JPH0774828B2 - Laser radar - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laser radar, and more particularly to a laser radar mounted on an aircraft and used for detecting an obstacle on a route that interferes with operation.

[Conventional technology]

Conventionally, in this type of laser radar, the maximum detection distance and the monitoring viewing angle of the area to be monitored are set independently of each other regardless of the speed of the aircraft.

[Problems to be Solved by the Invention]

Generally, when the course of an aircraft is to be changed, the maximum course changeable angle ψ after a certain period of time Δt becomes smaller as the speed v of the body increases due to inertia.

FIG. 3 is an explanatory view showing the relationship between the machine speed and the maximum angle at which the course can be changed, and FIG. 4 is an explanatory view showing the relationship between the machine speed and the flight area.

In FIG. 3, Δt is the time from the time when the pilot visually recognizes the obstacle to the time when the pilot takes a safe maneuvering operation.

The flightable area of the aircraft within a certain time Δt depends on the speed of the airframe, and is as shown in FIG. Therefore, the fourth
There is a drawback in that an obstacle 104 indicated by a cross mark outside the conventional monitoring area 103 indicated by a dotted line cannot be detected.

Further, in order to detect these obstacles 104, it is necessary to monitor a region shown by a dashed line in FIG. 3, which requires a laser transmitter having a higher output, which makes the laser radar larger. There was a drawback.

Further, even if the obstacle 104a in the monitoring area 103 according to the conventional method shown by the dotted line is detected, depending on the speed of the aircraft shown in FIG. However, there is a drawback in that these obstacles do not interfere with the aircraft and do unnecessary monitoring.

Both of these drawbacks result from the fact that the area to be monitored is defined independently of the flightable area of the aircraft, ie the speed of the airframe.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a laser radar capable of effectively detecting an obstacle on the course of an aircraft by matching the area to be monitored with the flightable area of the aircraft.

[Means for Solving the Problems]

The laser radar of the present invention includes a laser transmitting unit that emits a laser beam at a constant repetition frequency, and a beam angle that controls the beam divergence angle of the laser beam output by the laser transmitting unit and the light receiving instantaneous viewing angle of the received laser beam. Control means, scanning control means for scanning and sending out laser light whose beam divergence angle is controlled by the beam angle control means within the monitoring viewing angle, and for receiving laser light reflected by an obstacle; and the beam angle A beam receiving angle of the laser beam and a beam divergence angle of the laser beam in inverse proportion to the speed of the aircraft. The instantaneous light-receiving viewing angle is controlled, and the scanning control means is configured to control the monitoring viewing angle in inverse proportion to the speed of the aircraft.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention. A laser radar of this embodiment includes a laser transmitter 1, a received light signal processor 2,
A beam expander 3, a scanning optical system 4, an optical system controller 5, a mirror 6 and a half mirror 7 are provided, and a speedometer 8 is also shown.

The laser light enters the beam expander 3 from the laser transmitter 1 through the half mirror 7, is given a predetermined beam divergence angle, and enters the scanning optical system 4. Scanning optics 4
Scans and transmits the incident laser light at a monitoring viewing angle of solid angle Φ.

Further, the received laser light reflected from the obstacle travels in the direction opposite to that of the transmitted laser light, enters the beam expander 3 via the scanning optical system 4, and the beam expander 3 instantaneously views the received laser light. The angle is controlled, and the light is incident on the light reception signal processing unit 2 via the half mirror 7 and the mirror 6 and is subjected to signal processing.

Since laser radars for aircraft must detect minute obstacles within a wide surveillance viewing angle (several tens of degrees), the beam divergence angle and the light-receiving instant viewing angle are set to angles (several minutes) as much as possible. And control each independently.
Generally, the light-receiving instantaneous viewing angle and the beam diverging angle are set to the same or several times, but in the present embodiment, the light-receiving instantaneous viewing angle is set to be the same as the beam diverging angle.

The optical system control unit 5 receives the aircraft speed data from the speedometer,
After the maximum detection distance to be monitored is calculated, the necessary beam divergence angle and monitoring viewing angle are calculated, and the beam expander 3 and scanning optical system are set and controlled to this calculated value.

Next, a method for setting the beam divergence angle, the light receiving instantaneous viewing angle θ and the monitoring viewing angle Φ of the optical system controller 5 in the present embodiment will be described with an example.

As described above with reference to FIG. 4, the flight area of the aircraft depends on the speed of the aircraft. Now, match the area to be monitored with this feasible area, and
Find the light-receiving instantaneous viewing angle θ and the monitoring viewing angle Φ.

FIG. 2 is an explanatory diagram showing the relationship between the monitoring viewing angle and the beam divergence angle in the embodiment of FIG.

First, since the maximum path changeable angle ψ of the airframe is inversely proportional to the speed v, the monitoring viewing angle Φ is determined by the following equation (1).

Φ = 2ψ∝1 / v (1) On the other hand, since the maximum detection distance is proportional to the aircraft speed v,
The area S ₁ to be monitored is constant regardless of the speed v of the airframe as shown in the following equation (2).

S ₁ ∝ (・ Φ) ² ∝ (v ・ 1 / v) ² = constant… (2) Letting the beam divergence angle and the light-receiving instantaneous viewing angle be θ, the laser beam cross-sectional area S _{2 at} the maximum detection distance is It can be calculated by the formula 3).

S ₂ = π (θ / 2) ² (3) The repetition frequency f of the laser transmitter 1 is given by the equation (2) (3)
It is determined by the formula (4) by dividing by the formula.

_{f = S 1 / S 2 =} S 1 / π (θ / 2) 2 ... (4) where constant repetition frequency f of the laser transmitting unit 1, and (2) since the S ₁ also is constant from the equation From equation (4), θ
Is constant.

Therefore, the beam divergence angle and the light-receiving instantaneous viewing angle θ are
It is calculated like the formula.

θ∝1 / ∝1 / v (5) Therefore, the monitoring viewing angle Φ, the beam divergence angle, and the light-receiving instantaneous viewing angle θ should be inversely proportional to the speed of the machine as shown in equations (1) and (5). The optical system control unit 5 executes such optical system control.

〔The invention's effect〕

As described above, the present invention controls the beam divergence angle of laser light emitted at a constant repetition frequency and the light-receiving instant viewing angle of the received laser light in inverse proportion to the speed of the aircraft, and scans the laser beam. By controlling the surveillance viewing angle in inverse proportion to the speed of the aircraft, it is possible to match the flight area of the aircraft with the surveillance area (the area set by the surveillance viewing angle and the surveillance distance), and as a result, the aircraft speed. As the beam speed increases, the beam divergence angle of the laser light and the light-receiving instantaneous viewing angle are narrowed down, so it is possible to monitor farther.Also, as the aircraft speed increases, the monitoring viewing angle narrows. The ratio of the laser light to the beam cross-sectional area is constant, and the number of laser light beam pulses (repetition frequency) required to scan the monitoring area is one. To be, therefore, use a small laser transmission unit of the average output can be effectively detect obstacles on the path of the aircraft, weight simplification of the apparatus can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a laser radar according to the present invention, and FIG. 2 is an explanatory diagram showing a relationship between a monitoring viewing angle and a beam divergence angle / light receiving instantaneous viewing angle in the embodiment of FIG.
The figure is an explanatory view showing the relationship between the machine speed and the maximum course changeable angle. FIG. 4 is an explanatory diagram showing the relationship between the aircraft speed and the flightable area. 1 ... Laser transmitter, 2 ... Receiving signal processor, 3 ... Beam expander, 4 ... Scanning optical system, 5 ... Optical system controller, 8 ... Speedometer.

Claims (1)

[Claims] 1. A laser transmitting means for emitting a laser beam at a constant repetition frequency, and a beam angle control means for controlling a beam divergence angle of the laser beam output by the laser transmitting means and a light receiving instantaneous viewing angle of the received laser beam. A scanning control means for scanning and sending out a laser beam whose beam divergence angle is controlled by the beam angle control means within a monitoring viewing angle and for receiving the laser light reflected by an obstacle; and the beam angle control means. And a light receiving processing means for receiving a received laser light having a light receiving instant viewing angle controlled by the light receiving processing means, the beam angle controlling means being in inverse proportion to the speed of the aircraft, the beam divergence angle of the laser light and the light receiving instant. A laser radar characterized in that the viewing angle is controlled, and the scanning control means controls the monitoring viewing angle in inverse proportion to the speed of the aircraft.