JPH0540469Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

This invention relates to a radiation detection circuit used in scintillation cameras and the like, and particularly to a circuit that generates a timing signal synchronized with a random event signal.

[Conventional technology]

Radiation detection devices such as scintillation cameras require analog signal processing such as integrating event signals and sample-holding, and these operations are performed in synchronization with event signals. You need to create a signal. In general, digital circuits that generate timing signals are often configured to generate timing signals by frequency-dividing a basic clock from the viewpoint of stability against temperature changes and no need for maintenance. However, in radiation detection circuits, the timing of incidence of radiation is random, and the timing signal requires high precision (on the order of several tens of nanoseconds). 100MHz clock
This would cause negative effects such as noise (the clock frequency cannot be increased because analog and digital signals are mixed), so in the end, we were unable to use this method and decided to use a one-shot circuit. It is constituted as a subject.

[Problem that the invention attempts to solve]

As mentioned above, in the past, timing signals were created by combining one-shot circuits, which led to problems such as poor stability against temperature changes and poor maintainability. The purpose of this invention is to provide a radiation detection circuit that can obtain highly accurate timing signals synchronized with random event signals while using a low-frequency basic clock, and has excellent temperature characteristics and maintainability.

[Means to solve the problem]

The radiation detection circuit according to this invention includes means for generating a low frequency clock signal, delay means for delaying the event signal by a time corresponding to the time from the event signal to the clock signal, and the delayed event signal as described above. and signal processing means for processing in synchronization with a clock signal.

[Operation] Since the event signal is delayed by the time equivalent to the time from the event signal to the clock signal, even though the event signal is random, The clock signals become synchronized. Therefore, if this delayed event signal is processed in synchronization with the clock signal, signal processing can be performed in synchronization with the event signal even if the clock signal has a low frequency. As a result, since the system basically uses a clock signal, it has the advantage that the timing signal is stable against temperature changes and there is no need for maintenance.

【Example】

In FIG. 1, an event signal generated in response to incident radiation from a detection section of a scintillation camera, etc. is input to a delay line 6, and
It is also input to the event pulse generation circuit 7. The event signal input to the delay line 6 is delayed by a predetermined time from each of the taps 11 to 15,
One of the signals is taken out through one of the normally open analog switches 21 to 25 that is closed, and is sent to the signal processing circuit 10. On the other hand, an event signal with a short pulse width is generated from the event pulse generation circuit 7 in response to the event signal, and this is sent to the delay line 8.
Delayed event pulses are obtained from taps 31-35 of delay line 8, respectively, and are sent to flip-flops 41-45, respectively. The basic clock generation circuit 9 generates a low frequency basic clock signal regardless of the timing of the above event signal, and sends this to the signal processing circuit 10 as a timing signal and to each of the flip-flops 41 to 45. There is. The delay lines 6 and 8 have delay characteristics that match each other, and the total processing time is about 500 nsec. Taps 11 and 31 output a signal with a delay time of 0, and taps 12 and 32 and taps 13 and 33 output a signal with a delay time of 0.
Outputs delayed signals at equal time intervals from taps such as . The width of the event pulse is slightly shorter than this delay time interval. Therefore, the delayed event pulses sent to each flip-flop 41 to 44 do not overlap with each other, and a gate signal is generated from the flip-flop to which the delayed event pulse that coincides with the clock signal is input, and only the analog switch to which the gate signal is sent is activated. When turned on, any delayed event signal is sent to the signal processing circuit 10 via the analog switch. Next, one example of operation will be described with reference to the time chart of FIG. 2 showing the waveforms of each signal. First, when an event signal as shown in FIG. 2 is input, the taps 31 to 3 of the delay line 8 are
Delayed event pulses are generated sequentially from 5 onwards, but since the width of the event pulses is set slightly shorter than the delay time interval, as shown in Figure 2, when a signal is generated from one tap and it ends, the next one is generated. The signals are generated from the taps so that they do not overlap with each other. The clock signal is generated at a low frequency independently of these event signals and event pulses, and here, for example, the clock signal is generated at a low frequency.
As shown in the figure, if the delay event pulse starts from tap 33 during the period in which it is occurring, then
The flip-flop 43 reads this rising edge and outputs the gate signal 5 from the flip-flop 43.
3 (Figure 2). Then, only the analog switch 23 to which this gate signal 53 is sent is turned on, and the other analog switches 21, 22,
24 and 25 remain off, only the event signal generated at tap 13 of delay line 6 is output to signal processing circuit 10. Since the event signal inputted to the signal processing circuit 10 is delayed by the same amount of time as the delay time of the tap 33 of the delay line 8, it is almost synchronized with the clock signal. Therefore, this clock signal is input as a timing signal, and in the signal processing circuit 10, which performs signal processing such as delay and sample hold in synchronization with this timing signal, signal processing is performed from the moment the event signal is input. become. In addition to the delay lines 6 and 8, other delay means such as a C-R delay element may also be used.
In addition to the configuration in which an event pulse is generated from an event signal, delayed, and the timing of a clock signal is measured to turn on one analog switch, the rise of the signal output from each tap of the delay line 6 is used. It is also possible to arrange to turn on one analog switch by measuring the timing of the clock signal.

[Effect of the idea]

According to the radiation detection circuit of this invention, since the timing signal is generated from the clock signal,
The timing signal has high precision, is stable against temperature changes, and has good maintainability. Moreover, since the frequency of the clock signal can be lowered, there are no adverse effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of this invention, and FIG. 2 is a time chart showing waveforms. 6, 8...Delay line, 7...Event pulse generation circuit, 9...Basic clock generation circuit, 1
0...Signal processing circuit, 21-25...Analog switch, 41-45...Flip-flop.

Claims (1)

[Scope of utility model registration request] means for generating a low frequency clock signal;
A radiation detection circuit comprising a delay means for delaying an event signal by a time corresponding to the time from the event signal to the clock signal, and a signal processing means for processing the delayed event signal in synchronization with the clock signal.