Method of recording a multi-layer optically recordable information carrier

Abstract

The application relates to a method of and an apparatus for writing information onto a multi-layer optical information carrier ( 1 ). In an optical recording system information can be written onto a selected layer ( 41 ) of a multi-layer carrier ( 1 ) by focusing the laser beam ( 2 ) onto the selected layer. Intermediate layers ( 42 ) interact with the laser beam ( 2 ). An important property in writing information onto a multi-layer carrier ( 1 ) is the transmission coefficient of these intermediate layers ( 42 ). The transmission coefficient depends on the physical properties of the intermediate layer ( 42 ) and on whether or not information has been recorded. The apparatus includes a circuit ( 55 ) which derives information ( 711 ) about the changes of the transmission coefficients of the layers ( 41 through 43 ) when information is written onto these layers. On the basis of this information ( 711 ) a circuit determines the sequence in which the layers ( 41 through 43 ) are to be recorded. The sequence can be selected so as to minimize the intensity of the laser beam ( 2 ), thereby precluding unnecessary heating of the carrier ( 1 ) and allowing comparatively simple and cheap laser beam sources ( 3 ) to be used.

1 . A method of recording information onto an optically recordable information carrier having at least two superposed optically recordable layers, comprising 
 a first step in which information is recorded on a first one of the optically recordable layers by means of laser light to which the information carrier is exposed from a first side, followed by    a second step in which information is recorded on a second one of the optically recordable layers, which second layer differs from the first layer, by means of laser light to which the information carrier is also exposed from the first side, characterized in that the method comprises    a first preparatory step in which the changes of the effective transmission properties of the optically recordable layers before the recording of information on the layers with respect to the effective transmission properties of the optically recordable layers after the recording of information on the layers is determined, followed by    a second preparatory step in which the sequence of recording of the first and the second optically recordable layer is determined.    
     
     
         2 . A method as claimed in  claim 1 , characterized in that the first preparatory step comprises the reading of information about the changes of the effective transmission properties of the optically recordable layers from an area on the optically recordable information carrier, which area contains information about the physical properties of the optically recordable information carrier.  
     
     
         3 . A method as claimed in  claim 1 , characterized in that the first preparatory step comprises 
 a first measurement step in which the effective transmission properties of the optically recordable layers before the recording of information on the layers is measured, followed by    a second measurement step in which the effective transmission properties of the optically recordable layers after the recording of information on the layers is measured, followed by    a comparison step in which the measured effective transmission properties of the optically recordable layers before the recording of information on the layers is compared with measured effective transmission properties of the optically recordable layers after the recording of information on the layers.    
     
     
         4 . A method as claimed in  claim 1 ,  2  or  3 , characterized in that the first and the second optically recordable layer are inscribed successively, starting with the optically recordable layer situated farther from the laser light source and ending with the optically recordable layer situated nearer the laser light source if the effective transmission properties of the optically recordable layers after the recording of information on the layers have decreased with respect to the effective transmission properties of the optically recordable layers before the recording of information on the layers.  
     
     
         5 . A method as claimed in  claim 1 ,  2  or  3 , characterized in that the first and the second optically recordable layer are inscribed successively, starting with the optically recordable layer situated nearer the laser light source and ending with the optically recordable layer situated farther from the laser light source if the effective transmission properties of the optically recordable layers after the recording of information on the layers have increased with respect to the effective transmission properties of the optically recordable layers before the recording of information on the layers.  
     
     
         6 . A recording apparatus for the recording of information on an optically recordable information carrier having at least two superposed optically recordable layers, comprising a device adapted to record information on a first one of the optically recordable layers by means of laser light to which the information carrier is exposed from a first side, and to record information on a second one of the optically recordable layers, which second layer differs from the first layer, by means of laser light to which the information carrier is also exposed from the first side, characterized in that 
 the recording apparatus is adapted to determine the changes of the effective transmission properties of the optically recordable layers before the recording of information on the layers with respect to the effective transmission properties of the optically recordable layers after the recording of information on the layers, and    the recording apparatus is adapted to determine the sequence of recording of the first and the second optically recordable layer.