Optics: measuring and testing – Range or remote distance finding – Triangulation ranging to a point with one projected beam
Patent
1998-10-20
2000-02-29
Buczinski, Stephen C.
Optics: measuring and testing
Range or remote distance finding
Triangulation ranging to a point with one projected beam
356 31, 356 51, 396106, 180169, G01C 300, G01C 308, G03B 1300
Patent
active
060316004
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for determining the position of an object with reference to a measurement device having an optical transmitter which emits a light beam at a varying transmission angle, and having an angularly resolving optical receiver spaced away from the transmitter, a conclusion being drawn, from the respective transmission angle and from the respective angle at which the receiver receives radiation reflected from the object (reception angle), as to the resolution cell, defined by the angular resolution of the transmitter and the receiver, in which the object is located.
BACKGROUND INFORMATION
To determine the position of an object, it is known to use, among other things, an optical triangulation method. For example, in: J. A. Marzalee, R. A. Myllyla: Performance test of an angular scan LED array-based range imaging sensor, Proc. of the SPIE--the International Society for Optical Engineering, 2088 (1994), pp. 59-68. The measurement accuracy of such methods can be quite accurate if the angular resolution of the transmitter and receiver is high, but transmitters and receivers with limited angular resolution are used for reasons which include cost. The result is relatively large resolution cells whose extension in the longitudinal direction--perpendicular to the receiver/transmitter axis--becomes larger with increasing range from the measurement device.
European Patent Application No. 0 479 273 describes a method for determining the distance of an object with respect to a measurement device which is based on the radar principle. In this European Patent Application, the distance of the object to be located is determined by phase comparison between a modulated transmitted signal and a received signal reflected from the object.
It is the object of the present invention to configure an easily implemented optical triangulation method in such a way that the positional resolution is as high as possible for the measurement of the range of an object to be located.
SUMMARY OF THE INVENTION
This object is achieved, using the method according to the present invention, in that the light beam emitted from the transmitter is modulated; that the phase difference between the modulation of the transmitted light beam and the modulation of the received radiation is measured; that the individual resolution cells are defined by discrete transmission angles and reception angles, an address of a memory at which a pertinent phase difference and a distance from the measurement device are stored being allocated to each combination of discrete transmission and reception angles; and that the position of the object within a resolution cell is determined from the measured phase difference and from the phase difference values and distance values stored with reference to the resolution cell in the memory.
The method according to the present invention yields a substantial increase in positional resolution, in particular for ranges which are greater than the distance between transmitter and receiver. The method according to the present invention furthermore has the advantage that it requires only an extremely small additional outlay as compared with the known triangulation methods.
The method and the measurement device according to the present invention can be used for a variety of tasks, and adapted to them in terms of their configuration. They are suitable, for example, as proximity warning systems for motor vehicles and for monitoring purposes.
The method according to the present invention can be used for a variety of tasks. It is suitable, for example, for implementing a proximity warning device for motor vehicles.
A development of the method according to the invention consists in the fact that the transmission angle and the reception angle have discrete values; and that the resolution cell in which an object is located is read out from a stored table for the respective combination of transmission and reception angle that is present.
This development on the one hand makes possible
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Y. D. Chen et al, "Dynamic Calibration and Compensation of a 3D Laser Radar Scanning system", Proceedings of the International Conference on Robotics and Automat, Atlanta, XP0000409872, Institute of Electrical and Electronics Engineers, vol. 3, May 2, 1993, pp. 652-658.
Marszalec et al., "Performance Tests of an Angular Scan LED Array-Based Range Imaging Sensor", Proceedings SPIE, Conference on Laser Dimensional Metrology, Recent Advances for Industrial Application, XP000677571, vol. 2088, Brighton, UK, Oct. 7, 1993, pp. 59-68.
J.A. Marzalee et al., "Performance test of an angular scan LED array-based range imaging sensor", Proc. of the SPIE--the International Society for Optical Engineering, 2088 (1994), pp. 59-68.
Gaillard Alain
Uhler Werner
Winner Hermann
Buczinski Stephen C.
Robert & Bosch GmbH
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