Method and apparatus for recording/reproducing optical information

Abstract

A substrate ( 1 ) having a guide groove for tracking with spot irradiation light beam for recording/reproduction of information is provided with a recording layer ( 2 ) and a light transmitting layer ( 3 ). The recording layer ( 2 ) is irradiated with a spot light beam through the light transmitting layer ( 3 ) to record information on both a first portion (L′) of the recording layer corresponding to a flat section (L) between adjacent guide grooves and a second portion (G′) of the recording layer corresponding to a guide groove inside (G). Recording marks with mark lengths of nT-mT (where T is a unit length, n, m are integers of one or more, n<m) are formed on the first and second portions (L′, G′). The amplitude IL 1 of a reproduced signal from the longest recording mark with the mark length of mT recorded on the first portion (L′) and the amplitude IL 2 of a reproduced signal from the longest recording mark with the mark length of mT recorded on the second portion (G′) satisfy the relation 1<(IL 1 /IL 2 )<1.3.

1 . An optical information recording medium in which light is projected in a spot to thereby record/reproduce information and in which at least a recording layer and a light-transmitting layer are disposed in this order on a substrate having a guide groove for tracking of the spotted light and in which the light is projected in the spot to the recording layer from the side of the light-transmitting layer to record the information both in a first portion of the recording layer corresponding to a flat portion between mutually adjacent guide grooves and a second portion of the recording layer corresponding to the inside of the guide groove, 
 wherein a reflectance of the recording layer drops when the recording is performed with respect to the recording layer, and a difference Δφ=φa−φc between a phase φa of reflected light after the recording and a phase φc of the reflected light before the recording satisfies a relation of 0°<Δφ≦15°.    
   
   
       2 . An optical information recording medium in which light is projected in a spot to thereby record/reproduce information and in which at least a recording layer and a light-transmitting layer are disposed in this order on a substrate having a guide groove for tracking of the spotted light and in which the light is projected in the spot to the recording layer from the side of the light-transmitting layer to record the information both in a first portion of the recording layer corresponding to a flat portion between mutually adjacent guide grooves and a second portion of the recording layer corresponding to the inside of the guide groove, 
 wherein a reflectance of the recording layer increases when the recording is performed with respect to the recording layer, and a difference Δφ=φa−φc between a phase φa of reflected light after the recording and a phase φc of the reflected light before the recording satisfies a relation of −15°≦Δφ<0°.    
   
   
       3 . An optical information recording medium in which light is projected in a spot to thereby record/reproduce information and in which at least a recording layer is disposed on a substrate having a guide groove for tracking of the spotted light and in which the light is projected in the spot to the recording layer from the side of the substrate to record the information both in a first portion of the recording layer corresponding to a flat portion between mutually adjacent guide grooves and a second portion of the recording layer corresponding to the inside of the guide groove, 
 wherein a reflectance of the recording layer drops when the recording is performed with respect to the recording layer, and a difference Δφ=φa−φc between a phase φa of reflected light after the recording and a phase φc of the reflected light before the recording satisfies a relation of 0°<Δφ≦15°.    
   
   
       4 . An optical information recording medium in which light is projected in a spot to thereby record/reproduce information and in which at least a recording layer is disposed on a substrate having a guide groove for tracking of the spotted light and in which the light is projected in the spot to the recording layer from the side of the substrate to record the information both in a first portion of the recording layer corresponding to a flat portion between mutually adjacent guide grooves and a second portion of the recording layer corresponding to the inside of the guide groove, 
 wherein a reflectance of the recording layer increases when the recording is performed with respect to the recording layer, and a difference Δφ=φa−φc between a phase φa of reflected light after the recording and a phase φc of the reflected light before the recording satisfies a relation of −15°≦Δφ<0°.    
   
   
       5 . A method of recording/reproducing optical information, comprising the steps of: projecting light in spots with respect to both first and second portions of a recording layer of the optical information recording medium according to  claim 1;  lowering a reflectance of the recording layer; and forming recording marks having mark lengths nT to mT to perform recording, so that Δφ satisfies a relation of 0°<Δφ≦15°.  
   
   
       6 . A method of recording/reproducing optical information, comprising the steps of: projecting light in spots with respect to both first and second portions of a recording layer of the optical information recording medium according to  claim 2;  increasing a reflectance of the recording layer; and forming recording marks having mark lengths nT to mT to perform recording, so that Δφ satisfies a relation of −15≦Δφ<0°.