JPS58142271A - Transmission laser beam measurement of laser radar - Google Patents

Abstract

PURPOSE:To measure the beam diameter and the expansion angle of a transmission laser beam accurately by determining the beam diameter of a laser beam to be measured from the value of an angle of inclination remotely detecting the expansion of a reflected light from a long and narrow reflecting target arranged at the angle of inclination on the axis of the laser beam to be measured. CONSTITUTION:A long and narrow target 14 is set at a distance rho from a laser radar 10 inclined at an angle theta with respect to a laser beam 13 to be measured. A reflected light 15 from the target 14 is received with a receiving optical system 16 of the laser radar 10 and detected with a detector 17. An oscilloscope 18 traces the reflected light 15 with the output of the detector 17. When the width (diameter) of the target 14 is represented by (a) and the waveform of the reflected light 15 observed on the oscilloscope 18 is large in the expansion, the diameter (d) of the laser beam 13 at the distance rho is given by d=(C/2)(t-tau)tantheta. Therefore, if the pulse width tau of a transmission laser beam 13 and the set angle theta of the target 14 are defined, the diameter (d) of the transmission laser beam 13 can be determined at the distance rho by measuring the expansion range (t) of the reflected wave 15 with the oscilloscope 18 (where (c) is the velocity of light).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring a transmitted laser beam of a laser radar device, and more specifically, a method for measuring a transmitted laser beam of a laser radar device using a pulsed laser such as a satellite laser radar device. Regarding m-orthotropy.

In laser radar devices such as satellite laser ranging devices,
A means to measure and calibrate the diameter and divergence angle of the transmitted laser beam is required for system operation and maintenance.However, the transmitted laser beam of radar radar equipment has a large diameter and its divergence angle. It has the characteristic of being narrow. This is due to the following reasons. That is, the transmitting laser beam of a laser radar device is normally emitted through an optical system called a transmitting telescope or a collimator. The purpose of this is to appropriately set and control the p-angle of the beam output from the laser oscillator. Generally, the transmitted laser beam diameter Fi is compared to the beam diameter output from the laser oscillator. The image is enlarged several times to several tens of times. 1+, the spread angle of the transmitted laser beam is generally intended to be narrower than the beam output from the laser oscillator. Therefore, the transmitted laser beam emitted from the laser radar device has a large diameter and a narrow divergence angle, and therefore it is not easy to measure the diameter and divergence angle of the transmitted laser beam. Therefore, it is desired to develop a method for measuring the transmitted laser beam of a laser radar device with high precision.

As a conventional method for measuring a transmitted laser beam, it is known to measure the strongly variable power distribution in a cross section perpendicular to the beam axis of the transmitted laser beam, and calculate the diameter of the transmitted laser beam from this measurement value. These conventional methods move and scan pinholes, slits, knives, etc. at right angles to the beam axis and measure changes in the passing power at this time. The drawback is that it requires a moving scanning mechanism and a large-diameter condensing optical system used to measure the power of the passing beam.

In addition, since the spread of the transmitted laser beam is narrow at 9 angles,
In order to accurately determine the angle of divergence, it is necessary to measure the beam diameter from a sufficiently far distance, and the large device described above must be transported and measured, which requires a great deal of time and effort. .

The present invention has been made in view of the drawbacks of the prior art, and provides a transmitting laser beam of a laser radar device that can easily and accurately measure the beam diameter and divergence angle of a transmitting laser beam of a laser radar device such as an artificial satellite laser ranging device. The purpose of the present invention is to provide a measurement method for a transmitted laser beam of a laser radar device, which utilizes the original functions of the laser radar device and uses the measurement target instead of a pinhole, slit, knife, etc. An elongated reflective target is placed at an oblique angle to the beam axis of the laser beam, and the spread of the reflected light from this reflective target is remotely detected. The present invention is characterized in that the beam diameter of the laser beam to be measured is determined from the value of the oblique angle of the target with respect to the laser beam to be measured. It should be noted that the method of the present invention is highly effective when applied to pulsed lasers with short pulse widths that can be used in satellite laser ranging devices.5411
There is 1.

The present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings. In the accompanying drawings, 10 is a laser radar device that outputs a laser beam 13 to be measured, 114 is a laser oscillator, 12 is a laser transmission optical system, and 13 is a laser transmission optical system 12. A laser beam with a pulse width emitted from Reference numeral 14 denotes an elongated target installed at a distance ρ from the laser radar device 10 and inclined at an angle gl with respect to the laser beam 13 to be measured. 15 is reflected light from the target 14, 16 is a receiving optical system 1) of the laser radar device 10, and 17 is a detector. Furthermore, 1g is an oscilloscope p, which traces the reflected light 15 with the output of the detector 17.
3 is the diameter of d, and the laser beam to be measured 13 and the target 1 are
4 is the length in the axial direction of the beam, and the condition of ) τ is satisfied. However, C is the speed of light. In this case, the reflected light 1 observed on the oscilloscope 18
The spread of the waveform of No. 5, t, is 0 t-y+τ ・・・・・・・・・・・・・・・・・・
・・・・・・・・・(11t, transmission laser beam 13
The diameter d is expressed by the following equation (2).

dshunA*tan# ・・・・・・・・・・・・・・・
・・・・・・・・・・・・(21 Equation (1) and Equation (2)
From the formula, the diameter d of the transmitted laser beam 13 can be determined by the following formula (3).

d-2(i-τ)・is dragon θ・・・・・・・・・・・・
...+3) As is clear from the above explanation, if the pulse width τ of the transmitted laser beam 13 and the installation angle θ of the target 14 are known, the spread width t of the reflected wave 15 can be calculated using the oscilloscope 1.
By measuring at 8, the diameter d of the transmitted laser beam 13 at the distance ρ can be easily determined. The beam diameter of the laser beam to be measured can be easily measured by simply placing the target at two or more locations at the true distance. By measuring the beam diameter of the laser beam to be measured at each position, it is possible to obtain it with high precision.In this case, the target can be of simple shape and structure, so it is very easy to install multiple targets. It has this effect.

[Brief explanation of the drawing]

The attached drawings are diagrams showing an embodiment of a method for measuring a transmitted laser beam of a laser radar device according to the present invention. 1O... Laser radar device, 11... Laser oscillator, 12...
- Laser transmission optical system, 13... Laser beam to be measured,
14...Target, 15...Reflected light, 16...Reception optical system, 17...Detector, 18...Oscilloscope. Agent Patent Attorney Masami Akimoto

Claims (1)

[Claims] Column 511 A reflective target in an elongated shape, which is arranged at an oblique angle with respect to the laser beam and has a width smaller than the beam diameter of the 911III constant laser beam, is arranged on the 511 constant laser beam, and the laser beam to be measured from the wrinkled reflective target is remotely detecting the spread of the reflected light, and determining the beam diameter of the laser beam to be measured from the 910 value of the spread of the reflected light, the pulse width of the laser beam to be measured, and the oblique angle value of the reflection target with respect to the laser beam to be measured. A method for measuring a transmitted laser beam of a laser radar device, characterized by: