Experimental Demonstration Of Multi-Spectral Imaging Of Vegetation With A Diffractive Plenoptic Camera

The use of diffractive optics on space-based multi-spectral sensors allows for the creation of large-aperture systems in small cube satellite packages. However, the current technology will only allow for the imaging of one narrow spectral band. By using computational imaging, the number of spectral bands imaged can be increased while still maintaining a lightweight satellite. We have designed and built a diffractive plenoptic camera (DPC) that combines a diffractive optic and a light field camera in order to capture multiple spectral bands of vegetation to calculate a normalized difference vegetation index (NDVI). This paper will derive equations to relate system parameters to its performance and capture a multi-spectral scene with a DPC. The analysis yielded design equations for the spectral range, spectral resolution, and field of view. The experimental results found that the DPC was able to determine the location of the vegetation but with reduced NDVI values in comparison to a grating spectrometer. Additionally, artifacts like the zeroth-order of diffraction and spectra occupying the same spatial location, were found to contribute to the reduction of the NDVI values. Near the borders of the refocused image, false values were found as a result of optical aberrations present. Overall, the DPC shows potential in becoming a space-based multi-spectral sensor, but the contribution from artifacts and aberrations need to be reduced. Future work includes using different diffractive optic designs, using an intermediate image diffractive plenoptic camera, and using 3D deconvolution techniques.