WO2017086181A1 - 光パルス検出装置、光パルス検出方法、放射線計数装置、および生体検査装置 - Google Patents
光パルス検出装置、光パルス検出方法、放射線計数装置、および生体検査装置 Download PDFInfo
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Definitions
- the present technology relates to an optical pulse detection device, an optical pulse detection method, a radiation counting device, and a biological examination device, and in particular, an optical pulse detection device, an optical pulse detection method, and a radiation that can perform radiation counting more accurately.
- the present invention relates to a counting device and a biopsy device.
- a radiation counter that counts the dose of radiation incident on a detector while performing individual energy fractionation in units of incident photons is applied to various fields such as survey meters and gamma cameras.
- a scintillator and a photomultiplier tube are usually used.
- the radiation counter counts the energy and number of radiation incident on the detector.
- the scintillator emits light, and emits a pulse of visible light whose amount is proportional to the energy of the radiation. Such a light emission pulse is emitted each time a radiation photon enters and is detected by a photomultiplier tube.
- the scintillator is covered with a partition wall in which only the surface directed to the photomultiplier tube is opened.
- the barrier blocks the intrusion of visible light from the outside and desirably reflects the light generated from the inside so that all of the light enters the photomultiplier tube.
- the photomultiplier tube converts a light emission pulse into an electron and amplifies it to generate an analog electric pulse.
- the pulse height of the analog electric pulse is proportional to the amount of light emitted from the scintillator, that is, the energy of radiation. Since an independent pulse is output every time one radiation photon enters, the radiation counter can determine the number of incident radiation photons by counting the number of pulses.
- the detection circuit in the above-mentioned radiation counter amplifies and shapes the generated pulse, converts it into an analog wave with an appropriate delay, and converts it into a digital value by an AD converter.
- the radiation counter can derive the energy for each incident radiation photon as a digital value.
- a digital processing circuit in the radiation counter accumulates output results of the detection circuit in a predetermined period and derives an energy spectrum of radiation photons. This energy spectrum shows the abundance ratio of radiation photons captured by the radiation counter for each energy. This allows the radiation counter to identify the radiation source. Or the radiation directly incident from the radiation source and the radiation scattered in the middle can be separated.
- the present technology has been made in view of such a situation, and makes it possible to perform radiation counting more accurately.
- An optical pulse detection device includes a pixel array unit in which a plurality of pixels are arranged in a two-dimensional lattice, and an output signal of each pixel of the pixel array unit is a digital signal having a gradation larger than 1 bit.
- An AD converter that converts the value into a value; and a control circuit that performs an error determination process that compares the digital value with a first threshold value and discards the digital value that is larger than the first threshold value as an error.
- the optical pulse detection method includes a pixel array unit in which a plurality of pixels are arranged in a two-dimensional lattice, and an output signal of each pixel of the pixel array unit is a digital signal having a gradation larger than 1 bit.
- An optical pulse detection device comprising: an AD converter that converts a value into a value; and a control circuit that performs an error determination process that compares the digital value with a predetermined threshold value and discards the digital value larger than the threshold value as an error.
- An error determination process is performed in which an output signal of each pixel of the array unit is converted into a digital value having a gradation larger than 1 bit, the digital value is compared with a predetermined threshold, and the digital value larger than the threshold is discarded as an error. .
- an output signal of each pixel of the pixel array unit is converted into a digital value having a gradation larger than 1 bit, and the converted digital value is compared with a predetermined threshold value. Error determination processing for discarding a larger digital value as an error is performed.
- a radiation counting device includes the optical pulse detection device according to the first aspect and a scintillator, and the optical pulse detection device detects a light emission pulse emitted when radiation is incident on the scintillator. To do.
- the light emission pulse emitted by the radiation incident on the scintillator is detected by the light pulse detection device on the first aspect.
- a biopsy device includes the optical pulse detection device according to the first aspect, and the optical pulse detection device is configured to detect fluorescence or fluorescence excited by irradiating a specimen in a fluid with laser light. Detects scattered light.
- fluorescence or scattered light excited by irradiating the specimen in the fluid with laser light is detected by the light pulse detection device of the first aspect.
- the light pulse detection device, the radiation counting device, and the biopsy device may be independent devices or may be internal blocks constituting one device.
- weak pulse light can be detected more accurately.
- radiation counting can be performed more accurately.
- FIG. 27 is a timing chart showing an operation sequence of the pixel circuit of FIG. 26 when the dead time is zero. It is a figure showing an example of composition of a flow cytometer as a living body inspection device to which this art is applied. It is a figure which shows the mode of the weak pulse detection by the photodetector of a flow cytometer.
- First embodiment of radiation counting apparatus (configuration example in which one scintillator is arranged for a photodetector) 2.
- Second embodiment of radiation counting apparatus (configuration example in which a plurality of scintillators are arranged for a photodetector) 3.
- Semiconductor substrate structure example of photodetector 4.
- Other configuration examples of pixel circuit Other applications of photodetectors
- FIG. 1 shows a configuration example of a first embodiment of a radiation counting apparatus to which the present technology is applied.
- the light receiving unit 11 includes a scintillator 21, a partition wall 22, and a photodetector 23.
- FIG. 1A is a sectional view of the scintillator 21, the partition wall 22, and the photodetector 23 of the light receiving unit 11, and FIG. 1B is a perspective view of the scintillator 21 and the photodetector 23 of the light receiving unit 11. Represents.
- the scintillator 21 generates a photon 32 when the radiation 31 is incident thereon.
- the scintillator 21 includes, for example, sodium iodide (NaI), and is processed into a rectangular parallelepiped shape with a size of a surface facing the photodetector 23 of 4 millimeters (mm) square.
- the partition wall 22 covers the scintillator 21 and blocks visible light. However, the partition wall 22 is opened only on the face facing the photodetector 23 in the vicinity.
- the partition wall 22 is preferably made of a reflective material (for example, aluminum) that reflects light. Thereby, most of the photons 32 generated in the scintillator 21 can be made incident on the photodetector 23.
- the light detector 23 detects light and generates a digital signal.
- the photodetector 23 has a light receiving surface facing the scintillator 21, and a plurality of pixels 41 are arranged in a two-dimensional lattice pattern on the light receiving surface. In the present embodiment, it is assumed that 40000 pixels 41 of 200 (200 ⁇ 200) in each of the X direction (horizontal direction) and the Y direction (vertical direction) are arranged. Details of the pixel 41 will be described later.
- the photodetector 23 supplies the generated digital signal to the data processing unit 12 via the signal line 42.
- the scintillator 21 and the photodetector 23 are desirably bonded with an optical adhesive having an appropriate refractive index.
- a light guide made of fiber glass or the like may be inserted between the scintillator 21 and the photodetector 23.
- the data processing unit 12 processes the digital signal supplied from the photodetector 23 and performs radiation counting. In addition, the data processing unit 12 derives the light amount of the light emission pulse and performs energy determination (identification of a radiation source based on energy) of incident radiation.
- the data processing unit 12 can be configured by a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Various signal processing to be described later can be executed by reading and executing by the CPU.
- CPU Central Processing Unit
- ROM Read Only Memory
- RAM Random Access Memory
- the radiation counting apparatus 1 has a configuration of a radiation counting apparatus having a spatial resolution such as a gamma camera by tiling a set of scintillators 21 and photodetectors 23 in the XY direction (arranging a plurality of them in an array). It is also possible.
- FIG. 2 shows a circuit configuration of the photodetector 23.
- the photodetector 23 includes a pixel array unit 51, a detection circuit 52, a switch 53, a row drive circuit 54, a timing control circuit 55, a reference voltage generation circuit 56, an output control circuit 57, and the like. Each circuit constituting the photodetector 23 is provided in one chip, for example.
- a plurality of pixels 41 are arranged in a two-dimensional lattice pattern.
- a predetermined direction (X direction in FIG. 1) in which a plurality of pixels 41 are arranged is referred to as a row direction
- a direction orthogonal to the row direction (Y direction in FIG. 1) is referred to as a column direction.
- detection circuits 52 and switches 53 are provided for one column of pixels 41 in the pixel array unit 51. In FIG. 2, these are shown as detection circuits 52A to 52D and switches 53A to 53D. Yes.
- the pixels 41 in the 0th row are connected to the detection circuit 52A and the switch 53A via the vertical signal line 58A, and the pixels 41 in the 1st row are connected to the vertical signal line 58B.
- the pixels 41 in the second row are connected to the detection circuit 52C and the switch 53C via the vertical signal line 58C
- the pixels 41 in the third row are connected to the detection circuit 52D and the switch 53D via the vertical signal line 58D.
- each pixel 41 of the pixel array unit 51 is also connected to the row drive circuit 54 via a control line 59.
- the detection circuit 52 converts an analog electric signal supplied from the pixel 41 in the pixel array unit 51 into a digital signal under the control of the timing control circuit 55 and supplies the digital signal to the switch 53.
- the switch 53 opens and closes a path between the connection destination detection circuit 52 and the output control circuit 57.
- the four switches 53 arranged in each column supply the digital signal held in the connection destination detection circuit 52 to the output control circuit 57 in accordance with the control of a column driving circuit (not shown) that sequentially selects each column. To do.
- the row driving circuit 54 controls driving of each pixel 41 according to the control of the timing control circuit 55.
- the pixel array unit 51 is provided with four detection circuits 52A to 52D and switches 53A to 53D for one column of the pixels 41 arranged in a matrix.
- the row drive circuit 54 can simultaneously select and expose four adjacent rows to generate an analog electric signal.
- the electrical signals generated by the simultaneously selected four rows of pixels 41 are read out by the detection circuits 52A to 52D and converted into digital signals. When the reading is completed, the row driving circuit 54 performs the same control for the next four rows.
- the detection circuits 52A to 52D read out digital signals in units of four rows in the column direction, and when reading out all the rows of the pixel array unit 51 is completed, it corresponds to one frame, that is, one unit of light pulse detection. Image data to be output is output.
- the pixel array unit 51 is composed of 40000 pixels of 200 ⁇ 200, and it takes 16 microseconds ( ⁇ s) for processing of 4 rows, 50 times is required for one frame readout output. This process requires approximately 0.8 milliseconds (ms).
- the timing control circuit 55 controls the operation timing of the detection circuit 52, the row drive circuit 54, the reference voltage generation circuit 56, and the like. For example, the timing control circuit 55 generates a timing control signal indicating the scanning timing of the row and supplies the timing control signal to the row driving circuit 54. In addition, the timing control circuit 55 generates a DAC (Digital-to-Analog) control signal for controlling the reference voltage supply operation and supplies the DAC to the reference voltage generation circuit 56. The timing control circuit 55 supplies a detection control signal for controlling the operation of the detection circuit 52 to the detection circuit 52.
- DAC Digital-to-Analog
- the reference voltage generation circuit 56 generates a reference voltage Vref according to the DAC control signal and supplies the reference voltage Vref to each of the detection circuits 52.
- the detection circuit 52 converts an analog pixel signal into a digital signal by comparing the analog pixel signal (voltage thereof) supplied from the pixel 41 with a reference voltage Vref.
- the output control circuit 57 outputs a digital signal to the subsequent data processing unit 12 (FIG. 1). Although details will be described later, the output control circuit 57 performs error determination processing on the digital value corresponding to the light pulse detected by each pixel 41 of the pixel array unit 51, and after removing and correcting the error data. Output image data.
- the pixel 41 includes a photodiode 71, a storage node 72, a transfer transistor 73, an amplification transistor 74, a reset transistor 75, a detection node 76, and a selection transistor 77.
- a transfer transistor 73, the amplification transistor 74, the reset transistor 75, and the selection transistor 77 for example, an n-type MOS (Metal-Oxide Semiconductor) transistor is used.
- the photodiode 71 is a photoelectric conversion element that converts photons into electric charges.
- the photodiode 71 is connected to the transfer transistor 73 via the storage node 72.
- the photodiode 71 generates a pair of electrons and holes from photons incident on the silicon substrate on which the circuit of the pixel 41 is formed, and stores the electrons in the storage node 72.
- the transfer transistor 73 transfers the charge from the storage node 72 to the detection node 76 according to the control of the row drive circuit 54.
- the detection node 76 accumulates the charge from the transfer transistor 73 and generates an analog voltage corresponding to the amount of the accumulated charge. This voltage is applied to the gate of the amplification transistor 74.
- the reset transistor 75 is for initializing (resetting) the charge accumulated in the accumulation node 72 and the detection node 76 by extracting the charge to the power supply VDD.
- the reset transistor 75 has a gate connected to the row drive circuit 54, a drain connected to the power supply VDD, and a source connected to the detection node 76.
- the row drive circuit 54 controls the reset transistor 75 to be on at the same time as the transfer transistor 73 to draw out the electrons accumulated in the accumulation node 72 to the power supply VDD, and the pixel 41 is in a dark state before accumulation, that is, light. Is initialized to a non-incident state.
- the row drive circuit 54 controls only the reset transistor 75 to be in an on state, thereby extracting the charge accumulated in the detection node 76 to the power supply VDD and initializing the charge amount.
- the amplification transistor 74 amplifies the gate voltage.
- the amplification transistor 74 has a gate connected to the detection node 76, a drain connected to the power supply VDD, and a source connected to the selection transistor 77.
- the amplification transistor 74 forms a source follower with a constant current circuit 78 connected via the vertical signal line 58, and the voltage of the detection node 76 is output to the vertical signal line 58 with a gain of less than 1.
- the electric signal of the voltage is acquired by the detection circuit 52 including the AD converter 91.
- the selection transistor 77 outputs an electrical signal according to the control of the row drive circuit 54.
- the selection transistor 77 has a gate connected to the row drive circuit 54, a drain connected to the amplification transistor 74, and a source connected to the vertical signal line 58.
- the pixel 41 accumulates the photoelectrically converted charge in the period from when the photodiode 71 is reset to when reading is performed, and outputs a signal corresponding to the accumulated charge at the time of reading.
- the pixel 41 repeatedly performs accumulation and reading of such unit periods, and when a light pulse is incident during the accumulation, the result can be obtained at the time of reading.
- the type of photodiode 71 is preferably a buried photodiode that is completely depleted when charge is discharged by reset.
- a feature of the embedded photodiode 71 is that the detection node 76 and the storage node 72 of the photodiode 71 are not capacitively coupled during reading. As a result, the conversion efficiency improves as the parasitic capacitance of the detection node 76 is reduced, and the sensitivity to the incidence of one photon can be improved. Further, even if the photodiode 71 is enlarged, the conversion efficiency does not deteriorate. Therefore, as the photodiode 71 is made larger, the sensitivity per pixel for the same luminous flux density is improved. Note that the same property is also observed in MOS type photoelectric conversion elements.
- the pixel 41 configured as described above does not involve electron multiplication such as APD, SiPM, and high electron multiplier. Therefore, the output of the pixel 41 is affected by the readout noise caused by the amplification transistor 74 and the AD converter 91 in the detection circuit 52.
- the influence is relative. Can be minimized. That is, by reducing the parasitic capacitance of the detection node 76 as much as possible and enlarging the photodiode 71 as much as possible within a range where one electron transfer is possible, the SN ratio of the pixel 41 is maximized, and as a highly sensitive detector.
- the pixel 41 can be realized.
- the radiation counter 1 measures, for example, a weak emission pulse composed of, for example, several thousand photons 32 generated by photoelectrically absorbing one radiation 31 by the scintillator 21.
- the photodetector 23 receives a weak light emission pulse to be measured by a pixel array unit 51 including a plurality of pixels 41, and each pixel 41 generates an independent output according to the amount of light received.
- the output of each pixel 41 is converted into a digital value having a gradation larger than 1 bit by the AD converter 91. Furthermore, each pixel 41 can detect a plurality of photons.
- FIG. 4 shows an example of a digital value after the AD signal is output from the electric signal output from each pixel 41 by the AD converter 91.
- the AD converter 91 converts the photon signal into a digital value having a gradation such that the one-photon signal is output as 10 LSB, and outputs the digital value.
- LSB is a minimum output unit of a digital value.
- the output digital value includes readout noise in addition to the value corresponding to the photon signal. That is, the pixel output is a value obtained by combining the photon signal and the readout noise. Therefore, a negative value may be output due to noise. In the output example of FIG. 4, the negative value is described as it is, but the whole process may be offset, or the negative value may be rounded up to zero.
- the photodetector 23 is an aggregate of pixels 41 that are high-sensitivity photodetector cells each having a gradation output. Since each pixel 41 of the photodetector 23 does not perform electron multiplication by a strong electric field like APD or Si-PM, the output signal is very small. Therefore, since the output signal has significant readout noise, the number of incident photons in each pixel 41 is ambiguous. However, by combining these pixel outputs, it is possible to derive a pulse light amount corresponding to one radiation with high accuracy.
- the pixel 41 when the radiation passes through the scintillator 21 and is directly incident on the pixel array unit 51, or when a defective pixel is generated in the pixel array unit 51, the pixel 41 has a large output. Generate a signal locally. Therefore, a large output signal generated locally needs to be excluded as an abnormal output signal.
- the photodetector 23 has a function of selecting and discarding only the abnormal signal by paying attention to the difference in distribution in the pixel array unit 51 between the normal signal and the abnormal signal. In other words, the photodetector 23 performs processing to regard that a large output signal generated locally cannot be statistically present from a normal signal.
- High electron multipliers and normal APDs detect pulsed light with a single detector and generate analog pulses according to the amount of light.
- SiPM receives pulsed light at the pixel array, but only pixels where photons are incident output binary constant charge pulses. The final output intensity is determined by the number of pixels fired. That is, the high electron multiplier, APD, SiPM, and the like are not performed by the photodetector 23 because the two-dimensional lattice-like pixels 41 do not perform gradation output unlike the photodetector 23. It is not possible to perform the process of judging the output value abnormality from the distribution in the pixel array unit 51 and excluding it.
- FIG. 5 and FIG. 6 show an estimation example of pixel output composed of normal signals.
- the scintillator 21 emits light emitted from three types of radioactive materials Tc (technetium) 99m, Cs (cesium) 137, and K (potassium) 40, and 80% of the total light emission amount is detected by the photodetector 23.
- Tc technetium
- Cs cesium
- K potassium
- the total light yield of the scintillator is a characteristic value determined by the scintillator 21, and the incident rate to the photodetector and the quantum efficiency of the photodetector are light determined by the structure of the partition wall 22 and the pixel 41. This value is unique to the detector 23.
- the output signal probability of 99.999% is covered as a normal signal.
- a pixel signal exceeding 8e ⁇ may be regarded as some error. If a margin for the readout noise is added to the pixel signal exceeding 8e ⁇ , for example, as 3e ⁇ , 11e ⁇ can be set as the abnormal signal threshold. That is, the photodetector 23 discards the output signal exceeding 11e ⁇ from the output signal of the entire frame, so that the influence of the false signal can be almost completely removed while capturing a normal signal.
- the threshold value can be set flexibly in consideration of the error rate allowed for the device and the convenience of determination. For example, in many cases, even when a threshold value is set to about 100e-, most error elements can be removed.
- the total noise in the 200 ⁇ 200 pixel array unit 51 is calculated at 100 e-rms.
- the combination of the total noise and the variation in the effective incident photon number N is the noise of the photodetector 23, and the energy resolution Rp of the photodetector 23 calculated by the half-value width [%] is estimated as follows.
- FIG. 7 shows the energy resolution Rp of the photodetector 23 for three types of radioactive substances Tc99m, Cs137, and K40 when the readout noise ⁇ n of each pixel 41 is 0.5 e-rms.
- FIG. 8 is a block diagram relating to an error determination process for removing an abnormal signal as an error.
- the error determination process can be executed by the output control circuit 57 in the photodetector 23.
- the output control circuit 57 includes a comparator 101, a threshold register 102, an error counter 103, an adder 104, a sum signal register 105, and a signal correction unit 106.
- a light pulse incident on a predetermined pixel 41 of the pixel array unit 51 is photoelectrically converted into an analog pixel signal and supplied to a detection circuit 52 corresponding to the pixel 41.
- the AD converter 91 of the detection circuit 52 converts the supplied analog pixel signal into a digital value having a gradation larger than 1 bit, and supplies the digital value to the comparator 101 of the output control circuit 57.
- the comparator 101 determines whether the pixel output value is an error by comparing the digital value, which is the pixel output value of the predetermined pixel 41 supplied from the detection circuit 52, with the threshold value read from the threshold value register 102. . As a result of the comparison between the pixel output value and the threshold value, the comparator 101 discards the pixel output value and increments the count value of the error counter 103 when the pixel output value is larger than the threshold value and is determined to be an error. . On the other hand, when the comparator 101 determines that the pixel output value is not an error, the comparator 101 supplies the pixel output value to the adder 104.
- the threshold register 102 stores a plurality of different threshold values for each application and supplies them to the comparator 101 as necessary.
- the error counter 103 increments or resets an internal counter based on a command supplied from the comparator 101.
- the adder 104 adds the pixel output value supplied from the comparator 101 and the sum value supplied from the sum signal register 105, and supplies the addition result to the sum signal register 105.
- the sum signal register 105 supplies the sum value stored therein to the adder 104 and overwrites and stores the sum value newly supplied from the adder 104 over the previously stored value. Further, the sum signal register 105 supplies the stored sum value to the signal correction unit 106 when the sum corresponding to one frame is completed.
- the error counter 103 stores the number of times that the pixel output value is determined to be an error (count value) and supplies it to the signal correction unit 106.
- the signal correction unit 106 executes a correction process for correcting the sum value supplied from the sum signal register 105 to a sum value corresponding to one frame based on the error count value supplied from the error counter 103. Specifically, when the total number of pixels 41 in the pixel array unit 51 is M and the number of errors is E, the sum value stored in the sum signal register 105 is the total output value of (ME) pixels. . The signal correction unit 106 corrects the sum value stored in the sum signal register 105 by M / (ME) to a sum value corresponding to M pixels. However, when E is sufficiently smaller than M, this correction can be omitted.
- the output control circuit 57 is sequentially supplied with the pixel output value of each pixel 41 of the pixel array unit 51 corresponding to one frame in a predetermined order such as a raster scan order. Is started, for example, when the pixel output of the first pixel 41 for one frame is supplied.
- step S1 the comparator 101 determines whether or not the supplied pixel output value of the predetermined pixel 41 is larger than the threshold value read from the threshold value register 102, whereby the pixel output value is an error. Determine whether.
- step S1 If it is determined in step S1 that the supplied pixel output value is greater than the threshold value and an error has occurred, the process proceeds to step S2, and the comparator 101 discards the pixel output value and counts the error counter 103. Increments the value (error count value).
- step S ⁇ b> 1 if it is determined in step S ⁇ b> 1 that the supplied pixel output value is equal to or smaller than the threshold value and not an error, the process proceeds to step S ⁇ b> 3, and the comparator 101 supplies the pixel output value to the adder 104. .
- the adder 104 adds the pixel output value supplied from the comparator 101 and the sum value acquired from the sum signal register 105, and supplies the sum value after the addition to the sum signal register 105.
- the sum signal register 105 overwrites and stores the sum value supplied from the adder 104 as a new sum value.
- step S5 the output control circuit 57 determines whether the pixel output values of all the pixels 41 corresponding to one frame are compared with the threshold value.
- step S5 If it is determined in step S5 that all the pixels for one frame have not been compared, the process returns to step S1. Then, the above-described processing of steps S1 to S5 is repeated for the pixel output value supplied from the detection circuit 52 next.
- step S5 if it is determined in step S5 that all the pixels for one frame have been compared, the process proceeds to step S6, and the signal correction unit 106 adds up based on the error count value supplied from the error counter 103. The total value supplied from the signal register 105 is corrected to a total value corresponding to one frame. Then, the signal correction unit 106 supplies the sum signal indicating the sum after correction to the subsequent data processing unit 12 as an output signal of the photodetector 23, and ends the error determination process.
- the output control circuit 57 compares the pixel output value with the threshold value read from the threshold value register 102, discards the error pixel output value, and determines the pixel output value determined as a normal signal.
- a sum signal is output by summing only. Thereby, weak pulse light can be detected more accurately, and radiation counting can be performed more accurately.
- the output control circuit 57 corrects and outputs the signals for the pixels discarded as errors.
- this correction process can be omitted depending on the number of error pixels.
- the error determination process described above is an example in which the determination of an abnormal signal is performed in units of one pixel, but the determination of an abnormal signal may be performed in units of two pixels or a small number of plural pixel groups.
- the photodetector 23 derives the total value of the pixel output values for each pixel group, and discards the total value for the pixel group that exceeds the threshold and does not add it to the total value.
- the pixel output value of the normal signal can be included in the discarded total value. Therefore, if the group unit is large, the pixel information is lost correspondingly. Therefore, when an abnormal signal is determined in units of pixel groups, the number of pixels constituting one pixel group is desirably 1/100 or less of all pixels.
- the output control circuit 57 adds all pixel data corresponding to one frame and outputs the result to the data processing unit 12 at the subsequent stage.
- the addition output unit may be a row or a plurality of rows.
- a block composed of a plurality of pixels may be used.
- the pixel output values corresponding to the number of pixels in the pixel array unit 51 can be added except for errors in the subsequent data processing unit 12 or the like, and the pulse light amount can be derived using the sum.
- the output control circuit 57 in the photodetector 23 executes the error determination process.
- the data processing unit 12 subsequent to the photodetector 23 may execute the error determination process. .
- the error determination process described above is also effective in removing the influence of white spots, blinking white spots, or irregularly generated burst noise, which are initial defects of pixels formed on a semiconductor substrate. Further, this error determination process is not limited to radiation counting, and can be applied to general measurement of minute light pulses.
- the threshold at that time can be derived according to the Poisson cumulative distribution from the average pixel signal ⁇ s expected from the upper limit of the pulse intensity to be measured.
- the pixel on which one photon is incident has a fluctuation corresponding to readout noise around 10 LSB corresponding to one photon signal in the output distribution shown in FIG.
- a read noise of 0.4 e-rms corresponds to 4 LSBs.
- fluctuations larger than 8 LSBs, which is 2 ⁇ occur, and the probability that a signal smaller than 2 LSBs is output is 98% or less. That is, even if a signal smaller than 2 LSB is regarded as a no-signal by the error determination processing and removed from the count, 98% of the photon signal is acquired, and thus the sensitivity is slightly reduced.
- a non-signal pixel with no photon incidence has the same fluctuation centering on 0 LSB, but if a pixel of 2 LSB or less is treated as a non-signal pixel, 98% of the fluctuation component is filtered.
- FIG. 10 is a block diagram relating to error determination processing in the case where thresholds are provided not only for the upper limit threshold but also for the lower limit.
- the threshold register 102 in FIG. 8 is replaced with an upper threshold register 102A and a lower threshold register 102B in FIG.
- the upper limit threshold register 102A stores an upper limit threshold (upper limit threshold) which is the same threshold as the threshold register 102 in FIG. 8, and supplies it to the comparator 101 as necessary.
- the lower limit threshold register 102B stores a lower limit threshold (lower limit threshold), which is a threshold different from the threshold register 102 of FIG. 8, and supplies it to the comparator 101 as necessary.
- the upper limit threshold register 102A and the lower limit threshold register 102B also store a plurality of upper limit thresholds or lower limit thresholds that are different for each application.
- FIG. 11 is a flowchart of error determination processing executed by the output control circuit 57 shown in FIG.
- the error determination process of FIG. 11 is obtained by replacing step S1 of the error determination process of FIG. 9 with step S1A.
- step S1A the comparator 101 determines whether or not the supplied pixel output value of the predetermined pixel 41 is outside the range between the upper threshold value read from the upper threshold register 102A and the lower threshold value read from the lower threshold register 102B. By determining, it is determined whether the pixel output value is an error.
- step S1A If it is determined in step S1A that the supplied pixel output value is out of the upper limit threshold value and lower limit threshold value and is an error, the process proceeds to step S2. On the other hand, when it is determined that the supplied pixel output value is within the range between the upper limit threshold and the lower limit threshold, the process proceeds to step S3.
- steps S2 to S6 Since the processing of steps S2 to S6 is the same as the error determination processing described with reference to FIG. 9, detailed description thereof is omitted, but pixel output values outside the upper threshold and lower threshold values are considered errors. The error count value is incremented. Then, the pixel output values within the range between the upper limit threshold and the lower limit threshold are summed, corrected to a sum corresponding to one frame, and supplied as an output signal of the photodetector 23 to the subsequent data processing unit 12.
- the pulse light quantity detection accuracy can be further improved.
- FIG. 12 is a timing chart showing an operation sequence of the pixel 41.
- the row driving circuit 54 controls both the transfer transistor 73 and the reset transistor 75 to be in an on state at a timing T1 immediately before the exposure period. By this control, all the charges accumulated in the accumulation node 72 between the photodiode 71 and the transfer transistor 73 are discharged to the power supply VDD. This control is hereinafter referred to as “PD reset”.
- the row drive circuit 54 controls the transfer transistor 73 to be in an off state.
- the storage node 72 is in a floating state, and new charge accumulation is started.
- the row driving circuit 54 controls the reset transistor 75 to be turned off after the PD reset. Note that the reset transistor 75 may remain on during charge accumulation.
- the selection transistor 77 is controlled to be in an off state in order to allow access to other pixels 41 connected to the vertical signal line 58.
- the row driving circuit 54 controls the reset transistor 75 and the selection transistor 77 to be in an on state.
- the selection transistor 77 is turned on, the selected pixel 41 is connected to the vertical signal line 58.
- the reset transistor 75 is turned on, the detection node 76 that is the input of the amplification transistor 74 and the power supply VDD are short-circuited. Thereby, a reference potential is generated in the selected pixel 41.
- the row driving circuit 54 controls the reset transistor 75 to be in an off state.
- the potential of the detection node 76 is somewhat lowered from the reference potential due to coupling with the gate of the reset transistor 75, and enters a floating state. Furthermore, significant kTC noise is generated at the detection node 76 at this time. Since a floating diffusion layer (Floating Diffusion) is generally used as the detection node 76, the control for resetting the potential of the detection node 76 by turning on the reset transistor 75 is hereinafter referred to as “FD reset”.
- Detecting circuit 52 performs sampling N times (for example, 4 times) between the FD reset and the end of an exposure period to be described later. In these samplings, the signal of the potential of the vertical signal line 58 is converted into a digital signal Ds1 as a reset signal by the AD converter 91 of the detection circuit 52. Multiple sampling of the reset signal is handled as the first reading in correlated double sampling.
- the row driving circuit 54 controls the transfer transistor 73 to be in an on state.
- the electric charge accumulated in the accumulation node 72 is transferred to the detection node 76.
- the row driving circuit 54 controls the transfer transistor 73 to be in an OFF state.
- the potential of the detection node 76 decreases by the amount of accumulated charge (that is, the potential becomes shallower) than before the transfer transistor 73 is driven.
- the voltage corresponding to the fall is amplified by the amplification transistor 74 and output to the vertical signal line 58.
- the detection circuit 52 performs sampling N times (for example, four times). In these samplings, the signal of the potential of the vertical signal line 58 is converted into a digital signal Ds2 as an accumulated signal by the AD converter 91 of the detection circuit 52. Multiple sampling of the accumulated signal is handled as the second reading in correlated double sampling.
- the detection circuit 52 compares the digital signal Ds2 that is the sampled accumulated signal and the digital signal Ds1 that is the reset signal, and calculates a pixel output value corresponding to the amount of incident photons based on the comparison result.
- the detection circuit 52 adds all of the plurality of sampled digital signals Ds1 and calculates an average value thereof. Similarly, a plurality of sampled digital signals Ds2 are all added, and an average value thereof is calculated. The detection circuit 52 obtains a difference between the average value of the digital signal Ds1 and the average value of the digital signal Ds2 as a net accumulated signal. This net accumulated signal becomes the pixel output value corresponding to the amount of incident photons. The kTC noise generated at the time of FD reset is canceled by using the difference between the digital signals Ds1 and Ds2 as a net accumulated signal.
- noise can be reduced by sampling the digital signals Ds1 and Ds2 N times (multiple times), but the number of times of sampling may be one.
- the average of these may not be calculated, and the total value may be processed as an N-fold signal.
- the exposure period of each pixel 41 is a period between the above-described reset operation and readout operation.
- the transfer transistor 73 is turned off after being turned on at timing T1 and then turned on and turned off at timing T4. It is a period.
- the generated charge becomes a net stored signal represented by the difference between the reset signal and the stored signal, and is derived by the detection circuit 52 according to the procedure described above. Is done.
- the time from the end of exposure until the next timing T1 arrives and the exposure starts is a dead period. If the generation of the dead period is inconvenient in terms of the sensitivity of the apparatus, the read line may be immediately PD reset. Alternatively, the PD reset may be omitted, and the charge transfer at the timing T4 may be combined with the PD reset at the timing T1. If the PD reset is omitted, the next charge accumulation in the photodiode 71 is started immediately after the charge transfer at the completion of exposure. As a result, the dead period becomes zero. In this case, the exposure time is determined by the frame rate.
- each pixel 41 connected to each of the detection circuits 52A to 52D in the pixel array unit 51 is regarded as a pixel group and data processing is performed in units of pixel groups, the above-described reading process is greatly simplified. Can do. That is, there are 50 pixels 41 connected to each detection circuit 52A in the pixel array unit 51, and there are 50 detection circuits 52B to 52D. A process of adding the pixel output value for each pixel group with respect to the reset signal and the accumulation signal with the 50 pixels 41 as a pixel group and using the difference as a total output of the net accumulation signal of the pixel group is performed for each detection circuit 52A. To 52D can be easily implemented. Therefore, it is not necessary to transfer the data group AD-converted in units of four rows to the output control circuit 57, and each pixel group may transfer the total output of the net accumulated signal once per frame.
- the output control circuit 57 When the readout process is performed in units of pixel groups, the output control circuit 57 also executes error determination processing in units of pixel groups.
- the number of pixels constituting one pixel group is preferably 1/100 or less of all pixels as described above. In the present embodiment, since the number of shared pixels of each of the detection circuits 52A to 52D is 50, the number of pixels constituting one pixel group is 1/800 of all the pixels of the pixel array unit 51 of 200 ⁇ 200. 1/100 or less.
- FIG. 13 is a timing chart showing a procedure for reading pixel data of one frame.
- the vertical axis in FIG. 13 is the row address, and the horizontal axis is the time.
- reading of pixel data in units of four rows is performed for all pixels at the same time interval.
- the pixel rows of the pixel array unit 51 are simultaneously selected in units of four rows and sequentially accessed from the lower address. In the lower row, the pixel output is described as a total value of four rows.
- each pixel 41 is PD reset immediately after reading, and detection of minute pulse light is started. Then, after a certain unit detection period T ACC has elapsed, reading is sequentially performed. The light emission pulse incident in the unit detection period T ACC from the end time of the reading T RD 1 to the start time of the next reading T RD 2 is output as frame data in the reading of the reading T RD 2.
- the incidence frequency of radiation that is, the generation frequency of the light emission pulse
- the unit detection period T ACC can be set sufficiently long with respect to the readout period, or when the generation timing of the light emission pulse can be controlled by an external device, There is no problem in the read operation as shown in FIG.
- FIG. 14A is a diagram showing an example in the case where there are a plurality of pulse emission during the unit detection period T ACC .
- FIG. 14A shows a state in which two radiations are incident on the scintillator 21 and pulsed during the unit detection period T ACC from the end time of the read T RD 2 to the start time of the next read T RD 3. It is shown. In this case, correct radiation energy cannot be obtained from the pixel data read in the reading T RD 3.
- the photodetector 23 copes with such a problem by shortening the accumulation time of the pixel 41, that is, the unit detection period T ACC . That is, firstly, an error generation rate allowable in the photodetector 23 is determined in advance. When an error rate higher than a predetermined error rate is predicted from the measurement data, the photodetector 23 shortens the unit detection period T ACC and increases the frequency of reading.
- the error occurrence rate can be predicted from the light emission pulse count rate assuming that it also follows the Poisson distribution.
- FIG. 15A is a graph showing the emission pulse count rate Ps with respect to the average emission frequency ⁇ p of emission pulses in the unit detection period T ACC .
- the count rate Ps of the light emission pulses is a rate at which the light emission pulses are detected, and is a probability that one or more light emission occurs during the unit detection period TACC .
- the difference between the solid line and the broken line in FIG. 15A is a false detection.
- the emission pulse count rate Ps 0.08
- the actual average number of times of light emission ⁇ p is expected to be 0.0834.
- the ratio of energy detection is 0.0767 indicated by a broken line.
- the difference 0.0033 at this time is the occurrence probability of erroneous detection, and corresponds to 4.1% of the count rate Ps of the light emission pulses.
- the count rate Ps of the light emission pulse is 8%
- the error occurrence rate is 4.1%
- light emission is performed twice or more at 4.1% of the counted pixel data, and there is an error in energy detection. Can be determined to have occurred.
- FIG. 15B is a graph showing the relationship between the count rate Ps of the light emission pulses and the error occurrence rate at that time.
- the light emission pulse count rate Ps is 2% or less.
- the accumulation time of the pixel 41 that is, the unit detection period T ACC may be shortened to shorten the detection cycle.
- FIG. 16 shows a flowchart of a detection cycle control process for controlling the unit detection period T ACC based on an allowable error occurrence rate. This process is started, for example, when the radiation counting apparatus 1 performs radiation counting.
- the radiation counting apparatus 1 performs a predetermined number of times of sampling (that is, detection of a light emission pulse) at a predetermined sample rate.
- the photodetector 23 performs sampling a total of 500 times at a sample rate of 100 times / second.
- the data processing unit 12 counts radiation based on the pixel output value from the photodetector 23.
- the photodetector 23 performs a predetermined number of samplings at a predetermined initial sample rate.
- a predetermined number of times of sampling is executed at a sample rate corresponding to the processing result of step S24, S26, or S27 described later.
- step S23 the data processing unit 12 determines whether the calculated emission pulse count rate Ps is within a specified range. For example, when the allowable error occurrence rate is determined to be 3%, the count rate Ps of the corresponding light emission pulse is about 6% from the graph shown in FIG. For example, a range of 3% to 6% is set as the specified range of the counting rate Ps of the light emission pulses. In this case, the data processing unit 12 determines whether or not the calculated emission pulse count rate Ps is within a range of 3% to 6%.
- step S23 When it is determined in step S23 that the calculated emission pulse count rate Ps is within the specified range, the process proceeds to step S24, and the data processing unit 12 stores the radiation count result. The stored radiation count results are used to derive the energy profile.
- step S23 if it is determined in step S23 that the calculated emission pulse count rate Ps is smaller than the specified range, for example, in the above-described example in which the allowable error rate is determined to be 3%. If the count rate Ps of the light emission pulses is 2%, the process proceeds to step S25, and the data processing unit 12 stores the radiation count result. In step S ⁇ b> 26, the data processing unit 12 changes the sample rate to a sample rate at which the accumulation time is longer than the current time, and supplies the changed sample rate to the photodetector 23. By extending the accumulation time, the amount of data processing and power consumption can be reduced.
- step S23 if it is determined in step S23 that the calculated emission pulse count rate Ps is greater than the specified range, for example, in the above-described example in which the allowable error rate is determined to be 3%. If the count rate Ps of the light emission pulses is 7%, the process proceeds to step S27, and the data processing unit 12 changes the sample rate to a sample rate at which the accumulation time is shorter than the current time, and changes the changed sample rate. This is supplied to the photodetector 23. Therefore, when it is determined that the calculated emission pulse count Ps is larger than the specified range, the radiation count result is not stored and discarded.
- step S24, S26, or S27 the process returns to step S21, and the processes of steps S21 to S27 described above are repeated.
- the above detection cycle control processing is continuously executed until the radiation counting device 1 finishes counting the radiation, and is terminated when the counting of radiation is terminated by, for example, a user instruction operation.
- the detection cycle control process if the calculated emission pulse count rate Ps is smaller than the specified range, the accumulation time is extended to lower the sample rate, and if larger than the specified range, the accumulation time is decreased. Control for shortening and increasing the sample rate is executed.
- the minimum value of the unit detection period T ACC is 0, and the timing chart at that time is as shown in FIG.
- the period of reading TRD of one frame is 0.8 milliseconds
- the detection cycle is 0.8 milliseconds and the sample rate is 1,250 times / second.
- the sample rate can be further increased by using only a part of the pixel rows without using all the pixel rows of the pixel array unit 51.
- 50 times of read processing are executed by 4-row collective access to the pixel array unit 51 of 200 rows per frame.
- the number of reading processes is ended by five times. In such detection, since only 10% of the incident pulse light is detected, the energy resolution is deteriorated, but the sample rate is 10 times 12,500 times / second.
- the calculated emission pulse count rate Ps is maintained. There may be a case where it is determined that it is larger than the specified range. In this case, energy detection becomes difficult.
- the radiation dose is determined by the following process. It can be measured.
- the radiation counter 1 sets the count rate Ps_A1 to the count rate Ps_A1.
- a second count rate Ps_A2 larger than that is set.
- the data processing unit 12 of the radiation counting apparatus 1 shows the relational expression between the emission pulse count rate Ps and the average number of emission times ⁇ p shown in FIG. Accordingly, the average light emission number ⁇ p is calculated from the calculated light emission pulse count rate Ps.
- the emission pulse count rate Ps is about 0.63
- the data processing unit 12 is based on the relational expression between the emission pulse count rate Ps and the average emission count ⁇ p.
- the average light emission number ⁇ p is derived.
- the data processing unit 12 decreases the sample rate and derives an integral radiation dose.
- M is the number of radiations incident on each frame
- Ap is the average light quantity integrated value of the light emission pulses
- ⁇ p is the variation.
- M (Ap / ⁇ p) 2
- the data processing unit 12 obtains the number M of radiations using the average Ap of the light intensity integrated value for each frame and its variation ⁇ p.
- step S41 the radiation counting apparatus 1 performs a predetermined number of times of sampling at a predetermined sample rate, and calculates the count rate Ps of the light emission pulses.
- step S42 the radiation counting apparatus 1 determines whether the calculated count rate Ps of the light emission pulses is equal to or less than the first count rate Ps_A1.
- step S42 If it is determined in step S42 that the calculated emission pulse count rate Ps is equal to or less than the first count rate Ps_A1, the process proceeds to step S43, and the radiation counter 1 detects the detected emission pulse (single pulse). ) Is derived. After step S43, the process returns to step S41.
- step S42 determines that the calculated emission pulse count rate Ps is greater than the first count rate Ps_A1
- the process proceeds to step S44, and the radiation counting apparatus 1 determines that the current sample rate is the radiation count. It is determined whether the upper limit value of the device 1 is reached.
- step S44 If it is determined in step S44 that the current sample rate is not the upper limit value, the radiation counting apparatus 1 increases the sample rate and returns the process to step S41.
- step S44 determines that the sample rate is the upper limit value
- the process proceeds to step S46, and the radiation counting apparatus 1 determines that the calculated emission pulse count rate Ps is equal to or less than the second count rate Ps_A2. Determine if there is.
- step S46 When it is determined in step S46 that the calculated emission pulse count rate Ps is equal to or less than the second count rate Ps_A2, the process proceeds to step S47, and the radiation counting apparatus 1 calculates the average of the emission pulse count rate Ps.
- the radiation dose is derived by calculating the average number of light emission ⁇ p from the calculated light emission pulse count rate Ps according to the relational expression of the number of light emission ⁇ p.
- step S47 the process returns to step S41.
- steps S41 to S45 surrounded by a broken line correspond to the detection cycle control process in FIG.
- Such an accumulation time control method is not limited to the circuit configuration of the pixel 41 and the configuration of the photodetector 23 described with reference to FIG.
- the pixel includes a photoelectric conversion element, an accumulation unit that accumulates the photoelectrically converted charge in the pixel, an output unit that outputs the charge of the accumulation unit at a desired timing, and a reset unit that resets the charge of the accumulation unit
- the above-described accumulation time control method can be applied.
- FIG. 20 shows an example of pixel output when there is pulse light emission during the readout period.
- a minute light pulse is incident during the period of reading T RD 2.
- the incident minute light pulse is reflected as an accumulation signal only in the output of a part of pixels of one frame, and the remaining pixels are outputted as an accumulation signal in the next readout T RD 3 period.
- the Such a state can occur at a high frequency when the radiation dose increases and the unit detection period T ACC becomes shorter in the detection cycle control process of FIG.
- the data processing unit 12 determines the presence and intensity of the light emission pulse using the digital signal supplied from the photodetector 23 using a plurality of continuous frames.
- FIG. 21 shows read data for two frames when four rows are collectively read using four adjacent rows of the pixel array unit 51 as a read unit (block).
- FIG. 21A shows the read data of read T RD 1 as the first frame and the read data of read T RD 2 as the second frame.
- FIG. 21B shows the read data of read T RD 2 as the second frame and the read data of read T RD 3 as the third frame.
- one frame is divided into 50 blocks and read, and 2 frames are data for 100 blocks.
- the average signal amount of one block when incident is 80 [e ⁇ ].
- the readout noise is 0.5 [e ⁇ ] per pixel
- the output of one block when a minute light pulse is incident is represented by the average signal amount and the total readout noise, so that 80 ⁇ 14.14 [e ⁇ ], that is, an output of about 65 to 95 is obtained. Indicates that a minute light pulse is incident.
- the data processing unit 12 observes the output in units of blocks, and when one or a plurality of continuous blocks all exceed a prescribed determination threshold value, it is regarded as significant data and starts the optical pulse output. It is judged that.
- the determination threshold is, for example, 30 [e ⁇ ], which is approximately 2 ⁇ of the floor noise
- the data processing unit 12 determines that the output exceeds the specified determination threshold for four consecutive blocks as an optical pulse output. .
- the probability that a block without incident light pulses exceeds this is about 2.5%.
- the data processing unit 12 executes a determination process using the reading data of the reading T RD 1 and the reading data of the reading T RD 2.
- the signal amount exceeds the determination threshold at the 64th block, and pulse output is started.
- the determination threshold value is still exceeded even in the 100th block, it is detected that the pulse output has not ended and straddles the next frame (third frame). Therefore, the determination is suspended at this point.
- the data processing unit 12 executes a determination process using the read data of the read T RD 2 and the read data of the read T RD 3.
- the signal amount exceeds the determination threshold at the 14th block, and pulse output is started.
- the pulse output falls in the middle of the fourth frame across the third frame and the fourth frame.
- the data processing unit 12 adds the signal amount for 50 blocks (number of blocks corresponding to one frame) from the pulse start position to detect the light amount.
- the determination process at the end of reading of the next read T RD 4 is performed using the read data of the third frame and the fourth frame, but the pulse is started from the beginning (first block) of the third frame which is the previous frame. Instead of performing detection, detection of pulse output is started from the 14th block, which is a block where the end of pulse output is detected.
- the start position of the pulse output is detected, and the light amount detection is performed by adding the signal amount for a predetermined number of blocks from the detected start position, but the determination process is not limited to this example.
- the determination process is not limited to this example.
- the start of pulse output is detected, it is detected that the signal amount of a plurality of blocks continuously falls below the determination threshold, and the end of pulse output is detected, or the last four blocks (97 to 97) of two frames are detected.
- a process for detecting the signal amount and confirming that the pulse output has been completed for the 100th block may be added.
- the data processing unit 12 identifies the generation timing of data corresponding to the light emission pulse by confirming the signal amount in units of blocks read from the pixel array unit 51.
- the generation timing is specified by comparing the signal amount with the determination threshold over one block or a plurality of blocks.
- the signal amount may be added after executing the above-described error determination processing on the block unit data and discarding the error data.
- the amount discarded as error data is corrected by error determination processing and output.
- FIG. 22 is a timing chart showing an operation sequence of the pixel 41 enabling the global shutter.
- the row drive circuit 54 starts exposure by performing PD reset at timing T11. Then, at the timing T12 immediately after the start of exposure, the row drive circuit 54 controls the selection transistor 77 to be in an on state. Then, the detection circuit 52 samples the reset signal N times (for example, four times) during a period until the timing T13 when the selection transistor 77 is controlled to be turned off. By storing the reset signal sampling result for each pixel, FD reset at timing T2 in FIG. 12 and subsequent reset signal sampling are substituted.
- the row driving circuit 54 controls the transfer transistor 73 to be on. By this control, the electric charge accumulated in the accumulation node 72 is transferred to the detection node 76.
- the row drive circuit 54 controls the selection transistor 77 to be in an ON state.
- the detection circuit 52 samples the accumulated signal N times (for example, 4 times) until a timing T16 when the selection transistor 77 is controlled to be turned off.
- the exposure timings T11 and T14 and the signal sampling timings T12 and T15 are independent. Therefore, for example, even when a plurality of pixels 41 share the detection circuit 52, it is possible to perform a so-called global shutter operation in which exposure is started and ended at the same time, and reading is sequentially performed for each pixel.
- kTC noise generated at the time of FD reset in each pixel 41 (here, it is simultaneously performed at the time of PD reset at timing T11) is reduced. Cancel and get the net accumulated signal.
- one PD reset can be omitted and the dead period can be made zero.
- FIG. 23 is a timing chart when the operation sequence of FIG. 22 is transformed to a dead period zero.
- the transfer transistor 73 is not driven, only the reset transistor 75 is turned on, and only the FD (detection node 76) is reset while maintaining the charge of the photodiode 71. Then, when the charge of the photodiode 71 is transferred to the detection node 76 by the charge transfer at timing T14, the exposure period ends, and at the same time, this becomes a PD reset, and the next charge accumulation in the photodiode 71 is started. As a result, the dead time for detecting the pulsed light becomes zero, and the accumulation time becomes equal to the frame rate.
- the operation sequences shown in FIGS. 22 and 23 have the following characteristics.
- (First Step) Electric charges are discharged from the photodiode 71 of each pixel 41, and exposure is started for all the pixels at the same time.
- (Second Step) Next, the detection node 76 of each pixel 41 is reset.
- (Third Step) Next, a reset signal is read out to the detection circuit 52 for each pixel 41.
- (Fifth Step) Finally, the accumulated signal is read out to the detection circuit 52 for each pixel 41.
- the first step also serves as the fourth step and the next exposure is started immediately after the exposure is completed, an operation sequence with zero dead period is obtained.
- FIG. 24 illustrates a configuration example of the second embodiment of the radiation counting apparatus to which the present technology is applied.
- FIG. 24 is a perspective view of the radiation counting apparatus 1 according to the second embodiment corresponding to B in FIG.
- the radiation counting apparatus 1 also includes a light receiving unit 11 and a data processing unit 12.
- one scintillator 21 is made to correspond to the photodetector 23, and the scintillation light is diffused over the entire opening of the photodetector 23.
- the radiation counting apparatus 1 has a scintillator array 121 including four scintillators 21-C1 to 21-C4 with respect to the photodetector 23.
- the four scintillators 21-C1 to 21-C4 are optically separated from each other.
- the light receiving area of the photodetector 23 is divided into four areas 122-C1 to 122-C4 corresponding to the four scintillators 21-C1 to 21-C4 of the scintillator array 121.
- a light shielding portion 123 is provided between the adjacent region 122. The light shielding portion 123 prevents light leakage from the scintillators 21 other than the corresponding scintillators 21 in each of the four regions 122-C1 to 122-C4.
- the light shielding portion 123 can be omitted.
- pulsed photons generated by gamma rays incident on the scintillator 21-C1 reach only the corresponding region 122-C1.
- a plurality of pixels 41 are arranged in a two-dimensional lattice, and the scintillation light is received by the four regions 122- Implemented independently for each of C1 through 122-C4.
- the data processing unit 12 performs radiation counting, light amount measurement, energy determination, and the like for each region 122 based on the digital signal supplied from the photodetector 23.
- the scintillator array 121 corresponds to the photodetector 23, it is possible to cause spatial resolution in the photodetector 23.
- the set of the photodetector 23 and the scintillator array 121 is further tiled in the XY direction (a plurality of arrays are arranged in an array), so that a configuration of a radiation counting device with improved spatial resolution can be obtained. It is.
- the scintillator array 121 is composed of four 2 ⁇ 2 scintillators 21-C1 to 21-C4, but the X direction (horizontal direction) and Y direction (vertical direction) of the scintillator 21 ) Is not limited to this. That is, the scintillator array 121 only needs to have a plurality of scintillators 21 arranged therein.
- FIG. 25 shows a semiconductor substrate structure example of the photodetector 23.
- the photodetector 23 can be formed on one semiconductor substrate (for example, a silicon substrate), but can also be formed on two semiconductor substrates as shown in FIG. 25, for example.
- the photodetector 23 is configured by a laminated structure of two semiconductor substrates, an upper substrate 141 and a lower substrate 142.
- a pixel array unit 51 is formed on the upper substrate 141.
- a plurality of detection circuits 52, a row drive circuit 54, a reference voltage generation circuit 56, a timing control circuit 55, an output control circuit 57, and the like are formed on the lower substrate 142.
- the upper substrate 141 and the lower substrate 142 are stacked using a substrate bonding technique such as bonding of silicon wafers. Further, the upper substrate 141 and the lower substrate 142 are electrically connected by a metal bond such as a Cu—Cu bond, a through via, or the like.
- a plurality of detection circuits 52 are formed so that one detection circuit 52 corresponds to a pixel group 161 composed of four pixels close to each other in the pixel array unit 51. . That is, one detection circuit 52 on the lower substrate 142 is shared by a plurality of adjacent pixels 41 in the pixel array unit 51.
- the reason why the pixel group 161 is configured by a plurality of adjacent pixels 41 is that an abnormal value when radiation is directly incident is caused to occur in a plurality of adjacent pixels.
- Each detection circuit 52 sequentially AD-converts the output signals of the respective pixels 41 in the corresponding pixel group 161, further adds them, and supplies them to the output control circuit 57. That is, when one detection circuit 52 is provided for a pixel group 161 composed of a plurality of adjacent pixels in the pixel array unit 51, the detection circuit 52 outputs an output signal of each pixel 41 in the pixel group 161. In addition to AD conversion, the output signals of the pixels 41 in the pixel group 161 can be added together.
- the comparator 101 compares the output signal of the pixel group 161 supplied from the detection circuit 52 with the threshold value read from the threshold value register 102. Thus, it is determined whether or not the output signal of the pixel group 161 unit is an error. When the output signal of the pixel group 161 unit is larger than the threshold and it is determined that there is an error, the output signal is discarded.
- the output signals of the pixel groups 161 are further summed and stored in the sum signal register 105.
- the output signal stored in the summation signal register 105 is supplied to the signal correction unit 106.
- the signal correction unit 106 Based on the error count value supplied from the error counter 103, the signal correction unit 106 corrects the output signal supplied from the sum signal register 105 to an output signal corresponding to one frame, and outputs it to the subsequent stage.
- the ratio (aperture ratio) of the pixel array portion 51 in the photodetector 23 is increased, and the energy resolution is improved. Can do.
- the large scintillator 21 is disposed in front of the light receiving surface of the photodetector 23, most of the scintillation light can be received, and the radiation sensitivity can be increased.
- the light yield can be increased.
- the photodetector 23 can be mass-produced with the same manufacturing process on the same manufacturing line as the CMOS image sensor.
- the radiation counting apparatus 1 manufactured in this way is small and light, resistant to environmental fluctuations, stable in characteristics, and easy to maintain.
- the output of the radiation counting device 1 is a digital signal
- the subsequent circuit only needs to process the digital signal, is not easily affected by noise from the surroundings, and easily processes data output from a large number of light receiving units. can do.
- one detection circuit 52 is provided for the pixel group 161 including four pixels in the pixel array unit 51 in the lower substrate 142, but the detection circuit 52 is provided in units of pixels. It may be provided. In this case, for example, one frame is 16 ⁇ s, and all the pixels are collectively read once per frame. Then, the output signal of each pixel 41 is compared with a threshold value in units of one pixel to determine whether or not there is an error.
- circuit configuration of the pixel 41 shown in FIG. 3 is a configuration often adopted in a CMOS image sensor for a camera.
- the photodiode 71 For detecting weak light pulses such as scintillation, it is advantageous to increase the area of the photodiode 71 as much as possible as described above. On the other hand, the enlargement of the photodiode 71 makes it difficult to collect charges at the one-electron level by drifting the charge generated in the photodiode 71 by photoelectric conversion. If uncollected charges remain in the photodiode 71, it reduces the accuracy of light amount detection and at the same time becomes a noise generation source in the next detection. Such uncollected charges are generated by trapping charges with a certain probability in a potential dip caused by variations in impurity concentration in the photodiode 71. When the photodiode 71 becomes large and the internal electric field weakens, the capture probability increases.
- FIG. 26 shows another circuit configuration of the pixel 41, and shows a circuit provided with means for completely eliminating charges slightly existing in the photodiode 71 at the time of PD reset.
- 26 includes a photodiode 71, a transfer transistor 73, a detection node 76, and an amplification transistor 74 that amplifies and outputs the signal of the detection node 76, and further connects the detection node 76 to the power supply VDD.
- Reset transistor 75 and a second reset transistor 181 directly connected to the photodiode 71 and connected to the power supply VDD.
- FIG. 27 shows a planar layout of the pixel circuit shown in FIG.
- the number of the second reset transistors 181 may be one, but as shown in FIG. 27, a plurality of the second reset transistors 181 may be provided so that the remaining charges of the large-area photodiode 71 can be completely discharged. Since such second reset transistors 181 do not affect the parasitic capacitance of the detection node 76 at all, a flexible plurality of arrangements are possible.
- FIG. 28 is a timing chart showing an operation sequence of the pixel circuit shown in FIG.
- timing for turning on the second reset transistor 181 may be anywhere other than the exposure period.
- FIG. 29 is a timing chart showing an operation sequence of the pixel circuit of FIG. 26 when the dead period is zero.
- the timing at which the second reset transistor 181 is turned on may be the same as the timing T24 at which the transfer transistor 73 is turned on, or may be performed continuously before or after the transfer transistor 73 is turned on. Good.
- FIG. 29 shows a control example in which the second reset transistor 181 is turned on after the transfer transistor 73 is turned on.
- the row driving circuit 54 controls the selection transistor 77 to the on state, and then until the timing T23 at which the row driving circuit 54 is controlled to the off state, the detection circuit 52 performs N times (for example, four times).
- the reset signal is sampled.
- the detection circuit 52 stores the reset signal sampling result for each pixel.
- the row driving circuit 54 controls the transfer transistor 73 to be in an ON state. By this control, the electric charge accumulated in the accumulation node 72 is transferred to the detection node 76.
- the row drive circuit 54 controls the second reset transistor 181 to the ON state at timing T25. With this control, the charge of the photodiode 71 is completely discharged.
- the exposure period ends when the transfer transistor 73 that is turned on at timing T24 is controlled to be turned off, and the second exposure transistor 181 that is turned on at timing T25 is changed to the off state, and then the next exposure period starts. It becomes.
- the row driving circuit 54 controls the selection transistor 77 to be in an ON state. Then, until the timing T27 when the selection transistor 77 is controlled to be in the OFF state, the detection circuit 52 samples the accumulated signal N times (for example, 4 times). The detection circuit 52 stores the result of sampling the accumulated signal for each pixel. Then, the detection circuit 52 derives a net accumulation signal represented by the difference between the reset signal and the accumulation signal for each pixel.
- the discharge by the second reset transistor 181 completes the charge transfer by turning on the transfer transistor 73. Just after that.
- the operation sequence shown in FIG. 29 makes the readout sequence and the exposure timing independent, enabling flexible timing setting. Thereby, even when the detection circuit 52 is shared by a plurality of pixels, it is possible to introduce a so-called global shutter that simultaneously starts and ends the exposure of all the pixels.
- the pixel 41 discharges the accumulated charge in the photodiode 71 using both of them. More generally, the pixel 41 uses a plurality of transistors directly connected to the photodiode 71, and discharges accumulated charges of the photodiode 71 in conjunction with each other.
- the size of the photodiode 71 that requires the mounting of the second reset transistor 181 is generally 100 ⁇ m 2 or more.
- the photodetector 23 for detecting the weak light pulse can be applied to a device other than the radiation counting device described above. Therefore, a biopsy device will be described as an example in which the photodetector 23 is applied to a device other than the radiation counting device.
- FIG. 30 shows a configuration example of a flow cytometer as a biopsy device to which the present technology is applied.
- the flow cytometer 200 includes at least a photodiode 201 that detects forward scattered light 205 and a light detector 23 that detects side scattered light or fluorescence 206 emitted from a fluorescent marker attached to the specimen 203.
- Specimens 203 such as cells flowing from the sample tube 202 are arranged in a line in the sample flow 204, and a laser beam 207 is irradiated from the laser light source 209 there.
- a laser beam 207 is irradiated from the laser light source 209 there.
- fluorescence 206 excited from a fluorescent marker or the like and scattered light are generated.
- the forward scattered light 205 having a large amount of light is received by the photodiode 201, the size of the specimen 203 is detected, the timing of passing the specimen is acquired, and the event signal is generated.
- the fluorescence 206 or the side scattered light emitted from the fluorescent marker attached to the specimen 203 becomes weak pulse light and is detected by the photodetector 23.
- FIG. 31 shows how a weak pulse is detected by the photodetector 23 of the flow cytometer 200.
- each pulse shape 221 has one specimen. It corresponds to passage of 203.
- the forward scattered light 205 detected by the photodiode 201 also draws a pulse shape 222 with similar timing.
- the photodiode 201 compares the intensity of the forward scattered light 205 with a predetermined threshold value 231, detects the passage of the specimen 203 at the timing T31 when the intensity of the forward scattered light 205 becomes equal to or higher than the threshold value 231, and outputs the event signal 232. appear.
- the completion of exposure and data reading in the photodetector 23 are executed in synchronization with the event signal 232 passing through the specimen.
- the data read access sequence is a global shutter with almost no dead period, in accordance with FIG. At this time, in-pixel transfer is performed in synchronization with the specimen passing event signal 232, and the exposure period ends and readout starts. Further, the next exposure period starts all pixels at once.
- the photodetector 23 completes the exposure (accumulation) in each pixel 41 at a timing T32 after a certain delay considering the flow velocity and size of the specimen 203 from the acquisition of the event signal 232, and reads out the accumulated signal. To start. Further, at timing T32, the photodetector 23 starts the next exposure (accumulation).
- the total value of the pixel outputs in each readout sequence corresponds to the total amount of photons received by the photodetector 23 for each pulse. Thereby, the intensity of side light scattered light and fluorescence for each specimen 203 is derived.
- Such a photodetector 23 has a function of completing the accumulation of all effective pixels at a desired timing and outputting an accumulation signal. Further, the photodetector 23 starts the next accumulation immediately after the completion of the accumulation.
- the specimen passing event signal 232 is generated at the timing T31 that passes through the threshold 231 and increases, but may be generated at the timing T33 that passes through the threshold 231 and decreases.
- the generation at the timing T33 has an advantage that it can easily cope with the variation in the size and flow rate of the specimen 203.
- the event signal 232 may be generated using side scattered light and fluorescence 206. In that case, they may be dispersed and applied to another event generating element, or an event generating element may be separately mounted in the photodetector 23.
- Embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology.
- the photodetector 23 may be an independent device as an optical pulse detection device, for example, or may be incorporated as a part of a device other than the radiation counting device 1 and the flow cytometer 200.
- the present technology can take a cloud computing configuration in which one function is shared by a plurality of devices via a network and is jointly processed.
- each step described in the above flowchart can be executed by one device or can be shared by a plurality of devices.
- the plurality of processes included in the one step can be executed by being shared by a plurality of apparatuses in addition to being executed by one apparatus.
- a pixel array unit in which a plurality of pixels are arranged in a two-dimensional lattice;
- An AD converter for converting an output signal of each pixel of the pixel array unit into a digital value having a gradation larger than 1 bit;
- An optical pulse detection device comprising: a control circuit that performs an error determination process that compares the digital value with a first threshold value and discards the digital value that is larger than the first threshold value as an error.
- the control circuit further compares the digital value with a second threshold value different from the first threshold value, and performs an error determination process for discarding the digital value smaller than the second threshold value as no signal.
- the pixel is A charge storage unit that stores charges photoelectrically converted by the photoelectric conversion element; A reset transistor for resetting the charge of the charge storage unit; The optical pulse detection device according to any one of (1) to (5), further comprising: an output transistor that outputs the charge of the charge storage unit as the output signal.
- the pixel is The optical pulse detection device according to (6), further including a second reset transistor that is directly connected to the photoelectric conversion element and resets a charge of the photoelectric conversion element.
- the optical pulse detection device according to any one of (1) to (8), wherein the optical pulse detection device is configured by a laminated structure of a plurality of semiconductor substrates.
- a control circuit that performs an error determination process that discards the digital value that is larger than the threshold as an error.
- the optical pulse detection device Converting an output signal of each pixel of the pixel array unit into a digital value having a gradation larger than 1 bit;
- An optical pulse detection method for performing an error determination process of comparing the digital value with a predetermined threshold and discarding the digital value larger than the threshold as an error.
- the optical pulse detection device A scintillator and The light pulse detection device detects a light emission pulse emitted by radiation incident on the scintillator.
- a data processing unit that calculates the count rate of the light emission pulse from the number of times of the light emission pulse detected by the light pulse detection device, and controls the accumulation time of the pixel based on the calculated count rate of the light emission pulse
- the radiation counting apparatus further including: (13) The data processing unit, when it is determined that the calculated count rate of the light emission pulse is larger than a specified range, changes the sample rate to a sample rate at which the accumulation time of the pixel is shorter than the present time. Radiation counting device.
- the data processing unit controls to use only a part of the pixel rows of the pixel array unit when it is determined that the calculated count rate of the light emission pulse is larger than a prescribed range, The radiation counting apparatus according to (13), wherein the sampling rate is changed to a sample rate that is shorter than the current accumulation time. (15) When it is determined that the calculated count rate of the light emission pulse is greater than the first count rate and equal to or less than the second count rate, the data processing unit calculates an average from the calculated count rate of the light emission pulses. The radiation counting apparatus according to (12), wherein the number of times of light emission is calculated to derive a radiation dose.
- the radiation processing apparatus (16) The radiation processing apparatus according to (15), wherein the data processing unit derives an integral radiation dose when it is determined that the calculated counting rate of the emission pulse is larger than the second counting rate. . (17) The data processing unit determines that it is the start of light emission pulse output when the output signal of the readout unit exceeds a predetermined determination threshold, and derives the light amount of the light emission pulse.
- the radiation counting device according to (12), . (18) The scintillator is composed of a scintillator array in which a plurality of optically separated scintillators are arranged, The radiation counting apparatus according to any one of (11) to (17), wherein the pixel array unit includes a light receiving region corresponding to the plurality of scintillators.
- the radiation counting apparatus wherein the pixel array unit includes a light shielding unit between light receiving regions corresponding to the plurality of scintillators.
- the optical pulse detection device detects fluorescence or scattered light excited by irradiating a specimen in a fluid with laser light.
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Abstract
Description
1.放射線計数装置の第1の実施の形態(光検出器に対して1個のシンチレータを配置した構成例)
2.放射線計数装置の第2の実施の形態(光検出器に対して複数個のシンチレータを配置した構成例)
3.光検出器の半導体基板構造例
4.画素回路のその他の構成例
5.光検出器のその他の適用例
<1.1 放射線計数装置の構成例>
図1は、本技術を適用した放射線計数装置の第1の実施の形態の構成例を示している。
図2は、光検出器23の回路構成を示している。
次に、図3を参照して、画素41の回路構成について説明する。
放射線計数装置1は、例えば1個の放射線31がシンチレータ21に光電吸収されることによって生じた、例えば数千個の光子32よりなる微弱発光パルスを測定する。光検出器23は、測定対象の微弱発光パルスを、複数個の画素41よりなる画素アレイ部51で受光し、各画素41が受光量に応じて独立した出力を発生する。各画素41の出力は、AD変換器91で1ビットより大きな階調を持つデジタル値に変換される。さらに各画素41は、複数個の光子を検知することができる。
光検出器23が行う、画素アレイ部51の各画素41の画素出力から異常値を判断して除外するエラー判定処理について、詳しく説明する。
P(k)=(λs)k*e-λs/k!
である。図5に示されるポアソン累積分布は、k=0としたP(0)、k=1としたP(1)、k=2としたP(2)、・・・の累積である。
λs=N/総画素数
N=シンチレータの全光収率x放射線エネルギーxシンチレーション光の光検出器への入射率x光検出器の量子効率
図12を参照して、画素41の動作について説明する。図12は、画素41の動作シーケンスを示すタイミングチャートである。
次に、図13を参照して、4行単位で同時に画素出力を行う場合の画素アレイ部51全体の読み出し動作について説明する。
初めに、単位検出期間TACC中に複数のパルス発光がある場合の対処方法について説明する。
P(k)=(λp)k*e-λp/k!
で表すことができ、発光パルスの計数率Psは、確率P(k)のk=1からk=∞までの累積となる。その中で正しくエネルギー検出されているのはk=1の時のみであり、図15のAのグラフの破線に相当する。
図16は、許容できるエラー発生率に基づいて単位検出期間TACCを制御する検出周期制御処理のフローチャートを示している。この処理は、例えば、放射線計数装置1が放射線の計数を実行するとき開始される。
Ap=ηM
σp=η√M
であり、各フレームに入射される放射線個数Mは、
M=(Ap/σp)2
で表される。
(1)サンプルレートが上限値に到達するまで、発光パルスの計数率Psが第1の計数率Ps_A1以下となるように蓄積時間を短縮してサンプリングレートを上げていく第1段階、
(2)サンプルレートが上限値に到達してから、発光パルスの計数率Psが第2の計数率Ps_A2となるまで、算出された発光パルスの計数率Psから平均発光回数λpを算出し、放射線量を導出する第2段階、
(3)発光パルスの計数率Psが第2の計数率Ps_A2を超えてから、M=(Ap/σp)2により、積分的に放射線量を導出する第3段階
の3段階の工程に分けて、放射線量を検出することができる。
次に、読み出し期間中にパルス発光がある場合の対処方法について説明する。
(1)読み出したデータ群から、単一のパルス光入射に対応するデータを判定して抽出する判定処理の導入
(2)露光期間と読み出し期間を独立して制御し、露光の開始と終了を全画素一斉に実施する、所謂グローバルシャッタの導入
初めに、(1)の対処方法、即ち、読み出したデータ群から、単一のパルス光入射に対応するデータを判定して抽出する判定処理について説明する。
次に、(2)の対処方法、即ち、グローバルシャッタにより、読み出し期間中に非選択画素が露光されないようにする方法について説明する。
(第1の工程)各画素41のフォトダイオード71から電荷が排出され、全画素一斉に露光が開始される。
(第2の工程)次に、各画素41の検出ノード76がリセットされる。
(第3の工程)次に、リセット信号が、画素41ごとに検出回路52に読み出される。
(第4の工程)次に、フォトダイオード71の蓄積信号が検出ノード76に転送され、全画素一斉に露光が完了する。
(第5の工程)最後に、蓄積信号が、画素41ごとに検出回路52に読み出される。
図24は、本技術を適用した放射線計数装置の第2の実施の形態の構成例を示している。
図25は、光検出器23の半導体基板構造例を示している。
ところで、図3に示した画素41の回路構成は、カメラ用のCMOSイメージセンサにしばしば採用されている構成ではある。
微弱光パルスを検出する光検出器23は、上述した放射線計数装置以外にも適用することができる。そこで、放射線計数装置以外の装置に光検出器23を適用した例として、生体検査装置について説明する。
(1)
複数の画素が二次元格子状に配列された画素アレイ部と、
前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換するAD変換器と、
前記デジタル値を第1の閾値と比較し、前記第1の閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う制御回路と
を備える光パルス検出装置。
(2)
前記制御回路は、さらに、前記デジタル値を前記第1の閾値と異なる第2の閾値と比較し、前記第2の閾値より小さい前記デジタル値を無信号として破棄するエラー判定処理を行う
前記(1)に記載の光パルス検出装置。
(3)
前記制御回路は、前記第1の閾値以下の前記デジタル値を合算し、その結果得られる合算値を出力する
前記(1)に記載の光パルス検出装置。
(4)
前記制御回路は、前記第1の閾値以下の前記デジタル値を合算した合算値に対して、エラーとして破棄した画素分を補正して出力する
前記(1)または(3)に記載の光パルス検出装置。
(5)
前記制御回路は、前記エラー判定処理を、複数画素からなる画素グループ単位の前記デジタル値で行う
前記(1)乃至(4)のいずれかに記載の光パルス検出装置。
(6)
前記画素は、
光電変換素子により光電変換された電荷を蓄積する電荷蓄積部と、
前記電荷蓄積部の電荷をリセットするリセットトランジスタと、
前記電荷蓄積部の電荷を前記出力信号として出力する出力トランジスタと
を備える
前記(1)乃至(5)のいずれかに記載の光パルス検出装置。
(7)
前記画素は、
前記光電変換素子に直結され、前記光電変換素子の電荷をリセットする第2のリセットトランジスタをさらに備える
前記(6)に記載の光パルス検出装置。
(8)
前記画素は、前記第2のリセットトランジスタを複数備える
前記(7)に記載の光パルス検出装置。
(9A)
前記画素アレイ部は、露光の開始と終了を全画素同時に行う
前記(1)乃至(8)のいずれかに記載の光パルス検出装置。
(9B)
複数枚の半導体基板の積層構造で構成されている
前記(1)乃至(8)のいずれかに記載の光パルス検出装置。
(10)
複数の画素が二次元格子状に配列された画素アレイ部と、前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換するAD変換器と、前記デジタル値を所定の閾値と比較し、前記閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う制御回路とを備える光パルス検出装置が、
前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換し、
前記デジタル値を所定の閾値と比較し、前記閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う
光パルス検出方法。
(11)
前記(1)に記載の光パルス検出装置と、
シンチレータと
を備え、
前記光パルス検出装置は、放射線が前記シンチレータに入射されて発光した発光パルスを検出する
放射線計数装置。
(12)
前記光パルス検出装置で検出された前記発光パルスの回数から、前記発光パルスの計数率を算出し、算出された前記発光パルスの計数率に基づいて、前記画素の蓄積時間を制御するデータ処理部をさらに備える
前記(11)に記載の放射線計数装置。
(13)
前記データ処理部は、算出された前記発光パルスの計数率が規定範囲よりも大きいと判定された場合、前記画素の蓄積時間が現在よりも短くなるサンプルレートに変更する
前記(12)に記載の放射線計数装置。
(14)
前記データ処理部は、算出された前記発光パルスの計数率が規定範囲よりも大きいと判定された場合、前記画素アレイ部の一部の画素行のみを使用するように制御して、前記画素の蓄積時間が現在よりも短くなるサンプルレートに変更する
前記(13)に記載の放射線計数装置。
(15)
前記データ処理部は、算出された前記発光パルスの計数率が第1の計数率よりも大きく、第2の計数率以下であると判定された場合、算出された前記発光パルスの計数率から平均発光回数を算出し、放射線量を導出する
前記(12)に記載の放射線計数装置。
(16)
前記データ処理部は、算出された前記発光パルスの計数率が前記第2の計数率よりも大きいと判定された場合、積分的な放射線量の導出を行う
前記(15)に記載の放射線計数装置。
(17)
前記データ処理部は、読み出し単位の出力信号が規定の判定閾値を超えた場合、発光パルス出力の開始であると判定し、前記発光パルスの光量を導出する
前記(12)に記載の放射線計数装置。
(18)
前記シンチレータは、光学的に分離された複数のシンチレータが配列されたシンチレータアレイで構成されており、
前記画素アレイ部は、前記複数のシンチレータに対応する受光領域を有する
前記(11)乃至(17)のいずれかに記載の放射線計数装置。
(19)
前記画素アレイ部は、前記複数のシンチレータに対応する受光領域の間に遮光部を有する
前記(18)に記載の放射線計数装置。
(20)
前記(1)に記載の光パルス検出装置を備え、
前記光パルス検出装置は、流体内の検体にレーザ光が照射されることにより励起された蛍光または散乱光を検出する
生体検査装置。
Claims (20)
- 複数の画素が二次元格子状に配列された画素アレイ部と、
前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換するAD変換器と、
前記デジタル値を第1の閾値と比較し、前記第1の閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う制御回路と
を備える光パルス検出装置。 - 前記制御回路は、さらに、前記デジタル値を前記第1の閾値と異なる第2の閾値と比較し、前記第2の閾値より小さい前記デジタル値を無信号として破棄するエラー判定処理を行う
請求項1に記載の光パルス検出装置。 - 前記制御回路は、前記第1の閾値以下の前記デジタル値を合算し、その結果得られる合算値を出力する
請求項1に記載の光パルス検出装置。 - 前記制御回路は、前記第1の閾値以下の前記デジタル値を合算した合算値に対して、エラーとして破棄した画素分を補正して出力する
請求項1に記載の光パルス検出装置。 - 前記制御回路は、前記エラー判定処理を、複数画素からなる画素グループ単位の前記デジタル値で行う
請求項1に記載の光パルス検出装置。 - 前記画素は、
光電変換素子により光電変換された電荷を蓄積する電荷蓄積部と、
前記電荷蓄積部の電荷をリセットするリセットトランジスタと、
前記電荷蓄積部の電荷を前記出力信号として出力する出力トランジスタと
を備える
請求項1に記載の光パルス検出装置。 - 前記画素は、
前記光電変換素子に直結され、前記光電変換素子の電荷をリセットする第2のリセットトランジスタをさらに備える
請求項6に記載の光パルス検出装置。 - 前記画素は、前記第2のリセットトランジスタを複数備える
請求項7に記載の光パルス検出装置。 - 前記画素アレイ部は、露光の開始と終了を全画素同時に行う
請求項1に記載の光パルス検出装置。 - 複数の画素が二次元格子状に配列された画素アレイ部と、前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換するAD変換器と、前記デジタル値を所定の閾値と比較し、前記閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う制御回路とを備える光パルス検出装置が、
前記画素アレイ部の各画素の出力信号を1ビットより大きな階調のデジタル値に変換し、
前記デジタル値を所定の閾値と比較し、前記閾値より大きい前記デジタル値をエラーとして破棄するエラー判定処理を行う
光パルス検出方法。 - 請求項1に記載の光パルス検出装置と、
シンチレータと
を備え、
前記光パルス検出装置は、放射線が前記シンチレータに入射されて発光した発光パルスを検出する
放射線計数装置。 - 前記光パルス検出装置で検出された前記発光パルスの回数から、前記発光パルスの計数率を算出し、算出された前記発光パルスの計数率に基づいて、前記画素の蓄積時間を制御するデータ処理部をさらに備える
請求項11に記載の放射線計数装置。 - 前記データ処理部は、算出された前記発光パルスの計数率が規定範囲よりも大きいと判定された場合、前記画素の蓄積時間が現在よりも短くなるサンプルレートに変更する
請求項12に記載の放射線計数装置。 - 前記データ処理部は、算出された前記発光パルスの計数率が規定範囲よりも大きいと判定された場合、前記画素アレイ部の一部の画素行のみを使用するように制御して、前記画素の蓄積時間が現在よりも短くなるサンプルレートに変更する
請求項13に記載の放射線計数装置。 - 前記データ処理部は、算出された前記発光パルスの計数率が第1の計数率よりも大きく、第2の計数率以下であると判定された場合、算出された前記発光パルスの計数率から平均発光回数を算出し、放射線量を導出する
請求項12に記載の放射線計数装置。 - 前記データ処理部は、算出された前記発光パルスの計数率が前記第2の計数率よりも大きいと判定された場合、積分的な放射線量の導出を行う
請求項15に記載の放射線計数装置。 - 前記データ処理部は、読み出し単位の出力信号が規定の判定閾値を超えた場合、発光パルス出力の開始であると判定し、前記発光パルスの光量を導出する
請求項12に記載の放射線計数装置。 - 前記シンチレータは、光学的に分離された複数のシンチレータが配列されたシンチレータアレイで構成されており、
前記画素アレイ部は、前記複数のシンチレータに対応する受光領域を有する
請求項11に記載の放射線計数装置。 - 前記画素アレイ部は、前記複数のシンチレータに対応する受光領域の間に遮光部を有する
請求項18に記載の放射線計数装置。 - 請求項1に記載の光パルス検出装置を備え、
前記光パルス検出装置は、流体内の検体にレーザ光が照射されることにより励起された蛍光または散乱光を検出する
生体検査装置。
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US20180328783A1 (en) | 2018-11-15 |
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US10852183B2 (en) | 2020-12-01 |
JPWO2017086181A1 (ja) | 2018-10-04 |
CN108139268A (zh) | 2018-06-08 |
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