Photoluminescence is a widely used tool for the characterization of wide-gap semiconductor materials. However, most narrow-gap, infrared materials exhibit very weak, hard to detect photoluminescence. We report on the development of a sensitive, Fourier transform infrared (FTIR)-based apparatus capable of measuring and spatial imaging of weak infrared photoluminescence with diffraction limited resolution. The apparatus is also capable of measuring transmittance and phototransmittance. This is, to our knowledge, the first report of measuring infrared phototransmittance using an FTIR spectrometer.