History of Television

 

The History of Television

The history of television is both complex and far-reaching, involving the work of many inventors and engineers in several countries over many decades. Initially, work proceeded along two different but overlapping lines of development: those designs employing both mechanical and electronic principles, and those employing only electronic principles. Electromechanical television would eventually be
abandoned in favour of fully electronic designs. The origins of what would become todays television system can be traced back to the discovery of the photoconductivity of the element selenium by Willoughby Smith in 1873, the invention of a scanning disk by Paul Gottlieb Nipkow in 1884, John Logie Bairds demonstration of televised moving images in 1926 and Philo Farnsworths Image dissector in 1927.

The 20 year old German university student Nipkow proposed and patented the first electromechanical television system in 1884, although he never built a working model of the system. Nipkows spinning disk design is credited with being the first television image rasterizer. Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the International World Fair in Paris on August 25, 1900.
Perskyis paper reviewed the existing electromechanical technologies, mentioning the work of Nipkow and others. The photoconductivity of selenium and Nipkows scanning disk were first joined for practical use in the electronic transmission of still pictures and photographs, and by the first decade of the 20th century halftone photographs, composed of equally spaced dots of varying size, were being transmitted by facsimile over telegraph and telephone lines as a newspaper service.

However, it wasnt until 1907 that developments in amplification tube technology, by Lee DeForest and Arthur Korn among others, made the design practical. The first demonstration of the instantaneous transmission of still silhouette images was by Georges Rignoux and A. Fournier in Paris in 1909, using a rotating mirror-drum as the scanner, and a matrix of 64 selenium cells as the receiver.

In 1911, Boris Rosing and his student Vladimir Kozmich Zworykin created a television system that used a mechanical mirror-drum scanner to transmit, in Zworykins words, “very crude images” over wires to the electronic Braun tube (cathode ray tube or “CRT”) in the receiver. Moving images were not possible because, in the scanner, “the sensitivity was not enough and the selenium cell was very laggy”.

On March 25, 1925, Scottish inventor John Logie Baird gave a demonstration of televised silhouette images in motion at Selfridge Department Store in London. ATandTs Bell Telephone Laboratories transmitted halftone still images of transparencies in May 1925. Charles Francis Jenkins was able to demonstrate on June 13, 1925, the transmission of the silhouette image of a toy windmill in motion from a naval radio station to his laboratory in Washington, using a lensed disk scanner with 48 lines per picture, 16 pictures per second.

However, if television is defined as the live transmission of moving images with continuous tonal variation, Baird first achieved this privately on October 2, 1925. But strictly speaking, Baird had not yet achieved moving images on October 2. His scanner worked at only five images per second, below the threshold required to give the illusion of motion, usually defined as at least 12 images per second. By January, he had improved the scan rate to 12.5 images per second. Then he gave the worlds first public demonstration of a working television system to members of the Royal Institution and a newspaper reporter on January 26, 1926 at his laboratory in London. Unlike later electronic systems with several hundred lines of resolution, Bairds vertically scanned image, using a scanning disk embedded with a double spiral of lenses, had only 30 lines, just enough to reproduce a recognizable human face.

In 1927, Baird transmitted a signal over 438 miles (705 km) of telephone line between London and Glasgow. In 1928, Bairds company (Baird Television Development Company/Cinema Television) broadcast the first transatlantic television signal, between London and New York, and the first shore-to-ship transmission. He also demonstrated an electromechanical colour, infrared dubbed “Noctovision”), and stereoscopic television, using additional lenses, disks and filters. In parallel, Baird developed a video disk recording system dubbed “Phonovision”; a number of the Phonovision
recordings, dating back to 1927, still exist. In 1929, he became involved in the first experimental electromechanical television service in Germany. In November 1929, Baird and Bernard Natan of Pathe established Frances first television company, Télévision-Baird-Natan. In 1931, he made the first live transmission, of the Epsom Derby. In 1932, he demonstrated ultra-short wave television. Bairds electromechanical system reached a peak of 240 lines of resolution on BBC television broadcasts in 1936, before being discontinued in favour of a 405-line all-electronic system developed by Marconi-EMI.

In parallel, Herbert E. Ives of Bell Labs gave another dramatic demonstration of low-frame-rate television on April 7, 1927, when he field tested reflected-light television systems using small-scale (2 by 2.5 inches) and large-scale (24 by 30 inches) viewing screens over a wire link from Washington to New York City, and over-the-air broadcast from Whippany, New Jersey. The subjects, who included Secretary of Commerce Herbert Hoover, were illuminated by a flying-spot scanner beam that was scanned by a 50-aperture disk at a rate of 16 pictures per minute (about one picture every 4 seconds).

Meanwhile in Soviet Russia, Léon Theremin had been developing a mirror drum-based television, starting with 16 lines resolution in 1925, then 32 lines and eventually 64 using interlacing in 1926, and as part of his thesis on May 7, 1926 he electrically transmitted and then projected near-simultaneous moving images on a five foot square screen. By 1927 he achieved an image of 100 lines, a resolution that was not surpassed until 1931 by RCA, with 120 lines.

On December 25, 1926, Kenjiro Takayanagi demonstrated a television system with a 40-line resolution that employed a Nipkow disk scanner and CRT display at Hamamatsu Industrial High School in Japan. This prototype is still on display at the Takayanagi Memorial Museum in Shizuoka University, Hamamatsu Campus. His research in creating a production model were halted by the US after Japan lost World War II.

In 1911, engineer Alan Archibald Campbell-Swinton gave a speech in London, reported in The Times (UK), describing in great detail how distant electric vision could be achieved by using cathode ray tubes at both the transmitting and receiving ends. The speech, which expanded on a letter he wrote to the journal Nature in 1908, was the first iteration of the electronic television method that is still used today. Others had already experimented with using a cathode ray tube as a receiver, but the concept of using one as a transmitter was novel. By the late 1920s, when electromechanical television was still being introduced, several inventors were already working separately on versions of all-electronic transmitting tubes, including Kálmán Tihanyi in Hungary, and Philo Farnsworth and Vladimir Zworykin in the United States.

The decisive solution, the accumulation and storage of electrical charges (“photoelectrons”) within the transmitting tube throughout each scanning cycle, was first described on March 1926 by Kálmán Tihanyi, and appeared in a patent application for his “Radioskop” he filed in Hungary. Tihanyi was awarded patents for his television system in both France and Great Britain in 1928, and applied for patents in the United States in June of the following year. Although his breakthrough would be incorporated into the design of RCA’s “iconoscope” in 1931, the U.S. patent for Tihanyis transmitting tube would not be granted until May 1939. The patents for his receiving tube had been granted the previous October. Both patents had been
purchased by RCA prior to their approval. On September 7, 1927, Philo Farnsworths Image Dissector camera tube transmitted its first image, a simple straight line, at his laboratory at 202 Green Street in San Francisco. By 1928, Farnsworth had developed the system sufficiently to hold a demonstration for the press, televising a motion picture film. In 1929, the system was further improved by 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 (“Pem”) with her eyes closed (possibly due to the bright lighting required).

Farnsworth gave the his first public demonstration of a complete all-electronic television system on August 25, 1934 at the Franklin Institute in Philadelphia. Other inventors had previously demonstrated components of such a system, or had shown an electronic system using still images or motion picture film. Manfred von Ardenne demonstrated an all-electronic television system using cathode ray tubes at the Berlin Radio Show in August 1931, but as he never built a camera tube, his system was
limited to using the CRT as a flying spot scanner to transmit motion picture films and slides. Farnsworth became the first to use all-electronic cameras and receivers to transmit and receive live, moving images. Unfortunately, his cameras needed too much light, so his work came to a stop. Despite many useful improvements he developed for television, Farnsworth’s camera didnt use the image-storage principle. (Its competitor the Iconoscope required less lighting than Farnsworths image dissector. Moreover it produced significantly sharper image therefore this system superseded the Farnsworth-system)

Vladimir Zworykin was also experimenting with the cathode ray tube to create and show images. While at Westinghouse in 1923, he developed an electronic camera tube. But in a 1925 demonstration, the image was dim, had low contrast and poor definition, and was stationary. The tube never got beyond the laboratory stage, but RCA (which had acquired the Westinghouse patent) believed the patent on Farnsworths 1927 image dissector was written so broadly that it would exclude any other electronic formation of an image. And so RCA, armed with Zworykins 1923 patent application, filed a patent interference suit against Farnsworth. The U.S. Patent Office examiner
is agreed in a 1935 decision, finding priority of invention for Farnsworth against Zworykin. Farnsworth claimed that Zworykins 1923 system would be unable to produce an electrical image of the type to challenge to Farnsworths patent. Zworykin was unable or unwilling to introduce in evidence a working model of his tube that was based on his 1923 patent description. In October 1939, after losing an appeal in the courts and wishing to go forward with the commercial manufacturing of television equipment, RCA agreed to pay Farnsworth US$1 million (the equivalent of $13.8 million in 2006) over a ten-year period, in addition to license payments, to use Farnsworths patents.

In 1931 RCA introduced an improved camera tube that relied on Kálmán Tihanyis principle of storage of electrical charges within the tube. Dubbed the iconoscope by Zworykin, the new tube had a light sensitivity of about 75,000 lux, and thus was much more sensitive than Farnsworths image dissector. It was also easier to manufacture and produced a very clear image. The iconoscope was the primary camera tube used in American broadcasting from 1936 until 1946, when it was replaced by the image orthicon tube.

In Britain Isaac Shoenberg used Zworykins design to develop Marconi-EMIs own Emitron tube, which formed the heart of the cameras they designed for the BBC. Using this, on November 2, 1936 a 405 line service was started from studios at Alexandra Palace, and transmitted from a specially-built mast atop one of the Victorian buildings towers; it alternated for a short time with Bairds mechanical system in adjoining studios, but was more reliable and visibly superior. So began the worlds first high-definition regular service. The mast is still in use today.

Also in 1936, according to Kálmán Tihanyis daughter Katalin Tihanyi Glass, Tihanyi described the principle of “plasma television” and designed the first flat panel receiver.

In its most basic form, a colour broadcast can be created by broadcasting three monochrome images, one each in the three colours of red, green and blue (RGB). When displayed in fast succession, these colours will blend together to produce a single colour as seen by the viewer. One of the great technical challenges of introducing colour broadcasting was the desire to reduce the high bandwidth, three times that of the existing black and white (B and W) standards, into something more acceptable that would not use up most
of the available radio spectrum. After considerable research, the NTSC introduced a system that encoded the colour information separately from the brightness, and greatly reduced the resolution of the colour information in order to conserve bandwidth. The brightness image remained compatible with existing B and W television sets, at slightly reduced resolution, while colour televisions could decode the extra information in the signal and produce a limited-colour display. The higher resolution B and W and lower resolution colour images combine in the eye to produce a seemingly high resolution colour image. The NTSC standard represents a major technical achievement.

Although introduced in the U.S. in the 1950s, only a few years after black and white televisions had been standardized there, high prices and lack of broadcast material greatly slowed its acceptance in the marketplace. It was not until the late 1960s that colour sets started selling in large numbers, due in some part to the introduction of GEs Porta-Color set in 1966. By the
1970s colour sets had become standard, with all-colour broadcasts becoming common. Colour broadcasting in Europe was not standardized on the PAL format until the 1960s, and broadcasts did not start until 1967. By this point many of the technical problems in the early sets had been worked out, and the spread of colour sets in Europe was fairly rapid. Most major markets in North America and Europe were all colour by the 1970s, and by the 1980s B and W sets had been pushed into niche markets, notably low-power uses or small portable sets.

The recent switch to all-digital broadcasting in the U.S. has made B and W sets largely unusable, after 50 years of compatibility with an increasingly colour world.

History of Television – Videos

History of Television – Videos – The Origins of Television

This short video shows the origins of television.

 

History of Television – Videos – The story of television, Part 1 of 2

This short video shows the story of television.

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