Patent ID: 8902425
Filing Date: 2014-12-02
Classification: G01B,G01N

Abstract:
1. A light source, comprising: a light-emitting diode operatively configured to emit an unpolarized, incoherent light beam directed along an optical axis; an adjustable polarizer positioned on said optical axis to intercept said light beam, said polarizer being operatively configured to polarize said light beam along a polarization direction perpendicular to said optical axis; a beam splitter positioned on said optical axis to intercept said light beam after passage through said polarizer, said beam splitter comprising a first optical surface operatively configured to reflect a first portion of said polarized light beam and to transmit a second portion of said polarized light beam therethrough, wherein a place of incidence of said light beam at said beam splitter includes said optical axis and is perpendicular to said first optical surface; and a photodetector positioned to capture said first portion of said polarized light beam after reflection by said beam splitter and operatively configured to generate photocurrent proportional to an intensity of said captured first portion of said polarized light beam, wherein said first optical surface comprises an optical interference coating, said coating being characterized by a ratio of reflectivity to transmission that depends on polarization and wavelength such that a change of said ratio with wavelength for light polarized parallel to said plane of incidence is opposite to a change of said ratio with wavelength for light polarized perpendicular to said plane of incidence.