Spatial Resolution in ATR FT-IR Imaging: Measurement and Interpretation

ATR FT-IR imaging with germanium crystals offers the potential for acquiring infrared spectral images at up to four times higher spatial resolution than is possible using conventional reflectance or transmission imaging. There is often some confusion over the meaning and inter-relationship of terms such as “spatial resolution,” “pixel size” or “sampling interval,” and it may be hard to understand how any given system’s specifications will affect the imaging of a particular sample. Using the PerkinElmer ATR FT-IR Imaging Accessory with the SpotlightTM FT-IR Imaging System as an example, this note explains what is meant by spatial resolution and sets out a generally applicable method for its measurement on any imaging system. Guidance is given regarding practical questions such as “can this instrument see a feature in my sample which is only X microns wide?”