Full-frame programmable spectral filters based on micro-mirror arrays

Abstract

Rapidly programmable micro-mirror arrays, such as the DLP ® digital micro-mirror device (DMD), have opened an exciting new arena in spectral imaging: rapidly reprogrammable, high spectral resolution, multi-band spectral filters that perform spectral processing directly in the optical hardware. Such a device is created by placing a DMD at the spectral plane of an imaging spectrometer, and using it as a spectral selector that passes some wavelengths down the optical train to the final image and rejects others. While simple in concept, realizing a truly practical DMD-based spectral filter has proved challenging. Versions described to date have been limited by the intertwining of image position and spectral propagation direction common to most imaging spectrometers, reducing these instruments to line-by-line scanning imagers rather than true spectral cameras that collect entire two-dimensional images at once. Here we report several optical innovations that overcome this limitation and allow us to construct full-frame programmable filters that spectrally manipulate every pixel, simultaneously and without spectral shifts, across a full 2D image. So far, our prototype, which can be programmed either as a matched-filter imager for specific target materials or as a fully hyperspectral multiplexing Hadamard transform imager, has demonstrated over 100 programmable spectral bands while maintaining good spatial image quality. We discuss how diffraction-mediated trades between spatial and spectral resolution determine achievable performance. Finally, we describe methods for dealing with the DLP's 2D diffractive effects, and suggest a simple modification to the DLP that would eliminate their impact for this application.

Full-frame programmable spectral filters based on micromirror arrays

“…11,12 Instead of a microlouver assembly, this prototype was constructed using a bundle-of-tubes capillary array manufactured by the Schott Corporation, (Southbridge, Massachusetts). 11,12 Instead of a microlouver assembly, this prototype was constructed using a bundle-of-tubes capillary array manufactured by the Schott Corporation, (Southbridge, Massachusetts).…”