JPH09211128A - Speed measuring device - Google Patents

Abstract

(57) An object of the present invention is to obtain an inexpensive velocity measuring device using a light source having a wide linewidth and capable of measuring a target velocity at an arbitrary distance with a high velocity resolution and a high S / N ratio. SOLUTION: A laser light source 1, an optical branching means 11 for branching a laser light 2 from the laser light source 1 into a transmission light 2b and a local light 2a, and a transmission light 2b are irradiated to a target 3 and then from the target 3. Transmitting / receiving optical means 10 and 12 for receiving the reflected and scattered light of the light as the signal light 2c, an optical delay means 13 for delaying the local light 2a, and the delayed local light 2a.
And a signal light 2c are combined with each other, and an optical receiving means 6 for coherently detecting the combined local light 2a and signal light 2c is provided. Measure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed measuring device,
In particular, it relates to a velocity measuring device using a coherent CW laser as a light source.

[0002]

2. Description of the Related Art FIG. 12 shows a velocity measuring device using a laser as a light source disclosed in Japanese Patent Publication No. 2-272382 by Alexander Binz. 1 is a laser which oscillates at a single wavelength, 2 is laser light emitted from laser 1, 3 is a target, 4 is a partial reflecting mirror, 5 is an optical multiplexer, 6 is a receiver for performing heterodyne detection, and 7 is an optical splitter , 8 is a total reflection mirror, 9 is a frequency shifter, and 10 is a transmission / reception optical system.

The operation will be described with reference to the drawings. A laser beam 2 emitted from a laser 1 oscillating at a single wavelength is emitted toward a target 3. The laser light 2 is partially reflected by the partial reflection mirror 4 2a.
Is branched and reaches the receiver 6 via the optical multiplexer 5 as local light. The remaining portion 2b of the laser light 2 is shifted in frequency by the frequency shifter 9 by the intermediate frequency fIF, and is transmitted through the optical branching device 7 to the target 3 by the transmitting / receiving optical system 10.
Is irradiated. Laser light 2c reflected and scattered from the target 3
Is received by the transmission / reception optical system 10, passes through the optical branching device 7, the total reflection mirror 8 and the optical multiplexer 5, and reaches the receiver 6 as signal light. The receiver 6 performs coherent detection and outputs beat signals of the signal light 2c and the local light 2a. The difference between the frequency of the beat signal and the intermediate frequency fIF is proportional to the speed of the target 3. Thus, the speed of the target 3 can be measured.

In the speed measuring device using the laser light source as described above, the time (τ _L ) required for the local light 2a to reach the receiver 6 from the laser 1 and the signal light 2c is received from the laser 1 via the target 3. Time to reach vessel 6 (τ _s )
In between, a time difference (τ _d = τ _s −τ _L ) corresponding to a round trip time (τ _rt ) occurs. for that reason,
When a light source with a spectral line width (Δf) of laser light wider than the Doppler frequency corresponding to the velocity resolution required by the device is used, the time between the signal light and the local light is increased for a long-distance target. The coherence cannot be maintained, and the velocity resolution and sufficient S / N ratio required for the device cannot be secured.

Ogoshi, Kikuchi, et al. Have shown that a semiconductor laser (hereinafter referred to as LD) is used as a light source (Coherent Optical Communication Engineering, p92-p94, Ohmsha, 198).
9), the spectrum of the beat signal is as shown in FIG. The beat signal has a small time difference with respect to a short-distance target, so that temporal coherence is maintained as shown in FIG. 13A, and the spectral line width of the beat signal becomes a line spectrum, which is necessary for the apparatus. It is possible to secure the required speed resolution and a sufficient S / N ratio. On the other hand, the temporal coherence is not maintained for a target at a long distance, and the temporally incoherent component forms a broad spectrum according to the line width of the laser light source (FIG. 13B). For a farther target, the spectral line width of the beat signal becomes a broad spectrum which is about twice the line width of the laser light as shown in FIG. 13 (C).

For example, wavelength 1.5 [μm], line width 5 [MH
When the light source of z] is used, the spectrum of the beat signal becomes a line spectrum as shown in FIG. 13A for a target at a distance of 1 to 2 [m] and 1 [cm / s] (Doppler frequency 13 [ k
It is possible to perform measurement with high speed resolution and high S / N ratio such as [Hz]). But the target distance is 25
At about [m], the spectral line width of the beat signal becomes exponentially smaller as shown in FIG. 13B, and the S / N ratio deteriorates in proportion thereto. Further, when the target distance exceeds 50 [m], the spectral line width of the beat signal becomes a broad spectrum with a line width of 10 [MHz] as shown in FIG.
s] (Doppler frequency 13 [kHz]) is not possible.

As described above, since the speed resolution required for the apparatus cannot be satisfied and the S / N ratio is deteriorated, a speed measuring apparatus using a conventional laser light source has, for example, a DFB (distribution feed back). A light source such as -LD, which is inexpensive but has a wide line width of several [MHz], can be used only for short-distance measurement. For a target at a long distance, it is necessary to use an expensive light source such as a solid-state laser (line width: several [kHz]) that oscillates with a narrow line width and a single wavelength.

[0008]

As described above, in the velocity measuring device using the laser light source, when the light source having a relatively wide spectral line width of the laser light is used, the signal light is not used for the target at a long distance. The temporal coherence is not maintained between the local lights, and the spectral line width of the beat signal is about twice the line width of the laser light. Therefore, there are problems that the velocity resolution required for the device cannot be satisfied and that the S / N ratio deteriorates.

The present invention solves the above-mentioned drawbacks, and obtains a velocity measuring device which is inexpensive and can measure the velocity of a target at a long distance with a high velocity resolution and a high S / N ratio by using a light source having a wide line width. The purpose is to

[0010]

A velocity measuring device according to the present invention includes a laser light source, an optical branching unit for branching a laser beam from the laser light source into a transmission light and a local light, and a target for the transmission light. Then, reflected from the target, transmission and reception optical means for receiving scattered light as signal light, optical delay means for delaying the local light, optical combining means for combining the delayed local light and the signal light, An optical receiving unit for coherently detecting the combined local light and signal light is provided, and the target velocity is measured by the output of the optical receiving unit.

Further, in the speed measuring device according to the present invention,
The transmission / reception optical means consists of an optical path switching optical system and a transmission / reception optical system.The transmission / reception optical system irradiates the target with transmission light through the optical path switching optical system, and the reflected / scattered light from the target is received by the transmission / reception optical system to switch the optical path. Through the optical system, the signal light is switched to an optical path different from the optical path of the transmission light and guided to the optical multiplexing means.

Further, in the speed measuring device according to the present invention,
The transmission / reception optical means is provided with a transmission optical system for irradiating the target with the transmission light, and a reception optical system for receiving the reflected / scattered light from the target and guiding it as signal light to the optical combining means.

Further, in the speed measuring device according to the present invention,
The optical delay means is made of a long optical fiber and allows local light to pass through the optical fiber to delay the local light.

Further, in the speed measuring device according to the present invention,
The optical delay means is composed of two or more reflecting mirrors and reflects the local light between the reflecting mirrors to delay the local light.

Further, in the speed measuring device according to the present invention,
The optical delay means includes a plurality of optical delay elements that delay the local light with different delay times, and an optical delay element switching means that selects only one optical delay element through which the local light passes among the plurality of optical delay elements. And delays the local light by various delay times by controlling the optical delay element switching means.

Further, in the speed measuring device according to the present invention,
The plurality of optical delay elements are composed of a plurality of optical fibers having different lengths, and the optical delay element switching means is a mechanical optical switch,
Alternatively, it comprises a non-mechanical optical switch that combines any one or more of an electro-optical effect, an acousto-optical effect, and a Faraday effect.

Further, in the speed measuring device according to the present invention,
The plurality of optical delay elements are composed of a plurality of movable reflecting mirrors, and the optical delay element switching means is composed of a reflecting mirror control means for controlling the angles or positions of the plurality of movable reflecting mirrors.

Further, in the speed measuring device according to the present invention,
It is provided with an autofocus mechanism that adjusts the focal point of the transmission / reception optical system and a switching control unit that controls the optical delay element switching unit according to the focus data obtained from the autofocus mechanism.

Further, in the speed measuring device according to the present invention,
The transmission light is focused substantially on the target by controlling the autofocus mechanism, and the data from the autofocus mechanism when the focus is focused is used to control the optical delay element switching means to delay the optical delay means. The time is selected and the target speed is measured by the output of the light receiving means.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 and 2 in which parts corresponding to those in FIG. 11 are assigned the same reference numerals show Embodiment 1 of the speed measuring device according to the present invention, in which 11 is a first optical coupler for branching a laser beam 2, 12 Is an optical circulator, 13 is an optical delay line that delays the local light 2a for a predetermined time, and 14 is a second optical coupler that combines the local light 2a and the signal light 2c.
Each element in the device is coupled by an optical fiber. Further, in FIG. 2, reference numeral 100 is a transmission optical system, and 101 is a reception optical system. 1 shows an embodiment using a transmission / reception optical system 10 in which the optical transmission means and the optical reception means are coaxially configured in one optical system, and FIG. 2 shows the optical transmission means and the optical reception means respectively. This is an embodiment in which the optical system 100 and the optical receiving optical system 101 are biaxial, and the spectroscopic circulator 12 is omitted.

Next, the operation will be described with reference to FIG. The laser light 2 from the laser light source 1 which oscillates at a single wavelength propagates in the optical fiber and is branched by the first optical coupler 11 into local light 2a and transmission light 2b at an arbitrary branching ratio. The transmitted light 2b is emitted from the transmission / reception optical system 10 to the target 3 via the optical circulator 12. The transmitted light 2b with which the target 3 is irradiated is reflected and scattered by the target 3, and a part thereof is received by the transmission / reception optical system 10. The reflected and scattered light thus received propagates again in the optical fiber as the signal light 2c and is guided to the second optical coupler 14 via the optical circulator 12. On the other hand, the local light 2a is the optical delay line 1
3 and is input to the second optical coupler 14. The local light 2a and the signal light 2c are combined by the second optical coupler 14 and coherently detected by the receiver 6.
As a result, the receiver 6 outputs a beat signal having a Doppler frequency proportional to the speed of the target 3.

Here, the delay time (Δτ) by the optical delay line 13 is the time (τ _L ) required for the local light 2a to reach the receiver 6 from the laser light source 1, and the signal light 2c is the laser light source 1 from the laser light source 1. When it is set to be equal to or close to the time (τ _s ) required to reach the receiver 6 via the target 3, temporal coherence can be obtained between the local light 2a and the signal light 2c. Therefore, even if a light source with a wide line width such as DFB-LD is used, the spectrum of the beat signal between the local light 2a and the signal light 2c is as shown in FIG.
The line spectrum is obtained as described above. Thereby, the speed of the target 3 can be measured with high speed resolution and high S / N ratio. Conversely, when the delay time Δτ of the local light 2b by the optical delay line 13 is determined, as shown in the following formula (1), for the signal light from the target near the distance R,
It can be measured with high velocity resolution and high S / N ratio.

R = (τ _L0 + Δτ−τ _s0 ) · c / 2 (1) (where τ _L0 = τ _L −Δτ, τ _s0 = τ _s −τ _rt , τ _rt :
Round trip time, c: speed of light)

For example, the wavelength of the light source is 1.5 μm and the line width is 5
In the velocity measuring device with [MHz] and τ _L0 = τ _s0 , the spectrum line width of the beat signal is as shown in FIG. 13 (C) for the target of the distance 50 [m] without the optical delay line 13. A broad spectrum with a line width of 10 [MHz] is obtained.
However, about 30 which corresponds to τ _rt in the optical path of the local light 2a
When the optical delay line 13 of [μs] is provided, the spectrum of the beat signal becomes a line spectrum as shown in FIG. 13A, and it is possible to measure with high speed resolution and high S / N ratio.

FIG. 2 shows an example in which a biaxial optical system is used for transmitting and receiving light by separate optical systems. The transmission light 2b is emitted from the transmission optical system 100 to the target 3. The transmission light with which the target 3 is irradiated is reflected and scattered by the target 3, and a part thereof is received by the reception optical system 101. The reflected and scattered light thus received propagates again in the optical fiber as the signal light 2c and is directly guided to the second optical coupler 14.
Other operations and the effects obtained as a result are similar to those of the speed measuring device described above with reference to FIG.

Embodiment 2 FIG. FIG. 3 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals shows a second embodiment of the speed measuring device according to the present invention, in which reference numeral 15 is an optical fiber for time delay. The operating principle is the same as in the first embodiment described above. The optical delay line is composed of an optical fiber 15 inserted between the first optical coupler 11 and the second optical coupler 14. The delay time Δτ due to the optical fiber 15 is expressed by the following equation (2).

Δτ = n · l _f / c (2) (where n is the refractive index of the optical fiber 15 and l _{f is} the length of the optical fiber 15)

By selecting the length of the optical fiber 15, for the signal light from the target near an arbitrary distance,
Since the temporal coherence with the local light 2a can be obtained, the target velocity can be measured with high velocity resolution and high S / N ratio even if a light source having a wide line width such as DFB-LD is used. . The optical fiber 15 is easy to handle and can be wound on a bobbin of about 60 [mmφ], so that an optical delay line for light can be constructed in a small size.

Embodiment 3 FIG. 4 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals shows a third embodiment of the speed measuring device according to the present invention, in which 16a, 16b, 16c and 16d are shown.
Is a total reflection mirror that constitutes an optical delay line. The operation will be described with reference to FIG. Laser light 2 emitted from a laser light source 1 oscillating at a single wavelength is emitted toward a target 3. A part of the laser light 2 is branched by the partial reflection mirror 4, and enters the total reflection mirror 16a as local light 2a through the total reflection mirror 8. The local light 2a is reflected by the total reflection mirrors 16a, 16b, 16
Δτ after passing through the optical delay line composed of c and 16d
Receive a time delay. The local light 2a emitted from the total reflection mirror 16d reaches the receiver 6 via the optical multiplexer 5. The remaining portion of the laser light 2 is irradiated onto the target 3 by the transmission / reception optical system 10 via the optical branching device 7 as the transmission light 2b. The transmitted light reflected and scattered from the target 3 is received by the transmission / reception optical system 10, passes through the optical branching device 7, the total reflection mirror 8, and the optical multiplexer 5,
The signal light 2c reaches the receiver 6. The receiver 6 performs coherent detection.

The principle of measuring the speed of the target 3 is the same as in the above-described first and second embodiments. In the case of the third embodiment, total reflection mirrors 16a, 16b, 16c, which constitute the optical delay line,
The delay time can be arbitrarily selected by adjusting the distance between 16d. Therefore, with this configuration, the DFB-
Even if a light source having a wide line width such as an LD is used, the target velocity can be measured with high velocity resolution and high S / N ratio. The optical delay line composed of a plurality of total reflection mirrors may be configured as shown in FIG. 5 in which the same parts as those in FIG. In this case, the local light 2a incident from the total reflection mirror 16a is reflected multiple times between the total reflection mirrors 16b and 16c,
The light is emitted from the total reflection mirror 16d. Total reflection mirrors 16b, 16c
The optical delay line can be downsized as a whole by reflecting the light a plurality of times.

Embodiment 4 FIG. FIG. 6 in which parts corresponding to those in FIG. 1 are designated by the same reference numerals shows a fourth embodiment of the speed measuring device according to the present invention, in which 17a and 17b are optical delay line switching mechanisms, 18 ₁ , 18 ₂ , .., 18 _n are optical fibers serving as optical delay lines having different lengths. The optical fibers for optical delay line 18 ₁ , 18 ₂ , ..., 18 _n are
One end is connected to the optical delay line switching mechanism 17a, and the other end is connected to the optical delay line switching mechanism 17b.

Next, description will be made with reference to FIG. The laser light 2 from the laser light source 1 that oscillates at a single wavelength propagates in the optical fiber and is branched by the first optical coupler 11 into local light 2a and transmission light 2b at an arbitrary branching ratio. The transmitted light 2b is emitted from the transmission / reception optical system 10 to the target 3 via the optical circulator 12. The transmitted light with which the target 3 is irradiated is reflected and scattered by the target 3, and a part of the light is transmitted and received by the transmitting and receiving optical system 1.
Received by 0. The reflected and scattered light thus received propagates again in the optical fiber as the signal light 2c and is guided to the second optical coupler 14 via the optical circulator 12. On the other hand, the local light 2a is transmitted by the optical delay line switching mechanism 17
Optical fiber 1 for optical delay line selected by a and 17b
8 ₁ , 18 ₂ , ..., 18 _n arbitrary optical fibers 18 _i
And is guided to the second optical coupler 14. The local light 2a and the signal light 2c are combined by the second optical coupler 14 and coherently detected by the receiver 6. The receiver 6 outputs a beat signal having a Doppler frequency proportional to the speed of the target 3.

Optical fibers for optical delay line 18 ₁ , 18 ₂ ,
.., 18 _n have different lengths, so that the delay time is different. Each has the temporal coherence of the local light with respect to the signal light from the target 3 in the vicinity of the distance R _i (i = 1, 2, ..., N) within the desired measurement distance range, and the speed of the target 3 can be obtained. It can be measured with high velocity resolution and high S / N ratio. The optical fiber 18 for time delay is provided by the optical delay line switching mechanisms 17a and 17b.
By selecting an optical fiber 18 _i having an appropriate delay time according to the distance of the target 3 from ₁ , 18 ₂ , ..., 18 _n , the target speed within the desired measurement distance range as a whole can be set to a high speed resolution. And high S / N ratio.

Embodiment 5. FIG. 7 shows a configuration of an optical delay line switching mechanism of a speed measuring device as a fifth embodiment of the speed measuring device according to the present invention. In the figure, 19 is the local light 2a
Is an input optical fiber, 20 is an output optical fiber of the local light 2a, and 21a and 21b are first optical fiber connectors for coupling the input optical fiber 19 and an arbitrary optical delay line fiber 18 _i , Reference numerals 22a and 22b are second optical fiber connectors for coupling the output optical fiber 20 and an arbitrary optical delay line fiber 18 _i .

The principle of operation of the speed measuring device as a whole is as follows.
This is the same as the speed measuring device according to the fourth embodiment described above. That is, the first optical fiber connectors 21a and 21b and the second optical fiber connectors 22a and 22b are always connected to the same optical delay line fiber 18 _i and the input optical fiber 19 respectively.
Also, the output optical fiber 20 and the output optical fiber 20 are interlocked so as to be coupled. Therefore, the first optical fiber connectors 21a and 21b and the second optical fiber connectors 22a and 22b are operated so as to couple the optical delay line fibers 18 _i suitable for the target distance or the distance to be measured.
This makes it possible to measure a target speed in a desired measurement distance range with a high speed resolution and a high S / N ratio with a simple configuration.

Sixth Embodiment FIG. 8 shows a configuration of an optical delay line switching mechanism of a speed measuring device as a sixth embodiment of the speed measuring device according to the present invention. In the figure, 23 and 24 are first and second optical switches, and 25 is a delay time control circuit for controlling the first and second optical switches. The operation principle of the speed measuring device as a whole is the same as that of the speed measuring device of the fourth embodiment described above. That is, the input optical fiber 19 is connected to the input port of the first optical switch 23 and the output optical fiber 20 is connected.
Is coupled to the output port of the second optical switch 24.

Both ends of the time delay optical fibers 18 ₁ and 18 ₂ are respectively coupled to the output port of the first optical switch 23 and the input port of the second optical switch 24. The first and second optical switches 23 and 24 are controlled by the delay time control circuit 25 so that the local light 2a always passes from the input optical fiber 19 to the output optical fiber 20. The delay time control circuit 25 uses a fiber for optical delay line suitable for the target distance or the distance to be measured as the local light 2a.
So as to pass through the first and second optical switches 23, 24
Operate. This makes it possible to measure a target speed in a desired measurement distance range with a high speed resolution and a high S / N ratio with a simple configuration.

Such optical switches 23 and 24 are provided with Li
A waveguide type optical switch using the electro-optical effect formed on the NbO ₃ substrate, an optical switch using the Faraday effect including a Faraday rotator and a polarizer, and the like can be used. Further, in FIG. 8, a 1 × 2 optical switch is used, but 1 × n
Alternatively, n optical fibers for time delay may be used.

Embodiment 7. FIG. 9 in which parts corresponding to those in FIG. 4 are assigned the same reference numerals shows a seventh embodiment of the speed measuring device according to the present invention. In the figure, 26a and 26b are optical delay line switching mechanisms, and 27, 28, 29 and 30 are first, second, third and fourth total reflection mirrors which constitute the optical delay line. The operation will be described with reference to FIG. Laser light 2 emitted from a laser light source 1 oscillating at a single wavelength is emitted toward a target 3. Laser light 2
Part of the light is split by the partial reflection mirror 4 and enters the first total reflection mirror 27 as local light 2a via the total reflection mirror 8. The local light 2a is reflected by the total reflection mirrors 27, 28, 2
It is time-delayed by passing through the optical delay line constituted by 9 and 30. Local light 2a emitted from the total reflection mirror 30
Passes through the optical multiplexer 5 and reaches the receiver 6. The remaining portion of the laser light 2 is irradiated onto the target 3 by the transmission / reception optical system 10 via the optical branching device 7 as the transmission light 2b. The laser light reflected and scattered from the target 3 is received by the transmission / reception optical system 10,
After passing through the optical splitter 7, the total reflection mirror 8 and the optical multiplexer 5, the signal light 2
Reach the receiver 6 as c. The receiver 6 performs coherent detection.

The measurement of the speed of the target 3 is the same as that of the third embodiment described above. Second total reflection mirror 2 constituting an optical delay line
8, the third total reflection mirror 29, the optical delay line switching mechanism 26a,
The delay time can be arbitrarily selected by moving it to an arbitrary position by 26b. The second total reflection mirror 28,
When the third total reflection mirror 29 is selected at the positions 28 ₁ and 29 ₁ , the delay time corresponding to the shortest distance in the desired measurement distance range is set to 28 _n and 29 _n , and the desired measurement distance is set. The delay time should be set according to the longest distance in the range. As a result, it is possible to measure the target velocity within the desired measurement distance range with high velocity resolution and high S / N ratio.

Embodiment 8 FIG. FIG. 10 shows a configuration of an optical delay line switching mechanism of a speed measuring device as an eighth embodiment of the speed measuring device according to the present invention. In the figure, 31 is the local light that passes through the optical delay line, 32 is the first movable total reflection mirror,
Reference numerals 33 and 34 denote first and second total reflection mirrors, and 35 denotes a second movable total reflection mirror. The principle of operation is the same as in the fourth embodiment. The local light 31 passing through the optical delay line is reflected by the first movable total reflection mirror 32 into the first and second total reflection mirrors 33 and 34.
Is input to the two movable total reflection mirrors 35 and 34, and is finally output by the second movable total reflection mirror 35. By moving the angle and position of the first movable total reflection mirror 32 and the second movable total reflection mirror 35, the total reflection of the local light 31 between the first and second total reflection mirrors 33 and 34 can be achieved. The number of times can be adjusted. However, the first movable total reflection mirror 32 and the second movable mirror 32 are arranged so that the local light 31 passing through the optical delay line is always multiplexed with the signal light 2c by the optical multiplexer 5 and heterodyne detected by the receiver 6. The angle and position of the expression total reflection mirror 35 is moved.

From the above, the first and second total reflection mirrors 33,
34, the first movable total reflection mirror 32, and the second movable total reflection mirror 35, the delay time of the optical delay line can be arbitrarily selected. Thus, the target velocity in the desired measurement distance range can be measured with high velocity resolution and high S / N ratio. Further, although the first and second reflecting mirrors 33 and 34 are fixed in the eighth embodiment, the first and second reflecting mirrors 33 and 34 may also be moved together.
In this case, the same effect can be obtained and the delay time can be greatly changed.

Ninth Embodiment FIG. 11 in which parts corresponding to those in FIG. 6 are assigned the same reference numerals shows a ninth embodiment of the speed measuring device according to the present invention. In the figure, 36 is an autofocus mechanism for adjusting the focal point distance of the transmission / reception optical system, and 37 is an optical delay line switching adjustment device.

Next, description will be made with reference to the drawings. The laser light 2 from the laser light source 1 that oscillates at a single wavelength propagates in the optical fiber and is branched by the first optical coupler 11 into local light 2a and transmission light 2b at an arbitrary branching ratio. The transmitted light 2 b is transmitted from the transmission / reception optical system 10 to the target 3 via the optical circulator 12.
Is irradiated against. The autofocus mechanism 36 adjusts the focus of the transmission / reception optical system 10 so that the transmission light from the transmission / reception optical system 10 takes a condensing point in the vicinity of the target 3 distance. The transmission light with which the target 3 is irradiated is reflected and scattered by the target 3, and a part thereof is received by the transmission / reception optical system 10.

As a result, the received reflected and scattered light propagates again in the optical fiber as the signal light 2c and is guided to the second optical coupler 14 via the optical circulator 12.
On the other hand, the local light 2a is the optical delay line switching mechanism 17a, 1
Optical fiber group 1 for optical delay line selected by 7b
8 ₁ , 18 ₂ , ..., 18 _n arbitrary optical fibers 18 _i
And is input to the second optical coupler 14. The optical fiber 18 _i selected at this time is the autofocus mechanism 36.
It is determined in the optical delay line switching adjustment mechanism 37 using the distance information of the target 3 obtained from The local light 2a and the signal light 2c are combined by the second optical coupler 14 and coherently detected by the receiver 6. The receiver 6 outputs a beat signal having a Doppler frequency proportional to the speed of the target 3.

A laser oscillating at a single wavelength is used as a light source,
It has been known that the highest coherent detection efficiency can be obtained when the focus of the transmission / reception optical system is adjusted so that the transmission light is focused on the target in the velocity measuring device that measures the target velocity by the coherent detection. Therefore, the transmission / reception optical system 10 is controlled by the autofocus mechanism 36.
Highly efficient measurement is performed by condensing the transmission light from the target 3 in the vicinity of the distance of the target 3. Further, the distance information of the target 3 can be obtained from the focus adjustment amount at this time.

In this case, the procedure for speed measurement is as follows. (1) The autofocus mechanism 36 adjusts the focus of the transmission / reception optical system so that the transmission light 2b from the transmission / reception optical system 10 takes a focal point in the vicinity of the target 3 distance. (2)
The optical delay line 18 _i having the most suitable delay time is selected from the distance information of the target 3 obtained from the focus adjustment amount. (3) The velocity of the target 3 is calculated from the beat signals of the signal light 2c and the local light 2a output from the receiver 6.
With the above configuration and procedure, using a laser light source with a wide line width, you can quickly set the target speed in the desired measurement distance range,
It can be measured with high velocity resolution and high S / N ratio.

Embodiment 10 FIG. Although the second to ninth embodiments described above show examples in which coaxial transmitting / receiving optical systems are used for the transmitting means and the receiving means of the laser light,
A biaxial optical system including a transmission optical system 100 and a reception optical system 101 may be used as in the first embodiment described above with reference to FIG. Also in that case, the same operation principle and effect as those of the above-described second to ninth embodiments can be obtained.

In the first, second, fourth, fifth, sixth and ninth embodiments, the means for sending the transmitted light 2b from the first optical coupler 11 to the transmission / reception optical system 10 and the transmission / reception optical system 10 to the second optical coupler. Although the optical circulator 12 is used as means for sending the signal light 2c to the optical disc 14, instead of the optical circulator 12,
Even if an optical branching device such as an optical coupler that performs the same function is used,
The same effects as those of the above-described first, second, fourth to sixth and ninth embodiments can be obtained.

Further, although the total reflection mirror is used as the reflection mirror in the above-mentioned third, seventh, and eighth embodiments, the above-described embodiment can be realized even if a reflection mirror having an arbitrary reflectance is used instead of the total reflection mirror. It is possible to obtain the same effects as those of the forms 3, 7, and 8.

[0051]

As described above, according to the present invention, the laser light from the laser light source is split into the transmission light and the local light,
The transmitted light is irradiated to the target, the reflected and scattered light from the target is received as the signal light, the other local light is delayed and combined with the signal light to perform coherent detection. Accordingly, it is possible to realize a speed measuring device capable of measuring a target speed at an arbitrary distance with a high speed resolution and a high S / N ratio even if a laser light source having a wide spectral line width of laser light is used.

Further, according to the next invention, the transmission / reception optical means is composed of the optical path switching optical system and the transmission / reception optical system, and the transmission light is irradiated to the target from the transmission / reception optical system through the optical path switching optical system and reflected from the target. The scattered light is received by the transmission / reception optical system, and through the optical path switching optical system, the signal light is switched to an optical path different from the optical path of the transmission light and guided to the optical combining means, so that the transmission light and the signal light are coaxial on the transmission / reception optical means. With a configuration that can be processed with a laser beam source having a wide spectral line width of the laser beam, it has a high speed resolution and a high S / N ratio. It is possible to realize a speed measuring device that can measure with.

Further, according to the next invention, a transmission optical system for irradiating the transmission / reception optical means to the target with the transmission light, and a reception optical system for receiving the reflected / scattered light from the target and guiding it as signal light to the optical multiplexing means. With this configuration, the optical path switching optical system becomes unnecessary, and the target configuration at an arbitrary distance can be provided with high speed resolution and high speed resolution with a simple configuration. A speed measuring device capable of measuring with a high S / N ratio can be realized.

Further, according to the next invention, the optical delay means is formed of a long optical fiber, and local light is allowed to pass through the optical fiber to delay the local light. Even if a laser light source having a wide spectral line width of laser light is used to measure a target speed at a distance of, it is possible to realize a speed measuring device capable of measuring with a high speed resolution and a high S / N ratio.

According to the next invention, the optical delay means is
It is made up of more than one reflecting mirror, and local light is reflected between the reflecting mirrors to delay it, so that the structure can be miniaturized, and the target speed at an arbitrary distance is wide and the spectral line width of the laser light is wide. Even if a laser light source is used, it is possible to realize a speed measuring device capable of measuring with high speed resolution and high S / N ratio.

Further, according to the next invention, a plurality of optical delay elements for delaying the local light with different delay times by the optical delay means, and only one optical delay element through which the local light passes among the plurality of optical delay elements. By configuring the optical delay element switching means for selecting an element, the local light is delayed by various delay times, and the target speed at an arbitrary distance is
Even if a laser light source having a wide spectral line width of laser light is used, it is possible to realize a speed measurement device capable of measuring with high speed resolution and high S / N ratio.

Further, according to the next invention, a plurality of optical delay elements are formed by a plurality of optical fibers each having a different length,
The optical delay element switching means is formed by a mechanical optical switch, or a non-mechanical optical switch combining any one of electro-optical effect, acousto-optical effect and Faraday effect, or a plurality of effects thereof. By delaying the local light by various delay times, the target speed at an arbitrary distance can be measured with high speed resolution and high S / N ratio even if a laser light source having a wide spectral line width of the laser light is used. A speed measuring device can be realized.

Further, according to the next invention, the plurality of optical delay elements are formed by the plurality of movable total reflection mirrors, and the optical delay element switching means controls the angle or position of the plurality of movable reflection mirrors. By forming the reflecting mirror control means, the local light can be delayed by various delay times with a configuration that can be downsized as a whole, and the target speed at an arbitrary distance can be changed to a laser light source with a wide spectral line width of the laser light. Even if it is used, it is possible to realize a velocity measuring device capable of measuring with a high velocity resolution and a high S / N ratio.

Further, according to the next invention, by controlling the optical delay element switching means in accordance with the focus data obtained from the autofocus mechanism for adjusting the focal point of the transmission / reception optical system, the delay optimized for the target is obtained. The local light is delayed by various delay times in time, the local light is delayed by various delay times, and a target speed at an arbitrary distance is obtained by using a laser light source having a wide spectral line width of the laser light. Thus, it is possible to realize a speed measuring device capable of measuring with a high speed resolution and a high S / N ratio.

Further, according to the next invention, the autofocus mechanism is controlled to substantially condense the transmitted light on the target, and
By using the data from the autofocus mechanism at the time of substantially condensing, controlling the optical delay element switching means to select the delay time of the optical delay means, and measuring the target speed by the output of the optical receiving means. , By delaying the local light by various delay times and using a laser light source with a wide spectral line width of the laser light at a target speed at an arbitrary distance,
It is possible to realize a velocity measuring device capable of measuring with high velocity resolution and high S / N ratio.

[Brief description of drawings]

FIG. 1 is a first embodiment of a speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of FIG.

FIG. 2 is a block diagram showing another configuration of the speed measuring device of FIG.

FIG. 3 is a second embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of FIG.

FIG. 4 is a third embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing a configuration having an optical delay line made up of a plurality of total reflection mirrors.

5 is a block diagram showing another configuration of the speed measuring device in FIG.

FIG. 6 is a fourth embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of an optical delay line switching mechanism.

FIG. 7 is a fifth embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of an optical delay line switching mechanism.

FIG. 8 is a sixth embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of an optical delay line switching mechanism.

FIG. 9 is a seventh embodiment of the speed measuring device according to the present invention.
FIG. 3 is a block diagram showing the configuration of FIG.

FIG. 10 is a block diagram showing a configuration of an optical delay line switching mechanism as an eighth embodiment of the speed measuring device according to the present invention.

FIG. 11 is a block diagram showing a configuration of a ninth embodiment of a speed measuring device according to the present invention.

FIG. 12 is a block diagram showing a configuration of a conventional speed measuring device.

FIG. 13 is a spectrum distribution diagram for explaining spectra of beat signals of local light and signal light when a laser light source having a wide line width is used.

[Explanation of symbols]

1 Laser Light Source 2 Laser Light 2a, 31 Local Light 2b Transmitted Light 2c Signal Light 3 Target 4 Partial Reflector 5 Optical Multiplexer 6 Receiver 7 Optical Divider 8 Total Reflector 9 Frequency Shifter 10 Transmitter / Receiver Optical System 11, 14 Optical Coupler 12 optical circulator 13 optical delay line 14 second optical coupler 15, 18 ₁ , 18 ₂ , ..., 18 _n , 19, 20 optical fiber 16a, 16b, 16c, 16d, 33, 34 total reflection mirror 17a, 17b light Delay line switching mechanism 21a, 21b, 22a, 22b Optical fiber connector 23, 24 Optical switch 25 Delay time control circuit 26a, 26b Optical delay line switching mechanism 27, 28, 29, 30 Total reflection mirror 32, 35 Movable total reflection mirror 36 Auto Focus Mechanism 37 Optical Delay Line Switching Adjustment Device 100 Transmission Optical System 101 Reception Optical System

Claims (10)

[Claims] 1. A laser light source, an optical branching unit for branching the laser light from the laser light source into transmission light and local light, and irradiating the target with the transmission light, and reflecting from the target,
Transmitting / receiving optical means for receiving scattered light as signal light, optical delay means for delaying the local light, and optical multiplexing means for multiplexing the delayed local light and signal light.
A velocity measuring device comprising: an optical receiving unit that coherently detects the multiplexed local light and the signal light, and measures the target velocity by an output of the optical receiving unit. 2. The transmission / reception optical means includes an optical path switching optical system and a transmission / reception optical system, wherein the transmission light is applied to the target from the transmission / reception optical system through the optical path switching optical system, and reflected from the target. The scattered light is received by the transmission / reception optical system, and is switched to an optical path different from the optical path of the transmission light as the signal light through the optical path switching optical system, and is guided to the optical multiplexing means. The speed measuring device according to 1. 3. The transmission / reception optical means receives a transmission optical system for irradiating the target with the transmission light, and a reception optical system for receiving reflected / scattered light from the target and guiding it as the signal light to the optical combining means. The speed measurement device according to claim 1, further comprising: 4. The speed measuring device according to claim 1, wherein the optical delay means is a long optical fiber, and the local light is passed through the optical fiber to delay the local light. 5. The speed measuring device according to claim 1, wherein the optical delay means is composed of two or more reflecting mirrors and reflects the local light between the reflecting mirrors to delay the local light. 6. The optical delay means includes a plurality of optical delay elements for delaying the local light with different delay times, and a single optical delay element of the plurality of optical delay elements through which the local light passes. 2. The speed measuring device according to claim 1, further comprising: an optical delay element switching unit for selecting the optical delay element switching unit for delaying the local light by various delay times under the control of the optical delay element switching unit. 7. The plurality of optical delay elements are formed of a plurality of optical fibers having different lengths, and the optical delay element switching means is a mechanical optical switch, or an electro-optical effect, an acousto-optical effect and a Faraday effect. 7. The speed measuring device according to claim 6, wherein the speed measuring device comprises a non-mechanical optical switch that combines any one or a plurality of the effects. 8. The plurality of optical delay elements are composed of a plurality of movable reflecting mirrors, and the optical delay element switching means is constituted by a reflecting mirror control means for controlling an angle or a position of the plurality of movable reflecting mirrors. The speed measuring device according to claim 6, wherein: 9. An autofocus mechanism for adjusting a focal point of the transmission / reception optical system, and a switching control means for controlling the optical delay element switching means according to focus data obtained from the autofocus mechanism. The speed measuring device according to claim 6, which is characterized in that. 10. The optical delay element switching is performed by controlling the autofocus mechanism to substantially focus the transmission light on the target and using data from the autofocus mechanism at the time of the substantially focus. 10. The means for controlling the means to select the delay time of the optical delay means, and to measure the target speed by the output of the light receiving means.
The speed measurement device described in.