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:
Nov. 22, 1988
Filed:
Jan. 06, 1987
Hitachi, Ltd., Tokyo, JP;
Abstract
An apparatus for measuring photoelasticity permitting to control mechanical stress applied to an elastic body, by visualizing phase differences of polarized light transmitted by the elastic body is disclosed. In such a prior art apparatus a quarter wavelength plate was used in order to obtain circularly polarized light. However, the precision of the circularly polarized light is worsened, when it works in a wide wavelength region. To the contrary, in an apparatus according to this invention, circularly polarized light is obtained by means of Fresnel's rhombic body. As the result good circularly polarized light can be obtained for a wide wavelength region from the visible region to the near infrared region and control of products including thin films and semiconductor substrates can be effected by visualizing mechanical stress therein.