JPH01233383A - Laser distance measuring apparatus - Google Patents

Abstract

PURPOSE:To use an interference optical fiber with a narrow band width for the removal of a background light, by controlling an oscillation wavelength of a semiconductor laser with the regulation of the length of a resonator based on a quantity difference in the transmission light monitoring the quantity of transmission light of the filter. CONSTITUTION:A part of laser light outputted from a semiconductor laser 1 is taken out with a beam splitter 14 and divided in two with a partial mirror 15 and a mirror 16. The laser light is introduced to narrow band interference optical filters 17 and 18 for monitoring with a different center wavelength. An interference optical filter whose center wavelength is at an intermediate area of the center wavelength of the filters is used as reception one 4. As an oscillation wavelength of the semiconductor laser 1 varies in level from the center wavelength lambda of the reception interference optical filter 4, outputs of two detectors 19 and 20 change and a variation of a transmission wavelength is discriminated with a monitoring section 21 according to the level and direction thereof to output a drive signal to a PTZ controller 22 corresponding to the variation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laser range finder, and more particularly to a laser range finder using a semiconductor laser.

[Conventional technology]

FIG. 2 shows the configuration of a conventional laser distance measuring device using a semiconductor laser.

The semiconductor laser 1 is driven in synchronization with a trigger signal output from the timing controller 7.

Laser light output from the semiconductor laser 1 is emitted toward a target through a transmission optical system 2.

The laser beam reflected from the target is collected by a receiving optical system 3 and sent to a detector 5 through an interference optical filter 4 for removing background light. The received signal converted into an electrical signal by the detector 5 is guided to the timing controller 7 by the amplifier 6. The time from when the semiconductor laser beam is sent out to when the received signal enters the timing controller 7 is measured, and this time is converted into distance and displayed on the display 8.
Display the distance.

[The problem that the idea aims to solve]

In the conventional laser distance measuring device described above, the emission wavelength of the semiconductor laser changes depending on the temperature of the semiconductor laser, and the wavelength change range is wide, for example, 500 people, so it is not suitable as an interference optical filter for removing background light during reception. , it is necessary to use an interference optical filter having a transmission band that includes the wavelength change range described above.

For this reason, the effect of background light removal cannot be expected to be very effective, and therefore effective distance measurement can only be performed at night when there is little background light, or at short distances where the signal light is sufficiently larger than the background light. The disadvantage is that it is limited.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser distance measuring device that can eliminate the above-mentioned drawbacks and can significantly improve the effect of background light removal using an interference optical filter with a narrow transmission bandwidth.

[Means to solve the problem]

The device of the present invention is a laser ranging device using a semiconductor laser, in which a part of the laser light generated by the semiconductor laser is taken out, and this is transmitted to at least two laser beams each having a different center wavelength and a narrow transmission bandwidth. means for monitoring the amount of transmitted light through an interference optical filter; and at least two
and means for controlling the resonator length of the semiconductor laser based on the difference in the amount of light transmitted through the interference optical filters to maintain the emission wavelength of the semiconductor laser within a predetermined range.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In the embodiment of FIG. 1, symbols 1 to 10 are the same as those of the same number in FIG.

In FIG. 1, 11 is a resonator output mirror that constitutes the resonator of the semiconductor laser 1, 12 is a resonator total reflection mirror, 13 is PZT for changing the resonator length, and 14 is the resonator output mirror of the semiconductor laser 1.
a beam splitter for extracting a part of the output light of the
5 is a partial mirror that reflects the laser beam extracted by the beam splitter 14 and the remaining half; 1;
6 is a reflecting mirror, 17 and 18 are narrow bandwidth monitoring interference optical filters with slightly different center wavelengths, and 2O is a monitoring photodetector for monitoring the amount of light transmitted through the interference optical filters 17 and 18. , 21 is a monitor photodetector 19
．． A monitor section 22 monitors the signal difference from 20 and detects a variation in the oscillation wavelength of the semiconductor laser 1, and 22 is, for example, a PZT controller for controlling the resonator length of the semiconductor laser 1.

A portion of the laser light output from the semiconductor laser 1 is extracted by the beam splitter 14 and divided into two parts by the partial mirror 15 and the mirror 16. The two-split laser beam is guided to narrow-band monitoring interference optical filters 17 and 18 whose center wavelengths are slightly different. An interference optical filter whose center wavelength is between the center wavelengths of the monitoring interference optical filters 17 and 18 is used as the reception interference optical filter 4. This relationship is shown in FIG. 3. In FIG. 3, 23, 24, and 25 are respectively used as interference optical filters 4 for reception. This relationship is shown in FIG. 3. In FIG. 3, 23, 24° 25 are the transmission characteristics of the interference optical filter for reception, the transmission characteristics of the interference optical filter 17 for monitoring, and the transmission characteristics of the interference optical filter 18 for monitoring. It is a characteristic.

The oscillation wavelength of the semiconductor laser 1 is detected by the receiving interference optical filter 4.
Suppose that the wavelength changes from the center wavelength to the longer wavelength side. At this time,
The outputs of the monitoring photodetectors 19 and 20 are arranged in a monitoring interference optical filter 17 having a large transmittance on the long wavelength side. The output of the monitoring photodetector 19 increases,
On the other hand, the output of the monitoring photodetector 20 becomes smaller.

On the other hand, when the oscillation wavelength changes to the shorter wavelength side, the output of the monitoring photodetector 20 increases, and the output of the monitoring photodetector 19 increases.
output becomes smaller. In this way, the amount of change in the emission wavelength is determined by the monitor unit 21 based on the magnitude and direction of the outputs of the two photodetectors, and the drive signal corresponding to the amount of change is transmitted to the PTZ.
Output to the controller 22.

It is generally known that the oscillation wavelength of a laser shifts to the shorter wavelength side as the resonator length becomes longer, and to the longer wavelength side as the resonator length becomes shorter. Therefore, if the monitor 21 determines that the wavelength has shifted to the longer wavelength side, the voltage applied to the PZT 13 is increased to increase the resonator length, and on the other hand, when the wavelength is shifted to the shorter wavelength side, the voltage applied to the PZT 13 is lowered. Do it like this.

〔Effect of the invention〕

As explained above, in a laser distance measuring device using a semiconductor laser, the oscillation wavelength of the semiconductor laser is adjusted based on the difference in the amount of transmitted light while monitoring the amount of transmitted light of an interference optical filter having a narrow transmission bandwidth. By controlling the laser cavity length, it is possible to use a narrow-bandwidth filter as an interference optical filter for background light removal during reception, which has the effect of significantly increasing the effect of background light removal. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the laser distance measuring device of the present invention, FIG. 2 is a block diagram of a conventional laser distance measuring device, and FIG. 3 is a block diagram of an interference optical filter used in the embodiment of FIG. FIG. 3 is an explanatory diagram of transmission characteristics. 1... Semiconductor laser, 2... Transmission optical system, 3...
Reception optical system, 4... interference optical filter for reception, 5...
・Detector, 6... Amplifier, 7... Timing controller, 8... Display device, 9... Transmission beam, 10.
... Reception beam, 11... Resonator output mirror, 12.
...Resonator total reflection mirror, 13...PZT, 14...
・Beam splitter 115...partial mirror,
16...Mirror, 17° 18...Interference optical filter for monitor, 19.20...Photodetector for monitor, 21.
...Monitor section, 22...PTZ controller, 23.
・Transmission characteristics of interference optical filter for reception, 24.25・
...Transmission characteristics of interference optical filters for monitors.

Claims (1)

[Claims] In a laser ranging device using a semiconductor laser, a part of the laser light generated by the semiconductor laser is extracted and passed through at least two interference optical filters each having a narrow transmission bandwidth with a different center wavelength. means for monitoring the amount of light; and means for controlling the resonator length of the semiconductor laser based on the difference in the amount of transmitted light between the at least two interference optical filters to maintain the emission wavelength of the semiconductor laser within a predetermined range. A laser distance measuring device characterized by: