Thin lightguide target for laser alignment

Abstract

The target structure of this invention is comprised of a thin optically transparent lightguide sheet, preferably two sheets bonded together with flat sides. The thin sheet material is chosen to make a good pocket-size lightguide and provide an adequate tradeoff to cost, manufacturing ease, and internal reflective loss, and may be colored to provide an optical filter enhancing contrast of the viewed image by rejecting unwanted light. At the entrance edge of the target are side-by-side formations generating optically the lens and axicon function, and separately the reference lens function. The exit edges of the sheets are either flat and perpendicular to the faces, or at such an angle as to direct images at a prescribed angle with respect to the face of the sheet(s). The entrance edge of the one sheet is formed with a curve to produce the optical lens and axicon functions, the shape of which can be chosen to enhance any difference occuring between the images when the incoming beam is not on center. The other sheet is similarly designed to the lens function that produces a single image reference line. The exit ends of each lightguide are made in several ways depending on where the images are to be viewed. The output ends may be viewed from the edge of the target, as for drop ceiling rail alignment, and the images appear directly on the ends.