JP2522499Y2 - Laser radar receiver - Google Patents

Description

[Detailed description of the invention] [Summary] Regarding the laser radar receiver used for measuring the distance to the target, the signal light reflected from the target is used to increase the detection range and improve the distance measurement accuracy. In a laser radar receiving device that condenses light with a light receiving lens and receives light with a detector, a receiving viewing angle is enlarged behind the light receiving lens, and the signal light is reflected in a direction substantially perpendicular to the axis of the signal light. A curved mirror for condensing the signal light outside the optical path of the signal light incident on the curved mirror via the optical disc, and a detector arranged at a position where the signal light is condensed via the curved mirror. .

[Industrial applications]

The present invention relates to a laser radar receiver used for measuring a distance from a target.

In a laser radar that transmits laser pulses in the detection direction and receives reflected light from the target to measure the distance, the viewing angle of the reflected light affects the detection range, thus enabling highly accurate distance measurement. Requires an increase in the detection range, and therefore, an increase in the reception viewing angle.

[Conventional technology]

A laser radar which is mounted on a vehicle and measures the distance between the vehicle and a preceding vehicle or the like drives a laser diode 2 with the output of an oscillator 1 as shown in FIG. Radiates forward. Then, reflected light from a target such as a vehicle ahead is condensed by a receiving lens 4 such as a Fresnel lens and received by a detector 5, and its output is amplified by an amplifier 6. The distance generator 7 compares the output (transmitted pulse) of the oscillator 1 with the output (received pulse) of the amplifier 6,
A distance signal having the time difference T as a pulse width is generated. The counter 8 counts the pulse width T of the distance signal by a reference clock and converts the pulse width T into inter-vehicle distance data with a preceding vehicle or the like.

As shown in FIG. 8 (a), the focal length of the receiving lens 4 is
When the size (diameter) of the FL and the detector 5 is a, the reception viewing angle θ of this laser radar is Is represented by Therefore, to increase θ, it is necessary to reduce FL or increase a.

[Problems to be solved by the invention]

However, the detector size (chip area)
There is a disadvantage that the response becomes worse when a is increased. If the focal length FL is reduced as shown in FIG. 8 (b), the allowable range b for installing the detector 5 becomes narrower than the case where the FL is large as shown in FIG. 8 (c). There are drawbacks.

The present invention is intended to increase the reception viewing angle θ without adding a focusing means without reducing the focal length FL and without increasing the detector size a.

[Means for solving the problem]

1A and 1B are diagrams showing the principle of the present invention, in which FIG.
In FIG. 1, the light condensing means 9 is disposed in front of the light receiving lens 4.

[Action]

When the light condensing means 9 is interposed as shown in FIG. 1A, this is equivalent to increasing the size a of the detector 5, and the reception viewing angle is enlarged. At this time, the detector 5 is disposed ahead of the focal length FL of the light receiving lens 4.

As shown in FIG. 1 (b), when the light collecting means 9 is disposed in front of the light receiving lens 4, this is equivalent to a reduction in the focal length FL of the light receiving lens 4, and the reception viewing angle is also enlarged in this method. . At this time, the detector 5 is disposed at the focal point of the light receiving lens 4.

〔Example〕

2 to 5 show different embodiments of the system of FIG. 1 (a).

FIG. 2 shows the focusing means 9 realized by a convex lens 9A.
The output light of the light receiving lens 4 (a convex Fresnel lens in this example) is further collected by the convex lens 9A. In this case, since it is ideal that the detector 5 is disposed at the focal point of the convex lens 9A, the convex lens 9A and the detector 5 may be unitized in advance. If this unit 10 is arranged ahead of the focal point of the light receiving lens 4, the reception viewing angle can be expanded equivalently to increasing the detector size a. Moreover, since the positional accuracy of the unit 10 described above does not have to be strict, assembly is easy.

FIG. 3 is a diagram showing a configuration of the present invention in which the light collecting means 9 is realized by a curved mirror 9B. In FIG. 3, while the reception viewing angle is enlarged, the signal light reflected from the target is reflected in a direction substantially perpendicular to the axis of the signal light, and the signal light enters the curved mirror via the reception lens outside the optical path of the signal light. The curved mirror 9B for condensing light is disposed in front of the focal point of the light receiving lens 4, and the detector 5 is located at a position where the signal light is condensed via the curved mirror 9B.
Is arranged so that the reflected light from the curved mirror enters the detector 5. Also in this case, the reception viewing angle can be expanded equivalently to expanding the detector size a, and since the detector is installed not in the rear but in the lateral direction, there is an effect that the depth dimension can be further reduced. Since it is outside, there is an effect that the condensing loss is reduced.

FIG. 4 illustrates two examples in which the focusing means 9 is a parabolic mirror 9C. In FIG. 1A, a hole is formed in the top surface of the converging parabolic mirror 9C, and the detector 5 is disposed there.
Another parabolic mirror 9C 'is disposed at the focal point of the light source and the reflected light is incident on the detector 5. On the other hand, FIG. 2B shows the detector 5 directly disposed at the focal point of the parabolic mirror 9C for focusing. Also in this example, the reception viewing angle can be expanded equivalently to expanding the detector size a.

FIG. 5 shows an optical fiber 9D as the focusing means 9. The optical fiber 9D has a number of tapered optical fibers bundled in a conical shape, and the bottom surface (wide area side) is disposed at the focal point of the light receiving lens 4 and the vertex (small area side) is disposed near the detector 5. The optical fiber 9D having such a shape has a light collecting function similar to that of the convex lens 9A, which is equivalent to increasing the detector size a. In this case, the reception viewing angle is enlarged according to the size of the bottom surface of the optical fiber 9D.

FIG. 6 shows an embodiment based on the method of FIG. 1 (b), in which the condensing means 9 provided in front of the light receiving lens 4 is realized by a concave lens 9E. In this example, the detector 5 is disposed at the focal point of the light receiving lens 4. However, since the concave lens 9E is disposed in front of the light receiving lens 4, the reception viewing angle is equivalent to the case where the focal length FL of the light receiving lens 4 is reduced. Is enlarged. This concave lens 9E may be a Fresnel type.

[Effect of the invention]

As described above, according to the present invention, there is an advantage that the reception viewing angle of the laser radar required for capturing the target can be increased without reducing the focal length of the light receiving lens or increasing the detector size. Particularly, in the case of a vehicle, the vehicle often pitches due to road surface distortion or the like, and the optical axis of the light receiving unit often deviates from the target. In such a case, if the reception viewing angle is wide, the target can be reliably captured, so that the ranging accuracy is improved. In addition, a curved mirror that reflects the signal light in a direction substantially perpendicular to the axis of the signal light is disposed, and a detector is disposed at the light condensing position, so that the depth dimension can be reduced.
Effects such as a reduction in light collection loss can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing a specific example of FIG. 1 (a), FIG. 3 is a diagram showing the structure of the present invention, FIG. 4 and FIG. FIG. 6A is a diagram showing another specific example, FIG. 6 is a diagram showing a specific example of FIG. 1B, FIG. 7 is a principle diagram of a laser radar, and FIG. . In the figure, 4 is a light receiving lens, 5 is a detector, 9 is a focusing means, 9A is a convex lens, 9B is a curved mirror, 9C is a parabolic mirror, and 9D.
Is an optical fiber and 9E is a concave lens.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-183606 (JP, A) JP-A-63-249413 (JP, A) JP-A-60-227324 (JP, A) JP-A-2- 170205 (JP, A) JP-A-62-242806 (JP, A) JP-A-2-1122783 (JP, A) JP-A-59-65279 (JP, A) JP-A-57-19195 (JP, U) Japanese Utility Model Showa 59-117981 (JP, U) Japanese Utility Model Showa 63-190983 (JP, U) Japanese Patent Publication No. 63-4652 (JP, B2) Japanese Patent Publication No. 4-10592 (JP, B2)

Claims (1)

(57) [Scope of request for utility model registration] 1. A laser radar receiving apparatus for condensing signal light reflected from a target by a light receiving lens (4) and receiving the signal light by a detector (5). A curved mirror (9B) for reflecting the signal light in a direction substantially perpendicular to the axis of the signal light and condensing the signal light outside the optical path of the signal light incident on the curved mirror via the receiving lens is arranged. A laser radar receiving device comprising a detector disposed at a position where light is condensed via a curved mirror.