Measuring method for thickness of transparent plate

Abstract

Abstract PURPOSE: To measure the thickness of a transparent plate with precision by slantingly irradiating the surface of the transparent plate with a laser focusing beam, by generating interference stripes of light reflected by the top and reverse surfaces of the plate, and then by counting the number of stripes. CONSTITUTION: A laser beam from laser light source 2 over transparent plate 1 to be measured is projected slantingly on the surface of transparent plate 1 as projected beam 4 passed through optical system 3. Part of beam 4, after being diffused after beam waist (w), is reflected by surface 1a, and the other by reverse surface 1b, obtaining reflected beams 5 and 6. Mutual interference of a surge based on the optical path difference between both reflected beams 5 and 6 forms light interference stripes 7 at equal intervals where both reflected beams 5 and 6 overlap each other. In interference-formation space 8, two measurement points A and B are fixed crossing interference stripes 7 and the number of interference stripes 7 residing between both the points, so that plate thickness (d) can be measured by a contrast with the number of stripes of a reference thickness plate. COPYRIGHT: (C)1981,JPO&Japio

Inventors

• 👤 Katsumi Kokubu
• 👤 Masaharu Okafuji

Bibliographic Details