Information about Nipkow Disk
A Nipkow disk (sometimes Anglicized as Nipkov disk) is a mechanical, geometrically operating image scanning device, invented by Paul Gottlieb Nipkow. This scanning disk was a fundamental component in mechanical television through the 1920s.
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.
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.
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.
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 to produce acceptable images would be to drill smaller holes (millimeter or even micrometer scale) closer to the outer sectors of the disk, but technological evolution has favoured electronic means of image acquisition.
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, accomplished by the Scottish inventor John Logie Baird, as well as the first "TV-Enthusiasts" communities and even experimental image radio broadcasts in the 1920s.
Another serious disadvantage when reproducing images with the aid of a Nipkow disk is that the images were typically very small, as small as the surface used for scanning, and which on the practical implementations of mechanical television were the size of a postage-stamp for a 30 to 50 cm diameter disk.
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.
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Physical description
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This schematic shows the circular paths traced by the holes, that may also be square for greater precision.
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.
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.
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 to produce acceptable images would be to drill smaller holes (millimeter or even micrometer scale) closer to the outer sectors of the disk, but technological evolution has favoured electronic means of image acquisition.
Usage and applications
One of the few advantages 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 at 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.).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, accomplished by the Scottish inventor John Logie Baird, as well as the first "TV-Enthusiasts" communities and even experimental image radio broadcasts in 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 were typically very small, as small as the surface used for scanning, and which on the practical implementations of mechanical television were the size of a postage-stamp for a 30 to 50 cm diameter disk.
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.External Links
- Paul Nipkow, biography includes a description and drawing of the Nipkow disc.
- The Invention of Television: Early Pioneers
- Nipkov disc, instructions on creating a cardboard Nipkov disc for experimentation.
- "Will 'camera-boxes' help catch Whitechapel Ripper?" A fictional piece about the use of Nipkow Disks in 1888 London, at Skeptic Friends Network.
Document Scanning or Image Scanning is the action or process of converting text and graphic paper documents, photographic film, photographic paper or other files to digital images.
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Paul Julius Gottlieb Nipkow (22 August 1860, Lauenburg, Pomerania - 24 August 1940, Berlin) was a German technician and inventor.
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Beginnings
While at school in Neustadt, East Pomerania, Nipkow experimented in telephony and the transmission of moving pictures...... Click the link for more information.
Mechanical television was a television system that used mechanical or electromechanical devices to capture and display images. However, the images themselves were usually transmitted electronically and via radio waves.
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A disk or disc generally refers to a round flat object, although the usage varies between different variants of English (see spelling of disc for the origin of the two spellings and regional differences[1]).
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diameter (Greek words diairo = divide and metro = measure) of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle.
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spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.
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Spiral or helix
A "spiral" and a "helix" are two terms that are easily confused, but represent different objects...... Click the link for more information.
gramophone record (also phonograph record, or simply record) is an analogue sound storage medium consisting of a flat disc with an inscribed modulated spiral groove starting near the periphery and ending near the center of the disc.
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diameter (Greek words diairo = divide and metro = measure) of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle.
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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. Its area can be calculated as described below.
Let θ be the central angle, in radians, and the radius.
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Let θ be the central angle, in radians, and the radius.
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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.
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Cinematography (from Greek: kinesis (movement) and grapho (to record)), is the discipline of making lighting and camera choices when recording photographic images for the cinema.
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cite any references or sources. Please help improve this article by citing reliable sources.
* It is in need of attention from an expert on the subject. may be able to help recruit one.
* It needs to be expanded.
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* It is in need of attention from an expert on the subject. may be able to help recruit one.
* It needs to be expanded.
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Document Scanning or Image Scanning is the action or process of converting text and graphic paper documents, photographic film, photographic paper or other files to digital images.
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scan line is one line, or row, in a raster scanning pattern, such as a video line on a cathode ray tube (CRT) display of a television or computer. A scan line represents a row of picture elements (pixels) in the image being displayed.
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In mathematics, the concept of a curve tries to capture the intuitive idea of a geometrical one-dimensional and continuous object. A simple example is the circle.
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In mathematics, curvature is any of a number of loosely related concepts in different areas of geometry. Intuitively, curvature is the amount by which a geometric object deviates from being flat, but this is defined in different ways depending on the context.
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The angular 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 Also see: Angular momentum.
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1 millimetre =
SI units
010−3 m 0 cm
US customary / Imperial units
010−3 ft 010−3 in
The millimetre (American spelling: millimeter, symbol mmSI units
010−3 m 0 cm
US customary / Imperial units
010−3 ft 010−3 in
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1 micrometre =
SI units
010−6 m 010−3 mm
US customary / Imperial units
010−6 ft 010−6 in
A micrometre (American spelling: micrometer; symbol µmSI units
010−6 m 010−3 mm
US customary / Imperial units
010−6 ft 010−6 in
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Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. All applications of electronics involve the transmission of power and possibly information.
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sensor is a type of transducer. Direct-indicating sensors, for example, a mercury thermometer, are human-readable. Other sensors, such as a thermocouple, only produce an output voltage or other electrical output which must be interpreted by another device (such as a computer).
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Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:
Most optical detectors are quantum devices in which an individual photon produces a discrete effect.
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Most optical detectors are quantum devices in which an individual photon produces a discrete effect.
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photodiode is a semiconductor diode that functions as a photodetector. Photodiodes are packaged with either a window or optical fibre connection, in order to let in the light to the sensitive part of the device. They may also be used without a window to detect vacuum UV or X-rays.
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pixel (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample.
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Timing is the spacing of events in time. Some typical uses are:
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- The act of measuring the elapsed time of something or someone, often at athletic events such as swimming or running, where participants are timed with a device such as a stopwatch.
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Angular resolution describes the resolving power of any image forming device such as an optical or radio telescope, a microscope, a camera, or an eye.
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Definition of terms
Resolving power..... Click the link for more information.
Mechanical television was a television system that used mechanical or electromechanical devices to capture and display images. However, the images themselves were usually transmitted electronically and via radio waves.
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Radiovision has several meanings in references to articles:
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- 1. An early name used by Charles Francis Jenkins for technology now known as television.
- 2. The name of a BBC radio educational program for schools that was distributed with slides and films. http://newswww.bbc.
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John Logie Baird (August 13 1888 – June 14 1946) was a Scottish engineer and inventor of the world's first working television system. Although Baird's electromechanical system was eventually displaced by purely electronic systems (such as those of Vladimir Zworykin and Philo
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Centuries: 19th century - 20th century - 21st century
1890s 1900s 1910s - 1920s - 1930s 1940s 1950s
1920 1921 1922 1923 1924
1925 1926 1927 1928 1929
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1890s 1900s 1910s - 1920s - 1930s 1940s 1950s
1920 1921 1922 1923 1924
1925 1926 1927 1928 1929
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