Polarization interferometer with beam polarizing compensator

Claim 1

In dichroism measurement apparatus that includes: a. a source of electromagnetic radiation of different wavelengths lambda , b. a linear polarizer operable upon said source radiation to linearly polarize same, c. interferometer means for processing the linearly polarized source radiation to provide a beam characterized, for each wavelength, by ellipticity that alternates between left and right circular polarization and between which the beam polarization becomes linear in one direction as the ellipticity alternates from left to right circular polarization, and linear in the orthogonal direction as the ellipticity alternates from right to left circular polarization, the characteristic frequency Nu a of such alternation varying as a function of the wavelength, d. a sample space located for effecting passage of the elliptically polarized beam through a dichroic sample in that space, the sample differentially absorbing the alternately polarized radiation of a characteristic set of wavelengths lambda , and e. a beam intensity detector located in the path of the beam passing from the sample space and characterized as having signal output that varies in intensity with frequency Nu a when said sample is in said space, said output adapted for processing to produce dichroic spectra varying with wavelength lambda , the improvement comprising, f. said means comprising two prisms, at least one of which is movable with respect to the other, both having axes at 45* to the linear polarization direction, and actuating means for effecting such relative movement of said prisms to control said frequencies Nu a.