Abstract
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.
Highlights
Red Edge Simple Ratio Index and a Water Band Index
DesignWorks of a spectral device for measuring a single vegetation index based on spectral that rely on such an approach have already been published, with a diffractive diffractive lenses (SDL)
SDLs enable several wavelengths of light to beaberrations focused ininthe plane but In in difthis work, we propose the design of a spectral device for measuring a single vegetation ferent diffraction orders, e.g., with wavelengths λ1 and λ2 being, respectively, imaged in on spectral diffractive lenses (SDL).asAamethod for designing
Summary
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. [29] discussed the use of a special narrowband illumination source in place of a sophisticated setup for wavelength separation, which has made it possible to create a very cheap setup for multispectral imaging, though applicable only in laboratory conditions. Works that rely on such an approach have already been published, with a diffractive lens array utilized for setup for wavelength separation, which has made it possible to create a very cheap setup wavelength separation in Ref. [30], resulting in a compact setup for measuring the NDVI for multispectral imaging, though applicable only in laboratory conditions It index butappropriate suffering from highaaberrations in the off-axis. DesignWorks of a spectral device for measuring a single vegetation index based on spectral that rely on such an approach have already been published, with a diffractive diffractive lenses (SDL)
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