Multi-layer information storage system with improved aberration correction

  • US 5,677,903 A
  • Filed: 09/01/1994
  • Issued: 10/14/1997
  • Est. Priority Date: 03/25/1991
  • Status: Expired due to Term
First Claim
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1. An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers,and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers,characterized in that the focusing means introduce such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.

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