JP2000338244A - Coherent laser radar device - Google Patents

Abstract

(57) Abstract: A coherent laser radar device capable of suppressing the influence of the sum of spread spectra of a plurality of decorrelated spatial layers. SOLUTION: As an optical component, a CW laser, an optical modulator for modulating one of branched laser beams of the laser beam, an optical antenna for irradiating a target with the modulated laser beam as transmission light and receiving scattered light from the target, A pseudo-random modulation signal generator that has a photodetector that optically heterodyne-detects mixed light obtained by mixing the other of the split laser light with the reception light from the optical antenna, and sends a modulation signal to the optical modulator as an electrical component, and its modulation. A time delay unit for giving a time delay to a signal, a signal processing unit for obtaining physical information by an output signal of a mixer for integrating an output signal of the photodetector and a time-delayed modulated signal and a delay time of the time delay unit, The pseudo-random modulation signal generator used a pseudo-random modulation signal in which the long distance equivalent to one sequence has a sequence length sufficiently longer than the effective reception distance range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser radar device for measuring physical information such as a target distance, speed, density distribution, and speed distribution, and more particularly to a CW laser light source that oscillates at a single wavelength. The present invention relates to a coherent laser radar device that modulates a transmission light with a pseudo-random sequence by using a laser beam.

[0002]

2. Description of the Related Art As an apparatus for measuring physical information such as a target distance, velocity, density distribution, velocity distribution, etc., a pulse Doppler radar using microwaves and millimeter waves and an optical wave (laser) are used. Coherent laser radar device. Due to the difference in frequency between the two, the former has a feature that it can measure a wide range and a long distance, and the latter has a feature that a high spatial resolution and a high speed resolution can be obtained.

A single target having a certain size, such as an automobile or an aircraft, and having a boundary surface as a reflection or scattering surface is called a hard target. Further, when scattered light from a large number of minute scatterers distributed in a certain space is synthesized and used as received light, the spatially distributed target is called a soft target.

In the measurement of wind speed and wind speed distribution, which are targets of a soft target, the pulse Doppler radar mainly uses raindrops, fog and cloud particles in the atmosphere as scatterers, and obtains the wind speed from the Doppler shift of the echo. . Therefore, there is a drawback that echoes of sufficient intensity cannot be obtained in fine weather when there are no raindrops, fog, or cloud particles in the atmosphere, and turbulence in fine weather cannot be measured with a pulse Doppler radar.

A coherent laser radar device using a laser beam can obtain a sufficient scattering intensity even with an aerosol in the atmosphere, so that the wind speed and the wind speed distribution can be measured even in fine weather. For this reason, the coherent laser radar device is expected as an obstacle detection device including turbulence installed at an airport or on an aircraft.

FIG. 7 is a Japanese Patent Publication No. 64-2903 by Takeuchi et al.
No. 1993, the laser light source is shown in FIG.
This is a laser radar device that obtains target distance information by modulating transmission light with a pseudo-random signal using a laser. In FIG. 7, 1 is a transmitting unit, 2 is a receiving unit, 3 is a transmitting optical system, and 4 is a receiving optical system. The transmission unit 1 is a CW
A laser oscillator 5 for oscillating light, a modulator 6, and a sequence generator 7 for generating a pseudo-random signal (for example, an M-sequence or a Barker-sequence). The receiving unit 2 includes a photodetector 8,
It comprises a delay correlator 9 and a display recording unit 10.

Next, the operation of the illustrated configuration will be described. The CW light oscillated from the laser oscillator 5 is modulated by a pseudo-random signal (one sequence length M bits, time width per bit: τ) generated from the sequence generator 7, and transmitted from the transmission optical system 3 to the atmosphere as transmission light. Radiated inside. The distance at which the ratio of transmitting light included in the field of view of the receiving optical system 4 changes from 0 to positive is R
m. This distance Rm is the minimum measurement distance of the laser radar device, and a target farther than Rm can be measured.

The reflected light from the target is transmitted to the receiving optical system 4
And is detected by the photodetector 8 and converted into an electric signal. The received signal is recorded, and a correlation process with a pseudo-random signal from the sequence generator 7 multiplied by a time delay t _d is performed by the delay correlator 9. By adjusting the delay time t _d, the information of the reflection intensity of the distance that the round trip time t _r of the received light is equal to the delay time t _d the distance resolution cτ / 2: can be measured by (c speed of light). Therefore, by sweeping the delay time t _d in the measurement region, the position if the target hard target, it is possible to measure the spatial distribution if the target soft targets.

By using a CW laser oscillating at a single frequency as a light source and performing heterodyne detection in a receiving section, the amount of Doppler shift of the target can be detected, and not only distance information of the target but also velocity information can be obtained.

A coherent laser radar device using a coherent CW laser as a light source can avoid the drawbacks of the coherent laser radar device using a pulse laser.
Further, by modulating the transmission light, there is a possibility that arbitrary distance resolution and velocity resolution can be obtained.

FIG. 8 is disclosed by Hirano et al.
No. 87, which is a coherent CW laser radar device using a CW laser oscillating at a single wavelength as a light source. In the configuration shown in FIG. 8, laser light from a CW laser oscillator 31 oscillating at a single wavelength
It is divided into two by two. One of them is a sequence generator 33
The light is modulated by an optical modulator 34 that modulates based on a pseudo-random modulation signal generated in the above, and is transmitted from a transmission / reception optical system 37 to a target 39 as transmission light 38 via a polarizer 35 and a １ ／ wavelength plate 36. You. The transmission light 38 is scattered or reflected by the target 39, and a part of the scattered light or reflected light is used as the reception light 40 as the transmission / reception optical system 3.
7 is received. The received light 40 is separated from the transmission light 38 by the polarizer 35 via the 波長 wavelength plate 36 and guided to the optical multiplexer 41.

The other of the laser beams from the laser oscillator 31 divided by the optical distributor 32 is used as local light in optical heterodyne detection. The local light passes through a reflecting mirror 42, and its optical frequency is shifted by an intermediate frequency f _IF by a frequency shifter 43, and then the half-wave plate 44
, The polarization plane is rotated by 90 ° so that the polarization plane with the reception light 40 substantially coincides with the optical multiplexer 41.
Are multiplexed with the reception light 40. The mixed light of the local light and the reception light 40 is subjected to optical heterodyne detection in the PD 45 as a photodetector. The received signal from the PD 45 is amplified by the amplifier 46 and passes through the band-pass filter 47 to the correlator 4.
To 8.

In the correlator 48, the received signal is
Arbitrary delay time t _dGiven
The signal is integrated with the pseudo-random modulated signal that has modulated the light and the correlation is obtained.
Can be Hard target with sufficient reflectivity for target 39
Target, round trip of received light to target 39
Time t_rIs the delay time t_dPower meter when equal to
At 49, the peak of the output power of the correlator 48 is obtained. Ma
The Doppler frequency of the received light due to the movement of the target
Let fd be the output of correlator 48 in frequency discriminator 26.
F as the force frequency_IF−f_dIs obtained. Therefore, the control equipment
Delay time t_dIn the measurement area
From the power meter 49, the distance information of the target and the frequency
Obtaining the speed information of the hard target from the number discriminator 26
Can be.

FIG. 9 shows a configuration diagram for measuring a soft target. 8 differs from FIG. 8 in the signal processing unit after the correlator 48. The operation is the same as described above up to modulation of laser light, transmission and reception, and correlation with a pseudo-random modulation signal. The output signal of the correlator 48, the correlation is consistent round trip time t _r of the received light on the received signal from the equal distance and the delay time t _d, with significant peaks at the frequency f _IF -f _d. Received signals from other distances become uncorrelated, and their frequency spectrum is spread and spread over a wide frequency range.

In the signal processing unit of FIG. 9, the output signal of the correlator 48 is converted into a digital signal by the AD converter 101,
A frequency spectrum is obtained by the FFT circuit 102, and a peak having a frequency f _IF −f _d is detected by the signal extraction circuit 103. Target speed at a distance round trip time t _r of the received light from the frequency and intensity of the peak is equal to the delay time t _d, the distribution density and the like is obtained.

A received signal of a coherent CW laser radar device targeting a soft target is represented by the following equation (1).

[0017]

(Equation 1)

Here, P _CW : transmission light output, β (R): backscattering coefficient of target (soft target), Dr: aperture of receiving optical system, T (R): atmospheric transmittance, T _t : transmission optical System transmittance, _Tr : reception optical system transmittance, SRF (R): signal attenuation coefficient, R: distance

The atmospheric transmittance T (R) and the signal attenuation coefficient SRF (R) are represented by the following equations (2) to (4).

[0020]

(Equation 2)

Here, α (R ′): atmospheric attenuation coefficient, F:
Receiving optical system focal point distance, k = 2π / λ, H = 2.914
383, C ² _n (R): atmospheric structure constant

When a soft target distributed in a space such as the atmosphere is measured with a CW laser beam, the space is considered as a series of thin layers whose thickness along the optical axis of the transmitted light is ΔR as shown in FIG. . Here, ΔR is a distance resolution and is represented by the following equation (5).

[0023]

(Equation 3)

Here, τ is a time width per bit (element) of the pseudo-random modulation signal.

Assuming that each layer has a reflector having the same reflectance as that of the target (soft target) of the layer, equation (1) becomes as follows.

[0026]

(Equation 4)

In the pseudo-random modulation CW coherent rider, a single atmospheric layer received signal is used as a signal component by a correlation process. The received signal from the k-th layer is represented as follows.

[0028]

(Equation 5)

Generally, the S / N ratio is represented by the ratio of the signal strength to the system noise of the receiving system such as shot noise and thermal noise. The S / N ratio is expressed by the following equation.

[0030]

(Equation 6)

Here, η _f : electric filter efficiency, B: reception bandwidth.

The reception bandwidth is inversely proportional to the time required for performing the correlation operation, that is, the time corresponding to the length of one sequence of the pseudo-random modulated signal (one long sequence). Therefore, the long time for one series for obtaining the required S / N ratio is obtained from equation (8).

[0033]

Unlike a hard target, a soft target simultaneously receives scattered light from a plurality of spatial layers as shown in equation (6). By performing pseudo-random modulation, the received signals of the uncorrelated spatial layer that are not noticed are spread spectrum. However, when considering the sum of the spread spectrum of a plurality of spatial layers, it is necessary that the maximum value of the intensity is sufficiently suppressed with respect to the received signal from the spatial layer of which the correlation is of interest. is there.

FIG. 11 shows an example of the distance dependence of the reception intensity of the coherent CW laser radar device obtained by using the equation (7). The position and size of the peak are determined by the receiving optical system focal point distance F and the receiving optical system aperture diameter Dr. From the figure, it can be seen that there is an effective reception distance range where an effective reception intensity can be obtained. Therefore, it is sufficient to consider a received signal from a spatial layer within the effective receiving distance range.

Under the conditions shown in FIG. 12, the FFT circuit 1
02, a frequency spectrum of the received signal is obtained.
The effective reception distance range is set to 9 × ΔR corresponding to 9 bits of the pseudo-random modulation signal, and the one-sequence length of the pseudo-random modulation signal obtained from Expression (8) is set to 31 bits. Therefore, the distance equivalent to one series long time (defined as the distance that can be reciprocated in the time of one series long) is 31 × ΔR. The pseudo-random sequence used for the pseudo-random modulation signal is M of 31 bits.
The delay time is set so that the correlation is matched with one spatial layer in the effective reception distance range. The Doppler shift exists only in the spatial layer whose correlation is matched.

Under these conditions, the result of obtaining the frequency spectrum of the received signal obtained by the FFT circuit 102 is shown in FIG.
3 is shown. The horizontal axis in FIG. 13 is the frequency based on the intermediate frequency _fIF . The sum of the spread spectra of a plurality of uncorrelated spatial layers is a signal that is spread over a wide frequency range with the envelope of a spectrum waveform of a square wave having a pulse width τ.
(In the figure, f _B = 1 / τ.) However, as is clear from the figure, there are some peaks having large values depending on the type, sequence length, time width, and the like of the pseudo-random modulation signal. If these peak values are approximately the same or higher than the peak values of the spectrum of the received signal from the spatial layer with the coincident correlation of interest, the information of the spatial layer with the coincident correlation of interest is obtained. I can't get it. In FIG. 13, the spectrum of the received signal from the spatial layer with matching correlation has a single sharp peak at frequency −f _d , but is hidden by the sum of the spread spectra of a plurality of uncorrelated spatial layers.

As described above, due to the influence of the sum of the spread spectra of a plurality of decorrelated spatial layers, there is a disadvantage that the measurement of the soft target cannot be performed with sufficient accuracy using the coherent CW laser radar device.

The present invention has been made in order to solve the above-described problems of the prior art, and has a high S / N ratio represented by the ratio of signal strength to system noise of a receiving system such as shot noise and thermal noise. It is another object of the present invention to provide a coherent laser radar device capable of suppressing the influence of the sum of spread spectra of a plurality of uncorrelated spatial layers.

[0039]

A coherent laser radar apparatus according to the present invention comprises, as optical components, a CW laser oscillating at a single wavelength, a branching means for branching laser light from the CW laser, and a branching means. An optical modulator that modulates one of the laser lights branched by the above, an optical antenna that irradiates the modulated laser light as transmission light toward a target, and receives scattered light from the target, and is branched by the branching unit. A mixing unit that mixes the other of the divided laser beams as local light with the received light from the optical antenna, and a photodetector that performs optical heterodyne detection of the mixed light, and the optical modulator includes: A pseudo-random modulation signal generator that sends a modulation signal to a time delay unit that provides a time delay to a part of the modulation signal of the pseudo-random modulation signal generator;
A correlator that integrates the output signal of the photodetector and the time-delayed modulated signal from the time delay device; and a target and the intensity and frequency of the output signal of the correlator and the delay time in the time delay device. Signal processing means for obtaining physical information such as distance, speed, etc., and the pseudo-random modulation signal generator has a pseudo-random modulation signal having a time required for one sequence length and having sufficient intensity for the optical antenna. It is characterized in that a pseudo-random sequence that is sufficiently longer than the time required for light to reciprocate in the distance range where light can be obtained is used.

Further, the pseudorandom modulation signal generator is capable of taking the time required for the pseudorandom modulation signal for one sequence length to cause the light to reciprocate within a distance range in which the optical antenna can receive the received light of sufficient intensity. It is characterized in that the time required is longer than 30 times.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram showing a coherent laser radar device according to Embodiment 1 of the present invention. In the configuration shown in FIG.
The laser light from the CW laser 51 oscillating at ₀ is coupled to an optical fiber, and the laser light coupled to the optical fiber is split into two by a first fiber type optical coupler 52. One of the two divided laser beams is used as transmission light, and the other is used as local light in optical heterodyne detection.

The transmission light passes through an optical modulator 53 and a high-output optical fiber amplifier 54 placed in the optical path of the optical fiber, and reaches a transmission / reception separation optical antenna 55. The optical modulator 53 is
The transmission light is modulated by a pseudo random modulation signal corresponding to a pseudo random sequence (for example, M sequence) from the pseudo random signal generator 56. The modulation may be any of intensity modulation, frequency modulation, and phase modulation. Here, an M sequence (the number of sequences N and a time width τ of 1 bit) is used as a pseudo random sequence.
The following shows an example in which phase modulation is used for modulation.

FIG. 2 shows an example of modulation of transmission light. The pseudo-random signal generator 56 repeatedly and continuously generates a pseudo-random modulation signal that outputs a voltage of [1, -1] according to the value [1, 0] of the pseudo-random sequence at every time τ. The optical modulator 53 performs binary phase modulation of [0, -π] on the transmission light according to the value [1, -1] of the pseudo random modulation signal.

The transmission / reception separation optical antenna 55 is an optical fiber.
The transmitted light beam diameter D_rAnd the radius of curvature F of the wavefront
And convert it to a target beam 57
A first function of irradiating the target and a target 57
Of the scattered or reflected light of the laser beam at
To the photodetector 58 for optical heterodyne detection
It has a second function of coupling to an optical fiber. target
(Target) 57 is moving with respect to the laser radar device
If the received light is Doppler shifted according to its moving speed
The frequency of the received light is f₀+ F_dBecomes (Dot
Puller frequency is f _dAnd )

The other laser light divided into two by the first fiber type optical coupler 52 used for the local light is a frequency shifter 59 placed in the optical path of the optical fiber.
After that, the light is mixed with the reception light from the transmission / reception separation optical antenna 55 by the second fiber type optical coupler 61 and reaches the photodetector 58. In the frequency shifter 59, the local light undergoes a frequency shift corresponding to the intermediate frequency f _IF , and the frequency becomes f ₀ + f _IF .

The mixed received light and local light are subjected to square detection in the photodetector 58 to be subjected to optical heterodyne detection. As a result, beat signals of the received light and the local light are output. The beat signals of the received light and the local light are integrated by the correlator 62 with the pseudo-random modulated signal from the pseudo-random signal generator 56 that has undergone a time delay of an arbitrary delay time t _d by the variable delay 63, The correlation is taken. The signal processor 64 analyzes the signal strength and frequency of the correlation signal from the correlator 62, and detects a target (target) and a Doppler frequency.

Here, the time required from the generation of the pseudo-random modulated signal by the pseudo-random signal generator 56 to the modulation of the transmission light by the optical modulator 53 and the delay time t _d given by the variable delay 63 are excluded. The time required for the pseudo-random modulated signal to be generated by the pseudo-random signal generator 56 and then to the correlator 62 and the time required for the received light and the beat signal of the local light to reach the correlator 62 from the photodetector 58 are negligible. . When the target is a soft target, the frequency spectrum of the output signal from the correlator 62 is basically equal to that of the conventional example of the coherent CW laser radar.

In the first embodiment, the S / N ratio represented by the ratio of the signal intensity to the system noise of the receiving system such as shot noise and thermal noise is increased, and the spread spectrum of a plurality of uncorrelated spatial layers is increased. In order to suppress the influence of the sum of the pseudo random modulation signals generated by the pseudo random signal generator 56, the pseudo random modulation signal having a sequence length corresponding to a long time corresponding to one long sequence is sufficiently longer than the effective reception distance range. Is used.

Thus, by reducing the ratio of the number of uncorrelated spatial layers in the effective reception distance range to the total number of sequences, the intensity of the sum of the spread spectrum of the plurality of uncorrelated spatial layers is suppressed. can do.

The frequency spectrum of the output signal from the correlator 62 is obtained. Effective receiving distance range is determined by the receiving optical system focal point distance F and the reception optical system aperture diameter D _r. As shown in FIG. 3, the effective reception distance range is set to 9 × ΔR corresponding to 9 bits of the pseudo random modulation signal (see FIG. 3A). The pseudo-random modulation signal used is an M-sequence in which the pseudo-random sequence is 127 bits, and the delay time is set so that the correlation matches one spatial layer within the effective reception distance range (see FIG. 3B). The relationship is such that the effective reception distance range and the long distance equivalent to one series are approximately 1:14.

FIG. 4 shows the frequency spectrum of the output signal at this time. Compared with the conventional example shown in FIG. 13, the intensity of the sum of the spread spectrums of a plurality of spatial layers that are clearly uncorrelated is suppressed, and the spectrum of the received signal from the spatial layer with a correlated coincidence has a single sharp peak at the frequency. -F appears in _d .

Further, as shown in FIGS. 5 (a) and 5 (b), FIG. 6 shows the frequency spectrum of the output signal under the condition that the ratio between the effective reception distance range and the long distance equivalent to one series is increased. At this time, the ratio between the effective reception distance range and the long distance corresponding to one series is approximately 1:57. The pseudo-random modulation signal used is an M-sequence in which the pseudo-random sequence is 511 bits. Compared to FIG. 4, the intensity of the sum of the spread spectra of a plurality of uncorrelated spatial layers is further suppressed, and the intensity ratio with the spectrum of the received signal from the spatial layer whose correlation appears in frequency is 12 dB as compared with the maximum value. That is all.

The ratio between the peak value of the spectrum of the received signal from the spatial layer having a coincidence appearing at the frequency −f _d and the maximum intensity of the sum of the spread spectra of a plurality of uncorrelated spatial layers is 1
The condition for setting it to 0 dB or more is that the distance equivalent to one series long time is set to 30 times or more the effective reception distance range.

As described above, in the coherent CW laser radar device according to the above-described embodiment, by using a pseudo-random modulated signal in which the long distance equivalent to one sequence has a sequence length sufficiently longer than the effective reception distance range. Also in the measurement of the soft target, the effect of the sum of the spread spectra of a plurality of uncorrelated spatial layers can be suppressed, and there is an effect that highly accurate measurement can be performed. Further, by setting the long distance equivalent to one series to be at least 30 times the effective reception distance range, the sum of the peak value of the spectrum of the received signal from the spatial layer having correlation and the spread spectrum of a plurality of uncorrelated spatial layers is obtained. There is an effect that the ratio to the maximum intensity can be 10 dB or more. Furthermore, since a long pseudo-random modulation signal having a long sequence is used, a high S / N ratio can be obtained.

[0055]

As described above, according to the present invention, as an optical component, a CW laser oscillating at a single wavelength,
A branching unit that branches the laser light from the W laser, an optical modulator that modulates one of the laser lights branched by the branching unit, and irradiates the modulated laser light as a transmission light toward a target. An optical antenna for receiving the scattered light from the optical antenna; a mixing means for mixing the other of the laser light branched by the branching means with the received light from the optical antenna as local light; and optical heterodyne detection of the mixed light. A pseudo-random modulation signal generator that has a photodetector and sends a modulation signal to the optical modulator as an electrical component, and a time delay unit that provides a time delay to a part of the modulation signal of the pseudo-random modulation signal generator A correlator for integrating an output signal of the photodetector and a time-delayed modulated signal from the time delay device; an intensity and frequency of an output signal of the correlator; and the time delay device Signal processing means for obtaining physical information such as a target distance and a speed based on a delay time in the optical antenna, wherein the pseudorandom modulation signal generator takes a time required for one series length as a pseudorandom modulation signal. Since a pseudo-random sequence that is sufficiently larger than the time required for light to reciprocate in a distance range in which received light with sufficient intensity is obtained is used, even in the measurement of a soft target, a plurality of uncorrelated spatial layers are used. The effect of the sum of the spread spectrum can be suppressed, high-precision measurement can be performed, and a high S / N ratio can be obtained since a pseudorandom modulation signal having one long sequence is used. .

The pseudo-random modulation signal generator may be configured such that the time required for the pseudo-random modulation signal for one series length is such that the light reciprocates within a distance range in which received light of sufficient intensity can be obtained at the optical antenna. By making the required time longer than 30 times, the ratio between the peak value of the spectrum of the received signal from the spatial layer having the matched correlation and the maximum intensity of the sum of the spread spectrums of the plurality of uncorrelated spatial layers is 10 dB or more. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a coherent laser radar device according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram illustrating an example of modulation of transmission light according to Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram of a signal strength and a sequence length of a pseudo-random modulation signal according to Embodiment 1 of the present invention.

4 is an explanatory diagram showing a frequency spectrum of a received signal under the conditions shown in FIG.

FIG. 5 is an explanatory diagram of the signal strength and the sequence length of the pseudo-random modulation signal when the ratio between the effective reception distance range and the one-line long-time equivalent distance is increased.

FIG. 6 is an explanatory diagram showing a frequency spectrum of a received signal under the conditions shown in FIG.

FIG. 7 is a configuration diagram showing a laser radar device disclosed in Japanese Patent Publication No. 64-2903.

FIG. 8 is a configuration diagram of a coherent CW racer radar device disclosed in Japanese Patent Application Laid-Open No. 2-284087.

FIG. 9 is a conventional configuration diagram when measuring a soft target.

FIG. 10 is an explanatory diagram in a case where a soft target distributed in a space such as the atmosphere is measured by a CW laser beam.

FIG. 11 shows a coherent CW obtained using equation (7).
FIG. 4 is an explanatory diagram illustrating an example of distance dependence of reception intensity of a laser radar device.

FIG. 12 is an explanatory diagram of signal strength and sequence length of a pseudo-random modulation signal in a conventional example.

13 shows an FFT circuit 1 under the conditions shown in FIG.
FIG. 4 is an explanatory diagram showing a frequency spectrum of a reception signal obtained in 02.

[Explanation of symbols]

51 CW laser, 52 optical coupler, 53 optical modulator,
54 High-output optical fiber amplifier, 55 Transmission / reception separation optical antenna, 56 pseudo-random signal generator, 57 target, 58 photodetector, 59 frequency shifter, 60 phase difference compensator, 61 optical coupler, 62 correlator, 63
Variable delay unit, 64 signal processing unit.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuzo Wakadaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term within Mitsubishi Electric Corporation (reference) 5J084 AA02 AA05 AA07 AB08 AD04 BA03 BA04 BA32 BA45 BA51 BB31 CA04 CA07 CA08 CA09 CA42 CA64 CA68 EA04

Claims (2)

[Claims] 1. An optical component comprising: a CW laser oscillating at a single wavelength; a branching unit for branching a laser beam from the CW laser; and an optical modulator for modulating one of the laser beams branched by the branching unit. And an optical antenna that irradiates the modulated laser light as transmission light toward a target and receives scattered light from the target; and the other of the laser light branched by the branching unit as local light from the optical antenna. Mixing means for mixing with the received light, and a photodetector for optically heterodyne-detecting the mixed light; as an electrical component, a pseudo-random modulation signal generator for sending a modulation signal to the optical modulator; A time delay unit for providing a time delay to a part of the modulation signal of the pseudo-random modulation signal generator, and a time delay unit that outputs the output signal of the photodetector and the time-delayed modulation signal from the time delay unit And a signal processing means for obtaining physical information such as a target distance and a speed based on the intensity and frequency of the output signal of the correlator and the delay time in the time delay unit. The signal generator generates a pseudo-random modulated signal as a pseudo-random modulated signal, the time required for one sequence length being sufficiently larger than the time required for the light to reciprocate in the distance range in which the received light of sufficient intensity is obtained by the optical antenna. A coherent laser radar device characterized by using: 2. The method according to claim 1, wherein the pseudo-random modulation signal generator takes a time required for the pseudo-random modulation signal for one sequence length so that the light reciprocates within a distance range in which received light of sufficient intensity can be obtained at the optical antenna. 2. The coherent laser radar device according to claim 1, wherein the time required is longer than 30 times.