Infrared spectroscopy (sometimes called Infrared spectrometry) is a physical analysis method that uses infrared light. Typically, infrared spectroscopy uses a wavelength between 800nm and 1mm. The method can be used for quantitative analyses of unknown substances, or of the structural properties of known substances. Raman spectroscopy is another method that produces similar results. The main method used in infrared spectroscopy today is Fourier transform infrared spectroscopy, which uses Fourier transforms.