Imaging device

Abstract

Disclosed herein is a device (9000), comprising: a radiation detector (100); a collimator (101); wherein the collimator (101) and the radiation detector (100) are configured to translate together relative to a radiation source (109) along a direction (905) without relative motion between the collimator (101) and the radiation detector (100); wherein the collimator (101) comprises a plurality of planar plates parallel to each other; and wherein the planar plates are not parallel to the direction (905).

Description

[Background Technology]

[0001] A radiation detector may be a device used to measure the flux, spatial distribution, spectrum, or other properties of radiation.

[0002] Radiation detectors are used in many applications. One important application is imaging. Radiation imaging is a radiographic technique that can be used to reveal the internal structure of opaque objects with inhomogeneous composition, such as the human body.

[0003] Early radiation detectors used for imaging included photographic plates and photographic film. Photographic plates can be glass plates coated with a light-sensitive emulsion. Although photographic plates have been superseded by photographic film, they are still used in specialized situations due to their superior quality and extreme stability. Photographic film can be plastic film (e.g., strips or sheets) coated with a light-sensitive emulsion.

[0004] In the 1980s, photosensitizable phosphor plates (PSP plates) became available. PSP plates can contain phosphor materials with color centers in their crystal lattice. When the PSP plate is exposed to radiation, electrons excited by the radiation are trapped in the color centers until they are excited by a laser beam scanned across the plate surface. 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 type of radiation 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, radiation image intensifiers can produce real-time images, that is, no post-exposure processing is required to produce an image. The radiation first strikes an input phosphor (e.g., cesium iodide) and is converted into visible light. The visible light then strikes a photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes electron emission. The number of electrons emitted is proportional to the intensity of the incident radiation. The emitted electrons are projected onto an output phosphor through electron optics and cause the output phosphor to produce a visible light image.

[0006] Scintillators operate somewhat similarly to radiation image intensifiers, in that the scintillator (e.g., sodium iodide) absorbs radiation and emits visible light, which can then be detected by a suitable image sensor for visible light. Within the scintillator, visible light diffuses and scatters in all directions, reducing spatial resolution. Reducing scintillator thickness helps improve spatial resolution but also reduces radiation absorption. Scintillators therefore must achieve a compromise between absorption efficiency and resolution.

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

[0008] Disclosed herein is an apparatus comprising: a radiation detector; a collimator; wherein the collimator and the radiation detector are configured to translate together along a direction relative to a radiation source without relative motion between the collimator and the radiation detector; wherein the collimator comprises a plurality of planar plates parallel to each other; and wherein the planar plates are not parallel to the direction.

[0009] According to an embodiment, the angle between the planar plate and the direction is less than 5 degrees, 10 degrees, 25 degrees or 45 degrees.

[0010] According to an embodiment, the planar plate is perpendicular to the radiation receiving surface of the radiation detector.

[0011] According to an embodiment, the collimator and the radiation detector are configured to be jointly moved to a plurality of positions relative to the radiation source by translation relative to the radiation source along the direction.

[0012] According to an embodiment, the radiation detector is configured to capture images of portions of the scene at the plurality of positions.

[0013] According to an embodiment, the apparatus is configured to form an image of the scene by stitching together images of the portions.

[0014] According to an embodiment, the radiation detector comprises a pixel array.

[0015] According to an embodiment, the radiation detector is rectangular in shape.

[0016] According to an embodiment, the radiation detector is hexagonal in shape.

[0017] According to an embodiment, the radiation detector is configured to count a plurality of numbers of radiation particles incident on the plurality of pixels over a period of time.

[0018] According to an embodiment, said radiation particles are X-ray photons.

[0019] According to an embodiment, the radiation detector includes: a radiation absorbing layer including an electrical contact; a first voltage comparator configured to compare the voltage of the electrical contact with a first threshold; a second voltage comparator configured to compare the voltage with a second threshold; a counter configured to record at least one of the multiple quantities; a controller, wherein the controller is configured to start a time delay from the time when the first voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during the time delay; wherein the controller is configured to: when the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold, increase at least one of the multiple quantities by 1.

[0020] According to an embodiment, the apparatus further comprises an integrator electrically connected to the electrical contacts, wherein the integrator is configured to collect charge carriers from the electrical contacts.

[0021] According to an embodiment, the controller is configured to activate the second voltage comparator when the time delay starts or expires.

[0022] According to an embodiment, the controller is configured to connect the electrical contact to electrical ground.

[0023] According to an embodiment, upon expiration of the time delay, the rate of change of the voltage is substantially zero.

[0024] According to an embodiment, the radiation detector does not comprise a scintillator.

Brief Description of the Drawings

[0025] Figure 1A Schematically illustrates a perspective view of an apparatus translating in one direction according to an embodiment.

[0026] Figure 1B Schematically shows a top view of a portion of a device translated along a direction according to an embodiment.

[0027] Figure 2 An apparatus for capturing multiple images of a portion of a scene according to an embodiment is schematically shown.

[0028] Figures 3A to 3C The arrangement of radiation detectors in an apparatus according to some embodiments is schematically shown.

[0029] Figure 4 An arrangement with a plurality of hexagonally shaped radiation detectors according to an embodiment is schematically shown.

[0030] Figure 5 A radiation detector according to an embodiment is schematically shown having a pixel array.

[0031] Figure 6A A cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0032] Figure 6B A detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0033] Figure 6C An alternative detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0034] Figure 7A and Figure 7B Each shows a Figure 6A 、 Figure 6B and Figure 6C Component diagram of the radiation detector's electronic system.

[0035] Figure 8 Schematically shown are the time variation of a current flowing through an electrical contact of an electrode of a diode or a resistor exposed to radiation of a radiation absorbing layer according to an embodiment (upper curve), and the corresponding time variation of the voltage of the electrode (lower curve), the current being caused by charge carriers generated by radiation particles incident on the radiation absorbing layer. [Specific implementation method]

[0036] Figure 1A Schematically illustrates a perspective view of an apparatus 9000 translated along direction 905 according to an embodiment. The apparatus 9000 may include a radiation detector 100 and a collimator 101. The collimator 101 may be located between the radiation detector 100 and the radiation source 109. The collimator 101 may include a plurality of planar plates (e.g., Figure 1B In the example, as shown in FIG. Figure 1A As shown, radiation from radiation source 109 reaches scene 50 (e.g., a human body part) before passing through collimator 101 and reaching radiation detector 100. In examples, radiation incident on scene 50 may be partially transmitted through scene 50. Collimator 101 is configured to allow the transmitted portion of the radiation to reach radiation detector 100 and substantially prevent portions of the radiation scattered by scene 50 from reaching radiation detector 100.

[0037] In an embodiment, the collimator 101 and the radiation detector 100 are configured to translate together relative to the radiation source 109 along the direction 905 without relative motion between the collimator 101 and the radiation detector 100. Figure 1AIn the example shown, the collimator 101 and the radiation detector 100 can be translated together along a direction 905 relative to the radiation source 109 to a plurality of positions, such as a first position 910 and a second position 920. During the translation and at the plurality of positions, the collimator 101 can remain stationary relative to the radiation detector 100. In one embodiment, when the radiation detector 100 and the collimator 101 are co-located at the plurality of positions relative to the radiation source 109 along the direction 905, a plurality of sets of images of portions of the scene 50 are respectively captured.

[0038] Figure 1B Schematically illustrates a top view of a portion of apparatus 9000 translated along direction 905 according to an embodiment. Figure 1B As shown, the planar plate 501 of the collimator 101 can be perpendicular to the radiation receiving surface of the radiation detector 100. In one embodiment, the planar plate 501 is not parallel to the direction 905, but is at a small angle 901 relative to the direction 905. In an embodiment, the planar plate 501 is not perpendicular to the direction 905. The angle 901 can be less than 5 degrees, 10 degrees, 25 degrees, or 45 degrees.

[0039] Figure 2 Schematically illustrated is an apparatus 9000 for capturing multiple images of a portion of a scene 50 according to an embodiment. Figure 1A and Figure 1B In the example shown, the radiation detector 100 and the collimator 101 can be translated together to two positions 910 and 920. At positions 910 and 920, images 51A and 51B of a portion of the scene 50 can be captured, respectively. In the example, the portion of the scene 50 in image 51A can substantially overlap with the portion of the scene 50 in image 51B. The apparatus 9000 can stitch the images 51A and 51B to form an image 52A of the scene 50. There can be an overlap between the images 51A and 51B to facilitate stitching. In the example, the planar plate 501 of the collimator 101 blocks different portions of the scene 50 at positions 910 and 920, which results in Figure 2 , but positions 910 and 920 result in different occluded portions. Each portion of scene 50 may be included in at least one of the images captured when radiation detector 100 is at multiple positions. That is, the images of the portions, when stitched together, may cover the entire scene 50.

[0040] like Figures 3A to 3C As shown, the apparatus may include a plurality of radiation detectors 100 arranged in various ways. Figure 3AA schematic diagram illustrates an arrangement according to an embodiment, in which radiation detectors 100 are arranged in staggered rows. For example, radiation detectors 100A and 100B are aligned in the Y direction and are of uniform size in the same row; radiation detectors 100C and 100D are aligned in the Y direction and are of uniform size in the same row. Radiation detectors 100A and 100B are staggered in the X direction relative to radiation detectors 100C and 100D. According to an embodiment, the distance X2 between two adjacent radiation detectors 100A and 100B in the same row is greater than the width X1 (i.e., the dimension in the X direction, which is the direction in which the row extends) of a radiation detector in the same row and less than twice the width X1. Radiation detectors 100A and 100E are aligned in the X direction and are of uniform size in the same column; the distance Y2 between two adjacent radiation detectors 100A and 100E in the same column is less than the width Y1 (i.e., the dimension in the Y direction) of a radiation detector in the same column.

[0041] Figure 3B Another arrangement according to an embodiment is schematically shown, in which the radiation detectors 100 are arranged in a rectangular grid. For example, the radiation detectors 100 may include: Figure 3A The radiation detectors 100A, 100B, 100E and 100F are precisely arranged in the Figure 3A The radiation detectors 100C, 100D, 100G, or 100H in FIG. This arrangement allows for imaging of a scene by capturing images of portions of the scene at six locations. For example, three locations spaced apart in the X direction and three additional locations spaced apart in the X direction and spaced apart from the first three locations in the Y direction.

[0042] Other arrangements are possible. For example, Figure 3C In the embodiment, the radiation detectors 100 can span the entire width in the X direction, wherein the distance Y2 between two adjacent radiation detectors 100 is less than the width of one radiation detector Y1. Assuming that the width of the detectors in the X direction is greater than the width of the scene in the X direction, the image of the scene can be stitched together from two images of the scene portion captured at two positions spaced apart in the Y direction.

[0043] The radiation detectors 100 may be of any suitable size and shape. According to an embodiment, at least some of the radiation detectors are rectangular in shape. According to an embodiment, Figure 4 As shown, at least some of the radiation detectors are hexagonal in shape.

[0044] Figure 5The radiation detector 100 is schematically shown as having a pixel array 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 radiation particles incident on it, measure the energy of the radiation particles, or both detect and measure. For example, each pixel 150 can be configured to count the number of radiation particles incident on it whose energy falls within multiple intervals over a period of time. All pixels 150 can be configured to count the number of radiation particles incident on them within multiple energy intervals over the same period of time. Each pixel 150 can 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 can have a resolution of 10 bits or higher. Each pixel 150 can be configured to measure its dark current, for example before or simultaneously with each radiation particle incident on it. Each pixel 150 can be configured to subtract the contribution of the dark current from the energy of the radiation particles incident on it. 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 may be waiting for another radiation particle to arrive. The pixels 150 may be, but need not be, individually addressable. The radiation particle may be an X-ray photon.

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

[0046] like Figure 6B As shown in the detailed cross-sectional view of the radiation detector 100 in , according to an embodiment, the radiation absorbing layer 110 may include one or more diodes (e.g., pin or pn) formed by one or more discrete regions 114 of a first doping region 111, a second doping region 113. The second doping region 113 may be separated from the first doping region 111 by an optional intrinsic region 112. The discrete regions 114 are separated from each other by the first doping region 111 or the intrinsic region 112. The first doping region 111 and the second doping region 113 have opposite doping types (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 6BIn the example of , 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. Figure 6B In the example of FIG, the radiation absorbing layer 110 has a plurality of diodes having the first doping region 111 as a common electrode. The first doping region 111 may also have discrete portions.

[0047] When a radiation particle strikes the radiation-absorbing layer 110 comprising a diode, the radiation particle is absorbed and generates one or more charge carriers through various mechanisms. The radiation particle can generate 10 to 100,000 charge carriers. The charge carriers can drift to one of the diode's electrodes under an electric field. The field can be an external electric field. Electrical contact 119B can include discrete portions, each of which is in electrical contact with a discrete region 114. In embodiments, the charge carriers can drift in various directions such that charge carriers generated by a single radiation particle are not substantially shared by two different discrete regions 114 (where "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 a radiation particle incident around the footprint of one of these discrete regions 114 are not substantially shared by another of these discrete regions 114. A pixel 150 associated with a discrete region 114 may 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 radiation particles incident thereon at an angle of incidence of 0° flow toward the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of these charge carriers flow through the pixel.

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

[0049] When a radiation particle strikes radiation absorbing layer 110, which includes a resistor but not a diode, it is absorbed and generates one or more charge carriers through various mechanisms. The radiation particle can generate between 10 and 100,000 charge carriers. The charge carriers can drift to electrical contacts 119A and 119B under an electric field. This field can be an external electric field. Electrical contact 119B includes discrete portions. In embodiments, the 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 portions of electrical contact 119B (where "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 a radiation particle incident around the footprint of one of these discrete portions of electrical contact 119B are substantially not shared by another of these discrete portions of electrical contact 119B. A pixel 150 associated with a discrete portion of electrical contact 119B can be a region 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 radiation particles incident thereon at an angle of incidence of 0° 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.

[0050] The electronic device layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation particles incident on the radiation absorbing layer 110. The electronic system 121 may include analog circuits such as filter networks, amplifiers, integrators, and comparators, or digital circuits such as microprocessors and memories. The electronic system 121 may include components shared by each pixel or components dedicated to a single pixel. For example, the electronic system 121 may include an amplifier dedicated to each pixel and a microprocessor shared between all 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 filling material 130, which may increase the mechanical stability of the connection between the electronic device layer 120 and the radiation absorbing layer 110. Other bonding techniques may connect the electronic system 121 to the pixels without using vias.

[0051] Figure 7A and Figure 7B 3 and 4 show component diagrams of the electronic system 121 according to an embodiment. The electronic system 121 may include a first voltage comparator 301 , a second voltage comparator 302 , a counter 320 , a switch 305 , an optional voltmeter 306 , and a controller 310 .

[0052] The first voltage comparator 301 is configured to compare the voltage of at least one electrical contact 119B with a first threshold. The first voltage comparator 301 can be configured to monitor the voltage directly or calculate the voltage by integrating the 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 the maximum voltage that an incident radiation particle would generate at the electrical contact 119B. The maximum voltage can depend on the energy of the incident radiation particle, the material of the radiation absorbing layer 110, and other factors. For example, the first threshold 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 calculate the voltage by integrating the 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 terms "absolute value" or "modulus" |x| of a real number x refers to 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 the maximum voltage that an incident radiation particle would generate at the electrical contact 119B. For example, the second threshold value may be 100 mV, 150 mV, 200 mV, 250 mV, 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 can compare a voltage to two different threshold values at different times.

[0054] The first voltage comparator 301 or the second voltage comparator 302 may include one or more operational amplifiers or any other suitable circuits. The first voltage comparator 301 or the second voltage comparator 302 may have high speed to allow the electronic system 121 to operate under a high flux of incident radiation particles. However, high speed generally comes at the expense of power consumption.

[0055] Counter 320 is configured to record at least the number of radiation particles incident on pixels 150 surrounding electrical contact 119B. Counter 320 can be a software component (e.g., a number stored in computer memory) or a hardware component (e.g., 4017 IC and 7490 IC).

[0056] Controller 310 can be a hardware component, such as a microcontroller or microprocessor. Controller 310 is configured to initiate a time delay from the time the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of a first threshold (e.g., the absolute value of the voltage increases from an absolute value below the first threshold to a value equal to or above the absolute value of the first threshold). Absolute values are used here because the voltage can be negative or positive, depending on whether the voltage at the cathode or anode of the diode is used or which electrical contact is used. Controller 310 can be configured to deactivate second voltage comparator 302, counter 320, and any other circuitry not required for the operation of first voltage comparator 301 before the time 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 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 variation of the voltage is less than 0.1% / ns. The phrase "the rate of change of the voltage is not substantially zero" means that the temporal variation 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 expiration). In an embodiment, the controller 310 is configured to activate the second voltage comparator at the start of the time delay. The term "activate" means to put the component into an operating state (e.g., by sending a signal such as a voltage pulse or logic level, by providing power, etc.). The term "deactivate" means to put the component into a non-operating state (e.g., by sending a signal such as a voltage pulse or logic level, by cutting off power, etc.). The operating state can have a higher power consumption than the non-operating state (e.g., 10 times, 100 times, 1000 times that of the non-operating 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.

[0058] The controller 310 may be configured to increment at least one number recorded by the counter 320 by one 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.

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

[0060] In an embodiment, system 121 has no analog filter networks (eg, RC networks). In an embodiment, system 121 has no analog circuitry.

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

[0062] The electronic system 121 may include an integrator 309 electrically connected to the electrical contact 119B, wherein the integrator is configured to collect charge carriers from the electrical contact 119B. The integrator 309 may include a capacitor in the feedback path of the amplifier. An amplifier configured in this way is called a capacitive transimpedance amplifier (CTIA). The 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. Over a period of time ("integration period"), charge carriers from the electrical contact 119B accumulate on the capacitor. After the integration period expires, the capacitor voltage is sampled and then reset by a reset switch. The integrator 309 may include a capacitor directly connected to the electrical contact 119B.

[0063] Figure 8The diagram schematically illustrates the temporal variation of current flowing through electrical contact 119B (upper curve) caused by charge carriers generated by radiation particles incident on pixel 150 surrounding electrical contact 119B, and the corresponding temporal variation of the voltage at electrical contact 119B (lower curve). Voltage can be the integral of current with respect to time. At time t0, a radiation particle strikes 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, first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of first threshold V1, and controller 310 begins time delay TD1. Controller 310 may deactivate first voltage comparator 301 at the start of TD1. If controller 310 was deactivated before t1, controller 310 is activated at t1. During TD1, controller 310 activates second voltage comparator 302. As used herein, the term "during" means the beginning and expiration (i.e., the end) and any time therebetween. For example, the 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 value V2, the controller 310 waits for the voltage to stabilize and settle. When all charge carriers generated by the radiation particles drift out of the radiation absorbing layer 110, the voltage stabilizes at time te. At time ts, the time delay TD1 expires. At or after time te, the controller 310 causes the voltmeter 306 to digitize the voltage and determine which interval the energy of the radiation particle falls into. The controller 310 then causes the counter 320 to add 1 to the number recorded corresponding to the interval. During Figure 8 In the example shown, time ts is after time te; that is, TD1 expires after all charge carriers generated by the radiation particle have drifted out of the radiation absorbing layer 110. If time te cannot be easily measured, TD1 can be empirically selected to allow sufficient time to collect substantially all charge carriers generated by the radiation particle, but not so long as to risk another incident radiation particle. That is, TD1 can be empirically selected so that time ts is empirically determined to be after time te. Time ts does not necessarily need to be after time te, as the controller 310 can ignore TD1 and wait for time te once V2 is reached. Therefore, the rate of change of the difference between the voltage and the dark current contribution to the voltage is substantially zero at te. The controller 310 can be configured to deactivate the second voltage comparator 302 at the expiration of TD1, at t2, or at any time therebetween.

[0064] The voltage at time te is proportional to the amount of charge carriers generated by the irradiated particle, which is related to the energy of the irradiated particle. The controller 310 may be configured to determine the energy of the irradiated particle using the voltmeter 306.

[0065] After TD1 expires or the voltmeter 306 is digitized (whichever is later), the controller 310 connects the electrical contact 119B to electrical ground during a reset period RST to allow the charge carriers accumulated on the electrical contact 119B to flow to ground and reset the voltage. After RST, the electronic system 121 is ready to detect another incident radiation particle. If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before the RST expires. If the controller 310 has been deactivated, it can be activated before the RST expires.

[0066] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for 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 imaging device comprising: Radiation detectors; collimator; wherein the collimator is located between the radiation detector and the scene; wherein the collimator and the radiation detector are configured to translate jointly along a direction relative to a radiation source without relative motion between the collimator and the radiation detector; wherein the collimator comprises a plurality of planar plates parallel to each other; and The plane plate is not parallel to the direction, and the plane plate is not perpendicular to the direction.

2. The imaging device according to claim 1, wherein The angle between the planar plate and the direction is less than 5 degrees, 10 degrees, 25 degrees or 45 degrees.

3. The imaging device according to claim 1, wherein The planar plate is perpendicular to the radiation receiving surface of the radiation detector.

4. The imaging device according to claim 1, wherein The collimator and the radiation detector are configured to be jointly moved to a plurality of positions by translation along the direction relative to the radiation source.

5. The imaging device according to claim 4, wherein The imaging device is configured to capture images of portions of the scene at the plurality of locations.

6. The imaging device according to claim 5, wherein The imaging device is configured to form an image of the scene by stitching the images of the portions.

7. The imaging device according to claim 1, wherein The radiation detector includes an array of pixels.

8. The imaging device according to claim 1, wherein The radiation detector is rectangular in shape.

9. The imaging device according to claim 1, wherein The radiation detector is hexagonal in shape.

10. The imaging device according to claim 7, wherein The radiation detector is configured to count a plurality of numbers of radiation particles incident on a plurality of pixels over a period of time.

11. The imaging apparatus of claim 10, wherein the radiation particles are X-ray photons.

12. The imaging device according to claim 10, wherein The radiation detector comprises: a radiation absorbing layer including electrical contacts; a first voltage comparator configured to compare the voltage of the electrical contact with a first threshold; a second voltage comparator configured to compare the voltage with a second threshold; a counter configured to record at least one of the plurality of quantities; Controller; wherein the controller is configured to start the time delay from the time when the first voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during the time delay; The controller is configured to, when the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold, increase at least one of the plurality of numbers by 1.

13. The imaging device of claim 12, further comprising an integrator electrically connected to the electrical contacts, wherein The integrator is configured to collect charge carriers from the electrical contacts.

14. The imaging device according to claim 12, wherein The controller is configured to activate the second voltage comparator when the time delay begins or expires.

15. The imaging device according to claim 12, wherein The controller is configured to connect the electrical contact to electrical ground.

16. The imaging device according to claim 12, wherein At the expiration of the time delay, the rate of change of the voltage is substantially zero.

17. The imaging device according to claim 1, wherein The radiation detector does not include a scintillator.

Images