The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 20, 1990
Filed:
Dec. 08, 1986
Wolfgang Gawrisch, Gau-Bischofsheim, DE;
Thomas Trzebiatowski, Wiesbaden, DE;
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
An interference image of a biaxially stretched film strip 4 is generated optically. Streaks in the film strip are areas of different orientation and/or thickness d which are distinguished from the streakfree areas in the interference image by clearly different intensities. In order to generate the interference image, a light-source 1, a diffuser screen 2 and a polarizer 3 are arranged on one side of the film strip 4, and an analyzer 5 and a filter 6 are arranged on the other side of the film strip 4. The light beam of the light source 1 is polarized by the polarized 3 and, within the film (whose main refractive indices n.sub.1 and n.sub.2 have an angle of 45.degree. or 135.degree. respectively to the polarization plane) is split into two beams, oscillating perpendicularly to one another, which have a path difference .GAMMA.=(n.sub.1 -n.sub.2)d after emerging from the film. Of the light behind the film, in general elliptically polarized, only that portion of the light which oscillates parallel to the analyzer plane, which is perpendicular to the polarization plane, passes through the analyzer 5. In general, a colored interference image is obtained if the light source emits polychromatic light. A detector 7 as light-sensitive element, e.g. a video camera, comprising a light-sensitive diode matrix, which is connected to an image analysis and computing unit 8 for evaluation of the interference image, is arranged behind the filter, which serves to increase the contrast of the image.