JP2000338243A - Coherent laser radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coherent laser radar device for accurately detecting the peak of a reception signal from distance where correlation coincides. SOLUTION: The coherent laser radar device is provided with, as optical parts, a light modulator 53 for modulating one laser beam branched from the laser beams of a CW laser, a light antenna 55 for applying the modulated laser beam to a target as a transmission beam and receiving scattered beam from the target, and a photo detector 58 for performing the heterodyne detection of mixed light where the other of the branch laser beams is mixed with the reception light from the light antenna 55 as a local beam. Also, the device is provided with, as electrical parts, a pseudo random modulation signal generator for transmitting a modulation signal to the light modulator 53, time delay equipment for delaying the modulation signal, and a signal-processing means for obtaining the physical information of the target by the output signal of a mixer where the output signal of the photo detector is integrated with the time-delayed modulation signal and the delay time of the time delay equipment, where the pseudo random modulation signal generator has a function for generating pseudo random modulation by switching based on a plurality of different pseudo random series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Apparatuses for measuring physical information such as the distance, velocity, density distribution, and velocity distribution of a target include a pulse Doppler radar using microwaves and millimeter waves and a light wave (laser). ), There is a 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 (target) having a certain size, such as an automobile and an aircraft, and having a boundary surface as a reflection or scattering surface is called a hard target. When scattered light from a large number of minute scatterers distributed in a certain space is combined to be received light, the target (target) spatially distributed is called a soft target.

In measurements such as wind speed and wind speed distribution in which a soft target is a target (target), a pulse Doppler radar mainly uses raindrops, fog, and cloud particles in the atmosphere as scatterers, and calculates the wind speed from the Doppler shift of the echo. Have gained. 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. 9 is a view of Japanese Patent Publication No. 64-2903 by Takeuchi et al.
FIG. 1 is a configuration diagram showing a laser radar device that uses a CW laser as a light source and modulates transmission light with a pseudo-random signal to obtain target distance information. In FIG. 9, 1 is a transmitting unit, 2 is a receiving unit, 3 is a transmitting optical system, and 4 is a receiving optical system. The transmitting unit 1 includes a laser oscillator 5 that oscillates CW light, a modulator 6, and a sequence generator 7 that generates a pseudo-random signal (for example, an M sequence or a Barker sequence). The receiving unit 2 includes a photodetector 8, a delay correlator 9, and a display recording unit 10.

Next, the operation according to the above configuration will be described. The CW light oscillated from the laser oscillator 5 is a pseudo random signal (one sequence length M bits,
The light is modulated by a time width per bit: τ) and emitted from the transmission optical system 3 into the atmosphere as transmission light. The distance at which the ratio of the transmitted light included in the field of view of the receiving optical system 4 changes from 0 to a positive value is defined as Rm. 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 received signal from a distance round-trip time t _r of the received light is equal to the delay time t _d is correlated to the pseudo-random signal subjected to time delay, from the other a distance Are uncorrelated.

Accordingly, 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 area, the position can be measured when the hard target is the target (target), and the spatial distribution when the soft target is the target (target).

Further, by using a coherent CW laser as a light source and performing heterodyne detection in a receiving unit, 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 disadvantages 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. 10 is disclosed by Hirano et al.
No. 087, which is a configuration diagram showing 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. 10, laser light from a CW laser oscillator 31 oscillating at a single wavelength is split into two by a light distributor 32. One of them is modulated by an optical modulator 34 that performs modulation based on a pseudo-random modulation signal generated by a sequence generator 33, and the polarizers 35, 1 /
After passing through a four-wavelength plate 36, the light is transmitted from a transmission / reception optical system 37 to a target 39 as transmission light 38. Transmit light 38
Is scattered or reflected by the target 39, and a part of the scattered light or the reflected light is received by the transmission / reception optical system 37 as the reception light 40.

The received light 40 is received by the 波長 wavelength plate 3
6, the light is separated from the transmission light 38 by the polarizer 35,
The light is 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. After the local light is shifted its optical frequency by the intermediate frequency f _IF by the frequency shifter 43 through the reflecting mirror 42, the polarization plane of the received light 40 in the optical multiplexer 41 is substantially matched by the half-wave plate 44. The polarization plane is rotated by 90 ° as described above, and is multiplexed with the reception light 40 in the optical multiplexer 41. 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 signal received from the PD 45 is amplified by the amplifier 46 and reaches the correlator 48 via the band-pass filter 47.

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_dPseudo-lander when equal to
Maximum correlation between the modulated signal and the received signal
The peak of the output power of the correlator 48 is obtained by the correlator 49. Ma
The Doppler frequency of the received light due to the movement of the target
To f_dIn the frequency discriminator 26, the output of the correlator 48
F as the force frequency_IF−f_dIs obtained.

Therefore, the delay time t _{d is}
Is swept in the measurement region, the distance information of the target from the power measuring device 49 and the speed information of the hard target from the frequency discriminator 26 can be obtained.

FIG. 11 shows a configuration diagram for measuring a soft target. 10 is different from FIG. 10 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 are uncorrelated, and their frequency spectrum is spread and spread over a wide frequency range.

In the signal processing section of FIG. 11, the output signal of the correlator 48 is converted into a digital signal by the AD converter 101, and the frequency spectrum is obtained by the FFT circuit 102.
The signal extraction circuit 103 detects a peak having a frequency f _IF −f _d . Speed of the target (target) in the 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.

In the coherent CW laser radar device in which the transmission light is modulated in a pseudo-random sequence as described above, by increasing the observation time per measurement, even if a CW laser whose power is smaller than that of a pulse laser is used. A sufficient S / N ratio is obtained. However, for this purpose, a pseudo-random sequence having a sequence length exceeding several hundred bits to several thousand bits may be used.

FIG. 12 shows a spectrum of a received signal when a uniform soft target is measured using a pseudo random sequence having a sequence length of 127 bits. The horizontal axis is based on the frequency f _IF -f _d of the received signal from a distance round-trip time t _r of the received light is equal to the delay time t _d in frequency. Frequency 0 sharp peak received signal correlation (f _IF -f _d) matches are found. Further, from −f _B to f _B (= 1 / τ; τ:
In a wide frequency range (time width per bit), received signals that have undergone spectrum spreading from the entire non-correlated distance within the distance range in which effective received light intensity can be obtained are distributed. In the measurement of a soft target, it is necessary that the peak value of a received signal having a correlation match is sufficiently large with respect to a received signal that has undergone spectrum spreading from the entire non-correlated distance.

[0021]

As described above, in the conventional coherent CW laser radar device for measuring a soft target, the observation time per measurement is long in order to obtain a sufficient S / N ratio. . Further, a pseudo-random sequence in which the time corresponding to one sequence length corresponds to the observation time per measurement is used. For this reason, a pseudo-random sequence having a long sequence length may be used.

On the other hand, to obtain the Doppler frequency,
Frequency analysis of the received signal is required. In order to perform the correlation process, it is necessary to use the data of the received signal at the time corresponding to one sequence length for this frequency analysis. When the AD converter and the FFT are used in the signal processing unit as shown in FIG. 11, it is necessary to perform the FFT using the AD converted data of the received signal in a time corresponding to a large amount of one-sequence length. The amount of calculation of the FFT is approximately proportional to the square of the number of data points used. For this reason, FF
There is a disadvantage that the amount of calculation at T becomes very large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the prior art, and provides a coherent laser radar device capable of detecting a peak of a received signal from a distance where a correlation is matched with high accuracy. The purpose is to do so.

[0024]

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 beams branched by the above, and an optical antenna that irradiates the modulated laser beam as transmission light toward a target (target) and receives scattered light from the target (target). A mixing unit that mixes the other of the laser beams branched by the branching unit as local light with the reception light from the optical antenna, and a photodetector that optically heterodyne-detects the mixed light, and includes an electric component. As a pseudo-random modulation signal generator that sends a modulation signal to the optical modulator,
A time delay unit for giving a time delay to a part of the modulation signal of the pseudo-random modulation signal generator, and a correlator for taking the product of the output signal of the photodetector and the time-delayed modulation signal from the time delay unit And signal processing means for obtaining physical information such as the distance and speed of a target (target) based on the intensity and frequency of the output signal of the correlator and the delay time in the time delay unit. The device has a function of switching and generating pseudo-random modulation based on a plurality of different pseudo-random sequences.

Further, the pseudorandom modulation signal generator is characterized in that it has means for varying a time interval of a timing signal for generating a pseudorandom modulation signal.

Further, the pseudo-random modulation signal generator converts a pseudo-random modulation signal corresponding to an observation time per measurement for obtaining a sufficient S / N ratio into a modulation signal or a timing based on a plurality of different pseudo-random sequences. It is characterized by comprising a series of modulated signals having different signal time intervals.

[0027]

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 illustrated configuration, the laser light from the CW laser 51 oscillating at a single wavelength f ₀ is coupled to an optical fiber, and the laser light coupled to the optical fiber is
The light is split into two by a first fiber type optical coupler 52. One of the two divided laser beams is used as transmission light.
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 a value of a pseudo-random sequence [1, 0] at each 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 beam split 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 to detect a target (target) and a Doppler frequency. The signal processing device 64 includes an AD converter 65, an FFT circuit 66, and a signal extraction circuit 67. Here, the time required from the time when the pseudo-random modulation signal is generated by the pseudo-random signal generator 56 to the time when the optical modulator 53 modulates the transmission light,
Variable delays 63 except the delay time t _d given by the pseudo-random modulation signal pseudo random signal generator time reaches the correlator 62 from occurring at 56 and receive light and beat signal of local light photodetector 58 From the time to the correlator 62 can be ignored. 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 this embodiment, a sufficient S / N
A pseudorandom modulation signal corresponding to an observation time per measurement for obtaining a ratio is formed by a series of modulation signals based on a plurality of different pseudorandom sequences. Thereby, the FFT may be performed in units of modulation signals based on the pseudo random sequences of the plurality of different modulation signals,
Finally, by taking the sum of the respective frequency spectra obtained by the FFT, the spectrum of the received signal can be obtained. Thus, since the FFT is performed after dividing the number of measurement data, the amount of calculation can be reduced.

The pseudo-random signal generator 56 for generating modulated signals based on a plurality of different pseudo-random sequences has the configuration shown in FIG. That is, the sequence selecting means 68 and the pseudo-random modulated signal generating means 69
A pseudo-random sequence generating means 70 having a plurality of different pseudo-random sequences and transmitting an arbitrary pseudo-random sequence to a pseudo-random modulation signal generating means 69 in accordance with a signal from the sequence selecting means 68; And timing generating means 71 for generating a timing signal at an arbitrary time interval according to the following. The sequence selection means 68 selects the pseudo random sequence and the time width τ per bit of the modulation signal, and the pseudo random modulation signal generation means 69 generates a pseudo random modulation signal.

FIG. 4 shows an example of a pseudo random modulation signal according to this embodiment. The A-sequence is a pseudo-random sequence used for a pseudo-random modulated signal corresponding to an observation time per measurement, the time corresponding to one sequence length used in the conventional method. The pseudo-random modulation signal according to this embodiment is
The sequence length is composed of four different pseudo-random sequences of B, C, D, and E, each of which is approximately 1/4 of the length of the A sequence. In the frequency analysis of the received signal, the FFT circuit 66 converts the received signal to B,
FFT is performed four times for each of the pseudo-random sequence units of C, D, and E, and the sum of the four frequency spectra is obtained by the signal extraction circuit 67, whereby the reception signal of the pseudo-random modulation signal using the A sequence is obtained. Collectively FFT
The spectrum corresponding to the frequency spectrum obtained by the above is obtained.

FIG. 5 shows an example of a frequency spectrum of a received signal when a pseudo random modulation signal composed of four pseudo random sequences B, C, D and E is used. B, C, D, E
In this example, the sequence length of the four pseudo random sequences is set to 31. Further, the time width τ per bit is equal to the pseudo random sequence used in FIG. As the frequency spectrum of the received signal according to this embodiment, the same spectrum as that of the conventional example shown in FIG. 12 is obtained.

On the other hand, as shown in FIG.
Consider an example in which a dam sequence is used repeatedly. Pseudo-random modulation
The signal is a repetition of the B sequence as shown in the figure.
You. FIG. 7 shows a pseudo-random modulated signal obtained by repeating the B sequence four times.
4 shows a frequency spectrum of a received signal when the symbol is used. B
The sequence length of the sequence is also 31. From the figure, at the same observation
If the same sequence is repeated between
Me-f_BTo f_BReception over a wide frequency range
Is the entire non-correlated distance within the range where the light intensity can be obtained?
Cannot sufficiently suppress the strength of these received signals,
Wave number f_IF−f _dThe received signal from the distance where the correlation of
It cannot be detected with high accuracy.

FIG. 8 shows the frequency spectrum of the received signal for one B sequence. The spread spectrum has a distribution with the frequency spectrum of a square wave having a time width τ as an envelope.
The position of the peak of the spread spectrum is affected by the type of the pseudo-random sequence used for the modulated signal. For this reason, when the same sequence is used repeatedly, its intensity cannot be sufficiently reduced as shown in FIG. When different pseudo-random sequences are used, the positions of the peaks are different in each sequence, and thus the sum is averaged when the sum is taken, so that the maximum value of the spread spectrum can be reduced.

As described above, this embodiment has means for continuously switching and generating modulated signals based on a plurality of different pseudo-random sequences, so that when the same sequence is used repeatedly, In comparison, the maximum value of the spread spectrum can be reduced, and the peak of the received signal from the distance where the correlation is matched can be detected with high accuracy. Further, the amount of calculation in the FFT is reduced by forming a pseudo-random modulation signal corresponding to the observation time per measurement for obtaining a sufficient S / N ratio by a series of modulation signals based on a plurality of different pseudo-random sequences. effective.

Although the embodiment has been described with respect to an example in which the time per bit of the modulated signal is equal, the timing generating means 71 can produce a modulated signal having a different time per bit. If the time per bit is different, the pseudo-random modulated signal using the same pseudo-random sequence is the spread spectrum of the received signal from the entire non-correlated distance within the distance range where the effective received light intensity is obtained. Since the peak positions are different, they can be regarded as different pseudo random modulation signals. As a result, the same effect as described above can be obtained even if modulation signals having different times per bit are used.

[0042]

As described above, according to the present invention, the pseudo-random modulation signal generator has a function of switching and generating pseudo-random modulation based on a plurality of different pseudo-random sequences. The maximum value of the spread spectrum can be reduced as compared with the case where the same sequence is repeatedly used, and there is an effect that the peak of the received signal from the distance where the correlation is matched can be detected with high accuracy.

Also, the pseudo-random modulation signal generator has means for varying the time interval of the timing signal for generating the pseudo-random modulation signal. A randomly modulated signal can be generated.

Further, the pseudo-random modulation signal generator converts the pseudo-random modulation signal corresponding to the observation time per measurement for obtaining a sufficient S / N ratio into a modulation signal or timing based on a plurality of different pseudo-random sequences. Since the signal is constituted by a series of modulated signals having different time intervals, a pseudo-random modulated signal corresponding to an observation time per measurement for obtaining a sufficient S / N ratio is converted into a modulated signal based on a plurality of different pseudo-random sequences. Has the effect of reducing the amount of calculation in FFT.

[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 internal configuration diagram showing a pseudo-random signal generator according to Embodiment 1 of the present invention.

FIG. 4 is an explanatory diagram illustrating an example of a pseudo random modulation signal.

FIG. 5 is an explanatory diagram showing an example of a frequency spectrum of a received signal when a pseudo random modulation signal composed of four pseudo random sequences shown in FIG. 4 is used.

FIG. 6 is an explanatory diagram showing an example of a pseudo-random modulation signal using the same pseudo-random sequence repeatedly.

7 is an explanatory diagram showing an example of a frequency spectrum of a received signal when a pseudo random modulation signal obtained by repeating the B sequence shown in FIG. 6 four times is used.

FIG. 8 is an explanatory diagram showing a frequency spectrum of a received signal for one time of the B sequence shown in FIG. 6;

FIG. 9 is a configuration diagram showing a laser radar device disclosed in Japanese Patent Publication No. 64-2903.

FIG. 10 is a configuration diagram showing a coherent CW racer radar device disclosed in Japanese Patent Application Laid-Open No. 2-284087.

FIG. 11 is a configuration diagram showing a conventional coherent CW racer radar device when measuring a soft target.

FIG. 12 is an explanatory diagram showing a spectrum of a received signal when a uniform soft target is measured using a pseudo-random sequence having a sequence length of 127 bits in a conventional example.

[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, 61 optical coupler, 62 correlator, 63 variable delay, 64 signal processing device, 65 AD converter, 66 FFT circuit, 67
Signal extraction circuit, 68 sequence selection means, 69 pseudo random modulation signal generation means, 70 pseudo random sequence generation means, 71 timing generation means.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shuzo Wakadaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5F072 KK30 YY13 5J084 AA05 AA07 AB01 AB03 AB08 AD01 BA03 BA14 BA33 BB21 BB24 CA10 CA33 CA49 CA64 CA68 EA04

Claims (3)

[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. An optical antenna for irradiating the modulated laser light as transmission light toward a target (target) and receiving scattered light from the target (target); and locally arranging the other of the laser light branched by the branching unit. Mixing means for mixing light received from the optical antenna with light; and a photodetector for optically heterodyne-detecting the mixed light, and as an electrical component, a pseudo-random modulation for sending a modulation signal to the optical modulator. A signal generator; a time delay unit for giving a time delay to a part of the modulation signal of the pseudo-random modulation signal generator; and an output signal of the photodetector and the time delay unit. A correlator for taking the product of the time-delayed modulated signal, and a signal for obtaining physical information such as the distance and speed of a target by the strength and frequency of the output signal of the correlator and the delay time in the time delay A coherent laser radar device comprising: a processing unit; and the pseudorandom modulation signal generator has a function of switching and generating pseudorandom modulation based on a plurality of different pseudorandom sequences. 2. The coherent laser radar device according to claim 1, wherein said pseudo-random modulation signal generator has means for changing a time interval of a timing signal for generating a pseudo-random modulation signal. 3. The pseudo-random modulation signal generator converts a pseudo-random modulation signal corresponding to an observation time per measurement for obtaining a sufficient S / N ratio into a modulation signal or a timing based on a plurality of different pseudo-random sequences. 3. The coherent laser radar device according to claim 1, wherein the coherent laser radar device is configured by a series of modulated signals having different signal time intervals.