Document Illumination in Image Scanner
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
In conventional image scanners the document is illuminated by incandescent bulbs. This disclosure replaces these bulbs by one or more low power miniature fluorescent tubes. To eliminate light output ripple or flicker, the tubes are supplied with high frequency AC. The technique has application in low-cost image scanners. In an image scanner it is necessary to illuminate the document to be scanned in uniform fashion. Traditionally, this has been done by the use of incandescent or photoflood bulbs. These bulbs are expensive, have a short life, are physically large, generate excessive heat, and it is difficult to obtain uniform illumination across the surface of the document. A recent development in fluorescent lighting technology has made low power fluorescent tubes commercially available.