Patent ID: 8379228
Filing Date: 2013-02-19
Classification: G01B,G01N

Abstract:
1. A device for measuring the thickness of a thin film that is on a sample plate, and the index of refraction of the material of said thin film as a function of wavelength, comprising: an input beam path having a direction of propagation, a first right prism consisting of a prism material that is transparent in the first wavelength band, the first right prism having: and a second right prism that is identical to the first right prism, having corresponding elements comprising: the first right prism is mounted onto a first rotation stage, with the first rotation stage having a first rotation axis and a first rotational position about the first rotation axis with the first rotation axis in the first planar first transmission surface and also parallel to each of a line in the first planar first reflecting surface, a line in the first planar second reflecting surface, and a line in the first planar second transmitting surface the second right prism is mounted onto a second rotation stage, the second stage having a second rotation axis and a second rotational position about the second rotation axis, with the second rotation axis in the second planar second transmission surface, wherein the second rotation axis is also parallel to the first rotation axis, and also parallel to each of a line in the second planar first reflecting surface, a line in the second planar second reflecting surface, and a line in the second planar second transmitting surface the first rotation stage and the second rotation stage are positioned so that a light beam propagating with a central input axis is aligned and in the direction of the input beam path, will follow a light beam path, in which the light beam enters the first planar first transmission surface, then reflects from the first planar reflection surface at an angle of incidence, wherein the angle of incidence is greater than the critical angle for the prism material, then the light beam reflects from the first planar second reflection surface, then the light beam exits through the first planar second transmission surface, then the light beam enters the second right prism through the second planar second transmission surface, then the light beam reflects from the second planar second reflection surface, then the light beam reflects from the second planar first reflection surface, and then the light beam exits through the second planar first transmission surface in an output beam path that is aligned with the central input axis, and a means for pressing a thin film sample plate into close contact with the first planar first reflection surface.