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. 23, 2021
Filed:
Aug. 10, 2018
Applied Photophysics Inc., Beverly, MA (US);
Nigel Thornton Hopley White, Dorking, GB;
Lindsay John Cole, Bookham, GB;
Applied Photophysics Limited, Leatherhead, GB;
Abstract
The present invention relates to methods for calibrating and controlling a polarization modulator, for example a photoelastic modulator (PEM) device on a CD measurement instrument, the method comprising scanning the control input voltage (V) at a fixed wavelength (λ); and recording the CD scan, wherein the control input voltage (V) determines the peak retardation (δ) at the fixed wavelength (λ), and wherein the method is repeated for one or more fixed wavelengths. An augmented drive function allows the PEM to be operated with greater accuracy over the full wavelength range, and measurement of resonant frequency provides a means to continually correct for temperature related drift of retardation.