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:
Sep. 10, 2002
Filed:
Mar. 31, 2000
Yee Loy Lam, Singapore, SG;
Zhisheng Yun, Singapore, SG;
Yan Zhou, Singapore, SG;
Siu Chung Tam, Singapore, SG;
Nanyang Technological University, Singapore, SG;
Abstract
A method for sensing and analyzing topographic properties of an aspheric test element is disclosed. The principle of the measurement technique is to immerse the element under test into a container filled with liquid crystal. A polarized plane wave passes through front and back precisely processed glass plates of the container sandwiched between a polarizer and an analyzer. The two side plates are not transited by the plane wave of light but are deposited with conductive layers in order to generate an electrical field between them. This DC (direct current) external electrical field is supplied to help to align the molecular direction of the liquid crystal. In a thus-induced desired configuration, the molecular direction of liquid crystal is aligned to be perpendicular to the incident plane wave front. As the plane light wave propagates through the liquid crystal in the container, it will be divided into ordinary and extraordinary beams. These two beams will create interference behind the analyzer. In the presence of the aspheric optical element under test, which is not a uniaxial crystal, a compensatory interferogram will be formed. Analysis of the interferogram will allow the user to determine the topographic surface profile of the aspheric element under test.