Physics

The Emergence of Television


The emergence of television is due to great mathematicians and physicists, who belong to the exact sciences, who gave the humanities a great and powerful vehicle. Since the early nineteenth century, scientists had been concerned with the transmission of images at a distance, and it was with the invention of Alexander Bain in 1842 that the telegraphic transmission of an image (facsimile), now known as fax, was obtained.

In 1817, Swedish chemist Jons Jacob Berzelius discovered selenium, but it was only 56 years later, in 1873, that Englishman Willoughby Smith proved that selenium had the property of transforming light energy into electrical energy. Through this discovery one can formulate the transmission of images through the electric current.

In 1884, the young German Paul Nipkow invented a disk with spiral holes the same distance from each other that caused the object to be subdivided into small elements that together form an image.

In 1892, Julius Elster and Hans Getiel invented the electric signal photoelectric cell. In which he transformed each subdivision in 1906, Arbwehnelt developed a cathode ray television system, the same in Russia by Boris Rosing. The system employed mechanical mirror scanning plus the cathode ray tube. In 1920, true transmissions were made, thanks to the Englishman John Logie Baird, through the mechanical system based on Nipkow's invention. Four years later, in 1924, Baird transmitted contours of objects at a distance and the following year, faces of people. As early as 1926, Baird made his first demonstration at the Royal Institution in London for the scientific community and soon after signed a contract with the BBC for experimental broadcasts. The definition standard had 30 lines and was mechanical.

During this period, in 1923, Russian Wladimir Zworykin discovered the iconoscope, an invention that used cathode ray tubes. In 1927, Philo Farnsworth also discovered a cathode ray dissecting system, but with unsatisfactory resolution. Zworykin was invited by RCA to head the team that would produce the first television tube, called orticon, which was produced on an industrial scale from 1945 onwards.

In March 1935, television is officially broadcast in Germany, and in November in France, the Eiffel Tower being the broadcasting station.

In 1936, London uses 405-line definition images and the regular BBC station opens. The following year, three electronic cameras broadcast the coronation ceremony of George VI, with about fifty thousand viewers.

In Russia, television began to operate in 1938 and in United Studies in 1939. During World War II, Germany was the only European country to keep television on air.

Paris returned with broadcasts in October 1944, Moscow in December 1945 and the BBC in June 1946 with the broadcast of the Victory Parade. In 1950, France had an 819-line broadcasting station, 405-line England, 625-line Russians, and 525-line United States and Japan. In September of that same year, the Tupi TV of São Paulo opens, owned by journalist Assis Chateaubriand, owner of the Diários Associados, with an American-based system.

In short it can be said that the TV camera captures the images, decomposing them into electrical signals that are sent to an electronic center, the modeler (apparatus that modulates the waves in an oscillator). The signals are sent in the form of waves by a large transmitting antenna that is sent to the receiving apparatus that undoes the signals, recomposing them in their original position, reproducing the transmitted image on the screen.

The formation of the image is instantaneous. The electronic device uses dots instead of lines and can draw the entire frame every 1/25 of a second. Antennas were used to transmit the image from one place to another, but as but as the waves are in a straight line it was difficult to transmit to the other side of the globe due to curvature, thus seeking a spatial solution. On 23 July 1962, the first satellite broadcast, the Telstar artificial satellite, launched by the US NASA.

The progress of space engineering and telecommunications has allowed satellites to orbit around the earth. They are the ones that guarantee the television transmissions and the intercontinental telephone communications that allow to communicate the same signal all over the world at the same time.

Start of color transmissions

Regular color transmissions in the U.S. began in 1954. But as early as 1929, Hebert Eugene Ives made the first color images at 50 wire definition lines in New York, about 18 frames per second. Peter Goldmark perfected the mechanical invention by demonstrating at 343 lines at 20 frames per second in 1940.

Several systems were created, but they all met a strong barrier: if a new system were to emerge, what to do with the old black and white devices that were already about 10 million in the early 1950s? A special committee was created in the United States to literally put color into the black and white system. This committee was named the National Television System Committee (also known as the National Television Standards Committee), whose initials served to name the new system, NTSC. The developed system was based on using the black and white pattern that worked with luminance levels (Y) and added the chronance (C), ie the color. The principle of capturing and receiving color images lies in the decomposition of white light into three primary colors which are red (R de red), green (G de green) and blue (B de blue). At a ratio of levels of 30% R, 59% G and 11% B. On reception the process is reversed, the image consists of the sum of the pixel colors, ie at the points of the television screen.

In 1967, a variation of the American system came into operation in Germany, solving some weaknesses of this system that was named Phase Alternation Line, giving the initials for the PAL system.

That same year, SECAM (Séquentille Coleur à Memoire) entered France, but not compatible with the French black and white system.

The first official color broadcast in Brazil took place on March 31, 1972. The development of the TV was so great that the available Very High Frequency (VHF) channels became saturated, thus extending the use of VHF. UHF (Ultra High Frequency) range. Thus TV manufacturers were forced to build a device capable of capturing all channels to make UHF band programs accessible.
Broadcasting a live program requires the participation of a large and highly qualified team that can be divided into four groups: scene personnel, color and lighting control, sound and direction control. All feature in this scheme of a current studio.

Source: //www.notapositivo.com