FLYING SPOT SCANNING SYSTEM

• US 3,836,706 A
• Filed: 06/18/1973
• Issued: 09/17/1974
• Est. Priority Date: 06/18/1973
• Status: Expired due to Term

• Current Assignee: Carl J. Roberts, Patrick J. Keegan
• Original Assignee: Carl J. Roberts, Patrick J. Keegan
• Inventors: Keegan, Patrick J., Roberts, Carl J.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/370,718
• Time in Patent Office: 456 Days
• Field of Search: 178/5.2R,5.2D,7.2,DIG.28
• US Class Current: 348/101
• CPC Class Codes: G11B 7/0032 for moving-picture soundtracks, i.e. cinema cameras or projectors with sound recording or reproducing means G03B31/02
• CPC Class Codes: H04N 9/11 Scanning of colour motion picture films, e.g. for telecine

Abstract

A flying spot scanning system includes a flying spot scanner arrangement utilizing a multi-facetted prism, such as an 18-sided prism, for scanning a movie film and producing color video signals therefrom for display on a conventional color television receiver. Red, blue, and green photomultiplier tubes in conjunction with a dichroic mirror arrangement provide the color signals which are gamma corrected, and phosphor corrected and processed to provide the composite color video signal. The film preferably contains a separate audio track which is separately processed and mixed with the color video signal to provide the composite video signal. The control for the flying spot scanner is provided by a digital synchronizing generator which utilizes the color burst frequency as the basic timing reference signal for generating all of the control signals for the television receiver, the scanner, and the synchronizing signals for ant external devices, such as a computer terminal and a computer, to lock these external devices to the scanning of the flying spot scanner, which digital signals are utilized to directly drive analog circuitry. Specifically, the digital synchronizing generator generates the vertical sweep drive and the horizontal sweep drive signals for the cathode ray tube flying spot scanner, the composite sync, chromo clamp, video clamp, color burst, and composite blanking signals which are provided to the flying spot scanner and subsequently to the television receiver in the composite video signal, and the horizontal sync and vertical sync signals which are utilized for external control of video so as to lock the external device to the television sweep provided from the digital synchronizing generator. The audio portion of the signal is processed through an audio FM modulator utilizing a field effect transistor to modulate an LC oscillator, the field effect transistor being utilized as a phase variance circuit. The gamma correction circuitry utilized in the system is substantially temperature independent. The phosphor correction circuitry and chroma processing circuitry utilize multi function elements to increase efficiency.

Claims

1. A flying spot scanning system capable of scanning a continuously moving film containing color information tHereon to provide a composite color video signal therefrom which is displayable on a color television means, said system comprising a cathode ray tube flying spot light source;

means for continuously moving a portion of said film past said light source for enabling said film portion to be scanned by said light source as said film portion moves past said light source;

means interposed between said moving film and said flying spot light source for providing a flying spot lap-dissolve scan of said continuously moving film portion, detection means in optical alignment with said lapdissolve scanned film portion and said lap-dissolve scan providing means for detecting said scan and providing a video signal therefrom, said detection means comprising color separation means for optically separating said detected scan into red, blue and green components and photomultiplier means for detecting each of these components to provide electrical signals representative of separate red, blue and green components of said flying spot scan;

processing means operatively connected to said photomultiplier means for processing said detected red, blue and green scan component representative signals for providing said composite color video signal therefrom, said processing means comprising color burst frequency signal, penetration means for providing a color burst component for said composite color video signal and means for providing an (R-Y) and (B-Y) color video information component for said composite color video signal from said signals representative of said detected red, blue and green components of said flying spot scan; and

digital synchronizing signal generator means operatively connected to said flying spot light source and said processing means for controlling the operation thereof, said synchronizing signal generator comprising means responsive to said color burst frequency signal for digitally providing from said color burst signal a plurality of digital synchronizing signals of differing parameters from said color burst signal, said color burst signal being a basic timing reference signal for said synchronizing signal generator, said generated plurality of digital synchronizing signals comprising synchronizing signals for controlling all of the synchronization of the cathrode ray tube flying spot light source as well as all the synchronization of the color television means, said color television means synchronizing signals being provided to said video processing means, said video processing means combining said color burst signal, said color video information component signals and said color television means synchronizing signals to comprise said composite color video signal.

2. A flying spot scanning system in accordance with claim 1 wherein said synchronizing generator comprises means for digitizing said color burst signal and a digital frequency divider chain for operating on said digitized basic timing reference color burst signal to provide a composite blanking synchronizing signal and a composite sync synchronizing signal as said color television synchronization signals.

3. A flying spot scanning system in accordance with claim 2 wherein said divider chain further operates on said digitized basic timing reference color burst signal to provide a chroma clamp and a video clamp synchronizing signal to said processor means for setting signal reference levels in said processing means for the processing of said representative signals.

4. A flying spot scanning system in accordance with claim 2 wherein said divider chain further operates on said digitized basic timing reference color burst signal to provide a vertical sweep drive and a horizontal sweep drive synchronizing signal as said cathode ray tube flying spot light source synchronization signals for vertically and horizontally synchronizing the scan of said flying spot light source.

5. A flying spot scanning system in accordance with claim 2 wherein said divider chain further operates on said digitized basic timing rEference color burst signal to provide a controlled duration for said color burst signal component of said composite color video signal.

6. A flying spot scanning system in accordance with claim 1 wherein said system further includes data terminal means for externally controlling the information to be displayed on said color television means, said data terminal means comprising a computer means and a computer interface means operatively connected between said computer means and at least said processing means for enabling interactions therebetween whereby said displayable color television information is externally controlled;

and said synchronization generator comprises means for digitizing said color burst signal and a digital frequency divider chain for operating on said digitized basic timing reference color burst signal to provide a horizontal sync synchronizing signal and a vertical sync synchronizing signal to said data terminal means for synchronizing said data terminal means with said color television means and said cathode ray tube flying spot light source means, said generated plurality of synchronizing signals further comprising said horizontal and vertical sync external control data terminal means synchronizing means for further controlling said data terminal means synchronization.

7. A flying spot scanning system in accordance with claim 1 wherein said lap-dissolve scanning means comprises a rotatable multifacted prism means, three facets of said prism covering three frames of said film being scanned in lap-dissolve light paths as said prism rotates, whereby a first facet fades into the film portion being scanned, a second facet scans said film portion, and a third facet fades out from said film portion, the light output to said photomultiplier tube means being the sum of the lap-dissolve light paths.

8. A flying spot scanning system in accordance with claim 7 wherein said lap-dissolve scanning means further comprises a primary lens interposed beween said prism and said cathode ray tube flying spot light source for forcusing said light source along an optical axis on said prism, said prism rotating about a normal to said optical axis, said prism means comprising a solid prism having a predetermined number of facets which number balances the factors of minimal distoration through said prism, light output from said prism and the size of the back focal length of said primary lens.

9. A flying spot scanning system in accordance with claim 8 wherein said prism comprises 18 facets.

10. A flying spot scanning system in accordance with claim 8 wherein said prism has a predetermined diameter D for said predetermined number of facets defined by the relationship;

average diameter D'"'"''"'"' Dmax + Dmin;

/Z corner to corner diameter for said prism Dmax (YN theta (Nd2 - sin2 theta )1/2)/ theta Nsin theta ((Nd2 - sin2 theta )1/2 - cos theta ) and center to center diameter for said prism Dmtn YNNd/( theta N(Nd-1)) where theta N theta max, theta angle formed between the prism face and said film, YN half pitch of prism half film frame height, Nd refractive index for sodium D line and Vd Abbey constant -(Nd-1)/(NF-NC) where F line blue and C line red.

11. A flying spot scanning system in accordance with claim 10 wherein said film is super 8 movie film and said prism is Schott BK7 type glass and has a refractive index of substantially 1.517 for the sodium D line with a corresponding Abbey constant of substantially 64.2, and said prism has an interior angle between adjacent facets of substantially 160* + or - 1/2 '"'"''"'"'.

12. A flying spot scanning system in accordance with claim 11 wherein said prism facets each have a length of substantially 0.246 inches, said prism diameter is substantially 1.396 inches and said prism has a width of substantially 0.5 inches.

13. A flying spot scanning system in accordance with claim 7 wherein said system further comprises idler sprocket means geared to said prism means for rotation therewith, said film means having sprocket holes therein with said sprocket means engaging said film sprocket holes for rotation with said moving film, said prism rotating with said sprocket means for synchronizing the feed of said film;

the sprocket means being driven by said film, and said prism being driven by said sprocket means.

14. A flying spot scanning system in accordance with claim 13 wherein said film moving means comprises capstan driven means.

15. A flying spot scanning system in accordance with claim 1 wherein said color separation means comprises dichroic means and each of said photomultiplier means including focusing lens means optically interposed between said photomultiplier means and said dichroic means.

16. A flying spot scanning system in accordance with claim 15 wherein said detection means further comprises collimating lens means optically interposed between said film portion being scanned and said dichroic means in optical alignment therewith.

17. A flying spot scanning system in accordance with claim 1 wherein said processing means comprises a video clamping means and phosphor correction means operatively connected between each of said photomultiplier means outputs and said video clamping means for correcting for the phosphor decay time associated with the red, green and blue phosphors, respectively, said phosphor correction means comprising a single stage transistor amplifier means capable of providing signal inversion and gain and phosphor correction for said photomultiplier means representative signals, and a low impedance drive for said video clamping means.

18. A flying spot scanning system in accordance with claim 1 wherein said processing means comprises gamma correction means operatively connected to each of said photomultiplier means outputs for gamma correcting said representative signals, said gamma correction means comprising an emitter coupled transistor differential amplifier means having an output stage having a base, an emitter and a collector, a diode-resistor ladder network means operatively connected to said output stage collector, said ladder network comprising a plurality of parallel diode-resistor branches, each of said diode branches having a different cut-in voltage, said network being substantially a square root circuit, said representative signals being provided to said output stage collector through said differential amplifier means, said representative signal being provided as a linear video signal in the form of a current waveform on said output stage emitter and substantially the square root of said linear video signal being provided on said output stage collector as a voltage waveform, each of said diodes cutting in at a different value of said collector voltage, whereby the collector associated impedance drops as more parallel diode-resistor branches are cut in providing a decreasing change in collector current for a given change in collector voltage with decreasing collector impedance.

19. A flying spot scanning system in accordance with claim 18 wherein said gamma correction means further comprises a potentiometer means connected to said output stage base for clamping the base bias to vary the operating point on the gamma correction curve.

20. A flying spot scanning system in accordance with claim 1 wherein said film includes a audio information and said system further includes separate audio processing means for separately detecting and processing said audio information, and combining means for combining said processed audio information and processed vIdeo information into said composite signal, said audio processing means comprising an audio FM modulator means, said audio modulator means comprising a field effect transistor phase shifting means and an audio subcarrier transistor oscillator means, said field effect transistor means receiving said detected audio signal, said oscillator means having a base, an emitter and a collector with the field effect transistor phase shifted output being coupled to the collector of said oscillator transistor, a tunable LC tank circuit having a center frequency of said audio subcarrier frequency being connected in parallel to said collector, the FM modulated audio output being provided from said emitter, said emitter being coupled to said collector in a feedback loop with said tank circuit, said phase shifted input to said tank circuit causing retuning of said tank circuit to provide said FM modulated audio output, said collector tracking said emitter phase shift to provide said FM modulated audio output.

21. A flying spot scanning system in accordance with claim 1 wherein said processing means comprises chroma modulator means for modulating said (R-Y) and (B-Y) signals and chroma clamping means for setting a dc reference level for said chroma modulator means.