Imaging method

Abstract

Disclosed herein is a method comprising: moving an image sensor (9000) along a first direction (951) between a plurality of positions (910, 920) relative to a scene (50) and capturing partial images (1010, 1020) of the scene (50) at the plurality of positions (910, 920), respectively; forming an image (1030) of the scene (50) from the partial images (1010, 1020); wherein the image sensor (9000) has an active area (190) and a dead zone (195); wherein the dead zone (195) extends along a second direction (952); wherein the second direction (952) is at an angle (953) to the first direction (951); wherein when the image sensor (9000) is located at the plurality of positions (910, 920), each point in the scene (50) falls on the dead zone (195) no more than once.

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 Although photographic plates have been superseded by photographic film, they are still used in specialized situations due to their superior quality and extreme stability.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 vacuum sealed. Compared to photographic plates, photographic film, and PSP plates, a radiation image intensifier 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 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 a method comprising: moving an image sensor between a plurality of positions relative to a scene along a first direction, and capturing partial images of the scene at the plurality of positions respectively; forming an image of the scene from the partial images; wherein the image sensor has an active area and a dead zone; wherein the dead zone extends along a second direction; wherein the second direction forms an angle with the first direction; wherein when the image sensor is located at the plurality of positions, each point in the scene falls on the dead zone no more than once.

[0009] According to an embodiment, the dead zone extends across the active area.

[0010] According to an embodiment, the dead zone divides the active area into a plurality of spatially discontinuous parts.

[0011] According to an embodiment, the image sensor includes a plurality of radiation detectors.

[0012] According to an embodiment, the dead zone is part of a guard ring of the radiation detector.

[0013] According to an embodiment, the plurality of radiation detectors overlap each other.

[0014] According to an embodiment, at least one of the plurality of radiation detectors has an edge parallel to the first direction.

[0015] According to an embodiment, the method further comprises forming a projection of a guard ring in the first image and in the second image.

[0016] According to an embodiment, the image sensor comprises a plurality of pixels; wherein the image sensor is configured to count the number of radiation particles incident on the pixels over a period of time.

[0017] According to an embodiment, said radiation particles are X-ray photons.

[0018] According to an embodiment, at least one of the radiation detectors includes: a radiation absorbing layer including an electrical contact; a first voltage comparator, the first voltage comparator being configured to compare the voltage of the electrical contact with a first threshold; a second voltage comparator, the second voltage comparator being configured to compare the voltage with a second threshold; a counter, the counter being configured to record the number of radiation photons or particles reaching the radiation absorbing layer; 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 increase the number recorded by the counter by 1 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.

[0019] According to an embodiment, the image sensor further comprises an integrator electrically connected to the electrical contacts, wherein the integrator is configured to collect charge carriers from the electrical contacts.

[0020] According to an embodiment, the controller is configured to activate the second voltage comparator when the time delay starts or expires.

[0021] According to an embodiment, the controller is configured to connect the electrical contact to electrical ground.

[0022] According to an embodiment, upon expiration of the time delay, the rate of change of the voltage is substantially zero.

[0023] According to an embodiment, the radiation absorbing layer comprises a diode.

[0024] According to an embodiment, the radiation absorbing layer comprises single-crystalline silicon.

[0025] According to an embodiment, the image sensor does not comprise a scintillator.

Brief Description of the Drawings

[0026] Figure 1 A method of moving an image sensor between a plurality of positions relative to a scene along a first direction and capturing partial images of the scene at the plurality of positions according to an embodiment is schematically illustrated.

[0027] Figure 2A An image sensor including a plurality of radiation detectors according to an embodiment is schematically illustrated.

[0028] Figure 2B Schematically shows a top view of a first radiation detector and a second radiation detector according to an embodiment.

[0029] Figures 2C to 2DEach schematically shows a side view of two different arrangements of radiation detectors of an image sensor according to an embodiment.

[0030] Figure 3 It is schematically shown that an image sensor according to an embodiment captures a plurality of partial images of a scene portion.

[0031] Figure 4 It is schematically shown that a radiation detector according to an embodiment may have a pixel array.

[0032] Figure 5A A cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0033] Figure 5B A detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0034] Figure 5C An alternative detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0035] Figure 6A and Figure 6B Each shows a Figure 5A 、 Figure 5B and Figure 5C Component diagram of the radiation detector's electronic system.

[0036] Figure 7 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]

[0037] Figure 1 The method according to an embodiment is schematically shown. The method comprises moving the image sensor 9000 between a plurality of positions relative to the scene 50 along a first direction 951 and capturing partial images of the scene 50 at the plurality of positions, respectively.

[0038] exist Figure 1In the example shown, image sensor 9000 can be moved along first direction 951 from a first position 910 to a second position 920 relative to scene 50. In one embodiment, at first position 910 relative to scene 50, image sensor 9000 uses radiation from radiation source 109 that has passed through scene 50 to capture a partial image 1010 of a portion of scene 50; and at second position 920 relative to scene 50, image sensor 9000 uses radiation from radiation source 109 that has passed through scene 50 to capture another partial image 1020 of the portion of scene 50. Image sensor 9000 may include a plurality of radiation detectors configured to receive radiation incident thereon from radiation source 109.

[0039] Figures 2A to 2D The image sensor 9000 according to an embodiment may include a plurality of radiation detectors 100 (eg, a first radiation detector 100A, a second radiation detector 100B) and may include a support 107 such as a printed circuit board (PCB). Figure 2A Schematically shows a top view of a portion of an image sensor 9000 according to an embodiment. A plurality of radiation detectors 100 may be arranged on a flat surface of a support 107 . Figures 2C to 2D Schematically shows side views of two different arrangements of radiation detectors 100 of an image sensor 9000 according to one embodiment. Figure 2C In the example shown, a plurality of radiation detectors 100 may be mounted on a support 107, and the radiation receiving surface of each radiation detector may be inclined relative to the flat surface of the support 107. The plurality of radiation detectors 100 may overlap with each other. Figure 2D In the example shown, a plurality of radiation detectors 100 may be mounted on a bracket 107 , and a radiation receiving surface of each radiation detector may be parallel to a flat surface of the bracket 107 .

[0040] Figure 2B Schematically shows a top view of a first radiation detector 100A and a second radiation detector 100B according to an embodiment. The first radiation detector 100A may be arranged in a different orientation than the second radiation detector 100B. Figure 2BIn the example shown, the first radiation detector 100A may have an edge 921 parallel to a first direction 951. In one embodiment, the image sensor 9000 includes at least one first radiation detector 100A. The second radiation detector 100B may be tilted relative to the first direction 951 such that one edge 921 of the second radiation detector 100B may be parallel to a second direction 952. According to one embodiment, the second direction 952 is not parallel to the first direction 951. The second direction 952 may be at an angle 953 (e.g., greater than 10 degrees, 20 degrees, or 30 degrees, etc.) relative to the first direction 951. As used herein, "at an angle" means not parallel or perpendicular.

[0041] According to an embodiment, the radiation detector 100 (eg Figure 2B ) have an active area 190 and a dead zone 195, respectively. The active area 190 may include a plurality of pixels 150, so that when the radiation detector 100 receives radiation from the radiation source 109 that has passed through the scene 50, the pixels 150 can detect incident particles of the radiation. The dead zone 195 may be a peripheral area around the radiation receiving surface of the radiation detector 100 that does not include pixels, so that radiation particles incident in the dead zone 195 may not be detected by the radiation detector 100. In one embodiment, the dead zone 195 is also part of the guard ring of the radiation detector 100. The dead zone 195 may extend across the active area 190 in each radiation detector, respectively. In one embodiment, when a plurality of radiation detectors 100 (e.g., 100A, 100B, etc.) are arranged together to form a Figure 2A In the illustrated image sensor 9000, the active area of the image sensor 9000 is divided into a plurality of spatially discontinuous portions by a dead zone 195. The dead zone of the image sensor 9000 may include the dead zone of the radiation detector 100 and any gaps between the radiation detectors 100. The active area of the image sensor 9000 is a combination of the active areas 190 of the radiation detectors 100.

[0042] Figure 3 Schematically, an image sensor 9000 according to an embodiment is shown capturing multiple images of portions of a scene 50. Figure 3 In the example shown, an image sensor 9000 including a plurality of radiation detectors 100 can be moved relative to a scene 50 along a first direction 951 from a position 910 to a position 920. The image sensor 9000 can capture partial images 1010 and 1020 of portions of the scene 50 at positions 910 and 920, respectively. The image sensor 9000 can stitch the partial images 1010 and 1020 together to form an image 1030 of the entire scene 50. The dead zone of the image sensor 9000 leaves gaps in the partial images 1010 and 1020. Figure 3In the example shown, according to an embodiment, when image sensor 9000 is at position 910, the dead zone leaves a gap 1015 in partial image 1010; when image sensor 9000 is at position 920, the dead zone leaves a gap 1025 in partial image 1020. In one embodiment, image sensor 9000 moves from position 910 to position 920 according to a minimum step size 1040, such that each point in scene 50 falls within the dead zone of image sensor 9000 no more than once when image sensor 9000 is at multiple positions. Therefore, when image sensor 9000 is at position 920, points of scene 50 that fall within the dead zone of image sensor 9000 at position 910 can be captured by image sensor 9000. Maintaining the minimum step size 1040 for each movement of image sensor 9000 along first direction 951, an image 1030 of the entire scene 50 can be formed by combining the partial images (i.e., 1010, 1020, etc.) captured by image sensor 9000 at multiple positions.

[0043] Figure 4 The radiation detector 100 according to an embodiment 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 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.

[0044] Figure 5AA cross-sectional view of one of the radiation detectors 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 one embodiment, the radiation detector 100 of the image sensor 9000 does not include a scintillator. The radiation absorbing layer 110 may include a semiconductor material, such as silicon, germanium, GaAs, CdTe, CdZnTe, or single crystal silicon. 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.

[0045] like Figure 5B 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 5B In 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 5B In the example of FIG, the radiation absorbing layer 110 has a plurality of diodes having a first doped region 111 as a common electrical contact. The first doped region 111 may also have discrete portions.

[0046] When a radiation particle strikes the radiation absorbing layer 110 comprising a diode, the radiation particle may be absorbed and generate one or more charge carriers through various mechanisms. The radiation particle may generate 10 to 100,000 charge carriers. The charge carriers may drift under an electric field to an electrical contact of one of the diodes. The field may be an external electric field. Electrical contact 119B may include discrete portions, each of which is in electrical contact with a discrete region 114. In embodiments, the charge carriers may 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.

[0047] like Figure 5C 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.

[0048] When a radiation particle strikes radiation absorbing layer 110, which includes a resistor but not a diode, it can be absorbed and generate 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 electrical contacts 119A and 119B under an electric field. The 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.

[0049] 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.

[0050] Figure 6A and Figure 6B 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 .

[0051] 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 can generate on 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.

[0052] The second voltage comparator 302 is configured to compare the voltage with a second threshold. The second voltage comparator 302 can be configured to directly monitor the voltage 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 without regard to 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 can 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.

[0053] 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.

[0054] Counter 320 is configured to record the number of radiation particles incident on radiation absorbing layer 110 including pixel 150. Counter 320 may be a software component (e.g., a number stored in computer memory) or a hardware component (e.g., 4017 IC and 7490 IC).

[0055] 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). The term "absolute value" is 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 becomes 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.

[0056] The controller 310 can be configured to activate the second voltage comparator during the time delay (including the start and expiration). In one embodiment, the controller 310 is configured to activate the second voltage comparator when the time delay starts or expires. 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.

[0057] The controller 310 may be configured to increment at least one of the quantities recorded by the counter 320 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.

[0058] 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 one 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).

[0059] In one embodiment, system 121 has no analog filter networks (eg, RC networks). In one embodiment, system 121 has no analog circuitry.

[0060] The voltmeter 306 may feed its measured voltage to the controller 310 as an analog or digital signal.

[0061] 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.

[0062] Figure 7The 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 start and expiration (i.e., end) and any time therebetween. For example, the controller 310 may activate the second voltage comparator 302 at the expiration of TD1. 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. When all charge carriers generated by the radiation particles drift outside the radiation absorbing layer 110, the voltage at time t e Stable. At time t s , the time delay TD1 expires. At time t e Or after, the controller 310 makes the voltmeter 306 digitize the voltage and determine which interval the energy of the radiation particle falls into. The controller 310 then makes the counter 320 increase the number recorded corresponding to the interval by 1. Figure 7 In the example, time t s At time t e After that; that is, after all the charge carriers generated by the radiation particles drift out of the radiation absorbing layer 110, TD1 expires. e , TD1 can be chosen empirically so that there is enough time to collect substantially all the charge carriers generated by the radiation particle, but not so long as to risk another incident radiation particle. That is, TD1 can be chosen empirically so that the time t s At time t e After that. Time t s Not necessarily at time t e Afterwards, since the controller 310 can ignore TD1 and wait for time t when V2 is reached e Therefore, the rate of change of the difference between the voltage and the dark current contribution to the voltage is eThe controller 310 may be configured to deactivate the second voltage comparator 302 upon expiration of TD1 or at t2 or any time therebetween.

[0063] At time t e The voltage of φ 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 .

[0064] 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.

[0065] 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 method comprising: moving the image sensor between a plurality of positions relative to a scene along a first direction and capturing partial images of the scene at each of the plurality of positions; forming an image of the scene from the partial images; Wherein, the image sensor has an effective area and a dead area; wherein the dead zone extends along the second direction; wherein the second direction is not parallel to the first direction; Wherein, when the image sensor is located at the plurality of positions, each point in the scene falls on the dead zone no more than once.

2. The method according to claim 1, wherein The dead zone extends across the active area.

3. The method according to claim 1, wherein The dead zone divides the active area into a plurality of spatially discontinuous portions.

4. The method according to claim 1, wherein The image sensor includes a plurality of radiation detectors.

5. The method according to claim 4, wherein The dead zone is part of a guard ring of the radiation detector.

6. The method according to claim 4, wherein: The plurality of radiation detectors overlap with each other.

7. The method according to claim 4, wherein: At least one of the plurality of radiation detectors has an edge parallel to the first direction. The method according to claim 1 , further comprising forming a projection of a guard ring in the partial image.

9. The method according to claim 1, wherein The image sensor comprises a plurality of pixels; wherein the image sensor is configured to count the number of radiation particles incident on the pixels over a period of time.

10. The method of claim 9, wherein the radiation particles are X-ray photons.

11. The method according to claim 4, wherein At least one of the radiation detectors 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 a number of radiation particles incident on the radiation absorbing layer; 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 increase the number recorded by the counter by 1 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.

12. The method according to claim 11, wherein The image sensor also includes an integrator electrically connected to the electrical contacts, wherein the integrator is configured to collect charge carriers from the electrical contacts.

13. The method according to claim 11, wherein The controller is configured to activate the second voltage comparator when the time delay begins or expires.

14. The method according to claim 11, wherein The controller is configured to connect the electrical contact to electrical ground.

15. The method according to claim 11, wherein At the expiration of the time delay, the rate of change of the voltage is substantially zero.

16. The method according to claim 11, wherein The radiation absorbing layer includes a diode.

17. The method according to claim 11, wherein The radiation absorbing layer includes single crystal silicon.

18. The method according to claim 11, wherein The image sensor does not include a scintillator.

Images