JPH02216492A - Range-finding device by light wave - Google Patents

Abstract

PURPOSE:To improve range resolution by providing a means for irradiating with the collimated beam of laser light facing to a corner cube prism or a plane reflection mirror and a means for detecting the reflected light beam from the corner cube prism or the plane reflection mirror. CONSTITUTION:As to a range-finding device by light wave, a laser interferometer is constituted of a laser diode 3b, semitransparent mirrors 5c and 5d, a photodiode 9b, a collimator lens 23 and a plane mirror 31. In this case, the reflected light beam of the laser beam from the plane mirror 31 and the reflected light beam of the laser beam from the corner cube prism 6 overlap and interfere each other on the incident surface of the photodiode 9b and the light beam detecting output of the photodiode 9b becomes larger every time the distance to the corner cube prism 6 changes by the half of the wavelength of the laser beam. Thus, the range-finding device by light wave with high accuracy and high data rate can be accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light wave ranging device used for measuring the distance to a target aircraft with high precision, for example, during a lunch-to-doing in space.

[Conventional technology]

FIG. 2 shows an example of a conventional optical distance measuring device. In FIG. 1, 13 is a reference oscillator, and (2) is a drive circuit.

(3) is a laser diode driven by intensity modulation by this drive circuit (21), (4) is a transmitting lens, (5) is a semi-transparent mirror, and (6) is a corner cube prism that is a target.

(71#i mirror (8) is the receiving lens, (9) is the photodiode placed at the focal position of the receiving lens (8),
αG is an amplifier, αυ is a phase comparator, az is a distance signal, a
3 is a band pass filter, (14 is a phase comparator +1
α9 is a phase measurement input signal. Figure 3 is a diagram showing an example of the configuration of the phase comparator (+11), (16a) and (16b) are the binarization circuits, aη is the set signal applied to the flip-flop a9, aS is the reset signal, and the wire is the oscillator. , an is a flip-flop a
Gate QD controlled by the output of QD is a counter that counts the output pulses of the oscillator Q outputted from the gate QD.

The conventional light wave distance measuring device is constructed as described above and operates as follows. The laser diode (3) is the reference oscillator il
oscillates laser light whose intensity is modulated at the frequency output from +. The laser beam whose irradiation angle is narrowed down by the transmission lens (4) and passes through the semi-transmissive mirror (5) is irradiated toward a corner cube prism (6) which is a distance R away. Since the corner cube prism (6) has the property that the incident angle and the output angle of light are equal, the reflected laser beam returns again along the same optical path and is redirected by the semi-transparent mirror (5). 171, and passes through a bandpass filter αj that matches the wavelength of the laser beam.The function of this bandpass filter α is to prevent interference light other than the laser beam (such as sunlight) from entering the photodetection system. .Receiving lens (8)
The laser light incident on the photodiode (91) is collected at the light receiving part and photoelectrically converted. The photoelectrically converted signal is amplified in amplitude by an amplifier and applied to two phase comparators all. It is applied to a phase comparator αB. Reference signal I and 9 phase measurement input signals (L!g is the binarization circuit (16a),
In (16b), the output pulse of the oscillator ■ that passed through the gate c + n only during the phase shift time of the borrowed sign in the binary substitution 6 can be counted by the counter @, so that the waveform output from the single oscillator c section 1 of n, M is obtained. We can find out the time it takes for a to pass through the system observed above. Letting this time be Tt, the following equation holds.

Tt=2OR+To・・・・・・・・・・・・
-... (1) However, C: Speed of light TO: The delay time To, O of the circuit system can be known in advance. Become. Therefore, it can be seen that the two distance signals fig represent the distance.

[Problem to be solved by the invention]

In conventional light wave ranging devices such as those described above, measurement errors are mainly caused by the amount of noise contained in the phase measurement input signal α.
Can't be ignored. The above noise is random noise generated from the photodiode (91) and the amplifier αG, so the distance signal a
A common method is to measure Z over a long period of time and average it to reduce the measurement error, but at the cost of this, the data rate becomes smaller. However, in Rendezvous Dotsking.

Distance measurement in short range areas requires high accuracy and high data rate, and conventional light wave ranging devices are not sufficient.

The present invention was made to solve this problem, and an object of the present invention is to obtain a light wave ranging device with high accuracy and high data rate.

[A precautionary measure to solve the problem]

The light wave distance measuring device according to this invention is a conventional light wave distance measuring device with a laser interferometer added thereto.

[Effect]

In this invention, the distance resolution of the laser interferometer is half the wavelength of the laser beam, so the distance resolution is much higher than that of the conventional example. Furthermore, by using a laser interferometer, the processing circuit becomes simple, so the data rate can be increased.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention (II.

+21. +41. (61, (71, (81, αυ~
The mackerel is exactly the same as the conventional device example above, (5
a), (3b), (sa), (sb) (5c), (5
d), (9a), (9b), (16c') If
i Each of the above conventional compensation examples (3) j (51, 171, (9
1, (t6a), and (t6b). υ
is a collimator lens that converts the output light of the laser diode (5b) into parallel light.

This also has the effect of focusing the received light onto the photodiode (9b). - is an amplifier that increases the output amplitude of the laser diode (9b), @ is a subtraction counter.

(2) is a laser power supply that supplies power to the laser diode (3b), @ is an averaging circuit that calculates the average of distance signals a2 of a predetermined number of data based on the calibration instruction signal, (to) is a reference distance signal, (to is ) is a precision distance signal, and all is a plane mirror.

The optical distance measuring device configured as described above includes a laser diode (3b) and a semi-transparent mirror (5C).

(5d), a 7-otodiode (9b), a collimator lens (c), and a plane mirror 011 constitute a laser interferometer, and on the incident surface of the photodiode (9b), the reflected light of the laser beam from the plane mirror Ca1l and the , the reflected laser beams from the corner cube prism (6) overlap and interfere, and each time the distance to the corner cube prism (6) changes by half the wavelength of the laser beam, the photodiode (9b)
) increases the light detection output. Therefore, each time the distance to the corner cube prism (6) changes by half the wavelength of the laser beam, the count value of the subtraction counter (c) becomes smaller. When rendezvous and docking, corner cube prisms (6
) is a monotonically decreasing value, and the change in the count value of the subtraction counter corresponds to the change in the distance. on the other hand,
With a laser interferometer, the absolute distance is not known, so at least once.

It is necessary to set the initial value of the subtraction counter (c).

This is an average circuit operated by the calibration instruction signal (2) @
Subtract the reference distance signal (to) which is the output of the counter (to)
This is done by setting it to . Note that it is necessary to select different oscillation wavelengths of the laser diodes (' a ) t (s b ) so that they do not interfere with each other.

〔Effect of the invention〕

The present invention has the effect of realizing a high-precision, high-data-rate optical distance measuring device by adding a laser interferometer to the above-described system.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a conventional light wave distance measuring device, and FIG. 3 is a diagram showing an example of the configuration of the phase comparator U in FIG. 2. It is. In the figure, (1) is the reference oscillator, (2) is the drive circuit,
(31° (3a), (5b) are laser diodes, (
4) is the transmission lens &"'j(") *(5b)*(5
C), (sa) are semi-transparent mirrors (6) are corner cube prisms, (7) are mirrors (8) are receiving lenses, (
91, (9a)t (9b) are photodiodes, trout is an amplifier, αfl is a phase comparator, and 03 is a distance signal. as, (13a), (txb) is /<n)”/<
Sufil fi, Q4! d reference signal, (1!9
are phase measurement signal inputs, (16a) and (16b). (16C) is a binary circuit, D71 is a set signal, a second is a reset signal, (ail is a flip-flop, (A) is an oscillator, Qll is a gate, @ is a counter, r23 is a collimator lens, L2A is an amplifier, @ is a subtraction counter, @ is a laser power supply, fin is an average circuit, @ is a reference distance signal, @ is a calibration instruction signal, (l [l is a precision distance signal, 0]) is a plane mirror. Note that in each figure The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a light wave distance measuring device for measuring a distance to a corner cube prism or a plane reflecting mirror, a means for irradiating parallel laser light to a corner cube prism or a plane reflecting mirror, means for detecting reflected light from a corner cube prism or a plane reflecting mirror; a semi-transmissive mirror disposed at a common portion of the optical path of the collimated laser beam and the reflected light at an angle with respect to the optical axis; A light wave distance measuring device comprising: a plane mirror disposed perpendicularly to the optical axis in the optical path of the parallel laser beam that is split by the laser beam.