Prismatic beam rotator for an optical beam projector

Abstract

A beam projector which is controlled to alternately transmit rectangular cross-sectional beams substantially parallel to a projection axis, wherein the beams are respectively pulse modulated over a correspondingly distinct pulse rate frequency range to supply yaw and pitch information and are respectively scanned in a direction correspondingly orthogonal to the cross-sectional length of each beam. The size format of the beam cross-sections and the angles of scan are controlled according to a predetermined time variable function. In a first time period, the largest cross-sectional beams are alternately transmitted and the scan angle is decreased as a function of time, so that a fixed area of detectable information is available for detection with respect to an imaginary orthogonal reference plane moving along the projection axis at a rate corresponding to the predetermined time variable function. In subsequent time periods proportionately smaller cross-sectional beams are transmitted and the scan angle is continually controlled. The disclosed embodiment employs the use of a single set of proportionately different size formatted cross-sectional laser sources as a radiation generator, a scanning mechanism, a vibrationally modulated Pechan type prism and a fixed focus optical system to effect alternately transmitted beams, of selectable cross-section, orthogonally oriented and scanned with respect to each other.