History of the scanner

Modern scanners may be considered the successors of early telephotography and fax input devices, consisting of a rotating drum with a single photodetector at a standard speed of 60 or 120 rpm (later models up to 240 rpm). They send a linear analog AM signal through standard telephone voice lines to receptors, which synchronously print the proportional intensity on special paper. This system was in use in press from the 1920s to the mid-1990s. Color photos were sent as three separated RGB filtered images consecutively, but only for special events due to transmission costs.

Édouard Belin is the inventor in 1907 of a phototelegraphic apparatus called the Bélinographe, a system able to send remote photographs, via telephone and telegraphic networks. Since 1914, a photograph of report is transmitted by telephotograph.

Its process was improved in 1921, so that it was able to transmit the images by radio waves.
In this apparatus, the transmitter traverses the original image point by point, and measures the light intensity via an electric eye. The intensity is conveyed to the receiver. There, a source of light reproduces the intensities measured by the electric eye, while carrying out same displacements exactly. By doing this, it impresses photographic paper, which makes it possible to obtain a copy of the original image.

The modern telecopiers and photocopiers use the same principle, with this close the sensor of light intensity was replaced by a sensor CCC, and that the device of impression is based on the laser technology, and either photographic.

The first image scanner developed for use with a computer, was a drum scanner. It was built in 1957 at the US National Bureau of Standards by a team led by Russell A. Kirsch. The first image ever scanned on this machine was a 5 cm square photograph of Kirsch's then-three-month-old son, Walden. The black and white image had a resolution of 176 pixels on a side.

Drum scanners capture image information with photomultiplier tubes (PMT), rather than the charge-coupled device (CCD) arrays found in flatbed scanners and inexpensive film scanners.

The drum scanner gets its name from the clear acrylic cylinder, the drum, on which the original artwork is mounted for scanning. Depending on size, it is possible to mount originals up to 11"x17", but maximum size varies by manufacturer. One of the unique features of drum scanners is the ability to control sample area and aperture size independently. The sample size is the area that the scanner encoder reads to create an individual pixel. The aperture is the actual opening that allows light into the optical bench of the scanner. The ability to control aperture and sample size separately is particularly useful for smoothing film grain when scanning black-and white and color negative originals.

While drum scanners are capable of scanning both reflective and transmissive artwork, a good-quality flatbed scanner can produce good scans from reflective artwork. As a result, drum scanners are rarely used to scan prints now that high-quality, inexpensive flatbed scanners are readily available. Film, however, is where drum scanners continue to be the tool of choice for high-end applications. Because film can be wet-mounted to the scanner drum and because of the exceptional sensitivity of the PMTs, drum scanners are capable of capturing very subtle details in film originals.

Only a few companies continue to manufacture drum scanners. While prices of both new and used units have come down over the last decade, they still require a considerable monetary investment when compared to CCD flatbed and film scanners. However, drum scanners remain in demand due to their capacity to produce scans that are superior in resolution, color gradation, and value structure. Also, because drum scanners are capable of resolutions up to 12,000 PPI, their use is generally recommended when a scanned image is going to be enlarged.


The first scanned imageIn most graphic-arts operations, very-high-quality flatbed scanners have replaced drum scanners, being both less expensive and faster. However, drum scanners continue to be used in high-end applications, such as museum-quality archiving of photographs and print production of high-quality books and magazine advertisements. In addition, due to the greater availability of pre-owned units, many fine-art photographers are acquiring drum scanners, which has created a new niche market for the machines.


***inserts from wikipedia.com