Vidicon tube

Video links Video recording Video sensor Video tape Video tapes Vidicon Vidicons Vidicon tubes Vifilcon-A... 

Tin oxide and indium oxide [1312-43-2] Iu202, are other important semiconductors that are doped to increase conductivity. Sn02, Iu202, Ti02, and in particular, SrTiO, are transparent to visible light and are often used as transparent electrodes, for example, on vidicon tubes. 

Fig. 14. Scheme of the vidicon tube. (1) Scanning beam (cathode potential F = 0 volt) (2) gauze (3) dye film (4) transparent supporting electrode (potential +30 volt) (5) amplifier (6) galvanometer... 

Vidicon. Although there are several types of vidicon tubes presently available, the most promising of these for spectroscopic work is the silicon vidicon, first conceived at Bell Labs (68). Figure 3 shows a diagram of a silicon vidicon. In contrast to a photomultiplier, which is based on a photoemissive principle, the vidicon television camera tube is based on a conductivity principle, a circumstance which explains its name. 

Spectral photosensitivity is high and favorable for color imaging. Sensitivity in the green region is more than twice as large as that for conventional vidicon tubes. 

Oriented polymers will no longer show a symmetric scattering pattern. For such systems a two dimensional detector is necessary. A commercial data aquisition system (Westinghouse), based on a Vidicon tube, is shown in Fig. 32. The video signal... 

Fig. 32. Schematic diagram of the operation of a Vidicon tube used for X-ray diffraction studies (Westinghouse). The videosignal is stored on videotape (UMATIC)...

Photo-Electronic Imaging Devices 6.1 Vidicon-Tube Based Detectors ... 

The main components of a Vidicon tube based system are shown in Fig. 16. 

Since the photocathodes which are used in Vidicon tubes are sensitive to visible radiation only, some means of conversion of the X-ray photons in the keV-region to visible radiation has to be provided. This is achieved by installing a scintillator in front of the Vidicon. 

With modem Vidicon tubes the spatial resolution power of a detector system is predominantly determined by the optical properties of the scintillator. 

Modern vidicon tubes with an integrated amplifying system exist in the form of the Silicon-Intensifier-Tanget-Tube (SIT-Tube). The main structure of this family of devices is shown in Fig. 17. It consists of an image-intensifier section, followed by a... 

The two parameters of importance, concerning the performances of vidicon tube systems are the spatial resolution and the dynamic range. The spatial resolution is not at all equal to the spacing of the individual diodes in the mosaic. The read-out beam is already itself wider than this spacing in order to avoid adjustment problems with the positioning of the beam relative to the structure of the mosaic. 

The ultimate resolution that can be obtained with a Vidicon-tube system can best be seen from the manufacturers specification. The spatial resolution is expressed by the so called modulation-transfer function (MTF), which is measured by the projection of a test mask directly on the photocathode, with visible light. Of course, this test does not include the degradation by the phosphor screen in X-ray applications. 

Bearing in mind the overall dimensions of the largest and most expensive Vidicon tubes with 80 mm photocathode diameter, the disadvantage in synchrotron radiation work becomes evident. The focal spot of the synchrotron radiation beam is much larger than 80 pm, and so are the reflections in a diffraction pattern, if the entire intensity of the source is to be used. 

The Princeton Vidicon-tube system has been used successfully at EMBL as a detector for the high intensity reflection of a muscle diffraction pattern... 

For small angle scattering work and for diffuse patterns, with high intensities as encountered in polymer physics applications, vidicon tube systems are certainly a possibility. 

Although vidicon-tubes are commercial devices, it still takes a long way to turn them into an excellent X-ray detector. For accurate amplitude measurements, quite some effort has to be invested in the development and tests of the different components. 

A new type of imaging devices has been introduced a decade ago These devices consist of an array of photo-sensitive diodes, coupled to a CCD read-out system. CCD s are based upon the transfer of charge packets in a repetitive metal-oxid°-silicon (MOS) structure (see Fig. 20). The charges in the elements of a CCD can be photo-generated, e.g. by the absorption of X-rays in the substrate, and then shifted out electronically to a single output. In a way CCD s operate as the solid state selfscanning equivalent of a vidicon-tube. 

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