| 摘要 |
PROBLEM TO BE SOLVED: To enable an optical reader which can detect the arrangement position of a latent-image mark formed of a phosphorescent body layer by detecting the afterglow emitted with the mark by using a photodetecting means, while irradiating the mark with exciting light by using a projecting means, to perform mark detection with superior S/N ratio, without having to provide a wall surface for partitioning a light irradiation position and a photodetection position from each other, even when both positions are arranged close to the mark. SOLUTION: While an angle α of intersection of the optical axis L1 of the projection means 14 with the latent-image mark 12 is set obliquely from the orthogonal direction, the angle β of intersection of the optical axis L2 of the photodetecting means 16 to the latent-image mark 12 is set between the angle αand the direction orthogonal to the latent-image mark 12. Consequently, the light irradiation position and photodetection position on the latent-image mark 12 can be arranged close to each other, and mark detection with superior S/N ratio can be performed, without having to provide a wall surface shielding both positions from each other. |
