Birefringence measurement system

A method of measuring birefringence properties of a sample, comprising the steps of:

• modulating polarization of monochromatic light;
• directing a beam of the modulated, monochromatic light through the sample along an incidence path;
• reflecting a second part of the beam from a reflective surface that is in the incidence path so that a first part of the beam is not reflected;
• analyzing the first part of the beam and a second part of the beam;
• determining the intensity of the reflected second part of the beam;
• determining the intensity of the first part of the beam;
• calculating a birefringence property of the sample based on the determined intensities;
• and
• calibrating the optical system by using a compound zero-order waveplate having two components, each of a known birefringence, that are combined in a manner to reduce the combined birefringence to a level lower than the known birefringence.

A method of measuring birefringence properties of a sample, comprising the steps of:

• modulating polarization of light;
• directing a beam of the modulated light through the sample along an incidence path;
• reflecting a second part of the beam from a reflective surface that is in the incidence path so that a first part of the beam is not reflected;
• analyzing the first part of the beam and a second part of the beam;
• determining the intensity of the reflected second part of the beam;
• determining the intensity of the first part of the beam;
• periodically moving the sample so that the beam is directed through a plurality of locations on the sample;
• calculating either or both the retardance magnitude of the sample and the angular orientation of a birefringent axis of the sample at each location;
• and
• simultaneously graphically displaying the retardance magnitude and angular orientation of substantially all of the locations.

A system for measuring birefringence properties in a sample, comprising:

• a source of light;
• means for polarizing the light;
• modulating means for modulating the polarization of the light;
• a sample arranged so that a beam of the modulated light passes through the sample along an incidence path;
• a beam-splitting element arranged to have a reflective surface for reflecting along a reflected path a second part of the beam that passes through the sample, whereby a first part of the beam passes through the beam-splitting element along the incidence path;
• a first analyzer located in the incidence path and having a polarization direction;
• a second analyzer located in the reflected path and having a polarization direction that is different than the polarization direction of the first analyzer;
• detection means for detecting the intensity of the first and second parts of the beam, thereby to provide information suitable for calculating a birefringence property of the sample based on the detected intensities;
• wherein the reflective surface is arranged so that the angle between the incidence path and the reflected path is less than 5 degrees.