Design of a Snapshot Spectral Camera Based on Micromirror Arrays

Abstract

Spectral imaging is an emerging tool for a variety of scientific and engineering applications because of the additional information it provides about the nature of the materials being imaged. Snapshot spectral imaging has great advantages over traditional imaging systems in the acquisition of data. Some examples of such systems are the computed tomographic imaging spectrometer (CTIS) and the coded aperture snapshot spectral imager (CASSI). Both instruments are based on computational imaging, which do not directly capture the image of the target. Another class of snapshot spectral imaging systems provides all spatial-spectral information on a single or multiple CCD image sensors with a one-to-one correspondence between datacube voxels and detector pixels. Integral field spectrometry with faceted mirrors (IFS-M), integral field spectrometry with coherent fiber bundles (IFS-F), and image mapping spectrometer (IMS) are all typical examples. In IFS-M, the two-dimensional field of interest is optically divided into small samples that are re-imaged at the entrance plane of the spectrograph. It has the characteristics of low spatial resolution. IFS-F uses a reformatter fiber optics to map a 2D image to a linear array that serves as an input slit to an imaging spectrometer. Its drawback with the use of fibers is that it is quite difficult to be coupled with light efficiently. So part of the light energy will be lost when entering the fiber. The micromirror array is IMS’s core component. It consists of a series of long and narrow mirrors and split and map the image onto the detector image plane. The reflective nature of the micromirror array and use of prisms for spectral dispersion provide the system with a high light collection capacity. In addition, its spatial resolution is higher than IFS-M. A designed snapshot spectral camera based on IMS is given in this chapter. The system with operation wavelength range from 400 nm to 900 nm, focal ratio of 15, and spectral resolution of 14.29 nm is designed, and the design results are analyzed and evaluated. It achieves a good imaging quality. It is expected to be applied to remote sensing.