Off-axis aberration correction for a reflective coded aperture snapshot spectral imager

The reflective optical configuration of the coded aperture snapshot spectral imager (CASSI) based on a digital micromirror device (DMD) features both high quality and high flexibility of intensity modulation, but the image quality is always subject to off-axis aberration. This letter analyzes the formation of the off-axis aberration, and then proposes an optical-axis-shift (OAS) configuration to compensate for this adverse effect in the DMD-based reflective CASSI system. Experimental results demonstrate that the proposed design can effectively eliminate the off-axis aberration. The average peak signal-to-noise ratio of the reconstructed spectral images is improved by approximately 2.8 dB. In addition, other methods to alleviate the off-axis aberration are discussed, and the superiority of the proposed design is signified. The proposed OAS design is easy to implement with commercially available components, and provides an initial configuration of an optical design to implement a high-performance CASSI instrument.