Signal readout circuit, signal readout device, and signal readout method for light detecting element

Abstract

The signal reading circuit (11) is a circuit that reads a signal from a light detection element (7) having a plurality of light detection pixels (71) that generate a detection signal in correspondence with the incidence of light, and includes N light incidence detection sections (13) that respectively input detection signals from N (N is an integer of 2 or more) light detection pixels (71) and output a signal indicating the incidence of light, and a total value detection section (14) that detects a total value of the output signals from the N light incidence detection sections (13). Each light incidence detection section (13) outputs a signal to which different weighting is applied in correspondence with each light detection pixel (71). The weight is set in such a manner that the total values are different from each other for each light detection pixel (71) and all combination patterns of the light detection pixels (71) with each other. Thus, a signal reading circuit, a signal reading device, and a signal reading method of a light detection element that can perform discrimination detection even when light is simultaneously incident at a plurality of positions while suppressing the increase in the circuit scale are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a signal readout circuit of a light detecting element, a signal readout apparatus, and a signal readout method. BACKGROUND

[0002] In Patent Literature 1, a technology related to a radiation detector is disclosed. The radiation detector includes a scintillator group including a plurality of scintillators coupled two-dimensionally and a light sensor optically coupled with the scintillator group, and detects an incident position of a gamma ray incident to the scintillator group. The scintillator group is configured so that each scintillator is in close contact with or close to each other. A plurality of light sensors are optically coupled with the scintillator group, and the incident position of the gamma ray is detected based on a center of gravity of a light amount distribution calculated based on a detected light amount detected at each light sensor.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 7-311270

[0006] NON-PATENT LITERATURE

[0007] Non-Patent Literature 1: Andrew L. Goertzen et al., "Design and Performance of a Resistor Multiplexing Readout Circuit for a SiPM Detector", IEEE Transactions on Nuclear Science, Vol. 60 No. 3, pp. 1541-1549 (2013)

[0008] Non-Patent Literature 2: Vladimir Popov et al., "A novel readout concept for multianode photomultiplier tubes with pad matrix anode layout", Nuclear Instruments and Methods in Physics Research, A 567, pp. 319-322 (2006) SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] For example, in reading out signals from a multi-channel type light detecting element such as a MPPC (Multi-Pixel Photon Counter) or a multi-anode PMT (Photomultiplier Tube), the most widely used method is a method using a resistance chain. Figure 14 Fig. 1 is an example conceptually showing the structure of a radiation detector using a resistance chain. The radiation detector 100 includes a scintillator group 101 composed of a plurality of scintillators 102 arranged in one dimension or two dimensions, and a multi-channel type light detecting element 103 attached to the scintillator group 101.

[0011] Each light detecting pixel (channel) 104 of the light detecting element 103 is electrically connected to each other by a resistance chain 105 composed of a plurality of resistors 106 connecting adjacent light detecting pixels 104 to each other. In the radiation detector 100, signals are read out from both ends of the resistance chain 105, and the incident position of light (i.e., the incident position of radiation) is determined based on the magnitude thereof. Such a method is particularly widely used for reading out signals from a multi-anode PMT, and is widely adopted in PET (Positron Emission Tomography) and radiation measuring instruments, etc.

[0012] However, in such a resistance chain method, there are the following problems. That is, since the signal processing for determining the incident position of light takes several tens to several hundreds of microseconds, the signal processing speed is slowed down in the response speed of the entire device, although the response speed of the detecting element itself is relatively fast (e.g., below 100 nanoseconds). In addition, in the case where light is simultaneously incident at a plurality of positions, they cannot be separately detected, and the incident position information is lost.

[0013] In view of these problems of the resistance chain method, a method is considered in which the same number of readout circuits as the number of light detecting pixels 104 is provided, and output signals from each light detecting pixel 104 are separately read out (see Fig. 2). Figure 15 However, in such a method, the scale of the readout circuits is enlarged in proportion to the number of light detecting pixels 104, and becomes a large circuit scale with respect to, for example, 64 or 256 such numbers of light detecting pixels.

[0014] The present embodiment aims to provide a signal readout circuit, a signal readout device, and a signal readout method of a light detecting element, which can separately detect light incident at a plurality of positions while suppressing the large-scale of the circuit, even in the case where light is simultaneously incident at a plurality of positions.

[0015] Method for solving the problem

[0016] The embodiment is a signal readout circuit of a light detecting element. The signal readout circuit of a light detecting element is a circuit that reads a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, characterized by comprising: N (N is an integer of 2 or more) light incidence detecting sections that respectively input detection signals from N light detecting pixels included in the plurality of light detecting pixels and output a signal indicating incidence of light, each light incidence detecting section outputting a signal to which different weighting is applied in correspondence with each light detecting pixel, the weight being set in such a manner that the sum total of the signals output from the N light incidence detecting sections differs for each combination of the light detecting pixels.

[0017] The embodiment is a signal readout method of a light detecting element. The signal readout method of a light detecting element is a method that reads a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, characterized by comprising: a first step of generating N signals indicating incidence of light based on signals respectively from N (N is an integer of 2 or more) light detecting pixels included in the plurality of light detecting pixels, each signal being generated in such a manner that different weighting is applied in correspondence with each light detecting pixel, the weight being set in such a manner that the sum total of the N signals differs for each combination of the light detecting pixels; and a second step of detecting the sum total of the N signals.

[0018] In the signal readout circuit and the signal readout method described above, when the signal indicating incidence of light is generated in the light incidence detecting section (first step), different weighting is applied in correspondence with each light detecting pixel, and the sum total of the N signals after the weighting is detected in the sum total detecting section (second step). The weight is set in such a manner that the sum total differs for each combination of the light detecting pixels.

[0019] In such a configuration, it is possible to uniquely determine from the sum total whether light has been incident on which light detecting pixel (one or a plurality of pixels). Therefore, according to the signal readout circuit and the signal readout method, even in the case where light is incident at a plurality of positions at the same time, it is possible to perform a differential detection of them. Furthermore, compared with the case where N signal readout circuits corresponding to the N light detecting pixels are provided, it is possible to suppress the increase in the scale of the circuit.

[0020] The embodiment is a signal readout device of a light detecting element. The signal readout device of the light detecting element is a device that reads out a signal from a light detecting element having M (M is an integer of 2 or more) light detecting pixel groups each including a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, the signal readout device of the light detecting element being characterized by: M signal readout circuits including a signal readout circuit of the above-described structure, the M signal readout circuits reading out signals from the M light detecting pixel groups, respectively.

[0021] According to the signal readout device, it is possible to perform a differential detection even when light is simultaneously incident from a plurality of positions while suppressing a large-scale of the circuit by making the M signal readout circuits signal readout circuits of the above-described structure. Further, it is possible to reduce the number N of light incident detection sections by dividing a large number of light detecting pixels of the light detecting element into the M light detecting pixel groups and providing the signal readout circuit for each light detecting pixel group, as compared with a case where a single signal readout circuit is used. Therefore, it is possible to suppress an excessive number of combination patterns realized by the N light detecting pixels.

[0022] Effects of the Invention

[0023] According to the signal readout circuit of the light detecting element, the signal readout device, and the signal readout method of the embodiment, it is possible to perform a differential detection even when light is simultaneously incident from a plurality of positions while suppressing a large-scale of the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a perspective view showing an external appearance of a radiation detector 1A of one embodiment.

[0025] Figure 2 is a perspective view showing an external appearance of a scintillator array 5.

[0026] Figure 3 is a perspective view showing an external appearance of a light detecting element 7.

[0027] Figure 4 is a plan view showing a light incident surface 7a of the light detecting element 7.

[0028] Figure 5 is a perspective view showing an external appearance of a signal readout device 10.

[0029] Figure 6 is a view schematically showing an internal structure of a signal readout circuit 11.

[0030] Figure 7 (a) of FIG. 1 is a view showing one light detecting pixel group 74, Figure 7 (b) of FIG. 1 is a view showing a relationship between Figure 7Fig. 2 is a diagram showing an example of weight values of the light incident detection sections 13 to which the four light detection pixels 71 shown in (a) of Fig. 1 correspond, respectively.

[0031] Figure 8 Fig. 3 is a diagram showing a table indicating a relationship of combinations of the channel number and the integrated value of the output signals from the N light incident detection sections 13 detected at the integrated value detection section 14.

[0032] Figure 9 Figs. 4(a) to 4(e) are diagrams conceptually showing examples of determining which light detection pixel 71 of the light detection element 7 a photo has been incident on.

[0033] Figure 10 Fig. 5 is a diagram conceptually showing an example of the operation of the signal readout circuit 11.

[0034] Figure 11 Fig. 6 is a diagram conceptually showing another example of the operation of the signal readout circuit 11.

[0035] Figure 12 Fig. 7 is a timing chart showing a signal readout method of one embodiment.

[0036] Figure 13 Fig. 8 is a plan view conceptually showing a modification example of the light incident surface 7a of the light detection element 7.

[0037] Figure 14 Fig. 9 is a diagram conceptually showing a structure of a radiation detector using a resistance chain.

[0038] Figure 15 Fig. 10 is a diagram conceptually showing a structure of a radiation detector having a configuration in which the same number of readout circuits as the number of light detection pixels are provided and output signals from the respective light detection pixels are individually read out. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of a signal readout circuit, a signal readout device, and a signal readout method of a light detection element will be described in detail with reference to the drawings. Note that the same reference numerals are applied to the same elements throughout the drawings, and repetitive description is omitted.

[0040] Figure 1 Fig. 1 IA is a perspective view showing the appearance of the radiation detector 1A of one embodiment. The radiation detector 1A includes the scintillator array 5, the light detection element 7, and the signal readout device 10. The scintillator array 5 is arranged on one end surface (light incident surface) of the light detection element 7. The signal readout device 10 is arranged on the other end surface (signal output surface) of the light detection element 7. In other words, in the direction of incidence of radiation, the light detection element 7 is arranged between the scintillator array 5 and the signal readout device 10.

[0041] Figure 2is a perspective view showing the appearance of the scintillator array 5. The scintillator array 5 has L (L is an integer of 2 or more, and in the drawing, L = 16 is shown) scintillators 51. The L scintillators 51 each have a cuboid shape, and are arranged side by side in one dimension or two dimensions. In the illustrated example, the 16 scintillators 51 are arranged in two dimensions of 4 rows x 4 columns.

[0042] Each scintillator 51 generates a photon when radiation is incident thereon. A light-shielding wall is provided between scintillators 51 adjacent to each other, and at least a part of the photon generated in a scintillator 51 does not move to an adjacent other scintillator 51, but moves to a face opposite to the face on which the radiation is incident. In addition, as the material of the scintillator 51, a plastic or the like can be cited.

[0043] Figure 3 is a perspective view showing the appearance of the light detection element 7. The light detection element 7 is, for example, a multi-channel type light detection element such as an MPPC or a multi-anode PMT, and is mainly composed of a semiconductor material such as silicon, for example, in the case of an MPPC. The light detection element 7 has L light detection pixels 71 in a light incident face 7a. The L light detection pixels 71 are arranged side by side in one dimension or two dimensions in correspondence with the arrangement of the scintillators 51 in the scintillator array 5.

[0044] That is, each light detection pixel 71 corresponds to each scintillator 51 one-to-one, and opposes each scintillator 51. In the illustrated example, the 16 light detection pixels 71 are arranged in two dimensions of 4 rows x 4 columns. Further, the light detection element 7 further has L output terminals 72. Each output terminal 72 protrudes from a signal output face 7b opposite to the light incident face 7a, and is provided in correspondence with each light detection pixel 71 one-to-one.

[0045] The L light detection pixels 71 each generate a detection signal in correspondence with the incidence of a photon from the scintillator 51. Each light detection pixel 71 includes, for example, an avalanche photo diode (APD) that operates in a Geiger mode, and a quenching resistor connected in series to the APD. The quenching resistor is electrically connected to the output terminal 72. The detection signal generated in each light detection pixel 71 is output from the output terminal 72 to the outside of the light detection element 7.

[0046] Figure 4is a plan view showing the light-incident surface 7a of the light-detecting element 7. In the present embodiment, the L light-detecting pixels 71 are divided into M (an integer of 2 or more) light-detecting pixel groups 74 each of which includes N light-detecting pixels 71. In the illustrated example, the 16 light-detecting pixels 71 are equally divided into 4 light-detecting pixel groups 74. In this case, the number N of the light-detecting pixels 71 included in each light-detecting pixel group 74 is 4. Further, in the illustrated example, the case where N1 rows x N2 columns (N1, N2 are integers of 1 or more, and N1 x N2 = N) of the light-detecting pixels 71 adjacent to each other are divided into 1 light-detecting pixel group 74, and the number of rows N1 and the number of columns N2 are equal to each other (specifically, N1 = N2 = 2) is shown.

[0047] Further, the number M of the light-detecting pixel groups 74 is not limited to 4, and can be various numbers such as M = 2 or M = 6, for example. Also, the number N of the light-detecting pixels 71 included in the light-detecting pixel group 74 is not limited to 4, and can be various numbers such as N = 2 or N = 6, for example. The number of rows N1 and the number of columns N2 are also arbitrary.

[0048] Figure 5 is a perspective view showing the external appearance of the signal readout device 10. The signal readout device 10 has M signal readout circuits 11. The M signal readout circuits 11 are arranged in a one-dimensional or two-dimensional manner in parallel in correspondence with the arrangement of the light-detecting pixel groups 74 in the light-detecting element 7.

[0049] That is, each signal readout circuit 11 corresponds to each light-detecting pixel group 74 on a one-to-one basis. Each signal readout circuit 11 has N input terminals 12 connected to the N output terminals 72 of the corresponding light-detecting pixel group 74. In the illustrated example, the number M of the signal readout circuits 11 is 4, and the number N of the input terminals 12 is 4.

[0050] Figure 6 is a view schematically showing the internal structure of the signal readout circuit 11. The signal readout circuit 11 includes N light-incident detection sections 13 and one total value detection section 14. The N light-incident detection sections 13 are provided in correspondence with the N light-detecting pixels 71, respectively, and are electrically connected to the corresponding light-detecting pixels 71 through the output terminals 72 and the input terminals 12. That is, each light-incident detection section 13 is connected to the corresponding light-detecting pixel 71 through a wiring having a substantially zero resistance value.

[0051] Each light incident detection section 13 inputs a detection signal from the corresponding light detection pixel 71, and outputs a signal indicating the incidence of a photon incident on the light detection pixel 71. The signal indicating the incidence of a photon is, for example, a pulse signal having a rectangular time waveform. In one embodiment, the light incident detection section 13 includes a comparator. In a case where the detection signal from the light detection pixel 71 exceeds a prescribed threshold value, the comparator outputs a pulse signal of a preset magnitude.

[0052] In the above-described structure, the "pulse signal of a preset magnitude" is a signal on which different weighting has been performed by each light incident detection section 13, and has a different magnitude for each light incident detection section 13. In one example, the comparator of each light incident detection section 13 generates a pulse signal of a certain magnitude when the incidence of a photon is detected. Furthermore, the comparator of each light incident detection section 13 converts this pulse signal into a pulse signal of a different magnitude for each light incident detection section 13 in accordance with a weight determined for each light incident detection section 13.

[0053] The integrated value detection section 14 is electrically connected to the N light incident detection sections 13 via a signal transmission system having substantially zero impedance, and detects the integrated value of the output signals from the N light incident detection sections 13. In order to equalize the signal transmission time from each light incident detection section 13 to the integrated value detection section 14, the line length between the integrated value detection sections 14 is equalized for the N light incident detection sections 13. Furthermore, the signal transmission system from the N light incident detection sections 13 is coupled into one at the node Nd, and reaches the integrated value detection section 14.

[0054] In one embodiment, the output signals from the N light incident detection sections 13 are analog signals, and the integrated value detection section 14 includes an analog-digital conversion circuit. In this case, the integrated value detection section 14 converts the signal after superimposing the output signals from the N light incident detection sections 13 into a digital signal. That is, in a case where one light incident detection section 13 outputs a signal of VI (V) and another light incident detection section 13 outputs a signal of V2 (V), the integrated value detection section 14 converts a signal of VI + V2 (V) into a digital signal. The digital signal output from the integrated value detection section 14 is output to the outside of the radiation detector 1A.

[0055] The N light incident detection sections 13 are described in further detail. Figure 7 (a) of FIG. 8 is a view indicating one light detection pixel group 74. In this example, four light detection pixels 71 of 2 rows x 2 columns are indicated. For ease of explanation, these light detection pixels 71 are labeled with channel (CH) numbers of (1) to (4). Furthermore, each light incident detection section 13 outputs a signal on which different weighting has been performed in correspondence with each light detection pixel 71.

[0056] Figure 7 (b) of FIG. 8 indicates the signal output from each light incident detection section 13. In this example, the signal output from each light incident detection section 13 is a pulse signal of a different magnitude for each light incident detection section 13.Figure 7 (a) shows an example of the weight values ​​of the light incident detection unit 13 corresponding to the four light detection pixels 71. In this example, channel number (1) is assigned a weight of 1, channel number (2) is assigned a weight of 2, channel number (3) is assigned a weight of 4, and channel number (4) is assigned a weight of 8. In other words, the weight value of the light incident detection unit 13 with channel number n (n = 1, 2, ..., N) is 2. (n-1) .

[0057] The weight of each light incident detection unit 13 can be achieved, for example, by adjusting the voltage supplied to the comparator to a value corresponding to that weight through resistor division or the like. The minimum resolution required by the total value detection unit 14 is determined by the number N of light incident detection units 13 connected to the total value detection unit 14. For example, when N=4, the minimum resolution required by the total value detection unit 14 is 4 bits.

[0058] Figure 8 This is a graph showing the relationship between the sum of the output signals from the N light incident detection units 13 detected by the sum value detection unit 14 and the combination of channel numbers. For example, when the sum value is zero, it means that no photon is incident on any light detection pixel 71. When the sum value is 1, it means that a photon is incident only on the light detection pixel 71 of channel number (1). When the sum value is 2, it means that a photon is incident only on the light detection pixel 71 of channel number (2). When the sum value is 3, it means that photons are incident on both light detection pixels 71 of channels (1) and (2) simultaneously.

[0059] In this way, for each of the N light detection pixels 71 and all the combination modes of the light detection pixels 71, the total value is different from each other and the total value does not repeat.

[0060] Figure 9 This diagram conceptually illustrates an example of determining which photon of the photodetector element 71 a photon has entered. Figure 9 (a) represents four light detection pixel groups 74, each containing two rows and two columns (a total of four) of light detection pixels 71.

[0061] For example, such as Figure 9 As shown in (b), the four signal readout circuits 11 corresponding to the four light detection pixel groups 74 output a total value of 1, 1, 6, and 2 respectively. At this time, in the two light detection pixel groups 74 with a total value of 1, as shown in (b), Figure 9As shown in (c), it is determined that only the light detection pixel 71 of the channel number (1) has the photon (the light detection pixel 71 having the photon is indicated by a hatched line) shot thereto. In the light detection pixel group 74 having the total value of 6, it is determined that two light detection pixels 71 of the channel numbers (2) and (3) have the photons shot thereto at the same time. In the light detection pixel group 74 having the total value of 2, it is determined that only the light detection pixel 71 of the channel number (2) has the photon shot thereto.

[0062] In another example, as shown in (d), the four signal readout circuits 11 corresponding to the four light detection pixel groups 74, respectively, output the total values of 0, 14, 0, and 2, respectively. At this time, in the two light detection pixel groups 74 having the total value of 0, as shown in (e), it is determined that none of the light detection pixels 71 of any of the channel numbers (1) has the photon shot thereto. In the light detection pixel group 74 having the total value of 14, it is determined that three light detection pixels 71 of the channel numbers (2), (3), and (4) have the photons shot thereto at the same time. In the light detection pixel group 74 having the total value of 2, it is determined that only the light detection pixel 71 of the channel number (2) has the photon shot thereto. Figure 9 Figure 9

[0063] Figure 10 is a conceptual diagram showing an example of the operation of the signal readout circuit 11. For example, the photons are caused to be shot into two light detection pixels 71 of the channel numbers (1) and (3) at substantially the same time. At this time, the pulse signal Pl having a height (voltage value) of 1 is output from the light incidence detection section 13 corresponding to the channel number (1). In addition, the pulse signal P2 having a height (voltage value) of 4 is output from the light incidence detection section 13 corresponding to the channel number (3). Note that the heights of the pulse signals Pl, P2 are relative values.

[0064] These pulse signals Pl, P2 coincide with each other at the node Nd to become a pulse signal P3 having a peak height (maximum voltage value) of 5, which is input to the A / D conversion circuit as the total value detection section 14. The total value detection section 14 generates a digital signal corresponding to the peak height of the pulse signal P3, and outputs the digital signal to the outside of the signal readout device 10. In addition, as shown in (b), even if the generation timings of the pulse signals Pl, P2 are slightly deviated, the deviation can be tolerated as long as it is below the time width of the pulse signals Pl, P2. Figure 10

[0065] ​​​The time width of the pulse signal output from the light incidence detection section 13 affects the response speed of the radiation detector 1A. Therefore, it is preferable that the time width can be arbitrarily set according to the usage environment and required specifications. Further, if the time width of the pulse signal output from the light incidence detection section 13 is too short with respect to the processing period (processing speed) of the total value detection section 14, in the case where a plurality of pulse signals are separated in time, there is a risk that the signal input to the total value detection section 14 does not become the total value of them, thereby causing a false detection. Therefore, the time width of the pulse signal can be set according to the processing period of the total value detection section 14.

[0066] Figure 11 is a view conceptually showing another example of operation of the signal readout circuit 11. In this example, a photon also enters two light detection pixels 71 of channel numbers (1) and (3) at substantially the same time. At this time, a pulse signal P4 of which the pulse area (i.e., time integral value of pulse height, typically, pulse time width x pulse height) is 1 is output from the light incidence detection section 13 corresponding to the channel number (1). Further, a pulse signal P5 of which the pulse area is 4 is output from the light incidence detection section 13 corresponding to the channel number (3). In addition, the areas of the pulse signals P4, P5 are relative values.

[0067] These pulse signals P4, P5 are input to the A / D conversion circuit which is the total value detection section 14. The total value detection section 14 generates a digital signal corresponding to the total area of the pulse signals P4, P5, and outputs the digital signal to the outside of the signal readout device 10. In addition, the total value detection section 14 generates a digital signal corresponding to the total area of the pulse signals existing within a prescribed processing period, and in the case where two pulse signals are generated within different processing periods, respectively, the areas of these pulse signals are not totalized, but are A / D-converted at different timings, respectively. That is, as shown in Figure 11 even if the generation timings of the pulse signals P4, P5 are slightly deviated, the deviation is treated as a simultaneous incidence as long as it is below the processing period of the total value detection section 14.

[0068] Figure 12 is a timing chart showing the signal readout method of the present embodiment. The signal readout method is a method of reading out a signal from a light detection element 7 having a plurality of light detection pixels 71 which generate a detection signal in response to incidence of light, and can be implemented, for example, using the signal readout circuit 11 of the present embodiment.

[0069] First, in a first step S1, N signals indicating incidence of light are generated based on signals from N light detection pixels 71 included in a light detection pixel group 74, respectively. This first step S1 is performed, for example, at N light incidence detection sections 13. Next, in a second step S2, a total value of the N signals is detected. This second step S2 is performed, for example, at a total value detection section 14.

[0070] Moreover, in the first step S1, signals to which different weightings have been applied in correspondence with the respective light detection pixels 71 are generated, and the weights are set in such a manner that the aggregate values are different from each other for all combination patterns of the respective light detection pixels 71 and the light detection pixels 71 from each other in the light detection pixel group 74 (see Fig. 2). Figure 8 ).

[0071] The signal readout apparatus 10 and the signal readout circuit 11 of the present embodiment and the effects obtained by the signal readout method described above will be explained.

[0072] In the signal readout circuit 11 and the signal readout method of the present embodiment, when the signal indicating the incidence of light is generated in the light incidence detection section 13 (first step S1), the aggregate values of the N signals to which different weightings have been applied in correspondence with the respective light detection pixels 71 are detected in the aggregate value detection section 14 (second step S2). As shown in Fig. 2, the weights are set in such a manner that the aggregate values are different from each other for all combination patterns of the respective light detection pixels 71 and the light detection pixels 71 from each other. Figure 8

[0073] In such a configuration, it is possible to uniquely determine which light detection pixel 71 (one or a plurality of) the light has been shot into from the aggregate value. Therefore, according to the signal readout circuit 11 and the signal readout method, even in the case where light is simultaneously shot into a plurality of positions, it is possible to detect them in distinction. Moreover, compared with the case where N signal readout circuits corresponding to the N light detection pixels 71 are provided, it is possible to suppress the enlargement of the circuit scale.

[0074] In addition, in the radiation detector disclosed in Patent Literature 1, the output signals from the respective light detection pixels are also weighted. However, the method of determining the weight values is different from the present embodiment, and therefore in the case where light is simultaneously shot into a plurality of positions, it is not possible to detect them in distinction. The signal readout circuit 11 and the signal readout method of the present embodiment have a special effect that is not found in the technology described in Patent Literature 1, that is, it is possible to detect them in distinction even in the case where light is simultaneously shot into a plurality of positions.

[0075] Moreover, in the signal readout apparatus 10 of the present embodiment, the large number of light detection pixels 71 of the light detection element 7 are divided into M light detection pixel groups 74, and the signal readout circuit 11 is provided for each light detection pixel group 74. Thereby, compared with the case where a single signal readout circuit 11 is used, it is possible to reduce the number N of the light incidence detection sections 13. Therefore, it is possible to suppress the number of all combination patterns realized by the N light detection pixels 71 from being too large. Moreover, compared with the case where one signal readout circuit is provided for one light detection pixel 71, it is possible to make the circuit scale 1 / N. ​

[0076] As in the present embodiment, each light incidence detection section 13 can also include a comparator. In this case, it is possible to set a threshold value for the detection signal from the light detection pixel 71, and to determine with high precision whether or not light has been incident. Further, by making the signal output condition (voltage value, etc.) of the comparator different for each comparator, it is also possible to easily set the weight in such a manner that the total value is different for each combination of the light detection pixels 71 and the light detection pixels 71 from each other.

[0077] As in the present embodiment, the output signal from the N light incidence detection sections 13 can also be an analog signal, and the total value detection section 14 can include an A / D conversion circuit that converts the signal obtained by superimposing the output signals from the N light incidence detection sections 13 into a digital signal. By such a structure, for example, it is possible to appropriately detect the total value of the output signals from the N light incidence detection sections 13.

[0078] As in the present embodiment, the weight of the nth (n = 1, 2,..., N) light incidence detection section 13 can also be made 2 (n-1) By setting the weight in this way, for example, it is possible to make the total value different for each combination of the light detection pixels 71 and the light detection pixels 71 from each other. However, the weight value of the light incidence detection section 13 is not limited thereto, and various other weight values can also be used as long as the total value is different for each combination of the light detection pixels 71 and the light detection pixels 71 from each other.

[0079] (Modified Example)

[0080] Figure 13 is a plan view showing a modified example of the light incidence surface 7a of the light detection element 7. In the above-described embodiment, in Figure 4 which the case where N1 rows x N2 columns of light detection pixels 71 adjacent to each other are divided into one light detection pixel group 74 and the row number N1 and the column number N2 are equal to each other (specifically, N1 = N2 = 2) was shown, but the row number N1 and the column number N2 can also be different from each other as shown in Figure 13 In the example of Figure 13 , in the light incidence surface 7a in which 64 light detection pixels 71 are arranged in a two-dimensional shape of 8 rows x 8 columns, the row number N1 of each light detection pixel group 74 is made 8 and the column number N2 is made 1.

[0081] Further, for example, at least one light detection pixel 71 of the N light detection pixels 71 included in one light detection pixel group 74 can also be separated from the other light detection pixels 71 without being adjacent thereto. In this way, the division pattern of the light detection pixel group 74 is arbitrary, and the effects of the above-described embodiment can be appropriately obtained regardless of the division.

[0082] The signal readout circuit, signal readout device, and signal readout method of the light detecting element are not limited to the above-described embodiments and configurations, and various modifications can be made.

[0083] For example, in the above-described embodiments, the pulse height (voltage value) or pulse area of the signal output from the light incident detection section 13 is weighted, but various other characteristic values of the signal output from the light incident detection section 13 can be weighted.

[0084] Further, in the above-described embodiments, the light incident detection section 13 employs a comparator, and the weighted signal is output from the comparator, but the configuration of the light incident detection section 13 is not limited thereto, and for example, a signal of a certain size can be output from each comparator, and the output signals from the comparators can be weighted using various weighting circuits connected to the rear stage of the comparators. Alternatively, the light incident detection section 13 can be configured using a logic circuit and a decoder.

[0085] The signal readout circuit of the light detecting element of the above-described embodiment is a circuit that reads out a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in response to the incidence of light, and is characterized by including: N (N is an integer of 2 or more) light incident detection sections that input detection signals from N light detecting pixels included in the plurality of light detecting pixels and output signals indicating the incidence of light, each light incident detection section outputting a signal to which different weighting is applied corresponding to each light detecting pixel, the weight being set in such a manner that the sum total of the outputs of the N light incident detection sections differs for each combination of the N light detecting pixels.

[0086] The signal readout method of the light detecting element of the above-described embodiment is a method of reading out a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in response to the incidence of light, and is characterized by including: a first step of generating N signals indicating the incidence of light based on signals from N (N is an integer of 2 or more) light detecting pixels included in the plurality of light detecting pixels, and a second step of detecting the sum total of the N signals, in the first step, a signal to which different weighting is applied corresponding to each light detecting pixel is generated, the weight being set in such a manner that the sum total of the outputs of the N light incident detection sections differs for each combination of the N light detecting pixels.

[0087] In the signal readout circuit described above, a configuration in which a comparator is included for each light incident detection section can also be adopted. In this case, it is possible to set a threshold value for the detection signal from the light detection pixel and determine whether or not light has been incident with high precision. Further, by making the signal output condition (voltage value, etc.) of the comparator different for each comparator, it is also possible to easily set the weight in such a manner that the aggregate values are different for each combination of the light detection pixels and the light detection pixels from each other.

[0088] In the signal readout circuit described above, the output signals from the N light incident detection sections can also be analog signals, and the aggregate value detection section can include an analog-digital conversion circuit that converts a signal obtained by superimposing the output signals from the N light incident detection sections into a digital signal. With such a configuration, for example, it is possible to detect the aggregate value of the output signals from the N light incident detection sections.

[0089] In the signal readout circuit described above, the weight of the nth (n = 1, 2,..., N) light incident detection section can also be made 2 (n-1) With such a configuration, for example, it is possible to make the aggregate values different for each combination of the light detection pixels and the light detection pixels from each other.

[0090] The signal readout device of the light detection element of the embodiment described above is a device that reads out a signal from a light detection element having M (M is an integer of 2 or more) light detection pixel groups each including a plurality of light detection pixels that generate a detection signal in response to the incidence of light, and is characterized by including M signal readout circuits each of which is a signal readout circuit of a light detection element having the configuration described above and reads out a signal from each of the M light detection pixel groups.

[0091] Industrial applicability

[0092] The embodiment can be utilized as a signal readout circuit, a signal readout device, and a signal readout method of a light detection element that can distinguish and detect light incident at a plurality of positions at the same time while suppressing the increase in the circuit scale.

[0093] Explanation of reference numerals

[0094] 1A radiation detector

[0095] 5 scintillator array

[0096] 7 light detection element

[0097] 7a light incident surface

[0098] 7b signal output surface

[0099] 10 signal readout device

[0100] 11 signal readout circuit

[0101] 12 input terminal

[0102] 13 light incident detection section

[0103] 14 total value detection section

[0104] 51 scintillator

[0105] 71 light detection pixel

[0106] 72 output terminal

[0107] 74 light detection pixel group

[0108] 100 radiation detector

[0109] 101 scintillator group

[0110] 102 scintillator

[0111] 103 light detection element

[0112] 104 light detection pixel

[0113] 105 resistance chain

[0114] 106 resistance

[0115] Nd node

[0116] P1 to P5 pulse signals

Claims

1. A signal readout circuit of a light detecting element, which is a circuit that reads out a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, characterized by comprising: N light incidence detecting sections that respectively input the detection signal from N light detecting pixels included in the plurality of light detecting pixels and output a signal that indicates incidence of light, wherein N is an integer of 2 or more; and a total value detecting section that detects a total value of output signals from the N light incidence detecting sections.

2. The signal readout circuit of a light detecting element according to claim 1, characterized in that: each light incidence detecting section includes a comparator.

3. The signal readout circuit of a light detecting element according to claim 1 or 2, characterized in that: the output signal from the N light incidence detecting sections is an analog signal, and the total value detecting section includes an analog-digital conversion circuit that converts a signal obtained by superimposing the output signals from the N light incidence detecting sections into a digital signal.

4. The signal readout circuit of a light detecting element according to claim 1 or 2, characterized in that:

5. The signal readout circuit of a light detecting element according to claim 3, characterized in that: M is an integer of 2 or more, and the signal readout apparatus of a light detecting element is characterized by comprising: M signal readout circuits that are the signal readout circuit according to any one of claims 1 to 5, and the M signal readout circuits respectively read out signals from the M light detecting pixel groups, respectively.

7. A signal readout method of a light detecting element, which is a method that reads out a signal from a light detecting element having a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, characterized by comprising: a first step of generating N signals that indicate incidence of light, based on signals respectively from N light detecting pixels included in the plurality of light detecting pixels, wherein N is an integer of 2 or more; and a second step of detecting a total value of the N signals, in the first step, a signal to which different weightings are applied in correspondence with each light detecting pixel is generated, and the weightings are set in such a manner that the total values are different from each other for each light detecting pixel of the N light detecting pixels and all combination patterns of light detecting pixels with each other. ​ ​ The weight of the nth light incidence detection part is 2 （n-1） wherein n = 1, 2, …, N. ​ The weight of the nth light incidence detection part is 2 （n-1） wherein n = 1, 2, …, N.

6. A signal readout device of a light detecting element, which is a device that reads out a signal from a light detecting element having M groups of light detecting pixels each including a plurality of light detecting pixels that generate a detection signal in correspondence with incidence of light, wherein ​ ​ ​ ​ ​ ​ ​ ​

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