Hyperspectral Image Projector Research Articles

Digital phantoms generated by spectral and spatial light modulators.

A hyperspectral image projector (HIP) based on liquid crystal on silicon spatial light modulators is explained and demonstrated to generate data cubes. The HIP-constructed data cubes are three-dimensional images of the spatial distribution of spectrally resolved abundances of intracellular light-absorbing oxyhemoglobin molecules in single erythrocytes. Spectrally and spatially resolved image data indistinguishable from the real scene may be used as standard data cubes, so-called digital phantoms, to calibrate image sensors and validate image analysis algorithms for their measurement quality, performance consistency, and interlaboratory comparisons for quantitative biomedical imaging applications.

Developing digital tissue phantoms for hyperspectral imaging of ischemic wounds

Hyperspectral imaging has the potential to achieve high spatial resolution and high functional sensitivity for non-invasive assessment of tissue oxygenation. However, clinical acceptance of hyperspectral imaging in ischemic wound assessment is hampered by its poor reproducibility, low accuracy, and misinterpreted biology. These limitations are partially caused by the lack of a traceable calibration standard. We proposed a digital tissue phantom (DTP) platform for quantitative calibration and performance evaluation of spectral wound imaging devices. The technical feasibility of such a DTP platform was demonstrated by both in vitro and in vivo experiments. The in vitro DTPs were developed based on a liquid blood phantom model. The in vivo DTPs were developed based on a porcine ischemic skin flap model. The DTPs were projected by a Hyperspectral Image Projector (HIP) with high fidelity. A wide-gap 2nd derivative oxygenation algorithm was developed to reconstruct tissue functional parameters from hyperspectral measurements. In this study, we have demonstrated not only the technical feasibility of using DTPs for quantitative calibration, evaluation, and optimization of spectral imaging devices but also its potential for ischemic wound assessment in clinical practice.

Hyperspectral image projectors for radiometric applications

We describe a Calibrated Hyperspectral Image Projector (CHIP) intended for radiometric testing of instruments ranging from complex hyperspectral or multispectral imagers to simple filter radiometers. The CHIP, based on the same digital mirror arrays used in commercial Digital Light Processing (DLP) displays, is capable of projecting any combination of as many as approximately one hundred different arbitrarily programmable basis spectra per frame into each pixel of the instrument under test (IUT). The resulting spectral and spatial content of the image entering the IUT can simulate, at typical video frame rates and integration times, realistic scenes to which the IUT will be exposed during use, and its spectral radiance can be calibrated with a spectroradiometer. Use of such generated scenes in a controlled laboratory setting would alleviate expensive field testing, allow better separation of environmental effects from instrumental effects and enable system-level performance testing and validation of space-flight instruments prior to launch. Example applications are system-level testing of complex hyperspectral imaging instruments and algorithms with realistic scenes and testing the performance of first-responder cameras under simulated adverse conditions. We have built and tested a successful prototype of the spectral engine, a primary component of the CHIP, that generates arbitrary, programmable spectra in the 1000 nm to 2500 nm spectral range. We have also built a spectral engine operating at visible wavelengths to be discussed in a separate publication. Here we present an overview of this technology and its applications and discuss experimental performance results of our prototype infrared spectral engine.