The time-resolved absorption spectrum of singlet oxygen [O₂(a¹Δ_g) → O₂(b¹Σ_g )] has been recorded in the region ∼5100–5300 cm⁻¹ from air-saturated polystyrene samples using a microscope attached to a step-scan Fourier transform IR spectrometer. Singlet oxygen signals were observed with a time resolution of ∼160 ns from sample volumes of ∼20 nL using moderate data-acquisition times. These data indicate that it is reasonable and worthwhile to consider the further development of a transmission microscope as a viable tool to create singlet oxygen images of inhomogeneous samples including samples of biological importance.