A flying-spot scanner (FSS) uses a scanning source of a spot of light, such as a high-resolution, high-light-output, low-persistence

cathode ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...

(CRT), to scan an image. Usually the image to be scanned is on

photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...

, such as

motion picture film Film stock is an analog device, analog medium that is used for recording film, motion pictures or animation. It is recorded on by a movie camera, film developing, developed, film editing, edited, and projected onto a screen using a movie proj ...

, or a slide or

photographic plate Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, d ...

. The output of the scanner is usually a

television Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...

signal.

Basic principle

In the case of the CRT-based scanner, as an 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 A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sh ...

tube(s), one for each color (red, green, blue), that detects the variations in intensity of the beam spot as it scans across the film, and are converted to proportional electrical signals, one for each of the color channels.

Telecine Telecine ( or ), or TK, is the process of transferring film into video and is performed in a color suite. The term is also used to refer to the equipment used in this post-production process. Telecine enables a motion picture, captured origi ...

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 Nipkow 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 Allen B. DuMont Laboratories, Inc. (printed on products as Allen B. Du Mont Laboratories, Inc., referred to as DuMont Laboratories or DuMont Labs, and DuMont on company documents) was an American television equipment manufacturer and broadcasting ...

in the Vitascan 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.

Broadcast use

Flying-spot scanners were used to scan both still print sides and

for both broadcast TV and later

post-production Post-production, also known simply as post, is part of the process of filmmaking, video production, audio production, and photography. Post-production includes all stages of production occurring after principal photography or recording indivi ...

use. Flying-spot slide scanners were used for

Station identification Station identification (ident, network ID, channel ID or bumper (broadcasting), bumper) is the practice of radio and television stations and broadcast network, networks identifying themselves on-air, typically by means of a call sign or brand na ...

picture and to turn Test film into test TV pictures. There would be a slide changer like on

slide projector A slide projector is an optical device for projecting enlarged images of photographic slides onto a screen. Many projectors have mechanical arrangements to show a series of slides loaded into a special tray sequentially. 35 mm slide p ...

s to change the slide. Flying-spot

motion picture film scanner A motion picture film scanner is a device used in digital filmmaking to scan original film for storage as high-resolution digital intermediate files. A film scanner scans original film stock: negative or positive print or reversal/IP. Units may ...

s were used since the early days of TV. Since film cameras had better quality than early TV cameras. Early manufactures of Flying-spot scanners were Bosch Fernseh and Cintel. Cintel made Flying-spot scanners from the 1950s until the 2000s. The flying-spot scanner tube had limit life span and quantity decease with use. Most flying-spot scanners use a green light that is shone through the exposed film image into a lens. White light gives a better picture. Flying-spot scanners were replaced with

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

Line Array – CCD for imaging and a white light to the film.

Photo gallery

File:Flying spot scanner 1931.jpg, Mechanical Flying spot scanner 1931 File:Flying_spot_scanner_television_studio_1931.png, Mechanical Flying spot scanner television studio 1931 File:Early_Television_System_Diagram.png, Early Television System Diagram File:Cathode_ray_tube.png, Cathode ray Tube File:Braun_cathode_ray_tube_on_stand.jpg, Braun Cathode ray Tube from 1921 File:PhotoMultiplierTubeAndScintillator.svg, Photo Multiplier Tube And Scintillator File:Pmside.jpg, Photo Multiplier Tube File:PMT Voltage Divider.jpg, Photo Multiplier Tube

References

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External links

Science Newsletter, April 16, 1927 (reproduced at Science News Online)
"How New Television Process Works" with Gray's flying-spot scanner innovation Film and video technology Image sensors Image scanners