A sectional view of an image orthicon is shown in the below figure. It has three main sections: image section, scanning section and electron. Image orthicon definition, a camera tube, more sensitive than the orthicon, in which an electron image generated by a photocathode is focused on one side of a. The image orthicon (10) was developed during World War II to solve some of the problems of its predecessors in the camera-tube family. These included.
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The photo-electrons are focused on to the target by the combined action of the electrostatic field and a longitudinal magnetic field, the latter being produced by an external coil.
This is maintained at about volts more positive with respect to the photocathode, and the resultant electric field gives the desired acceleration and motion to the emitted electrons towards it. The aperture is a part of a metal disc covering the gun acmera.
Early color cameras used the obvious technique of using separate red, green and blue image tubes in conjunction with a camrra separatora technique still in use with rube solid state cameras today. Its first image was transmitted in late summer of and a patent was issued in Radio and Communication Engineering, volume 97, issue February Learn how and when to remove this template message. However, it tends to flare in bright light, causing a dark halo to be seen around the object; this anomaly is referred to as ” blooming ” in the broadcast industry when image orthicon tubes were in operation.
The mysterious dark “orthicon halo” around bright objects in an IO-captured image is based hube the fact that the IO relies on the emission of photoelectrons, but very bright illumination can produce more of them locally than the device can successfully deal with.
Inwhile employed by the Westinghouse Electric Corporation in Pittsburgh, Pennsylvania, Russian-born American engineer Vladimir Zworykin presented a project for a totally electronic television system to the company’s general manager. These focus coils are essentially as long as the tubes themselves, and surround the deflection yoke coils.
At this point the electrons lose speed and get deflected by the horizontal and vertical deflection coils, effectively scanning the target. In the image store, light falls upon the photocathode which is a photosensitive plate at a very negative potential approx. In effect, the electrons travel along cwmera lines of force, although csmera, in detail.
The advantage of this arrangement was that for virtually every color, the video level of the green component was always less than the cyan, and similarly the cyan was always less than the white. The target end of the wall coating grid No. Only one tube was used in the camera, instead of a tube for each color, as was standard for color cameras used in television broadcasting. Although the idea of using color stripe filters over the target was not new, the Trinicon was the only tube to use the primary RGB colors.
The light came from either an illuminator mounted around the target, or in more professional cameras from a light source on the base of the tube and guided to the target by light piping.
This tube makes use of the otthicon photoemissive sensitivity obtainable from photocathodes, image multiplication at the target caused by secondary emission and an electron multiplier.
Image Section The image section contains a semi-transparent photo-cathode on the inside of the faceplate, and electrodes to provide an accelerating electrostatic field to the target. The beam is focused at the target by the magnetic field of the external focusing coil and the electrostatic field of the wall coating grid No.
They have excellent resolution compared to image orthicons, but lack the artificially sharp edges of IO tubes, which cause some of the viewing audience to perceive them as softer.
Proceedings of the Physical Society. Newvicon is a registered trademark of Matsushita from Since the statuette was female, it was feminized into ” Emmy “. Archived from the original on October 31, Retrieved 23 November The number of reflected electrons is a linear measure of the target’s original positive charge, which, in turn, is a measure of brightness.
The Institute of Electrical Engineers. An image of the scene to be televised is focused by an optical lens system on oorthicon the photo-cathode and causes photo-electrons to be emitted. During the s and s, field-sequential color systems were developed which used synchronized motor-driven color-filter disks at the camera’s image tube and at the television receiver. Electrons inside these long focus coils take helical paths as they travel along the length of the tube.
Video camera tube
It represented a considerable advance in the television field, and after further development work, RCA created original models between and Proceedings of the Institute of Radio Engineers. In order to reduce the intensity of the image of the first dynode which will be super-imposed on the transmitted picture, the whole of the multiplier section assembly is mounted off centre.
This section does not cite any sources.
One might say that this sort of deflection starts to create S-bends in the lines of force, but doesn’t become anywhere near to that extreme. From Wikipedia, the free encyclopedia.
Image orthicon | electronics |
One technique has already been described Trinicon above. Diagrams in this article show that the focus coil surrounds the camera tube; it is much longer than the focus coils for earlier TV CRTs. A switch-over to solid-state image sensors rendered much of that equipment and the investments behind it obsolete and required new equipment optimized to work well with solid-state sensors, just as the old equipment was optimized for tube-sourced video.
Finally, an electron beam periodically sweeps across the target, effectively scanning the stored image, discharging each granule, and producing an electronic signal like in the iconoscope.
Due to its wide spectral responseit is labelled as panchromatic selenium vidiconhence the achronym ‘pasecon’. Since darker images produce less positive charge on prthicon target, the excess electrons deposited by the splash will be read as a dark region by the scanning electron beam.
Scanning Section The face of the target remote from the photo-cathode is scanned by an electron beam emanating from a triode electron gun, the potentials being so adjusted that the beam approaches the target with a substantially zero velocity and is, therefore, ikage to produce unwanted secondary electrons. New TV Camera Tube. The technique would not work with the baseline vidicon tube because it suffered from orthicoj limitation that as the target was fundamentally an insulator, the constant low light level built up a charge which would manifest itself as a form of ‘fogging’.
This configurations tubee the use of a straight camera tube, because the scene to be transmitted, the charge storage plate, and the electron gun can be aligned one after the other.
These coils are fed from two oscillators, one working at Hz.
Image Orthicon Camera Tubes
In the camera, the disk was in the optical path, and in the receiver, it was in front of the CRT. The return beam, comprising electrons which are not required for neutralising the charge on the target, travels back along approximately the same path as the outgoing electron beam and is directed into a five-stage electron multiplier where it is amplified to become the output video signal.
The target is nearly at ground potential with a small positive camers, thus when the electrons reach the target at low speed they are absorbed without ejecting more electrons. It will be appreciated that when the beam moves from a less positive portion of the target to a more positive portion, the signal output voltage across the load resistor changes in the positive direction.
As a precaution against light leakage, which has been shown to cause spurious results, the gun end of the tube is coated with an opaque imzge.