Patent ID: 7616362

Claim:
A hologram recording and reproducing apparatus in which coherent light emitted from a light source is split into a recording beam and a reference beam, the recording beam and the reference beam being superposed on a hologram recording medium for recording a hologram on the hologram recording medium, and in which the hologram recording medium is irradiated with the reference beam for reproducing recorded information based on the hologram, and a reflected beam from the hologram recording medium is detected with an optical detector, the apparatus comprising: a movable optical device that guides the reference beam toward the hologram recording medium, and that changes an incident angle of the reference beam with respect to the hologram recording medium; an optical device controller that causes the movable optical device to move so as to set the incident angle at a specified angle in recording the hologram on the hologram recording medium, the optical device controller also causing the movable optical device to move in reproducing the recorded information based on the hologram so that the incident angle of the reference beam with respect to the hologram recording medium increases from the specified angle when the wavelength of the coherent light emitted from the light source becomes greater at the time of reproducing than at the time of recording; and a reproduction unit that receives a detection signal from the optical detector while the incident angle changes continuously, the detection signal corresponding to intensity of the reflected beam, the reproduction unit reproducing the recorded information based on the detection signal when the intensity of the reflected beam is no lower than a specified level or reaches a maximum level; wherein the specified angle is set at a plurality of different values for performing hologram multi-recording on the hologram recording medium; and wherein the incident angle is set at the respective different values in reproducing the recorded information based on the hologram, and for each of the different values, the incident angle is continuously changed from said each of the different values within a specified range when the wavelength of the coherent light emitted from the light source becomes greater at the time of reproducing than at the time of recording, said specified range being narrower than an interval between the different values.