JP2001337119A - Pulse edge detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse edge detection circuit capable of surely and easily detecting superposed pulse signals. SOLUTION: The pulse edge detection circuit comprises a delay line 1 for delaying an input pulse signal, a limiter 3 for limiting the delayed input pulse signal, and a comparator 4 for comparing the limited delayed input pulse signal with the original input pulse signal and outputting an edge detection signal. Thus, by outputting rectangular-wave signals which are synchronized with the rise and fall of the pulse signal, detection of the superposed pulses is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pulse edge detection circuit capable of detecting a superimposed pulse.

[0002]

2. Description of the Related Art Generally, in radiation measurement for sample analysis in a sample analyzer such as an electron probe microanalyzer (EPMA) or a fluorescent X-ray analyzer, the generation of radiation from a sample by primary beam irradiation is detected by a semiconductor detector. And converts it into an electric signal using a charge-sensitive amplifier. The charge-sensitive amplifier outputs a staircase wave signal having a wave height proportional to the energy of the incident radiation, and the staircase wave signal is shaped into a single pulse having a peak proportional to the wave height of the staircase wave by a pulse processor. ing.

[0003] Radiation measurement pulse processors are roughly classified into two types, slow amplifiers and fast amplifiers.
It has two waveform shaping circuits, the slow amplifier is for generating a pulse with a good S / N ratio used for the purpose of measuring the energy of radiation, and it is necessary to use a relatively large time constant. It is getting longer. On the other hand, the first amplifier generates a pulse used to monitor the pile-up (superposition of pulses) by detecting the generation of radiation and a timing pulse for controlling a slow amplifier. The time constant is reduced so that the process time can be shortened as much as possible so that detection can be performed reliably even if the error occurs in close proximity.
The present invention relates to a method for detecting a pulse output from a first amplifier of the pulse processor.

Next, an example of a pulse output from the first amplifier will be described with reference to FIGS.
Here, description will be made assuming that the first amplifier outputs a triangular wave pulse. FIG. 6 shows a general discrimination circuit for detecting this pulse. This discrimination circuit monitors the level of the input pulse signal Vin based on a threshold value, and includes a comparator 101 and a voltage source V _R for setting the threshold value. (A) of FIG. 5 is (B) of FIG.
The pulse generation positions for explaining the pulse signals output from the first amplifier shown in FIG. In FIG. 5A, when radiation causing the pulse of FIG. 5D is generated after the pulse of FIG. 5A is generated, the output of the first amplifier becomes independent as shown in FIG. 5B. Pulses (a) and (d) are obtained. When this pulse output is input as the input signal Vin of the discrimination circuit shown in FIG. 6, an output indicated by Vout is obtained.
It is possible to recognize the generation of a pulse due to the two radiations (a) and (d).

[0005]

However, when pulse detection is performed using the discrimination circuit having the above-described configuration, the pulse shown in FIG.
When the radiation is generated close to each other so that the pulses of the first and second pulses are partially overlapped, the output of the first amplifier becomes (C) of FIG.
As shown in (1), the pulses (a) and (b) are superimposed. When this pulse signal Vin is input to the discrimination circuit shown in FIG. 6, an output as shown by Vout is obtained. In other words, in this case, it can be recognized that only one pulse is generated despite the generation of two radiation pulses (a) and (b). FIG.
When the radiation causing the pulse (c) is generated after the pulse (a) is generated, the output of the first amplifier is the same as the pulse (a) and (c) as shown in (D) of FIG. Is partially superimposed. Therefore, when this pulse signal Vin is input to the discrimination circuit shown in FIG. 6, an output indicated by Vout is obtained. In this case, similarly, even when pulses due to two radiations (a) and (c) are generated. Regardless, 1
That is, only pulses can be recognized. As described above, the pulse detection method using the discrimination circuit shown in FIG. 6 has a problem that when pulses are superimposed, an overlap of a plurality of pulses cannot be detected, and the pulse is erroneously recognized as a single pulse. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem in the conventional pulse detection system using a discriminating circuit, and has a pulse edge detection circuit capable of reliably and easily detecting each superimposed pulse signal. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a delay circuit for delaying an input pulse signal, a limiter for reducing a delay input pulse signal, and a limiter for reducing a delay input pulse signal. A pulse edge detection circuit is constituted by a comparator that compares the delayed input pulse signal with the original input pulse signal and outputs an edge detection signal.

With this configuration, as long as a plurality of peaks are present in the superimposed pulse signal, the rising and falling of each superimposed pulse can be detected.
By applying this to the output of the first amplifier in radiation measurement, it is possible to reliably detect pile-up without overlooking radiation generated in close proximity.

[0009]

Next, an embodiment will be described. FIG. 1 is a circuit configuration diagram showing an embodiment of a pulse edge detection circuit according to the present invention. In FIG. 1, 1 is a delay line for delaying an input pulse signal, 2 is a buffer amplifier for buffering, and 3 is a cut-off of an input pulse signal composed of a diode and a voltage source _VL , that is, for removing a low level portion. And 4 are comparators for comparing the delayed pulse signal with the original input pulse signal. In addition,
R on the circuit is a resistor for impedance matching with the delay line 1.

Next, the operation of the pulse edge detection circuit thus configured will be described with reference to the timing chart shown in FIG. Here, it is assumed that a pulse signal corresponding to the superimposed pulse signal shown in FIG. 5C is input. The input pulse signal is delayed for a predetermined time by the delay line 1. The delayed input pulse signal passes through the buffer amplifier 2 and is subjected to an appropriate truncation process by the limiter 3. The signal is input to the inverting input terminal of the comparator 4. The original input pulse signal is input to the non-inverting input terminal of the comparator 4. As a result, a rectangular wave signal synchronized with the rise and fall of the input pulse signal is output from the output terminal of the comparator 4.

When a pulse signal corresponding to the superimposed pulse signal shown in FIG. 5D is input to the pulse edge detection circuit having such a configuration, as shown in FIG. Is delayed by the delay line 1 for a predetermined time, then cut off by the limiter 3, and the cut-off delayed input pulse signal is input to the inverting input terminal of the comparator 4. Then, the delayed input superimposed pulse signal input to the inverting input terminal is compared with the original input superimposed pulse signal input to the non-inverting input terminal of the comparator 4, and the polarity is inverted at the point where the signal and the signal cross. 2
A rectangular wave signal synchronized with the rise and fall of the two superposed pulse signals is output. When a pulse signal corresponding to the non-overlapping pulse signal shown in FIG. 5B is input, naturally, a rectangle synchronized with the rising and falling edges of the two pulse signals similarly as shown in FIG. A wave signal is output.

Even when a pulse signal in which two pulses are superimposed is input as described above, as shown in FIGS. 2 and 3, the output signals of the comparator all generate two rectangular wave signals. Thus, as shown in FIGS. 5C and 5D, it is possible to detect a superimposed pulse that could not be detected by the conventional discriminating circuit.

Further, since the rising or falling edge of the output signal of the comparator in the pulse edge detection circuit according to the present invention is synchronized with the start of the edge of the input signal, the rising or falling edge of the output signal may be, for example, It can be used as a trigger signal for peak hold or valley hold.

In the above embodiment, the case where two pulses are superimposed has been described. However, the present invention is applicable to the case where three or more pulses are superimposed even when the corresponding pulse peaks. Is present, it is possible to detect each superimposed pulse. Also,
The present invention is not limited to pulse detection in radiation measurement,
It can be applied to detection of general input pulse signals.

[0015]

As described above, according to the present invention, according to the present invention, even when a superimposed pulse signal on which a pulse is superimposed is input, a plurality of peaks are provided as long as the plurality of peaks exist. Rising and falling edges can be detected. This makes it possible to detect pulse overlap, so if it is applied to the output of the first amplifier of a pulse processor for radiation measurement, it is possible to reliably detect pileup without overlooking radiation generated in close proximity. . In addition, the output of the first amplifier is also used for counting radiation generation per unit time, so that a counting error can be reduced. Further, since the rise or fall of the pulse can be detected, it can be used as a trigger signal for a peak hold or valley hold circuit.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a pulse edge detection circuit according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a timing chart for explaining another operation mode.

FIG. 4 is a timing chart for explaining still another operation mode.

FIG. 5 is a timing chart for explaining a conventional pulse detection mode.

FIG. 6 is a circuit configuration diagram showing a conventional discrimination circuit used for pulse detection.

[Explanation of symbols]

 1 delay line 2 buffer amplifier 3 limiter 4 comparator

Claims (1)

[Claims] 1. A delay circuit for delaying an input pulse signal, a limiter for cutting off the delayed input pulse signal, and edge detection by comparing the cut-off delayed input pulse signal with the original input pulse signal. A pulse edge detection circuit comprising a comparator for outputting a signal.