A Nipkow disk is a mechanical, geometrically operating image scanning device (by itself, it performs neither image acquisition or reproduction), invented by Paul Gottlieb Nipkow, which was primarily used as a fundamental component in mechanical television. Image scanning is the action or process of producing images from text documents, photographic film, photographic paper or other physical objects. ... // Engineering In engineering, the term acquisition has the following meanings: In satellite communications, the process of locking tracking equipment on a signal from a communications satellite. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ... Paul Julius Gottlieb Nipkow, born 22nd August 1860 in Lauenburg in Pomerania, died 24th August 1940 in Berlin), was a German technician and inventor. ... This schematic shows the circular paths traced by the holes in a Nipkow disk. ...

Physical description

This schematic shows the circular paths traced by the holes, that may also be square for greater precision.

The device itself is nothing more than a mechanically spinning disk of any suitable material (metal, plastic, cardboard, etc.), with a series of equally distanced circular holes of equal diameter drilled in it. Description Schematic drawing of a Nipkow disk Source: de:Bild:Nipkow-scheibe. ... Description Schematic drawing of a Nipkow disk Source: de:Bild:Nipkow-scheibe. ... A disk or disc (see below) is anything that resembles a flattened cylinder in shape. ... Diameter is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ...

These holes are positioned to form a single-turn spiral starting from an external radial point of the disk and proceeding to the center of the disk, much like a gramophone record. The holes, when the disk rotates, trace circular ring surfaces, with inner and outer diameter depending on each hole's position on the disk and thickness equal to each hole's diameter. These surfaces may or may not partly overlap, depending on the exact construction of the disk. In mathematics, a spiral is a curve which turns around some central point or axis, getting progressively closer to or farther from it, depending on which way you follow the curve. ... 33â…“ LP vinyl record album from the 1960s A gramophone record (also phonograph record, or simply record) is an analogue sound recording medium consisting of a flat disc with an inscribed modulated spiral groove. ... Diameter is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ...

How it works

A lens projects an image of the scene in front of it directly onto the disk [1]. Each hole in the spiral takes a horizontal "slice" through the image which is picked up as a pattern of light and dark by a sensor. If a light powered by a signal from the sensor is placed behind a second Nipkow disk rotating in synch at the same speed and direction, the image can be reproduced line-by-line, however it remains no larger than the one projected onto the original receiving disk.

When spinning the disk while observing an object "through" the disk, preferably through a relatively small circular sector of the disk (the viewport), for example, an angular quarter or eighth of the disk, the object seems "scanned" line by line, first by length or height or even diagonally, depending on the exact sector chosen for observation. By spinning the disk rapidly enough, the object seems complete, in a way similar to cinematography, and capturing of motion becomes possible. A circular sector or circle sector also known as a pie piece is the portion of a circle enclosed by two radii and an arc. ... An example of a graphical user interface in Windows XP, with the My Music window displayed A window is a visual area, usually rectangular in shape, containing some kind of user interface, displaying the output of and allowing input for one of a number of simultaneously running computer processes. ... Cinematography is the discipline of making lighting and camera choices when recording photographic images for the cinema. ... Motion involves change in position, such as this perspective of rapidly leaving Yongsan Station In physics, motion means a change in the position of a body relative to a reference point, as measured by a particular observer in a particular frame of reference. ...

This can be intuitively understood by covering all of the disk but a small rectangular area with black cardboard (which stays fixed), spinning the disk and observing an object through the small area.

Here arises one of the drawbacks of the Nipkow disk as an image scanning device: the scanlines are not straight lines, but rather curves. So the ideal Nipkow disk should have either a very large diameter, which means smaller curvature, or a very narrow angular opening of its viewport. Another way would be that of drilling smaller holes (millimeter or even micrometer scale) closer to the outer sectors of the disk, but technological evolution favoured electronic means of image acquisition. Image scanning is the action or process of producing images from text documents, photographic film, photographic paper or other physical objects. ... A scanline is a line on a CRT tube, made up of dots. ... In mathematics, the concept of a curve tries to capture our intuitive idea of a geometrical one-dimensional and continuous object. ... Curvature refers to a number of loosely related concepts in different areas of geometry. ... This is a large bone in the lower jaw of amphibians, birds and reptiles, which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the articular. ... A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ... A micrometre (American spelling: micrometer), symbol µm, is an SI unit of length. ... The field of electronics is the study and use of systems that operate by controlling the flow of electrons (or other charge carriers) in devices such as thermionic valves and semiconductors. ...

Usage and applications

One of the few, if not the only advantage of using a Nipkow disk is that the image sensor (that is, the device converting light to electric signals) can be as simple as a single photocell or photodiode, since each instant only a very small area (a pixel) is visible through the disk (and viewport), and so decomposing an image into lines is done almost by itself with little need for scanline timing, and very high scanline resolution. A simple acquisition device can be built by using an electrical motor driving a Nipkow disk, a small box containing a single light-sensitive (electric) element and a conventional image focusing device (lens, dark box, etc.). To meet Wikipedias quality standards, this article or section may require cleanup. ... A photoresistor is an electronic component whose resistance decreases with increasing incident light intensity. ... A photodiode A photodyke is a semiconductor diode that functions as a photodetector. ... This example shows an image with a portion greatly enlarged. ... Timing refers to how events are spaced in time. ... The word resolution has several meanings, depending on context. ...

Another advantage is that the receiving device is very similar to the acquisition device, except that the light-sensitive device is replaced by a variable light source, driven by the signal provided by the acquisition device. Some means of synchronizing the disks on the two devices must also be devised (several options are possible, ranging from manual to electronic control signals).

These facts helped immensely in building the first mechanical television, the Radiovision by means of the Scottish inventor John Logie Baird, as well as the first "TV-Enthusiasts" communities and even experimental image radio broadcasts, back in the 1920s. This schematic shows the circular paths traced by the holes in a Nipkow disk. ... Radiovision was an early name for the technology now known as television. ... Bust of John Logie Baird in Helensburgh. ... It has been suggested that this article or section be merged with Social issues of the 1920s. ...

Disadvantages

Unlike the line resolution provided by a Nipkow disk, which is potentially very high, the maximum number of scanlines is much more limited, and precisely, it's equal to the number of holes on the disk, which in practice was comprised between 30 and 100, with rare 200-hole disks tested.

Another serious disadvantage when reproducing images with the aid of a Nipkow disk, is that the images are typically very small, as small as the surface used for scanning, and which on the practical implementations of mechanical television was the size of a postage-stamp, for a 30 to 50 cm diameter disk. This schematic shows the circular paths traced by the holes in a Nipkow disk. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ...

Further disadvantages include the previously illustrated non-linear geometry of the scanned images, and the sheer size of practical implementations of the disk, at least in the past.

In fact, the Nipkow disks used in early TV were roughly 30 cm to 50 cm in diameter, with 30 to 50 "holes". The devices using them were also noisy, heavy and picture quality was very low, with a lot of flickering. Things weren't better regarding the acquisition part of the system, which required very powerful lighting of the subject.

Applications

Apart from the aforementioned mechanical television, which never took off for the practical reasons mentioned above, a Nipkow disk is used in one type of confocal microscope, a powerful optical microscope. It is also sometimes used in the field of high speed photography, although in miniaturised and very high speed versions. Confocal laser scanning microscopy (CLSM or LSCM) is a valuable tool for obtaining high resolution images and 3-D reconstructions. ... A microscope (Greek: micron = small and scopos = aim) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... High Speed Photography is the science of taking pictures of very fast phenomena. ...