The optical apparatus basically comprises a cylindrical lens which gathers light reflected at various angles from a material surface and projects it onto a strip like curved mirror with its axis at right angles to the lens and which subsequently concentrates the light onto a number of photodetectors...http://www.google.fr/patents/US4248537?utm_source=gb-gplus-shareBrevet US4248537 - Optical apparatus for determining the light exit angle from a material strip illuminated by a light bead
Optical apparatus for determining the light exit angle from a material strip ...
