A simple optical detector of position versus time providing submillimeter spatial and nanosecond time resolution is described. The spatial beam profile of a nanosecond‐pulse‐width nitrogen laser is sampled simultaneously when the UV light strikes multiple turns of a spiral fiber‐optic delay line. Fluorescent light coupled into the fiber converts the profile samples into serial bursts of light. These bursts are detected by avalanche photodiodes; electrical pulses are recorded on fast oscilloscopes. An interposed absorbing or refracting material casts a ‘‘shadow’’ which is measured by comparison with a reference recording. Applications are suggested, and two long‐time‐base recording methods are described.