HOLOGRAM OPTICAL REPRODUCING APPARATUS AND THICKNESS MEASURING METHOD OF HOLOGRAM OPTICAL RECORDING MEDIUM

PROBLEM TO BE SOLVED: To provide a hologram optical recording and reproducing apparatus that has an optical thickness sensor capable of measuring a thickness of an optical recording medium with high accuracy, and can improve recording and reproducing performance.SOLUTION: A ray 303 from a sensor light source 220 is incident on an optical disk 207 substantially in the vertical direction to the surface of an optical disc 207 being not an oblique direction. Thereby, even if a temperature changes and the deformation such as warping is caused to a recording medium 208, an interface between the recording medium 208 and a glass substrate 209 and the interface between the recording medium 208 and the glass substrate 210 are only shifted in parallel, and the occurrence of error of measuring a thickness is suppressed. Further, a temperature in a hologram optical recording apparatus 110 is measured by a temperature sensor 225, and a decision is made whether the temperature is increased or decreased, and the decision of the thickness of the recording medium 208 is made from the interference light strength detected, and thereby a precise thickness can be detected.SELECTED DRAWING: Figure 1 【課題】光学記録媒体の厚さを高精度で測定可能な光学式厚さセンサを有し、記録再生性能を向上可能なホログラム光記録再生装置を実現する。【解決手段】センサ光源２２０からの光線３０３は光ディスク２０７の面に対して、斜め方向ではなく略垂直方向に光ディスク２０７に入射する。これにより、温度が変化し、記録媒体２０８にそり等の変形が生じても記録媒体２０８とガラス基板２０９との界面と、記録媒体２０８とガラス基板２１０との界面とは平行移動するに過ぎず、厚さ測定の誤差の発生が抑制される。さらに、温度センサ２２５により、ホログラム光記録装置１１０内の温度を測定し、温度上昇か温度下降かを判断し、検出した干渉光強度から記録媒体２０８の厚さを判断しているので、正確な厚さを検出することができる。【選択図】図１