| 摘要 |
PURPOSE:To reduce influence due to dust, etc., attached on an optical recording medium and to exactly read information by arranging a light source by shifting from the focal point position of a collimator lens, and illuminating the optical recording medium in a de-focusing state. CONSTITUTION:In an optical information reader in which light from the light source is projected on the optical recording medium formed by laminating transparent layers 1b on a recording layer 1a via the collimator lens 3 and an objective lens 6 in spot shape and the information recorded on the recording layer is read from the reflected light, the optical recording medium is constituted in such a way that the light source is arranged by shifting from the focal point position of the collimator lens 3 and the medium is illuminated in the de-focusing state so that a spot area on a transparent layer 2 by the reflected light at the recording layer 1a can be formed larger than that on the recording layer. In such a way, it is possible to increase an illumination area on the recording medium, and also, to reduce the influence due to the dust, etc., on the transparent layer and to always read the information accurately in spite of the size of track width. |
