METHOD AND APPARATUS FOR SYNCHRONIZING PHOTOGRAPHIC RECORDS OF DIGITAL INFORMATION

• US 3,795,902 A
• Filed: 11/26/1971
• Issued: 03/05/1974
• Est. Priority Date: 09/01/1966
• Status: Expired due to Term

• Current Assignee: Optical Recording Corp.
• Original Assignee: James T. Russell
• Inventors: Russell, James T.
• Primary Examiner(s): Fears, Terrell W.
• Application Number:
  US05/202,539
• Time in Patent Office: 830 Days
• Field of Search: 178/6.6R,6.7R,6.7A 340/173LM 179/1.3D 250/219D
• US Class Current: 369/47.28
• CPC Class Codes: G11B 20/1403 characterised by the use of two levels
• CPC Class Codes: G11B 2220/218 Write-once discs
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: G11B 7/00 Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor G11B11/00, G11B13/00 take precedence
• CPC Class Codes: G11B 7/0033 with cards or other card-like flat carriers, e.g. flat sheets of optical film
• CPC Class Codes: G11C 13/04 using optical elements ; using other beam accessed elements, e.g. electron or ion beam
• CPC Class Codes: H04N 3/08 having a moving reflector
• CPC Class Codes: H04N 5/76 Television signal recording
• CPC Class Codes: H04N 5/85 on discs or drums
• CPC Class Codes: H04N 5/926 by pulse code modulation H04N5/919 takes precedence
• CPC Class Codes: H04N 5/935 Regeneration of digital synchronisation signals
• CPC Class Codes: H04N 5/95 Time-base error compensation H04N5/932 takes precedence

Abstract

An electrical signal recording and playback system is described in which an analog input signal is converted to a digital signal that pulses a light source to form a single, series-recorded track of binary coded digital information including information spots arranged in groups, which track is played back in a similar manner. The photographic film is a compact, permanent record of long, useful lifetime which may be photographically copied to provide a plurality of inexpensive copies. Recorded information is synchronized for playback by detecting a configuration of the digital signal, either from known characteristics of the signal or from information added to the signal during recording. The information thus read out is suitably employed for shifting digital words in a reassembly shift register until proper word synchronization is achieved.

Claims

1. The method of synchronizing an optical recording of the type comprising a track of a plurality of small spots representing digital bits recorded at high density on a photographic record by light source means, and readable through optically scanning said recording along said track for producing electrical pulses, said method comprising:

serially recording said digital bits in word groups of spots of substantially similar size having a data configuration representative of desired output information and also representative, by the configuration of digital bits, of the identification of word groups along said track, detecting a configuration representative of word group location, scanning the recording to read the digital bits of the record and synchronizing the reading of the same according to word group location so that word groups of said information can be individually read out.

2. The method according to claim 1 wherein said track is organized into raster lines, said method including recording a digital bit at a predetermined location on each line, said last mentioned bit having a predetermined value, said synchronizing during playback including resetting word synchronization upon receipt of a said bit of predetermined value at said location for each raster line.

3. The method according to claim 1 wherein predetermined words of digital bits are recorded with a predetermined code value, and said detection including recognizing such a coded word for resynchronizing readout.

4. The method according to claim 1 wherein each word is provided with at least one bit of predetermined value, said detection including reading said bit position, and said synchronizing including shifting readout information until said bit position continues to indicate said predetermined value.

5. The method according to claim 1 wherein said detection includes detecting unused data configuration, said synchronizing including shifting data read until such data configuration is not detected.

6. The method according to claim 1 wherein said detection includes comparing the pulse rate of a sign bit with a least significant bit of a word and wherein said synchronizing includes shifting data read until the comparison indicates a predetermined ratio between the two.

7. The method according to claim 1 wherein said detection includes detecting the frequency of a given bit, and shifting data until said bit has a predetermined frequency.

8. The method according to claim 7 wherein said given bit is a predetermined bit position.

9. The method according to claim 8 wherein a predetermined bit value is recorded with a fixed recording rate at such predetermined bit position.

10. The method according to claim 1 including adding a given digital signal to the digital bits of the recording, wherein said detection includes separating said additional signal on readout, and said synchronizing including shifting information until a predetermined added signal is detected.

11. The method according to claim 1 including adding a parity bit to each word, detecting parity, and shifting information until the proper synchronization is indicated.

12. The method according to claim 1 wherein certain of said spots have predetermined shapes, said detecting including optically masking light for readout of said spots to detect said spots of predetermined sHape.

13. The method according to claim 1 wherein certain of said spots are offset with respect to said track, for indicating synchronization, said detecting including differentially detecting said spots relative to said track to indicate such offset.

14. The method according to claim 1 including recording said spots at separate depths of said record and detecting by optically reading out said information at separate image locations corresponding to said separate depths, one of said depths including synchronizing information.

15. The method according to claim 1 including recording said spots in different colored layers in said record and separately detecting said spots by optically reading out said information by color selective light detectors, one of said colored layers including synchronizing information.