Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Patent
1993-02-22
1996-05-28
Hjerpe, Richard
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
348819, 348820, G09G 336
Patent
active
055216129
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device in a display unit of the LCD type for reducing time varying electric fields generated by the display unit.
2. Description of the Related Art
Display units have become more common in working localities and have recently been studied carefully with regard to different types of fields emitted therefrom. Different tests have shown that the emission has different effects on human tissue, but up to now the test results have been very contradictory.
One of the reasons for the results being contradictory and difficult to explain is probably that the picture of said field surrounding a display unit is very complex and comprises at least five different types of fields. Furthermore, in modern office premises there exists a high background level of emission from other electrical devices and installations.
A first type of field is the electrostatic field generating an electrostatic field between the surface of said display unit and any adjacent object having another potential, for instance a face.
Time varying electric fields or low frequency also surround a display unit. In frequently used cathode ray tubes said fields are comparatively weak, and therefore said fields have been considered harmless.
In a cathode ray tube which is included in the most common types of display units, a low frequency magnetic field is generated in the magnetic coils controlling the electron beam. It is very uncertain how the human being is affected by said field.
When the electron beam in a cathode ray tube hits the display surface an emission of radiation X-ray (s c soft emission) is generated. However, the major part thereof is stopped by the glass of the display unit.
Together with the visible light emitted from a display unit, a minor part of ultra-violet light is also emitted. Said ultra-violet light has more energy than the visible light.
Finally there is transmitted from the oscillator of the computer also radio frequency emissions, which all lower by at least a factor of 1000 than the present limit values.
In display units including cathode ray tubes it is previously known to cover the casing of the display unit with a conducting layer, and the front of the display unit with a transparent layer, the conducting ability thereof being such that higher electrical fields existing in these types of display units are attenuated almost completely around said unit. However, the weaker electrical fields, i.e., the fields having a strength of approximately 100 V/m, will remain to some extent.
SUMMARY OF THE INVENTION
In the type of display unit in accordance with the present invention, i.e., LCD (Liquid Crystal Display) or similar display units having corresponding electrical and magnetic properties, the problem of transmitting emission was not previously considered because there exist only time varying electrical fields, and possibly also radio frequency emissions from an associated computer.
An object of the present invention is to provide a method in a display unit of the LCD type according to which weaker electric fields are attenuated to a level below the background level. Also, a device for carrying out said method is provided.
Said object has been achieved by the invention having the characteristics hereinafter described.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail by means of embodiments, reference being made to the accompanying drawings, in which
FIG. 1 is a side elevational view of a display unit for carrying out the method according to the invention, and
FIG. 2 is a perspective view of the display unit of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1 there is shown a display unit 10 of the LCD type. Said display unit 10 includes a display means 13 and a back section 14 protecting said display means 13. Said display means 13 is of a conventional type and has a display side 11 and a backside 12, and also includes the required driver circuits (not shown). A
REFERENCES:
patent: 4246613 (1981-01-01), Choder et al.
patent: 4663670 (1987-05-01), Ito et al.
patent: 4748546 (1988-05-01), Ukrainsky
patent: 4853791 (1989-08-01), Ginther, Jr.
patent: 5139850 (1992-08-01), Clarke et al.
Hjerpe Richard
Luu Matthew
Multio Products Scandinavia AB
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