A non-scanning Fourier transform spectrometer utilizing a Wollaston prism array

A new non-scanning Fourier transform (NSFT) spectrometer design has been demonstrated. It is an improvement over a previous design that employs a single Wollaston prism with a linear detector array. Spectrometers based on this design will have the potential to achieve higher optical throughput than grating spectrometers, superior S/N ratio than infrared grating instruments, shorter measurement times than scanning Fourier transform (SFT) spectrometers, and finer resolution than current Wollaston prism designs. Such spectrometers will find important applications in remote sensing, environmental monitoring, industrial processing control, and medical diagnosis.; The previous design consists of a Wollaston prism placed between two suitably oriented polarizees. Light is collimated and then polarized at 45° with respect to the optical axis of the first birefringent wedge of the prism. The analyzer is oriented at 45° with respect to the optical axis of either birefringent wedge. The Wollaston prism induces a linearly varying optical path difference upon the two orthogonal beams of light across the aperture of the prism forming a spatial interferogram on its output side. This interferogram is then imaged onto a linear detector array. With some data processing and a Fourier transformation of the interferogram, the spectrum of the light that entered the spectrometer can be obtained. Current NSFT spectrometers utilizing Wollaston prisms have poor resolution due to the small path difference range that can be induced across the finite aperture of the Wollaston prism. So far, NSFT spectrometers employing Wollaston prisms are used exclusively as laboratory tools.; The design proposed for the new NSFT spectrometer employs a two-dimensional detector array and a multiple number of Wollaston prisms called sub-prisms. Each sub-prism provides a different range of optical path difference and they are designed in such a way that an optical path difference range from one sub-prism partially overlaps the optical path difference range in the next. The union of these ranges forms an equivalent optical path difference range for one long fictional Wollaston prism. The set of sub-prisms is called the Wollaston prism array (WPA). Each sub-prism in the array must be fabricated separately and cemented together to form the array. In conjunction with the two-dimensional detector array, a superior resolution can be achieved to realize a marketable instrument.; To enable the NSFT spectrometer based upon the proposed design function, four technical issues were solved. These were, (1) manufacturing defects compensation, (2) interferogram fusion, (3) dispersion compensation, and (4) spectral compensation. Camera calibration was not an issue for this study since the imaging lens was highly corrected for geometric and chromatic aberrations and the object and image distances are on the order of meters. (Abstract shortened by UMI.)...