JPH05100026A - Range finder by laser - Google Patents

Abstract

PURPOSE:To secure the precision in measuring distance by a laser device, independent from variation of the photo-reception level. CONSTITUTION:A laser oscillator 1, signal transmitting/receiving optical system 2, photo-receiver circuit 3, counter circuit 4, and display circuit 9 constitute a laser circuit for measuring distance of conventional structure. The counter circuit 4 starts counting with the photo-sending timing of the laser oscillator 1 as a start signal. A comparator circuit group 5 comprises a plurality of comparator circuits having different operating levels (comparing level), and therewith the level of photo-reception signal till near the peak can be known. A delay circuit group 6 makes such an output delay that the comparison output nearer the peak is given earlier. A judging circuit 7 judges the outputs given in a specified sequence from the delay circuits belonging to the group 6 and emits an output as a stop signal for the counter circuit 4, which is also passed to a calculator circuit 8. In response to the output from the judging circuit 7, this calculator circuit 8 makes a correction for the delay caused by the delay circuit group 6 and the time delay due to the output sequence, determines the photo-receiving timing near the peak value of the photo-reception signal level, and determines the correct time of propagation, i.e., correct propagation distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser range finder,
In particular, the present invention relates to a laser distance measuring device for measuring the distance to a target based on the timing of projecting laser light to the target based on the time between light receiving timings.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring a distance using laser light, a modulated continuous light is applied to a mirror or the like placed at a target point, and the phase of the returning light is detected to measure the distance. There is a method of calculating and a method of receiving a part of light scattered by applying pulsed light to a target and calculating the distance from the propagation time of the light.

The former can be expected to have high accuracy, but a mirror or the like must be installed on the target, and it is not possible to easily measure the target several km away.

On the other hand, in the latter, since it is not necessary to install a mirror or the like at the target, it is possible to easily measure the distance, but it is difficult to shorten the duration of the generated pulse, and so on. Is difficult to improve.

In order to improve the accuracy, the clock frequency of the counter circuit for measuring the time difference between the light sending timing and the light receiving timing is increased to improve the resolution.
It is necessary to control the input of the counter circuit to a constant level for the level fluctuation of the received light signal due to the difference in the target reflectivity, etc. There are problems such as influence and circuit complexity, and it is not always easy to improve accuracy.

[0006]

In the conventional laser distance measuring apparatus described above, in addition to increasing the clock frequency to increase the resolution, the pulse duration is shortened to improve the accuracy and the level of the received light signal is increased. Although measures such as taking constant measures are used, shortening the pulse duration and keeping the level of the received light signal constant in order to apply it to a laser range finder that is portable and aims to be small and lightweight. There was a problem that the measures were not suitable.

The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a laser distance measuring device capable of highly accurate distance measurement without making the received light signal level constant even if the received light signal level fluctuates.

[0008]

The device of the present invention is a laser range finder for measuring the distance to a target by measuring the time difference between the timing of transmitting the laser light and the timing of receiving the reflected light from the target. , A plurality of comparison circuits for performing level comparison of the received laser light at operation levels as different comparison values and sending an output corresponding to the operation level, and for each of the outputs of the plurality of comparison circuits, A plurality of delay circuits that give a time delay so that the output order is determined in correspondence with the order of magnitude of the operation levels, and one output according to the output order based on a judgment standard preset for the outputs of the plurality of delay circuits A determination circuit for measuring the apparent propagation time to the target as an apparent received laser light, and a plurality of delay circuits for the apparent propagation time. The delay time based on the output order when the output is selected by the judgment circuit is corrected, the true light reception timing near the peak value of the received laser light is determined, the true propagation time is calculated, and the distance to the target is determined. And an arithmetic circuit for measuring

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In the embodiment shown in FIG. 1, a laser oscillator 1 which is a component of a general laser range finder and a transmission / reception optical system 2 are provided.
In addition to the light receiving circuit 3, the counter circuit 4 and the display circuit 9, the comparison circuit group 5, the delay circuit group 6, the discrimination circuit 7 and the arithmetic circuit 8 directly related to the present invention are provided.

Next, the operation of this embodiment will be described.

The light emitted from the laser oscillator 1 has its divergence angle adjusted by the transmission / reception optical system 2 and is aimed at the target 10. The light striking the target 10 is reflected, condensed by the transmission / reception optical system 2, and converted into an electric signal by the light receiving circuit 3.

The counter circuit 4 starts counting with the monitor signal of the light transmission timing provided from the laser oscillator 1 as a start signal.

The signal from the light receiving circuit 3 passes through the comparison circuit 5 and the delay circuit 6 and is discriminated by the method described below to select an appropriate signal. This is used as a stop signal in the counter circuit 4 and the arithmetic circuit 8 in the laser. Measure the propagation time of light.

The output signal from the light receiving circuit 3 is a comparison circuit group 5 having a plurality of comparison circuits having different operation levels.
The output signal discriminated in step S3 and the output signal corresponding to the operation level are supplied to the delay circuit group 6 having a plurality of delay circuits arranged corresponding to the respective levels.

The delay circuit group 6 has a plurality of delay circuits in which the delay time is set shorter as the output of the comparison circuit having the higher operation level of the corresponding comparison circuit group 5 is set. It is necessary to adjust in accordance with the pulse width of 1. However, when the output of the comparison circuit of the comparison circuit group 5 having a higher operation level is delayed, the output time is corrected so that the output from the delay circuit group 6 is corrected. The signals compared at the high operation level are set to be output earlier in time.

The discriminating circuit 7 discriminates the optimum stop signal based on the following idea and sends it to the counter circuit 4. At this time, information on what magnitude of the operation level the transmitted signal is sent to is sent to the arithmetic circuit 8.

Based on the information from the discriminating circuit 7, the arithmetic circuit 8 calculates the time measured by the counter circuit 4, that is, the time corresponding to the light propagation time and the delay time of the delay circuit 6. The net propagation time of the light after subtracting the known delay time is calculated to obtain the distance, and the distance measurement data is sent to the display circuit 9.

The display circuit 9 displays the distance measurement value in a part of the sighting field of the transmission / reception optical system 2.

FIG. 2 shows the strength of the signal from the light receiving circuit 3 and
6 is a diagram for explaining the relationship between the operation level of the comparison circuit group 5 and the delay time of the delay circuit group 7. FIG.

When the input from the light receiving circuit 3 is large, A
The operation will be described by taking two input waveforms of B as an example.

The comparison circuit group 5 sets the operation levels set in the respective comparison circuits to V1, V2, ... Vn, and the delay time in the delay circuit group 6 corresponding to this level is D1, D2.
... Dn. The time until the strong light reception signal A exceeds the operation level V1 is T11, and the time until it exceeds the level V2 is T.
12. Time to exceed level V3 is T13, level V
The time required to exceed 4 is T14. The level V5 is never exceeded. Similarly, the time until the weak light reception signal B exceeds the operation level V1 is T21, and the time until it exceeds the level V2 is T22. The level V3 is never exceeded. As described above, since the delay times D1, D2, ... Dn are properly selected in consideration of the pulse width of the laser oscillator 1, T11 + D1> T12 + D2> T13 + D3>.
The signal becomes T14 + D4, and the signal exceeding the level V4 closest to the peak of the received light signal A reaches the discrimination circuit 7 first.

Similarly, in the case of the received light signal B, the signal that exceeds the level V2 closest to the peak first reaches the discrimination circuit 7. From each arrival time to the delay time D of the delay circuit 6,
The time obtained by subtracting 4 or D2, that is, T14 or T22, is slightly different from the time to the peak of the received light signal, but it is possible to make it closer to the time to the peak by making the level interval fine.

Practically, the level interval may be selected according to the required accuracy in consideration of the complexity allowed in the device.
In addition, although the level intervals are different in the above example for the sake of convenience of explanation, it is preferable that the level intervals are not constant but are equal ratio intervals. Furthermore, since the waveform of the received light signal is gentle near the peak, the level that is the signal that reaches the second or third peak can be used without using the level that is closest to the first peak. It is useful to use That is, the vicinity of the 1/2 peak is used as a stop signal, and time correction is required for that amount, but there is an advantage that the measurement time fluctuation for one level difference is reduced. Even if the peak values of the received waveforms A and B are different due to the target reflectance and other reasons, the original shape of the laser waveform is not deformed. Therefore, the time from the peak of the waveform to the peak becomes half. Since it becomes almost constant regardless of the magnitude of the value, it is not necessary to use the vicinity of the peak where the degree of change is small if the time is corrected. By properly selecting the level interval, the time error can be reduced, so that it is possible to obtain a predetermined distance measurement accuracy.

[0026]

As described above, according to the present invention, even if the light-receiving level fluctuates, the propagation time can be accurately measured and the distance can be measured without stabilizing the light-receiving level. There is an effect that it is possible to measure the distance to the target with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of the present invention.

[Explanation of symbols]

 1 Laser Oscillator 2 Transmission / Reception Optical System 3 Light-Receiving Circuit 4 Counter Circuit 5 Comparison Circuit 6 Delay Circuit Group 7 Discrimination Circuit 8 Arithmetic Circuit 9 Display Circuit 10 Target

Claims (1)

[Claims] 1. A laser range finder for measuring a distance to a target by measuring a time difference between a timing of transmitting a laser beam and a timing of receiving a reflected light from the target, and a plurality of different comparison values are set as different comparison values. A plurality of comparison circuits for comparing the levels of the received laser light at the operation levels and sending outputs corresponding to the operation levels, and an output order corresponding to each of the outputs of the plurality of comparison circuits in order of magnitude of the operation level. A plurality of delay circuits for giving a time delay so that the output is determined, and one output is selected according to the output order based on a judgment standard preset with respect to the outputs of the plurality of delay circuits. A determination circuit for measuring an apparent propagation time to a target as received laser light, a delay time provided by the plurality of delay circuits with respect to the apparent propagation time, and the determination circuit. Equipped with an arithmetic circuit that corrects the delay time based on the output order when selecting the output to determine the true light reception timing near the peak value of the received laser light, calculates the true propagation time, and measures the distance to the target. A laser distance measuring circuit characterized by comprising: