In the previous newsletter we examined the Telecine machine with particular reference to the Photo Conductive Film (PCF) chain type device, how it developed and its application in our high technology industry. In this second part, we examine the Flying spot telecine, and also take a look at the CCD telecine.  In Focus will attempt to keep these techno talk articles simple and concise, so apologies in advance to our more technical readers who may be expecting a bit more depth -  the purpose of these articles is to introduce newcomers to the industry to technical topics.

The Flying spot scanner                             

In the United Kingdom, Rank Precision Industries was experimenting with the flying-spot scanner (FSS), which inverted the cathode ray tube (CRT) concept of scanning using a television screen. The CRT emits a pixel-sized electron beam which is converted to a photon beam through the phosphors coating the envelope. This dot of light is then focused by a lens onto the film's emulsion, and finally collected by a pickup device. In 1950, the first Rank flying spot monochrome telecine was installed at the BBC's Lime Grove Studios. The advantage of the FSS is that colour analysis is done after scanning, so there can be no registration errors as can be produced by vidicon tubes where scanning is done after colour separation, as in the PCF type telecine. It also allows simpler dichroics to be used.

The parts of a flying spot scanner: (A) Cathode-ray tube (CRT); (B) photon beam; (C) & (D) dichroic mirrors; (E), (F) & (G) red-, green- and blue-sensitive photomultipliers.

15-February-big-diagramIn a flying spot scanner (FSS), a pixel-sized light beam is projected through exposed and developed motion picture film (either negative or positive) at a phosphor-coated envelope. This beam of light  'scans' across the film image from left to right to record the vertical frame information. Horizontal scanning of the frame was then accomplished by moving the film past the CRT beam. This beam passes through the film image, projecting it pixel-by-pixel onto the pickup (phosphor-coated envelope). The light from the CRT passes through the film and is separated by dichroic mirrors and filters into red, green and blue bands. Photomultiplier tubes or avalanche photodiodes convert the light into separate red, green and blue electrical signals for further electronic processing. This can be accomplished in 'real time', 24 frames a second (or in some cases faster). Rank Precision-Cintel introduced the 'Mark' series of FSS telecines. During this time advances were also made in CRTs, with increased light output producing a better signal-to-noise ratio and so allowing negative film to be used.

The problem with flying-spot scanners was the difference in frequencies between television field rates and film frame rates. This was solved first by the Mk. I Polygonal Prism system, which was optically sychronised to the television frame rate by the rotating prism and could be run at any frame rate. This was replaced by the Mk. II Twin Lens, and then around 1975, by the Mk. III 'jump scan'. The Mk. III series progressed from the original 'jump scan' interlace scan to the Mk. IIIB which used a progressive scan and included a digital scan converter (Digiscan) to output interlaced video. The Mk. IIIC was the most popular of the series and used a next generation Digiscan plus other improvements.

The "Mark" series was then replaced by the Ursa (1989), the first in their line of telecines capable of producing digital data in 4:2:2 color space. The Ursa Gold (1993) stepped this up to 4:4:4 and then the Ursa Diamond (1997), which incorporated many third-party improvements on the Ursa system.

Line Array CCD

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The parts of a CCD scanner: (A) Xenon bulb; (B) film plane; (C) & (D) prisms and/or dichroic mirrors; (E) ,(F) & (G) red, green and blue-sensitive CCDs.

The Robert Bosch GmbH, Fernseh Div., which later became BTS inc. - Philips Digital Video Systems and is now part of Thomson's Grass Valley, introduced the world's first CCD telecine (1979), the FDL-60. The FDL-60, designed and made in Darmstadt West Germany, was the first all solid state Telecine.

Rank Cintel (ADS telecine 1982) and Marconi Company (1985) both made CCD Telecines for a short time. The Marconi B3410 sold 84 units over a three year period, and a former Marconi technician still maintains them.

In a charge-coupled device Line Array CCD telecine, a 'white' light is shone through the exposed film image into a prism, which separates out the image into the three primary colors, red, green and blue. Each beam of colored light is then projected at a different CCD, one for each color. The CCD converts the light into electrical impulses which the telecine electronics modulate into a video signal which can then be recorded onto video tape or broadcast.

Philips-BTS eventually evolved the FDL 60 into the FDL 90 (1989)/ Quadra (1993). In 1996 Philips, working with Kodak, introduced the Spirit DataCine (SDC 2000), which was capable of scanning the film image at HDTV resolutions and approaching 2K (1920 Luminance and 960 Chrominace RGB) x 1556 RGB. With the data option the Spirit DataCine can be used as a motion picture film scanner outputting 2K DPX data files as 2048 x 1556 RGB. In 2000 Philips introduced the Shadow Telecine (STE), a low cost version of the Spirit with no Kodak parts. The Spirit DataCine, Cintel's C-Reality and ITK's Millennium opened the door to the technology of digital intermediates, wherein telecine tools were not just used for video outputs, but could now be used for high-resolution data that would later be recorded back out to film. The Grass Valley Spirit 4k\2k\HD (2004) replaced the Spirit 1 Datacine and uses both 2K and 4k line array CCDs. (Note: the SDC-2000 did not use a color prisms and/or dichroic mirrors.)

Well, you may feel that this takes us up to date, however there is more. In the next article, we will discuss Pulsed LED/Triggered three CCD Camera systems and also touch on the Digital Intermediate. This is heavy stuff but well worth knowing, so don't forget to read the final article in this series in the next edition.