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

• Current Assignee: Di Chen, James Davis Zook
• Original Assignee: Di Chen, James Davis Zook
• Inventors: Chen, Di, Zook, James Davis
• Primary Examiner(s): Konick, Bernard
• Assistant Examiner(s): Hecker, Stuart
• Application Number:
  US05/159,896
• Time in Patent Office: 616 Days
• Field of Search: 340/173LM,174YC,174GA 350/16R 346/17R 178/15
• US Class Current: 365/122
• CPC Class Codes: G11B 11/10515 Reproducing compensating pit shift G11B11/1053
• CPC Class Codes: G11B 11/10595 Control of operating function
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/14 using self-clocking codes
• CPC Class Codes: G11B 2220/2525 Magneto-optical [MO] discs
• CPC Class Codes: G11B 5/00 Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor G11B11/00 and G11B13/00 take precedence
• CPC Class Codes: G11B 7/24085 Pits

Abstract

A beam addressed optical mass memory utilizes an alterable memory medium which exhibits a change in its optical properties as a function of time or as a function of write-rewrite cycles. A reference bit is recorded on the memory medium and one or more information bits are similarly recorded. The reference and information bits are subjected to essentially the same number of write-rewrite cycles, and therefore exhibit essentially identical changes in optical properties. Information is read out by sequentially directing the light beam to the reference bit and the information bits. A detector produces a reference signal indicative of the intensity of the light beam received from the reference bit and produces information signals indicative of the intensity of the light beam from each of the information bits. The reference signal is directed to a reference channel and temporarily stored. Each of the information signals is directed to an information channel. The reference signal is compared to each of the information signals and readout signals are produced which are indicative of the difference between or the ratio of the reference signal and each of the information signals.

Claims

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.

2. The invention as described in claim 1 wherein the erasable medium is a magnetic film.

3. The invention as described in claim 2 wherein the magnetic film is a manganese bismuth film.

4. 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 reference track on the memory medium having a plurality of alterable reference bits, an information track on the memory medium having a plurality of alterable information bits, the information track being adjacent the reference track, the reference and information bits being subject to essentially the same number of wRite-rewrite cycles, light source means for providing a light beam, light beam addressing means for sequentially deflecting the light beam from a bit in one of the tracks to a bit in the other of the tracks, radiation detector means for receiving the light beam from each of the reference and information bits and alternatively producing a reference signal indicative of the intensity of the light beam received from a reference bit and then an information signal indicative of the intensity of the light beam received from an information bit, switching means for directing the reference signal to a reference channel and the information signal to an information channel, temporary storage means connected in the reference channel for storing the reference signal until another reference signal is directed to the reference channel, and electrical signal comparing means for receiving signals from the reference and information channels and producing an output signal indicative of the comparison of the reference and the information signals.

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

6. 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 first and second alterable reference bits recorded on the memory medium, and a first alterable information bit recorded on the memory medium, light source means for providing a light beam, light beam addressing means for directing the light beam to the first reference bit, then to the first information bit, and then to the second reference bit, radiation detector means for receiving the light beam from the block of recorded bits and for producing a first reference signal indicative of the intensity of the light beam received from the first reference bit, then producing after a first time duration T1 after the first reference signal a first information signal indicative of the intensity of the light beam received from the first information bit, and producing after a second time duration T2 after the first information signal a second reference signal indicative of the intensity of the light beam received from the second reference bit, swItching means for directing the first reference signal to a reference channel, then directing the first information signal to an information channel, and then directing the second reference signal to the reference channel, first temporary storage means connected in the reference channel for storage of the reference signals for a time duration equal to the sum of the first time duration T1 and the second time duration T2, second temporary storage means connected in the information channel for storing the first information signal for a time duration equal to second time duration T2, signal averaging means connected in the reference channel for receiving the first reference signal from the second temporary storage means and for receiving the second reference signal prior to its storage in the second temporary storage means, the signal averaging means producing an average reference signal equal to the average of the first and second reference signals, and electric signal comparing means for receiving the first information signal from the information channel and the average reference signal from the reference channel and for producing an output signal indicative of the comparison of the first information signal and the average reference signal.

7. The invention as described in claim 6 wherein the first temporary storage means comprises a delay line for providing a time delay of a duration equal to second time duration T2.

8. The invention as described in claim 6 wherein the second temporary storage means comprises a delay line for providing a time delay of a duration equal to the sum of the first time duration T1 and the second time duration T2.