- The computer scanner has been around for several decades. The technology was developed during the 1950s by the National Bureau of Standards, now called the National Institute of Standards and Technology, an agency of the United States Department of Commerce. The team that worked on the first computer scanner was led by Russell Kirsch. In 1957, Kirsch was the first person to scan a picture, a grainy, grayscale image of his son. The device developed by NBS is known today as a drum scanner.
- There are several different types of computer scanners available today. Flatbed scanners are popular and commonly purchased by home users. Sheet-fed scanners are similar to flatbed scanners but allow the user to scan multiple pages at a time. This type of scanner is for business applications. Drum scanners are generally used for commercial purposes. This type of device is more expensive but capable of producing high quality images.
- Flatbed scanners feature a glass panel where a document or other item is placed during scanning. There is a light and a scan head located below the surface of the glass. The light illuminates the document while the scan head moves across the surface. The information that is collected during the scan is transferred back to a computer in the form of a digital image. A sheet-fed scanner works in a similar way. This type of device has a stationary scan head. When documents are mechanically fed through the scanner, they pass over the scan head and the digital image is captured. Drum scanners feature a clear drum which documents are attached to. The drum rotates at high speeds in front of an optical sensor.
- When comparing the different scanners, there are a few features that you should pay attention to. The scanner's resolution will determine the quality of image that is produced. Resolution is measured in dots per inch, or dpi. It is common to see scanners with a resolution of 1200 or 2400 dpi. Color depth, measured in bits, determines the number of colors that your scanner will be able to recognize. Manufacturers commonly produce scanners with a color depth ranging from 24 to 48 bits. Speed is another major feature of any computer scanner. The speed dictates how long it will take the device to scan an image.
- It might seem like a good idea to purchase a computer scanner with the highest resolution, most color depth, and fastest speed, but that may not be true. It is important to keep in mind that there are factors that limit the effectiveness of certain scanner features. If your printer can only produce images with a resolution of 1200 dpi, there is little point in purchasing a scanner that has a 2400 dpi resolution. A 24-bit color depth on a scanner will pick up 16 million different colors, far more than the human eye can actually see, so a scanner with a color depth of 48-bits, or 281 trillion colors, may be much more than you need.
