Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
1999-12-14
2001-09-11
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
C180S167000, C356S003140
Reexamination Certificate
active
06288774
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a distance measuring device, and more particularly, to a distance measuring device for measuring a distance to an object having a plurality of markers by obtaining a distance between images of the markers projected on a light receiving section thereof.
(2) Description of the Related Art
In ITS (Intelligent Transport System) etc., for example, a method has been proposed wherein the speed of a vehicle is controlled in such a manner that the distance between the vehicle and one ahead (hereinafter referred to as “preceding vehicle”) is always kept constant, to thereby lighten the burden imposed on the driver.
To achieve such control, it is necessary that the distance between the vehicle and the preceding vehicle be measured with accuracy.
Conventionally, a method has been employed in which, for example, two markers are affixed to the rear face of the preceding vehicle and parallax of the markers is optically detected to obtain the distance between the vehicles.
With this method, however, it is difficult to measure with accuracy a wide range of distance from short distance to long distance. Specifically, the visual distance between the markers is small when the markers are viewed from a long distance, and it is therefore desirable that the actual distance between the markers should be significantly large, in order to measure the distance with accuracy. If the actual distance between the markers is large, however, the two markers do not fit in the field of view of a parallax detection camera when viewed from a short distance, and therefore, the markers should desirably be separated at a relatively small distance from each other.
Consequently, a problem of trade-off arises between the long- and short-distance measurements, making accurate measurement difficult.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a distance measuring device capable of accurate distance measurement from short through long distances.
To achieve the above object, there is provided a distance measuring device for measuring a distance to an object having a plurality of markers by obtaining a distance between images of the markers projected on a light receiving section thereof. The distance measuring device comprises first marker image acquiring means for acquiring images of a pair of markers separated at a first distance from each other, from among images of the markers projected on the light receiving section, second marker image acquiring means for acquiring images of another pair of markers separated at a second distance from each other, from among the images of the markers projected on the light receiving section, selecting means for selecting the marker images acquired by the first marker image acquiring means or the marker images acquired by the second marker image acquiring means in accordance with a predetermined condition, and computing means for computing a distance to the object based on the marker images selected by the selecting means.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.
REFERENCES:
patent: 5039217 (1991-08-01), Maekawa et al.
patent: 5313262 (1994-05-01), Leonard
patent: 5475494 (1995-12-01), Nishida et al.
patent: 5528217 (1996-06-01), Adams
patent: 54-58047 (1979-10-01), None
Shiohara Morito
Takubo Masayuki
Buczinski Stephen C.
Fujitsu Limited
Staas & Halsey , LLP
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