Transmission is an important parameter of an optic affecting its performance. For polymer optics, transmission is typically limited by Fresnel reflection, scatter, and material absorption.
Fresnel reflection is a function of index of refraction and can be reduced by applying an anti-reflection coating. Scatter is caused by surface roughness, surface imperfections, and material imperfections, and can be reduced by optimizing the manufacturing process.
Absorption is mostly a property of the material. Thermoplastic resins used for injection molding transmit quite well in the visible and near-infrared spectrum, but have very limited transmission in the ultra-violet, mid-wave infrared, and long-wave infrared ranges. The chart below shows typical transmission curves for commonly used thermoplastic materials.
Material transmission can be altered by mixing and blending a base polymer with additives to achieve a specific spectral response. These additives can block this material transmission in certain ranges or modify its color.
Transmission was measured on 1-3 mm thick uncoated witness samples using a PerkinElmer Model 950 UV/VIS spectrophotometer.
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