To provide an optical information recording and reproducing apparatus capable of correct positioning, in an optical information recording and reproducing apparatus which branches a light beam into reference light and signal light to cause interference and records an obtained interference fringe as a hologram on an optical information recording medium and reproduces the hologram recorded by applying the reference light onto the optical information recording medium, the apparatus has an image pickup element which detects reproduction light passing through an aperture 101 in reproduction light obtained by applying the reference light onto the optical information recording medium and generates a reproduction signal, photo detectors 104a, 104b, 104c, and 104d that are different from the image pickup element and detect reproduction light applied on a location on the periphery of the aperture 101, and a computing unit which computes a position error signal based on outputs from the photo detectors.

A method of performing a write operation in a holographic data storage system, in which schedule schedules at least one write operation across multiple non-contiguous write intervals, the write operation pertaining to a set of data to be stored in a region of a holographic recording medium. In each of the non-contiguous write intervals, the region of the holographic recording medium is exposed to an interference pattern caused by interference between a reference beam and an input beam carrying the set of data. The multiple non-contiguous write intervals have a total aggregate duration of sufficient length to cause a persistent state change in the exposed region, such that the set of data is recoverable from that region by the end of a final write interval of the multiple non-contiguous write intervals.