Patent ID: 6943881
Filing Date: 2005-09-13
Classification: A61B,G01B,G01J,G01N,G02B

Abstract:
1. A method for optically measuring a sample comprising: directing one beam of guided light in a first propagation mode to a sample; directing a first portion of the guided light in the first propagation mode at a location near the sample away from the sample before the first portion reaches the sample while allowing a second portion in the first propagation mode to reach the sample; controlling a reflection of the second portion from the sample to be in second propagation mode different from the first propagation mode to produce a reflected second portion; directing both the first portion in the first propagation mode and the reflected second portion in the second propagation mode through a common waveguide into a detection module to extract information from the reflected second portion on the sample; adjusting a relative phase delay between the reflected first portion and the reflected second portion to a first value to measure a first signal associated with a first layer within the sample; adjusting the relative phase delay to a second, different value to measure a second signal associated with a second layer within the sample; and obtaining a ratio between the first and the second signals to extract information about a layer of the sample located between the first and the second layers.