Patent ID: 7345698

Claim:
An apparatus for measuring optical distortion in a transmissive reflective sheet, the apparatus comprising: a conveyor receiving and positioning the transmissive reflective sheet, with the conveyor having a length in a transport direction and a width transverse to the length and coextensive with the conveyor; a light source mounted on a first side of the conveyor, the light source projecting a plurality of ellipsoidal two-dimensional images across the length and the width of the conveyor wherein the plurality of two-dimensional images appear continuously and simultaneously on the transmissive reflective sheet, with the plurality of two-dimensional images separated and regularly spaced about the length of the conveyor, with the plurality of two-dimensional images separated and regularly spaced about the width of the conveyor, with each of the plurality of two-dimensional images separated from all others of the plurality of two-dimensional images by a background, with each of the plurality of two-dimensional images regularly spaced from each adjacent one of the plurality of two-dimensional images, with the plurality of two-dimensional images being high-contrast white in color and the background being black in color, wherein the high-contrast white in color of the plurality of two-dimensional images is different from the black of the background and detectable by the camera, and with the plurality of two-dimensional images reflected off the transmissive reflective sheet and producing a plurality of reflected two-dimensional images; a camera oriented to continuously and simultaneously detect the plurality of reflected two-dimensional images corresponding to the plurality of two-dimensional images; and a processing circuit coupled to receive output data from the camera to: measure magnification and orientation of each of the plurality of reflected two-dimensional images; and compute lens power based on a measurement of magnification of the reflected two-dimensional images, wherein the lens power is indicative of a local curvature of the transmissive reflective sheet over the the length and the width of the conveyor.