Category Archives: L


LPI is an abbreviation for „lines per inch“.

Similar to DPI or PPI, LPI Lines per inch (LPI) is a measurement of printing resolution. A line consists of halftones built up by physical ink dots made by the printer device to create different tones. Specifically LPI is a measure of how close together the lines in a halftone grid are. The quality of printer device or screen determines how high the LPI will be. High LPI indicates greater detail and sharpness.

Conversion of the LPI to DPI can be done by simple multiplication: z.B. 150 LPI x 16 = 2400 DPI

Light spectrum

The light spectrum is the visible range of the electromagnetic spectrum that can be perceived by the eye. The spectral range visible to humans is between 380 and 780 nanometers, corresponding to a frequency range of about 4·1014 to 7.5·10 14 Hz.

Each wavelength produces a different color, for example green has a wavelength of about 540nm and blue is between 450 and 500nm. If all visible wavelengths are displayed next to each other, a rainbow-like color gradient appears. In addition, there are wavelength ranges that the human eye cannot see or perceive because there is no trigger for a pulse. These ranges are called ultra-violet (10-380nm) and infrared radiation (>780nm). The shorter a wavelength is, the more energy it has. This is also the reason why ultraviolet light is so harmful for our skin and our eyes, because in the long run it stimulates molecules to change their spatial structure and to split off single atoms.

Line sensor

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.


LEDs (light-emitting diodes) are energy-saving light sources (ESL). In contrast to conventional light bulbs, LEDs achieve 30-50 times the lighting duration, which corresponds to about 50,000 hours. Consequently, an LED can burn for up to 2083 days or more than 5.5 years. Despite their higher initial cost, they are therefore much more economical than conventional lighting.

Our boo2net devices meet the highest conservation and ecological requirements. The Fresnel lenses specially developed for the book2net lighting units are a significant technological advantage over lighting from other manufacturers. They ensure perfect light distribution and illumination. Unwanted and disruptive gradients and reflection effects, which otherwise occur in very in very bright or very dark areas and also with glossy materials, are avoided.


Library scanner

What are the requirements for a library scanner?

Besides archives and museums, libraries are among the main custodians of cultural knowledge. With regard to the stocks, there is certainly some overlap. Furthermore, state-sponsored public or academic libraries are service institutions that collect, develop, preserve and provide their users with access to a wide range of information on behalf of the public. Moreover, there are libraries that, like museums, have a certain collection focus or a special function (e.g. music libraries, monastery libraries, school libraries, etc.). Likewise, private libraries, e.g. of companies, religious communities, political parties, public or private associations, can be of high social importance.

The information collected in libraries is conveyed through the provision of media and services; traditionally in form of printed media such as books and journals, but increasingly also in digital form (e-books, DVDs or electronic journals). Since many printed media are often only available as single copies, access to these information carriers is usually very limited. The switch to electronic resources therefore serves to further disseminate and improve the accessibility of media, so that these are no longer limited to one or a few copies. In particular, retro digitization, i.e. the digitization of older collections and rare, valuable books, is becoming increasingly important. Many libraries make these digital copies available via e-readers as digital or virtual libraries.

The on-site use of media in libraries takes place in different ways. A basic distinction is made between lending libraries, in which media can also be physically borrowed, and reference libraries, in which media can only be used on site. Library scanners therefore increase user-friendliness, especially for reference libraries, since the media can also be used outside of the library’s own rooms via digitization.

As part of the cultural heritage, libraries are also highly threatened by disasters or as primary targets of armed conflict. Therefore, the digitization of important, historical and rare library holdings is also a form of active cultural property protection.

Due to these diverse fields of activity, libraries also need different types of library scanners when digitizing their holdings: from self-service scanners as a replacement for copiers to production scanners for document delivery services, to special scanners for retro-digitizing valuable manuscripts, from A3 to A0 large format scanners, from a simple 180° book support up to a conservational V-shape book cradle.

Therefore, self-service scanners such as our book2net Spirit A3 or book2net Public A2 are recommended for public areas with high public traffic, such as reading rooms. They offer quality, ease of use, robustness, durability and a protected operating system that cannot be manipulated. This makes them ideally suited for demanding continuous use and an environmentally friendly alternative to conventional copiers.

In contrast, the digitization centers of libraries need high-performance scanners such as the book2net Ultra A2 or the book2net Mosquito A1. V-scanners such as our book2net Cobra , Lizard and Dragon or special applications such as the book2net multispectral system for the scientific research of manuscripts and incunabula are particularly suitable for the conservational digitization of precious rare collections.

In addition to the special hardware requirements, library scanners also require special software that is intuitive on the one hand and can be easily operated by users in the self-service area, but on the other hand also meets the requirements for integrating third-party software, for supporting service offers (interlibrary loan, etc.), for OCR reading or for generating metadata.



Luminance is a photometric measure of the luminous intensity (brightness) per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle. The standard unit of luminance is candela per square meter (cd/m2).