drum scanner (redirected from image scanner)

A type of scanner used to capture the highest resolution from an image. Photographs and transparencies are taped, clamped or fitted into a clear cylinder (drum) that is spun at speeds exceeding 1,000 RPM during the scanning operation. A light source that focuses on one pixel is beamed onto the drum and moves down the drum a line at a time.

For transparencies, light is directed from the center of the cylinder. For opaque items, a reflective light source is used. Mirrors filter out the RGB values and send them to the drum scanner's photomultiplier tube (PMT), which is more sensitive than the CCDs used in flatbed and sheet-fed scanners and can produce resolutions exceeding 10,000 dpi. If one PMT is used, three passes across the image are required. When three PMTs are used, a faster single-pass scan is performed. Contrast with flatbed scanner, sheet-fed scanner and handheld scanner.

Drum Scanner

ICG's model 370 provides 12,000 dpi of optical resolution for service bureau quality scanning. Drum scanners provide the ultimate in scanning quality and resolution and are widely used for commercial graphics production as well as applications that turn photos into posters and wall-sized images. (Image courtesy of ICG North America.)

Mounting Slides and Transparencies

Transparencies can be taped or clipped onto the drum. This QuickMount system from ICG uses cassettes built especially for easy insertion of 35mm slides, 2 1/4" and 4x5" transparencies. (Image courtesy of ICG North America.)