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OPTICAL MEMORY WITH REFERENCE CHANNEL TO COMPENSATE FOR DETERIORATION

  • US 3,720,923 A
  • Filed: 07/06/1971
  • Issued: 03/13/1973
  • Est. Priority Date: 07/06/1971
  • Status: Expired due to Term
First Claim
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1. In a beam addressed optical mass memory having an alterable memory medium exhibiting a change in its optical properties as a function of write-rewrite cycles, and having means for writing and rewriting bits on the memory medium, an improvement comprising:

  • a block of recorded bits comprising, a plurality of alterable information bits recorded on the memory medium, and an alterable reference bit recorded on the memory medium, the reference bit being subjected to a number of writ-rewrite cycles essentially equal to the average number of write-rewrite cycles to which one of the plurality of information bits is subjected, light source means for providing a light beam, light beam addressing means for directing the light beam to the reference bit and then to each of the plurality of information bits, radiation detector means for receiving a light beam from the reference bit and from each of the plurality of information bits and for producing a reference signal indicative of the intensity of the light beam received from the reference bit and then information signals indicative of the intensity of the light beam received from each of the plurality of information bits, switching means for directing the reference signal to a reference channel and sequentially directing each of the information signals to an information channel, temporary storage means connected in the reference channel for storing the reference signal until each of the information signals is directed to the information channel, and electric signal comparing means for receiving signals from the reference and information channels and comparing the reference signal to each of the information signals and producing a plurality of output signals indicative of the comparison of the reference signal and each of the information signals.

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