Liquid Crystal Based Hyperspectral Image Projector

摘要

A hyperspectral image projector (HIP) is introduced that is built with liquid crystal based spatial light modulators (SLM)as opposed to micromirror arrays. The use of an SLM as a broadband intensity modulator presents several benefits to thisapplication. With slight modifications to the SLM design, SLMs can be built for a wide range of spectral regimes,ranging from the ultraviolet (UV) to the long-wavelength infrared (LWIR). SLMs can have a large pixel pitch,significantly reducing diffraction in the mid-wavelength infrared (MWIR) and LWIR. Liquid crystal based devices offerdirect analog intensity modulation, thus eliminating flicker from time sequential drive schemes. SLMs allow for an on-axis configuration, enabling a simple and compact optical layout. The design of the HIP system is broken into two partsconsisting of a spectral and spatial engine. In the spectral engine a diffraction grating is used to disperse a broadbandsource into spectral components, where an SLM modulates the relative intensity of the components to dynamicallygenerate complex spectra. The recombined output is fed to the spatial engine which is used to construct two-dimensionalscenes. The system is used to simulate a broad range of real world environments, and will be delivered to the NationalInstitute of Standards and Technology as an enabling tool for the development of calibration standards and performancetesting techniques for multispectral and hyperspectral imagers. The focus of this paper is on a visible-band HIP system;however, related work is presented with regard to SLM use in the MWIR and LWIR.