Furnishing information to determine the position of a body

摘要

To determine two positional co-ordinates of a point (D) within a space, a beam (10) of radiation is caused to illuminate a part of the space and is deflected cylindrically over the space, the beam being modulated in phase with the cyclical movement such that the radiation incident upon the point (D) includes enough information to identify the point. Radical co-ordinates r, r are defined respectively by (i) shaping the beam so that duration of exposure of the point D to radiation is a measure of r and (ii) pulsing the beam so that pulse frequency varies with r . In a alternative embodiment cartesian co-ordinates are determined by scanning two beams across the space and pulsing them so that pulse frequency indicates displacement r the x and y redirection.