Optical distance measurement
First Claim
1. Optical distance measuring equipment comprisinga signal source for supplying a modulation signal, a transmission system connected to the signal source for transmitting a transmitted optical signal modulated by the modulation signal, a reception system for receiving a received optical signal which is a reflected and delayed version of the transmitted signal, and a cross-correlator arranged to carry out the steps of determining, at a coarse resolution, a time delay of the modulation signal needed to maximise the cross correlation between the time delayed modulation signal and the received signal, determining at a finer resolution than the coarse resolution, a time delay of the modulation signal needed to maximise the cross correlation between the modulation signal and the received signal as a function of the time delay of the modulation signal with respect to the received signal in a time delay range around the time delay determined at a coarse resolution, and outputting a measure of distance calculated from the time delay of the modulation signal determined at a finer resolution.
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Accused Products
Abstract
Optical distance equipment transmits an optical signal and determines distance by locating the peak of a correlation with the reflected signal. The number of calculations required for the correlation is greatly reduced by using a combination of a coarse and fine correlation. The accuracy of the distance measurement is also improved by calculating the point of intersection of two best fit lines to either side of the correlation peak. The signal is preferably modulated by a maximum length sequence.
72 Citations
21 Claims
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1. Optical distance measuring equipment comprising
a signal source for supplying a modulation signal, a transmission system connected to the signal source for transmitting a transmitted optical signal modulated by the modulation signal, a reception system for receiving a received optical signal which is a reflected and delayed version of the transmitted signal, and a cross-correlator arranged to carry out the steps of determining, at a coarse resolution, a time delay of the modulation signal needed to maximise the cross correlation between the time delayed modulation signal and the received signal, determining at a finer resolution than the coarse resolution, a time delay of the modulation signal needed to maximise the cross correlation between the modulation signal and the received signal as a function of the time delay of the modulation signal with respect to the received signal in a time delay range around the time delay determined at a coarse resolution, and outputting a measure of distance calculated from the time delay of the modulation signal determined at a finer resolution.
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12. A method of optically measuring distance including
supplying a modulation signal, transmitting a transmitted optical signal modulated by the modulation signal, receiving a received optical signal which is a reflected and delayed version of the transmitted signal, coarsely determining a time delay of the modulation signal needed to maximise the cross correlation between the time-delayed modulation signal and the received signal, and calculating at a finer resolution the cross correlation between the modulation signal and the received signal as a function of the time delay of the modulation signal with respect to the received signal in a time delay range around the time delay determined by the coarse cross-correlator to give a measure of distance based on the time delay maximising the cross-correlation calculated at a finer resolution.
Specification