Multiplexed hyperspectral imaging and spectrometry using spatial light modulators

The signal-noise-ratio, (SNR) is often the primary figure of merit when evaluating instrument performance. Multiplexing is one method employed in spectrometry and imaging to increase the magnitude of a signal received by a detector during a period of measurement. Optical masks employing Hadamard encoding matrices for multiplexing can be used to increase the SNR of some spectrometric and hyperspectrometric imaging measurements. A transmissive/opaque metal-etched optical mask and a reflective micro-mirror optical mask were used to investigate Hadamard transform (HT) multiplexing in spectrometric and hyperspectrometric imaging measurements. HT spectrometry (HTS) is a combination of dispersive and multiplexing spectrometry employing a one-dimensional (1D) optical mask. Dividing and folding the ID Hadamard, encoded optical mask used for spectral encoding in HT multiplexing spectrometry results in a two-dimensional (2D) mask that can be used for spatial encoding in Hadamard transform imaging (HTI). An etched, mechanically translated 2D optical mask and a digital micro-mirror array (DMA) encoded by a cyclic S₂₅₅ matrix were successfully employed in the investigation of spatial multiplexing in HT Raman chemical mapping systems. Imaging heterogeneous liquid and solid samples using a 2D Hadamard encoded metal-etched moving mask was successfully demonstrated using conventional Raman spectroscopic equipment. The DMA is an improvement in Hadamard optical mask technology over moving optical masks and was successfully applied to visible Raman hyperspectral imaging of heterogeneous liquid and solid samples. The DMA was also successfully demonstrated to be effective for improving SNR in near-infrared (NIR) FITS as a 1D Hadamard encoded optical mask.