Like OCT, the early implementations of a/LCI relied on physically changing the optical path length (OPL) to control the depth in the sample from which data are acquired. However, it has been demonstrated that it is possible to use a Fourier domain implementation to yield depth resolution in a single data acquisition. A broadband light source is used to produce a spectrum of wavelengths at once, and the backscattered light is collected by a coherent optical fiber in the return path to capture different scattering angles simultaneously. Intensity is then measured via a spectrometer: a single frame from the spectrometer contains scattering intensity as a function of wavelength and angle. Finally the data is Fourier transformed on a line-by-line basis to generate scattering intensity as a function of OPL and angle. In the resulting image, the x axis represents the OPL and the y axis the angle of reflection, thus yielding a 2D map of reflection intensities.
Using this method, the acquisition speed is limited only by the integration time of the spectrometer and can be as short at 20 ms. The same data that initially required tens of minutes to acquire can be acquired ~10 times faster.