JPH0443926A - Laser irradiation detector - Google Patents

Abstract

PURPOSE:To set the sensitivity of the laser irradiation detector to the optimum reference value automatically according to the state of its periphery by sending a minimum value detected by a minimum value detecting circuit to a comparator as a threshold value signal. CONSTITUTION:The output of an amplifier 4 is supplied to a comparator 6 and an integration circuit 12. The integration circuit 12 integrates the signal from the amplifier 4 to average it with time, and sends its output to a minimum voltage detecting circuit 13. The minimum voltage detecting circuit 13 outputs the lowest voltage among four inputs to the comparator 6 as the threshold value signal. The minimum value detecting circuit 13 compares the minimum output as the threshold value signal with the input signal and sends out a minimum output voltage.

Description

[Detailed description of the invention] a. Industrial application field The present invention relates to a laser irradiation detector.

b. Prior Art FIG. 3 is a block diagram of a pre-signal processing section of a laser irradiation detector according to the prior art.

Received signals from four optical sensors Ia arranged in four directions are converted into voltages by a current/voltage conversion circuit 2a, low frequency noise of the sensors is removed by a coupling capacitor 3a, and the signals are applied to an amplifier 4a. The signal amplified by the amplifier 4a has low frequency noise removed by the coupling capacitor 5a, and is sent to one input terminal of the comparator 6a. In the threshold value setting circuit 7a, the threshold value is fixed at a level that reduces false alarms due to noise, and the threshold value is applied to the other input terminal of the comparator 6a.

When the received signal exceeds the threshold, the signal output of the comparator 6a is given to the data latch 8a and the OR gate 9a
given to. The output of OR gate 9a becomes a latch timing signal for data latch 8a.

The data latch 8a latches the signal from the comparator 6a according to the latch timing signal output from the OR gate 9a, and sends the output signal as parallel data to the parallel/serial conversion circuit 10a. The parallel/serial conversion circuit 10a converts parallel data into serial data using the clock signal supplied from the clock generation circuit 11a, and outputs the serial signal to the subsequent signal processing circuit.

Since the subsequent signal processing circuit is outside the scope of the present invention, a description thereof will be omitted.

C0 Problems to be Solved by the Invention In conventional laser irradiation detectors, the threshold value is constant even though the amount of noise varies depending on the surrounding environment. As a result, when there is a lot of noise, there are many false alarms, and when there is little noise, that is, when the threshold becomes relatively high relative to the noise due to changes in the environment, signals between the threshold and the noise level are detected. The problem is that it is impossible.

The present invention can be applied when the surrounding situation changes, for example, the amount of light in the background.
It is an object of the present invention to propose a laser irradiation detector that has a threshold value setting circuit that can automatically set an optimal threshold value according to the amount of noise of the optical sensor or amplifier.

60 Means for Solving the Problem The above problem is to use a plurality of optical sensors and a signal from each sensor in a laser irradiation detector that detects the laser light irradiated to the self or the laser light irradiated by the self and reflected. It is equipped with a minimum voltage detection circuit that integrates and sets the smallest signal among the integrated values as a threshold, and a level comparison circuit that compares the threshold with the received signal and determines that a signal is present when the latter is larger than the former. Characteristic laser irradiation detector.

More specifically, it includes a plurality of optical sensors, a current/voltage conversion circuit that converts the output current of each optical sensor into a voltage signal, a threshold setting circuit, and a signal corresponding to the output of each current/voltage conversion circuit. and a data latch circuit that latches the output of each comparison circuit. In the laser irradiation detector that performs signal processing based on the data obtained, the threshold value setting circuit integrates the signal corresponding to the output of the current/voltage conversion circuit, and the minimum value among the outputs of each integration circuit. The problem has been solved by a laser irradiation detector that includes a minimum value detection circuit for determining the minimum value, and sends the minimum value detected by the minimum value detection circuit to the comparison circuit as a threshold signal.

The amount of noise from the sensor located in the direction where the 80 action laser light does not arrive, depending on the surrounding situation, is used as the threshold value of the comparator. Therefore, when the amount of ambient light is relatively low,
Its sensitivity can be fully demonstrated, there are fewer malfunctions due to noise even when background light increases, and the sensitivity of the laser irradiation detector is automatically set to the optimal reference value according to the surrounding situation.

f. Embodiment FIG. 1 is a block diagram of an embodiment of a laser irradiation detector according to the present invention.

This laser irradiation detector is part of a device that measures not only the arrival direction of the laser beam but also the frequency of the laser beam by adding an optical filter in front of the optical sensor, as well as the pulse width and pulse repetition frequency of the laser beam. used as.

In the figure, optical sensor 1, current/voltage conversion circuit IB2, amplifier 4
, comparator 6, data latch 8, OR gate 9, parallel/serial conversion circuit 10. The clock generation circuit 11 includes the optical sensor 1a, current/voltage conversion circuit 2a, amplifier 4a, comparator 6a, data latch 8a, OR gate 9a, parallel/serial conversion circuit 10a, and clock generation circuit 11a, which are explained in FIG. corresponds to and has the same effect. Therefore, corresponding parts will be given corresponding reference numbers and their description will be omitted.

The output from amplifier 4 is provided to comparator 6 and integration circuit 12. The integrating circuit 12 integrates the signal from the amplifier 4, averages it over time, and outputs it to the minimum voltage detection circuit 13. The minimum voltage detection circuit 13 outputs the smallest voltage among the four inputs to the comparator 6 as a threshold signal.

FIG. 2 shows a circuit example of the integration circuit 12 and the minimum voltage detection circuit 13.

The integrating circuit 12 consists of an operational amplifier, a capacitor, and a diode, and the diode of the integrating circuit with the minimum output voltage is turned on.
The operational amplifier of the minimum voltage detection circuit 13 outputs its minimum output voltage.

g8 Advantages of the Invention It is possible to trade off the detection probability and false alarm probability according to the surrounding environmental conditions such as the amount of background light, and adopt a threshold value as an optimal comparison reference value.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a laser irradiation detector according to the present invention, Fig. 2 is a specific circuit diagram of the integrating circuit and minimum voltage detection circuit of Fig. 1, and Fig. 3 is a block diagram of a laser irradiation detector according to the prior art. This is a diagram. 1... Optical sensor, 2... Current/voltage conversion circuit, 4... Amplifier, 6... Comparator,
8...Data latch, 9...OR gate, 1
0...Parallel/serial conversion circuit, 11...Clock generation circuit, 12...Integrator circuit, 13...Minimum voltage detection circuit.

Claims (1)

[Claims] 1) A laser irradiation detector that detects a laser beam irradiated to itself or a laser beam irradiated by itself and reflected, integrates a plurality of optical sensors and the signals of each sensor, and integrates the signals of each sensor. A laser characterized by comprising a minimum voltage detection circuit that sets the smallest signal among the values as a threshold, and a level comparison circuit that compares the threshold with a received signal and determines that a signal is present when the latter is larger than the former. Irradiation detector. 2) a plurality of optical sensors, a current/voltage conversion circuit that converts the output current of each optical sensor into a voltage signal, and a threshold setting circuit;
A signal corresponding to the output of each current/voltage conversion circuit is sent to one input terminal of each, and a threshold signal is sent from the threshold setting circuit to the other input terminal of each comparison circuit, and the output of each comparison circuit is latched. Equipped with a data latch circuit to
In a laser irradiation detector that performs signal processing based on data latched by a data latch circuit, the threshold setting circuit includes an integrating circuit that integrates the signal corresponding to the output of the current/voltage conversion circuit, and an integrating circuit that integrates the signal corresponding to the output of the current/voltage conversion circuit. A laser irradiation detector comprising a minimum value detection circuit for determining the minimum value among outputs, and sending the minimum value detected by the minimum value detection circuit to the comparison circuit as a threshold signal.