Flying spot scanner
Encyclopedia
A flying-spot scanner uses a scanning source of a spot of light, such as a high-resolution, high-light-output, low-persistence Cathode Ray Tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

 (CRT), to scan an image, usually from motion picture film or a slide. The output of the scanner is usually a television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

 signal.

Basic principle

In the case of the CRT-based scanner, as the electron beam is drawn across the face of the CRT, it creates a scan that has the correct number of lines and aspect ratio for the format of the signal. The image of this scan is focused with a lens onto the film frame. Its light passes through the image being scanned and is converted to a proportional electrical signal by Photomultiplier
Photomultiplier
Photomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...

 tube(s), one for each color (Red, Green, Blue) that detect the variations in intensity of the beam spot as it scans across the film, and are converted to proportional electrical signals, on for each of the color channels.

Telecine
Telecine
Telecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....

s that use a monochrome CRT as the light source can be referred to as flying-spot scanners. The advantage of the FSS technique is that as colour analysis is done after scanning, simple dichroics may be used to split the light to each photomultiplier — and there are no registration errors, as would have been introduced by early electronic cameras.

Early use

Historically, flying-spot scanners were also used as primitive live-action studio cameras at the dawn of electronic television, in the 1920s.
A projector equipped with a spinning perforated disc created the spot that scanned the stage. Scanning a subject this way required a completely dark stage, and was impractical for production use, but gave early researchers a way to generate live images before practical imaging pickup tubes were perfected.

DuMont Vitascan

Flying-spot scanner technology was later implemented by DuMont Laboratories
DuMont Laboratories
DuMont Laboratories was an American television equipment manufacturer. The company was founded in 1931, by inventor Allen B. DuMont. Among the company's developments were long-lasting cathode ray tubes that would be used for television. Another product out of the lab was a DuMont invention, the...

 for their Vitascan
Vitascan
Vitascan was an early color television camera system developed by American television equipment manufacturer DuMont Laboratories. Development began in 1949 and the product was released on an experimental basis in 1956...

 color television system, released in 1956. Vitascan produced NTSC color video using a "camera" that acted in reverse by housing the flying-spot CRT which was projected through the "camera"'s lens and illuminated the subject in a special light-tight studio. The light from the CRT "camera" was then picked up by special "scoops" housing 4 photomultiplier tubes (2 for red, 1 for green, and 1 for blue), which then would provide video of the talent in the studio. Unlike earlier FSS systems that relied on the studio being entirely darkened, Vitascan used a special strobe light would illuminate the studio for the talent's convenience, and would turn on during the photomultiplier scoop's blanking interval pulses, so as not to interfere with the scanning.

See also

  • Frank Gray (researcher)
    Frank Gray (researcher)
    Frank Gray was a physicist and researcher at Bell Labs who made numerous innovations in television, both mechanical and electronic, and is remembered for the Gray code....

    , inventor of (mechanical) flying-spot scanner
  • History of television
    History of television
    The history of television records the work of numerous engineers and inventors in several countries over many decades. The fundamental principles of television were initially explored using electromechanical methods to scan, transmit and reproduce an image...

  • Electronic Video Recording
    Electronic Video Recording
    Electronic Video Recording, or EVR, was a film-based video recording format developed by Hungarian-born engineer Peter Carl Goldmark at CBS Laboratories in the 1960s....

     (CBS, 1967)
  • Vitascan
    Vitascan
    Vitascan was an early color television camera system developed by American television equipment manufacturer DuMont Laboratories. Development began in 1949 and the product was released on an experimental basis in 1956...

     (DuMont Laboratories
    DuMont Laboratories
    DuMont Laboratories was an American television equipment manufacturer. The company was founded in 1931, by inventor Allen B. DuMont. Among the company's developments were long-lasting cathode ray tubes that would be used for television. Another product out of the lab was a DuMont invention, the...

    , 1949)

External links

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