Characterization of disordered medium for small form-factor hyperspectral imaging

Abstract

Hyperspectral imaging is a technology that combines imaging and spectroscopy, This method is drawing attention that it can obtain more precise spectral information than traditional RGB format-based imaging devices. Conventional hyperspectral imaging was performed by scanning in either space or spectral information using dispersive elements. However, the limitation was that it requires large free space to obtain precise spectral resolution. Recently, there have been increasing research efforts exploiting a characteristic of speckle patterns that randomly mix an object's space and spectral information through the scattering process inside a thin disorder medium. In particular, a single-shot hyperspectral imaging is possible in that the point spread function(PSF) generated by a point of an object is spatially invariant within the range of memory effects for a thin disorder medium and the PSF is sensitive with respect to wavelength change. This is because the image formed at the output of the disordered medium can be expressed as the sum of the intensity of light formed by the convolution of the object and the PSF for various wavelengths. In this imaging scheme, the performance of the hyperspectral sensor is determined by the memory effect range of the disordered medium and the spectral resolution of the speckle. In this study, a disordered medium was fabricated by mixing ZnO nanoparticles and polydimethylsiloxane (PDMS). Memory effect range and spectral resolution were controlled by quantitatively adjusting the thickness and free scattering path of the scattering variable. In particular, as the disorder medium was stacked, the memory effect range was $0.01^\circ$ to $0.1^\circ$ level and the spectral resolution was adjustable from 0.1 nm to 10 nm level.