Spectroscopy including a source generating light profile on the sample. The light profile is movable relative to the sample. An optical input for receiving light from sample interaction with light from the source, a detector including two-dimensional array of photodetector elements, a dispersive device between the optical input and detector to spectrally disperse light from the optical input in spectral direction across the detector, an optical splitter in optical path between the optical input and detector to split light based upon wavenumber so, for a spectrum generated by a point on the sample, the spectrum first and second portions are dispersed across photodetector elements of different array row/column. Controller shifting data between photodetector elements in spatial direction, perpendicular to spectral direction, synchronously with relative movement between light profile and sample so data is accumulated on the spectrum first and second portions across different sets of photodetector elements during relative movement.