MEMS-based hyperspectral imager uses a single photodetector

Most hyperspectral imagers use a linear or two-dimensional array of photodetectors, with the exception of certain pushbroom mechanisms that use a fixed diffraction grating with two mirrors—one that scans in the spectral domain, the other in the spatial domain. But unlike this exception, which requires the mirrors to rotate out of the plane at high speed and potentially induce aberrations, researchers at the National University of Singapore and the Institute of Microelectronics (both in Singapore) have developed a single-detector hyperspectral imager with a microelectromechanical systems (MEMS) grating that moves in-plane with respect to its surface, significantly reducing nonrigid-body deformations and aberrations and enabling increased image-acquisition rates.

Symmetrical flexure suspensions attach two ends of a circular MEMS diffraction grating to electrostatic comb-drive resonators that cause in-plane rotation of the grating about its geometrical center, which changes the orientation of the grating lines and causes a diffracted laser beam to scan. For hyperspectral imaging, optics direct light from a scene or a sample to bounce off the MEMS grating and pass through a pinhole to a single photodetector that stores the narrowband information. In addition to its mechanical robustness, its small size makes it convenient for portable hyperspectral applications. Contact Guangya Zhou at [email protected].