JPS63300986A - Detector for light or radiation incidence position - Google Patents

Abstract

PURPOSE:To speed up the detection of a radiation incidence position by arranging detectors in two dimensions and comparing the outputs of detectors mutually when they exceed a threshold value. CONSTITUTION:Signals from wire anodes 0-15 are passed through amplifies 100-115 and compared with the threshold value by comparators 300-315, and signals which are larger than the threshold value are latched by a latch circuit 40. Further, comparators 321-335 compare the outputs of adjacent detectors with each other and the circuit 40 latches them. Then exclusive ORs 501-514 compare the outputs of adjacent detectors with each other to detect a position where the comparison output changes from 0 to 1. In this case, only wires having peak change points correspond to 1 and the threshold value comparison outputs are ANDed by AND circuits 600-615 to select one of 16 wires. Then an effective output larger than the threshold value is converted by an encoder 70 into an address signal, which is outputted by a latch circuit 80 as a 4-bit X address. In a Y direction, a Y address signal is obtained similarly and the radiation incidence position is found from both address signals.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a detector using a multi-wire readout circuit;
In a position detector having multiple outputs, such as a detector having multiple detectors such as a scintillation camera, the detector having the maximum output signal is identified by mutually comparing the outputs of each detector, The present invention relates to a light or radiation incident position detection device that can detect the incident position at high speed.

[Conventional technology]

Conventionally, four 2D-multiwire position detection methods have been mainly used: a gravity center position calculation method, a delay line method, a coincidence encoding method, and a dual comparator method.

The center of gravity position calculation method is as shown in Figure 12.
The incident position is determined by connecting the wires in each direction with a resistor, adding the output signals obtained from both ends, and dividing the signal obtained from one end by this added value.

In the delay line method, the delay is weighted for each wire in advance, and the position is determined by identifying which wire position the signal was input to based on the difference in arrival time of the output signal of the wire. , the X direction, and the X direction, and the incident position is determined as the intersection of the identified wires.

In the coincidence encoding method, wires are connected as shown in Figure 13, and when a signal is input, there is a coincidence between the output lines of the connected wires (although only the X direction is shown in the figure, direction) is determined as the incident position.

As shown in FIG. 14, the dual comparator method is a method previously proposed by the applicant, in which two thresholds V are set for the spread distribution of electrons to each wire.
+, Vz are set, and when each exceeds this level, the two signal bit patterns obtained by setting the output to 1 are converted into incident position address information using the conversion table in ROM15 and 16, and then Y A highly accurate X address signal is obtained by correcting distortion based on directional position information. The same applies to the Y direction.

[Problems to be solved by the invention]

However, although the center-of-gravity position calculation method can provide a high degree of position resolution, it requires position calculation, which poses a problem in terms of response speed. Furthermore, even if digital calculations are performed using an A/D converter, it is necessary to use a high-speed A/D converter, which poses an economical problem.

Since the delay line method uses a delay to discriminate the position, in principle it is not possible to increase the response speed.

The coincidence encoding method is advantageous for position detection using many wires, but if the electron spread inside the PMT is large, the coincidence of many wires may be lost depending on the signal discrimination level setting. There is.

In the dual comparator method, the response speed is limited by the ROM.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a light or radiation incident position detection device that can detect the incident position at high speed, has a simple circuit configuration, and is excellent in economical efficiency. do.

[Means for solving problems]

For this purpose, the light or radiation incident position detection device of the present invention has the following features:
A plurality of two-dimensionally arranged detectors, a first comparator group that mutually compares the outputs of each detector, and a second comparator to which a detection signal from each detector and a threshold level signal are input. group, and the incident position is determined from the output of the first comparator group when the detector output is equal to or higher than a threshold level.

[Effect]

The present invention detects the detector having the peak of the output signal by mutually comparing the outputs of adjacent detectors arranged in a two-dimensional array, and thereby detects the light or radiation incident position with an inexpensive configuration and at an ultra-high speed. It can be detected by

〔Example〕

Hereinafter, an embodiment using a 2D-multiwire PMT will be described with reference to the drawings.

Fig. 1 is a diagram showing the detection principle of the light or radiation incident position detection device according to the present invention, and Fig. 2 is a diagram showing the relationship between the incident position and the comparator output, where A is the electron distribution spread distribution curve;
#1 to #9 are wire anodes, and 21 to 28 are comparators.

In the figure, light incident on a PMT (not shown) is photoelectrically converted and amplified at that position, and enters the wire with an electron spread as shown by curve A, for example. When comparing the reference inputs of the comparators of adjacent wires in one direction as shown in Figure 2, the comparator outputs are located before and after wire 5 where the electron spread peak of the input signal is located as shown in the figure. You can see that it changes. The position of the wire 5 where the comparator output has changed in this way becomes the signal input position. Note that since all wires are compared at the same time, the comparator outputs of wires far from the signal input vary, but this can be nullified by the threshold (2). In other words, the incident position can be detected by finding the change point of the effective comparator output.

Figure 3 shows 2D-multi wire P of 16x16 wires.
FIG. 4 is a diagram showing the circuit configuration of an embodiment of the light or radiation incident position detection device according to the present invention when using MT, and FIG. 4 is a diagram for explaining the logic of signal detection in the case of FIG. 3. In the figure, #0 to #15 are wire anodes, 100 to 1
15 is an amplifier, 300 to 315 are comparators for comparison with threshold signals, 321 to 335 are comparators for comparison of outputs of adjacent detectors, 40 is a latch circuit, 501 to 515 are exclusive OR circuits, 600
615 is an AND circuit, 70 is an encoder, and 80 is a launch circuit.

In the figure, the signals obtained from wire anodes #1 to #15 are amplified by amplifiers 100 to 115, and then outputted by comparators 300 to 315 only when the signal is at a predetermined level or higher, and latched by a launch circuit 40. Also,
The comparators 321 to 335 compare the output signals of adjacent detectors in one direction as shown in the figure, and the outputs are similarly latched.

Now, assuming that there is human power as shown in Fig. 4, the comparators 321 to 335 will output as shown in the figure.
Exclusively connect these adjacent outputs to 0R501~
514, and a location where the exclusive OR output is "1", that is, a location where the comparator output is rOJ-rlJ, is detected. In this case, only the wire at the peak change point becomes "1", and if this is ANDed with the threshold comparison output, one of the 16 wires can be selected. If the output is valid, exceeding the threshold level, the encoder 70 converts it into an address signal, and the launch circuit 80 outputs it as a 4-bit X address signal.

Note that although the above explanation shows a detection circuit only for the X direction, the same applies to the X direction, and this embodiment is effective when the electronic method has only one peak when comparing wires. It is.

No. 50 is a diagram showing various electronic law distribution waveforms.

Figure 5 (A) shows the case where the output at the left end of the wire is the largest, and in the mutual comparison shown in Figure 3, all comparator outputs are "1", and in the case of Figure 5 (B), When the output at the right end of the wire is the largest, all comparator outputs are "0". In this way, if the end of the wire is the largest, there will be no peak change points as mentioned above, but all of them are rlJ, or all of them are
0'', the left end or right end is detected as the incident position. In this case, in the case of FIG. 5(b), "0" may be inverted and used as "1".

Figure 5 (c) shows the case where there is a fluctuation in the electron beam,
FIG. 5(d) shows the case of a true double event, both of which will be excluded by the encoder 70.

Next, the detection method in the case of FIG. 5(c) will be explained with reference to FIGS. 6 and 7.

FIG. 6 is a principle diagram showing a detection method when there is fluctuation in the electronic method.

As a fluctuation condition, when comparing every other wire, curves B and C in the figure are obtained, but if there is one peak each, it is difficult to detect one of these peaks. The incident position can be detected by Incidentally, fluctuations greater than this can also be detected by comparing every two or more wires.

Fig. 7 is a diagram showing an embodiment of the present invention when every other wire is compared, and Fig. 8 is a diagram showing the logic in the case of Fig. 7. The same reference numerals as in Fig. 3 indicate the same content. ing. In addition, 341 to 354 are comparators, 401 to 4
15 is an inverter, and 421 to 434 are AND circuits.

The difference from the circuit configuration in the case of FIG. 3 is that comparators 341 to 354 are also included in every other wire to absorb most of the fluctuations of the electronic method. That is, Fig. 8 (
In the case of the electronic method as shown in b), the comparators 321 to 325 that compare the outputs of adjacent wires are (0, 0, 1, 0, 1, 1, 1, 1) as shown in the figure. The outputs of every other comparator 341 to 354, that is, every even number and every odd number, are (0°0.
1.1), (0, O, 0, 1, 1).

Therefore, the outputs of adjacent comparators are connected to the inverter 4.
01 to 414, and by ANDing the inverted output with the output of the adjacent comparator, the outputs of the AND circuits 421 to 434 become as shown in FIG. 8(b). Also, the rj-rlJ of every other comparator output
The position that changes to
By using the D circuits 602 to 613, it is possible to detect the wire that becomes the output rlJ.

In this way, if we were to use exclusive OR as in the circuit configuration shown in Figure 3, the comparator would compare many changing points, so only the changing point from 0 to 1 would become 1 when we AND the inverter. For every other peak, the peak is 1.
Exclusive OR is used to select only one peak. Then, threshold processing and encoding are performed in the same manner as in the case of FIG. 3, and incident position address information can be obtained.

FIGS. 9 and 10 are diagrams showing specific application examples of the zero-incidence position detection device for light or radiation according to the present invention.

FIG. 9 is a diagram showing a configuration of a combination of a mosaic scintillator and a 2D-multiwire PMT, and FIG. 10 is a diagram showing a 1:1 correspondence between the mosaic scintillator and the wire.

In the figure, the mosaic scintillator array is placed on the intersection of each xy wire in a 1:1 correspondence. 2
There is some fluctuation in the electron spread to the wires inside the D-multiwire PMT, but when comparing the wires, it can be assumed that there is only one peak in the wires near the signal. The incident position can be detected by the circuit configuration shown in FIG. if,
If the signal fluctuation of the electron spread is large and this assumption cannot be guaranteed, this fluctuation can be almost absorbed by inserting a comparator between every other wire in addition to the comparators between adjacent wires as described above. Fluctuations larger than this can be absorbed by further increasing the number of comparators between the wires, but in practice, by inserting every other comparator, it can be removed as a double event without any problem.

FIG. 11 shows the position obtained by applying the circuit configuration of the present invention in FIG. 3 to a detector (T-ray detector) in which a 4n-pitch BGO scintillator array is coupled to a position-detecting PMT with an anode wire pitch of 4 fl. This is a diagram showing an example of a discrimination result, and shows the relationship between the γ-ray incident position and positional accuracy. (However, only 8 wires in the X direction are used.) In the figure, the BG○ scintillators are arranged in 4 pitches, but as you can see from the figure, the detection by each scintillator is very well separated. I understand that.

[Effects of the Invention] As described above, according to the present invention, position detection having multiple outputs such as a detector using a multi-wire readout circuit, a detector having multiple detectors such as a scintillation camera, etc. In the detector, each wire (detector) is connected with a simple configuration consisting of a comparator and simple gate logic.
After integrating the input signal, the position can be detected at extremely high speed (within 100 nsec). Note that the spatial resolution depends on the pitch and number of wires (detectors).

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the detection principle of the light or radiation incident position detection device according to the present invention, Fig. 2 is a diagram showing the relationship between the incident position and the comparator output, and Fig. 3 is a 2D diagram of 16 x 16 wire.
- A diagram showing the circuit configuration of an embodiment of the present invention when using a multi-wire PMT, FIG. 4 is a diagram for explaining the logic of signal detection in the case of FIG. 1, and FIG. A diagram showing a spread distribution waveform, FIG. 6 is a principle diagram showing a detection method when there is fluctuation in electron spread, and FIG. 7 is a circuit configuration of another embodiment of the present invention when comparing every other wire. FIG. 8 is a diagram showing the logic in the case of FIG. 7, FIGS. 9 and 10 are diagrams showing specific application examples of the light or radiation incident position detection device according to the present invention, and FIG. 11 is a diagram showing the logic in the case of FIG. A diagram showing an example of position discrimination results obtained by applying the circuit of the present invention to a detector in which a 4N-pinch BGO scintillator array is combined with a position detection type PMT. Figure 12 shows a conventional incident position detection using the center of gravity position calculation method. FIG. 13 is a diagram showing a conventional incident position detecting device using a coincidence encoding method, and the fourteenth leap is a diagram showing a conventional incident position detecting device using a dual comparator method. A... Electron distribution spread distribution curve, #1 to #9...
Wire anode, 21-28... comparator, #
1~#15...Wire anode, 100~115.
... Amplifier, 300-315... Comparator for comparison with threshold signal, 321-335... Comparator for comparison between adjacent ones, 40... Latch circuit,
501-515... Exclusive OR circuit, 60
0 to 615...AND circuit, 70...encoder,
80...Latch circuit. Mr. Ise Hamamatsu Photonics Co., Ltd.
Agent Patent Attorney Akira Hiru Kawa Akira Nobuo Figure 1 Figure 2 Figure 4 Figure 5, Figure 5 (B) Figure 5 (Ha9 ψψψψψIψψψψψlψψψp Figure 11 Figure 12 Figure 13 Figure 14

Claims (3)

[Claims] (1) A plurality of detectors arranged in a two-dimensional array, a first comparator group that mutually compares the outputs of each detector, and a first comparator group that receives the detection signal from each detector and a threshold level signal. 1. A light or radiation incident position detection device comprising: two comparator groups, the incident position being determined from the output of the first comparator group when the detector output is equal to or higher than a threshold level. (2) The first comparator group is a group of comparators that compare the outputs of adjacent detectors.
The light or radiation incident position detection device described in 2. (3) A patent claim in which the first comparator group includes a third comparator group that compares the outputs of adjacent detectors, and a fourth comparator group that compares the outputs of every other or more detectors. The light or radiation incident position detection device according to item 1.