Wavelength agile receiver with noise neutralization and angular

Abstract

A tunable wavelength agile opto-electronic device for detecting and determining an angle of arrival of a collimated beam of radiation comprising a linearly variable optical filter superimposed over an elongated detector having at least one radiation detector element in each quadrant of the detector. Radiation that transverses that filter projects an image of a first portion of the filter onto two adjacent detector elements in separate quadrants at a first end of the elongated detector and an equal size image of a second portion of the filter onto two adjacent detector elements in separate quadrants at a second end of the elongated detector. A signal generated by radiation that transverses the filter onto a detector element in a quadrant at the second end is subtracted from a signal generated by radiation that transverses the filter onto an aligned detector element at the first end of the elongated detector to provide two difference signals, one for each side of the elongated detector. That subtraction reduces noise generated by background radiation to enable easier detection of a collimated beam and processing electronics use the two difference signals to determine the angle of arrival of such a collimated beam. In one embodiment, a liquid crystal bar graph is located between the filter and the detector which, under control of a control unit, forms two transparent narrow apertures at selected positions so that an image of one aperture forms on quadrant detectors at the first end and the second aperture on quadrant detector at the second end.