Convergent beam scanner with multiple mirror defocus compensation

Claim 1

An optical system comprising: an objective lens means having a first optical axis for forming a convergent focused beam of light from a distant radiating object; a first plane deflection mirror mounted at a first point on said first axis and inclined thereto to redirect said beam to a second point in a reference plane normal to said first optical axis; a plurality of plane scanning mirrors symmetrically mounted in fixed relative positions at a fixed radial distance parallel to and facing a second axis, the center of one of said scanning mirrors coinciding with said second reference point; a linear array of optical detectors mounted in fixed relative position to said objective lens and said first and second points with the centers of their active faces in a first radial plane through said second axis, the normal to the center of said array passing through said second reference point making an acute angle of at least several degrees with the straight line through said first and second points, said acute angle being approximately bisected by the normal from said second axis to said second point; a third point located at the center of a second of said scanning mirrors; an eyepiece lens having a third optical axis parallel to said first and second axis; a second deflection mirror centered on said third axis and inclined thereto to reflect a light ray from said third point to said third axis; a linear array of light emitting elements having their centers in a second radial plane through said second axis and having a central normal which passes through said third point, said light emitters being electronically coupled to said detector elements, with said lenses, deflection mirrors, and arrays being in fixed relative positions to one another and the spacing of said first and third axes from said second axis being equal and less than said fixed radial distance to said scanning mirrors; and means for rotating said scanning mirrors relative to said relatively fixed elements about said second axis.