Cascaded, self-calibrated, single-pixel mid-infrared Hadamard transform spectrometer.

In this paper, a single-pixel mid-infrared (mid-IR) Hadamard transform spectrometer is developed. The spectrometer's design, fabrication and experimental results are discussed. The single-pixel mid-IR Hadamard transform spectrometer has dual cascaded encoding regions, 2875 nm to 3500 nm and 3500 nm to 4077 nm, to reduce the travel range required by the moving mask. The encoded wavelength band is determined by the bandpass filter used. A collection optics consisting of a reverse spectrometer is used to collect the encoded signal onto a single-pixel detector with a small sensing area. A 635 nm laser is used as a reference within the spectrometer to calibrate the recovered spectrum with accurate positioning. Our experiments demonstrate that mid-IR spectrums can be accurately recovered in the designed wavelength range. The proposed spectrometer, with dimensions of 200 mm × 200 mm × 84 mm and a weight of 1.8 kg, can be made portable and at low cost, suitable for IR spectroscopy in the field.