Light shed on laser printing

QUESTION Why are laser printers sonamed, when they contain no laser?

THE original copier used electrophotography, discovered by Hungarian physicist Pal Selenyi but improved on and patented by American inventor and patent lawyer, Chester Carlson, in 1938.

They found a way of transmitting and printing facsimiles of printed images by directing a beam of ions onto a rotating drum of insulating material. The ions create an electrostatic charge, a fine powder is then dusted on the drum which sticks to the charged parts.

Gary Starkweather of Xerox created an actual laser printer in 1969. Instead of using a photographic process, he used light. Eight years later, Xerox released its 9700 Electronic Printing System. The first mass-market laser, the original HP LaserJet came in 1985.

A true laser printer does use a laser, a powerful beam of focused monochromatic light.

Laser printing has seven steps. A Raster Image Processor scans the page and creates a bitmap, which is stored in the raster memory. The drum is charged negatively and the bitmap is written on the photosensitive drum by a laser.

The toner particles, which include plastic powder, are attracted to the parts the laser beam hits. The powder is then fused at 200c to bond the ink to the paper.

Simon Crowe, Coventry.

QUESTION Is it true that Mark Chapman shot John Lennon with a Smith & Wesson 38 Special that holds five rounds, yet Lennon’s body had more than seven bullet holes?

FURTHER to the earlier answer, John Lennon was killed with a Charter Arms .38 Special snubnose, five-shot revolver, not a Smith & Wesson.

There is unconvincing evidence that a fifth shot was fired which missed. The autopsy makes it clear that he was hit four times.

David Gilby, Shaftesbury, Dorset.