JPH0339570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser light warning device that can detect laser light and know the direction of incidence of the laser light.

Conventionally, this type of laser beam cover alarm device has a configuration in which a plurality of photodetecting elements 5, 6, 7, etc. are arranged in an array at the focal point of a condensing lens 2, as shown in FIG. A photodetecting element array 3 is arranged, and current/voltage conversion circuits 8, 9, 10, etc. are provided to convert the photocurrent output from the individual photodetecting elements 5, 6, 7 into voltage, and this voltage output is converted into a laser beam. It is equipped with discriminating circuits 11, 12, 13, etc., which are composed of level comparators, etc., for discriminating whether or not the laser beam is present. Ru. The operation is such that the incident laser beam 1 with a certain incident angle θ is
According to the intensity of the laser beam 1, the light is focused on a focusing point 4 on the photodetecting element array 3, and is supplied from the photodetecting element 6 at the focusing point 4 to a photocurrent-voltage conversion circuit 9 according to the intensity of the laser beam 1, which outputs a voltage. Therefore, the discrimination circuit 12
It is determined whether it is a laser beam or not, and if it is a laser beam, a voltage output is sent to the display 15, and the display 15 indicates that the laser beam 1 has entered and also displays the incident angle θ.

In the laser beam warning device configured as described above, when a laser beam with excessive incident intensity is incident, the condensing lens 2 emits high intensity light to the condensing point 4 on the photodetecting element array 3. Because the laser beam is focused and the incident intensity is excessive, crosstalk (leakage) occurs in the photodetecting elements 5 and 7 adjacent to the photodetecting element 6 at the condensing point 4, as if the photodetecting elements 5 and 7 In the same way as if a laser beam was incident on the sensor, the current-voltage conversion elements 8 and 10 send the voltage output to the discrimination circuits 11 and 13, and the displays 14 and 16 display that the laser beam has entered the sensor. However, there was a drawback in that it was not possible to accurately determine the incident angle θ at which the laser beam actually entered.

Furthermore, the laser beam with excessive incident intensity is focused by the condenser lens 2 onto a condensing point 4 on the photodetecting element array 3, and the focused light is reflected on the surface of the photodetecting element. , this reflected light is further reflected in the direction of the photodetector array 3 by the condenser lens 2,
The light enters the photodetecting element on the photodetecting element array 3 again, and in response to this incident, the photocurrent output is sent to the current-voltage conversion element, where it is converted to voltage output, which is discriminated by the discrimination circuit as laser light, and displayed. The device displays the incident direction of the laser beam as well as the incident direction, making it impossible to accurately determine the actual incident angle θ.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser beam warning device that can solve the above-mentioned drawbacks and accurately display the incident direction of laser beams ranging from minute incident intensity to excessive incident intensity.

The present invention involves arranging a plurality of photodetecting elements in an array, combining these with a condensing lens, and focusing the laser beam on one of the photodetecting elements arranged on the array according to the incident angle of the laser beam. emitting light, dividing the photocurrent output from the photodetecting element into two outputs according to a distribution ratio unique to each photodetecting element, and determining the distribution ratio of the photocurrent output from the two outputs. Therefore, the configuration is such that the incident angle of the laser beam is determined regardless of the incident and received intensity of the laser beam.

Embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing one implementation of the present invention.

The laser beam alarm device of the present invention includes a condensing lens 2, a photodetecting element array 3, an impedance element 17,
18, 19, 20, 21, etc., current-voltage conversion circuits 22 and 23, discrimination circuits 24 and 25, addition circuit 26, subtraction circuits 27 and 30, and logarithmic amplifier circuit 2
8 and 29 and a display circuit 31.

The photodetecting element array 3 is a plurality of photodetecting elements 5, 6, 7, etc. arranged in an array.
Impedance elements 17, 18, 19, 20, 2
The first element is composed of a single resistor or a resistor, inductance, and capacitance, has the same impedance, and combines the outputs of each photodetector element 5, 6, 7, etc., to a distribution ratio unique to each photodetector element. Therefore, the photocurrent output is divided and the current-voltage conversion circuit 22
and 23. The determination circuit includes a level comparator and the like, and determines whether the voltage outputs of the current-voltage conversion circuits 22 and 23 are laser beams. Addition circuit 26 and subtraction circuit 2
7 is the discrimination circuit 24 and 2 for ultra-short pulse light.
Calculate the sum signal output and difference signal output from the output of 5,
The respective outputs are supplied to multiple amplifier circuits 28 and 29. The subtraction circuit 30 is a logarithmic amplifier circuit 28
From the outputs of 29 and 29, the difference signal output is divided by the sum signal output to obtain a voltage output corresponding to the photodetector element into which the laser beam is incident. The display circuit 31 has a peak hold circuit, and uses the voltage output of the subtraction circuit 30 to display the incidence and direction of incidence of the laser beam.

Assuming that a laser beam is incident on the condenser lens 2 at an incident angle θ, the condenser lens 2 condenses the laser beam 1 onto a condensing point 4 on the photodetector array 3 . The photodetecting element 6 at this condensing point 4 is
It outputs a photocurrent according to the intensity of the incident laser light. Here, if the number of photodetecting elements is M and the impedance of the impedance element is Z, then
The impedance element is composed of (M+1) pieces,
If the laser beam is incident on the Nth photodetector element 6, the impedance elements 17, 18, 19, 2
0, 21, etc., the photocurrent output of the th photodetector element is divided into _I22 to the current-voltage conversion circuit 22 and I23 to the current-voltage conversion circuit ₂₃ .

I ₂₂ = I・NZ/(M+1)Z=IN/(M+1) I ₂₃₌ I(M+1-N)Z/(M+1)Z =I(M+1-N)/(M+1) These current-voltage conversion circuit 22 and The current to 23 becomes a voltage output depending on the current-voltage conversion rate α.
Assuming that the voltage outputs of the current-voltage conversion circuits 22 and 23 are V ₂₂ and V ₂₃ , respectively, V ₂₂ = αIN/M+1, V ₂₃ = αIM+1-N/M+
It becomes 1. This voltage output passes through discrimination circuits 24 and 25, respectively, and is supplied to an addition circuit 26 and a subtraction circuit 27. These adder circuits 26 voltage output
V _ADD and the voltage output of the voltage circuit 27 of the subtraction circuit 27 as V _SUB , V _ADD = V ₂₃ + V ₂₂ = αIM+1-N/M+1 + αIN/M+1 = αI _SUB = V ₂₃ -V ₂₂ = αIM+1-N/M+1 -αIN/M+1=αI(1-2N/M+1). By passing these voltage outputs V _ADD and V _SUB through the logarithmic amplifier circuits 28 and 29 and further through the subtraction circuit 30, the subtraction circuit output becomes V _SUB /V _ADD . Therefore, the voltage output V ₃₀ of the subtraction circuit 30 is V ₃₀ = V _SUB /V _ADD = αI (1-2N/M+1)/αI = 1-2
It becomes N/M+1. Here, M is the total number of photodetecting elements 5, 6, 7, etc. in the photodetecting element array 3, and N is the current-voltage conversion circuit 2 of the photodetecting element on which the laser beam is incident.
This is the number counted from the 2nd side and varies from 1 to M.

From the voltage output V ₃₀ of this subtraction circuit 30, an output corresponding to the incident angle of the laser beam can be obtained regardless of the incident intensity of the laser beam, and this output is sent to the display circuit 30.
1 indicates that the laser beam is incident and also indicates the angle of incidence.

According to this method, a laser beam having an excessively high incident intensity is used to collect the laser beam on the photodetecting element 6.
The influence of crosstalk (leakage) on the adjacent photodetecting elements 5 and 7 is less than a few percent of the current output of the photodetecting element 6, and the current output is almost equally distributed between the adjacent photodetecting elements 5 and 7. In addition, the calculation error of the incident angle due to the current output of the photodetector element 5 and the calculation error of the incidence angle due to the current output of the photodetector element 7 work to cancel each other out, and the incident angle of the laser beam can be accurately determined without the influence of crosstalk. You can know. Also, regarding the light that is reflected on the surface of the photodetector element 6 and is further directed toward the photodetector array 3 side by the condenser lens 2 and enters again, the intensity is less than a few percent of the intensity that is incident on the photodetector element 6. Since the laser beam is almost uniformly incident on the photodetecting element array 3, the calculation error of the incident angle of the laser beam is very small, and compared to conventional laser beam warning devices, the incident direction of the laser beam can be determined more accurately. You can know.

As explained above, the present invention combines a plurality of photodetecting elements arranged in an array with a condensing lens, and selects one photodetecting element in the photodetecting element array according to the incident angle of the laser beam. The laser beam is focused on the photodetector, the photocurrent output from the photodetector is divided into two outputs according to the distribution ratio unique to each photodetector, and the distribution ratio is determined from these two outputs. This has the effect that the incident angle of the laser beam can be obtained regardless of the intensity of the laser beam.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the structure of a conventional laser beam warning device, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1... Laser light, 2... Condensing lens, 3... Photodetecting element array, 4... Focusing point, 5, 6, 7...
Photodetection element, 8, 9, 10... Current-voltage conversion circuit, 11, 12, 13... Discrimination circuit, 14, 1
5, 16... Indicator, 17, 18, 19, 20,
21... Impedance element, 22, 23... Current voltage conversion circuit, 24, 25... Discrimination circuit, 26
... Addition circuit, 27 ... Subtraction circuit, 28, 29 ...
... Logarithmic amplifier circuit, 30 ... Subtraction circuit, 31 ... Display circuit.

Claims (1)

[Claims] 1. A condensing lens, a plurality of photodetecting elements arranged in an array, a photodetecting element array disposed at the focal position of the condensing lens and receiving light from the condensing lens, and this photodetecting element array. means for dividing the photocurrent output from each photodetector in the transducer array into two currents according to a distribution ratio specific to each photodetector; and means for determining the distribution ratio of the divided photocurrent output. , and display means for displaying the direction of arrival of the laser light from the determined ratio.