This Variable Angle Transmission Accessory is excellent for examining thick samples and optical coatings thereon at any angle using transmission spectroscopy. When light impinges on a thick sample at an angle, the light reflects from both surfaces of the sample. The transmitted light is parallel to the incident light but slightly shifted. The measured transmittance is altered by this misalignment of the beam. The Variable Angle Transmission Accessory eliminates this by allowing a sample and a blank to be placed in the beam at the same angle but in opposing directions. Using a blank which matches the sample in thickness and refractive index shifts the transmitted beam back to the original position. This accessory incorporates a holder for an optional polarizer. For optimum performance with inherently polarized beams, the accessory can be rotated 90° around the beam axis. This accessory is designed for FT-IR or UV-Vis transmission studies of samples up to 6 mm thick and up to 10 mm thick with its included thick sample holder.