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Following the 1938 invention of PAR lamps for automotive applications, and the general lighting PAR38 around 1940, it took many years before they were adopted in entertainment lighting. One of the first was the 30W #4515 PAR36 Pinspot. Then followed the 300W PAR56 and 500W PAR64 for indoor & architectural floodlighting, the 120V mains being boosted to match the 3200K of other studio lights. Still more power followed with PAR64 28-volt aircraft headlamps, in particular the 250W #4552 and 600W #4559, although their beams were too narrow and the low voltage proved inconvenient.
It was not until the later 1960s that the ruggedness and simplicity of PAR lamps and PAR can fixtures won them widespread success, fuelled by developments in rock music which drew entertainment lighting equipment out of fixed-venue theatres, to mobile rigs erected at concert sites. GE addressed the power shortcomings in 1964 with the launch of halogen versions, first the 250W PAR38, followed by the 1000W PAR64 with transverse capsule and coiled-coil filament, which became the workhorse of show lighting.
These could only be made up to 120V due to problems of fragility and arcing, and in high voltage countries this limited flexibility due to the need to use them in series pairs. The problem was overcome with the 1978 invention of this lamp by Roger Hume of Thorn Lighting, which made its debut to light the film 'Flash Gordon'. The inner capsule is mounted axially rather than transversally and employs a grid filament. This increased shock resistance up to 800G and achieves superior optical efficiency with a more rounded beam profile. The arcing problems were overcome with another of Hume's inventions, by dosing a trace of hydrogen gas into the lamp. |