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:
Jun. 30, 1987
Filed:
Nov. 19, 1984
Jean Canteloup, Montlhery, FR;
Compagnie Industrielle des Telecommunications, Paris, FR;
Abstract
A device for monitoring the thickness of a low absorption thin film or layer (53B) on an at least partially reflecting substrate (31) placed inside a vacuum chamber (1) closed by a window (7), includes a polarized laser source (8), a polarizing cube (13), placed in the path of the laser beam, consisting of two right-angle prisms (13A, 13B) assembled by their hypotenuse faces by means of a dielectric film (13C), the cube being oriented so that the incident laser beam has a 45 degree angle of incidence with the film, the cube allowing a first part of the incident beam to pass into a first, linear optoelectronic converter (15A) supplying a first electrical signal (I.sub.oe), the cube reflecting a second part of the incident beam to pass through a quarter-wave plate (7, 7A) and reflect off the layer before returning through the cube, without being deflected, and thereafter striking a second converter (15B) supplying a second electrical signal (I.sub.e). The device further includes apparatus for finding the ratio of the second electrical signal to the second electrical signal, for correcting spurious light, or obtaining the derivative of the ratio, for calibrating the measuring head, and for supplying a signal when the derivative has remained, for a given amount of time, between two given values limiting a set point value for the desired thickness of the layer.