OPTICAL METHOD TO MEASURE INSTANTANEOUS FIELD OF TRANSPARENT FILM THICKNESS

摘要

FIELD: measurement equipment.;SUBSTANCE: method may be used for contactless continuous measurements of transparent film thickness. The method includes directed exposure of the film to light beams, their total internal reflection at the interface, and subsequent treatment of reflected light. The source of light is placed above the film or under the film, from which light beams are created that are directed at angles - smaller than the limit angle of reflection at the border of film-air and larger than the limit angle of reflection at the border of film-air. The image of the distorted light spot is recorded, which is formed on the solid surface under the film as a result of total internal reflection of light at the interface of film-air, by a video camera, during the entire time of measurement, processed on a computer, geometric dimensions of the light spot are measured, and the thickness of the film is determined using the following formula: h=(D-d)/[4tg arcsin (n₂/n₁)], where h - thickness of the film, D - length of the main diagonal of the ellipse, which approximates the area of the light ring, d - dimension of the source of light on the surface, n₂ - coefficient of air refraction, n₁ - coefficient of film material refraction.;EFFECT: development of a simple method having simple calibration and providing for possibility of direct continuous measurements of time-varying field of transparent film thickness with small measurement error.;3 cl, 2 dwg