Optics: measuring and testing – Range or remote distance finding – With photodetection
Patent
1994-02-25
1996-12-31
Buczinski, Stephen C.
Optics: measuring and testing
Range or remote distance finding
With photodetection
356 401, 396106, G01C 308, G03B 300
Patent
active
055899307
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical radar apparatus, and is used, for example, for a constant-speed traveling apparatus and an optical radar apparatus capable of accurately detecting the position of a vehicle, an obstacle or the like moving closer to a detection-side vehicle.
BACKGROUND ART
As optical radar apparatuses capable of setting a detection area in a widthwise direction of a road surface, there are apparatuses such as those disclosed in Japanese Utility Model Laid-Open Nos. 59-117980 and 59-117981.
In the apparatus disclosed in Japanese Utility Model Laid-Open No. 59-117980, shown in FIGS. 7A and 7B, light from a light source is condensed to some extent by a lens to obtain a first detection range .theta.T1, and the light source is suitably moved to obtain a second detection range .theta.T2 wider than the first detection range .theta.T1 in a widthwise direction of a road surface by changing the degree of condensing of the lens.
In the apparatus disclosed in Japanese Utility Model Laid-Open No. 59-117981, shown in FIG. 8, light from a light source traveling through a lens is diffused by a prism to increase an expansion angle in a road surface direction, thereby setting a detection range wide in a widthwise direction of a road surface.
In the apparatus disclosed in Japanese Utility Model Laid-Open No. 59-117980 among the above-described conventional apparatuses, shown in FIGS. 7A and 7B, however, light cannot be emitted simultaneously for the first detection range .theta.T1 and the second detection range .theta.T2, and the detection range is set one-sidedly, since the detection range is changed by moving the light source.
The apparatus disclosed in Japanese Utility Model Laid-Open No. 59-117981, shown in FIG. 8, entails the problem of a reduction in the maximum detection distance because light is uniformly diffused by the prism. Because of this problem, it is not possible to meet a demand heretofore made for widening the detection range in a widthwise direction of a road surface in a short-distance area without reducing the maximum detection distance when an optical radar apparatus is used for an inter-vehicle control or an obstacle detecting apparatus.
The present invention has been achieved in consideration of the above-described problems, and an object of the present invention is to provide an optical radar apparatus capable of increasing the expansion angle in a road surface direction in a short-distance range without setting the detection range one-sidedly and without sacrificing the maximum detection distance.
DISCLOSURE OF INVENTION
According to the present invention, an optical radar apparatus is therefore adopted in which a beam of light is emitted from a light transmitter, reflected light from an object is received by a light receiver, and the distance to the object is detected on the basis of a light transmitting-receiving relationship, the light transmitter having: focal length, and a second focus portion having a second focal length at least longer than the first focal length; and than the first focal length from the optical device, the light source emitting light to the optical device so that light travels to the outside through the first focus portion and the second focus portion.
In the above-described arrangement, the optical device provided in the light transmitter is formed of at least the first focus portion and the second focus portion, and the light source provided in the light transmitter is provided in a position at a distance equal to or shorter than the first focal length from the optical device, and emits light to the optical device so that light travels to the outside through the first focus portion and the second focus portion.
Accordingly, light emerging from the first focus portion in the light emitted from the light source to the optical device has a small expansion angle such as not to diffuse largely and, therefore, can be caused to reach a long distance. On the other hand, light emerging from the second focus portion has a large expansion ang
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patent: 5305047 (1994-04-01), Hayakawa et al.
Ando Hirosi
Hoashi Yoshiaki
Kaneiwa Toshiyuki
Kurahashi Akira
Buczinski Stephen C.
Nippondenso Co. Ltd.
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