Optics: measuring and testing – Range or remote distance finding
Reexamination Certificate
1999-08-24
2001-02-20
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Range or remote distance finding
C356S003000, C356S004050, C356S005010
Reexamination Certificate
active
06191845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distance measuring apparatus and method, as well as an offerable medium for providing program code to implement the apparatus and method. More particularly, the present invention relates to a distance measuring apparatus and method for measuring the distance to an object based on a reflected beam from the object.
2. Description of the Related Art
A distance measuring method is known with which the distance to an object is measured by irradiating a laser beam to the object and measuring a time from the emission of the laser beam to the arrival of a reflected beam. There is also known another distance measuring method of measuring the amount of a laser beam reflected by an object and determining the distance to the object, as disclosed in PCT International Publications WO97/0111, WO97/0112 and WO97/0113, for example.
With the above latter related art, however, it is difficult to achieve precise measurement of the distance because the reflectivity of the object for the laser beam is not taken into consideration.
The above former related art has a problem as follows. When measuring the distance to an object having a predetermined size, the laser beam requires to be scanned over the whole of the object. Accordingly, the time at which the distance is measured differs for each point on the object, and therefore the distance to a moving object cannot be precisely measured.
SUMMARY OF THE INVENTION
The present invention has been made in view of the state of art set forth above, and intends precise measurement of the distance, taking into account the reflectivity of an object for a laser beam.
The present invention provides a distance measuring apparatus for measuring the distance to an object using a laser beam, the apparatus comprising laser beam emitting means for emitting a laser beam; light receiving means comprising at least one light receiving device for receiving the laser beam reflected by the object; control means for controlling the laser beam emitting means to emit the laser beam, and controlling the light receiving means to receive the laser beam reflected by the object during a first period of time and to receive the laser beam reflected by the object during a second period of time; and calculating means for producing a measured value corresponding to the amount of light received during the first period of time and a reference value corresponding to the amount of light received during the second period of time, normalizing the measured value with the reference value, and calculating the distance to the object based on the normalized measured value.
Also, the present invention provides a distance measuring method for measuring the distance to an object using a laser beam, the method comprising the steps of a laser beam emitting step of controlling a laser beam emitting unit to emit a laser beam; a first light receiving step of making control to receive the laser beam reflected by the object during a first period of time by a light receiving unit comprising at least one light receiving device; a second light receiving step of making control to receive the laser beam reflected by the object during a second period of time by the light receiving unit; and a calculating step of producing a measured value corresponding to the amount of light received during the first period of time and a reference value corresponding to the amount of light received during the second period of time, normalizing the measured value with the reference value, and calculating the distance to the object based on the normalized measured value.
REFERENCES:
patent: 5576975 (1996-11-01), Sasaki et al.
patent: 5699280 (1997-12-01), Oda et al.
Font Frank G.
Limbach & Limbach L.L.P.
Ratliff Reginald A.
Sony Corporation
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