JPH1114752A - Laser radar device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Conventional calibration of a reception detector and calibration of a laser output monitoring detector are based on calibration data of the detector sensitivity acquired before the observation period, and are used during the observation period. The performance requirements for the change or deterioration of the detector sensitivity are severe, and when the sensitivity change or deterioration occurs, the concentration of the particles in the atmosphere, which is the observation result, deviates from the true value. A calibration device incorporated in a laser radar device includes a calibration laser extraction unit and a calibration laser introduction unit.
With. The laser beam 6 output from the laser generator 1 is extracted in the calibration laser extraction unit 13. The calibration laser introduction unit 14 transmits the calibration laser light 19 extracted by the calibration laser extraction unit 13 to the light collection unit 3 or the reception detector 4. The transmitted calibration laser beam is converted into an electric signal 12 by the reception detector 4 and used as calibration data.

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 mounted on a flying object such as an artificial satellite or an aircraft to observe the concentration of particles existing in the atmosphere, and more particularly to a laser generator built in the laser radar device. The present invention relates to an improvement of a calibration device for a detector output value and a reception detector sensitivity.

[0002]

2. Description of the Related Art A laser radar apparatus irradiates a laser beam to an object to be observed and receives the reflected light to sense the density and position of the object to be observed. When this laser radar device is mounted on an artificial satellite or aircraft to observe the concentration distribution of particles present in the atmosphere, the concentration is measured by the energy of the laser reflected light. Must be known during the observation period. In particular, when observing the earth's atmosphere from outer space mounted on a satellite, for example, 3
A change in the sensitivity of the reception detector over a long operation period such as one year affects the concentration data as the observation result.

On the other hand, with respect to laser light transmitted from a laser generator of a laser radar device, when the transmission output value changes, the laser reflected light from particles in the atmosphere changes. If the laser output value is not known, the density data will be inaccurate.

[0004] Conventional calibration of the sensitivity of the reception detector is as follows.
It is generally performed by the following two methods. (A) Before the observation by the laser radar device, the sensitivity calibration data is obtained by the detector alone. (B) Before observation by the laser radar device, a reference light source is irradiated to the laser radar device from outside the laser radar device to acquire calibration data of the sensitivity of the reception detector.

The processing of the observation result by the laser radar device is performed by associating the data of the output electric signal of the reception detector, which is the observation result, with the calibration data previously obtained by the method (a) or (b). Do. Therefore, in order to accurately determine the physical quantity such as the concentration of particles in the atmosphere, it is necessary that the calibration data of the receiver detector sensitivity before observation and the receiver detector sensitivity during the observation period by the laser radar have not changed or deteriorated. Required.

On the other hand, a change in the laser output value of the conventional laser generator can be measured by arranging a dedicated detector different from the reception detector at the laser output end during the observation period of the laser radar device. Have been done. The measurement value of the laser output at which the sensitivity of the dedicated detector changes becomes inaccurate. The dedicated detector for monitoring the laser output is also calibrated in the same way as the receiving detector, and the detector sensitivity calibration data before observation and the detector sensitivity during the observation period by the laser radar device have changed or deteriorated. It is necessary that there is not.

[0007]

As described above, the conventional method of calibrating the reception detector of the laser radar device and the dedicated detector for monitoring the laser output is based on the detection method acquired before the observation by the laser radar device. It is based on the calibration data of the detector sensitivity, and there is a problem that the performance requirement for the change or deterioration of the detector sensitivity during the observation period by the laser radar device becomes severe. Further, when the detector sensitivity changes or deteriorates, there is a problem that the concentration of particles in the atmosphere obtained by observation with a laser radar device deviates from the true value.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a calibration device capable of calibrating an output value and a detector sensitivity of a laser generator during an observation period by a laser radar device. To provide a laser radar device.

[0009]

According to a first aspect of the present invention, there is provided a laser radar device for extracting a part of a laser beam output from a laser generator, and a laser beam extracted by the calibration laser extracting unit. Having a calibration laser introduction unit to inject the laser light into the reception detector through the optical transmission path,
The laser beam injected from the calibration laser introduction unit is converted into an electric signal in the reception detector, and the electric signal is used as calibration data to calibrate the output value of the laser generator and the sensitivity of the reception detector. Is what you do.

A laser radar device according to a second aspect of the present invention is a laser radar device for extracting a part of a laser beam output from a laser generator, and a laser beam extracted by the calibration laser extracting unit. Having a calibration laser introduction unit for injecting into the focusing unit of the laser radar device through the transmission path, after condensing the laser light injected from the calibration laser introduction unit in the focusing unit, in the reception detector The output value of the laser generator and the sensitivity of the reception detector are calibrated by converting into an electric signal and using the electric signal as calibration data.

According to a third aspect of the present invention, in the laser radar device according to the first aspect of the present invention, in the configuration of the calibration laser extraction unit, the laser beam attenuator attenuates the extracted laser beam to a predetermined amplitude level before entering the calibration laser introduction unit. Is included.

The laser radar device according to a fourth aspect of the present invention uses an optical fiber cable as an optical transmission line of the calibration laser introducing section and makes the optical fiber cable a predetermined length to thereby propagate laser light. It is time-delayed and temporally separates the laser light generation time and the reception detector output time.

According to a fifth aspect of the present invention, in the laser radar device, the optical transmission path of the calibration laser introducing section is constituted by two optical fiber cables having different lengths, and the deterioration of the optical fiber cable is measured. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is an overall configuration diagram of a laser radar device having a built-in calibration device according to Embodiment 1 of the present invention. In FIG. 1, 1 is a laser generator, 2 is a calibration device,
Reference numeral 3 denotes a condensing unit, 4 denotes a reception detector, and 5 denotes particles in the atmosphere. The laser beam 6 from the laser generator 1 is injected into the calibration device 2, and the calibration laser beam 9 extracted by the calibration device 2.
Is injected into the reception detector 4, and the reception detector 4 photoelectrically converts the electric signal 12 into an electric signal 12. When calibrating the laser radar device including the focusing unit 3, the laser light extracted by the calibration device 2 is used as a calibration laser beam 10 instead of being injected into the reception detector 4 as a calibration laser beam 9. Inject into the focusing part.

Here, the principle of the calibration method using the calibration device built in the laser radar device according to the present invention will be described with reference to FIG. The observation laser beam 7 (output value is E) transmitted from the laser radar device is irradiated to the particles 5 in the atmosphere and scattered. The scattered laser light 8 is
The light received by the condensing unit 3 is converted into an electric signal 12 as a received light 11, injected into the reception detector 4, and converted into an electric signal 12 by the reception detector 4. Electric signal 12 output by reception detector 4
(Output value I) is given assuming that the concentration of particles in the atmosphere to be measured is β and the sensitivity of the reception detector 4 is R.

[0016]

(Equation 1)

## EQU1 ## In the equation (1), T _H is a term relating to the atmospheric transmittance of the transmitted laser light and the distance between the laser radar device and the particles in the atmosphere, and T _S is the transmittance of the light collecting unit. When the output value of the laser beam 6 generated by the laser generator 1 changes to E ′ due to a change in temperature or deterioration over time, and similarly, the sensitivity of the reception detector 4 also changes to R ′.
The electric signal I ′ output from the reception detector 4 is given by equation (2).

[0018]

(Equation 2)

When equation (2) is solved for β,

[0020]

(Equation 3)

## EQU1 ## If the change of the output value of the laser beam 6 to E ′ or the change of the sensitivity of the reception detector 4 to R ′ cannot be measured, it is assumed that these values remain the output value E and the sensitivity R. Then, the density β, which is the observation result of the laser radar device, deviates from the true value.

In the laser radar device incorporating the calibration device 2 according to the present invention, a part of the laser beam 6 from the laser generator 1 is extracted by the calibration device 2, and the extraction rate is k (in the calibration device, When the output value of the extracted laser light is kE ′), the electric signal J ′ output from the reception detector 4 by the calibration laser light 9 is

[0023]

(Equation 4)

## EQU1 ## Solving equation (4) for E ′ × R ′ and substituting it into equation (3) gives

[0025]

(Equation 5)

## EQU1 ## Therefore, in the calculation of the concentration β, the extraction rate k is known before the observation period by the laser radar device, and the electric signal J ′ is output from the electric signal output 12 from the reception detector 4 during the observation period by the laser radar device.
The change in output of the laser generator 1 and the change in sensitivity of the reception detector need not be measured. Further, when the calibration laser beam 10 is output from the calibration device 2 instead of the calibration laser beam 9 and injected into the focusing unit 3, the deterioration of the transmittance T _S of the focusing unit must also be calibrated. Becomes possible.

FIG. 2 shows the output of the laser beam 6 (FIG. 2A).
FIG. 4 is a timing chart of the electric signal 12 (FIG. 2B).
Pulsed laser light 6 output from laser generator 1
At approximately the same time t0 as (output value E ′), the calibration electric signal S1 (output value J ′) is output from the reception detector 4.
On the other hand, the laser light 8 scattered upon the particles 5 in the atmosphere is received with a time delay according to the distance between the laser radar device and the particles 5 in the atmosphere, and is output from the reception detector 4 as an observation electric signal S2. You. The calibration electric signal S1 and the observation electric signal S2 are obtained by separating the period from the reception start time t2 to the reception end time t3 of the observation electric signal S2 from the output period of the calibration electric signal S1 (period from t0 to t1). can do.

FIG. 3 is an internal configuration diagram of the calibration device 2 according to the first embodiment of the present invention. 3, reference numeral 13 denotes a calibration laser extraction unit, 15 denotes an optical fiber cover, 16 denotes a laser light attenuator incorporated as required, 14 denotes a calibration laser introduction unit, and 15 denotes an optical fiber cable. In FIG. 3, a calibration laser extracting unit 13 extracts a laser beam 6 output from the laser generator 1 by an optical fiber coupler 15. If the calibration laser light 18 extracted by the optical fiber coupler 15 is too large as the amount of light to be injected into the reception detector 4, it passes through the laser light attenuator 16 to obtain the calibration laser light 19 attenuated to a predetermined level. The calibration laser introduction unit 14 transmits the calibration laser light 19 from the calibration laser extraction unit 13 to the reception detector 4 as the calibration laser light 9 via the optical fiber cable 17. When the calibration is performed including the condensing unit 3, the calibration radar light 10 is transmitted to the condensing unit 3 instead of the calibrating laser light 9, and is condensed by the condensing unit 3. Output to The calibration laser light 9 or the calibration laser light 10 is output after being converted into an electric signal 12 by the reception detector 4.

By setting the length of the optical fiber cable 17 in the calibration laser introducing section 14 to a predetermined length, as shown in FIG. Start time t of the electric signal S1
It is possible to shift 0, and in this case, it is possible to separate the noise propagating from the laser generator 1 to the reception detector 4 and the calibration electric signal S1 during the laser generation period.

As shown in FIG. 5, the calibration laser introducing section 14 can be constituted by an optical fiber coupler 20 for branching the calibration laser beam 19, two optical fiber cables 21, and an optical fiber cable 22. . By setting the two optical fiber cables to have different lengths, a change over time in the attenuation rate of light propagation of the optical fiber cable (hereinafter, simply referred to as an attenuation rate) or when a laser radar device is used in outer space is generated. Radiation degradation or the like of the attenuation rate of the optical fiber cable can be measured. For convenience of explanation, the shorter one of the optical fiber cable 21 and the optical fiber cable 2
2 is the longer one. Calibration laser beam 23 (or calibration laser beam 25) output from optical fiber cable 21 and calibration laser beam 24 output from optical fiber cable 22
The (or calibration laser beam 26) is converted by the reception detector 4 to become a calibration electrical signal S1a (see FIG. 6) and a calibration electrical signal S1b (see FIG. 6). In FIG. 5, the calibration laser beams 25 and 26 are focused on the focusing unit 3. As shown in FIG. 6, the calibration electric signal S1a and the calibration electric signal S1b are generated with a time delay, and the output value is attenuated according to the length of the optical fiber cable. (The output value J′1 is larger than J′2 in FIG. 6). When a change in the attenuation factor depending on the length occurs in the optical fiber cable 21 and the optical fiber cable 22, the change in the output values J′1 and J′2 also depends on the length. By the difference between the changes of '1 and J'2,
The change in the attenuation rate of the optical fiber cable can be grasped.

[0031]

According to the first aspect of the present invention, during the observation period by the laser radar device, the output value of the laser generator and the sensitivity of the reception detector are obtained without acquiring the output value of the laser generator and the sensitivity of the reception detector, respectively. The sensitivity of the instrument can be calibrated.

According to the second aspect of the invention, during the observation period by the laser radar device, the output value of the laser generator, the transmittance of the condensing section, and the sensitivity of the reception detector are not obtained, respectively. Can be calibrated with respect to the output value, the transmittance of the light condensing unit, and the sensitivity of the reception detector.

According to the third aspect, the calibration laser light can be attenuated to a predetermined level before being input to the reception detector.

According to the fourth aspect, the propagation of the calibration laser light can be delayed in time, and the time when the laser light is generated and the time when the output of the receiving detector is output can be temporally separated.

According to the fifth aspect, it is possible to measure the deterioration of the optical fiber cable for transmitting the calibration laser light.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a laser radar device including a calibration device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing timings of a laser generator output of a laser radar device incorporating the calibration device of FIG. 1 and an electric signal output of a reception detector.

FIG. 3 is an internal configuration diagram of the calibration device of FIG. 1;

FIG. 4 is a diagram showing timings of a laser generator output and an electric signal output of a reception detector when an optical fiber cable has a predetermined length.

FIG. 5 is an internal configuration diagram of a calibration laser light introduction unit when two optical fiber cables are used.

6 is a diagram showing waveforms of a laser generator output and an electric signal output of a reception detector when the calibration laser light introducing unit of FIG. 5 is used.

[Explanation of symbols]

Reference Signs List 1 laser generator, 2 calibration device, 3 focusing unit, 4 reception detector, 5 particles in the atmosphere, 6 laser light, 7 observation laser light, 8 scattered laser light, 9, 10, 18, 1
9 Calibration laser light, 11 Received light, 12 Electric signal,
13 Calibration laser extraction unit, 14 Calibration laser introduction unit, 15, 20 optical fiber coupler, 16 laser light attenuator, 17, 21, 22 optical fiber cable, 23, 2
4, 25, 26 Calibration laser light.

Claims (5)

[Claims] A laser generator for irradiating the atmosphere with a laser beam, condensing the scattered laser beam, and receiving the laser beam by a reception detector to observe the concentration of particles in the atmosphere. A calibration laser extraction unit that extracts a part of the laser light output from the laser light source, and a calibration laser introduction unit that injects the laser light extracted by the calibration laser extraction unit into a reception detector through an optical transmission path. By converting the laser light injected from the calibration laser introduction unit into an electric signal in the reception detector and using the electric signal as calibration data, the output value of the laser generator and the sensitivity of the reception detector A laser radar device comprising a calibration device for calibrating the laser radar. 2. A laser radar device for irradiating the atmosphere with a laser beam, condensing the scattered laser beam, and receiving the same by a reception detector to observe the concentration of particles in the atmosphere. A calibration laser extraction unit for extracting a part of the laser beam, and a calibration laser introduction unit for injecting the laser beam extracted by the calibration laser extraction unit into a condensing unit of a laser radar device through an optical transmission path. Then, after condensing the laser light injected from the calibrating laser introduction unit in the condensing unit, the reception detector converts the laser light into an electric signal and uses the electric signal as calibration data to generate the laser light. A calibration device for calibrating the output value of the detector and the sensitivity of the reception detector. 3. The calibration laser extraction unit according to claim 1, further comprising a laser light attenuator that attenuates the extracted laser beam to a predetermined amplitude level before entering the calibration laser introduction unit. 3. The laser radar device according to any one of 2. 4. An optical transmission line of the calibration laser introduction unit,
An optical fiber cable, wherein the optical fiber cable has a predetermined length, thereby delaying the propagation of laser light in time, and separating a laser light generation time and a reception detector output time. A calibration device built in the laser radar device according to any one of claims 1 to 3. 5. The optical transmission line of the calibration laser introduction unit,
It consists of two optical fiber cables with different lengths,
5. The laser radar device according to claim 1, wherein a deterioration of an attenuation rate of light propagation in the optical transmission line is detected.