Patent ID: 6121598
Filing Date: 2000-09-19
Classification: G01C,G02B

Abstract:
A laser beam transmitting system comprising:a reflective target comprising at least two discrete target portions, wherein said discrete target portions define respective predetermined relative widths, and wherein each of said discrete target portions define distinct characteristic reflectances;a laser detection module operative to produce a reflected laser beam signal;an optical system arranged to generate a reference laser beam selectively in one of a search mode and a target dither mode and to direct a laser beam reflected from said reflective target to said laser detection module, wherein said optical system defines a central rotational axis, said reference beam projects radially from said central rotational axis, said search mode is characterized by movement of said reference beam through a rotational arc defined about said central rotational axis, and wherein said target dither mode is characterized by movement of said reference beam through a selected portion of said rotational arc;a rotary encoder arranged to produce a rotary signal indicative of a rotary position of said reference beam relative to said rotational arc; anda controller programmed toidentify a measured relative width of each of said discrete target portions based upon said reflected laser beam signal and said rotary signal,determine whether said reflected laser beam signal corresponds to a valid target based upon a comparison of said measured relative widths and said predetermined relative widths, andcause said optical system to generate a reference laser beam in one of said search mode and said target dither mode based upon whether said reflected laser beam signal corresponds to a valid target.