JPS5866880A - Light wave distance measuring meter - Google Patents

Abstract

PURPOSE:To reduce the measurement time by multifrequency simultaneous measurement considerably by receiving the light wave which is intensity modulated by the signals superposed with a fine signal and a coarse signal, demultiplying the same to the original coarse signal and fine signal and detecting the phase differences between the respective signals. CONSTITUTION:The coarse signal f1 and fine signal f2 from an oscillator 1 are inputted by a modulator 2 and the light intensity of a light source 3 is modulated. The modulated light wave passes through an optical system 4 for signal transmission, is reflected by a reflecting mirror 5, enters an optical system 6 for photodetection and is detected with a photodetector 7. The output signal of the detector 7 is branched to the two original frequencies f1, f2 components by an optical demultiplexer 8. The branched frequencies f1, f2 are mixed with mixed input frequencies f1', f2' and are processed in mixer amplifiers 9a, 9b respectively. Further the respective output signals are subjected to detection of their phase differences with phase detectors 10a, 10b by using a reference frequency f0; thereafter a distance is determined with a signal processing circuit 11 and said distance is displayed on a display device 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light wave range finder that measures distance using a novel method.

Conventional light wave rangefinders emit light waves that are intensity-modulated at a specific frequency and travel back and forth between the measured distances, and utilize the fact that the phase of the received light waves differs depending on the optical path length. It was intended to be measured. In this case, a method is usually adopted in which the received signal is converted to a frequency several orders of magnitude lower by a heterogeneous input to expand the time scale and improve measurement accuracy.

However, when the optical path length is longer than the wavelength of the light wave, the number of waves existing in the optical path becomes one or more, causing uncertainty. Furthermore, if the longest optical path length for distance measurement is set equal to the wavelength of the light wave, there is a drawback that the phase difference becomes small when measuring short distances, and the measurement accuracy cannot be improved.

Therefore, two types of specific frequencies are usually used, one of which is the optical wavelength λ, which is equal to the optical path length corresponding to the longest measurement distance.
1, which is the coarse signal, and the other one is the light wave wavelength λ2 corresponding to the optical path length corresponding to the shortest measurement distance L2.
Choose to have this and use this as the essence signal. And this 2
Switch the type of signal, first perform high-precision phase measurement in units of λ2 using the fine signal, then calculate the number of λ2 (integer value) included within the measured distance using the coarse signal, and then calculate A procedure is followed to find the total distance. Therefore, the circuit configuration becomes extremely complicated, and
This method has the disadvantage that the calculation time is long and the measurement time is long.

In order to eliminate the drawbacks of the conventional example, the present invention performs optical intensity modulation using a modulation signal in which a fine signal is superimposed on a coarse signal.
This light wave is sent back and forth between the measured distances and received, and then split into the original coarse signal and fine signal, and the phase difference of each signal is detected separately, reducing measurement time by simultaneously measuring multiple frequencies. The present invention provides a light wave range finder that achieves the following. below,
Examples will be explained in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention.
The oscillator 1 outputs a coarse signal f1 and a fine signal f2, a modulator 2 generates a modulation signal, and then the light intensity of the light source 3 is modulated by this modulation signal.

This modulated light wave, for example, as shown in Figure 2,
The fine signal f2 is superimposed on the coarse signal f1. This light wave passes through the transmitting optical system 4 and is detected by the ejector 7. The output signal of this photodetector 7 is demultiplexed by a demultiplexer 8 into the original two frequency components f= and h. Thereafter, as in the conventional phase difference measurement light wave range finder, the demultiplexed frequencies f1.
,/! are the mixed input frequency fi, f′2 and the mixed input frequency fi, f′2, respectively.
The output signals are processed in the amplifiers 9as to 9b, and each of the four output signals is set to a reference frequency f. Phase detector 10 using
A and IOb perform phase difference detection, and then a signal processing circuit 1 calculates the distance, and the display device 12 shows the distance.

Since the present invention is configured as described above, it is possible to perform simultaneous measurements using multiple signals, including coarse and fine signals, compared to conventional methods that switch frequencies and measure separately. The measurement time can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of Embodiment 1 of the present invention, and FIG. 2 is a diagram showing a light wave whose light intensity is modulated by a modulation signal of a coarse signal and a fine signal. l・・・・・・・Oscillator, 2・・・・・・・・・・
・Modulator, 3...Light source, 5...
...Reflector, 7...Photodetector,
8・・・・・・・・・Brancher, 9as9b・・・・・・
...mixer/amplifier, lOa, 10b...
. . . Phase detector, 11 . . . Signal processing circuit, 12 . . . Display device.

Claims (1)

[Claims] A first signal of a specific frequency is used as a rough measurement signal, and the first signal has a specific frequency.
modulating means for superimposing a second signal having a higher frequency than the signal for precision measurement on the first signal; means for receiving light by reciprocating it between measurement distances; demultiplexing means for extracting the first signal and second signal from the received light signal; and a demultiplexing means for extracting the first signal and the second signal from the received light signal; 1. Phase detection means for detecting the phase. Then,
A light wave rangefinder that uses multiple frequencies to perform rough and precise measurements at the same time.