Wednesday, June 16, 2010

Birth of digital printing

At the last EI conference John Ludd Recker gave a very successful lecture on GPU-based ripping. His paper's introduction started with a brief account of the origins of digital printing. One of the three pioneers of digital printing is Xerox Senior Research Fellow Dr. Peter Crean of the Xerox Research Center in Webster, N.Y. Dr. Crean has kindly provided the historical details before 1971, which we reproduce verbatim:

My view of digital print has a little larger view since I was involved in it before PARC even started. I fact, John Urbach, Gary's boss, asked me to join him in 1971. John and Gary came from Xerox Webster as part of the first settlers in Xerox Palo Alto.

Your paper deals with digital raster printing, specifically on Xerographic devices. I have Xerox internal reports from the 50s identifying computer/digital printing as a key application for our "new technology." We built the Henrietta facility in 1968 as the center of a "communications systems division" where many electronic printing systems using Xerography started. Our first product preceded that, the LDX was originally built as a long distance high speed fax for the Southern Railway. Its raster source was a line CRT for scanning and writing at resolutions up to about 256 dpi. It was a modified 813/660 copier with a roll feed/cutter plus the ability to slow down its 11 ppm to match the line speed. It was interfaced to several computers and sold as the Xerox Graphics Printer (XGP) to many research labs and universities. I believe Don Knuth used one in developing the TEX fonts — the only good digital font program until Adobe came out with Postscript in 1984.

801 also introduced a mobile printer (12 volts) that put a small Xerographic marker onto a typewriter carriage and was sold to police forces to put in cars and record ASCII messages. There was also a laser fax up to 2 ppm limited by line speed that was launched in 1974 or so.

Our 60 ppm duplicator (Xerox 3600) was fitted with an optical emulation of a drum line printer with 132 alphabets on a negative film "font wheel" wrapped around a drum spinning at 5000 rpm and exposed by individual flash lamps fired when the correct character was in position to project onto the drum. The printer exactly emulated a drum printer printing 132 characters by 66 lines onto an 8.5x11 page at 60 pages per minute (3960 lines per minute), ten times the mechanical printer.

Most interesting was a digital printer based on the 120 ppm duplicator still in development in 1970 when I arrived. This was to be a computer printer, writing shaped characters on a 12x2 inch high speed, high current CRT.

These were all running when I arrived in May of 1970. Pierre Lavallee and Gary Starkweather had just had the idea to put a laser scanner onto the newly developed X3600 III which had a red sensitive photoreceptor that we could easily write with a small, cheap and reliable HeNe laser. I came in from Princeton with my fresh PhD in nuclear physics and became project leader, designing the electronics and putting the system together (see photograph below). We pitched it as a graphics printer — since formed character text was already being done. For our "design guide" we used a technical report from Bell Labs who, about 6 years earlier, had built a similar system to write the 10X photo masks for integrated circuits this way. Remember Bell with local engineering firms in New Jersey was building the first IC factory, trying out a lot of things. Scanned laser system were not the winner for them, but they sure worked for us.

Peter Crean of Xerox assembling one of the first laser printers

Thank you, Peter!