Television – Cathode-ray tube display excessive voltage control
Reexamination Certificate
1998-11-20
2001-11-06
Eisenzopf, Reinhard J. (Department: 2614)
Television
Cathode-ray tube display excessive voltage control
C348S377000, C348S378000, C348S379000, C348S380000, C348S381000, C348S382000, C345S111000, C345S182000, C345S173000, C345S212000, C315S383000, C315S403000, C315S368170
Reexamination Certificate
active
06313878
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to display products, such as monitors, screens, and projectors, and more particularly to an improved screen-saver for display products.
BACKGROUND OF THE INVENTION
Some form of display products is used in just about every imaginable field of human endeavor. Any application in which information of some form or another is to be conveyed will most probably use one or more display products to convey that information. Display products, which include screens, monitors, such as computer and video monitors, and projectors, are indispensable to engineering, scientific, educational, government, military, and entertainment endeavors.
A common problem with displays is that an image will burn into the display after the image has been static or unchanging for a long period of time. Cathode ray tube (CRT), plasma, and liquid crystal display (LCD) displays are well known examples of display products that are susceptible to the burn-in problem. Of course, the longer a static image is displayed, the greater the probability that burn-in will result. Burn-in of the image results in an objectionable pattern that becomes visible when the product display changes to another image. Burn-in of an image in expensive display products, such as costly video monitors and projectors, is of particular concern. For example, in cases where large numbers of video communications links are continuously monitored, it is common that one or more display products will brightly display the same, unchanging image, such as logos, test patterns, or color bars, for long periods of time.
The display burn-in problem has typically been addressed with so-called “screen-saver” software, especially in the realm of computer screens. Screen-saver software detects a lack of input from the user interface and, after a predetermined time, usually set by the user, the software will invoke screen-saving activity that prevents burning of the image in the display product. The use of such screen-saving software is well known in the field and is available both commercially and at no charge.
While the software screen-savers commonly used for inexpensive display products, such as computer monitors, operate to prevent burning of the image into the display, they by definition do not permit the image to been seen on the display product once invoked. There are many applications, particularly where expensive display products are used, where it is desirable for the image to be continuously displayed on a display product. High-end video monitors and screens, for instance, are used to display advertisements that do not change for long periods of time in high visibility areas like airports and shopping malls. Where advertisers pay top dollar in order to purchase such prime advertising locations, the advertising image must be continuously displayed. A display product in which a company logo has been burned into the display often must have its CRT replaced, even though the display product may otherwise be functioning properly. Or, consider a broadcast monitor used in a security office of a jail or a secured military environment that must display the image of a remote location under surveillance for indefinite periods of time. In all of these applications, the image must be shown indefinitely regardless of the possibility of image burn-in.
In light of the above discussion, it is clear that there exists a need in the art to be able to indefinitely display an image on a display product while preventing burn-in of the image.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to be able to indefinitely display a static image on a display product while preventing burn-in of the image into a screen of the display product.
Therefore, according to the present invention, a method and system automatically provides a screen-saver function to a display product that burn-in of an image displayed on a screen of the display product by automatically reducing the video gain, and therefore the contrast, of the image when a part of the image within a two-dimensional detection window has changed by less than a predetermined amount for a predetermined period of time. The contrast of the image is restored once the content of the detection window changes at least the predetermined amount. The screen-saver of the present invention allows the image to remain visible, yet reduces the possibility of burn-in of the image in the screen of the display product.
The method of the present invention adjusts of the contrast of the image within the detection window by performing the following: defining a size and a position of the detection window of the image, detecting when a predetermined amount of the image within the detection window has not changed for the predetermined period of time, and in response to the image being static, reducing the contrast of the entire image displayed on the display product screen.
This method may be implemented by first, second, or third embodiments of the present invention. According to the first embodiment of the invention, a sampling circuit receives channel signals, representative of the red, green, and blue component signals of the video signal provided to the display product, and first and second control signals generated by a timer and logic circuit. The sampling circuit monitors the channel signals and generates a sampling signal indicative of whether the predetermined amount of any of the channel signals has not changed for the predetermined period of time within the detection window. The timer and logic circuit receives the sampling signal, a horizontal sync signal, and a vertical sync signal and generates first and second control signals and an adjustment signal capable of reducing the contrast of the static image within the detection window when the predetermined amount of any of the channel signals has not changed for the predetermined period of time. A gain control element receives the channel signals and the adjustment signal generated by the timer and logic circuit and changes the gain of the channel signals if controlled to do so by the adjustment signal. The image represented by the channel signals is displayed on a screen of the display product with reduced contrast so long as the image remains unchanging by the predetermined amount. Once the image is no longer static, the adjustment signal causes the contrast of the image to return to the nominal, pre-static state. The second embodiment of the present invention operates in a similar manner as the first embodiment, but is simplified for a monochromatic video display and so only has one channel signal, rather than three RGB channel analog signals.
According to the third embodiment of the present invention, the gain of a static video signal displayed on a digital display device, such as an LCD or plasma display panel, is reduced. This embodiment works in similar fashion to the first embodiment except that instead of sampling an analog signal in a sampling window, a checksum algorithm a processing block is used to determine when the video signal has not changed by the predetermined amount for the predetermined period of time.
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Eisenzopf Reinhard J.
Larson Reneé Michelle
Natnael Paulos M.
Sony Corporation
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