DMD diffraction measurements to support design of projectors for test and evaluation of multispectral and hyperspectral imaging sensors

Abstract

We describe our use of Digital Micromirror Devices (DMDs) for the performance testing, characterization, calibration, and system-level data product validation of multispectral and hyperspectral imaging sensors. We have developed a visible Hyperspectral Image Projector (HIP), which is capable of projecting any combination of many different arbitrarily programmable basis spectra into each image pixel at up to video frame rates. For the full HIP, we use a scheme whereby one DMD array is used in a spectrally programmable source, to produce light having the spectra of materials in the scene (i.e. grass, ocean, target, etc), and a second DMD, optically in series with the first, reflects any combination of these programmable spectra into the pixels of a 1024 ×768 element spatial image, thereby producing temporally-integrated 2D images having spectrally-mixed pixels. The HIP goes beyond conventional Digital Light Processing (DLP) projectors in that each spatial pixel can have an arbitrary spectrum, not just an arbitrary color. As such, the resulting spectral and spatial content of the projected image can simulate realistic scenes that a sensor system must acquire during its use, and can be calibrated using NIST reference instruments. Here we discuss our current HIP developments that span the visible/infrared spectral range of 380 nm through 5400 nm, with particular emphasis on DMD diffraction efficiency measurements in the infrared part of this range.