JPH0267986A - Optical heterodyne detector - Google Patents

Abstract

PURPOSE:To measure two-dimensional distributions of highly sensitive frequencies, phases and amplitudes by providing a laser beam input means, a laser- diameter converting means, a second input mans for reference light and a detecting means of an output signal. CONSTITUTION:A photodetector 3 receives detected light 1 which has passed through a beam splitter 2. A laser generator 4 generates laser light whose frequency is different from that of the detected light 1. A beam-diameter converter 6 receives the laser light generated in the generator 4. The diameter of the beam is converted into the beam diameter smaller than the beam diameter of the detected light 1, and reference light 5 is formed. A beam scanning part 7 receives the reference light 5 generated in the converter 6 and performs scanning. The direction of the reference light 2 is changed with the beam splitter 2. The reference light 5 is inputted to an arbitrary point (x, y) on the light receiving surface of the photodetector 3 in the same direction as the detected light 1. The output signal from the photodetector 3 is detected by a detecting circuit 8. Thus, amplitude U0 (x, y), frequency omega0 (x, y) and phase phi (x, y) of the detected light 1 are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical heterodyne detection device, and particularly an optical heterodyne detection device suitable for measuring the two-dimensional distribution of the amplitude, phase, and frequency of light. The present invention relates to a laser projection device suitable for use in the optical heterodyne detection device, as well as a surface shape measuring device and a coherent laser radar using the optical heterodyne detection device.

[Conventional technology]

Conventional optical heterodyne detection devices do not consider measuring the two-dimensional distribution of amplitude, phase, and frequency of detected light. For example, Japanese Patent Application Laid-Open No. 62-298789 discloses a heterodyne receiver for laser radar. However, this heterodyne receiver inputs the entire detected light into a photodetector, and the S/N is reduced due to differences in amplitude or frequency of each part of the detected light.
It is only an attempt to suppress the decline in the ratio, therefore,
In order to measure the distribution within the detected light using conventional equipment, it is necessary to make the photodetector smaller than the detected light and either mechanically scan the photodetector or use an array of photodetectors. .

[Problem to be solved by the invention]

However, when the photodetector is made smaller than the detection light and the photodetector is mechanically scanned, scanning time is required for mechanical scanning, and high-speed scanning is impossible. When using detectors, there was a problem of crosstalk between adjacent arrayed detectors.

An object of the present invention is to provide an optical heterodyne detection device that can measure at least one two-dimensional distribution of amplitude, phase, and frequency of detection light.

Another object of the present invention is to provide a laser projection device suitable for use in the optical heterodyne detection device.

A further object of the present invention is to provide a surface profile measuring device and a laser radar using the optical heterodyne detection device.

[Means to solve the problem]

The above object is an optical heterodyne detection device that receives a laser beam and measures at least one of its amplitude, phase, and frequency. means, a laser generating means for generating a laser beam having a frequency different from that of the laser beam as the detection light, and a beam for converting the beam diameter of the laser beam obtained by the laser generating means;
a diameter converting means; and a laser beam whose beam diameter has been converted by the beam diameter converting means is simultaneously input as a reference beam to an arbitrary point on the light receiving surface of the photodetector from the same direction as the laser beam serving as the detection light. at least one of the amplitude, phase and frequency of the output signal of the photodetector;
This is achieved by an optical heterodyne detection device characterized by having a detection means for detecting one.

The above object also provides a laser projection device for projecting a laser beam onto a flat surface, which includes a laser generator, a polygon mirror that reflects the laser beam output from the laser generator, and at least one of the laser generator and the polygon mirror. This is achieved by a laser projection device characterized in that it has means for changing the inclination of the image.

The above object also provides a laser radar that detects the position of an object by transmitting a laser beam into space and receiving a reflected wave from an object existing in space. a first calculating means for calculating the position of the object from the direction of the optical axis of the optical system in the reflected wave from the object received by the device and the position of the laser beam as the reference light on the light-receiving surface of the photodetector; This is achieved by a laser radar characterized in that it has a second calculation means for calculating the moving speed of the object from the frequency of the reflected wave obtained from the optical heterodyne detection device.

Furthermore, the above-mentioned object is a surface shape measuring device that irradiates a laser beam onto the surface of a test object and measures the surface shape of the test object using the reflected wave thereof; The optical heterodyne detection device receives the reflected wave from the surface of the specimen as the detection light, and the shape of the surface of the specimen is calculated based on the phase distribution of the reflected wave from the surface of the specimen detected by the optical heterodyne detection device. This is achieved by a surface profile measuring device characterized by having a calculation means.

[Effect]

Generally, in an optical heterodyne detection device, a beat signal is detected from the photodetector by inputting detection light and reference light in an overlapping manner onto the light-receiving surface of the photodetector. In an optical heterodyne detection device, if the reference light is superimposed only on a specific location of the detection light, the resulting beat signal will be affected only by the detection light present at that location.
Therefore, we focused on the fact that by scanning the reference light, it is possible to measure the two-dimensional distribution of the amplitude, phase, and frequency of the detection light.

The optical heterodyne detection device of the present invention is based on the above findings. That is, the first and second
The laser beam serving as the detection light and the laser beam serving as the reference light are input in an overlapping manner by the input means, and the beat signal generated by the overlap of both is detected as the output signal of the photodetector.2 Therefore, the beam diameter converting means , the beam diameter of the laser beam as the reference light is converted to a beam diameter smaller than the beam diameter of the laser beam as the detection light, and the second input means converts the laser beam as the reference light at a predetermined period. By scanning the light receiving surface of the photodetector, the amplitude of the laser beam as the detection light,
A two-dimensional distribution of at least one of phase and frequency can be measured.

Further, in the laser projection apparatus of the present invention, by using a polygon mirror, the laser beam serving as the reference light can be scanned at high speed.

Furthermore, in the laser radar of the present invention, by using the optical heterodyne detection device, the position and moving speed of the object can be detected, and the reference light can be tracked to the position of the object on the light receiving surface of the detector. By moving it, it is also possible to track a moving object.

Furthermore, in the surface shape measuring device of the present invention, by measuring the two-dimensional distribution of the phase of the reflected wave using the optical heterodyne detection device, it is possible to measure the surface shape of a wide area of the specimen by measuring -degrees. can do.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, the optical heterotine detection device of this embodiment includes a beam splitter 2 through which the detection light 1 passes, a photodetector 3 into which the detection light 1 that has passed through the beam splitter 2 is incident, and a detection light A laser generator 4 that generates a laser beam with a frequency different from 1 and the laser beam generated by the laser generator 4 are input, and the beam diameter is converted to a beam diameter smaller than that of the detection beam 1, and the reference beam 5 is It has a beam diameter converter 6 that produces a beam diameter converter 6, and a beam scanning section 7 that inputs and scans the reference light 5 produced by the beam diameter converter 6.The reference light 5 scanned by the beam scanning section 7 is sent to a beam splitter. 2, the direction of the detection light 1 is changed and the light is incident on an arbitrary point (x, y) on the light receiving surface -E of the photodetector 3 from the same direction as the detection light 1. FIG. 2 shows the positional relationship between the detection light 1 and the reference light 4 that are incident on the light receiving surface of the photodetector 3. The reference light 5 is scanned by the beam scanning section 7 with respect to the detection light 1 along a beam scanning path 9. be done. The output signal from the photodetector 3 is input to the detection circuit 8. The output signal from the photodetector 3 includes a beat signal as described later, and by detecting this with the detection circuit 8, the amplitude U o (x, y), frequency ωofx, y), and phase φ of the detected light 1 are determined.
O(X, Z) is obtained.

Next, the operation of this embodiment configured as described above will be explained. First, the heterodyne detection method, which is the theoretical background of the heterodyne detection device, will be explained using FIG. In the figure, members equivalent to those shown in FIG. 1 are given the same reference numerals. The detected light 1 at the time [at the point fx, y) on the light receiving surface of the photodetector 3 is defined as Uo (x, y, t), and the reference light 5
Let U r (t) be the detection light Uo (x, y, t) and the reference light Ur (t), respectively, expressed by the following equations.

U o (x, y, t) = U o (x, y) −ex
p(jfωo(x, y) is called φo(x, y)]) ・
...(1) Ur(t) = Urexp(j[ωrt+
φrl) − (2) where UO(X, V), φo(x, y), ωo(x, y):
Amplitude, phase and frequency of detection light 1 at point (x, y) Ur, φ", ω": Amplitude, phase and frequency of reference light 5 From the above formula, light for area A where reference light 5 and detection light 1 overlap The output of detector 3 is as follows.

= Ur 2 + Uo 2 (x, y) + 2
Ur tJo(x,y)-cos([ωr-ωo(x
, y)It+φ"-φo(x,y))...]3) As can be seen from the above equation, the photodetector 3 outputs the frequency [ωr
−ωO(X, V)] is obtained. Reference light 5
Since the amplitude Ur, frequency ωr, and phase φr are known,
By detecting the above beat signal, the vibration of detection light 1 @
Uo(x,y), phase φo(x,y), frequency ωo(x
, y) can be detected.

On the other hand, the photodetector 3 for area B where only the detection light 1
The output of is expressed by the following equation.

I B (x, '/, t) = lUo (x, y, t) 12
= Uo' (x, y, t) - (4) As can be seen from the above equation, the amplitude of detection light 1 is UO[X.

Only y and tl can be detected. Heterodyne detection method detects the beat signal expressed by equation (3),
Compared to the direct detection method expressed by equation (4), frequency and phase can be detected. Furthermore, in the heterodyne detection method, by increasing the amplitude Uo of the reference beam 5, the amplitude of the target signal can be increased, so compared to the direct detection method, the sensitivity is 102 to 1
04 times as high as about 10 is possible.

The optical heterodyne detection device of this embodiment is based on the above principle, and detects the beat signal included in the output signal of the photodetector 3 using the detection port #I8, thereby increasing the amplitude Uo of the detected light 1.
(x, y), frequency ωofX, V), phase φO(X, Z
).

In this embodiment, the two-dimensional signal distribution of the detection light 1 can be measured by further scanning the reference light 5 along the path 9 as shown in FIG. 2 in the beam scanning section 7. can. That is, the reference light 5 is transmitted to the beam scanning section 7.
The point (x,
y) from the beam scanning unit 7 as a position signal and measure the output of the detection circuit 8 at that time, the position (X, V
), the amplitude Uofx, y) and the frequency ωo of the detection light 1 at
(x, y) and phase φo(:x, y) are obtained. Here, in order to detect the above information with the detection circuit 8, the amplitude Uo(x,
y), by square-law detection of the input signal (beat signal) and dividing by the amplitude U of the reference light, an output proportional to UO(X, V) is obtained, and the frequency ωo( x, y), the beat signal frequency [ω'' is detected by frequency detection.
-ωO(X, V)] is detected, and since ωr is known, ω0(x.

y) can be detected, and to detect the phase φo(x, y), φo(x, y) can be obtained by detecting a signal having the same frequency as the beat signal and a phase φr using phase detection.

As described above, according to this practical example, only by scanning the reference light 5, without arranging the photodetectors 3 in an array or mechanically scanning the photodetectors 3, two of the detection lights 1 can be used. Can measure dimensional distribution. Further, by reducing the beam diameter of the reference light 5, the positional resolution can also be improved.

By the way, in the above-mentioned embodiment, the detection circuit 8 requires three types of detection means: square-law detection, frequency detection, and phase detection, but only specific information on the amplitude, frequency, and phase of the detection light 1 can be detected. If necessary, a detection circuit using only the corresponding detection means may be configured.

Next, one embodiment of the beam diameter converter 6 will be described using FIG. 4. As shown in FIG. 4, the beam converter 6 is
The output beam diameter is changed by a combination of a lens 6a for expanding a parallel input beam and a lens 6b for making the expanded beam parallel. The output beam diameter with respect to the input beam can be changed by the refractive index of the lenses 6a and 6b and the distance Wx of the lenses 6a and 6b.
Lens 6a to suppress wavefront aberration of the output beam.

It is preferable to insert a lens between 6b and 6b.

The beam diameter converter can also be realized with the configuration shown in FIG. That is, in FIG. 5, the beam diameter converter 6A has two convex lenses 6c and 6d placed at two points on the optical axis.
It is constructed by placing an aperture 6e at the focal point of point c. The input beam is focused by a convex lens 6C! A, the beam enters the convex lens 6d, and the convex lens 6d outputs a parallel beam having a beam diameter different from that of the input beam. In this embodiment as well, the output beam diameter can be changed by changing the refractive index of the lenses 6c and 6d and the distance x between the aperture 6e and the convex lens 6d.

Next, an embodiment of the beam scanning section 6 will be described using FIG. 6. The beam scanning section 7 two-dimensionally scans the input reference light 5 onto a plane on the light-receiving surface of the photodetector 3. Therefore, as shown in FIG. 6, if the axes of the plane are x and y, the beam operating unit 7 includes a mirror 7a and a motor 7b for moving the beam in the X-axis direction, and a motor 7b for moving the beam in the y-axis direction. mirror 7c, motor 7d"C"
By arranging these mirrors and motors along the optical axis of the input beam, the input beam, that is, the reference light 5, can be scanned two-dimensionally.

Further, the beam operating section can also be constructed using a polygon mirror 7e as shown in FIG.

That is, when the polygon mirror 7e is rotated at an angular velocity ω, the input beam can be deflected at twice the angular velocity. Therefore, the beam operating section 7A arranges the polygon mirror 7e and the motor 7f so that this deflection direction coincides with the X-axis direction on the scanning plane.

Further, scanning in the y-axis direction is made possible by changing the angle of the Bolinbon mirror 7e with respect to the input beam. For this purpose, the lower end of the polygon mirror 7e is supported on a pedestal 71 by a spherical bearing 7g, and the other end is adapted to be displaced by applying a voltage to the piezo element 7h.

In this embodiment, the polygon mirror 7e was used for scanning in the X-axis direction, but there is no problem even if the x and y axes are reversed.In addition, in the above embodiment, in order to change the angle between the input beam and the polygon mirror, Although the inclination of the polygon mirror was changed, it goes without saying that this can also be achieved by changing the incident angle of the input beam.

Next, in the optical heterodyne detection device described above, the reference light 5
An example of a detection method in which measurement is performed by changing the beam diameter will be described.

In FIG. 8, if the solid angle when looking at the scatterer 10 from the photodetector 3 is ΩS, and the laser wavelength is S, then the plane of light @ A C
In the range of A2/QS, the wavefront (phase) can be considered to be -like. This area AC is called a coherence area, and needs to be taken into consideration during optical heterodyne detection. That is, if the effective light receiving area Ae of the photodetector 3 is larger than AC, there is a risk that scattered light with a different wavefront (phase) will be incident, and the S/N of the detected signal when performing heterodyne detection will decrease. .

Therefore, the effective light receiving area Ae of the photodetector 3 needs to be smaller than the area AC. However - in boat fishing, the size of the scatterer 10 is unknown at the time of detection, so the coherence area Ac is not known; this problem can be solved by the method of the invention. This will be explained below using FIG. 9. First, as shown in FIG. 9(A), the beam diameter a of the reference beam 5 is set to a=a1, and the photodetector 3 is scanned to detect a signal.

Next, as shown in FIG. 8(B), the beam diameter a is changed to a2 smaller than al, and the same scanning is performed.
As shown in C), repeat scanning with beam diameter a=a3 (a2<a3) and detecting the signal six or more times until the signal does not change at the point (X, V) on the photodetector 3. Reduce the beam diameter a.

This allows light detection with a high S/N ratio regardless of the size of the scatterer 10.

In the above embodiment, a method was described in which the beam diameter a is gradually reduced and scanned in all areas on the photodetector 3. The beam diameter a gradually increases until the detection signal changes.
The same effect can be obtained by decreasing the beam diameter a and scanning only the area where the detection signal changes by further decreasing the beam diameter a.

Next, a laser radar, which is an example of an application device using the optical heterodyne detection device of the present invention, will be explained with reference to FIG. . In FIG. 10, the laser radar 15 includes a laser generator 4a for radar laser transmission, a beam splitter 2a, transmission optical system lenses lla and llb, a heterodyne detection laser generator 4, and a beam splitter 2.
b, 2c, photodetector 3a, detection circuit 8a, mirror 14,
Beam diameter converter 6, beam scanning unit 7, light receiving lens ll
c, beam splitter 2, photodetector 3, detection circuit 8,
It consists of a data processing device 12 and a display device 13.

Next, the operation of the above laser radar will be explained in chronological order.

The laser beam output from the transmitting laser generator 4a is split by a beam splitter 2a, one of which passes through lenses lla and llb of the transmitting optical system, and a laser beam for radar is transmitted into space. The other laser beam split by the beam splitter 2a is superimposed on the photodetector 3a via the beam splitter 2b with the laser beam output from the heterogeneous detection laser 4 and passed through the beam splitter 2C. The beat signal output from the photodetector 3a is detected by the detection circuit 8a to detect the frequency. Here, the frequency of the laser beam output from the transmission laser generator 4a is ω■, the frequency of the laser beam output from the heterodyne detection laser generator 4 is ω, O
Then, the frequency ωS detected by the detection circuit 8a is ω
S=ω〇−ω■.

The radar laser beam transmitted into space is the object 16
The light is reflected by the receiving lens llc and condensed by the receiving lens llc. This light corresponds to the detection light 1 in the embodiment described above. A laser beam for heterodyne detection from a laser generator 4 is inputted to a beam diameter converter 6 via a beam splitter 20 and a mirror 14, and a reference beam 5 is produced. Beam diameter converter 6, beam operation unit 7, beam currant Yter 2
, the photodetector 3 and the detection circuit 8 detect the amplitude and frequency of the detection light corresponding to the position (x, y) of the reference light 5 scanned by the beam scanning unit 6, as described in the above embodiment. ,
This information and the frequency ωS detected by the detection circuit 8a
is input to the data processing device 12.

The data processing device 12 performs processing based on the following idea. First, the position of the object 16 can be detected from the optical axis direction of the light receiving lens tic and the position signal (x, y). Also, when an object moves, due to Doppler frequency shift,
The detection circuit 8 detects a frequency different from the frequency ωS detected by the detection circuit 8a, and the speed of the object is determined from the frequency difference.

Also, when the object moves in the azimuth direction, the light receiving lens
If the movement is within the field of view c, the object can be tracked by moving the reference light 5 in the beam scanning unit 6 so as to follow the point where the reflected wave from the object 16 is imaged on the photodetector 3. can be done.

As described above, according to the laser radar of this embodiment, the position and speed of a moving object can be detected, and the object can be tracked by scanning the reference light.

In the above embodiments, a case has been described in which a continuous wave is used as the transmitting laser beam, but it goes without saying that the distance to an object can be measured using a pulse wave.

Next, a surface profile measuring device which is another embodiment of the device to which the present invention is applied will be explained with reference to FIGS. 11 and 12. In FIG. A symbol is attached. In FIG. 11, the surface shape measuring device 17 includes a laser generator 8, a beam splitter 2d,
2e, 2f.

2g, 2h, frequency shifter 18, concave lens lid, convex lens lie, photodetector 3.3b, mirrors 14a, 14b
, a beam diameter converter 6, a beam scanning section 7, a detection circuit 8, a data processing device 12, and a display device 13.

Let us now assume that the wavelength of the laser output from the laser generator 4 is λ, and the frequency is ω. Test #: 19 To measure the uneven shape of the point (X, y) on the surface, it is sufficient to measure the optical path of the laser beam without reflecting it on the test object 19.0 The difference in the unevenness at each point on the surface is The surface shape measurement device 17 uses this principle to measure the shape of the surface of the specimen.

The operation of the surface shape measuring device 17 will be described below with reference to FIGS. 11 and 12. In order to accurately measure the shape of the surface of a test piece, before measuring the optical path difference (phase) of the reflected wave from the surface of the test piece, measure the distribution of the optical path difference due to the lens and beam splitter in the equipment, and perform the test. By subtracting the above distribution from the distribution of optical path differences obtained from the body, the exact shape of the specimen can be determined. Therefore, first, before measuring a single test object, an object with a known shape is placed and the phase difference at each point is measured. The procedure is described below.

The laser beam output from the laser generator 4 is split by beam splitters 2d and 2e, one of which is an optical system for irradiating a parallel beam onto the specimen, that is, a concave lens 11d.
A parallel laser beam is irradiated onto the test object 19 (an object whose shape is known) through a convex lens ie. The reflected wave passes through beam splitter 2h and beam splitter 2h.
The light passes through and is input to the photodetector 3. On the other hand, one of the laser beams split by the beam splitters 2d and 2e is inputted to the frequency shifter 14, and the frequency changes from ω to ω+ω0.
will be shifted to The frequency-shifted laser beam is further split by a beam splitter 2f, one of which is input to a beam diameter converter 6 via mirrors 14a and 14b, and a reference beam 5 is produced. The beam scanning unit 7, the photodetector 3, and the detection circuit 8 after the beam diameter converter 6 have the same behavior as shown in FIG.
The signal at each point of the reflected wave (detection light 1) inputted from the detector is detected. In this embodiment, the detection circuit 8 only needs to detect the phase, and the other of the laser beams of frequency ω+ω0 split by beam splitter 2f is the laser beam of frequency ω split by beam splitter 2e. Beam splitter 2g"C" is superimposed with the beam,
The output signal inputted to the photodetector 3b becomes a beat signal having a frequency equal to the frequency difference ω0 between both laser beams. This signal is input to the detection circuit 8 and used as a phase reference signal.The above-described operation yields a phase distribution φ8 with a known shape as shown in FIG. 12(^). The phase distribution φB shown in FIG. 12(B) is obtained. Then, in the data processing device 12, φB−φ
The phase distribution shown in FIG. 12(C) is obtained.

By outputting this to the display device 13, trial 1
Two shape results are obtained.

As described above, according to the surface shape measuring apparatus of this embodiment, it is possible to widen the width of the beam irradiated to the test object, so a wide area can be measured by -degree measurement, and the inspection time can be shortened.

In the above-described embodiment, the frequency shifter 18 was used to generate laser beams with different frequencies, but it goes without saying that the present invention can also be realized by using an Ike's laser generator instead.

〔Effect of the invention〕

As explained above, according to the optical heterodyne detection device of the present invention, it is possible to two-dimensionally measure the frequency, phase, and amplitude distribution of laser light with high sensitivity.

Further, according to the laser projection device of the present invention, the laser beam can be scanned at high speed using a polygon mirror.

Further, according to the laser radar of the present invention, the position and moving speed of an object can be detected, and the moving object can be tracked.

Furthermore, according to the surface shape measuring device of the present invention, the surface shape of a test piece over a wide area can be measured by measuring -degrees.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical heterodyne detection device according to an embodiment of the present invention, FIG. 2 is a diagram showing a scanning path of a reference light in the optical heterodyne detection device, and FIG. 3 is a diagram showing an optical heterodyne detection method. FIG. 4 is a schematic diagram showing an embodiment of the beam diameter converter used in the optical heterodyne detection device of the present invention, and FIG. FIG. 6 is a schematic diagram showing an embodiment of the beam operating section used in the optical heterodyne detection device of the present invention, and FIGS. FIG. 8 is a schematic diagram showing another embodiment of the operation unit, and FIG. 8 is a diagram showing the solid angle of the scatterer for explaining the coherence area, and FIG. 9 (^), (B
) and (C) are diagrams showing a beam scanning hand 111 in the optical heterodyne detection method of the present invention, and FIG. 10 is a schematic diagram of a laser radar according to an embodiment of the present invention.
FIG. 1 is a schematic diagram of a surface profile measuring device according to an embodiment of the present invention, and FIGS. 12(A), 12(81) and (C) show phase distributions for explaining the operation of the same surface profile measuring device. It is a diagram. Explanation of symbols 1...Detection light 2...Beam splitter (first and second input devices)
3... Photodetector 4... Laser generator 5.
...Reference light 6...Beam diameter converter 7...
・Beam operation unit (second input means) 8...detection circuit (
Detection means) 7e... Polygon mirror 7h... Piezo element (means for changing inclination) 15...
Laser radar 12...Data processing device (calculating means) Fig. 1 6--Beam diameter converter 7-Beam operation section (second input means) 7e--Polygon mirror 7h--Piezo element (changes inclination) Means) 8. Detection Oi
l path (detection means) 12- Data processing device (calculation means) 15- Laser radar applicant Hitachi, Ltd.

Claims (8)

[Claims] (1) In an optical heterodyne detection device that receives a laser beam and measures at least one of its amplitude, phase, and frequency, the first input means inputs the laser beam as detection light onto the light receiving surface of the photodetector. A laser generating means for generating a laser beam having a frequency different from that of the laser beam as the detection light, a beam diameter converting means for converting the beam diameter of the laser beam obtained by the laser generating means, and a beam diameter converting means for converting the beam diameter of the laser beam obtained by the laser generating means. a second input means for simultaneously inputting a laser beam whose beam diameter has been converted to an arbitrary point on the light receiving surface of the photodetector as a reference light from the same direction as the laser beam serving as the detection light; 1. An optical heterodyne detection device comprising: detection means for detecting at least one of the amplitude, phase, and frequency of an output signal. (2) The beam diameter converting means converts the beam diameter of the laser beam serving as the reference light so that the beam diameter becomes smaller than the beam diameter of the laser beam serving as the detection light. The optical heterodyne detection device described. (3) The second input means includes a beam scanning means for scanning the laser beam as the reference light on the light-receiving surface of the photodetector at a predetermined period, and the detection means optically detects the laser beam. 2. The optical heterodyne detection device according to claim 1, wherein the optical heterodyne detection device simultaneously detects a position on the light receiving surface of the detector and at least one of the amplitude, phase, and frequency of the output signal of the detector at this position. (4) In the optical heterodyne detection device according to claim 1, the laser beam as the reference light is scanned over the light-receiving surface of the photodetector with the beam diameter set to an arbitrary constant size, and then the beam diameter is changed to the beam diameter. An optical heterodyne characterized in that the scanning is performed with a smaller size, and the same scanning is repeated thereafter until at least one of the detected amplitude, phase, and frequency does not change in a specific area of the light receiving surface of the photodetector. Detection method. (5) A laser projection device that projects a laser beam onto a flat surface, including a laser generator, a polygon mirror that reflects the laser beam output from the laser generator, and an inclination of at least one of the laser generator and the polygon mirror. A laser projection device characterized in that it has a means for changing. (6) A laser radar that detects the position of an object by transmitting a laser beam into space and receiving a reflected wave from an object existing in space, comprising: the optical heterodyne detection device according to claim 1; A first calculating means for calculating the position of the object from the direction of the optical axis of the optical system in the reflected wave from the object received by the heterodyne detection device and the position of the laser beam as the reference light on the light-receiving surface of the photodetector. and second calculation means for calculating the moving speed of the object from the frequency of the reflected wave obtained from the optical heterodyne detection device. (7) In the laser radar according to claim 6, the laser beam as the reference light is transmitted to the light receiving surface of the photodetector within a range where the reflected wave from the moving object is input onto the light receiving surface of the photodetector. A laser radar tracking method characterized by tracking a moving object by moving it so as to follow the position of the laser radar. (8) A surface shape measuring device that irradiates a laser beam onto the surface of a test object and measures the surface shape of the test object using its reflected wave, comprising: an optical means for converting the laser beam irradiated onto the surface of the test object into a parallel beam; The optical heterodyne detection device according to claim 1, which receives reflected waves from the body surface as the detection light, and detects the surface shape of the specimen based on the phase distribution of the reflected waves from the specimen surface detected by the optical heterodyne detection device. 1. A surface shape measuring device comprising: calculation means for calculating.