A method and an apparatus for examining the subsurface microstructure of a sample are provided. Radiation from a plurality of optical radiation sources travels along a first optical path. In the first optical path, a device focuses the optical radiati n from each of the optical sources into a plurality of respective focal points along the first optical path to provide substantially continuous coverage of a selected portion of the first optical path. Then, a sample on the first optical path within the selected length extending into the sample is scanned along said selected portion of the first optical path.