Imaging system for eliminating effects of dark currents and corresponding operating method

Abstract

Disclosed herein is a method comprising: collecting, for each combination of i and j (i = 1,..., M, and j = 1,..., N), charge (i, 1, j) from a sensing element (i) of the same radiation detector throughout a charge collection period (1, j) using a charge collection device (i, 1), where M and N are positive integers; for each combination of i and j, collecting charge (i, 2, j) from a sensing element (i) of the radiation detector over the entire charge collection period (2, j) by means of charge collection means (i, 2); and determining, for each value of i, a final value of a pixel (i) of the same image based on the charge (i, 1, j) and the charge (i, 2, j). The charge collection periods are discrete from each other such that there is no overlap between them.

Description

Background Art

[0001] A radiation detector is a device that measures properties of radiation. Examples of properties may include the spatial distribution of intensity, phase, and polarization of the radiation. The radiation measured by the radiation detector may be radiation that has passed through an object. The radiation measured by the radiation detector may be electromagnetic radiation, such as infrared light, visible light, ultraviolet light, X-rays, or gamma rays. The radiation may be of other types, such as alpha rays and beta rays. An imaging system may include one or more image sensors, each of which may have one or more radiation detectors. Summary of the invention

[0002] A method is disclosed herein, comprising: for each combination of i and j (i=1, ..., M, and j=1, ..., N), using a charge collection device (i, 1) to collect charges (i, 1, j) from a sensing element (i) of the same radiation detector during a whole charge collection period (1, j), wherein M and N are positive integers; for each combination of i and j (i=1, ..., M, and j=1, ..., N), using a charge collection device (i, 2) to collect charges (i, 2, j) from a sensing element (i) of the radiation detector during a whole charge collection period (2, j); and for each value of i, based on the charges (i, 1, j) and the charges (i, 2, j) (j=1, ..., N), determining a final value of a pixel (i) of the same image. The charge collection period (1, j) and the charge collection period (2, j) (j=1, ..., N) are discrete from each other, so that there is no overlap between these 2×N charge collection periods.

[0003] In one aspect, N=1.

[0004] On the one hand, the charge collection device (i,1) (i=1, ..., M) respectively includes capacitors (i,1) (i=1, ..., M), and the charge collection device (i,2) (i=1, ..., M) respectively includes capacitors (i,2) (i=1, ..., M).

[0005] In one aspect, the radiation detector comprises an absorption layer and an electronic layer, the absorption layer comprising a sensing element (i) (i=1, ..., M), and the electronic layer comprising a charge collection device (i, 1) (i=1, ..., M) and a charge collection device (i, 2) (i=1, ..., M).

[0006] On the one hand, determining the final value of pixel (i) includes: for each value of j, determining the data value (i,j) based on charge (i,1,j) and charge (i,2,j); and determining the best fit value of the data value (i,j) (j=1,...,N) as the final value of pixel (i).

[0007] On the one hand, determining the data value (i, j) includes: digitizing the charge (i, 1, j) and the charge (i, 2, j) to obtain the digital value (i, 1, j) and the digital value (i, 2, j), respectively; and obtaining the difference between the digital value (i, 2, j) and the digital value (i, 1, j) as the data value (i, j).

[0008] In one aspect, determining the data value (i, j) includes obtaining a difference between the charge (i, 2, j) and the charge (i, 1, j).

[0009] On the one hand, the charge collection device (i,1) (i=1, ..., M) respectively includes capacitors (i,1) (i=1, ..., M), and the charge collection device (i,2) (i=1, ..., M) respectively includes capacitors (i,2) (i=1, ..., M), and for each combination of i and j, the step of obtaining the difference between charge (i,2,j) and charge (i,1,j) includes: after the charge collection period (1,j) and the charge collection period (2,j), the positive side of capacitor (i,1) is electrically connected to the negative side of capacitor (i,2), and the negative side of capacitor (i,1) is electrically connected to the positive side of capacitor (i,2).

[0010] In one aspect, for each value of j, charge collection period (1, j) precedes charge collection period (2, j), or charge collection period (1, j) follows charge collection period (2, j).

[0011] On the one hand, for each value of j (j=1, ..., N), the charge collection period (1, j) and the charge collection period (2, j) are not separated by another charge collection period among the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N).

[0012] In one aspect, all charge collection periods (1, j) (j=1, ..., N) and charge collection periods (2, j) (j=1, ..., N) have the same length.

[0013] On the one hand, all charge collection periods (1, j) (j=1, ..., N) and charge collection periods (2, j) (j=1, ..., N) do not have the same length, and determining the final value of the pixel (i) of the image is also based on the length of the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N).

[0014] On the one hand, for each value of j, the radiation detector receives incident radiation particles from the radiation pulse (j) during the charge collection period (1, j), and does not receive any incident radiation particles from the radiation pulse (j) during the charge collection period (2, j), and the radiation pulse (j) generates multiple portions of charge (i, 1, j) (i = 1, ..., M) in the sensing element (i) (i = 1, ..., M) during the charge collection period (1, j), respectively.

[0015] The present invention also discloses a system including a radiation detector, which includes a sensing element (i) (i=1, ..., M), a charge collection device (i, 1) (i=1, ..., M) and a charge collection device (i, 2) (i=1, ..., M), wherein for each value of i and for j (j=1, ..., N), the charge collection device (i, 1) is configured to collect charges (i, 1, j) from the sensing element (i) within the entire charge collection period (1, j), and for each combination of i and j, the charge collection device (i, 2) is configured to collect charges (i, 2, j) from the sensing element (i) within the entire charge collection period (2, j). The system is configured to determine, for each value of i, a final value of a pixel (i) of the same image based on charge (i,1,j) (j=1, ..., N) and charge (i,2,j) (j=1, ..., N), and the charge collection period (1,j) (j=1, ..., N) and the charge collection period (2,j) (j=1, ..., N) are discrete from each other so that there is no overlap between these 2×N charge collection periods.

[0016] On the one hand, the charge collection device (i,1) (i=1, ..., M) respectively includes capacitors (i,1) (i=1, ..., M), and the charge collection device (i,2) (i=1, ..., M) respectively includes capacitors (i,2) (i=1, ..., M).

[0017] On the one hand, the absorption layer of the radiation detector includes sensing elements (i) (i=1, ..., M), and the electronic layer of the radiation detector includes charge collection devices (i, 1) (i=1, ..., M) and charge collection devices (i, 2) (i=1, ..., M).

[0018] On the one hand, determining the final value of pixel (i) includes: for each value of j, determining the data value (i,j) based on charge (i,1,j) and charge (i,2,j); and determining the best fit value of the data value (i,j) (j=1,...,N) to be used as the final value of pixel (i).

[0019] On the one hand, determining the data value (i, j) includes: digitizing the charge (i, 1, j) and the charge (i, 2, j) to obtain the digital value (i, 1, j) and the digital value (i, 2, j), respectively; and obtaining the difference between the digital value (i, 2, j) and the digital value (i, 1, j) as the data value (i, j).

[0020] In one aspect, determining the data value (i, j) includes obtaining a difference between the charge (i, 2, j) and the charge (i, 1, j).

[0021] On the one hand, the charge collection device (i,1) (i=1, ..., M) includes capacitors (i,1) (i=1, ..., M), respectively, and the charge collection device (i,2) (i=1, ..., M) includes capacitors (i,2) (i=1, ..., M), respectively, and the system includes a switch, the switch is configured to, for each combination of i and j, (A) after the charge collection period (1,j) and the charge collection period (2,j), electrically connect the positive side of the capacitor (i,1) to the negative side of the capacitor (i,2), and (B) after the charge collection period (1,j) and the charge collection period (2,j), electrically connect the negative side of the capacitor (i,1) to the positive side of the capacitor (i,2).

[0022] In one aspect, the charge collection period (1, j) (j=1, . . . , N) and the charge collection period (2, j) (j=1, . . . , N) have the same length. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A radiation detector according to an embodiment is schematically shown.

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

[0025] Figure 3 A detailed cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0026] Figure 4 A detailed cross-sectional view of a radiation detector according to an alternative embodiment is schematically shown.

[0027] Figure 5 An imaging system according to an embodiment is schematically illustrated.

[0028] Figure 6 A flow chart outlining the operation of an imaging system according to an embodiment is shown.

[0029] Figure 7 An alternative embodiment for operating the imaging system is shown. DETAILED DESCRIPTION

[0030] Radiation Detectors

[0031] As an example, Figure 1 The radiation detector 100 is schematically shown. The radiation detector 100 may include an array of pixels 150 (also referred to as sensing elements 150). The array may be a rectangular array (e.g. Figure 1 as shown), a honeycomb array, a hexagonal array, or any other suitable array. Figure 1 The array of pixels 150 in the example of FIG. 1 has 4 rows and 7 columns; however, in general, the array of pixels 150 may have any number of rows and any number of columns.

[0032] Each pixel 150 can be configured to detect radiation from a radiation source (not shown) incident thereon, and can be configured to measure the characteristics of the radiation (e.g., the energy, wavelength, and frequency of the particles). The radiation may include radiation particles such as photons (X-rays, gamma rays, etc.) and subatomic particles (alpha particles, beta particles, etc.). Each pixel 150 can be configured to count the number of radiation particles incident thereon over a period of time and whose energy falls into a plurality of energy bins. All pixels 150 can be configured to count the number of radiation particles incident thereon and falling into a plurality of energy bins over the same period of time. When the incident radiation particles have similar energies, the pixel 150 can be simply configured to count the number of radiation particles incident thereon over a period of time without measuring the energy of each radiation particle.

[0033] Each pixel 150 may have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of an incident radiation particle into a digital signal, or to digitize an analog signal representing the total energy of multiple incident radiation particles into a digital signal. The pixels 150 may be configured to run in parallel. For example, when one pixel 150 measures an incident radiation particle, another pixel 150 may be waiting for the radiation particle to arrive. The pixels 150 may not necessarily be individually addressable.

[0034] The radiation detector 100 described herein may be applied to applications such as: X-ray telescopes, X-ray mammography, industrial X-ray defect detection, X-ray microscopy or microradiography, X-ray casting inspection, X-ray nondestructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. It may be appropriate to use this radiation detector 100 instead of a photographic plate, photographic film, a photo-stimulated phosphor plate (PSP plate), an X-ray image intensifier, a scintillator, or another semiconductor X-ray detector.

[0035] Figure 2 Schematically illustrating the Figure 12-2. Specifically, the radiation detector 100 may include a radiation absorbing layer 110 and an electronic layer 120 (which may include one or more ASICs or application specific integrated circuits), and the electronic layer 120 is used to process and analyze the electrical signal generated in the radiation absorbing layer 110 by the incident radiation. The radiation detector 100 may or may not include a scintillator (not shown). The radiation absorbing layer 110 may include a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe or a combination thereof. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest.

[0036] As an example, Figure 3 Schematically shows Figure 1 Detailed cross-sectional view of the radiation detector 100 along line 2-2. Specifically, 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 the first doping region 111, the 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 may be 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 may have opposite types of doping (e.g., the first doping region 111 is p-type and the second doping region 113 is n-type; or the first doping region 111 is n-type and the second doping region 113 is p-type). Figure 3 In the example of , each discrete region 114 of the second doped region 113 forms a diode together with the first doped region 111 and the optional intrinsic region 112. Figure 3 In the example of FIG. 1 , the radiation absorbing layer 110 has a plurality of diodes (more specifically, 7 diodes corresponding to Figure 1 The array has 7 pixels in one row 150, for simplicity, in Figure 3 Only two pixels 150 are marked in FIG. 1 . The plurality of diodes may have an electrical contact 119A as a common electrode. The first doped region 111 may also have a plurality of discrete portions.

[0037] The electronic layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation incident on the radiation absorption 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 one or more ADCs (analog-to-digital converters). The electronic system 121 may include components shared by multiple pixels 150 or components dedicated to a single pixel 150. For example, the electronic system 121 may include an amplifier dedicated to each pixel 150 and a microprocessor shared between all pixels 150. The electronic system 121 may be electrically connected to the pixel 150 through the through hole 131. The space between the through holes can be filled with a filling material 130, which can increase the mechanical stability of the connection of the electronic layer 120 to the radiation absorption layer 110. Other bonding techniques can connect the electronic system 121 to the pixel 150 without using the through hole 131.

[0038] When radiation from a radiation source (not shown) strikes the radiation absorbing layer 110 including the diode, the radiation particles may be absorbed and generate one or more carriers (e.g., electrons, holes) through a variety of mechanisms. The carriers may drift to one of the electrodes of the diodes under the action of an electric field. The electric field may be an external electric field. The electrical contact 119B may include a plurality of discrete portions, each of which is in electrical contact with the discrete region 114. The term "electrical contact" may be used interchangeably with the term "electrode". In one embodiment, the carriers may drift in a plurality of directions, and the carriers generated by a single radiation particle are not substantially shared by two different discrete regions 114 (here, "substantially not shared by..." means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to a discrete region 114 different from the discrete region to which the remaining carriers flow). The carriers generated by radiation particles incident on the footprint of one of the discrete regions 114 are not substantially shared by another of the discrete regions 114. A pixel 150 associated with a discrete region 114 may be an area around the discrete region 114 in which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the carriers generated by radiation particles incident therein flow toward the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of the carriers flow out of the pixel 150.

[0039] Figure 4 Schematically illustrating an alternative embodiment Figure 1Detailed cross-sectional view of radiation detector 100 along line 2-2. More specifically, radiation absorbing layer 110 may include resistors of semiconductor materials such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof, but not diodes. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest. In one embodiment, Figure 4 The electronic layer 120 is similar in structure and function to Figure 3 The electron layer is 120.

[0040] When radiation strikes the radiation absorbing layer 110, which includes a resistor but does not include a diode, it can be absorbed and generate one or more carriers through a variety of mechanisms. One radiation particle can generate 10 to 100,000 carriers. The carriers can drift to the electrical contacts 119A and 119B under the action of the electric field. The electric field can be an external electric field. The electrical contact 119B can include multiple discrete parts. In one embodiment, the carriers can drift in multiple directions and make the carriers generated by a single radiation particle substantially not shared by two different discrete parts of the electrical contact 119B (here "substantially not shared by..." means that less than 2%, less than 0.5%, less than 0.1% or less than 0.01% of these carriers flow to a discrete part of the multiple discrete parts that is different from the discrete part to which the remaining carriers flow). The charge carriers generated by radiation particles incident on the footprint of one of the discrete portions of the electrical contact 119B are not substantially shared by another of the discrete portions of the electrical contact 119B. A pixel 150 associated with a discrete portion of the electrical contact 119B may be an area around the discrete portion in which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by radiation particles incident therein flow toward 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 out of the pixel associated with the discrete portion of the electrical contact 119B.

[0041] The term "image" in this patent application (including claims) is not limited to the spatial distribution of radiation characteristics (such as intensity). For example, the term "image" may also include the spatial distribution of the density of a substance or element.

[0042] Imaging System

[0043] Figure 5 The imaging system 500 according to an embodiment is schematically shown. In an embodiment, the imaging system 500 may include Figure 1-Figure 4 The radiation detector 100 and the radiation source 510 are provided.

[0044] In one embodiment, the radiation detector 100 of the imaging system 500 may be operated in an integration mode instead of a particle counting mode (also referred to as a photon counting mode) as described in the above embodiments. Specifically, when the radiation detector 100 is operated in the integration mode, for each sensor element 150 (e.g., sensor element 150.1) of the radiation detector 100, the electron layer 120 of the radiation detector 100 collects the charge (i.e., signal) generated in each sensor element 150 during the entire integration period (also referred to as a charge collection period).

[0045] In one embodiment, object 520 may be located between radiation source 510 and radiation detector 100 (as shown).

[0046] In one embodiment, for each sensing element 150 of the radiation detector 100, the electronic layer 120 may include a first capacitor and a second capacitor (e.g., as shown, the electronic layer 120 may include a first capacitor 520.1a and a second capacitor 520.1b for the sensing element 150.1). Thus, the electronic layer 120 includes 28 sensing elements 150 for the radiation detector 100 ( Figure 1 )'s 28 first capacitors and 28 second capacitors.

[0047] Operation of the imaging system

[0048] In an embodiment, imaging system 500 may be used to generate a first data image of object 520 as follows. Specifically, radiation source 510 may send a first radiation pulse 511 toward object 520.

[0049] Charge Collection Process

[0050] For the sensing element 150.1, during the entire charge collection period 511x, the first capacitor 520.1a can collect the first charge (i.e., signal) generated in the sensing element 150.1 during the charge collection period 511x. In one embodiment, the charge collection period 511x can coincide with the duration of the first radiation pulse 511 (as shown).

[0051] Note that the first charge generated in the sensor element 150.1 during the charge collection period 511x may originate from (A) radiation particles of the first radiation pulse 511 incident on the sensor element 150.1 during the charge collection period 511x, and (B) dark current flowing in the sensor element 150.1 during the charge collection period 511x.

[0052] Dark current may have various sources. For example, dark current may originate from structural defects in the semiconductor crystal of the absorption layer 110. Dark current may also originate from thermal energy within the crystal lattice of the absorption layer 110.

[0053] In one embodiment, after the first radiation pulse 511, the second capacitor 520.1b can collect the second charge generated in the sensing element 150.1 during the charge collection period 511y throughout the charge collection period 511y. In one embodiment, the charge collection period 511y can be the same in length as the charge collection period 511x (e.g., both have a length of 1 μs).

[0054] It should be noted that the second charge generated in the sensor element 150 . 1 during the charge collection period 511 y may originate from a dark current flowing in the sensor element 150 . 1 during the charge collection period 511 y .

[0055] Eliminating the influence of dark current

[0056] In one embodiment, a data value of a picture element of the first data image corresponding to the sensing element 150 . 1 may be determined based on the first charge and the second charge described above.

[0057] Specifically, in one embodiment, the data value may be the difference between (a) the digital value of the first charge and (b) the digital value of the second charge. More specifically, in one embodiment, the first charge may be digitized (e.g., the voltage on the first capacitor 520.1a may be read out and then digitized to obtain the first digital value); and the second charge may be digitized (e.g., the voltage on the second capacitor 520.1b may be read out and then digitized to obtain the second digital value). Then, the difference between the second digital value and the first digital value is obtained as the data value of the pixel corresponding to the sensing element 150.1 of the first data image.

[0058] In an alternative embodiment, the difference between the second charge and the first charge can be obtained as the above-mentioned data value. Specifically, in one embodiment, the difference can be obtained by the following method: after the charge collection periods 511x and 511y, the positive side of the first capacitor 520.1a is electrically connected to the negative side of the second capacitor 520.1b, and (B) the negative side of the first capacitor 520.1a is electrically connected to the positive side of the second capacitor 520.1b. Therefore, the resulting charge in the first capacitor 520.1a represents the difference between the first charge and the second charge. Then, the voltage on the first capacitor 520.1a can be read out and then digitized to obtain the data value of the pixel corresponding to the sensing element 150.1 of the first data image.

[0059] In an embodiment, the electronic layer 120 of the radiation detector 100 may include a switch (not shown) for electrically connecting the first capacitor 520.1a and the second capacitor 520.1b as described above.

[0060] It should be noted that the difference between the second charge and the first charge does not include the influence of the dark current on the pixel corresponding to the sensing element 150.1 of the first data image.

[0061] Data values ​​of other pixels

[0062] In one embodiment, the 27 data values ​​of the 27 remaining pixels of the first data image corresponding to the 27 remaining sensor elements 150 (i.e., sensor elements 150 other than sensor element 150.1) may be determined in a manner similar to the manner in which the data value of the pixel of the first data image corresponding to sensor element 150.1 was determined.

[0063] In one embodiment, the charge collection process of the 28 sensing elements 150 (including the sensing element 150.1) of the radiation detector 100 can be performed simultaneously in the entire charge collection period 511x. In other words, the 28 first capacitors of the 28 sensing elements 150 of the radiation detector 100 simultaneously and separately collect the 28 first charges generated by the first radiation pulse 511 and the dark current in the entire charge collection period 511x.

[0064] Similarly, in one embodiment, the charge collection process of the 28 sensing elements 150 (including the sensing element 150.1) of the radiation detector 100 can be performed simultaneously in the entire charge collection period 511y. In other words, the 28 second capacitors of the 28 sensing elements 150 of the radiation detector 100 simultaneously and respectively collect the 28 second charges generated by the dark current in the entire charge collection period 511y.

[0065] More radiation pulses for more data images

[0066] In one embodiment, reference Figure 5 , after the charge collection periods 511 x and 511 y , the radiation source 510 may send a second radiation pulse 512 to the object 520 .

[0067] In one embodiment, a second data image of the object 520 may be generated corresponding to the second radiation pulse 512 in a manner similar to the manner in which the first data image of the object 520 is generated corresponding to the first radiation pulse 511. Specifically, first, the 28 first capacitors of the 28 sensing elements 150 used in the radiation detector 100 may simultaneously and respectively collect the 28 first charges generated by the second radiation pulse 512 and the dark current during the entire charge collection period 512x. Then, the 28 second capacitors of the 28 sensing elements 150 used in the radiation detector 100 may simultaneously and respectively collect the 28 second charges generated by the dark current during the entire charge collection period 512y. Then, 28 differences between the obtained 28 second charges and the 28 first charges may be obtained respectively, and then the 28 differences may be digitized to generate 28 data values ​​of 28 pixels of the second data image of the object 520.

[0068] In one embodiment, reference Figure 5 , after charge collection periods 512x and 512y , radiation source 510 may send a third radiation pulse 513 to object 520 .

[0069] In one embodiment, a third data image of the object 520 may be generated corresponding to the third radiation pulse 513 in a manner similar to the manner in which the first data image of the object 520 is generated corresponding to the first radiation pulse 511. Specifically, first, the 28 first capacitors of the 28 sensing elements 150 used in the radiation detector 100 may simultaneously and respectively collect the 28 first charges generated by the third radiation pulse 513 and the dark current in the entire charge collection period 513x. Then, the 28 second capacitors of the 28 sensing elements 150 used in the radiation detector 100 may simultaneously and respectively collect the 28 second charges generated by the dark current in the entire charge collection period 513y. Then, 28 differences between the obtained 28 second charges and the 28 first charges may be obtained respectively, and then the 28 differences may be digitized to generate 28 data values ​​of the 28 pixels of the third data image of the object 520.

[0070] Final image of the object

[0071] In one embodiment, reference Figure 5 , a final image of the object 520 can be generated based on the first, second and third data images of the object 520.

[0072] Specifically, in one embodiment, the final value of the pixel corresponding to the sensor element 150.1 of the final image may be determined based on the following values: (A) the data value of the pixel corresponding to the sensor element 150.1 of the first data image, (B) the data value of the pixel corresponding to the sensor element 150.1 of the second data image, and (C) the data value of the pixel corresponding to the sensor element 150.1 of the third data image. More specifically, in one embodiment, the final value may be the best fit value (e.g., least squares) of the three data values ​​from the first, second, and third data images, respectively.

[0073] In one embodiment, the 27 remaining final values ​​of the 27 remaining picture elements of the final image may be determined in a similar manner.

[0074] In other words, the final value of the pixel corresponding to the sensor element 150 of the radiation detector 100 of the final image is determined based on the following values: (A) the first charge and the second charge generated in the sensor element 150 during the charge collection periods 511x and 511y, respectively, (B) the first charge and the second charge generated in the sensor element 150 during the charge collection periods 512x and 512y, respectively, and (C) the first charge and the second charge generated in the sensor element 150 during the charge collection periods 513x and 513y, respectively. In one embodiment, the numerical difference of the above six charges can be used to determine whether the final value of the pixel corresponding to the sensor element 150 of the final image is acceptable. For example, if the numerical difference exceeds a pre-specified threshold, the generated final value can be considered unacceptable.

[0075] Flowchart outlining the operation of the imaging system

[0076] Figure 6 A flowchart 600 outlining the operation of the imaging system 500 according to an embodiment is shown. In step 610, the operation may include: for each combination of i and j (i=1, ..., M, j=1, ..., N), using a charge collection device (i, 1) to collect the charge (i, 1, j) from the sensing element (i) of the same radiation detector over the entire charge collection period (1, j), where M and N are positive integers. For example, in the embodiment described above, with reference to Figure 5 , for the sensing element 150.1, the first capacitor 520.1a collects the first charge from the sensing element 150.1 of the radiation detector 100 during the entire charge collection period 511x. Here, M=28, N=3.

[0077] In step 620, the operation may include: for each combination of i and j (i=1, ..., M, j=1, ..., N), using the charge collection device (i, 2) to collect the charge (i, 2, j) from the sensing element (i) of the radiation detector during the entire charge collection period (2, j). For example, in the embodiment described above, with reference to Figure 5 , for the sensing element 150.1, the second capacitor 520.1b collects the second charge from the sensing element 150.1 during the entire charge collection period 511y.

[0078] In step 630, the operation may include: for each value of i, based on the charge (i,1,j) (j=1, ..., N) and the charge (i,2,j) (j=1, ..., N), determining the final value of the pixel (i) of the same image. For example, in the embodiment described above, reference Figure 5 , for sensor element 150.1, a final value of a pixel of a final image corresponding to sensor element 150.1 of radiation detector 100 is determined based on the following six charges: (A) a first charge and a second charge generated in sensor element 150.1 during charge collection periods 511x and 511y, respectively, (B) a first charge and a second charge generated in sensor element 150.1 during charge collection periods 512x and 512y, respectively, and (C) a first charge and a second charge generated in sensor element 150.1 during charge collection periods 513x and 513y, respectively.

[0079] In addition, in step 630, the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N) are discrete from each other, so that there is no overlap between these 2×N charge collection periods. For example, in the embodiment described above, referring to Figure 5 , there is no overlap between the six charge collection periods 511x, 511y, 512x, 512y, 513x and 513y. In other words, no time point is within at least two of the six charge collection periods 511x, 511y, 512x, 512y, 513x and 513y.

[0080] Other embodiments

[0081] Using a single radiation pulse

[0082] In one embodiment, reference Figure 5 and Figure 6 , N may be 1. For example, in the embodiment described above, only the radiation pulse 511 is used; and the first data image may be used as the final image of the object 520 .

[0083] In another embodiment, N may be greater than one.

[0084] Relative time position of charge collection period

[0085] In one embodiment, reference Figure 5 and Figure 6 , for each value of j, the charge collection period (1, j) may precede the charge collection period (2, j). For example, when j=1, the charge collection period 511x precedes the charge collection period 511y (as shown). For another example, when j=2, the charge collection period 512x precedes the charge collection period 512y (as shown). For another example, when j=3, the charge collection period 513x precedes the charge collection period 513y (as shown).

[0086] In addition, in one embodiment, for each value of j, no charge collection period is between the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N). That is, for each value of j, the charge collection period (1, j) and the charge collection period (2, j) are not separated by another charge collection period among the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N). This situation is as follows Figure 5 Specifically, the charge collection period 511x is immediately before the charge collection period 511y; the charge collection period 512x is immediately before the charge collection period 512y; and the charge collection period 513x is immediately before the charge collection period 513y.

[0087] In an alternative embodiment, reference Figure 5-Figure 7 , for each value of j, the charge collection period (1, j) can be followed by the charge collection period (2, j). Figure 7 , when j=1, the charge collection period 511x is after the charge collection period 511y (as shown in the figure). For another example, when j=2, the charge collection period 512x is after the charge collection period 512y (as shown in the figure). For another example, when j=3, the charge collection period 513x is after the charge collection period 513y (as shown in the figure).

[0088] In addition, in one embodiment, for each value of j, no charge collection period is between the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N). That is, for each value of j, the charge collection period (1, j) and the charge collection period (2, j) are not separated by another charge collection period among the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N). This situation is as follows Figure 7 Specifically, the charge collection period 511x is immediately after the charge collection period 511y; the charge collection period 512x is immediately after the charge collection period 512y; and the charge collection period 513x is immediately after the charge collection period 513y.

[0089] Length of the charge collection period

[0090] In the embodiments described above, the charge collection periods 511x, 512x, and 513x coincide with the durations of the radiation pulses 511, 512, and 513, respectively. In general, the charge collection period 511x may have any length within the duration of the radiation pulse 511, such that each time point of the charge collection period 511x is within the duration of the radiation pulse 511. Similarly, the charge collection period 512x may have any length within the duration of the radiation pulse 512, such that each time point of the charge collection period 512x is within the duration of the radiation pulse 512. Similarly, the charge collection period 513x may have any length within the duration of the radiation pulse 513, such that each time point of the charge collection period 513x is within the duration of the radiation pulse 513.

[0091] All charge collection periods can be the same

[0092] In one embodiment, reference Figure 5-Figure 7 , all charge collection periods (1, j) (j=1, ..., N) and charge collection periods (2, j) (j=1, ..., N) may have the same length. For example, all six charge collection periods 511x, 511y, 512x, 512y, 513x and 513y have the same length (as shown).

[0093] All charge collection periods can be different

[0094] In an alternative embodiment, reference Figure 5-Figure 7, the lengths of all charge collection periods (1, j) (j=1, ..., N) and charge collection periods (2, j) (j=1, ..., N) are different. In this case, the determination of the final value of the picture element (i) of the image is also based on the lengths of the charge collection periods (1, j) (j=1, ..., N) and the charge collection periods (2, j) (j=1, ..., N).

[0095] For example, in the embodiment described above, it is assumed that the two charge collection periods 511x and 511y are 1 μs and 2 μs, respectively. Therefore, in order to determine the data value of the pixel corresponding to the sensing element 150.1 of the first data image, the second charge needs to be multiplied by the ratio 1 μs / 2 μs or 0.5 and then subtracted from the first charge. In other words, if the lengths of the charge collection periods are not the same, the lengths of the charge collection periods need to be taken into account when determining the data value and the final value.

[0096] While various aspects and embodiments are 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. A method comprising: For each combination of i and j (i=1, ..., M, j=1, ..., N), using a charge collection device (i, 1) to collect the charge (i, 1, j) from the sensing element (i) of the same radiation detector during the entire charge collection period (1, j), wherein M and N are positive integers; for each combination of i and j (i=1, ..., M, j=1, ..., N), collecting, by means of a charge collection device (i, 2), charges (i, 2, j) from said sensing element (i) of said radiation detector over a charge collection period (2, j); and For each value of i, based on the charge (i,1,j) and the charge (i,2,j) (j=1, ..., N), determine the final value of the pixel (i) of the same image, The charge collection period (1, j) and the charge collection period (2, j) (j=1, . . . , N) are discrete from each other, so that there is no overlap between the 2×N charge collection periods.

2. The method of claim 1, wherein: N＝1。 3. The method according to claim 1, in, The charge collection devices (i, 1) (i=1, ..., M) respectively include capacitors (i, 1) (i=1, ..., M), and Wherein, the charge collection devices (i, 2) (i=1, ..., M) respectively include capacitors (i, 2) (i=1, ..., M).

4. The method according to claim 1, in, The radiation detector comprises an absorption layer and an electronic layer, Wherein, the absorption layer includes the sensing element (i) (i=1, ..., M), and Wherein, the electronic layer includes the charge collection device (i, 1) (i=1, ..., M) and the charge collection device (i, 2) (i=1, ..., M).

5. The method of claim 1, wherein: Determining the final value of the pixel (i) comprises: for each value of j, determining a data value (i, j) based on the charge (i, 1, j) and the charge (i, 2, j); and The best fitting value of the data value (i, j) (j=1, ..., N) is determined as the final value of the pixel (i).

6. The method of claim 5, wherein: The determining the data value (i, j) comprises: digitizing the charge (i, 1, j) and the charge (i, 2, j) to obtain a digital value (i, 1, j) and a digital value (i, 2, j), respectively; and The difference between the digital value (i, 2, j) and the digital value (i, 1, j) is obtained as the data value (i, j).

7. The method of claim 5, wherein: The determining the data value (i, j) includes obtaining a difference between the charge (i, 2, j) and the charge (i, 1, j).

8. The method according to claim 7, in, The charge collection devices (i, 1) (i=1, ..., M) respectively include capacitors (i, 1) (i=1, ..., M), wherein the charge collection devices (i, 2) (i=1, ..., M) respectively include capacitors (i, 2) (i=1, ..., M), and Wherein, for each combination of i and j, obtaining the difference between the charge (i,2,j) and the charge (i,1,j) includes: after the charge collection period (1,j) and the charge collection period (2,j), electrically connecting the positive side of the capacitor (i,1) to the negative side of the capacitor (i,2), and electrically connecting the negative side of the capacitor (i,1) to the positive side of the capacitor (i,2).

9. The method of claim 1, wherein: For each value of j, the charge collection period (1, j) precedes the charge collection period (2, j), or the charge collection period (1, j) follows the charge collection period (2, j).

10. The method of claim 9, wherein: For each value of j (j=1, ..., N), the charge collection period (1, j) and the charge collection period (2, j) are not separated by another charge collection period among the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N).

11. The method of claim 1, wherein: All of the charge collection periods (1, j) (j=1, . . . , N) and the charge collection periods (2, j) (j=1, . . . , N) have the same length.

12. The method of claim 1, in, All of the charge collection periods (1, j) (j=1, ..., N) and the charge collection periods (2, j) (j=1, ..., N) do not have the same length, and Wherein, the determination of the final value of the picture element (i) of the image is also based on the length of the charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N).

13. The method of claim 1, in, For each value of j, the radiation detector receives incident radiation particles from the radiation pulse (j) during the charge collection period (1, j) and does not receive any incident radiation particles from the radiation pulse (j) during the charge collection period (2, j), and The radiation pulse (j) generates a plurality of parts of the charge (i, 1, j) (i=1, ..., M) in the sensor element (i) (i=1, ..., M) during the charge collection period (1, j).

14. A system comprising a radiation detector, the radiation detector comprising a sensing element (i) (i=1, ..., M), a charge collection device (i, 1) (i=1, ..., M) and a charge collection device (i, 2) (i=1, ..., M), in, For each value of i and for j (j=1, ..., N), the charge collection device (i, 1) is configured to collect the charge (i, 1, j) from the sensing element (i) over the entire charge collection period (1, j), wherein, for each combination of i and j, the charge collection device (i, 2) is configured to collect the charge (i, 2, j) from the sensing element (i) within a charge collection period (2, j), wherein the system is configured to determine, for each value of i, a final value of a pixel (i) of the same image based on the charge (i,1,j) (j=1, ..., N) and the charge (i,2,j) (j=1, ..., N), and The charge collection period (1, j) (j=1, ..., N) and the charge collection period (2, j) (j=1, ..., N) are discrete from each other, so that there is no overlap between these 2×N charge collection periods.

15. The system of claim 14, in, The charge collection devices (i, 1) (i=1, ..., M) respectively include capacitors (i, 1) (i=1, ..., M), and Wherein, the charge collection devices (i, 2) (i=1, ..., M) respectively include capacitors (i, 2) (i=1, ..., M).

16. The system of claim 14, in, The absorption layer of the radiation detector comprises the sensing element (i) (i=1, ..., M), and The electronic layer of the radiation detector includes the charge collection device (i, 1) (i=1, ..., M) and the charge collection device (i, 2) (i=1, ..., M).

17. The system of claim 14, wherein: Determining the final value of the pixel (i) comprises: for each value of j, determining a data value (i, j) based on the charge (i, 1, j) and the charge (i, 2, j); and The best fit value of the data value (i, j) (j=1, ..., N) is determined to be used as the final value of the pixel (i).

18. The system of claim 17, wherein: The determining the data value (i, j) comprises: digitizing the charge (i, 1, j) and the charge (i, 2, j) to obtain a digital value (i, 1, j) and a digital value (i, 2, j), respectively; and The difference between the digital value (i, 2, j) and the digital value (i, 1, j) is obtained as the data value (i, j).

19. The system of claim 17, wherein: The determining the data value (i, j) includes obtaining a difference between the charge (i, 2, j) and the charge (i, 1, j).

20. The system of claim 19, in, The charge collection devices (i, 1) (i=1, ..., M) respectively include capacitors (i, 1) (i=1, ..., M); wherein the charge collection devices (i, 2) (i=1, ..., M) respectively include capacitors (i, 2) (i=1, ..., M), and The system includes a switch configured to, for each combination of i and j, (A) electrically connect the positive side of the capacitor (i, 1) to the negative side of the capacitor (i, 2) after the charge collection period (1, j) and the charge collection period (2, j), and (B) electrically connect the negative side of the capacitor (i, 1) to the positive side of the capacitor (i, 2) after the charge collection period (1, j) and the charge collection period (2, j).

21. The system of claim 14, wherein: The charge collection period (1, j) (j=1, . . . , N) and the charge collection period (2, j) (j=1, . . . , N) have the same length.

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