Construction and operation of vacuum fluorescent display

Many devices are equipped with self-luminous displays, display units whose information is dynamically changeable. Your lighting is not generated by light bulbs that are behind a static image mask. The luminous phenomena of these displays are based on luminescence and fluorescence.
The generic term for luminous phenomena is the luminescence. Is a light emission is carried out at normal ambient temperature. It is therefore also known as cold lights. In fluorescence, the light emitting ends almost immediately after the end of stimulation. In contrast, it comes with the phosphorescence to a more or less long afterglow.

The luminous effect of the fluorescence can be observed in various materials according to light. The name refers to fluorescence of the mineral fluorite, where this property was first observed. Immediately after excitation by light, X-rays or electron beams enter the appropriate materials in a portion of the absorbed energy as electromagnetic radiation than visible light again.

As the cathode ray tube CRT of a television set and the vacuum fluorescent display VFD has a heating wire. He sends out as the cathode of the CRT thermally excited electrons. The temperature of the wire is also called filaments at 650 ° C. The electrons are accelerated in an electric field and then to make a light emitting layer, which is composed of different chemical salts. The impact energy of the electrons excited to the chemical compounds to emit light.

Unlike CRT each pixel is electrically actuated with vacuum fluorescent display. This is located above a level of the pixel grid electrode. Through this control grid, the electrons are accelerated toward the phosphor layer or kept away from her. The phosphor layer is connected as anode. If a light pixel, this anode is driven positive. The corresponding control grid element receives a less negative potential, so that a part of the electrons can fly through.



The grid potential is sufficiently negative relative to the reference potential of the filament, no electrons can pass through, and the pixel is dark. It is also the possibility the anode negative and sufficient to load the grid positive, the electrons flow from across the grid and the pixel is also dark. The following figure outlines increases the internal structure of a VFD.



The displays are suitable for static and dynamic control. For static control, the anode remains positively charged, as the image segment is lit. In the dynamic control, the pixels having a high switching frequency are controlled cyclically. At high switching frequency is slow enough our eyes and we see the display flicker and quiet. The synchronized control offers the advantage of a brightness control. The following figure shows the spatial arrangement of the main components of a vacuum fluorescent display.



Vacuum fluorescent displays emit monochromatic light. Depending on the fluorescent colors of orange can be used to represent blue. Other colors are possible by incorporating additional color filters in the display. For moving color images, film or video, VFDs are not suitable. They are found in alphanumeric display units of measurement devices in the consumer electronics and appliances as large matrix displays with solid symbols.

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