Numerical methods are proposed for expanding the dynamic range and increasing the quantization resolution of Fourier transform infrared spectrum data. In these methods, an interferogram is oversampled at a rate higher than the Nyquist sampling rate. From the oversampled interferogram data, the full-range interferogram or the lost quantization bits are recovered by using the Gerchberg-Papoulis iterative algorithm, incorporating constraints on the amplitude range of the interferogram and on the band limitation and non-negativity of the spectrum. Experimental results for IR absorption spectra of cyclohexene are shown in order to demonstrate the capabilities of the methods.
