3 September 2015 Chromatic correction for a VIS-SWIR zoom lens using optical glasses
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Abstract
With the advancement in sensors, hyperspectral imaging in short wave infrared (SWIR 0.9 μm to 1.7 μm) now has wide applications, including night vision, haze-penetrating imaging, etc. Most conventional optical glasses can be material candidates for designing in the SWIR as they transmit up to 2.2 μm. However, since SWIR is in the middle of the glasses’ major absorption wavebands in UV and IR, the flint glasses in SWIR are less dispersive than in the visible spectrum. As a result, the glass map in the SWIR is highly compressed, with crowns and flints all clustering together. Thus correcting for chromatic aberration is more challenging in the SWIR, since the Abbé number ratio of the same glass combination is reduced. Conventionally, fluorides, such as CaF2 and BaF2, are widely used in designing SWIR system due to their unique dispersion properties, even though they are notorious for poor manufacturability or even high toxicity. For lens elements in a zoom system, the ray bundle samples different sections of the each lens aperture as the lens zooms. This creates extra uncertainty in correcting chromatic aberrations. This paper focuses on using only commercially available optical glasses to color-correct a 3X dual-band zoom lens system in the VIS-SWIR. The design tools and techniques are detailed in terms of material selections to minimize the chromatic aberrations in such a large spectrum band and all zoom positions. Examples are discussed for designs with different aperture stop locations, which considerably affect the material choices.
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Yang Zhao, Yang Zhao, Daniel J. L. Williams, Daniel J. L. Williams, Peter McCarthy, Peter McCarthy, Anthony J. Visconti, Anthony J. Visconti, Julie L. Bentley, Julie L. Bentley, Duncan T. Moore, Duncan T. Moore, } "Chromatic correction for a VIS-SWIR zoom lens using optical glasses", Proc. SPIE 9580, Zoom Lenses V, 95800E (3 September 2015); doi: 10.1117/12.2187533; https://doi.org/10.1117/12.2187533
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