JPH0448288A - Laser warning device - Google Patents

Abstract

PURPOSE:To prevent wrong warning by performing timing retrieval for the rising and falling of a converted logic pulse and generating no warning signal when reflected light whose logic pulse is not within a prescribed time range is made incident. CONSTITUTION:A rise counter 14 counts the time from a projection laser timing signal 4 to a detecting signal 5 and outputs rise timing data 6 and a fall counter 15, on the other hand, measures the time from the projection laser timing signal 4 to a fall detection signal 7 and outputs fall timing data 8. The rise counter 13 and fall counter 15 inputs a clock 3 for those measurement and are reset with a reset pulse 2. A counting range setting circuit 16 outputs a counting range setting signal 9 for limiting the counting time ranges of the rise counter 14 and fall counter 15 and eliminates the generation of a wrong warning due to the incidence of reflected light not within the prescribed time range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser warning device, and more particularly to a laser warning device that defines the time range of incidence of reflected light and eliminates the generation of false warning signals.

[Conventional technology]

Detection of logic pulses using reflected light in conventional laser alarm devices involves creating a range gate signal that opens at the same time the laser is emitted and closes at the same time as a specified time elapses, and converts the range gate signal and one reflected light into a logic pulse. Pulse detection was performed by performing logical product, and an alarm signal was generated based on the detected signal.

[Problem to be solved by the invention]

The logic pulse detection of the conventional laser alarm device described above detects a detection signal if the period of the logic value "'1" of the logic pulse obtained by converting one reflected light overlaps even slightly with the time range of the range gate signal. This circuit outputs an alarm signal, so even if reflected light from the laser emitted by the laser alarm device itself or other external light is detected outside the range of the range gate signal, the converted logic If part or all of the pulses are within the range of the range gate signal, a detection signal is generated, which has the drawback of outputting a false alarm signal.

The above-mentioned drawbacks are detailed as follows.

FIG. 3 is an explanatory diagram of occurrence of a false alarm in a conventional laser alarm device. FIG. 3(a) is a timing chart illustrating logical pulse detection in a conventional laser alarm device. The emitted laser shown in Fig. 3(a) returns from the alarm target as reflected light corresponding to the distance, thereby forming a logic pulse with a logic value of "1P". A detection signal is output and an alarm is issued when the specified time t is included, and this detection signal is obtained in the form of ANDing the range gate signal and the detection signal.

FIG. 3(b) is a timing chart showing a state where one reflected light exists outside the specified time of the range gate signal and a false alarm is issued. In this case, a part of one reflected light is included within the specified time of the range gate signal, and the pulse width is narrower than in the case of Fig. 3(a) only during the time when the logical product of the logic pulse and the range gate signal is obtained. Outputs a detection signal and issues a false alarm.

FIG. 3(c) is a timing chart for explaining the content of outputting a detection signal in a state where external light has partially entered within the specified time of the range gate signal. The external light is generally longer in time than the emitted laser, and therefore, as shown in Fig. 3 (c
), it is often output as a long pulse detection signal and a false alarm signal is output.

In both cases of FIGS. 3(b) and 3(c) described above, the detection signal will generate an undesirable false alarm.

[Means to solve the problem]

The device of the present invention is a laser alarm device that emits a pulsed laser, detects its reflected light, converts this reflected light into a logical pulse, detects the presence or absence of an alarm target, and generates an alarm signal. The timing search for the rise and fall of the converted logic pulse is performed, and if the logic pulse is caused by the incidence of reflected light outside a prescribed time range, generation of an alarm signal is excluded.

Furthermore, the apparatus of the present invention has a configuration in which the prescribed time range is set with the laser emission timing as the time starting point.

〔Example〕

Next, nine aspects of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The embodiment shown in FIG. 1 includes a rise detector 12 that receives a logical pulse formed by reflected light from an emitting laser and detects its rising edge, a falling detector 13 that detects its falling edge, and an emitting laser pulse. A rising counter 14 that measures the time from the timing to the above-mentioned rise, a falling counter 15 that measures the time until falling, and a count range setting circuit 16 that sets the count time range of the rising counter 14 and the falling counter 15. and a determination circuit 17 that determines whether or not the input logic pulse is in the correct specified time period and outputs a detection signal only if it is in the correct specified time period.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

The rising edge detector 12 receives the logic pulse 1, detects the rising edge thereof, and supplies a rising edge detection signal 5 indicating the rising edge to the rising edge counter 14.

The falling detector 13 detects the falling of the logic pulse 1,
A falling detection signal 7 indicating a falling edge is supplied to a falling counter 15.

The rising counter 14 measures the time from the emitted laser timing signal 4 to the rising detection signal 5.

Rise timing data 6 indicating the rise timing is output. Similarly, the falling counter 15 measures the time from the emitted laser timing signal 4 to the falling detection signal 7, and outputs 1 falling timing data 8. The rising counter 14 and the falling counter 15 receive a clock 3 for this measurement and are reset by a reset pulse 2.

The count range setting circuit 16 outputs a count range setting signal 9 for limiting the count time range of the rising counter 14 and the falling counter 15, and controls the time range of rising and falling counts.

FIG. 2 is a timing chart for explaining the operation of the first embodiment. This timing chart shows a sequence in which the time from the rise of the emitted laser timing signal 4 to the rise and fall of the logic pulse 1 is counted by the taro clock 3.

The emission laser timing signal 4 shown in FIG. 2(a) rises simultaneously with laser emission and is supplied to the count range setting circuit 16 as a signal with a predetermined pulse width. Logic pulse 1 in FIG. 2(b) is formed based on reflected light.

The rising pressure detection signal 5 in FIG. 2(d) detects the rising edge of the logic pulse 1 in FIG. 2(b), and the falling detection signal 7 in FIG. 2(g) detects the falling edge of the logic pulse 1 in FIG. 2(g). Detected and formed.

FIG. 2 (rise timing data 6 of e>).

In this embodiment, a 5-bit counter counts the clock 3 in FIG. 2(c) until the rising pressure detection signal 5 in FIG. 2(d) rises from the timing of the emission laser timing signal 4. For example, when the count number is 10, it is indicated as 01010 and is output from the rise counter 14.

The rise timing data 8 in FIG. 2(g) is as follows.

The falling detection signal 7 in FIG. 2(f) is the result of counting up from the timing of the emitted laser timing signal 4 to the rising edge using a 5-bit counter in the same way as the rising timing data 6. For example, when the count number is 17, is 10
001 and is output from the fall counter 15.

Note that clock 3 indicates the rising edge of the clock.

The count range setting signal 9 in FIG. 2(h) is
) and (c), the time range in which the logic pulse 1 should exist is set, and this is set in advance based on the characteristics and operational specifications of the laser alarm device, and the count range setting circuit 16 is output from.

FIG. 2 (i> maximum count value data 10).

Data counted up by a 5-bit counter within a time range defined by the count range setting signal 9 is supplied from the count range setting circuit 16 to the determination circuit 17.

The detection signal 11 in FIG. 2(j) is determined by comparing and determining the rising timing data 6 and the falling timing data 8 with the count maximum value data 10.
<The falling timing data 8 is output from the determination circuit 17 only when the condition that all count values are 0 or more and less than the maximum count value data 10 is satisfied.

After that, the rising timing data 6 and the falling timing data 8 are generated by the reset pulse 2 shown in FIG. 2(k).
and count maximum value data 10 are both reset to zero and enter a standby state.

〔Effect of the invention〕

As explained above, the present invention has the effect of preventing the generation of false alarm signals due to the incidence of extraneous light by eliminating the generation of false alarm signals due to the incidence of reflected light outside the specified time range. be.

[Brief explanation of the drawing]

FIG. 1 is a bronch diagram of one embodiment of the present invention, and FIG. 2 is a diagram of the first embodiment.
FIG. 3(a) is a timing chart for explaining the operation of the embodiment shown in the figure. FIG. 3(a) is a timing chart for detecting logical pulses of a conventional laser alarm device. FIG. FIG. 3(C) is a timing chart illustrating a state in which a false alarm is issued due to external light partially entering within a specified time. 1...Logic pulse, 2...Reset pulse, 3...
Clock, 4... Emission laser timing signal, 5...
・Rise detection signal, 6...Rise timing data 7
...Falling detection signal, 8...Fall timing data, 9...Count range setting signal, 10...Count maximum value data, 11...Detection signal, 12...Rise detector, 13... ... Falling detector, 14... Rising counter, 15... Falling counter, 16... Count range setting circuit, 17... Judgment circuit, 18... Search circuit.

Claims (1)

[Claims] 1. Emitting a pulsed laser and detecting the reflected light,
In a laser alarm device that detects the presence or absence of an alarm target and generates an alarm signal by converting this reflected light into a logic pulse, a timing search for the rise and fall of the converted logic pulse is performed, and the logic pulse is 1. A laser alarm device comprising means for eliminating generation of an alarm signal in the case of incidence of reflected light outside a prescribed time range. 2. The laser alarm device according to claim 1, wherein the predetermined time range is set using a laser emission timing as a time starting point.