Zworykin's patent diagram of a UV-microscope 1931.^[1] The apparatus is similar to the iconoscope. The image entered through the series of lenses at upper right, and hit the photoelectric cells on the image plate at left. The cathode ray at the right swept the image plate, charging it, and the photoelectric cells emitted an electric charge in variance with the amount of light hitting them. The resulting image signal was carried out the left side of the tube and amplified.

The Iconoscope (from the Greek: εἰκών "image" and σκοπεῖν "to look, to see") was the name given to an early television camera tube in which a beam of high-velocity electrons scans a mosaic of photoemissive isolated granules. Some of the principles of this apparatus were described when Vladimir Zworykin filed two patents for a Television system in 1923 and 1925.^[2][3]

A research group at RCA headed by Vladimir Zworykin presented the iconoscope to the general public in a press conference in June 1933,^[4] and two detailed technical papers were published in September and October of the same year.^[5][6] The German company Telefunken bought the rights from RCA and built the Iconoscope camera^[7] used for the historical TV transmission at the Olympic Games in Berlin 1936.

The Iconoscope was the leading camera tube used for broadcasting in the United States from 1936 until 1946, when it was replaced by the image orthicon tube.^[8][9]

Operation[link]

Within the iconoscope, an image was projected onto a plate containing a mosaic of electrically isolated photosensitive granules separated from a common plate by a thin layer of isolating material, each granule constituting a tiny capacitor with the common plate that accumulated and stored electrical charge in response to the light striking it. Emission of photoelectrons from each granule in proportion to the amount of light received resulted in a charge image being formed on the mosaic. An electron beam was then swept across the image plate from an electron gun, effectively scanning the stored image and discharging each capacitor in turn such that the electrical output from each capacitor was proportional to the average intensity of the light striking it between each discharge event.^[1][3][10] The accumulation and storage of photoelectric charges during each scanning cycle greatly increased the electrical output of the iconoscope relative to non-storage type image scanning devices.^{[citation needed]} In the 1931 version, the electron beam scanned the granules;^[1] while in the 1925 version, the electron beam scanned the back of the image plate.^[3]

History[link]

In July 1925, Zworykin submitted a patent application for a "Television System" that includes a charge storage plate constructed of a thin layer of isolating material (aluminum oxide) sandwiched between a screen (300 mesh) and a colloidal deposit of photoelectric material (potassium hydride) consisting of isolated globules.^[3] The following description can be read between lines 1 and 9 in page 2: The photoelectric material, such as potassium hydride, is evaporated on the aluminum oxide, or other insulating medium, and treated so as to form a colloidal deposit of potassium hydride consisting of minute globules. Each globule is very active photoelectrically and constitutes, to all intents and purposes, a minute individual photoelectric cell.^[3] Its first image was transmitted in late summer of 1925,^[11] and a patent was issued in 1928.^[3] However the quality of the transmitted image failed to impress to H P Davis, the general manager of Westinghouse, and Zworykin was asked to work on something useful.^[11]

Iconoscope and mosaic from a TV camera, circa 1955.

A patent for a television system was also filed by Zworykin in 1923, but this file is not a reliable bibliographic source because extensive revisions were done before a patent was issued fifteen years later^[12] and the file itself was divided into two patents in 1931.^[2][13] In 1926, the Hungarian engineer Kálmán Tihanyi explained in detail that the principle of "storing" electrical charges in proportion to the amount of light received throughout each scanning cycle results in a much more sensitive video camera tube.^[14][15][16] Although his 1926 application was never acted upon,^[17] two year later, in 1928, Tihanyi applied for a patent for a refined "Television Apparatus" that is essentially an iconoscope.^[10]

The first practical iconoscope was constructed in 1931 by Sanford Essig, when he accidentally left one silvered mica sheet in the oven too long. Upon examination with a microscope, he noticed that the silver layer had broken up into a myriad of tiny isolated silver globules.^[18] He also noticed that: the tiny dimension of the silver droplets would enhance the image resolution of the iconoscope by a quantum leap.^[19] As head of television development at Radio Corporation of America (RCA), Zworykin submitted a patent application in November 1931, and it was issued in 1935.^[1] Nevertheless, Zworykin's team was not the only engineering group working on devices that use a charge stage plate. In 1932, Tedham and McGee under the supervision of Isaac Shoenberg applied for a patent for a new device they dubbed "the emitron", a 405-line broadcasting service employing the emitron began at studios in Alexandra Palace in 1936, and a patent was issued in the USA in 1937.^[20] One year latter, in 1933, Philo Farnsworth also applied for a patent for a device that use a charge storage plate and a low-velocity electron scanning beam, a patent was issued in 1937,^[21] but Farnsworth did not know that the low-velocity scanning beam must land perpendicular to the target and he never actually built such a tube.^[22][23]

The iconoscope was presented to the general public in a press conference in June 1933,^[4] and two detailed technical papers were published in September and October of the same year.^[5][6] Unlike the Farnsworth image dissector, the Zworykin iconoscope was much more sensitive, useful with an illumination on the target between 4ft-c (43lx) and 20ft-c (215lx). It was also easier to manufacture and produced a very clear image.^{[citation needed]} The iconoscope was the primary camera tube used in American broadcasting from 1936 until 1946, when it was replaced by the image orthicon tube.^[8][9]

On the other side of the atlantic ocean, the British team formed by engineers Lubszynski, Rodda, and MacGee developed the super-emitron (or super-iconoscope) in 1934,^[24][25][26] this new device is between ten and fifteen times more sensitive than the original emitron and iconoscope,^[27] and it was used for a public broadcasting by the BBC, for the first time, on Armistice Day 1937.

See also[link]

• Image Dissector
• Video camera tube

External links[link]

• Iconoscope history
• Iconoscope pictures

References[link]

Karl Ferdinand Braun
Born	(1850-06-06)6 June 1850 Fulda, Electorate of Hessen, Germany
Died	20 April 1918(1918-04-20) (aged 67) Brooklyn, New York, USA
Nationality	German
Fields	Physics
Institutions	University of Karlsruhe University of Marburg University of Strassburg University of Tübingen University of Würzburg
Alma mater	University of Marburg University of Berlin
Doctoral advisor	August Kundt
Doctoral students	Leonid Isaakovich Mandelshtam Albert Schweizer
Known for	Cathode ray tube, Cat's whisker diode
Notable awards	Nobel Prize in Physics (1909)

24 September 1900: Bargman, Braun and telegraphist at wireless station Helgoland

Karl Ferdinand Braun (6 June 1850 – 20 April 1918) was a German inventor, physicist and Nobel laureate in physics. Braun contributed significantly to the development of the radio and television technology: he shared with Guglielmo Marconi the 1909 Nobel Prize in Physics.

Biography[link]

Braun was born in Fulda, Germany, and educated at the University of Marburg and received a Ph.D. from the University of Berlin in 1872. In 1874 he discovered that a point-contact semiconductor rectifies alternating current. He became director of the Physical Institute and professor of physics at the University of Strassburg in 1895.

In 1897 he built the first cathode-ray tube (CRT) and cathode ray tube oscilloscope. CRT technology has been replaced by flat screen technologies (such as liquid crystal display (LCD), light emitting diode (LED) and plasma displays) on television sets and computer monitors. The CRT is still called the "Braun tube" in German-speaking countries (Braunsche Röhre) and in Japan (Buraun-kan).

During the development of radio, he also worked on wireless telegraphy. In 1897 Braun joined the line of wireless pioneers.^[1][2] His major contributions were the introduction of a closed tuned circuit in the generating part of the transmitter, and its separation from the radiating part (the antenna) by means of inductive coupling, and later on the usage of crystals for receiving purposes. Wireless telegraphy claimed Dr. Braun's full attention in 1898, and for many years after that he applied himself almost exclusively to the task of solving its problems. Dr. Braun had written extensively on wireless subjects and was well known through his many contributions to the Electrician and other scientific journals.^[3] In 1899, he would apply for the patents, Electro telegraphy by means of condensers and induction colls and Wireless electro transmission of signals over surfaces.^[4]

Around 1898, he invented a crystal diode rectifier or cat's whisker diode. Pioneers working on wireless devices eventually came to a limit of distance they could cover. Connecting the antenna directly to the spark gap produced only a heavily damped pulse train. There were only a few cycles before oscillations ceased. Braun's circuit afforded a much longer sustained oscillation because the energy encountered less losses swinging between coil and Leyden Jars. And by means of inductive antenna coupling the radiator was better matched to the generator. The resultant stronger and less bandwidth consuming signals bridged a much longer distance.

Braun's British patent on tuning was used by Marconi in many of his tuning patents. Guglielmo Marconi used Braun's patents (among others). Marconi would later admit to Braun himself that he had "borrowed" portions of Braun's work. In 1909 Braun shared the Nobel Prize for physics with Marconi for "contributions to the development of wireless telegraphy." The prize awarded to Braun in 1909 depicts this design. Braun experimented at first at the University of Strasbourg. Not before long he bridged a distance of 42 km to the city of Mutzing. In spring 1899 Braun, accompanied by his colleagues Cantor and Zenneck, went to Cuxhaven to continue their experiments at the North Sea. On 24 September 1900 radio telegraphy signals were exchanged regularly with the island of Heligoland over a distance of 62 km. Lightvessels in the river Elbe and a coast station at Cuxhaven commenced a regular radio telegraph service.

Braun went to the United States at the beginning of World War I (before the U.S. had entered the war) to help defend the German wireless station at Sayville, New York, against attacks by the British-controlled Marconi Corporation. After the US entered the war, Braun was being detained, but could move freely within Brooklyn, New York. Braun died in his house in Brooklyn, before the war ended in 1918.

Patents[link]

• U.S. Patent 0,750,429, Wireless Electric Transmission of Signals Over Surfaces
• U.S. Patent 0,763,345, Means for Tuning and Adjusting Electric Circuits

See also[link]

• History of radio
• Invention of radio
• Edouard Branly

References[link]

Footnotes

• In the anime adaptation of the 2009 Japanese visual novel, Steins;Gate, the character Yūgo Tennōji, aka 'Mr. Braun', uses the pseudonym 'FB', after Karl Ferdinand Braun.

General

• K.F. Braun: "On the current conduction in metal sulphides (title translated from German into English)", Ann. Phys. Chem., 153 (1874), 556. (In German) An English translation can be found in "Semiconductor Devices: Pioneering Papers", edited by S.M. Sze, World Scientific, Singapore, 1991, pp. 377–380.
• Keller, Peter A.: The cathode-ray tube: technology, history, and applications. New York: Palisades Press, 1991. ISBN 0-9631559-0-3.
• Keller, Peter A.: "The 100th Anniversary of the Cathode-Ray Tube," Information Display, Vol. 13, No. 10, 1997, pp. 28–32.
• F. Kurylo: "Ferdinand Braun Leben und Wirken des Erfinders der Braunschen Röhre Nobelpreis 1909", München: Moos Verlag, 1965. (In German)

External links[link]

• "Ferdinand Braun – Biography". Nobel Lectures. Physics 1901-1921, Elsevier Publishing Company, Amsterdam, 1967.
• Naughton, Russell, "Karl Ferdinand Braun, Dr : 1850 - 1918".
• "Karl Ferdinand Braun ". Biographies of Famous Electrochemists and Physicists Contributed to Understanding of Electricity.
• Rybak, James P., "Forgotten" Pioneers of Wireless; Part 5 - Karl Ferdinand Braun".
• "Karl Ferdinand Braun, 1850-1918". (German) (English translation)
• The Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik Berlin, Germany
• Alfred Thomas Story A Story of Wireless Telegraphy. D. Appleton and company 1904