The Cathode Ray Tube site
History and Physics Instruments
Vladimir Kosma Zworykin
The electronic eye
The first page
Farnsworth Image dissector 
Early Philips Iconoscope 1935 
Nickname "the bedpan"
RCA 3" Image Orthicon 5820
The huge 4,5" EEV 9224 Image Orthicon with in front a 2/3" Vidicon tube.
This EEV 9224 was the successor of the RCA5820.
RCA's Rose, Law and Weimer managed in 1945
to produce the first usable Image Orthicon.
The biggest difficulty was to make the grid with
1600 holes per square mm, this was important
for the image resolution of the tube.
Also the glass target plate with a thickness of
0,005 mm was not easy to fabricate in those
days. The normal working temperature of the
tube was about 30 degrees Celsius and was
stabilised with a heater and fan.
Philips Iconoscope tube 1930 
The first Philips Iconoscope tube early 1930's.
To the right the complete experimental camera
for 180 TV lines displayed in the Philips laboratory.
The 3" 5820 workhorse tube of the
1950's and 1960's, used in the
RCA TK-11 AND TK-30 camera.
More info about these tubes at the
website of Alan and Sharon Kline .
Electron Multiplier section
This Electron Multiplier section from this RCA tube is an improved version of the one from the image dissector tube of Philo Farnsworth.
Camera tube schematic diagrams
With an 5826 tube.
Philo Taylor Farnsworth
An overview of the camera tube history
In the early days of television, moving picture transmission was only possible by mechanical transmitters and receivers. The development of the CRT which could be used as an electronic replacement of the mechanical receiver forced the researchers to produce an electronic eye to replace the mechanical flying spot principle from Manfred von Ardenne which was more or less successfully used for the transmission of film in the beginning with 30 and later with 180 scanlines.
Campbell Swinton described this all electronic television system in Nature June 1908, info can be found at the site of Bairdtelevision.
Several inventors clamed to have the first ideas for single or double sided target camera pickup tubes, the Hungarian engineer Kolomon Tihanyi claimed the invention of the Iconoscope storage principle, which later was used by Zworykin.
A patent of Kolomon Tihanyi's 1926 Application úRadioskop can be found here but the British one was never granted. Several other people inbetween 1924 and 1931 claimed to file the first pickup tube patents like Francois Charles Pierre Henrouteau (1928) George J.Blake and Henry D.Spooner (1924), Riccardo Brunni(Photoscope 1928) and S.I. Kataev ( Iconoscope 1931)
The first patent (not granted) for the Iconoscope of Zworykin (RCA) dates from 1923 based on his early ideas from 1919, the American Philo Taylor Farnsworth however claimed he had his first ideas of his Image dissector tube in 1922 when he, at an age of 14, made a drawing of his TV pickup tube on the blackboard of his school.
Farnsworth patented his all electronic TV system on Jan 7, 1927. By Sept 7, 1927 he was able to send a single horizontal line of light on the face of a CRT. The dissector tube however, became never a successful television pickup device and was mainly used to scan film and dia-positives, this was the result of a lack of sensitivity, it was in fact a cold cathode tube.
TV broadcast was not easy with the dissector tube because of the enormous amount of light needed for an acceptable picture, despite all he managed to transmit from August 25 1934 for ten day's live electronic television, he was the first ever. Kenjiro Takayanagi made the first camera tube for Japan and presented his all electronic TV system also in 1936. The next year German Nazi TV started regular broadcasting in Berlin using their first Iconoscope cameras at the Olympic Games in 1936.
Farnsworth's Image dissector and his TV display tube the "oscillite" a low pressure gas filled CRT, were no match for the mighty RCA (David Sarnoff). This was the beginning of the all electronic TV age, it was a race of patents which RCA eventually won. RCA didn't wanted to pay royalties but would only buy the dissector patent of Farnsworth for use of the multiplier section in the future development of the Image Orthicon. With this arrangement ended the great struggle between Farnsworth and RCA.
The first Iconoscope tubes that Zworykin developed for RCA were about 1000 times more sensitive than the Farnsworth Image dissector which had no storage capacity, the Iconoscope tubes used the "gathering effect" to collect electrons coming from the photo cathode to the mica target. But only 5-10% effectivity was reached, another disadvantage of the Iconoscope tube was shadow forming, due to the irregular form of the electron cloud in front of the target. This could be seen as dark spots on the receiving image on the upper left and bottom left of the picture.
The successor of the Iconoscope was the Super Emitron, patented in May 1934 by Hans G. Lubszinski and Sydney Rodda of EMI England, the patent later went to RCA due to an earlier conception date. The image of the Super Emitron was not formed by the photo-emission to the target plate itself, but by photo-electrons which came free by the illumination of a Photo Cathode in front of the target. This tube was much more efficient than the standard Iconoscope tube.
Even more progress was made with the Riesel-Iconoscope. In the Riesel tube there was a second photo sensitive Cathode in the form of a ring nearby the target. From this Cathode a constant flow of slow electrons was dripping to the target. (rieseln = dripping) This became a new shadow compensation to overcome the the old problem. The Riesel Iconoscope tube was only used on the mainland of Europe and had a 10 times higher sensitivity than the regular Iconoscope tube.
Harley Ambrose Iams and Alberts Rose (RCA) developed in 1938 the Orthicon tube, although it was theoretically a simpler design than the Iconoscope, building this tube was much more difficult. This Orthicon tube was used for the first NBC/RCA TV broadcasting in NewYork June 1940.
It took another five years to build a new and better one, the Image Orthicon. It used the Electron Multiplier section like the Image Dissector tube which was developed by Philo Tayler Farnsworth. Development of the first 3" Image orthicon started in 1944 with the LM5 for the use in guided missiles followed by the smaller MIMO (miniature image orthicon). This was a great advance for the postwar TV industry, RCA presented the fist public demonstration Oct 25 1945, the production was extended for a short time with the building of the huge 4,5" Image orthicon which was even more sensitive but much larger than the former ones and also more expensive. Image Orthicons were valued and insured for 500-1000 pounds at the BBC in 1950, in those days a lot of money !
To overcome this, the Vidicon tube was eventually developed in 1950, there was no need to be superior to the Image orthicon, but to produce camera tubes in a more economic way. Vidicon tubes were used until 1970 when the first solid state CCD camera came on the market. Even today the Vidicon and Vidicon-like tubes are still used in the industrial, medical and military environment.
The electron gun on the above is the same as the one on the picture. Found in a flea market! Probably all that is left today of this early 1935 Philips camera tube.
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