Patent Publication Number: US-3877069-A

Title: Skew correction system

Description:
United States Patent 1 [111 3,377,069 Altonjietal. [451 Apr. s, 1975 1 SKEW CORRECTION SYSTEM means being operatively connected to said [75] inventors: Edmund R. Altonji, Pcquannock. f and playback me?n5 for stomge of Nhmng orenck&#39;Meno Park information on a multiplicity of information Calif. channels.  
  synchronizing means. operatively connected to said [73] Assignee: The United States of America as rdi a d playback m a s represented by the Secretary of the synchronizing signal generating means. said y. wilshiiigwm synchronizing signal generating means being [22] Wed: 26 963 operatively connected to said recording means whereby said synchronizing signal generating H PP N05 326304 means generates synchronizing signals for storage upon said information storage means. and [52] us Cl 360/26; H04 phase shift control means. said phase shift control [5i] lnt. Cl G09!) 9/00; or lb 5/02 means peraiwely Playback means [58] Field of Search 3s/\o.4-. 343/1001; 9&#34; f fmm 340M741. 79001; 360/26 the information stored on said storage means whereby said phase sh|ft control means vary the l 56] R&#39;hrcnces cued yzlgircgtasuzlgnnel phase relations of the information UNTED STATES PATENTS and wherein said synchronizing generator means 2.751.439 6/l956 Burton 340/l74.l B i l d 2.937.239 5/l960 Garber 340/l74.l B a sine wave oscillator. and &#34;imam xu M akolm F. Hubler phase shift means. said sine wave oscillator being connected to generate a reference sine wave &#39;&#39;f&#34;-&#34; &#34;Tompkmsi signal for recording onto one of the external Epstcm information channels of said tape information storage means. and said phase shift means EXEMPLARY CLAIM being operatively connected to said reference I. An electronic skew correction system. comprising signal gcncrating means for shifting the phase in Comb na ion. of said reference signal for the production of recording means and playback a i equal amplitude signals ninety degrees out of recording means having a capability of receiving phase with said referenc signal for recording a ng r a o n ii tipli ty f on another one of the external channels of said information chlannetls and saiid playbac: means information storage recording means. having an abi ity or repro ucing sai stored information. 5 Claims. 1 Drawing Figure information storage means. said information storage 0 L I -INI&#39;ORIIATION truer: A)  
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 &#39; {D I neconomo Wm sears I SHIFT N Patent No. 3,877,069  
 April 8, 1975 E. R. Altonji et a1.  
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  2 xoqmb 2952x32- MEC o 225mg. Q E Jun am B959 855%.. 86: ll 852.8 354mm INVENTORS EDMUND a. Auow i DALE HORELICK&#39; SKEW CORRECTION SYSTEM The present invention relates to a skew correction system for use in training devices and is particularly directed towards an electronic skew correction system for maintaining exact phase relation between two or more information channels.  
 between two or more channels of an information storage recording medium.  
 Another obiect of the instant invention is to provide a novel electronic system for correctingthe phase shifts between two or more channels of an information storage magnetic tape mediumfor correction of skew effects due to recording-reproducing mechanisms.  
  Still another object of the instant invention is to provide a novel electronic system for skew correction in a magnetic tape information storage recording medium which is simple in design and easy to build.  
  Yetanother object of the instant invention is to provide a novel electronic skew correction system for use in a magnetic tape information storage system which maintains phase relationships between a multiplicity of information channels recorded on magnetic tapes.  
 Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood byreference to the following detailed description when considered in connection with the single drawing which is a schematic block diagram of a preferred embodiment of theinstantinvention. i a 7 Referring now to the drawing. the. skew correction trically variabledelay line30. The reference signal on channel F. is fed into a fixed delay line 32 and from there into a phase detector comparator 34. The outputs from the electrically variable delay line are alsofed .into the phase detectorcomparator 34. The phased ifl ference betweenjthe reference signals on channels A and F which represents an error phase difference. and  
 is causedmostly bythe skew of the magnetic tape in relation to the recording and feedback heads, is detected by phase detector comparator 34, integrated by integrator 36 and applied to modulators 38 and 40 respectively..The outputs from modulators 38 and 40 respectively. are amplified by amplifiers 42 and 44 respectively. and demodulated by demodulators 46 and 48 rea spectively. The output from phase detector comparator 34 is a varying DCsignal. This is integrated by integrator 36. Oscillator means43 provides a carrier signal for modulators 38 and 40.The error output from integrator 36 is used to modulate this carrier signal by modula t tors 38 and&#39;40. The modulator signal is fed to amplifi ers 42 and 44 and dcmodulators 46 and 48 to form an error signal in error summer 50. r  
  The modulators and demodulators. in a preferred embodiment of the invention. are choppers. The sum mer 50, in a preferred embodiment of the invention. is a parallel resistance summer. The summed output from summer 50 is applied to electrically variable delay line 30&#39;and at the same time to channels. B. C. D. E and F.  
 respectively 18. 20, 22. 24and 26 in the correct magnitude. to automatically control the amount of delay applied to each ofthc channel output signals so that the output information at point 52 is maintained incorrect phascrelation for the error feedback from summer 50 through electrically variable delay line 30 to phase detector 34, integrator 36. modulators 38 and 40, amplifiers 42 and 44 and demodulators 46 and 48. The electrically variable delay line 30 and the variable delay lines.  
 system&#39;ruses delay lines. These delay lines are varied and controlled electronically. Magnetic tape [0 is driven past recording heads 12 and 14 on which is recordcd equal magnitude sine-wave signals 90&#39; out of phase .with each other. These equal magnitude sinewave signals are in addition to the information signals which are also recorded onto the magnetic tape 10. The channels containing information are shown as channels A. B. C. D. E and F on the drawing. The two outside channels on which the referenced sine-wave signals are recorded by recording heads 12 and 14 do not contain any channel information but merely contain the information for correcting the skewof the tape. The 90 sine-wave reference signal is generated by a sine-wave generator 15. The output of the sine-wave generator is fed into the 90 phase-shifter 16 which shifts the phase of the input sine&#39;wave reference signal by 90 for use on channels 12 and 14 (information channels A and FLThc channel information contained in channels B. C. D and E are fed into variable delay lines. respectively 18. 20. 22. 24 and 26. The reference sine-wave signals which are recorded on the two outside channels (A and F). are fed into the skew correctrespectivcly i8. 20. 22, 24 and 26 are standard cornmercial items and for this reason are not further described hercin.  
 The above description and the FIGURE show that with the use of simplified circuitry and a novel system the skcw from a multiple channel tape storage system can be controlled. to maintain a constant phase rela tionship between a large number of channels recorded thereon. The novel system of thisinvcntion can also be.  
 utilized in filmrccording systems or any other type of system wherein a multiplicity of parallel channels have recorded thereon information which must be kept in exact phase relationships. I  
  Obviously many modifications and variations of the present invention are possible in the light of the above teachings. it is therefore to be understood that within ing circuitry. The reference Asignal in channel A is fed a into impedance matching cathode follower 28. The  
 output from this cathode follower 28 is fed into an electhe scope of the appended claims the invention may be practiced otherwise than as specifically described.  
 What is claimed is:  
 I. An electronic skew correction system. comprising in combination; a a  
 recording means and playback means. said recording means having a capability of receiving and storing information in a multiplicity of information channels and said playback means having an ability for reproducing said stored information.  
  information storage means. said information storage meansibcing operatively connected to said recording and playback means for storage of information on a multiplicity of information channels.  
  synchronizing means. operatively connected to said synchronizing signal generating means.  
 phase shift control means. said phase shift control formation stored on said storage means whereby said phase shift control means vary the various channel phase relations of the information reproduced. a  
 and wherein said synchronizing generator means inshift control means comprises:  
 cludes.  
 a sine waveoscillator. and r phase shift means. said sine wave oscillator being connected to. generate a reference sine wave sig&#39; nal for recording onto one of the external information channels of said tape information storage means. and said phase shift means being operalively connected to said reference signal generatingmcans for shiftingthe phase of said reference signal for the production of equal amplitude sig nals ninety degrees out of phase with Said reference signal for recording on another one of the external channels of said information storage recording means. a  
 The combination of claim I wherein said phaseerror signal detection means. said error signal detection means beingoperatively connected to said playback means for detection of the phase error between said ninety degree phase-shifted reference signal and said reference signal recorded on the external channels of said information&#39;recording medium. thereby prot idingan error correction signal voltage divider. means. said voltage proportional&#39;to said phase error.  
  divider means being operatively connected to the output of said 4 r means, whereby the output signal from said error detector means controls the phase shift of said control means for control of the information channel -.phase relations. t i 3. The combination of claim 2 wherein said feedback error detecting means comprises; u a fixed delay line and an electrically variable delay line.each of said delay lines being respectively connected to the output of i said external synchronizing signal recording channels. phase detector means. said phase detector means being operatively connected to the outputs of said fixed delay line and said electrically variable delay line for detection of phase difference between said signals. integrating means. said integrating means being oper atively connected to the output of said phase detection means for integration of signals generated therein. f amplifier-modulation and demodulation means. said amplifiermodulation and demodulation means i being operatively connected tothe output of said integration means for production of an error signal representing the phase difference &#34;between said synchronizing. signals recorded on the external g channels of said informationstorage means.  
  error summing means. said error summing means being connected to the output of said amplifier modulator and demodulation means for summing A the errors detected between said externally re corded synchronizing signal channels. the output of the error summer being applied both to said electrically variable delay line&#39;and to said voltage divider means whereby the output from said voltage divider means controls said control means in accordance with the detected error correction signal. 4. The combination of claim 3 wherein said control means comprises one electrically variable delay line for error detector means for dividing said error signal 1 feedback means.  
 into amplitudes proportional to the position of the channel recorded on said information storage means.  
  said feedback means being operalively connected to the output &#39;of said error detector means for control of said error correction signal. and  
 control means.ysaid control means&#39;being operatively.  
 channel recorded upon said information storage each recorded information channel. y t  
 5. Thecombination of claim 4 wherein said amplifier-modulation and demodulation means comprise;  
 means for generating a reference carrier signal. chopper means. coupled to said means for generating i demodulating means beingoperatively connected to r to the output of said amplifier means.  
 eeu e a reference carriersignahfor modulating said inteto the output of o