Tag: 20s

Read more about Electronic Television here.

In 1897, English physicist J. J. Thomson was able, in his three well-known experiments, to deflect cathode rays, a fundamental function of the modern cathode-ray tube. The earliest version of the cathode ray tube (CRT) was invented by the German physicist Ferdinand Braun in 1897 and is also known as the Braun tube.  It was a cold-cathode diode, a modification of the Crookes tube, with a phosphor-coated screen.  Braun was the first to conceive the use of a CRT as a display device.  The Braun tube became the foundation of 20th-century television.  In 1906 the Germans Max Dieckmann and Gustav Glage produced raster images for the first time in a CRT.  In 1907, Russian scientist Boris Rosing used a CRT in the receiving end of an experimental video signal to form a picture.  He managed to display simple geometric shapes on the screen.

In 1908, Alan Archibald Campbell-Swinton, fellow of the Royal Society, published a letter in the scientific journal Nature in which he described how distant electric vision could be achieved by using a cathode-ray tube, or Braun tube, as both a transmitting and receiving device, he expanded on his vision in a speech given in London in 1911 and reported in The Times and the Journal of the Rontgen Society in another letter to Nature published in October 1926.  Campbell-Swinton also announced the results of some not-very-successful experiments he had conducted with G. M. Minchin and J. C. M. Stanton.  They attempted to generate an electrical signal by projecting an image onto a selenium-coated metal plate that was simultaneously scanned by a cathode ray beam.  These experiments were conducted before March 1914, when Minchin died, but they were later repeated by two different teams in 1937, by H. Miller and J. W. Strange from Electric and Musical Industries Ltd. (EMI), and by H. Iams and A. Rose from Radio Corporation of America (RCA).  Both teams succeeded in transmitting very faint images with the original Campbell-Swinton’s selenium-coated plate.  Although others had experimented with using a cathode-ray tube as a receiver, the concept of using one as a transmitter was novel.  The first cathode-ray tube to use a hot cathode was developed by John B. Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric and became a commercial product in 1922.

In 1926, Hungarian engineer Kalman Tihanyi designed a television (TV) system using fully electronic scanning and display elements and employing the principle of charge storage within the scanning (or camera) tube.  The problem of low sensitivity to light resulting in low electrical output from transmitting (or camera) tubes would be solved with the introduction of charge-storage technology by Kalman Tihanyi beginning in 1924.  His solution was a camera tube that accumulated and stored electrical charges (photoelectrons) within the tube throughout each scanning cycle.  The device was first described in a patent application he filed in Hungary in March 1926 for a television system he called Radioskop.  After further refinements included in a 1928 patent application, Tihanyi’s patent was declared void in Great Britain in 1930, so he applied for patents in the United States (U.S.).  Although his breakthrough would be incorporated into RCA’s iconoscope design in 1931, the U.S. patent for Tihanyi’s transmitting tube would not be granted until May 1939.  The patent for his receiving tube had been granted the previous October.  Both patents had been purchased by RCA prior to their approval.  Charge storage remains a basic principle in the design of imaging devices for television to the present day.  On Christmas Day, 1926, at Hamamatsu Industrial High School in Japan, Japanese inventor Kenjiro Takayanagi demonstrated a TV system with a 40-line resolution that employed a CRT display.  This was the first working example of a fully electronic television receiver and Takayanagi’s team later made improvements to this system parallel to other TV developments.  Takayanagi did not apply for a patent.

In the 1930’s, Allen B. DuMont made the first CRT to last 1,000 hours of use, which was one of the factors that led to the widespread adoption of TV.

On the 7th of September 1927, U.S. inventor Philo Farnsworth’s image dissector camera tube transmitted its first image, a simple straight line, at his laboratory at 202 Green Street in San Francisco.  By the 3rd of September 1928, Farnsworth had developed the system sufficiently to hold a demonstration for the press.  This is widely regarded as the first electronic television demonstration.  In 1929, the system was improved further by the elimination of a motor generator, so that his television system now had no mechanical parts.  That year, Farnsworth transmitted the first live human images with his system, including a three-and-a-half-inch image of his wife Elma (nicknamed Pem) with her eyes closed (possibly due to the bright lighting required).

Meanwhile, Vladimir Zworykin was also experimenting with the cathode-ray tube to create and show images.  While working for Westinghouse Electric in 1923, he began to develop an electronic camera tube.  But in a 1925 demonstration, the image was dim, had low contrast, and poor definition, and was stationary.  Zworykin’s imaging tube never got beyond the laboratory stage but RCA, which acquired the Westinghouse patent, asserted that the patent for Farnsworth’s 1927 image dissector was written so broadly that it would exclude any other electronic imaging device.  Thus RCA, on the basis of Zworykin’s 1923 patent application, filed a patent interference suit against Farnsworth. The U.S. Patent Office examiner disagreed in a 1935 decision, finding priority of invention for Farnsworth against Zworykin.  Farnsworth claimed that Zworykin’s 1923 system could not produce an electrical image of the type to challenge his patent.  Zworykin received a patent in 1928 for a colour transmission version of his 1923 patent application.  He also divided his original application in 1931.  Zworykin was unable or unwilling to introduce evidence of a working model of his tube that was based on his 1923 patent application. In September 1939, after losing an appeal in the courts, and being determined to go forward with the commercial manufacturing of television equipment, RCA agreed to pay Farnsworth US$1 million over a ten-year period, in addition to license payments, to use his patents.

In 1933, RCA introduced an improved camera tube that relied on Tihanyi’s charge storage principle.  Called the Iconoscope by Zworykin, the new tube had a light sensitivity of about 75,000 lux and thus was claimed to be much more sensitive than Farnsworth’s image dissector.  However, Farnsworth had overcome his power issues with his Image Dissector through the invention of a completely unique multipactor device that he began work on in 1930, and demonstrated in 1931.  This small tube could amplify a signal reportedly to the 60th power or better and showed great promise in all fields of electronics.  Unfortunately, an issue with the multipactor was that it wore out at an unsatisfactory rate.

At the Berlin Radio Show in August 1931 in Berlin, Manfred von Ardenne gave a public demonstration of a television system using a CRT for both transmission and reception, the first completely electronic television transmission.  However, Ardenne had not developed a camera tube, using the CRT instead as a flying-spot scanner to scan slides and film.  Ardenne achieved his first transmission of TV pictures on Christmas Eve, 1933, followed by test runs for a public television service in 1934.  The world’s first electronically scanned TV service started in Berlin in 1935, the Fernsehsender Paul Nipkow, culminating in the live broadcast of the 1936 Summer Olympic Games from Berlin to public places all over Germany.

Philo Farnsworth gave the world’s first public demonstration of an all-electronic TV system, using a live camera, at the Franklin Institute of Philadelphia on the 25th of August 1934, and for ten days afterwards.  Mexican inventor Guillermo Gonzalez Camarena also played an important role in early telly.  His experiments with TV (known as telectroescopía at first) began in 1931 and led to a patent for the trichromatic field sequential system colour TV in 1940.  In Britain, the EMI engineering team led by Isaac Shoenberg applied in 1932 for a patent for a new device they called the Emitron, which formed the heart of the cameras they designed for the British Broadcasting Company (BBC).   On the 2nd of November 1936, a 405-line broadcasting service employing the Emitron began at studios in Alexandra Palace, and transmitted from a specially built mast atop one of the Victorian building’s towers.  It alternated for a short time with Baird’s mechanical system in adjoining studios but was more reliable and visibly superior.  This was the world’s first regular high-definition television (HDTV) service. 

The original U.S. iconoscope was noisy, had a high ratio of interference to signal, and ultimately gave disappointing results, especially when compared to the high-definition (HD) mechanical scanning systems that became available.  The Electric and Musical Industries Ltd. (EMI) team, under the supervision of Isaac Shoenberg, analysed how the iconoscope (or Emitron) produces an electronic signal and concluded that its real efficiency was only about 5% of the theoretical maximum.  They solved this problem by developing, and patenting in 1934, two new camera tubes dubbed super-Emitron and CPS Emitron.  The super-Emitron was between ten and fifteen times more sensitive than the original Emitron and iconoscope tubes and, in some cases, this ratio was considerably greater.  It was used for outside broadcasting by the British Broadcasting Company (BBC), for the first time, on Armistice Day 1937, when the general public could watch on a TV set as the King laid a wreath at the Cenotaph.  This was the first time that anyone had broadcast a live street scene from cameras installed on the roof of neighbouring buildings because neither Farnsworth nor R.C.A. would do the same until the 1939 New York World’s Fair.

On the other hand, in 1934, Zworykin shared some patent rights with the German licensee company Telefunken.  The image iconoscope (Superikonoskop in Germany) was produced as a result of the collaboration.  This tube is essentially identical to the super-Emitron.  The production and commercialisation of the super-Emitron and image iconoscope in Europe were not affected by the patent war between Zworykin and Farnsworth, because Dieckmann and Hell had priority in Germany for the invention of the image dissector, having submitted a patent application for their Lichtelektrische Bildzerlegerrohre fur Fernseher (Photoelectric Image Dissector Tube for Television) in Germany in 1925, two years before Farnsworth did the same in the United States.  The image iconoscope (Superikonoskop) became the industrial standard for public broadcasting in Europe from 1936 until 1960 when it was replaced by the vidicon and plumbicon tubes.  Indeed, it was the representative of the European tradition in electronic tubes competing against the American tradition represented by the image orthicon.  The German company Heimann produced the Superikonoskop for the 1936 Berlin Olympic Games, later Heimann also produced and commercialised it from 1940 to 1955.  From 1952 to 1958 the Dutch company Philips finally produced and commercialised the image iconoscope and multicon.

U.S. television broadcasting, at the time, consisted of a variety of markets in a wide range of sizes, each competing for programming and dominance with separate technology, until deals were made and standards agreed upon in 1941.  RCA, for example, used only Iconoscopes in the New York area, but Farnsworth Image Dissectors in Philadelphia and San Francisco.  In September 1939, RCA agreed to pay the Farnsworth Television and Radio Corporation royalties over the next ten years for access to Farnsworth’s patents.  With this historic agreement in place, RCA integrated much of what was best about Farnsworth Technology into their systems.  In 1941, the United States implemented 525-line television.  Electrical engineer Benjamin Adler played a prominent role in the development of television.

The world’s first 625-line TV standard was designed in the Soviet Union in 1944 and became a national standard in 1946.  The first broadcast in 625-line standard occurred in Moscow in 1948.  The concept of 625 lines per frame was subsequently implemented in the European CCIR standard.  In 1936, Kalman Tihanyi described the principle of plasma display, the first flat panel display system.

Early electronic TV sets were large and bulky, with analogue circuits made of vacuum tubes.  Following the invention of the first working transistor at Bell Labs, Sony founder Masaru Ibuka predicted in 1952 that the transition to electronic circuits made of transistors would lead to smaller and more portable TV sets.  The first fully transistorised, portable solid-state television set was the 8-inch Sony TV8-301, developed in 1959 and released in 1960.  This began the transformation of TV viewership from a communal viewing experience to a solitary viewing experience.  By 1960, Sony had sold over 4 million portable TV sets worldwide.