Hinds Instruments, Inc.

Theodore C Oakberg

Baoliang Wang

Paul Kadlec

A practical system and method for measuring waveplate retardation. The system employs a photoelastic modulator in an optical setup and provides high sensitivity. The analysis is particularly appropriate for quality-control testing of waveplates. The system is also adaptable for slightly varying the retardation provided by a waveplate (or any other retarder device) in a given optical setup. To this end, the waveplate position may be precisely altered to introduce correspondingly precise adjustments of the retardation values that the waveplate provides. The system is further refined to permit one to compensate for errors in the retardation measurements just mentioned. Such errors may be attributable to static birefringence present in the optical element of the photoelastic modulator that is incorporated in the system.

Measurement of waveplate retardation using a photoelastic modulator

A practical system and method for precisely measuring low-level birefringence properties (retardance and fast axis orientation) of optical materials ( ). The system permits multiple measurements to be taken across the area of a sample to detect and graphically display ( ) variations in the birefringence properties across the sample area. In a preferred embodiment, the system incorporates a photoelastic modulator ( ) for modulating polarized light that is then directed through a sample ( ). The beam (&ldquo;Bi&rdquo;) propagating from the sample is separated into two parts, with one part (&ldquo;B &rdquo;) having a polarization direction different than the polarization direction of the other beam part (&ldquo;B &rdquo;). These separate beam parts are then processed as distinct channels. Detection mechanisms ( ) associated with each channel detect the time varying light intensity corresponding to each of the two parts of the beam. This information is combined for calculating a precise measure of the retardance induced by the sample, as well as the sample's fast axis orientation.

Birefringence measurement

A practical system and method for precisely measuring low-level birefrigence properties (retardance and fast axis orientation) of optical materials ( ). The system permits multiple measurements to be taken across the area of a sample to detect and graphically display ( ) variations in the birefrigence properties across the sample area. In a preferred embodiment, the system incorporates a photoelastic modulator ( ) for modulating polarized light that is then directed through a sample ( ). The beam (&ldquo;Bi&rdquo;) propagating from the sample is separated into two parts, with one part (&ldquo;B &rdquo;) having a polarization direction different than the polarization direction of the other beam part (&ldquo;B &rdquo;). These separate beam parts are then processed as distinct channels. Detection mechanisms ( ) associated with each channel detect the time varying light intensity corresponding to each of the two parts of the beam. The information is combined for calculating a precise measure of the retardance induced by the sample, as well as the sample's fast axis orientation.

Birefringence measurement system

A practical system and method for measuring waveplate retardation. The system employs a photoelastic modulator ( ) in an optical setup and provides high sensitivity. The analysis is particularly appropriate for quality-control testing of waveplates ( ). The system is also adaptable for slightly varying the retardation provided by a waveplate ( ) or any other retarder device in a given optical setup. To this end, the waveplate ( ) position may be precisely altered to introduce correspondingly precise adjustments of the retardation values that the waveplate ( ) provides. The system is further refined to permit one to compensate for errors in the retardation measurements just mentioned. Such errors may be attributable to static birefringence present in the optical element of the photoelastic modulator ( ) that is incorporated in the system.

Modulated interference effects arising when laser beams are modulated by photoelastic modulators are substantially eliminated by methods and apparatus that extract from the detected beam the modulated, interfering light that emanates from the optical element of the modulator.

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Forest Grove, OR, United States of America

Theodore C Oakberg