History of the Image Scanner

The perishable nature of paper made it difficult to preserve documents and hence, image scanners can be included in some of the path-breaking inventions of the 20th century. The history of image scanners that we use today, can be traced back to the period when telephotography was used to transfer images from one place to other. Telephone lines were used as a medium in telephotography.

Scanning
The scanning process can be described as the procedure of converting hard copies, such as paper document and films, into a digital form that than can be preserved for a long time as well as transferred over long distances.

History of the Image Scanner
The devices that operated on telephotography technique, had components such as rotating drums. These drums had a photo detector attached to them. The drums rotated at 60 or 120 rotations per minute (rpm) speed. The models that were used later had the drums with 240 rpm speed.

The functioning of these models can be described as follows. The analog AM signals sent through the telephone lines were detected by receptors. These receptors, then printed the image on a specially prepared paper in accordance with the signals received. This technique of imaging was used by the newspapers for a period of around 70 years between the 1920s and 1990s. Color images were sent using the 'RGB filter' technique. However, use of this technique was a costly affair thus, the newspapers rarely sent color images.

The first image scanner was manufactured under the leadership of Russel Kirsch. This drum scanner was built at the National Bureau of Standards in United States. The scanner was developed in the year 1957, and the first image to be scanned was that of Russel Kirsch's son, Walden. The image was 176 pixels, in terms of resolution, and had a size of 5 square cm. It was a defining moment in the history of the development of image scanners.

Different Types of Scanners

• Drum Scanner: The drum scanners make use of the Photomultiplier Tubes (PMT), to capture the images. The photomultiplier tube or photo tube is a kind of vacuum tube. It can be a gas-filled tube. These tubes are sensitive to different lights including the visible light, near-infrared or the ultraviolet light. The drum or acrylic cylinder of the scanner use the PMTs for scanning images.
• Flatbed Scanner: The flatbed scanner uses CCD (Charged Coupled Device) or CIS (Contact Image Sensor) for scanning. The scanner assembly that uses CCD generally has sensors arranged in three rows. These sensors have different filters such as the green, blue and red ones. The scanner has a glass pane and under this pane is a bright light. During the scanning process the pane gets illuminated by the light. The images are placed on the glass pane in a face-down manner. An opaque layer or cover is placed over the image in order to shut out the ambient light.
• Hand Scanner: The hand-held scanner is available in two different forms such as 3D scanner and document scanner. These scanners are moved over the images to be scanned. However, there is a risk of generation of a distorted image by a hand-held scanner. To avoid this, the hand should be steadily dragged over the image.
• Film Scanner: A special equipment is used to scan films. Film strips are moved across a lens by using a 'stepper motor'. The CCD sensors placed inside the scanner, further scan these films.

Scanners are useful in our day-to-day lives. One can transfer images across long distances by scanning and emailing them. The image scanners were considered to be useful gadgets before the development of digital cameras.