The detector is a microbolometer camera FLIR A65SC, comprising a 640×512-pixel focal plane array with a pixel pitch of 17 μm and operating at 30 Hz. The camera has a noise equivalent temperature difference (NETD) of 50 mK and a digital output range of 14 bits. The spectral response of the camera covers the 1400–700 cm-1 band.
To prevent the sample surface from heating, a Ge filter is applied to the ZnSe lens that concentrates light on the sample plane.
An aluminum reflector collects the light, directing a 35-mm beam towards a compact Michelson interferometer comprising a ZnSe beamsplitter, a ZnSe compensation plate and two gold retroreflectors.
A stabilized silicon nitride globar lamp (Thorlabs) is the light source, providing 200mW over the 700–1400 cm−1 spectral range with 0.05% output power fluctuation.
The painting or other sample under investigation is positioned for successful imaging. Position-adjustable staging is used to hold the sample.