| 摘要 |
PURPOSE: To suppress reading out of information from adjacent tracks and to reproduce only the information of objective tracks by setting the inter-track difference in level of first and second grooves at a prescribed value and forming amplitude marks larger than the width of the tracks in any of the tracks of the two groups. CONSTITUTION: The projecting tracks 2 and recessed tracks 3 are alternately formed on the front surface of a substrate 1. Signal recording layers 4 consisting of phase shift thin films are formed on the front surface of the substrate 1. The amplitude marks 5 different in reflectivity of light from the ambient by the characteristics of the phase shift thin films are formed in the projecting tracks 2. The width of the marks 5 is slightly larger than the width of the projecting tracks and both ends thereof arrive at the adjacent recessed tracks. Then, the reading light reflected on the projecting tracks and the recessed tracks induces the interference. On the other hand, the recessed tracks have the difference in level of odd times of π in the phase difference of the light reflected on the surfaces of both with respect to the projecting tracks and, therefore, the crosstalks by the amplitude marks on the adjacent projecting tracks are drastically decreased as a result of the interference. Then, the drastic narrowing of the track pitches is possible and the higher density recording is possible. |
