JPH01320488A - Method and instrument for measuring distance - Google Patents

Abstract

PURPOSE:To eliminate the influence of intensity modulation of laser light by dividing beat signals, the amplitude of which is decreased depending upon the intensity of reflected light from an object to be measured by the signal corresponding to the reflected light from the object. CONSTITUTION:A reference mirror 11 is irradiated by light having an intensity which is about 1/2 as strong as that of laser light and an object 9 to be measured is irradiated by light having an intensity which is about 1/4 as strong as that the of the laser light. The reflected light from the object 9 is divided into the light advancing straight and the light branched at a right angle by means of a beam splitter 7 after passing through a lens system 8 and the branched light is made incident to a photodetector 13. The reflected light advancing straight is reflected by a mirror 11 and the interference light of the reflected light from the mirror 11 led to a beam splitter 6 through a lens system 10 and the light directly led to the beam splitter 6 from the beam splitter 7 is detected by a photodetector 12. Beat signals having a small amplitude corresponding to the intensity ratio between both reflected light are outputted from the photodetector 12 and signals having a small amplitude decided by the reflection coefficient, etc., of the object 9 are outputted from the photodetector 13. Both signal are influenced form intensity modulated components. The signals outputted from the photodetectors 12 and 13 are supplied to a divider 14 where division is performed in corresponding to both signals.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a distance 11111 determination method and apparatus, and more specifically, to a method for reflecting a part of a frequency-modulated laser beam by an object to be measured. The present invention also relates to a distance measuring device that measures the distance to a measurement target by reflecting the remaining light on a reference reflector and then causing both reflected lights to interfere.

<Prior Art> Conventionally, devices with various configurations have been provided for fixing the distance to an object to be measured. Specifically, there are those that apply the triangular 1TIl principle, and those that apply the principle that the interference of light, ultrasonic waves, etc. changes based on the difference in distance, but there are applications that require high measurement accuracy. 111, the laser beam is not easily affected by external conditions, etc.
It is preferable to use it as a constant light.

Distance measuring devices that use the above-mentioned laser beam as measuring light have conventionally been provided based on the principle shown in FIG. 4.

That is, a current source (32) is controlled by a modulation source (31) to control the current injected into a semiconductor laser (hereinafter abbreviated as LD) (33), and frequency-modulated laser light (34) is controlled. ) (for frequency modulating the laser beam by changing the injection current, for example, G, BEHEIM, PRITSCI (, ELE
CTRONIC8LETTER331ST JANUA
RY 1985 Vol, 21 qa). This laser beam (34) is guided through a lens (35) to a beam splitter (36) consisting of a half mirror, forming two laser beams (34a) pointing at right angles to each other.
(34b), one laser beam (34a)
is irradiated onto the mirror (37), and the other laser beam (34b) is irradiated onto the object to be measured (39) through the lens (38). The respective laser beams (34a) (34b) are mirrored (
37), is reflected by the object to be measured (39), guided again to the beam splitter (36), and guided to the detector (40) in an interference state. The detector (40) includes a conventional component that calculates the distance to a fixed object (39) based on a beat signal corresponding to the interference light, as well as an electric signal corresponding to the interference light. It has a light receiving element (42) that generates an electric signal corresponding to the laser beam (34) emitted from the light receiving element (41) and the laser beam (34) emitted from the light receiving element (41). It has a divider (43) that divides the output electric signal by the electric signal output from the light receiving element (42).

With the distance measuring device having the above configuration, the beam is guided back to the beam splitter (36) in accordance with the distance from the beam splitter (36) to the mirror (37) and the distance to the object to be measured (39). Since the interfered laser beam is guided to the detector (40), the divider (43
), the beat signal is divided by the electric signal corresponding to the laser beam (34) to eliminate the influence of the intensity modulation of the laser beam (34) emitted from the LD (33), and then noise components are removed, etc. After that, both laser beams (3
4a) The difference in distance can be detected by detecting the beat caused by the temporal change in the phase difference in (34b).

Furthermore, since the distance to the mirror (37) is set to a known predetermined distance that serves as a reference, by adding or subtracting the difference in distance to the known predetermined distance that serves as a reference, ) can also be detected.

<Problems to be Solved by the Invention> In the distance measuring device described above, even if the laser beam (34) output from the LD (33) is subjected to intensity modulation,
The divider (43) makes it possible to obtain a beat signal that eliminates the influence of intensity modulation, but since the intensity of the light reflected from the M1 constant object (39) is generally significantly reduced, the mirror By interfering with the reflected light from (37), the intensity of the beat component obtained becomes significantly low. Conversely, since the intensity of the laser beam (34) is significantly higher than the intensity of the reflected light from the M1 constant object (39), the L
By dividing the beat signal based on the electrical signal output from the light receiving element connected to common with D (33), by dividing the beat signal, which originally has a low level, based on the laser light intensity signal, which has a high level, - The layer level is reduced.

Therefore, depending on the material of the measurement object (39), it becomes impossible to use the signal after division as it is as a signal for distance calculation, and an amplifier is inserted to compensate for the level drop. The problem is that it becomes necessary.

To explain in more detail, the reflected light (hereinafter referred to as local light) Er (t) from the mirror (37) is converted to Er (
t)=k (t)EOcos (2πν01+θ(t
)) ...■ (However, E
If O is the amplitude of electrolysis, ν0 is the center frequency of the laser beam (34), and k (t) is the coefficient due to intensity modulation), and α2 is the intensity ratio of the signal light to the local light, then the signal light Es
(t) is Es (t) −ak (t−r)EOcos f
2πν0(-τ) 10(t-τ))...
・It becomes ■.

Here, since k(t) can be regarded as -τ, the intensity I (t) of the interference light is I (
t)-k (t)E O(1+α2)+2αk
(t)E20cos! 2πνOr+θ (t)−θ
(t − τ))
... becomes ■.

Furthermore, assuming that the modulation of L D (33) is triangular wave modulation, and assuming that the modulation current is im1 and the modulation frequency is fi, the intensity Ir (t) of the local light is
)−E20 + (d I/d i) 2 fra
1II11 ・
...■ (where ■ is the laser light output and i is the injection current). Also, from the above equation 0, Ir (t)−k (t)E20 −
...■, so from the above formula 00, k
(t)=1+(2/E20)(d I/d i)f
m im t...
■It becomes.

Therefore, by substituting the above equation 0 into the above equation 0, the interference light intensity I (t) is 1 (t) - (1+α) fE20 +2 (d
I/d 1) fi im tl +2α tE2
0 +2 (d I/di) fm 1IIt) c
osf2πνOr+θ(1)−〇 (t−τ))
... becomes ■.

cos(2yrνOr+θ(t)-θ(t-
Since a linear DC component is superimposed on the beat signal represented by τ), it can be seen that the beat signal is linearly amplitude-modulated. In addition, the intensity 1c (t) of the light received by the light receiving element commonly connected to the LD is Ic (t) - E20 + (d I/d i)2
fm imt
...Since ■, if we divide the ■ expression by the ■ expression, we get 1
(t)/Ic (t)-(1+α2)+2αC08(
2πν0τ+θ(1)−θ(t−τ))...■ The influence of intensity modulation is eliminated. Furthermore, as is clear from equation (2), it can be seen that the amplitude of the beat signal is determined by the intensity of the signal light relative to the local light.

If the reference side is a mirror, the intensity ratio α2 of the two lights is 0.02 if the object to be measured (39) is wood, 0.008 if it is rubber, 0.01 if it is paper, and 0.01 if it is plastic. becomes 0.1, and the amplitude of the beat signal becomes extremely small.

<Object of the invention> This invention was made in view of the above problems,
In addition to being able to eliminate the influence of the intensity modulation component of the laser beam, it is also possible to obtain a beat signal of a sufficient level even if the ratio of the intensity of the reflected light from the measurement object to the intensity of the reflected light from the reference reflector is small. The purpose of the present invention is to provide a distance measuring device and its device that can perform the following tasks.

Means for Solving the Problems To achieve the above object, the distance measuring method of the present invention divides the beat signal by a signal corresponding to the reflected light from the object to be measured, and then removes the noise component. This is a method of calculating the distance to a measurement target based on a signal from which noise components have been removed.

In order to achieve the above object, the distance measuring device of the present invention includes an optical branching means for branching a part of the reflected light from the object to be measured before interference, and generating an electric signal corresponding to the branched light. and a dividing means that divides the beat signal based on the electrical signal generated in the light receiving element.

In order to achieve the above object, the distance 4-1 constant device of another invention is such that the light irradiated to the reference reflector is light having only a polarization component in one direction, and the light irradiated to the measurement target. The light has polarization components in mutually orthogonal directions,
An optical branching means for branching only the light having a polarized component in a direction orthogonal to the polarized component of the light reflected from the reference reflector from the light in which both incident lights are interfered, and an electric signal corresponding to the branched light. The beat signal has a light receiving element that generates the beat signal, and a dividing means that divides the beat signal based on the electric signal generated in the light receiving element.

However, in addition to having a polarization-maintaining optical fiber that guides the emitted light from the semiconductor laser to the measurement target, it is also necessary to provide a reflective-transmissive lens as a reference reflector at a predetermined position of the polarization-maintaining optical fiber. preferable.

In the distance measurement method described above, a part of the laser light output from the semiconductor laser is irradiated to the n1 constant target object, and the rest is irradiated to the reference reflector, so that the reflected light from the measurement target, By interfering with the reflected light from the reference reflector, a beat signal with a frequency determined based on the optical path length of the reference reflector and the optical path length of the object to be measured can be obtained.

This beat signal is affected by the intensity modulation of the laser beam, and the reflected light from the object to be measured is also affected by the intensity modulation, but it corresponds to the reflected light from the object to be measured. By dividing the beat signal by the signal, it is possible to obtain a beat signal from which the influence of the intensity modulation component has been eliminated. In this case, the amplitude of the beat signal is determined based on the ratio of the reflected light intensity from the reference reflector to the reflected light intensity from the object to be measured, but if the above ratio is small, the amplitude becomes the divisor. Since the signal corresponding to the reflected light from the object to be measured also has a smaller amplitude,
The beat signal obtained after the division has amplified amplitude.

To explain in more detail, the interference light intensity 1 (t) is 1 (t) - (1 + α ) fE20 + 2 (dl/di
) fti is tl +2a (E20 +
2 (dl/di)fi im tl cos(2π
νOr+θ(1)−〇(−τ)), and the reflected light intensity Is (t) from the measurement object is Is (t
)-a k (t)E20, the interference light intensity I (t) is the reflected light intensity Is (t
), then 1 (t)/Is (t)=1
+1/α2+ (2/α)cos(2πν0τ+θ(1
)−〇(−τ)). Here, since the value of α is smaller than 1, even if the amplitude of the beat signal is small due to the small amplitude of the reflected light intensity Is (t), by performing the above division, the amplitude can be made larger.

Therefore, the distance can be calculated without any amplification.

Therefore, after that, the noise component can be removed, and the distance to the object to be measured can be accurately calculated based on the signal from which the noise component has been removed.

With the distance measuring device configured as above, the laser beam output from the semiconductor laser is divided into two parts, one of which is irradiated onto the object to be measured, and the other is irradiated with the reference reflector, and the laser beam output from the M1 constant object is irradiated into two. By interfering the reflected light and the reflected light from the reference reflector, a beat signal with a frequency determined based on the optical path length of the reference reflector and the optical path length of the object to be measured can be obtained.

In addition, by branching a part of the reflected light from the object to be measured before interference by the light branching means and having the light received by the light receiving element, it is possible to obtain an electric signal that is a divisor for the beat signal.

Therefore, by supplying the beat signal and the electric signal serving as the divisor to the dividing means, it is possible to obtain a beat signal in which the influence of the intensity modulation component is eliminated and the amplitude is amplified, and based on the obtained beat signal, The distance to the object to be measured can be calculated with high accuracy.

In addition, in the case of a distance measuring device having another configuration, part of the laser light output from the semiconductor laser is irradiated onto the object to be measured, and the remaining part is irradiated onto the reference reflector, so that the reflected light from the object to be measured, By interfering with the reflected light from the reference reflector, a beat signal with a frequency determined based on the optical path length of the reference reflector and the optical path length of the object to be measured can be obtained.

However, since the light irradiated to the reference reflector has only a polarized component in one direction, and the light irradiated to the measurement object has polarized components in mutually orthogonal directions, each The reflected light also becomes light having equal polarization components. As a result, when both reflected lights are caused to interfere, only the light of the polarization component common to both interferes with each other, and the light of other polarization components is preserved without any interference.

Therefore, the light branching means can branch only the light of the polarized component in the direction orthogonal to the polarized component of the light reflected from the reference reflector from the light in which both reflected lights are interfered with. By guiding light to a light receiving element and generating an electrical signal corresponding to the branched light, and supplying this electrical signal as a divisor to the dividing means, the influence of the intensity modulation component is eliminated and the amplitude is amplified. A beat signal can be obtained, and the distance to the object to be measured can be accurately calculated based on the obtained beat signal.

The case further includes a polarization-maintaining optical fiber that guides the light emitted from the semiconductor laser to the measurement target, and a reflective-transmissive lens as a reference reflector is provided at a predetermined position of the polarization-maintaining optical fiber. In this case, since the light propagating inside the polarization-maintaining optical fiber is hardly affected by atmospheric conditions, the accuracy of determining the distance 7n1 can be improved.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a schematic diagram showing an embodiment of the distance measuring device of the present invention.

The LD (1) that outputs the laser beam for measurement is electrically connected to
A predetermined temperature is maintained stabilized by a Peltier element (2), which is a type of heat conversion element, and an injection current is supplied by a drive current control section (3). Then, by changing the injection current supplied by the drive current control section (port), frequency modulation is applied to the laser light.

A lens system (5), a beam splitter (6) (7), and a lens system (8) are arranged in this order on the optical path of the laser beam (4) from the L D (1) to the object to be measured (9). There is. A lens system 00) and a reference mirror (11) are arranged in this order on the optical path of the laser beam split by the beam splitter (6), and the lens system 00) is placed around the beam splitter (6).
) A photodetector (12) is arranged on the opposite side. Further, a photodetector (13) is arranged on the same side of the beam splitter (7) as the photodetector (12).

Also, a divider (14) which inputs the electrical signals output from both the photodetectors (12) and (13), and a divider (14)
A comparator (16) that compares the output signal from the filter (15) with a predetermined reference signal, a counter (17) that counts the comparison result signal, and a coefficient A calculator that calculates the distance based on the signal (
18).

The divider (14) is supplied with the output signal from the photodetector (12) as a dividend, and also receives the output signal from the photodetector (13).
) is supplied as the divisor.

The operation of the distance measuring device having the above configuration is as follows.

If the frequency of the laser light (4) emitted from the LD (1) is modulated by changing the injection current in a triangular wave shape by the drive current control unit (3), the frequency will change in a triangular wave shape and the laser light intensity will change. changes in response to changes in the injected current. In other words, it becomes as if frequency modulation and intensity modulation have been applied.

The laser beam (4) passes through the lens system (5) and is guided to the beam splitter (6), so that the laser beam (4a) travels straight.
and the light (4b) that is branched at right angles,
The branched light (4b) passes through a lens system 00) and is irradiated onto a reference mirror (11) whose optical path length is known. Then, the straight-traveling light (4a) is guided to the beam splitter (7), so it is split into two in the same way as when it is guided to the beam splitter (6), and the straight-traveling light passes through the lens system (8) and has an optical path length of is irradiated onto an unknown measurement object (9). That is, light with an intensity of about 172 of the laser beam (4) is irradiated onto the reference mirror (11), and light with an intensity of about 1/4 of the laser beam (4) is irradiated onto the object to be measured (9).

The light reflected by the object to be measured (9) passes through the lens system (8) and is guided to the beam splitter (7), where it is split into two parts: straight forward light and perpendicularly branched light. The light is irradiated onto a photodetector (13). In addition, when the reflected light traveling straight through the beam splitter (7) is guided to the beam splitter (6), the reference mirror (1
Interference occurs with the light reflected from 1) and guided to the beam splitter (6) through the lens system (10), and the interference light is irradiated onto the photodetector (I2).

That is, the photodetector (12) outputs a beat signal with a small amplitude corresponding to the intensity ratio of both reflected lights, and the photodetector (13) outputs a beat signal determined by the reflection coefficient of the measurement object (9), etc. A signal with small amplitude is output.

Both of the above signals are affected by the intensity modulation component.

Since the signals output from the photodetectors (12) and (13) are supplied to the divider (14), by performing division based on both signals, the influence of the intensity modulation component can be eliminated. Moreover, the beat signal and photodetector (13
Even though the amplitude of the signal output from ) is small, a division result signal with sufficient amplitude can be obtained.

Therefore, the obtained division result signal is filtered (15)
The frequency of the beat signal is determined by supplying it to a comparator (1B) to remove noise components, converting it to a pulse signal train by supplying it to a comparator (1B), and counting the number of pulse signals within a predetermined time in a counter (17). can be obtained, and the obtained beat signal frequency is applied to a calculator (18
), the distance to the object to be measured (9) can be calculated by performing a predetermined calculation.

As is clear from the above explanation, by dividing the beat signal affected by the intensity modulation by the reflected light from the measurement object (9) affected by the intensity modulation, the effect of the intensity modulation can be eliminated. The eliminated beat signal can be obtained, and the small amplitude of the beat signal due to the low intensity of the reflected light from the measurement object (9) can be determined by Jl + constant object (9), which also has a low intensity. ), the amplitude of the division resultant signal can be made considerably large. therefore,
Post-processing can be performed without using any amplifiers.

<Embodiment 2> Fig. 2 is a schematic diagram of the main part showing another embodiment of the distance 7i11 constant device, and the configuration of the part after the divider (14) is as follows.
Since it is the same as the embodiment shown in the figure, illustration is omitted.

Only one beam splitter (6) is disposed between the L D (1) and the object to be measured (9), and a beam splitter (6) is placed between the reference mirror side and the object side of the beam splitter (6). A λ/4 wavelength plate (19) (20) is provided respectively. The beam splitter (6) is located on the opposite side of the reference mirror (11).
21) is arranged, and a beam splitter (
21), a polarizer (22) and a photodetector (12) are arranged in this order in the direction of light traveling straight through the polarizer, and a polarizer (23) and a photodetector (I3) are arranged in this order in the direction of light branching at right angles. ing.

The operation of the distance measuring device having the above configuration is as follows.

The laser light emitted from the L D (1) is guided to the beam splitter (6), where it is split into two parts, one that travels straight and the other that travels perpendicularly.
19), the light is converted into elliptically polarized light and linearly polarized light, and is irradiated onto a reference mirror (11) and a 4pj constant object (9), respectively.

The light reflected by the reference mirror (11) and the light reflected by the object to be measured (9) are both guided to the beam splitter (6) through opposite paths and are combined into one light beam, but they are different from each other. Since the light is of different polarization, no interference occurs. This light is further guided to a beam splitter (2I), where it is split into two, one that travels straight and one that travels at right angles. Then, the light in the perpendicular direction passes through the polarizer (23), so that only the polarized component orthogonal to the linearly polarized light irradiated on the reference mirror (11) is extracted, and the light is sent to the photodetector (13).
is irradiated. On the other hand, light traveling straight is polarizer (22
), the polarization directions are aligned and the interference light is irradiated onto the photodetector (12).

Therefore, from the photodetectors (12) (13), the first
Similar to the embodiment shown in the figure, electric signals corresponding to the beat signal and the reflected light from the measurement object (9) are output, and based on both signals, intensity modulation components are removed, noise components are removed, and the beat signal frequency is adjusted. Detection and calculation of the distance to the measurement target (9) can be performed.

However, the mounting angle of the λ/4 wavelength plate (20) can be set arbitrarily.

(Embodiment 3) Fig. 3 is a schematic view of the main parts of yet another embodiment of the distance measuring device, and the difference from the embodiment shown in Fig. 2 is that the end face of the beam splitter (6) on the side of the object to be measured is A polarization-maintaining optical fiber (24) is provided in the polarization-maintaining optical fiber (24).
The only difference is that a nof mirror (25) and a λ/4 wavelength plate (26) are provided in this order on the end face of the measurement object side of 24).

Therefore, in this embodiment, a part of the light propagating from the beam splitter (6) through the polarization-maintaining optical fiber (24) is reflected by the half mirror (25), and the polarization-maintaining optical fiber (24) is reflected by the half mirror (25). 24) in the opposite direction and is guided to the beam splitter (6). In addition, the remaining light passes through the half mirror (25) and then passes through the λ/4 wavelength plate (26).
and is irradiated onto the measurement object (9) as elliptically polarized light,
The elliptically polarized light reflected by the measurement object (9) passes through a λ/4 wavelength plate (2B) and a half mirror (25), and further propagates through a polarization-maintaining optical fiber to a beam splitter (6).
).

Then, both lights are combined into one light by the beam splitter (6), and as in the embodiment shown in FIG. The reflected light from (9) is separated into lights corresponding to the reflected light. Therefore, after that, the intensity modulation component and the noise component are removed in the same manner as described above, and then the beat signal frequency is detected and the distance to the All constant object (9) is calculated.

As is clear from the above explanation, in this example,
Since the distance that light propagates inside the polarization-maintaining optical fiber (24) is quite long, this part is not only less susceptible to atmospheric conditions, but also is irradiated to and reflected from the measurement object (9). Because the signal light and the reference light that is irradiated and reflected by the half mirror pass through the same optical path, both lights are affected by the atmospheric conditions to the same extent, which significantly reduces errors caused by atmospheric conditions and improves distance measurement accuracy. can be significantly increased.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, a right-angle mirror or a corner cube may be used in place of the reference mirror (11), and within the scope of the present invention without changing the gist of the present invention. It is possible to make various design changes within.

<Effects of the Invention> As described above, the first invention divides the beat signal whose amplitude is reduced depending on the intensity of reflected light from the object to be measured by the signal corresponding to the light reflected from the object to be measured. This has the unique effect of being able to eliminate the effects of intensity modulation of the laser beam and making the amplitude of the signal from which the effects of intensity modulation have been removed large enough for post-processing. play.

In the second invention, the beat signal whose amplitude is reduced depending on the intensity of the reflected light from the object to be measured is divided by the signal corresponding to the light reflected from the object to be measured.
The influence of intensity modulation of the laser beam can be eliminated, and the amplitude of the signal from which the influence of intensity modulation has been eliminated can be made large enough for post-processing. This has the unique effect of eliminating the need for an amplifier and simplifying the configuration of the distance measuring device.

The third invention suppresses the extent to which the amplitude of the beat signal is reduced by preventing the intensity of the reflected light from the measurement object from becoming significantly lower than that of the reflected light from the reference reflector, and the intensity modulation. This has the unique effect of increasing the amplitude of the beat signal from which the influence has been removed.

In the fourth invention, since the reference reflector is provided integrally with the polarization-maintaining optical fiber, there is no need to separately provide an optical system leading to the reference reflector in addition to the optical system leading to the measurement object, and the overall This has the unique effect of simplifying the optical system, suppressing the influence of atmospheric conditions, and significantly increasing distance measurement accuracy.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing one embodiment of the distance measuring device of the present invention, Figs. 2 and 3 are schematic diagrams showing other embodiments of the distance measuring device, respectively, and Fig. 4 shows a conventional example. Schematic. (1)...LD, (3)...drive current control section, (4
)...Laser light, (4a)...Light traveling straight, (4b
)...Light branched in the right angle direction, (6)(7)(
21)...Beam splitter, (9)...Measurement object, (11)...Reference mirror, (12X13)...
Photodetector, (14)...Divider, (19) (20)
(2B)...λ/4 wavelength plate, (24)...Polarization maintaining optical fiber, (25)...Half mirror Patent applicant: Daikin Industries, Ltd. Representative Patent attorney: Tomoji Tsugawa No. 1 Figure 2 Figure 3 Figure 4 O jl 31

Claims (1)

[Claims] 1. Laser light (4) output from semiconductor laser (1)
A part (4a) of the measured object (9) is irradiated, and the remaining part (4b) is irradiated to the reference reflector (11), and the reflected light from the measured object (9) and the reference reflector (11) are irradiated. ) in a distance measurement method in which a beat signal is obtained by interfering with the reflected light from the object (9) and distance data is obtained based on the beat signal, after dividing the beat signal by a signal corresponding to the reflected light from the measurement object (9), A distance measuring method characterized in that a noise component is removed and a distance to a measurement target (9) is calculated based on the signal from which the noise component has been removed. 2. Laser light (4) output from semiconductor laser (1)
is divided into two parts, one side (4a) is irradiated onto the measurement object (9), and the other side (4b) is irradiated onto the reference reflector (11), and the reflected light from the measurement object (9) and the reference are irradiated. In a distance measuring device that obtains a beat signal by interfering reflected light from a reflector (11) and obtains distance data based on the beat signal, a part of the reflected light from the measurement target (9) before interference is branched. a light-receiving element (13) that generates an electrical signal corresponding to the branched light; and a dividing means that divides the beat signal based on the electrical signal generated in the light-receiving element (13). (14) A distance measuring device comprising: 3. Laser light (4) output from semiconductor laser (1)
A part (4a) of the measured object (9) is irradiated, and the remaining part (4b) is irradiated to the reference reflector (11), thereby reflecting light from the measuring object (9) and the reference reflector (11). ) in a distance measuring device that obtains a beat signal by interfering with the reflected light from the center and obtains distance data based on the beat signal. At the same time, the light irradiated onto the measurement object (9) is light having polarization components in mutually orthogonal directions, and the light reflected from the reference reflector (11) is the result of interference of both reflected lights. A light branching means (6) that branches only the light of the polarized component in the direction perpendicular to the polarized component of the light, a light receiving element (12) that generates an electric signal corresponding to the branched light, and a light receiving element (12). A distance measuring device comprising: dividing means (14) for dividing the beat signal based on the electrical signal generated in the step. 4. The light emitted from the semiconductor laser (1) is transferred to the measurement target (9).
), and a half mirror (25) as a reference reflector is provided at a predetermined position of the polarization-maintaining optical fiber (24). The distance measuring device according to item 3.