Patent ID: 7492692

Claim:
A hologram recording and reproducing apparatus comprising: a recording unit which records information on a holographic recording medium by recording interference fringes formed by irradiating an object light corresponding to recording information and a reference light; a reproducing unit which generates detected information data and a focus error signal based on detected light from the holographic recording medium; and a focus servo unit which performs focus servo based on the focus error signal, wherein the focus servo unit comprises a servo target value setting unit which sets a target value for the focus servo based on the detected information data, wherein the servo target value setting unit comprises: a unit which detects a distance between two markers included in the detected information data; and a setting unit which sets the target value for the focus servo based on a result of a comparison of the distance between the markers with a distance reference value, wherein the recording unit comprises a spatial modulator which spatially modulates light from a light source based on the recording information to generate the object light, and wherein the distance reference value is a distance between the two markers on the spatial modulator.