Category Archives: Glossary

Line sensors are light or radiation sensitive detectors (mostly semiconductor detectors), which consists of one or sometimes several rows of pixels (lines) to capture information. The counterpart to the line sensor is the area sensor, which has a rectangular arrangement (matrix) of pixels.

Line sensors are based on the original development for data storage from 1969 and have not changed significantly to this day. The light-sensitive sensors are very suitable for scanning documents in order to capture an image. The detector runs close to the original, scans the document line by line and combines the information from the individual scan lines to form an overall image. Sometimes only one line is used; sometimes a separate line is used for each color channel (red, green, blue).
This technology is still employed today in scanners, fax machines and copiers because it is very cheap and available in large quantities.

A major disadvantage of using this type of sensor in scanners is that the image capturing takes a comparatively long time due to the sequential scanning and that mechanical wear always takes place due to the movement of the components. This can lead to premature wear, especially with production scanners that have to digitize large quantities of documents in continuous operation.

In addition, the depth of field of line sensors is very small and covers only a few millimeters. Particularly in the case of books with a deep book fold or wavy pages that are not completely flat, this leads to blurring or even loss of information in the digitized material.

At book2net, we therefore only use image area sensors in our scanning systems.

Every camera needs a lens to project the object or the image to be captured onto the sensor. Lenses come in a variety of designs for a wide range of applications: Macro, back-magnification, telephoto, wide-angle, zoom or tilt-shift lens. Basically, lenses can be adjusted in two ways: focal length and aperture. The focal length determines how close or how far away objects must be to be in focus. This is also referred to as focusing. The aperture controls how much light falls through the optics onto the sensor. If the aperture is wide open, a lot of light falls on the sensor and the depth of field is basically shallow. If you close the aperture, the image becomes darker, but the depth of field increases.

In our systems we use a special lens, which was designed for the digitization of documents and books. Here we pay a lot of attention to a distortion-free image in order to avoid deformations of the documents. This ensures that the documents are also scanned and displayed at right angles and true to scale. In addition, the lens we use differs from other commercially available lenses in that it is apochromatic corrected and has extremely high sharpness even in the peripheral areas. This is because unlike in photography, when digitizing, the important image information is not only in the center of the image, but also, or especially, in the peripheral areas.