GB2389730A

GB2389730A - Display with automatic brightness control

Info

Publication number: GB2389730A
Application number: GB0213753A
Authority: GB
Inventors: Yu-I Kuan
Original assignee: Mitac International Corp
Current assignee: Mitac International Corp
Priority date: 2002-06-14
Filing date: 2002-06-14
Publication date: 2003-12-17
Also published as: GB0213753D0; DE20209901U1

Abstract

A display monitor incorporates a photo sensor (10) arranged to detect the brightness of ambient light conditions about the monitor. The response of the sensor is output to a control device (12) which converts the photo sensor output to a brightness control signal. The brightness control signal is supplied to the CRT display circuit (18) to adjust the display brightness in accordance with surrounding ambient light conditions. The sensor may be a photoconductive or photovoltaic element. The display may also include a switch to control brightness via touch control and a digital display.

Description

AUTO BRIGIlllFaul= a.

The invention relates to a display and, in particular, to an auto brightness adjusting display. Monitors have become part of our daily life. They may be the monitors for the input;toutput of personal computers or terminals of workstations. Normally, a brightness adjuster is provided on the monitor to change the brightness of the display. When the display and its user are in a brighter environment, e.g. subject to a stony light source, the user has to manually adjust the monitor to a larger brightness. On the hand, if the environment is too dark, then he or she has to change to a lowa brightness mode, in order not to damage the eyes.

If the monitor and the user are in an environment with changing brightness, it becomes tedious tO adjust die brightness intermittently or may make the user's eyes tired soon.

In view of the foregoing, it is then an objective of the invention to provide an auto brightness adjusting display to address the many problems in the prior art

According to the invention there is provided an auto brightness adjusting display compnslng: a photo sensor, which detects the brightness in front of the display to generate a corresponding physical quantity; an auto photo control device, which converts the physical quantity into a brightness control signal; an unage amplification device, which receives the brightness control signal and a plurality of first image signals and amplifies the plurality of first image signals to generate a plurality of corresponding second image signals; a high-voltage amplification device, which amplifies the plurality of second image signals to generate a plurality of corresponding third image signals; and a CRT (Cathode Ray Tube), which receives the plurality of third image signals to generate an image on its screen.

The auto brightness adjusting display of at least preferred embodiments includes a photoconductive element to detect and monitor the brightness in front of the display, thus producing an induced resistance. This resistance value is converted by a DC gain amplifier into a brightness control signal. An image amplifier is supplied with the brightness control signal and several first image signals (e.g. ROB image signals) and amplifies the first image signals to produce the corresponding second image signals. A high-voltage amplification circuit is then used to amplify the second image signals to generate the corresponding third image signals. Finally, a CRT (Cathode Ray Tube) takes the third image signals to produce an image on the CRT screen.

Viewed from another aspect the invention provides an auto brightness adjusting monitor comprising: a photoconductive element, which detects the brightness in front of the monitor I to generate a corresponding resistance value; a DC gain amplifier, which converts the resistance value into a brightness control signal; an image amplifier, which receives the brightness control signal and a plurality of first image signals and amplifies the plurality of first image signals to generate a plurality of corresponding second image signals; a high-voltage amplification circuit, which amplifies the plurality of second unage signals to generate a plurality of corresponding third image signals; and a CRT (Cathode Ray Tube), which receives the plurality of third image signals to generate an image on its screen.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which.

FIG. I is a functional block diagram of a first example embodiment of the invention; FIG. 2A shows Be relation between the sensitivity of a CdS element and the light wavelength; FIG. 2B shows the relation between the resistance of the CdS element and the brightness on a logarithmic scale;

FIG. 3 shows the DC gain amplifier in the embodiment; and FIG. 4 is a fimctional block diagram ot a second example embodiment of the invention.

With reference to FIG. 1, the photo sensor 10 is installed in front of the display 18 for detecting the brightness in front of the monitor to generate a corresponding physical quantity. This photo sensor 10 is a cadmium sulphide (CdS) photoconductive element circuit. The photoconductive element is governed by the photoconductive effect, which says that when a semiconductor material is shined with light electronhole pairs are produced a., charge carriers to increase the conductivity of the material (i.e. the resistance reduces) in order to detect visible or infrared light. The CdS elements are mainly used for visible light detection. The relation of its sensitivity to different optical wavelengths is shown in FIG. 2A. From the CdS element resistance versus brightness relation shown in FIG. 2B, we see that the resistance is lower for intense light while higher for dim light.

On the other hand, the photo sensor 10 can be a photovoltaic element circuit such as a phototransistor. According to the photovoltaic effect, the photovoltaic element generates an induced voltage or current when electron-hole pairs are at or close to the pn junction, due to the internal electric field of the semiconductor. For example, the currents at the drain and

base of a phototransistor are amplified by the emitter.

The physical quantity measured by the photo sensor 10 is converted by the auto photo control device 12 into a brightness control signal. FIG. 3 shows such an embodiment with a DC gain amplifier as the auto photo control device 12. This DC gain amplifier includes a non-reverse operating amplifier 32. The two pins of the photo sensor I O are connected to the input end (+) and the ground end ofthe non-revere operating amplifier. The variable resistor 30 is the brightness adjuster of a conventional monitor. The intermediate adjustment end of the variable resistor 30 is also connected to the non-reverse input end (+).

Afterwards, an image amplification device 14 (such as a nonnal image amplification circuit) receives the brightness control signal from the auto photo control device 12 and several first image signals 140 (e.g. RGB image signals). The image amplification device 14 amplifies the first image signals 140 to generate corresponding second image signals 142.

The brightness control signal enters the contrast input end of the image amplification device 14 to control the output brightness of the images. The voltages of normal first image signals are about 1V whereas those of normal second image signals 142 are about 6V.

The second image signals 142 are then amplified by a high-voltage amplification device 16 to generate corresponding third image signals 160, with voltage values being about 60V.

The third image signals 160 are transmitted to a CRT (Cathode Ray Tube) 18 to generate an image on the screen of the CRT 18. As shown in FIG. I, the block diagram includes a usual horizontal bias circuit 17, a vertical bias circuit 19 and a power circuit 15 supplying power to the horizontal bias circuit 17, the vertical bias circuit 19, and the image amplification device i 14. With reference to FIG. 4, the photo sensor 40, the auto photo control device 42, the image amplification device 44, the high-voltage amplification device 46, the CRT 48, the horizontal bias circuit 47, the vertical bias circuit 49, and the power circuit 45 have the same functions and action principles as the previous embodiment. The difference from the former one is that this embodiment filer includes a no-stroke switch 50, which produces an electric signal to a central processing device 54 by touch control and digital display. The central processing device 54 also controls the horizontal bias circuit 47 and the vertical bias l circuit 49. The central processing device 54 generates a digital voltage representing its brightness according to the adjustment of the no-stroke switch 50 and sends the digital voltage value to a D/A (Digital-to-Analog) converter 52, converting the digital voltage into an analog voltage to be sent to the auto photo control device 42. One advantage of using the no-stroke switch 50 is that the auto control can be used with the touch-control no-stroke switch 50. This does not only allow the user to manually adjust the brightness according to the need, but also uses the no-stroke switch 50 and the central processing device 54 to automatically set the brightness to a default value each time the machine is turned on.

Therefore, the invention also inherits the advantage of the prior art.

The invention being thus described, it will be obvious that Me same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. An auto brightness adjusting display comprising: a photo sensor, which detects the brightness in front of the display to generate a 5 corresponding physical quantifier; an auto photo control device, which converts the physical quantity into a brightness control signal; an image amplification device, which receives the brightness control signal and a plurality of first image signals and amplifies the plurality of first image signals 10 to generate a plurality of corresponding second image signals; a high-voltage amplification device, which amplifies the plurality of second image signals to generate a plurality of corresponding Bird image sisals; and a CRT (Cathode Ray Tube), which receives the plurality of third image signals to generate an image on its screen.

15 2. The display of claim 1 being a monitor.

3. The display of claims I and 2, wherein the photo sensor includes a photoconductive element.

4. The display of claim 37 wherein the photoconductive element includes a CdS (cadmium sulphide) device.

20 5. The display of claim 4, wherein the physical quantity is a resistance value which decreases at strong light while increases at weak light.

6. The display of any one of claims I and 2, wherein the photo sensor includes a photovoltaic element

7. The display of claim 6, wherein the photovoltaic element includes a phototransistor.

8. The display of claim 7, wherein the physical quantity is a voltage value.

9. The display of claim 7, wherein the physical quantity is a current value.

1 O. The display of any one of the preceding claims, wherein the auto photo 5 control device includes a DC gain amplifier.

I I. The display of claim 10, wherein the DC gain amplifier includes a non-reverse operating amplifier and the two pins of the photo sensor are connected between the non-

reverse input end and ground end of the non-reverse operating amplifier.

12. The display of claim I 1 further including a variable resistor, whose intermediate 10 adjustment pin is connected to the pop-reverse input end.

13. The display ot any one of the preceding claims, wherein the brightness control signal is transmitted to a contrast input end of the image amplification device.

14. The display of any one of the preceding claims, wherein the voltage values of the first image signals are about I V. 15 15. The display of claim 14, wherein the voltage values of the second image signals are about 6V.

16. The display of claim 15, wherein the voltage values of the third image signals are about 60V.

17. The display of any one of the preceding claims, further including a no 20 stroke switch, which controls the display brightness of the display by touch control and digital display.

18. The display of claim 17 further comprising a central processing device, which produces a digital voltage value representing the brightness according to the no-

stroke switch adjustment.

19. The display of claim 18 further comprising a D/A (Digital-to-Analog) converter, which converts the digital voltage value to an analog voltage value to be sent to the auto; photo control device.

20. The display of any one of the preceding claims, wherein the photo 5 sensor is installed at the front end of the display.

21. An auto brightness adjusting monitor comprising: a photoconductive element, which detects the brightness in front of the monitor to generate a corresponding resistance value; a DC gain amplifier, which converts the resistance value into a brightness control I O signal; an image amplifier, which receives the brightness control signal and a plurality of first image signals and amplifies the plurality of first image signals to generate a plurality of corresponding second image signals; a highvoltage amplification circuit, which amplifies the plurality of second 15 image signals to generate a plurality of corresponding third image signals; and a CRT (Cathode Ray Tube), which receives the plurality ofthird image signals to generate an image on its screen.

22. The monitor of claim 21, wherein the photoconductive element includes a CdS (cadrniurn sulphide) device.

20 23. The monitor of claim 22, wherein the resistance decreases at strong light while increases at weak light.

24. The monitor of any one of claims 21 to 23, wherein the DC gain amplifier includes a non-reverse operating amplifier and the two pins of the photovoltaic element are connected between the

non-reverse input end and ground end of the non-reverse operating amplifier.

r 25. The monitor of claim 24 archer including a variable resistor, whose intermediate adjustment pin is connected to Me non-reverse input end.

26. The monitor of any one of claims 21 to 25, wherein the brightness control signal is transmitted to a contrast input end of the image amplification device.

27. The monitor of any one of claims 21 to 26, wherein the voltage values of the first image signals are about I V. 28. The monitor of claim 27, wherein the voltage values ofthe second image signals are about 6V.

I 0 29. The monitor of claim 28, wherein the voltage values of the third image signals are about 60V.

30. The monitor of any one of claims 21 to 29 further including a nostroke switch, which controls the display brightness of the display by touch control and digital display.

31. The monitor of claim 30 fiercer comprising a central processing device, which 15 produces a digital voltage value representing the brightness according to the no-stroke switch adjustment. 32. The monitor of claim 31 further comprising a D/A (Digital-to-Analog) converter, which converts the digital voltage value to an analog voltage value to be sent to the auto photo control device.

20 33. The monitor of any one of claims 21 to 32, wherein the photovoltaic element is installed at the front end of the monitor.

34. An auto brightness adjusting display substantially as hereinbefore described with reference to the Figures 1, 2A, 2B and 3 of the accompanying drawings. 35. An auto brightness adjusting monitor substantially as hereinbefore described with reference to Figures 2A, 2B, 3 and 4 of the accompanying drawings.