JP2001324563A - Laser radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser radar device that ensures the same range resolution as an existent device by means of a light source of a simple structure and has high reliability, and that can relax conditions for a line width and for the precision of frequency modulation and use a simpler light source. SOLUTION: The coherent laser radar device has a pulsed laser 34 for generating a laser pulse, a CW laser 40 for generating local light, a light transmission/reception system 37 for transmitting the laser pulse toward a target and receiving part of scattered light from the target, a light mixing means 38 for mixing the local light and the received light the transmission/reception optic system receives, a photodetector 39 for optical heterodyne detection of the mixed light, and a signal processor 42 for extracting information about the target from the detection signal. The pulsed laser 34 has a first frequency modulating means 35 for frequency modulation of the laser pulse, and the CW laser 40 has a second frequency modulating means 41 for such repeated frequency modulation of the local light as has one period of the same frequency modulation as that for the laser pulse.

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 and speed.

[0002]

2. Description of the Related Art There is a laser radar apparatus using a light wave (laser) as an apparatus for measuring physical information such as distance and speed of a target (hard target) such as an arbitrary vehicle or building. The laser radar device that obtains the target distance information includes a pulse method that obtains the target distance by the time from when the pulse laser light is transmitted to when the reflected scattered light from the target is received, and a modulated CW (Continuous Wave) laser light. There is a modulation CW method for transmitting. The pulse method includes a direct detection method and a coherent detection method. In the coherent detection method, target speed information can be obtained from Doppler shift of received light. As a modulation CW method, an FMCW (Frequency Modulated Control) for frequency-modulating a CW laser beam is used.
inuous Wave) method.

As a pulse method, a conventional example of a coherent detection method will be described. FIG. 5 is a configuration diagram of a coherent laser radar device disclosed in US Pat. No. 5,237,331 by Sammy W. Henderson et al., Which uses an injection seeding pulse laser device as a light source. 5, reference numeral 1 denotes a CW laser light source that oscillates at a single frequency, 2 denotes a first optical splitter, 3 denotes a frequency shifter, 4 denotes an injection seeding pulse laser, 5 denotes a beam splitter, and 6 denotes a quarter-wave plate. , 7 is a transmission / reception optical system, 8 is a scanning optical system, 9 is a first optical mixer, 10 is a first optical detector, 11 is a second optical splitter, 12 is a third optical splitter, 1
3 is a second light mixer, 14 is a second light detector, 15 is A
D converter, 16 is a signal processing device, 17 is a mechanism for adjusting the cavity length of the injection seeding pulse laser 4,
18 is a control circuit of the adjusting mechanism 17, 19 is a laser beam from the laser light source 1, 20 is a seed beam, 21 is a pulse laser beam, 22 is an optical axis of transmission and reception light, 23 is a transmission beam, 24 is a reception beam, and 25 is a reception beam. The local light 26 is a mixed light of the received light 24 and the local light 25 by the first optical mixer 9.

Next, the operation will be described. Single wavelength f
The laser light 19 from the laser 1 oscillating at ₀ is split into two by the first optical splitter 2, one of which is used as the local light 25, and the other is the laser light whose frequency is increased by the frequency f _IF by the frequency shifter 3. , As seed light 20 to the injection seeding pulse laser 4. Injection seeding pulse laser 4
Pulse oscillation of a single frequency (single wavelength) is performed in the axial mode having the frequency closest to the seed light 20. Pulse laser beam 2 from injection seeding pulse laser 4
1 is linearly polarized and is reflected by the beam splitter 5. After being converted into circularly polarized light by the 波長 wavelength plate 6, the transmission light 2 is transmitted through the transmission / reception optical system 7 and the scanning optical system 8.
Irradiation toward the target is performed as 3.

[0005] Scattered light from the target is received via a path opposite to that of the transmitted light. The received light 24 is linearly polarized by 90 ° from the polarization plane of the pulsed laser light 21 by the quarter-wave plate 6, passes through the beam splitter 5, and is guided to the first optical mixer 9. In the first optical mixer 9, the received light 2
4 and the local light 25 are mixed. The mixed light 26 is coherently detected by the first photodetector 10. The signal from the first photodetector 10 is sampled by the AD converter 15, and the signal processor 16 extracts the target distance from the time waveform of the intensity signal and the target velocity from the Doppler signal.

As described above, the injection seeding pulse laser 4 oscillates at a single frequency in the axial mode having the frequency closest to the seed light 20.
In order to obtain an accurate Doppler signal, it is necessary to monitor the frequency difference between the pulse laser light 21 and the local light 25. For this reason, the pulse laser light 21 and a part of the local light 25 are respectively extracted by the second and third optical splitters 11 and 12, and the two are mixed by the second optical mixer 13, and then the second light detection is performed. The coherent detection is performed by the detector 14. The sampling is performed by the AD converter 15 in the same manner as the reception light, and the signal processor 16 determines the frequency difference between the pulse laser light 21 and the local light 25. Assuming that the frequency of the local light 25 is f ₀ , the respective frequencies f _s , f _T , of the seed light, the pulse laser light, the reception light, the frequency monitor signal, and the reception signal
f _R , f _M , and f _sig are represented by the following equations.

[0007]

(Equation 1)

Here, f_IFIs the intermediate frequency, δf is the pulse
Frequency difference between laser light and seed light, f _dIs the target Doppler
-Frequency and the received signal f_sigAnd frequency monitor signal f_M
Can be obtained by taking the difference

The distance resolution in the pulse method is determined by the pulse width of the transmission laser pulse. Considering the strength of the S / N ratio of the received signal and the fluctuation of the signal intensity due to the target speckle effect, the distance accuracy is about the same as the distance resolution. Conceivable. The distance resolution ΔR of the pulse method is expressed by the following equation.

[0010]

(Equation 2)

Where τ is the pulse width of the laser pulse, c
Is the speed of light.

As is clear from equation (2), the distance resolution Δ
In order to reduce R and perform highly accurate measurement, the width τ of the transmitted laser pulse may be reduced. To obtain 1 m as the value of the distance resolution, the pulse width τ needs to be 6.6 ns. As a high-output pulse laser oscillator, a Q-switched pulse laser oscillator that normally obtains a laser pulse by controlling the Q of a resonator is used. High gain is required to obtain a laser pulse with a narrow pulse width by using a Q-switched pulse laser oscillator. A four-level Nd laser (oscillation wavelength 1 μm), which is a four-level laser capable of obtaining a high gain, has achieved a pulse width of several ns, but Er and Ho lasers oscillating at an eye-safe wavelength (> 1.4 μm). And t
The m-system laser is a three-level laser having a low gain, and it is difficult to achieve a pulse width of several ns. Therefore, it is necessary to increase the pump power in order to increase the gain or to improve the pump efficiency. It requires a more complicated configuration. Further, when the pulse width is reduced, the frequency band of the received signal is widened, so that it is necessary to increase the peak power in order to secure the same SN ratio.

Therefore, a high-gain Q-switched pulse laser oscillator is required to obtain a high distance resolution by the pulse method, so that the laser has a complicated structure. In addition, since the peak power is increased, there is a high possibility that optical components used in the apparatus are burned, and there is a problem that reliability is reduced and expensive components having high laser power resistance need to be used.

In the coherent detection system,
When the distance resolution is reduced by reducing the pulse width, there is a problem that the speed resolution increases. This is the distance resolution ΔR
This is because there is the following relationship between the speed resolution and the speed resolution Δv.

[0015]

(Equation 3)

Here, λ is the wavelength of the laser pulse.

Next, a conventional example of the FMCW system which is a modulation CW system will be described. Figure 6 shows A by Christer J. Karlson et al.
pplied Optics (Vol. 38, No. 15, pp33766-3386,
1999) is a configuration diagram showing an FMCW type laser radar device disclosed in US Pat. 6, reference numeral 27 denotes a semiconductor laser (hereinafter referred to as an LD); 28, a power supply; 29, an FM modulation circuit; 30, an optical coupler; 31, a transmission / reception optical system; 32, a photodetector; .

The operation of the configuration shown in FIG. 6 will be described.
The CW laser light from the LD 27 oscillating in a single mode is
The light passes through the optical coupler 30 and is emitted from the transmission / reception optical system 31 toward the target. Part of the scattered light from the target is
1 and received by the photodetector 32 through the optical coupler 30.
Leads to. In the transmission / reception optical system 31, a part of the transmission light is reflected by, for example, Fresnel reflection at the emission end of the optical fiber. The reflected light reaches the photodetector 32 as local light via the optical coupler 30 in the same manner as the received light. The received light and the local light are subjected to heterodyne detection by the photodetector 32. The signal received from the photodetector 32 is frequency-analyzed by the signal processing device 33 to extract target distance and speed information.

Here, the CW laser light from the LD 27 is
The frequency is modulated by the FM modulation circuit 29. FIG. 7 shows an example of frequency modulation. The CW laser beam has a period tm of 2
The frequency is modulated to an equilateral triangular wave. The frequency changes of the transmission light, the local light and the reception light at this time are as shown in FIG.

FIG. 8 shows the target distance and speed from the received signal.
Received light, local light and
And the time change of the frequency of one cycle of the received signal. Receiving
The frequency modulation of light has a lower
Round trip time t_rMinutes late. Because of this, the local light
And the frequency modulation function of the received light have the same slope.
The received signal, which is the beat signal between the received light and the local light.
The signal is a constant frequency f_rhave. (Fixed (stationary) goal
Time) constant frequency f_rIs obtained by the frequency modulation
One cycle time is t_mThen the modulation function has a positive slope
T_r~ T _m/ 2, t at negative slope_m/ 2 + t_r~ T_mso
is there. If the target is a moving target (has a speed
), The Doppler frequency f_dIs the frequency of the received light
Because of the number, the resulting beat frequency is
F at positive slope_r-f_d, With a negative slope_r+ f_dWhen
Become. From the beat frequency when both the positive and negative slopes, f_rYou
And f_dCan be requested. This allows the target distance
Release and speed information can be obtained.

The maximum measuring distance R _max is in theory a distance determined by the condition t _r = t _m / 2 there is a time modulation function of the local light and the received light have the same slope, the measurement time It is not realistic because it is close to 0 as much as possible. Here, providing the condition that the measured time is 50% duty, the maximum measuring distance R _max and the frequency f _r and the distance resolution [Delta] R, the frequency resolution df _r is determined as follows.

[0022]

(Equation 4)

Here, Δf is the modulation frequency width, f _{m is the} modulation frequency, and df is the slope of the modulation function.

[0024] The range resolution ΔR is the modulation frequency width Delta] f, it does not depend on the modulation frequency f _m. On the other hand, the frequency resolution d
Since f _r is expressed by the following equation, the maximum measuring distance R _max increases, the frequency resolution df _r decreases.

[0025]

(Equation 5)

This has a great effect not only because the measurement time becomes longer but also the line width of the light source and the accuracy of frequency modulation need to be lower than the frequency resolution. ΔR = 1
m, the measurement distance range, that is, the maximum measurement distance is 1 km
The accuracy of the line width and frequency modulation of the light source is 300
If the maximum measurement distance is 10 km at 30 kHz, 30 kHz is required. Since the line width of a normally available LD is about 1 MHz, it cannot be used under the above conditions.

[0027]

As described above, in a conventional laser radar apparatus using a pulse method, a pulse having a short pulse width is required to obtain a high distance resolution. For this reason, a high-gain Q-switched pulse laser oscillator is required, and the laser has a complicated configuration. Further, since the peak power is increased, there is a high possibility that optical components used in the apparatus are burnt, and there is a problem that reliability is reduced and expensive components having high laser power resistance need to be used.
Further, in the pulse method using coherent detection, since the distance resolution ΔR and the velocity resolution Δv are in inverse proportion, there is a problem that the velocity resolution increases when the pulse width is reduced and the distance resolution is reduced. .

On the other hand, in the conventional FMCW system, in order to reduce the distance resolution and increase the measurement distance range, high conditions are required for the line width of the light source and the accuracy of frequency modulation, and such as the LD. There is a problem that a light source that is inexpensive and easy to modulate cannot be used.

The present invention has been made in view of the above points, and provides a highly reliable laser radar device in which a light source having a simpler structure can be used to obtain the same distance resolution as compared with the conventional pulse method. The purpose is to: It is another object of the present invention to provide a laser radar device in which conditions for line width and frequency modulation accuracy are relaxed as compared with the conventional FMCW method, and a simpler light source can be used.

[0030]

A laser radar device according to the present invention comprises: a laser pulse generating means for generating a laser pulse; a local light generating means for generating local light;
The laser pulse from the laser pulse generating means is transmitted toward the target, the light transmitting / receiving means for receiving a part of the scattered light from the target, the local light from the local light generating means and the light transmitted / received by the transmitting / receiving optical means. Light mixing means for mixing the received light, optical detection means for optical heterodyne detection of the mixed light mixed by the light mixing means, and signal processing means for extracting target information from a signal from the light detection means. In the coherent laser radar device having the above, the laser pulse generation means has first frequency modulation means for frequency-modulating the laser pulse, and the local light generation means has the same frequency as the laser pulse from the laser pulse generation means. A second frequency modulating means for applying repetitive frequency modulation having one cycle of modulation to the local light. .

Further, the first frequency modulating means is characterized by alternately modulating a plurality of linear frequency modulations having different slopes for each laser pulse.

The laser pulse generating means and the local light generating means are a CW laser oscillating in a single mode, a modulating means for frequency modulating the CW laser light from the CW laser, and a CW laser light. It is characterized by comprising a light splitting means for dividing the light into two, and an optical switch means for extracting one of the CW laser lights split by the light splitting means as pulse light.

Further, an optical amplifier is provided between the optical branching means and the optical transmitting / receiving means.

Further, the optical amplifier is an optical fiber amplifier.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram showing a laser radar device according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 34 denotes a pulse laser oscillating in a single mode; 35, a first frequency modulating unit; 36, a transmitting and receiving light separating unit; 37, a transmitting and receiving optical system;
9 is a photodetector, 40 is a CW laser oscillating in a single mode, 41 is a second frequency modulating means, 42 is a signal processing device, and 43 is a frequency modulation control circuit.

Next, the operation will be described with reference to the drawings. The pulse laser 34 oscillates a single mode transmission laser pulse. The first frequency modulation means 35 frequency-modulates the optical frequency of the laser pulse within the pulse according to a control signal from the frequency modulation control circuit 43. As means for modulating, a means for modulating the cavity length of the pulse laser 34, modulating the pump power, or directly modulating the laser pulse can be considered. The transmission laser pulse passes through the transmission / reception light separating means 36 and is transmitted / received by the transmission / reception optical system 37.
Irradiates toward the target. A part of the scattered light from the target is received by the transmission / reception optical system 37 and the transmission / reception light separation means 36
The received light is sent to the optical mixer 38 after being separated from the transmission laser pulse.

On the other hand, a CW laser 4 oscillating in a single mode
0 is C having the optical frequency Δfs with respect to the laser pulse.
Oscillates W laser light. The second frequency modulating means 41 includes:
The repetitive frequency modulation in which one cycle is the same frequency modulation as that of the laser pulse of the first frequency modulation means 35 is given to the optical frequency of the CW laser light. As means for the second frequency modulating means 41 to modulate the CW laser light, means for modulating the resonator length of the CW laser 40, modulating the pump power, or directly modulating the CW laser light can be considered. The modulated CW laser light is supplied to the optical mixer 38 as local light.

The frequency modulation control circuit 43 converts a control signal for frequency modulation by alternately switching the transmission laser pulse light repeatedly transmitted from the pulse laser 34 with two or more types of modulation functions having different slopes. Modulation means 3
Send to 5. Further, a control signal is sent to the second frequency modulating means 41 so that the CW laser light is frequency-modulated in synchronization with the first frequency modulating means 35. The optical mixer 38 mixes the received light and the local light and sends the mixed light to the photodetector 39. The photodetector 39 performs optical heterodyne detection, and sends the received signal to the signal processing device 42. The signal processing device 42 analyzes the time and frequency of the received signal to obtain target distance and speed information.

In the method according to the present invention, the transmission laser light is
This is an FM pulse method, which is an FMCW method using pulse light for a period. FIG. 2 is a time conceptual diagram of the intensity and frequency of the transmission light and the local light in the FMCW method and the FM pulse method. In the FMCW system, the transmission light and the local light are CW light in which the intensity is constant and the frequency of the triangular wave is modulated. On the other hand, in the FM pulse system, the transmission light is one cycle of the frequency modulation of the triangular wave in the FMCW system. It is characterized by two pulses divided for each hypotenuse. The local light is a sawtooth frequency-modulated light that is synchronized with each transmission light pulse and has the same frequency waveform as the transmission light. The distance resolution in the ordinary pulse method is about the pulse width, but the distance resolution can be improved by using the FMCW method.

The frequency fr or fr 'corresponding to the target distance in the range bin is determined from the frequency of the signal of the time gate (range bin) corresponding to the first pulse and the second pulse. Further, since the Doppler frequency df is also obtained at the same time, target speed information can be obtained. FIG.
4 shows a relationship between a pulse reception signal and a time gate. Although the value of the frequency and the time shape of the signal differ depending on the value of dt, it can be seen that there is a constant frequency section at least during τ / 2. The above frequency can be obtained by turning off the time gate every τ / 2 and performing signal processing. From this frequency and the frequency obtained from the same time gate of the second pulse, the frequency f corresponding to the target distance in the range bin
r or fr 'and the Doppler frequency df can be determined.

The relationship between fr and fr 'and the target distance R' in the range bin is expressed by the following equation.

(Equation 6)

Here, fm is the modulation frequency, and c is the speed of light.

The relationship between the frequency resolution df _r and the distance resolution ΔR is expressed by the following equation.

[0044]

(Equation 7)

Since the frequency resolution df _r is equal to the receiver band B of the apparatus, the following equation is obtained.

[0046]

(Equation 8)

Therefore, the following equation is obtained.

(Equation 9)

If the FM pulse method of the present invention is used, for example, the maximum measurement distance is 10 km, and the distance resolution ΔR =
When the distance is 1 m, it is possible to construct a device with a transmission laser pulse width τ = 1 μs and a frequency resolution df _r = 2 MHz. This means that the pulse width is τ = 6.7 ns
Is required, the conditions for the peak power and pulse width of the laser pulse are relaxed, and a pulse laser having a simpler configuration can be used. The required frequency resolution is determined by the pulse width and the distance resolution. Therefore, regardless of the maximum measurement distance, the frequency resolution does not change to df _r = 2 MHz under the above conditions. Therefore, as compared with the FMCW method, the conditions of the line width of the light source and the accuracy of the frequency modulation are relaxed, and a simpler light source can be used. That is, there is a possibility that an inexpensive and easily modulated light source such as an LD can be used.

In the FM pulse system according to the present invention, the transmission laser pulse is frequency-modulated, and the frequency modulation in which local light is applied to the transmission laser pulse is performed in one cycle, so that the repetition frequency modulation is performed. As compared with the above, a light source having a small peak power and a wide pulse width can be used to obtain the same distance resolution, so that a pulse laser having a simpler configuration can be used and the reliability of the apparatus can be improved. Also, compared to the conventional FMCW method, the line width and frequency modulation accuracy required for the light source do not become strict even if the maximum measurement distance increases, so that there is an effect that a simpler light source can be used, and such an effect as LD There is a possibility that a cheap and easy-to-modulate light source can be used. further,
Since the transmission laser pulse light is alternately switched by two or more types of modulation functions having different inclinations to perform frequency modulation, there is an effect that not only a target distance but also velocity information can be obtained.

Embodiment 2 FIG. 4 is a configuration diagram showing a laser radar device according to Embodiment 2 of the present invention. 4, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. As a new code,
Reference numeral 44 denotes a reference light source having frequency modulating means and outputting a single-mode frequency-modulated CW laser beam; 45, an optical coupler as an optical splitter; 46, an optical switch; and 47, an optical fiber amplifier. .

Next, the operation will be described with reference to the drawings.
The basic operation is the same as in the first embodiment. Reference light source 4
4. The functions of the pulse laser 34, the CW laser 40, and the first and second frequency modulating units 35 and 41 in the first embodiment are realized by the optical coupler 45 and the optical switch 46. The reference light source 44 outputs frequency-modulated CW laser light such as the local light shown in FIG. 2 by the frequency modulation control circuit 43. That is, it is a CW laser beam repeatedly modulated by a combination of two or more sawtooth frequency modulations with a period τ having different slopes. The CW laser beam from the reference light source 44 is split into two by an optical coupler 45. One of the branched CW laser lights is sent to the optical mixer 38 as local light. The optical switch 46 cuts out one cycle of the sawtooth frequency modulation from the other branched CW laser beam as a laser pulse in accordance with a control signal from the frequency modulation control circuit 43. The cut laser pulse is amplified by an optical fiber amplifier 47 as transmission laser light, passes through a transmission / reception light separation unit 36, and is emitted from a transmission / reception optical system 37 toward a target.

As described above, the functions of the pulse laser, the CW laser, and the first and second frequency modulation means are changed to the reference light source 4.
4. Since the laser light source and the frequency switch are constituted by the optical coupler 45 and the optical switch 46, the laser light source and the frequency modulation means can be integrated into one, and the effect described in the first embodiment can be realized with a simpler configuration. Furthermore, since the transmission laser light is amplified using the optical amplifier, the output required for the reference light source can be reduced, and there is an effect that a light source having a low output can be used. Thus, the reference light source has an effect that an LD that is inexpensive and can easily perform frequency modulation with an injection current can be used.
Next, by configuring the optical amplifier with an optical fiber amplifier, not only the above effects can be achieved easily, but also the arrangement of light in the device can be configured with an optical fiber, which facilitates assembly and component arrangement of the device. This makes it possible to construct a device that is strong against environmental conditions such as vibration.

[0053]

As described above, according to the present invention, the FM
In the pulse method, the transmission laser pulse is frequency-modulated, and the local light is subjected to repetitive frequency modulation in which the frequency modulation given to the transmission laser pulse is one cycle. Therefore, compared to the conventional pulse method, the same distance resolution is obtained. Since a light source having a small peak power and a wide pulse width can be used to obtain the pulse laser, a pulse laser having a simpler configuration can be used and the reliability of the apparatus can be improved. Also, compared to the conventional FMCW method, the line width and frequency modulation accuracy required for the light source do not become strict even if the maximum measurement distance increases, so that there is an effect that a simpler light source can be used, and such an effect as LD There is a possibility that a cheap and easy-to-modulate light source can be used.

Further, since the frequency modulation is performed by alternately switching the transmission laser pulse light with a plurality of linear frequency modulations having different inclinations, not only the target distance but also velocity information can be obtained.

Further, since the functions of the pulse laser, the CW laser, and the first and second frequency modulation means are constituted by the CW laser, the modulation means and the optical switch means, the laser light source and the frequency modulation means can be integrated into one. There is an effect that can be realized with a simpler configuration.

Further, since the transmission laser light is amplified using the optical amplifier, the output required for the CW laser can be reduced, and there is an effect that a light source having a low output can be used. Thus, the CW laser has an effect of using an LD which is inexpensive and can easily perform frequency modulation with an injection current.

Further, by configuring the optical amplifier with an optical fiber amplifier, not only the above-mentioned effects can be easily achieved, but also the arrangement of light in the device can be configured with an optical fiber. There is an effect that the device can be easily arranged and a device that is strong against environmental conditions such as vibration can be configured.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram of the intensity and frequency of transmission light and local light in the FMCW method and the FM pulse method.

FIG. 3 is an explanatory diagram showing a relationship between a received signal and a time (range) gate.

FIG. 4 is a configuration diagram showing a laser radar device according to Embodiment 2 of the present invention.

FIG. 5. US Patents 5,2 by Sammy W. Henderson et al.
37, which is a configuration diagram of a coherent laser radar device using an injection seeding pulse laser device as a light source.

FIG. 6 Applied Optic by Christer J. Karlson et al.
FIG. 1 is a configuration diagram showing an FMCW laser radar device disclosed in s magazine (Vol. 38, No. 15, pp33766-3386, 1999).

FIG. 7 is an explanatory diagram illustrating an example of frequency modulation.

FIG. 8 is an explanatory diagram showing a time change of the frequency of one cycle of the reception light, the local light, and the reception signal in order to explain a method of obtaining a target distance and a speed from the reception signal.

[Explanation of symbols]

Reference Signs List 1 CW laser light source, 2 first optical splitter, 3 frequency shifter, 4 injection seeding pulse laser, 5 beam splitter, 6 1/4 wavelength plate, 7 transmitting / receiving optical system, 8 scanning optical system, 9 first light Mixer, 10
1st optical detector, 11 2nd optical splitter, 12 3rd
13 optical splitter, 13 second optical mixer, 14 second photodetector, 15 AD converter, 16 signal processing device, 17
Adjustment mechanism of cavity length of injection seeding pulse laser 4, 18 Control circuit of adjustment mechanism 17, 19
Laser light from laser light source 1, 20 seed light, 21
Pulse laser light, 22 optical axis of transmission / reception light, 23 transmission light, 24 reception light, 25 local light, 26 mixed light of reception light 24 and local light 25 by the first optical mixer 9,
27 semiconductor laser (LD), 28 power supply, 29 FM
Modulation circuit, 30 optical coupler, 31 transmission / reception optical system, 32
Photodetector, 33 signal processing device, 34 pulse laser, 35 first frequency modulation means, 36 transmission / reception light separation means, 37 transmission / reception system, 38 light mixing means, 39 photodetector, 40 CW laser transmitting in single mode , 41
Second frequency modulation means, 42 signal processing device, 43 frequency modulation circuit, 44 reference light source, 45 optical coupler, 46
Optical switch, 47 Optical fiber amplifier.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takayuki Yanagisawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Mitsubishi Electric Corporation (reference) 5J084 AA05 AA07 BA03 BB16 BB31 CA03 CA08 EA04

Claims (5)

[Claims] 1. A laser pulse generating means for generating a laser pulse, a local light generating means for generating local light, a laser pulse from the laser pulse generating means is transmitted toward a target, and scattered light from the target is transmitted. An optical transmitting / receiving unit that receives a part of the light; a light mixing unit that mixes the local light from the local light generating unit with the reception light received by the transmission / reception optical unit; In a coherent laser radar device having a light detection means for heterodyne detection, and a signal processing means for extracting target information from a signal from the light detection means, the first laser pulse generation means performs frequency modulation of a laser pulse. Frequency modulating means, wherein the local light generating means has the same frequency as the laser pulse from the laser pulse generating means. The laser radar apparatus characterized by having a second frequency modulation means for providing a repetition frequency modulation to one cycle adjustment locally light. 2. A laser radar apparatus according to claim 1, wherein said first frequency modulation means performs modulation control alternately with a plurality of linear frequency modulations having different slopes for each laser pulse. apparatus. 3. The laser radar device according to claim 1, wherein said laser pulse generating means and said local light generating means output a CW laser oscillating in a single mode, and a CW laser light from said CW laser. It is characterized by comprising a modulating means for modulating the frequency, an optical splitting means for splitting the CW laser light into two, and an optical switch means for extracting one of the CW laser lights split by the optical splitting means as pulse light. Laser radar device. 4. The laser radar device according to claim 3, wherein an optical amplifier is provided between the optical branching unit and the optical transmitting / receiving unit. 5. The laser radar device according to claim 4, wherein said optical amplifier is an optical fiber amplifier.