Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1991-02-11
1992-12-08
Razavi, Michael
Facsimile and static presentation processing
Facsimile
Recording apparatus
358215, 358216, H04N 336, H04N 5253
Patent
active
051702541
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to telecines, that is, apparatus designed to provide a video or television signal from cinematographic film.
The earliest telecines were based on the conventional cinematographic projector and had a pull-down mechanism to pull down the film by one frame whereupon the frame was scanned to produce a video signal. However, the output signal has to conform with video scanning standards and this meant that the film movement between scans should be accomplished during the video field blanking interval of typically 1.6 milliseconds. While some such fast pull-down intermittent motion telecines have been produced, in fact this short time period is not sufficient to allow the mechanism to move the film with the desired accuracy.
This problem is overcome in the continuous motion flying-spot telecine which images a cathode ray tube raster onto the film while the film moves steadily past it. Thus part of the vertical scanning action is produced by the motion of the film, and the height of the cathode ray tube raster is reduced. Typically at normal operating speed the raster height may be only about 10% of its normal stationary height. This has several deleterious effects. The image of the phosphor grain particles on the tube face is stretched in the vertical plane, and a similar effect occurs with dust particles in certain parts of the optical system, making the defects they cause more visible. The different raster heights can cause burn patches on the cathode ray tube face which require compensation if the appearance of light and dark bands across the picture is to be avoided. Indeed at certain combinations of film speed and desired scan rate the raster height becomes zero on the tube face, resulting in a worsening of these problems. Dust and phosphor particles appear as vertical lines the full picture height, severe damage is caused to the cathode ray tube phosphor and changes in the light output and colour of the cathode ray tube phosphor can result.
A further difficulty with continuous motion film scanning is the very small steadiness errors caused by scanning the film when it is in motion; these errors become very significant in video editing techniques where it is required to overlay the telecine video with video from another source. It is known that intermittent motion projectors using register pins to locate the film and hold it steady during scanning are capable of producing much improved picture steadiness. However, this is conditional on the speed being reduced so as to allow sufficient film pull-down time.
SUMMARY OF THE INVENTION
We have appreciated that a return to the intermittent motion flying spot telecine could overcome these problems, but intermittent motion telecines were quite rightly less favoured because of their more fundamental inherent problems.
This invention provides various features which can be used, preferably in combination, to enable an intermittent motion flying spot telecine to be constructed which will operate in real time without introducing the defects of the continuous motion telecine noted above, and without suffering from the basic defect of the known intermittent motion machines.
The invention provides ways of generating extra time between frames in which the film can be pulled down to the next frame. Existing commerically-available film projector systems are typified by the Nielson-Hordell 26-00 which is capable of accurate pull down and film registration within 13.9 milliseconds.
A telecine embodying the invention will be described by way of example. This telecine is an intermittent motion flying spot telecine capable of operating at conventional video rates and producing a normally scanned 625/50 or 525/60 interlaced video signal. It employs three significant features.
I. The first feature is that the film is scanned using a sequential line scan which is then converted to a standard interlaced video signal by a sequential-to-interlaced standards converter employing a digital picture store. In this way the two field blank
REFERENCES:
patent: 3814850 (1974-06-01), Matchell
patent: 3867570 (1975-02-01), Blaxtan et al.
patent: 4310856 (1982-01-01), Poetsch
patent: 4814885 (1989-03-01), Beard
patent: 4914520 (1990-04-01), Beard
Collard, Paul, "The Film/Tape Interface*", Image Technology (Journal of the BKSTS), May, 1988, No. 5, (pp. 149-154).
Greening Wendy R.
Rank Cintel Limited
Razavi Michael
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