JPS58147670A - Object detector - Google Patents

Abstract

PURPOSE:To eliminate resetting of a set value for a change in an output of a radiation source and a change in sensitivity of a detector, by a method wherein a delay circuit is located to a radiation detector, and a difference signal between a direct signal of a detector and a delay signal is compared with a set value. CONSTITUTION:When an object 13 to be measured moves and is located above a ray source receptacle 10, radiation from a radiation source 11 is shielded, an output of a radiation detector 12, inputted to an amplifier 14, is divided into two parts, the one is connected to an inversion side of a differential amplifier 16 through a resistance 15, and the other to a non-inversion side of the amplifier 16 through a delay circuit 17. The output of the amplifier 16 is compared by a comparing part 24 provided with comparators 22 and 23 having positive and negative values +PC0 and -PC, and the output terminals of the comparators 22 and 23 are connected to an S-terminal and an R-terminal, respectively, of an FF circuit 25. As noted above, setting of a set value for a difference signal prevents the absolute output of the detector 12 and the set value from having a direct relation therebetween, and permits the elimination of the influence on a detecting sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an object detection device that detects the presence or absence of an object by reducing the intensity of the radiation edge. The object detection device is configured to detect the absence of the object to be measured from the attenuation of radiation transmitted through the object, and Figures M1 and 2 show the block configuration diagram and signal time chart of the device. Illustrated. That is, this equipment emits a radiation edge from the radiation source 2 housed in the source container 1, and the radiation detector 3 converts it into an electrical signal based on its intensity. ing. This electrical signal is input via the amplifier 4 to one input of the comparator 5 and compared with the set value from the setting 66 input to the other. Here, the object to be measured 7 is transferred to the radiation irradiation area by the S object distribution device (not shown) as shown in FIG. 2(a).
After passing for the time t shown in Fig. 2(b), the output S0 of the radiation set detector 3 becomes
The output gradually decreases to below the set value PSo9, and after the object to be measured 7 passes through the radiation 1111 irradiation area, the output gradually returns to the original value. Therefore, during the time t when the output S0 of the detector 3 is below the set value PS0, the comparator 5 detects the
) is configured to output an output C0 indicating the presence of an object to be measured.

[Study points for background technology]

By the way, in the conventional device described above, each time the output of the linear radiation source 2 or the sensitivity of the radiation detector 3 of the set value Ps0 changes,
There is an inconvenience that the set value ps0 must be changed. Therefore, it is necessary to manage the performance of the radiation source 2 and radiation detector 3! However, this is not desirable in terms of work efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an object detection device that stably detects the presence or absence of an object to be measured without resetting set values in response to changes in the output of radiation@m or the sensitivity of a radiation detector.

[Summary of the invention]

In order to achieve the above-mentioned objectives, the present invention provides a delay circuit that provides a time delay to the electrical signal according to the radiation dose output from the radiation detector, and provides a time delay between the signal of the radiation detection sIO Naohata and the delay circuit. Calculate the difference signal from the signal obtained by t4, compare this difference signal with the positive and negative set values in the comparison section, and based on the signal output when the difference signal exceeds the positive and negative set values, respectively. The object detection device detects an object to be measured and has a configuration in which the signal of the radiation detector and the set value have no direct relationship.

[Embodiments of the invention]

FIG. 3 is a block configuration diagram showing an embodiment of the device of the present invention. That is, in this device, a radiation source 11 and a radiation detector 12 housed in a radiation source container 10 are arranged facing each other with a sufficient distance between them. For example, the object to be measured 13 is moved in the direction of the arrow shown in the figure. This radiation detector 1
2 converts the incident radiation into an electric signal according to its line intensity and supplies it to the subsequent amplifier 14. This amplifier 14
The output terminal is branched into two branches, one of which is connected to the negative input terminal of a differential amplifier 16 via a resistor 15, and the other to the positive input terminal of a differential amplifier ti16 via a delay circuit 17. Therefore, the differential amplifier 16 outputs a signal corresponding to the difference between the signal input via the resistor IJ and the input signal delayed by the delay circuit 1r. A filter circuit consisting of a resistor 19 and a capacitor 20 in parallel is used.

21a is a feedback resistor of the differential amplifier 16.

Then, the output of the differential amplifier 16 is the positive set value +p
c, and a negative setpoint -K.

A comparison section 24 having a comparator 23 with

The output terminals of the comparators 22 and 23 are free, differential 0. G time lol
! It is connected to the S terminal and the S terminal of No. 25, respectively. This flip-flora f circuit 25 generates an output at the Q terminal with input from the 8 terminals, and is reset by the S terminal input to return the output of the Q terminal to its original off state.

Next, we will explain the operation of the device configured as described above.
This will be explained using the No. 41 time chart.

When the constant Il 13 passes through the radiation irradiation region at time T shown in FIG. 4(&), an output as shown by real ImA in FIG. 4(b) is generated from the amplifier 14 to the negative input terminal of the differential amplifier 1#. A degraded signal is input. At the same time, a resistor 18, a resistor 19, and a capacitor 2 are connected to the positive input terminal of the differential amplifier 16.
The time constant of the delay circuit 110 is greater than 0 as shown in Fig. 4(b).
As shown in point IIB, a signal having a slow characteristic with a time delay is input to the negative input terminal. Therefore, (1) Depending on the input Si of these differential amplifiers 16, a signal C0 corresponding to the difference between the signals at both input terminals is outputted from the differential amplifier 16. This is shown in Figure 4 (,). This signal is
The settings shown in FIG.
0 and -PC0, and when it exceeds +PC0 and falls below -PC0, comparators 22 and 23 of the comparator 24 output signals, respectively. Among these outputs, the signal output from the comparator 22 is input to the S terminal of the free, f, and g circuit z5, and the signal output from the comparator 23 is input to the S terminal of the f, f, and p circuit 25. is input. However, the output F of this frig hoop circuit 25. A signal having an arm pulse 411i1Tt- as shown in FIG. 4(d), which rises to 9 when the signal is input to the 4S terminal and falls when the signal to the S terminal is input, is output to the output terminal Q.

However, assuming that the object to be measured 13 is not present in the radiation irradiation area, the output of the amplifier 14 is constant. Therefore, the signal level at both input ends of the differential amplifier 16 is
Even if one signal is delayed by the time constant of the delay circuit zrtv, it will still be the same signal, and the output of the differential amplifier 16 will be zero. Therefore, there will be no change in the output ' of the comparison s24.
Huh, 'f flow, f circuit 25 also does not transmit the signal.

However, the pulse signal of the above-mentioned nine-flip-frog circuit 2j can be used as a detection signal for the object to be measured 110 in the radiation irradiation area, and the pulse intensity ↑ can be taken as the radiation-to-irradiation area passage time of the object to be measured. Yes In this way, the change in the output of the amplifier 14 caused by the object under test 13 is transferred to the delay circuit 11.
By dividing the signal into two signals with a level difference according to the time constant of , and treating the difference as the difference between the two signals, and setting a set value for this difference, the absolute output of the radiation detector 12 and the set value can be adjusted as before. ◇Therefore, the influence of the output intensity of the radiation source 11 and the detection sensitivity of the radiation detector 12 can be removed.
If the outputs of 2 and 24 are output as they are, they can be used as a signal for entering the radiation region of the object to be measured (output of comparator 22) and a signal for exiting from the same region (output of comparator 23).

Furthermore, the present invention is not limited to the above embodiments; for example, if the time constant of the radiation detector 12 is small, a capacitor may be added in parallel to the feedback resistor 2 of the differential amplifier 16. Various modifications may be made without departing from the gist of the present invention.

[! i@light effect]

According to the present invention, there is no need to reset the setting value that serves as the detection standard due to changes in the output of the radiation source or the detection sensitivity of the radiation detector. It is possible to detect the presence or absence of

9. Since the change in radiation intensity caused by a constant object is regarded as the level difference between two signals created with a time difference, there is no malfunction due to external noise compared to when the change in line intensity is determined by differentiation. 0 that can provide an object detection device that can stably detect the presence/absence of an object to be measured.

[Brief explanation of drawings]

The first WIA is a block diagram of a conventional device, and the second figure is a Jl
Ill 111c) Signal time chart of the device of Ill Wei, No. 5rjA is a block diagram of an embodiment of the object detection device according to the present invention, and FIG. 4 is a signal time chart of the device having the configuration shown in FIG. ts3. 11... Radiation source, 12... Radiation detector, 13.
...Measurement object, 16...Differential amplifier, 17...Delay circuit, 24...Hieibe, 25...Free lag flop circuit・Dehojin's agent Patentari Tosuzu Oshiki Hiko Figure 1 Figure 2 1'/ Figure 4

Claims (1)

[Claims] A radiation source and its radiation liI+! A radiation detector that receives the radiation and outputs an electrical signal according to the dose, a delay circuit that provides a time delay to the signal of this radiation detector, and a difference between the output signal of this delay circuit and the output signal of the radiation detector. It includes a differential amplifier that outputs a signal, and a comparison section that compares the difference signal of this differential amplifier with predetermined positive and negative set values and outputs a signal when each set value is exceeded. An object detection device characterized by detecting an object to be measured that enters a radiation irradiation area of a piece-wise radiation edge source based on a signal from a soft part.