Atmospheric Aerosol Multiband Synthesis Imaging Spectrometer

Monolithic Miniature Glass Spectrometer

This paper presents a monolithic spectrometer based on a plano-convex glass lens and achieves a resolution better than 0.7 nm in the spectral range of 550-720 nm. In the monolithic instrument, all components were fixed in the machined lens, resulting in a much smaller size and more stable assembly than traditional mini spectrometers. Additionally, a dual-band design was proposed and demonstrated to extend the spectral range from the visible band (550-700 nm) to the near-infrared band (800-900 nm), thus allowing more characteristic spectral fingerprints for improved material identification. The feasibility of compensating the residual aberrations caused by structural limitations with a specifically designed aberration-correcting grating is further detailed.

Spectral Diffractive Lenses for Measuring a Modified Red Edge Simple Ratio Index and a Water Band Index

We propose a novel type of spectral diffractive lenses that operate in the ±1-st diffraction orders. Such spectral lenses generate a sharp image of the wavelengths of interest in the +1-st and -1-st diffraction orders. The spectral lenses are convenient to use for obtaining remotely sensed vegetation index images instead of full-fledged hyperspectral images. We discuss the design and fabrication of spectral diffractive lenses for measuring vegetation indices, which include a Modified Red Edge Simple Ratio Index and a Water Band Index. We report synthesizing diffractive lenses with a microrelief thickness of 4 µm using the direct laser writing in a photoresist. The use of the fabricated spectral lenses in a prototype scheme of an imaging sensor for index measurements is discussed. Distributions of the aforesaid spectral indices are obtained by the linear scanning of vegetation specimens. Using a linear scanning of vegetation samples, distributions of the above-said water band index were experimentally measured.