-rays from an X-ray source 109 that pass through a portion of the scene 50 and are incident thereon. The mask 60 may include a plurality of X-ray transmission zones 601.

[0036] In the example shown in Figure 1, image sensor 9000 can be moved from a first position 910 to a second position 920 along a first direction 951 by actuator 500. According to one embodiment, at the first position 910 relative to scene 50, image sensor 9000 uses X-rays from source 109 that have passed through scene 50 to capture a first partial image 1010 of a portion of scene 50; and at the second position 920 relative to scene 50, image sensor 9000 uses X-rays from source 109 that have passed through scene 50 to capture a second partial image 1020 of a portion of scene 50. Images of portions of scene 50 (e.g., 1010 and 1020) can be formed by X-rays passing through X-ray transmission zone 601 of mask 600 and detected by X-ray detector 100. Each image of a portion captured by the X-ray detector can have at least one edge at an angle 953 to direction 951 (e.g., FIG. 1AEdge 1011 or edge 1021 in the middle). As used herein, an edge at an angle to a direction means that the edge is neither parallel nor perpendicular to the direction. According to an embodiment, in FIG. 1A In the example shown, edges 1011 and 1021 are at an angle to direction 951. For example, the angle 953 between edge 1011 or edge 1021 and direction 951 can be greater than 10 degrees, 30 degrees, or 45 degrees, as shown. FIG. 1A As shown.

[0037] FIG. 1B A cross-sectional view of an image sensor 9000 according to one embodiment is schematically shown. FIG. 1B In the example shown, mask 600 includes a plurality of X-ray transmission zones 601. The X-ray transmission zones 601 of mask 600 allow at least a portion of the X-rays incident thereon to pass through, while the remaining X-rays are blocked by mask 600. An example of mask 600 may be a perforated metal sheet with sufficient thickness to block X-rays. These perforations may be radiation transmission zones 601. According to embodiments, such as... FIG. 1A and 1B As shown, the X-ray transmission region 601 is configured to form a spatially discontinuous exposure area on the image sensor 9000. (As...) FIG. 1B As shown, the exposure area formed by the X-ray transmission region 601 can be aligned with the X-ray detector 100 on the image sensor 9000, wherein the effective region 9002 of the X-ray detector 100 is within the exposure area. According to an embodiment, the mask 600 blocks X-rays from the source 109 that would otherwise reach the dead zone 9004 outside the exposure area on the image sensor 9000. Therefore, the intensity of incident X-rays outside the exposure area is essentially zero, i.e., the intensity of X-rays outside the exposure area is insufficient to be detected by the X-ray detector 100. FIG. 1B In the examples, the X-ray detector 100 may have an active region 9002 and a peripheral region 9005 near the edge of its detector 100. The active region 9002 may be sensitive to X-rays incident thereon, the peripheral region 9005 may be insensitive to incident X-rays, and the detector 100 may not detect X-rays incident thereon. According to the embodiments, the change in X-ray intensity across the periphery of the exposure area is smooth.

[0038] According to the embodiments, such as FIG. 1BThe illustrated actuator 500 is configured to move the image sensor 9000 and the mask 600 together to a plurality of positions. The actuator 500 can have various designs (e.g., including a robotic arm). The actuator 500 can also include a controller configured to determine movement to the plurality of positions. According to an embodiment, when the actuator 500 moves the image sensor 9000 and the mask 600 to the plurality of positions, the X-ray detector 100 is kept in alignment with the exposure area on the image sensor 9000 at each position at which an image of a portion of the scene 50 is captured. That is, when the detector 100 is at the first position 910, an image of a first portion of the scene 50 is captured by the image sensor 9000 using the detector 100, and when the detector 100 is at the second position 920, an image of a second portion of the scene 50 is captured by the image sensor 9000. The images of these portions (e.g., 1010, 1020) can then be stitched to form an image of the scene 50. The images of these portions can overlap one another to facilitate stitching.

[0039] FIG. 2 An image sensor 9000 according to an embodiment that captures a plurality of images of portions of a scene 50 is schematically illustrated. In this example, the image sensor 9000 includes an array of pixels 9010, a mask 600, and an actuator 500. The array of pixels 9010 is configured to capture images of portions of a scene 50. The mask 600 is configured to block X-rays from reaching the array of pixels 9010. The actuator 500 is configured to move the image sensor 9000 and the mask 600 together to a plurality of positions. The actuator 500 can have various designs (e.g., including a robotic arm). The actuator 500 can also include a controller configured to determine movement to the plurality of positions. According to an embodiment, when the actuator 500 moves the image sensor 9000 and the mask 600 to the plurality of positions, the X-ray detector 100 is kept in alignment with the exposure area on the image sensor 9000 at each position at which an image of a portion of the scene 50 is captured. That is, when the detector 100 is at the first position 910, an image of a first portion of the scene 50 is captured by the image sensor 9000 using the detector 100, and when the detector 100 is at the second position 920, an image of a second portion of the scene 50 is captured by the image sensor 9000. The images of these portions (e.g., 1010, 1020) can then be stitched to form an image of the scene 50. The images of these portions can overlap one another to facilitate stitching. FIG. 2 In the illustrated example, the image sensor 9000 and the mask 600 can be moved together to three positions A, B, and C using the actuator 500. The image sensor 9000 can capture images 51A, 51B, and 51C of portions of the scene 50 at positions A, B, and C, respectively. According to an embodiment, the image sensor 9000 can stitch the images 51A, 51B, and 51C of these portions to form an image 52 of the scene 50. The images 51A, 51B, and 51C of these portions can overlap one another to facilitate stitching. Each portion of the scene 50 can be in at least one of the images captured when the detector is at the plurality of positions. That is, the images of these portions can cover the entire scene 50 when stitched together.

[0040] The X-ray detector 100 can be arranged in the image sensor 9000 in a variety of ways. FIG. 3AAn arrangement according to an embodiment is schematically illustrated in which the detectors 100 are arranged in staggered rows. For example, detectors 100A and 100B are in the same row, aligned in the Y direction, and uniform in size; detectors 100C and 100D are in the same row, aligned in the Y direction, and uniform in size. The X-ray detectors 100A and 100B are staggered in the X direction relative to the detectors 100C and 100D, which means that the X-ray detectors 100A and 100B are not aligned with the detectors 100C and 100D in the X direction. According to an embodiment, the distance X2 between two adjacent detectors 100A and 100B in the same row is greater than the width X1 of one detector in the same row (i.e. the size in the X direction, the X direction being the direction of extension of the row), and less than twice the width X1. The X-ray detectors 100A and 100E are in the same column, aligned in the X direction, and uniform in size; the distance Y2 between two adjacent detectors 100A and 100E in the same column is less than the width Y1 of one X-ray detector in the same column (i.e. the size in the Y direction). This arrangement allows imaging of a scene as shown in FIG. 2 and an image of the scene can be obtained by stitching three images of portions of the scene captured at three positions spaced apart in the X direction.

[0041] FIG. 3B Another arrangement according to an embodiment is schematically illustrated in which the X-ray detectors 100 are arranged in a rectangular grid. For example, the X-ray detectors 100 can comprise detectors 100A, 100B, 100E and 100F arranged as precisely as FIG. 3A in the absence of detectors 100C, 100D, 100G or 100H in FIG. 3A This arrangement allows imaging of a scene by taking images of portions of the scene at six positions. For example, three positions spaced apart in the X direction and another three positions spaced apart in the X direction and spaced apart in the Y direction from the first three positions.

[0042] Other arrangements are possible. For example, in FIG. 3C the X-ray detectors 100 can span the entire width of the image sensor 9000 in the X direction with a distance Y2 between two adjacent X-ray detectors 100 being less than the width of one X-ray detector Y1. Assuming the width of the detectors in the X direction is greater than the width of the scene in the X direction, an image of the scene can be stitched from two images of portions of the scene captured at two positions spaced apart in the Y direction.

[0043] The X-ray detectors 100 in the image sensor 9000 can be provided with any suitable size and shape. According to an embodiment (for example, in FIG. 2As shown in FIG. 3), at least some of the X-ray detectors are rectangular in shape. According to embodiments, as FIG. 4 As shown in FIG. 3), at least some of the X-ray detectors are rectangular in shape. According to embodiments, as

[0044] FIG. 5 An X-ray detector 100 according to embodiments is schematically shown as having an array of pixels 150. The array can be a rectangular array, a honeycomb array, a hexagonal array, or any other suitable array. Each pixel 150 can be configured to detect X-ray photons incident thereon, measure the energy of the X-ray photons, or perform both operations. For example, each pixel 150 can be configured to count the number of radiation particles incident thereon over a period of time that have energies falling in a plurality of bins. All of the pixels 150 can be configured to count the number of radiation particles incident thereon over the same period of time that fall in a plurality of energy bins. 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 to a digital signal. The ADC can have a resolution of 10 bits or more. Each pixel 150 can be configured to measure its dark current, for example, before or at the same time as each X-ray photon is incident thereon. Each pixel 150 can be configured to subtract the contribution of the dark current from the energy of the X-ray photons incident thereon. The pixels 150 can be configured to operate in parallel. For example, while one pixel 150 is measuring an incident X-ray photon, another pixel 150 can be waiting for another X-ray photon to arrive. The pixels 150 can be, but need not be, individually addressable. The radiation particles can be X-ray photons.

[0045] FIG. 6A A cross-sectional view of one of the X-ray detectors 100 according to embodiments is schematically shown. The X-ray detector 100 can include a radiation-absorbing layer 110 and an electronics layer 120 (e.g., an ASIC) for processing or analyzing electrical signals generated in the radiation-absorbing layer 110 by incident radiation. In one embodiment, the X-ray detector 100 of the image sensor 9000 does not include a scintillator. The radiation-absorbing layer 110 can include a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or single-crystal silicon. The semiconductor can have a high mass attenuation coefficient for the radiation energy of interest. A surface 103 of the radiation-absorbing layer 110 distal from the electronics layer 120 is configured to receive radiation.

[0046] As shown in FIG. 3), at least some of the X-ray detectors are rectangular in shape. According to embodiments, as FIG. 6BIn the detailed cross-sectional view of the X-ray detector 100 shown in FIG. 1, according to an embodiment, the radiation-absorbing layer 110 can include one or more diodes (e.g., p-i-n or p-n) formed from the first doped region 111, the second doped region 113, and one or more discrete regions 114. The second doped region 113 can 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 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). Each discrete region 114 of the second doped region 113 forms a diode with the first doped region 111 and the optional intrinsic region 112. That is, in the example shown in FIG. 1, the radiation-absorbing layer 110 has multiple diodes with the first doped region 111 as a common electrical contact. The first doped region 111 can also have discrete portions. FIG. 6B In the example shown in FIG. 1, the radiation-absorbing layer 110 has multiple diodes with the first doped region 111 as a common electrical contact. The first doped region 111 can also have discrete portions.

[0047] When an X-ray photon strikes the radiation-absorbing layer 110 including the diodes, the X-ray photon can be absorbed and generate one or more charge carriers by a variety of mechanisms. The X-ray photon can generate 10 to 100,000 charge carriers. The charge carriers can drift under an electric field to an electrical contact of one of the diodes. The field can be an external electric field. The electrical contact 119B can include discrete portions, each in electrical contact with a discrete region 114. In an embodiment, the charge carriers can drift in various directions such that substantially none of the charge carriers generated by a single X-ray photon flow to a different discrete region 114 (here "substantially none" means less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of the charge carriers flow to a different discrete region 114 than the rest of the charge carriers). The charge carriers generated by an X-ray photon incident around the footprint of one of the discrete regions 114 are substantially not shared with another one of the discrete regions 114. A pixel 150 associated with a discrete region 114 can be a region around the 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 an X-ray photon incident therein at a 0° angle of incidence flow to the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of the charge carriers flow through the pixel.

[0048] As FIG. 6CAs shown in the alternative detailed cross-sectional view of the X-ray detector 100, according to embodiments, the radiation-absorbing layer 110 can include a resistor of a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof, but not a diode. The semiconductor can have a high mass attenuation coefficient for the radiation energy of interest.

[0049] When an X-ray photon strikes the radiation-absorbing layer 110 including a resistor but not a diode, it can be absorbed and generate one or more charge carriers through a variety of mechanisms. An X-ray photon can generate 10 to 100,000 charge carriers. The charge carriers can drift under an electric field to the electrical contacts 119A and 119B. The field can be an external electric field. The electrical contact 119B includes discrete portions. In embodiments, the charge carriers can drift in various directions such that substantially none of the charge carriers generated by a single X-ray photon are shared by two different discrete portions of the electrical contact 119B (where "substantially none" means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of the charge carriers flow to a different discrete portion compared to the rest of the charge carriers). Substantially none of the charge carriers generated by an X-ray photon incident around the footprint of one of the discrete portions of the electrical contact 119B are shared with another of the discrete portions of the electrical contact 119B. A pixel 150 associated with a discrete portion of the electrical contact 119B can be the area around 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 an X-ray photon incident at an angle of 0° thereto 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 charge carriers flow through a pixel associated with one of the discrete portions of the electrical contact 119B.

[0050] The electronics layer 120 can include an electronic system 121 suitable for processing or interpreting signals generated by particles of radiation incident on the radiation-absorbing layer 110. The electronic system 121 can include analog circuitry such as filter networks, amplifiers, integrators, and comparators or digital circuitry such as microprocessors and memory. The electronic system 121 can include components shared by multiple pixels or components dedicated to a single pixel. For example, the electronic system 121 can include an amplifier dedicated to each pixel and a microprocessor shared among all pixels. The electronic system 121 can be electrically connected to the pixels through vias 131. The space between the vias can be filled with a filler material 130, which can increase the mechanical stability of the connection of the electronics layer 120 to the radiation-absorbing layer 110. Other bonding techniques can connect the electronic system 121 to the pixels 150 without using vias.

[0051] FIG. 7A and FIG. 7B Both show a component diagram of an electronic system 121 according to an embodiment. The electronic system 121 can 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.

[0052] The first voltage comparator 301 is configured to compare a voltage of the at least one electrical contact 119B to a first threshold. The first voltage comparator 301 can be configured to monitor the voltage directly or to calculate the voltage by integrating a current flowing through the electrical contact 119B over a period of time. The first voltage comparator 301 can be controllably activated or deactivated by the controller 310. The first voltage comparator 301 can be a continuous comparator. That is, the first voltage comparator 301 can be configured to be continuously activated and continuously monitor the voltage. The first voltage comparator 301 can be a clocked comparator. The first threshold can be 5-10%, 10%-20%, 20-30%, 30-40%, or 40-50% of a maximum voltage that one incident X-ray photon can produce on the electrical contact 119B. The maximum voltage can depend on the energy of the incident X-ray photon, the material of the radiation-absorbing layer 110, and other factors. For example, the first threshold can be 50 mV, 100 mV, 150 mV, or 200 mV.

[0053] The second voltage comparator 302 is configured to compare the voltage to a second threshold. The second voltage comparator 302 can be configured to monitor the voltage directly or to calculate the voltage by integrating a current flowing through the diode or electrical contact over a period of time. The second voltage comparator 302 can be a continuous comparator. The second voltage comparator 302 can be controllably activated or deactivated by the controller 310. When the second voltage comparator 302 is deactivated, the power consumption of the second voltage comparator 302 can be less than 1%, 5%, 10%, or 20% of the power consumption when the second voltage comparator 302 is activated. 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 can be 200%-300% of the first threshold. The second threshold can be at least 50% of a maximum voltage that one incident X-ray photon can produce on the electrical contact 119B. For example, the second threshold can be 100 mV, 150 mV, 200 mV, 250 mV, or 300 mV. The second voltage comparator 302 and the first voltage comparator 301 can be the same component. That is, the system 121 can have one voltage comparator that can compare the voltage to two different thresholds at different times.

[0054] The first voltage comparator 301 or the second voltage comparator 302 can include one or more operational amplifiers or any other suitable circuitry. The first voltage comparator 301 or the second voltage comparator 302 can have a high speed to allow the electronic system 121 to operate under high flux of incident radiation particles. However, having a high speed is usually at the cost of power consumption.

[0055] The counter 320 is configured to record the number of radiation particles incident on the radiation-absorbing layer comprising the pixel 150. The counter 320 can be a software component (e.g., a number stored in a computer memory) or a hardware component (e.g., a 4017 IC and a 7490 IC).

[0056] The controller 310 can be a hardware component, such as a microcontroller and a microprocessor. The controller 310 is configured to start a time delay from the time when the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold value (e.g., the absolute value of the voltage increases from a value below the absolute value of the first threshold value to a value equal to or above the absolute value of the first threshold value). The absolute value is used here because the voltage can be negative or positive, depending on whether the cathode or the anode of the diode is used for the voltage or which electrical contact is used. The controller 310 can be configured to keep the second voltage comparator 302, the counter 320, and any other circuitry not needed for the operation of the first voltage comparator 301 deactivated before the time when the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold value. The time delay can 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 of the voltage is substantially zero” means that the temporal change of the voltage is less than 0.1 % / ns. The phrase “the rate of change of the voltage is substantially not zero” means that the temporal change of the voltage is at least 0.1 % / ns.

[0057] The controller 310 can be configured to activate the second voltage comparator during the time delay, including the start and the expiration. In one embodiment, the controller 310 is configured to activate the second voltage comparator at the start or the expiration 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 a logic level, by providing power, etc.). The term “deactivate” means to bring a component into a non-operational state (e.g., by sending a signal such as a voltage pulse or a logic level, by cutting off power, etc.). The operational state can have a higher power consumption than the non-operational state (e.g., 10 times, 100 times, 1000 times the power consumption of the non-operational state). The controller 310 itself can be deactivated until the output of the first voltage comparator 301 activates the controller 310 when the absolute value of the voltage equals or exceeds the absolute value of the first threshold value.

[0058] The controller 310 can be configured to cause at least one of the quantities recorded by the counter 320 to increase by 1 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 value.

[0059] The controller 310 can be configured to cause the optional voltmeter 306 to measure the voltage at expiration of the time delay. The controller 310 can be configured to connect the electrical contact 119B to electrical ground in order to reset the voltage and discharge any charge carriers accumulated on the electrical contact 119B. In one embodiment, the electrical contact 119B is connected to electrical ground after expiration of the time delay. In an embodiment, the electrical contact 119B is connected to electrical ground for a limited reset time period. The controller 310 can connect the electrical contact 119B to electrical ground by controlling a switch 305. The switch can be a transistor such as a field effect transistor (FET).

[0060] In one embodiment, the system 121 does not have an analog filter network (e.g., an RC network). In an embodiment, the system 121 does not have analog circuitry.

[0061] The voltmeter 306 can feed its measured voltage to the controller 310 as an analog or digital signal.

[0062] The electronic system 121 can include an integrator 309 electrically connected to the electrical contact 119B, where the integrator is configured to collect charge carriers from the electrical contact 119B. The integrator 309 can include a capacitor in the feedback path of an amplifier. An amplifier so configured is called a capacitance transimpedance amplifier (CTIA). A CTIA has a high dynamic range by preventing the amplifier from saturating, and improves signal-to-noise ratio by limiting the bandwidth in the signal path. Charge carriers from the electrical contact 119B accumulate on the capacitor over a time period (“integration period”). After expiration of the integration period, the capacitor voltage is sampled and then the capacitor voltage is reset by a reset switch. The integrator 309 can include a capacitor directly connected to the electrical contact 119B.

[0063] FIG. 8The diagram schematically illustrates the time-varying current (upper curve) flowing through electrical contact 119B caused by charge carriers generated by X-ray photons incident on pixel 150 surrounding electrical contact 119B, and the corresponding time-varying voltage of electrical contact 119B (lower curve). Voltage can be the integral of current relative to time. At time t0, X-ray photons strike pixel 150, charge 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 t1, a first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of a first threshold V1, controller 310 begins a time delay TD1, and controller 310 may deactivate the first voltage comparator 301 at the start of TD1. If controller 310 is deactivated before t1, controller 310 is activated at t1. During TD1, controller 310 activates a second voltage comparator 302. The term "during" as used herein refers to the start and end (i.e., the end) of a period, and any time in between. For example, controller 310 may activate the second voltage comparator 302 when TD1 expires. If, during TD1, the second voltage comparator 302 determines at time t2 that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold V2, then controller 310 waits for the voltage to stabilize. The voltage at time t1 stabilizes as all charge carriers generated by the X-ray photons drift outside the radiation absorption layer 110. e Stable. At time t s The time delay TD1 expires. At time t e Alternatively, controller 310 causes voltmeter 306 to digitize the voltage and determine which interval the X-ray photon energy falls into. Then, controller 310 increments counter 320 by 1 corresponding to the number of records for that interval. FIG. 8 In the example, time t s At time t e Afterwards; that is, after all the charge carriers generated by the X-ray photons have drifted outside the radiation absorption layer 110, TD1 expires. If time t e If it cannot be easily measured, TD1 can be selected empirically to allow sufficient time to collect essentially all the charge carriers generated by the X-ray photon, but not too long, so as to avoid the risk of another X-ray photon. That is, TD1 can be selected empirically, thus allowing time t to be determined empirically. s At time t e After that. Time t s It doesn't necessarily have to be at time t e Subsequently, because controller 310 can ignore TD1 and wait for time t once V2 is reached. e Therefore, the rate of change of the difference between voltage and the contribution of dark current to voltage is in t eThe voltage at the electric contact 119B is substantially zero. The controller 310 can be configured to deactivate the second voltage comparator 302 at the expiration of TD1 or at t2 or at any time in between.

[0064] At time t e The voltage is proportional to the amount of charge carriers generated by the X-ray photon, which is related to the energy of the X-ray photon. The controller 310 can be configured to determine the energy of the X-ray photon using the voltmeter 306.

[0065] After the expiration of TD1 or the digitization by the voltmeter 306, whichever is later, the controller 310 connects the electric contact 119B to electrical ground for a reset period RST to allow the charge carriers accumulated on the electric contact 119B to flow to ground and reset the voltage. After RST, the electronic system 121 is ready to detect another incident X-ray photon. If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before the expiration of RST. If the controller 310 has been deactivated, it can be activated before the expiration of RST.

[0066] 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 are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. An image sensor, comprising: Multiple X-ray detectors; An actuator is configured to move the plurality of X-ray detectors to a plurality of positions along one direction, wherein the image sensor is configured to capture images of portions of the scene at the respective positions using the X-ray detectors; A mask with multiple X-ray transmission zones, The X-ray transmission region is configured to form spatially discontinuous exposure areas on the image sensor, and the formed exposure areas are configured such that each image of the portion has at least one edge at an angle to the direction, and the X-ray intensity outside the exposure areas is substantially zero; and The image sensor is configured to form an image of the scene by stitching together the images of the portions thereof.

2. The image sensor according to claim 1, wherein, The multiple X-ray detectors are spaced apart.

3. The image sensor according to claim 1, wherein, The effective area of ​​the image sensor is within the exposure area.

4. The image sensor according to claim 1, wherein, The change in X-ray intensity across the periphery of the exposed area is smooth.

5. The image sensor according to claim 1, wherein, The actuator is configured to move the mask such that the X-ray detector remains aligned with the exposure area at the location.

6. The image sensor according to claim 1, wherein, At least some of the plurality of X-ray detectors are arranged in staggered rows.

7. The image sensor according to claim 6, wherein, The X-ray detectors in the same row are of the same size; wherein the distance between two adjacent X-ray detectors in the same row is greater than the width of one X-ray detector in the row in the direction of extension of the row, and less than twice that width.

8. The image sensor according to claim 1, wherein, The actuator includes a robotic arm.

9. The image sensor according to claim 1, wherein, At least some of the plurality of X-ray detectors include multilayer detectors.

10. The image sensor according to claim 1, wherein, At least some of the plurality of X-ray detectors are rectangular in shape.

11. The image sensor according to claim 1, wherein, At least some of the plurality of X-ray detectors are hexagonal in shape.

12. The image sensor according to claim 1, wherein, At least some of the plurality of X-ray detectors are right-angled trapezoidal in shape.

13. The image sensor according to claim 1, wherein, The actuator includes a control unit configured to determine the position.

14. An imaging device comprising an image sensor and an X-ray source as claimed in claim 1.

Images