Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Patent
1991-03-11
1994-09-13
Weldon, Ulysses
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
345147, G09G 336
Patent
active
053472934
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to display devices for motor vehicles and, more particularly, to a Liquid Crystal Display (LCD) for vehicular use in which either positive or negative contrast is used, depending upon ambient lighting conditions.
In known LCD display devices, the legibility of the display at different degrees of brightness in the surroundings in front of the display is kept as constant as possible, in that the brightness of the surroundings is measured by a photo-electric detector, and the illumination of the display device is made to follow by means of suitably dosed direct or indirect lighting of the display (EP-A3-011 55 75, Ziegler and Knoll, assigned to the assignee of the present invention). It is also known that the brightness of the display can additionally be controlled in dependence on the brightness in front of the vehicle in order thus to take into account the state of adaptation of the driver's eyes, which is mainly determined by the brightness in the driver's field of vision. The legibility of the displays however also depends on whether the information to be displayed is represented in positive contrast or in negative contrast. This applies particularly for graphic-capable transflective dot matrix LCDs, on which information can be represented in the form of different symbols, figures, or numerical values and/or letters or words. In the case of a display in positive contrast where dark symbols appear on a bright background, the legibility is good in daylight, while at night, due to the back-lighting of the LCD, the eye must first adjust to the bright surroundings, which extends the reading period. With bright back lighting, there is the danger of dazzling the driver, and with weak back lighting, the legibility is reduced by too little contrast. In the case of negative contrast, i.e. with bright symbols on a dark background, the display is easily legible in the dark, as here the eye need not adapt to the background brightness. However, in that case there is poor legibility in daylight, as shadows are formed by the illumination on the background of the display, which shadows limit the symbols to be shown. There occurs a so-called dazzle effect of the liquid crystal display.
In the present solution of the problem, the effort is made to optimize the contrast of the display for graphic-capable transflective dot matrix LCDs as far as possible in dependence respectively on the light conditions in the vehicle or in front of and behind the vehicle as the case may be.
The Invention
The display device according to the invention has the advantage that, due to the contrast switch-over on the one hand a high contrast of the display can be achieved during the day, in that when illuminated, the symbols appear dark on a light background, and in that on the other hand conversely in darkness the surroundings of the symbols are dark, so that the eye does not have to adapt to bright surroundings. Due to this solution, the legibility of the display is no longer adversely affected by light conditions outside or by back-lighting. It is to be regarded as a further advantage that the contrast switch-over is also independent of whether the LCD was made for positive or negative contrast. One can simply invert the activation of the individual matrix dots of the LCD without altering the LCD, and thereby obtain a contrast switch-over. In the case of an LCD produced with positive contrast, the non-activated matrix dots are bright, i.e. translucent and become dark by the contrast switch-over by applying a voltage, i.e. they are switched to block, whereas LCDs produced with negative contrast are dark when the matrix dots are not activated, and in the case of contrast switch-over are switched to be bright by applying a voltage. In this solution it is further advantageous that the necessary light power for the back-lighting of the transflective dot matrix LCDs can be reduced.
The invention features a particularly effective and hence advantageous contrast switch-over for the LCD, wh
REFERENCES:
patent: 4104627 (1978-08-01), Thuler
patent: 4838661 (1989-06-01), McKee et al.
patent: 4865425 (1989-09-01), Kobayashi et al.
patent: 4965574 (1990-10-01), Fukushima et al.
Automotive Engineering, "West Germany", Jan., 1986, pp. 32-39.
Patent Abstracts of Japan, vol. 9, No. 18 (M-353).
Ereth Walter
Wiedemann Werner
Chow Doon
Robert & Bosch GmbH
Weldon Ulysses
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