Matthew
08-08-2003, 11:07 PM
TV records
PHILIPS has succeeded in creating a new system by which color programs lasting 30 to 45 minutes can be recorded on one side of a new kind of record which resembles a normal LP. The playis equipped with an optical pick-up system and can be connected directly to a TV set.
The VLP (video long-playing) record is of normal LP size and is made from a similar material. Information is stored along a spiral shaped track. It is played at 25 revolutions per second and each turn of the track contains the information for one complete image. The track consists of a "string" of microscopically small oblong pits which are equal in depth and width. Their variation in length and distance from one another contains all the information required, ie. brightness, color, synchronisation and sound.
Instead of a pick-up stylus, an extremely small spot of light is centred on the track by means of an opto-electronic control system, which obviates the use of a mechanical groove for guiding purposes. This system allows for an extremely small track pitch.
When the spot of light scans the track, the light reflected by the record is modulated in accordance with the pattern of pits. The modulated beam impinges upon a photodiode delivering an electrical signal which, after suitable amplification and processing, can be fed directly to the input of a television set.
The Philips VLP system. The diagram below shows how it works.
1. Video long-playing record. Detail (1a) shows the pattern of pits (pits appear white).
2. Spring-suspended lens with automatic focusing of the light beam.
3. Hinged mirror for following the track.
4. Beamsplitting prism.
5. Photodiode (detector).
6. light source.
To obtain a signal that is sufficiently free from noise, a light source of high intensity is required. The small, inexpensive heliurn-neon laser used for this purpose can be mass-produced by means of a new, specially developed production method.
The opto-electronic tracking mechanism makes the apparatus surprisingly flexible in use. A picture can, for instance, be "frozen" whenever required; picture sequences can be speeded up, played back in slow motion or viewed picture-by-picture. Reverse motion is also possible.
PHILIPS has succeeded in creating a new system by which color programs lasting 30 to 45 minutes can be recorded on one side of a new kind of record which resembles a normal LP. The playis equipped with an optical pick-up system and can be connected directly to a TV set.
The VLP (video long-playing) record is of normal LP size and is made from a similar material. Information is stored along a spiral shaped track. It is played at 25 revolutions per second and each turn of the track contains the information for one complete image. The track consists of a "string" of microscopically small oblong pits which are equal in depth and width. Their variation in length and distance from one another contains all the information required, ie. brightness, color, synchronisation and sound.
Instead of a pick-up stylus, an extremely small spot of light is centred on the track by means of an opto-electronic control system, which obviates the use of a mechanical groove for guiding purposes. This system allows for an extremely small track pitch.
When the spot of light scans the track, the light reflected by the record is modulated in accordance with the pattern of pits. The modulated beam impinges upon a photodiode delivering an electrical signal which, after suitable amplification and processing, can be fed directly to the input of a television set.
The Philips VLP system. The diagram below shows how it works.
1. Video long-playing record. Detail (1a) shows the pattern of pits (pits appear white).
2. Spring-suspended lens with automatic focusing of the light beam.
3. Hinged mirror for following the track.
4. Beamsplitting prism.
5. Photodiode (detector).
6. light source.
To obtain a signal that is sufficiently free from noise, a light source of high intensity is required. The small, inexpensive heliurn-neon laser used for this purpose can be mass-produced by means of a new, specially developed production method.
The opto-electronic tracking mechanism makes the apparatus surprisingly flexible in use. A picture can, for instance, be "frozen" whenever required; picture sequences can be speeded up, played back in slow motion or viewed picture-by-picture. Reverse motion is also possible.