JPH0126516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a light wave measurement method that precisely measures the distance to a point to be measured based on the phase difference between a modulated light wave sent to the point to be measured and a modulated light wave reflected and returned from the point to be measured. This invention relates to a distance method and device.

In recent years, light wave distance meters have come into widespread use for distance measurement, mainly in the field of surveying. A light wave distance meter sends out light waves modulated at a predetermined modulation frequency toward a reflector consisting of a corner cube installed at a measurement point, receives the light waves that are reflected by the reflector, and returns. The distance to the measurement point is measured based on the phase difference between the light wave and the transmitted light wave.

At present, the light source for optical rangefinders is:
Light emitting diodes are being used due to the demand for smaller and lighter devices. However, since the maximum measurable distance of a light-wave rangefinder is determined by the brightness of the light source, the maximum measurable distance of a light-wave rangefinder using a light-emitting diode has been limited to 2 to 3 km.

He--Ne gas lasers were used in optical distance meters for longer distance measurements, but using He--Ne gas lasers as a light source would require a large laser tube, which would result in an increase in the size of the device. However, it requires a high-voltage, high-capacity power source, which is inconvenient for outdoor surveying.Furthermore, it is susceptible to temperature changes and shocks, and it is not suitable for laser light modulation.
It was also necessary to use an electro-optical element such as KDP.

In recent years, with the advancement of semiconductor technology, semiconductor lasers have become available. If this semiconductor laser is used as a light source for a light wave distance meter, a high-brightness light source similar to that of a conventional gas laser can be obtained, making it possible to make maximum measurements. The distance can be greatly extended, and the size and power consumption are on the same level as conventional light emitting diodes.Furthermore, since the semiconductor laser itself can be modulated, not only does it require no special modulation means, but the light emission response is also very low. Since the speed is faster than that of a light emitting diode, the modulation frequency can be increased, and a light wave distance meter with higher measurement accuracy can be produced.

However, when a semiconductor laser is used as a light emitting source for an optical distance meter, the following problems occur. In other words, when a rectangular modulated wave is applied to a semiconductor laser to emit modulated light, the waveform of the modulated light is not exactly rectangular but has a different shape depending on the exit angle.For example, light at a certain exit angle is The waveform has a sharp protrusion at the front end, the light with another exit angle has a medium-high waveform with a bulge in the center, and the light with yet another exit angle has a waveform with a bulge in the front half, and so on. Become. Such a difference in the waveforms of the modulated waves means that the sine waves, which are the fundamental wave components, have different phases. For this reason, there will be a difference in the measurement results depending on which emission angle the light receiving section receives the light.

By the way, in actual distance measurement using a light wave distance meter,
A reflector such as a corner cube placed at a measurement point is not always installed under the same conditions with respect to a light wave distance meter. For example, if the corner cube is disposed laterally offset from the optical axis, the light rays incident on the light receiving element and involved in measurement will have different exit angles. Furthermore, since the light beam emitted from the objective lens of a light wave distance meter is not completely parallel but has some spread, the light rays involved in the measurement change depending on the measurement distance. Furthermore, changes occur due to slight tremors and air fluctuations at the installation site where the corner cube is installed. These changes in the light beams involved in the measurement will cause differences in the measurement results based on the differences in their waveforms.

Furthermore, in the case of a conventionally used light emitting diode, its light emitting area is larger than that of a semiconductor laser, and it is well known that a difference in emission point causes a difference in the phase of modulated light. In light wave distance meters using light emitting diodes, various types of phase mixing devices have been proposed in order to solve this problem of phase difference of modulated light. Although these phase mixing devices can solve some of the problems with light-wave distance meters that use light-emitting diodes,
This method is not effective in solving the above-mentioned problem in a semiconductor laser, which has a very small area of a light emitting part and can be expected to serve as an almost perfect point light source.

The present invention was made in view of the problems of the light emitting source in the conventional light wave distance meter,
The first object is to provide a new light wave distance measuring method and apparatus in which the difference in phase difference between emitted light beams emitted from a light emitting source does not contribute to errors in distance measurement data.

A second object of the present invention is to prevent changes in phase difference between emitted light beams from contributing to errors in distance measurement data without making any significant improvements or changes to conventional light wave distance meters. An object of the present invention is to provide a light wave distance measuring device that is more accurate than conventional light wave distance meters.

Furthermore, the third purpose of the present application is to solve the problem that when a semiconductor laser is used as a light emitting source, the phase difference change between the emitted light beams depending on the emitting angle causes an error in the distance measurement data, and to fully put it into practical use. Not only is it more efficient, but it is also smaller, lighter, consumes less power, has a longer maximum measurement distance, and has higher measurement accuracy than conventional light-wave distance meters that use light-emitting diodes or gas lasers as light sources. The objective is to provide a measurement system.

That is, the present invention includes a step of emitting a distance measuring light beam from a light emitting source driven at a predetermined modulation frequency, a step of transmitting the distance measuring beam to a point to be measured by an optical means, and a step of transmitting the distance measuring beam to a point to be measured. receiving a reflected light beam from the distance measuring light beam reflected from the point;
In a light wave ranging method that measures the phase difference between a reflected light beam and a distance measuring light beam, and measures the distance to the distance measurement point based on the phase difference, a plurality of waveforms inevitably generated from the light emitting source are differentiated. In order to eliminate the influence of the distance measurement light rays, the distance measurement optical path formed by the distance measurement light rays and the reflected light rays is configured so that at least one of the distance measurement light rays is propagated at a different time from the other distance measurement light rays. The present invention provides a light wave ranging method based on the following methods.

Furthermore, the present invention includes a light emitting source that is driven at a predetermined modulation frequency and emits a distance measuring light beam, an optical means for sending the distance measuring light beam from the light source to a distance measurement point, and a light emitting source that emits a distance measuring light beam from the light emitting source. a phase difference measuring means for receiving a reflected beam of the distance measuring beam reflected at the distance measuring point and measuring a phase difference between the distance measuring beam and the reflected beam; and a distance to the distance measuring point from this phase difference. In a light wave distance measuring device comprising a calculation means for calculating, a plurality of distance measuring light beams having different waveforms inevitably generated from the light emitting source are formed by a distance measuring light beam and a reflected light beam. The present invention provides a light wave distance measuring device characterized by having a mixing means for propagating light onto a distance measuring optical path at different times.

In the present invention, "distance measuring light rays with different waveforms" refers to cases where the shapes of the output waveforms are different depending on the light beams, or cases where the output waveforms have the same shape but differ only in phase. It is used in a meaning that also includes.

According to the above-mentioned features of the present invention, even in conventional light-wave distance measuring methods and devices that use light emitting diodes as light sources, higher accuracy can be obtained compared to conventional methods. This opens the way to the practical use of a light wave ranging method and device that uses a semiconductor laser as a light source, and allows the maximum measurement distance to be greatly extended compared to a light emitting diode type light wave ranging device. Highly accurate ranging accuracy can be obtained. In addition, compared to conventional gas laser type optical distance measuring devices, it is smaller and lighter, consumes less power, and can be used for long-term surveying outdoors, and does not require special electro-optical elements for modulation. It is possible to provide an extremely useful new optical distance measuring device that does not

Embodiments of the present invention will be described in detail below with reference to the drawings. In the following embodiments, only the case where a semiconductor laser is used as the light emitting source will be explained, but the present invention is not limited to this, and the present invention is similarly applicable to a case where a light emitting diode is used as the light emitting source.

FIG. 1 is a block diagram showing the configuration of a light wave range finder as an example of a light wave range finder according to the present invention. The frequency divider 10 divides the 15MHz signal from the oscillator 11 into two signals, 75KHz and 3K.
Generates Hz. The synthesizer 13 receives the output from the oscillator 11.
Difference between 15MHz and 3KHz from frequency divider 10 (15MHz-
3KHz) to 14.997MHz and a 72KHz signal from the frequency divider 10, which is 24 times 3KHz.
The first switch 14 receives the signal 1 from the processing control circuit 15.
6 outputs one of the signals from 15MHz to 75KHz. A semiconductor laser 18 disposed within the mixer section 17 is driven by the output signal of the first switching device 14 and emits modulated light, and an optical expander 21 composed of a lens 19 and a lens 20 is connected to the semiconductor laser 18 .
The light is incident on the optical fiber 22 by the following. The modulated light emitted from the optical fiber 22 is emitted into either the distance measurement optical path 23 or the internal reference optical path 24 by a shutter 25 that switches between the distance measurement optical path 23 and the internal reference optical path 24. Distance measurement optical path 23
When is selected, the modulated light is reflected by the slope 26a of the prism 26, then converted into a parallel beam by the objective lens 27, and sent out toward a reflector R, such as a corner cube, installed at the point to be measured. The reflected light from the reflector R passes through the objective lens 27 and the slope 26b of the prism 26, enters the optical fiber 28, and is received by the light receiving element 30 made of an avalanche photodiode via the optical expander 29. When the internal reference optical path is selected by the shutter 25, the modulated light emitted from the optical fiber 22 is reflected by the internal reflection surface 26c of the prism 26, directly enters the optical fiber 28, and is transmitted to the light receiving element 3.
Light is received at 0.

This internal reference optical path is used to prevent phase changes caused by temperature drift of the electric circuit that makes up the optical distance meter itself from causing errors in distance measurement data. Obtain accurate ranging data by subtracting from the measured value.

The second switch 31 outputs either a 14997 MHz or 72 KHz signal depending on the signal 16 from the processing control circuit 15. The output from the light receiving element 30 is amplified by an amplifier 32 via a capacitor 50 and input to a mixer 33. The mixer 33 is the amplifier 32
A beat signal is created by mixing the signal from the second switch 31 with the signal from the second switch 31, and the beat signal is detected.
Outputs a 3KHz sine wave. Waveform shaper 34 is 3K
Outputs a signal obtained by shaping a Hz sine wave into a rectangular wave (hereinafter referred to as a beatdown signal). The gate circuit 35 uses the 3KHz signal from the frequency divider 10 as a start signal, uses the signal from the waveform shaper 34 as a stop signal, and uses the signal from the oscillator 11 in between.
A 15MHz signal is output to the counter 36. The phase difference is measured by counting this signal with a counter 36. The count value obtained by the counter 36 is the total number of N measurements. In order to know the number of N times, a 3KHz signal from the frequency divider 10 is supplied to the processing control circuit 15. When counting N times is completed, a reset signal 37 is supplied from the processing control circuit 15 to the counter 36, and the counter 36 enters the reset state. The count value of N measurements is multiplied by 1/N in a processing control circuit to obtain an average value, which is converted into a distance and displayed on the display 39 as a measured distance value.

In order to make the output of the mixer 33 3KHz, the first
The output signal of the switch 14 and the output signal of the second switch 31 are controlled by the signal 16 from the processing control circuit 15 so that the relationship is 14997 MHz when the frequency is 15 MHz, and 72 MHz when the frequency is 75 KHz. Semiconductor laser 18
The reason why it is modulated at two frequencies, 15 MHz and 75 KHz, is that 15 MHz corresponds to a wavelength of 20 m and is used for precise measurements, and 75 kHz corresponds to a wavelength of 4 km and is used for rough measurements. To convert the frequencies of 15MHz and 75KHz to 3KHz using the mixer 33,
This is to increase the resolution of phase measurement, and the frequency is 15MHz.
Or to measure the phase at 75KHz by changing it to 3KHz.

A semiconductor laser 8 used as a light source in this example emits light modulated with different waveforms depending on the emission angle. Figures 2a, b, and c are examples.
The modulated lights having different waveforms have different phases in their basic component, sine wave, and the measurement results differ depending on which modulated light reaches the light receiving section. The mixer section 17 allows modulated lights with different emission angles to be emitted one after the other in time to the distance measuring optical path and reach the light receiving section via the reflected optical path, and has the optical fiber 22 as described above. .

Optical fiber 22 of mixer section 17
is wound into a coil several times, and one of its circular parts
The side surface of the vibrator 41 is in contact with the pressing piece 40, and the piston 41a of the vibrator 41 is pressed against the opposite side surface.
The vibrator 41 is caused to vibrate by being driven by an oscillation source 42 that is not synchronized with the modulated wave signal.
The mixing effect of the light emitted from the semiconductor laser 18 due to the vibration of the optical fiber 22 is schematically shown in FIGS. 3a, b, and c. The semiconductor laser 18 is modulated with a rectangular modulated wave as shown in _FIG . Assume that a ray B having the modulated output waveform shown in Fig. _2b is emitted at an angle of θ 2, and a ray C having the modulated output waveform shown in Fig. 2c is emitted at an angle of exit angle θ ₃ . do. When each of these emitted lights enters the vibrating optical fiber 22 via the optical expander 21, a certain time t ₁
In this case, as shown in FIG. 3a, the light ray A from the optical fiber 22 is at an angle θ ₁ '.
Ray B is emitted from angle θ' ₂ and ray C is emitted from angle θ' _3. At time t ₂ , ray B is emitted from angle θ ₁ ' and ray C is emitted from angle θ ₂ ', as shown in FIG. 3b. C
However, the rays A are also emitted from the angle θ ₃ ',
Furthermore, at time _t3 , as shown in FIG. 3c, ray C is emitted from angle θ ₁ ', ray A is emitted from angle θ ₂ ', and ray B is emitted from angle θ ₃ '. By vibrating the optical fiber 22 in this way, the light rays A, B, and C emitted from a certain angle, for example, θ ₁ ', are randomly mixed. This state is shown in FIG. 4b.

FIG. 4c shows the semiconductor laser 18 shown in FIG. 4a.
FIG. 3 is a diagram showing a sine wave that is the fundamental component of a rectangular modulated wave added to the sine wave.

The fundamental sine wave of the modulated output waveform of the emitted light beam from the angle θ ₁ ' has a phase difference with the modulated wave applied to the semiconductor laser, so that the modulated wave output waveform does not change from time to time, as shown in Figure 4d. becomes a sine wave that changes from moment to moment as △ _A , △ _B , and △ _C. However, since the beatdown signal from the waveform shaper 34 used for phase difference measurement has a much lower frequency than the modulated wave, the phase difference of the beatdown signal is the average value of the phase difference of each mixed light beam. This results in a beatdown signal with a phase difference of _Δ0 (Fig. 4 e, f).

This is also true for the light beams at the exit angles θ ₂ ' and θ ₃ ', and is true for the light rays exiting the optical fiber 22 at all exit angles.

The mixing effect is more effective as the frequency at which the same type of modulated wave waveform appears repeatedly in a certain direction (hereinafter referred to as the beam switching frequency) is higher than the frequency of the averaging means. FIG. 4b shows an example in which the beam switching frequency is lower than the modulation frequency, but the reverse may also be the case. FIGS. 4a' to 4f' correspond to FIGS. 4a to 4f when the beam switching frequency is higher than the modulation frequency. In this case, the output waveform of the modulated wave emitted from the angle θ ₁ ' is as shown in Figure 4b',
A mixing effect appears within the period of the modulated wave, and the fundamental sine wave becomes a mixed one as shown in FIG. 4 d'. Figure 5 shows the emitted light when the light from the semiconductor laser 18 modulated at a modulation frequency of 75 KHz is incident on the optical fiber 22 vibrated at 1 KHz, and the emitted light is synchronized at 75 KHz and displayed on the screen of the synchroscope. The waveform is the same at all exit angles θ ₁ ′, θ ₂ ′, and θ ₃ ′. This means that the phase difference of the beatdown signal from the waveform shaper 34 is the same regardless of the exit angle.

In the light wave distance meter, the phase is measured many times and the average value is obtained by the processing control circuit 15, which is used as the final result, so that the above-mentioned light beam switching frequency is sufficiently effective even if it is not high. In other words, the light beam switching frequency may be sufficiently fast compared to the time it takes to perform a large number of phase measurements to obtain one measurement value.

If the beam switching frequency is lower than the time required to perform phase measurement to obtain one measurement value, the measurement data will vary. Therefore, it is desirable that the beam switching frequency be sufficiently high compared to the time during which phase measurements are performed. However, by increasing the beam switching frequency as shown in the modulation waveform shown in Figure 5,
It is not necessarily necessary to temporally average different rays; the first phase measurement is made with ray A, the second with ray B, the third with ray C, and so on. Phase measurements may be made with separate beams and the measurements obtained from the average of the phase measurements.

FIG. 6 shows the results of an experiment on the distance measurement accuracy of a light wave distance meter using the mixer section 17 of FIG. 1, and a comparison of the effects of the mixer section.

The light wave distance meter provides distance measurement data at a modulation frequency of 75KHz for rough measurements and for precise measurements.
Although both distance measurement data at a modulation frequency of 15MHz are combined to form the final measurement data, the experimental data in Figure 6 is shown separately for 75KHz measurement data and 15MHz measurement data to make it easier to understand.

Figures 6a and 6b are data when the vibrator 41 is not driven and no vibration is applied to the optical fiber 22 of the mixer section 17, and a is
75KHz measurement data is shown, b is 15MHz measurement data, the vertical axis shows the measured distance value, and the horizontal axis shows the number of measurements from the first measurement to the nth measurement.

6c and d show the measurement results when the optical fiber 22 of the mixer section 17 was vibrated (1 KHz vibration) by the vibrator 41, respectively.
Figure 6c shows the measured data at 75KHz, and d shows the measured data at 15MHz. Measurements are made from the main body of the light wave distance meter.
A reflector was installed at a position of m, and the distance between the two was measured. As can be seen from the measurement results in FIGS. 6a and 6b, if the mixer section 17 is not operated, it will be affected by slight vibrations and air fluctuations at the installation location, and variations in the light beam involved in the measurement will directly affect the measurement data. Dispersion in measured distance data increases. On the other hand, as is clear from the measurement results shown in FIGS. 6c and 6d, when the mixer section 17 is driven, there is almost no variation in the measured distance data.

Generally, in order to avoid the effects of temperature drift in the electric circuit, an optical distance meter is provided with an internal optical path 24 inside the device, as shown in FIG. section passes.

When the distance measuring optical path 23 and the internal optical path 24 are formed as two separate optical paths in this way, the waveforms of the light beam passing through the distance measuring optical path and the light beam passing through the internal optical path will be different if the mixer section 17 is not present. Therefore, even if you try to obtain accurate distance measurement data by subtracting the phase difference of the internal optical path from the phase difference of the distance measurement optical path, the distance measurement data will be inaccurate because the light flux passing through both optical paths is different, and the offset will occur. Appears as a value. In particular, the offset value of measurement data using a 75KHz modulated light wave must be considered important. Generally, 75KHz and
When combining 15MHz data to obtain the final result, add or subtract a value of approximately 1m or less to the 75KHz data to match the meter units. The measurement results in Figure 6a show an average of about 18m, while Figure 6b shows an average of about 7.1m. For example, Figure 6a,
If there is a difference of 1m or more in meters, such as the nth _1st and nth _2nd measurement data of b, it is no longer possible to
It becomes impossible to synthesize 75KHz data and 15MHz data. On the other hand, Fig. 6c shows a measured distance of approximately 17.8m, and Fig. 6d shows a distance measurement of approximately 17.8m.
It shows approximately 7.877m, and there is no difference between the two.

Although the example of the mixer unit 17 described above is one that vibrates the optical fiber 22, the present invention is not limited to this, and the basic configuration is to temporally change the light beam propagating on the distance measuring optical path. Other arrangements may be used to meet the requirements.

Figures 7a and 7b show a second embodiment of the mixer section of the invention. In this embodiment, a parallel plane glass 100 that rotates and vibrates in the direction of an arrow 101 within the range of angle γ is provided between the two lenses 19 and 20 constituting the optical expander 21. The light beams A and B having different modulated output waveforms are emitted from a secondary light source 18' that is optically conjugate with the light emitting point of the semiconductor laser 18 at an emission angle θ ₁ ' that changes over time. It is something.

FIGS. 8a and 8b show the parallel plane glass 100 of the previous example.
Instead, an example will be shown in which a corrugated disk 102 having a similar effect is placed between the lenses 19 and 20 and rotated about a rotation axis O' parallel to the optical axis O. In any of the embodiments described above, the emitted light beam at a certain angle is changed by swinging the light emitted from the semiconductor laser 18 and changing the final emission angle. FIG. 9 shows the laser chip 1 by vibrating the semiconductor laser 18 itself, which is a light source.
The waveform of the light beam emitted from a certain point on the objective lens surface is substantially changed over time by changing the emission angle θ' of the light beam l emitted from 8a itself at an emission angle θ with respect to the optical axis O.

That is, the semiconductor laser 18 is attached to the mounting substrate 110 via electrically vibrating vibrators such as piezoelectric elements 111a and 111b, and is caused to vibrate by passing an alternating current through the piezoelectric elements. The semiconductor laser 18 is configured to rotate and vibrate with respect to the optical axis O.

10a and 10b show that the embodiment of FIG. 1 vibrates the middle part of the optical fiber with a vibrator 41, whereas the embodiment of FIG.
The light beams are mixed by vibrating the incident end 22a of the optical fiber and changing the angle of incidence of the light beams onto the optical fiber.

Furthermore, the mixer section does not necessarily need to be placed inside the optical distance meter, and as shown in FIG.
00 is attached to the housing 200 of the optical distance meter via piezoelectric elements 111a and 111b, and alternating currents from oscillators 42 and 42' having different oscillation phases are applied to the piezoelectric elements to cause them to vibrate, thereby creating a parallel plane glass 100. By rotating and vibrating the device around an axis perpendicular to the optical axis O of the device, the light ray m after exiting the objective lens is translated in parallel, or the incident position of the reflected light ray n from a reflector (not shown) on the objective lens is changed, When one distance measurement optical path is considered, it is possible to cause substantially the same effect as when light rays with different waveforms propagate through the measurement optical path at different times.

Furthermore, the objective lens that sends the distance measuring light beam m toward the reflector placed at the distance measurement point does not necessarily have to be a refracting light beam as in each of the above embodiments, but a Cassegrain type as shown in FIG. It may be an objective optical system 300 consisting of a reflective optical system, and the mixing means, as shown in the figure, combines a blower 301 and a heater 302 to actively create air fluctuations 303, and uses this air fluctuation to measure distance. The exit angle and the incident angle of the optical ray m and the reflected ray n may be changed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a light wave distance meter showing the first embodiment of the present invention, Fig. 2 a, b, and c are photographs showing waveforms of light rays with different emission angles of a semiconductor laser, and Fig. 3
Figures a, b, and c are optical layout diagrams schematically showing the action of the mixer part of the present invention, Figure 4 is a waveform diagram showing the action of the mixer part, and Figure 5 is a photograph showing an example of the waveform after mixing. Fig. 6 is a diagram showing the dispersion of distance measurement data to show the effect of the present invention on distance measurement;
Figures a and b show the second embodiment of the present invention;
Figures a and b show the third embodiment of the present invention;
The figure shows the fourth embodiment of the present invention, FIGS. 10a and 10b show the fifth embodiment of the invention, and FIG.
The figure shows a sixth embodiment of the invention, and FIG. 12 shows a seventh embodiment of the invention. DESCRIPTION OF SYMBOLS 11... Oscillator, 18... Semiconductor laser, 17... Mixer part, 27... Objective lens, 41... Vibrator, 22... Optical fiber.

Claims (1)

[Claims] 1. A step of emitting a distance measuring light beam from a light emitting source driven at a predetermined modulation frequency; a step of transmitting the distance measuring light beam to a point to be measured by optical means; A step of receiving a reflected beam of the distance measuring beam reflected from the distance measuring point, measuring a phase difference between the reflected beam and the distance measuring beam, and calculating the distance to the distance measuring point from the phase difference. In the light wave distance measuring method for measuring, in order to eliminate the influence of the distance measuring light beam that is inevitably generated from the light emitting source and which causes different waveforms, the distance measuring method formed by the distance measuring light beam and the reflected light beam is used. A light wave ranging method characterized in that at least one of the plurality of ranging light beams is propagated along an optical path at a different time from other ranging light rays. 2. At least one of the plurality of distance measuring light beams is connected to another distance measuring light beam at a certain point of the optical means,
2. The light wave distance measuring method according to claim 1, wherein the light waves are emitted at different times. 3. The step of measuring the phase difference further includes the step of measuring the phase difference a plurality of times for one distance measurement point and averaging the plurality of phase difference values. At least 2 ranging rays
3. The optical distance measuring method according to claim 1, wherein the time required for emitting the light twice is shorter than the time required for averaging the phase difference values. 4. A light emitting source that is driven at a predetermined modulation frequency and emits a distance measuring light beam; an optical means for transmitting the light beam from the light emitting source to a distance measuring point; a phase difference measuring means for receiving a reflected light beam from the distance measuring light beam and measuring a phase difference between the distance measuring light beam and the reflected light beam; and calculating a distance to the distance measurement point from this phase difference. A light wave ranging device comprising: a calculation means, wherein a plurality of ranging light beams having different waveforms are inevitably generated from the light emitting source, and are formed by the ranging light beam and the reflected light beam. A light wave distance measuring device comprising a mixing means in a distance measuring optical path for causing propagation at different times. 5. Claim 4, wherein the mixing means emits at least one of the plurality of distance measuring light beams at a certain point of the optical means at a different time from other distance measuring light beams. The light wave ranging device described. 6. The phase difference measuring means further includes averaging processing means for performing phase difference measurement a plurality of times for one distance measurement point and averaging the plurality of phase difference values, and the point at which the optical means has a certain point is of the same kind. 6. The optical distance measuring device according to claim 4, wherein the time required for the distance measuring light beam to be emitted at least twice is shorter than the averaging time of the averaging processing means. 7. The optical distance measuring device according to any one of claims 4 to 6, wherein the light emitting source is a semiconductor laser.