A new optical accessory for simultaneous measurements of reflectance and transmittance at continuously variable angles

A new optical accessory is equipped with two spheroidal mirrors, which completely cover a sample on the equatorial plane. It is possible to make simultaneous measurements of reflectance and transmittance at continuously variable angles. The geometric mean of two reflectance (or transmittance) values gives us the absolute reflectance (or transmittance) because of the independence of the reflectance difference of the individual mirrors and the optical loss at each mirror. The accessory achieves spectral measurements with high accuracy and within a short period of time and is designed as it can be incorporated into commercial spectrometers.