1. An optical system comprising: an assembly arranged to collect short coherence length light from a sample; a spectrograph including a dispersing element and detector array; an interferometer arranged to receive the light collected from said sample, divide said collected light into at least two optical paths, make a fixed delay of light passing along one of said paths relative to light passing along another of said paths, recombine the collected light and pass the recombined collected light as recombined self-interfering light to said spectrograph, said interferometer being operative on at least a portion of the light collected from the sample; wherein said spectrograph produces a self-interference signal from the recombined self-interfering light collected from the sample, the signal being representative of structure of said sample over a depth and corresponding to said delay, wherein the assembly collects light from a line or region of the sample located at a depth and the system includes a processor configured to process the self-interference signal to produce an image of that line or region.