VN Absolute Specular Reflectance

Thermo Electron Corporation has introduced the VN Absolute Specular Reflectance accessory for use with its Evolution 300/600 UV-Vis spectrophotometer series. The Absolute Specular Reflectance accessory incorporates the VN optical design, which provides significant advantages over other available specular reflectance methods. The new Thermo VN accessory will have research and QC applications for anti-reflective coatings, multi-layer coatings, multilayer dielectric coatings, thin films and laser mirrors. The accessory is particularly applicable for the optical and material science industries where Thermo is already well-known for its leading FT-IR solutions.Thermo’s new VN accessory offers significant design advantages over traditional relative and VW specular reflectance accessories. Unlike relative designs, Thermo’s VN accessory is highly accurate and does not require the purchasing of expensive calibrated specular standards, such as first-surface aluminium mirrors to obtain absolute measurements. The Thermo accessory is also not dependent on maintaining the quality of the standard surface, which can introduce erroneous results.

With the VW design accessory, the light bounces off the sample surface twice, requiring a larger sample surface to accommodate two reflections. In addition, because two separate areas of the sample surface are measured, errors may result if the sample is not homogeneous. Also, the measurement accuracy of low reflectance samples such as anti-reflective coatings or laser mirrors is limited by the VW design, unlike the VN design.