JPH0442785Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a radar beam scanning device that scans a radar beam over a monitoring area.

PRIOR ART Recently, systems have been developed that equip cars with radar to detect obstacles such as vehicles traveling in front and activate automatic braking systems. It is difficult to have the radar beam scan only in a predetermined monitoring area in front of the vehicle, and the beam is scanned outside the predetermined monitoring area, resulting in the detection of objects that do not pose an obstacle to the vehicle's movement. There is.

Therefore, in conventional radars, unnecessary object detection signals are removed by processing the received signals, resulting in a complex radar configuration.

Purpose This invention was made taking the above points into consideration.
An object of the present invention is to provide a radar beam scanning device that is optimal for a vehicle-mounted radar and is capable of beam scanning only to a predetermined monitoring area where objects need to be detected.

Configuration In order to achieve the objective, the present invention is designed to scan the beam by reflecting the beam emitted from the transmitter by a rotating reflector, and the curvature of the beam reflecting surface of the rotating reflector is changed. By doing so, the beam opening degree is designed to increase as the beam reflected by the rotating reflector deviates from a predetermined monitoring area where an object is to be detected.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 shows an example of the configuration of a radar using a laser beam. The laser beam LB emitted from the light transmitter 2 of the radar transceiver 1 is reflected on the mirror surface of a rotating polygon mirror 4 rotated at a constant speed by a motor 3. The radar transmitter/receiver 1 receives the reflected beam LB' from the object O in the monitoring area repeatedly and scans the monitoring area in a predetermined direction repeatedly.
Detection is performed. 6 in the figure is
This is a motor driver that controls the drive of the motor 3 in accordance with the motor rotation synchronization signal SYNC given from the radar transceiver 1.

In the present invention, in such a radar, the beam is scanned by changing the curvature of each mirror surface 41 of the rotating polygon mirror 4, as shown in the plan view of the mirror surface 41 portion in FIG. The convex mirror has a curved surface in which the radius of curvature decreases from the center of the mirror surface 41 toward the ends in the horizontal plane. In FIGS. 1a, b, and c, arrows indicate the direction of rotation of the mirror surface 41.

FIG. 2 shows a front view of the portion of the mirror surface 41 that is irradiated with the laser beam LB.

However, when the mirror surface 41 whose curvature has changed in this way is irradiated with a parallel laser beam LB,
As shown in FIG. 1a, when the laser beam LB is incident on the central part of the mirror surface 41 with almost the same curvature, the curvatures of the parts a and b that the beam hits are almost the same, so that The reflected beam becomes almost the same parallel beam as the incident beam, but
As shown in FIG. 3c, as the laser beam LB enters the end of the mirror surface 41, the mirror surface 4
As the curvature of 1 becomes smaller, the rate of change in the curvature of the portion hit by the beam gradually increases, and accordingly, the beam apertures α1 and α2 of the reflected beam gradually increase.

That is, in Fig. 1b, the incident laser beam
Since the curvatures c and d of the portion where LB hits the mirror surface 41 are different, the reflected beam spreads, and in FIG.
Since the respective curvatures of e and f in the portion corresponding to , are significantly different, the reflected beam is greatly spread.

Therefore, the directivity of the laser beam LB reflected at the central portion of the mirror surface 41 becomes sharp, and objects in the direction of reflection can be detected with high sensitivity with sufficiently high power density. , the object detection distance in the reflection direction becomes longer.

In addition, the more the laser beam LB is reflected at the end of the mirror surface 41, the more the directivity of the reflected beam decreases and becomes broader.As a result, the power density decreases and object detection sensitivity gradually decreases, and the direction of the reflection decreases. Object detection distance becomes shorter.

Normally, the fourth vehicle radar for forward monitoring is
As shown in the figure, the area A is monitored by a radar that detects objects that may obstruct the movement of the automobile 7.
As a rough outline, the shaded area in the figure is necessary. The monitoring area A has, for example, a length L of about 100 m in front of the vehicle and a width W of about 4 to 5 m. In the figure,
8 is a driving lane for the automobile 7 having a width of about 2.5 to 3.5 m.

When one beam is reflected by the rotating polygon mirror 4 and scanned repeatedly so as to cover the monitoring area A, A1 in the monitoring area A
As mentioned above, the directivity of the laser beam LB reflected by each mirror surface 41 is set to be the sharpest, and for the A2 portion on both sides, the directionality of the laser beam LB reflected by each mirror surface 41 is adjusted as described above. If the curvature of each mirror surface 41 is set so that the beam aperture of the laser beam LB gradually expands toward the outside and the directivity becomes broader, the vehicle-mounted radar can detect only objects within the monitoring area A. As a result, unnecessary objects in other areas can be excluded from detection.

As described above, the radar beam scanning device according to the present invention scans the beam only in the area necessary for radar monitoring, and prevents the transmission and reception of the beam from unnecessary detection of objects outside the area. It will be possible to effectively suppress it through the system.
Furthermore, since the side portions of the area monitored by the radar are scanned by the laser beam with a widened beam opening, objects within the monitoring area can be quickly detected.

It goes without saying that the present invention is not limited to radars using laser beams, but can be widely applied to radars in which other general beams such as electromagnetic waves are diffracted and scanned by a rotating reflector.

Effects As described above, in the present invention, in a radar beam scanning device that performs beam scanning by reflecting a directional parallel beam emitted from a radar transmitter by a rotating reflecting mirror, The curvature of the mirror surface is almost constant in the horizontal plane where the beam is scanned, and the directivity of the reflected beam becomes broader as it goes from the center where it is sharpest to the edge. By making the surface a convex surface with a curved surface with a gradually increasing rate of change in curvature, the mirror surface has a sharply directional reflected beam that can be directed only to a predetermined monitoring area where objects need to be detected. It has the excellent advantage of being able to perform beam scanning.

[Brief explanation of the drawing]

Figures 1a, b, and c are plan views showing the reflection states of the laser beam by the rotating mirror surface in the radar beam scanning device according to the present invention, Figure 2 is a front view of the rotating mirror part, and Figure 3 is the laser beam FIG. 4 is a simplified diagram showing an example of a configuration of a radar using a vehicle. 1... Radar transceiver, 2... Light transmitter, 3...
Motor, 4... Rotating multi-area, 5... Light receiver, 6...
...Motor driver, 7...Automobile.

Claims (1)

[Scope of utility model registration request] In a radar beam scanning device that performs beam scanning by reflecting a directional parallel beam emitted from a radar transmitter by a rotating reflecting mirror, the mirror surface of the rotating reflecting mirror is in a horizontal plane where the beam is scanned, A curved surface where the curvature of the mirror surface is almost constant and the rate of change in curvature gradually increases from the center where the directivity of the reflected beam becomes sharpest to the edges so that the directivity of the reflected beam becomes broader. A radar beam scanning device characterized by having a convex surface with a .