JPS63150684A - Laser radar visual sensor - Google Patents

Abstract

PURPOSE:To increase the level of a beam signal for heterodyne detection and to observe an object which is low in refractive index by providing a Galilean type beam diameter conversion telescope in the optical path of at least either of reference laser light and reflected laser light. CONSTITUTION:Laser light from a laser oscillator 1 is split by a beam splitter 2 into signal laser light 21 and the reference laser light 22. The signal laser light 21 is projected on the object 7 through an acoustooptic modulating element 3, a reflecting mirror 5, the hole of a holed mirror 10, and a scanner 30. Its reflected light is bent by the holed mirror 10, and reduced in beam diameter by the Galilean type beam diameter conversion telescope composed of a convex lens 14 and a concave lens 15 to obtain the reflected laser light 801. This reflected laser light 80 is mixed by a beam splitter 11 with reference laser light 22, condensed by a lens 12, and heterodyne-detected by a detector 13.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a laser radar visual sensor that can simultaneously obtain distance information and visual information.

2. Description of the Related Art A conventional persimmon laser radar vision sensor is described, for example, in Applied Optics, Vol. 23, p. 2565 (Appl.
, ○ptics, 23, P2565 1984), it had a configuration as shown in Fig. 3.

That is, a laser beam emitted from a laser oscillator 1 is split into a signal laser beam 21 and a reference laser beam 2 by a beam splitter 2.
Separate into 2. The signal laser beam 21 is transferred to a frequency shifter 23
The signal is shifted in frequency by a reflecting mirror 25 and guided to a modulator 26 .

The other non-frequency-shifted laser beam that comes out of the frequency shifter 23 is guided to an output meter 24 and used as monitor light. The laser beam passing through the modulator 26 passes through the convex lens 2
The beam diameter is expanded by a Keplerian beam diameter conversion telescope configured with 7.28, bent by a reflecting mirror 29, and irradiated onto the object 7 by a two-dimensional scanning scanner 30. The reflected laser beam 8 from the object 7 varies from regular reflection to complete diffusion depending on the surface condition of the object 7, but the reflected laser beam 8 corresponds to the area 9 corresponding to the aperture of the scanner 30 and is contained. It will be done. A reflected laser beam 81 collected by the scanner 30 is mixed with a reference laser beam 22 by a beam splitter 11, focused by a lens 12, and subjected to heterodyne detection by a detector 13.

Problems to be Solved by the Invention However, in an optical system with such a configuration, the reflected laser beam 8
There was a problem in that the beam diameters of the reference laser beam 1 and the reference laser beam 22 were extremely different, and effective heterodyne detection could not be performed.This is due to the following reasons.

In other words, in heterogain detection, the reference laser beam 22, which is light at the original frequency, and the reflected laser beam 81, which is frequency-shifted, are mixed, and the difference frequency between the two laser beams, that is,
It detects a beat signal with a shift frequency, but 2
It is necessary to make the wavefronts of the two laser beams perfectly coincide with each other so that the two laser beams enter the detector 13. Here, if the diameters of the two laser beams are different, the wavefronts cannot be completely matched, and the reflected laser beam 81 is not effectively used.

The present invention is intended to solve the above-mentioned problems, and aims to achieve high sensitivity by making the wavefronts of two laser beams perfectly match and effectively using reflected laser beams.

A means for solving the problems and a technical means of the present invention for solving the above problems is to provide a beam diameter conversion telescope on at least one of the reference laser beam and the reflected laser beam. .

For production The effect of this technical means is as follows.

That is, in the present invention, the beam diameter of at least one of the reference laser beam and the reflected laser beam is converted using a beam conversion telescope, and the two laser beams are mixed after matching the beam diameters of both, so that the two laser beams are The wavefronts of the two will match perfectly, and all inputs will contribute to the heterogain detection. As a result, detection is possible even if the intensity of the reflected laser light from the object is weak.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, a laser beam emitted from a laser oscillator 1 is separated by a beam splitter 2 into a signal laser beam 21 and a reference laser beam 22. The signal laser beam 21 is diffracted by the acousto-optic modulation element 3 and undergoes frequency shift and intensity modulation at the same time. The transmitted light that has not been frequency shifted is used as a monitor with an output total of 4. The intensity-modulated laser beam is bent by a reflecting mirror 5, passes through a hole in a perforated mirror 10, and is irradiated onto an object 7 by a scanner 30. Of the reflected laser beam 8 from the object 7, an area 9 corresponding to the aperture of the scanner 30
It is taken in by. The reflected laser beam 81 collected by the scanner 30 is subjected to hetero gain detection by the detector 13 using the perforated mirror 10 . At this time, the specifications of the beam diameter conversion telescope are determined so that the beam diameters of the reference laser beam 22 and the reflected laser beam 801 are equal. The reduction rate of the beam diameter is determined by the ratio of the focal lengths of the convex lens 14 and the concave lens 15.

In this embodiment, since the reflected radar' light 81 is reduced to the reflected laser beam 801 by the beam diameter conversion telescope, the beam splitter 11 and the lens 12 need only have small diameters, and the optical system can be made inexpensive. Furthermore, since the diameters of the reference laser beam 22 and the reflected laser beam 801 are equal and their wavefronts match, the intensity of the beat signal of the hetero gain detection is also increased.

Next, other embodiments of the present invention will be described.

FIG. 2 shows another embodiment. The same parts in the figure as in FIG. 1 are given the same reference numerals. In this embodiment, a Galilean beam diameter conversion telescope is provided in the optical path of the reference laser beam 22. In this embodiment, the beam diameter is expanded by the concave lens 15, and the beam is made into parallel light by the convex lens 14. At this time, the specifications of the telescope are determined so that the diameters of the reflected laser beam 81 and the enlarged reference laser beam 202 are made equal.

This embodiment has the advantage that optical adjustment for mixing is easy because the diameters of the two laser beams are large.

Effects of the Invention As described above, the present invention provides a Galilean beam diameter conversion telescope in the optical path of at least one of the reference laser beam and the reflected laser beam, so that the beam diameters of the two laser beams can be changed. Since the wave fronts can be made equal and mixed, the intensity of the beat signal of the hetero gain detection becomes stronger, making it possible to observe objects with low reflectance. Further, by adopting a pre-lay type telescope, spherical aberration can be reduced, and at the same time, the device can be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a laser radar vision sensor according to an embodiment of the present invention, Fig. 2 is a block diagram of a laser radar vision sensor according to another embodiment of the present invention, and Fig. 3 is a block diagram of a conventional laser radar vision sensor. FIG. DESCRIPTION OF SYMBOLS 1... Laser oscillator, 3... Acousto-optic modulation element, 10... Hexagonal mirror, 11... Beam splitter, 13... Detector, 14... ... Convex lens, 15 ... Concave lens, 22 ... Reference laser beam, 30 ... Scanner, 81 ... Reflected laser light.

Claims (2)

[Claims] (1) A laser oscillator, an acousto-optic modulation element for frequency shifting and intensity modulation of laser light, and a scanner for two-dimensionally scanning an object with the frequency-shifted laser light;
A laser radar vision sensor comprising a detector for heterodyne detection of a reflected laser beam from an object and a reference laser beam, and a beam diameter conversion telescope provided in at least one of the optical paths of the reflected laser beam and the reference laser beam. (2) The laser radar visual sensor according to claim 1, wherein the beam diameter conversion telescope is a Galilean telescope.