Computer graphics processing and selective visual display system – Display driving control circuitry – Display power source
Reexamination Certificate
2000-11-27
2004-02-17
Awad, Amr (Department: 2675)
Computer graphics processing and selective visual display system
Display driving control circuitry
Display power source
C348S536000
Reexamination Certificate
active
06693628
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a device for monitoring the setting of the phase between the pixel clock rate of a graphics card and the sampling clock rate of a flat screen having an analog interface.
Flat screens having an analog interface have to be adapted to the graphics card of the connected computer. If the phase or sampling frequency are set incorrectly, the picture is fuzzy and exhibits interference.
Whereas the values for picture position, that is to say the right-left and top-bottom setting, and the sampling frequency can be defined as preset values for standard modes, this is not possible for the phase since the phase depends on the graphics card used and also on the video line.
A microprocessor is usually provided in flat screens according to the prior art, the microprocessor performing the general control of the flat screen. This microprocessor is configured in such a way that it can also identify the video mode set at the computer. If the mode has already been set at the factory or by the user, the flat screen is operated with the stored settings for picture position, sampling frequency and phase. By contrast, if the mode is one which has not yet been implemented in the microprocessor of the flat screen, then standard values are adopted for picture position, sampling frequency and phase. These standard values are not satisfactory in all cases.
The setting of the sampling clock rate and of the phase has a direct effect on the picture quality. An optimum sampling frequency is given when the sampling of all the pixels of a line, for example, of a video signal ensues in a stable or characteristic region of the pixels, for example in the center of each pixel. The data conversion yields optimum results in that case. The picture shown has no interference and is stable. In other words, the optimum sampling frequency is equal to the pixel frequency. If an incorrect sampling frequency is set, for example if the sampling clock rate is too fast in comparison with the pixel clock rate, the pixels are initially sampled in the permissible region, that is to say in the center between two edges, but the subsequent pixels are sampled more and more in the direction of an edge until even the region between two pixels is sampled, which obviously leads to an unsatisfactory picture quality. Incorrect samples are derived in the region where the pixels are not sampled in an optimum, characteristic region. The picture then exhibits a high degree of vertical interference. The greater the difference in frequency between the sampling clock rate and the pixel clock rate, the more regions with vertical interference are visible on the screen.
However, even in cases in which the sampling clock rate is identical to the pixel clock rate, the picture quality can suffer if the phase is not set correctly. The reason is that the sampling takes place in a pixel region which is not ideally suited to sampling, for example too close to the front or back edge of a pixel. This problem can be solved by the phase, that is to say the sampling instant, overall being shifted until the sampling takes place in a characteristic or permissible region of the pixels. If the phase is not set correctly, the picture quality on the entire screen is impaired by noise signals.
Many users are unaware of the relationship between sampling frequency and phase with respect to the picture quality. If the picture is fuzzy, a defect is assumed and after-sales service is enlisted. This leads to unnecessary costs. Indications in the manual or on the packaging of the screen are overlooked by many users. Moreover, some users do not know that every resolution which is used and is set with respect to a graphics card requires a dedicated adjustment. If the picture quality is unsatisfactory for the reasons mentioned above, then in the most favorable case the after-sales service or the hotline of the manufacturer is contacted, whereupon the user is informed of the adjustment to be made to the phase. In some cases, however, entirely satisfactory monitors are returned under warranty even though only the phase must be set correctly.
Published, Non-Prosecuted German Patent Application No. DE 39 14 249 A1 discloses a method for a clock recovery from an input signal generated with an unknown clock, in which the input signal is digitized with a comparison clock in different phase angles. From the profile of the phase angle (input signal to comparison clock), the difference between the clock frequency of the input signal and that of the comparison clock is determined and the frequency of the comparison clock is corrected accordingly.
Published, Non-Prosecuted German Patent Application No. DE 19 751 719 A1 describes a signal processing method for an analog picture signal. In this case, the analog picture signal originates from a computing unit in which the signal has been generated digitally in accordance with a graphics standard, such as e.g. EGA (enhanced graphics adapter), or VGA (video graphics array), and has subsequently been converted into analog form. The method subjects the analog picture signal to an analog/digital conversion with a first, chosen sampling frequency, after which the sampled picture is then investigated for picture disturbances in order to determine a corrected sampling frequency. Further measures relate to the determination of the optimum sampling phase and the determination of the exact position of the active picture relative to the horizontal and vertical synchronizing pulses.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device for monitoring the setting of the phase in flat screens which overcome the above-mentioned disadvantages of the heretofore-known methods and devices of this general type and which ensure that the required setting of the phase is performed whenever such a setting or adjusting is required.
With the foregoing and other objects in view there is provided, a method for monitoring, in a flat screen/graphics card/computer system, a setting of a phase between a pixel clock rate of a graphics card and a sampling clock rate of a flat screen having an analog interface, the method includes the steps of:
setting a flag if a phase of a flat screen has been set from a user-side;
interrogating the flag upon switching on the flat screen and/or switching a video mode at a computer and/or exchanging a graphics card and/or exchanging the computer; and
providing a display indication or initiating a setting of the phase if, during the interrogating step, it is ascertained that the flag is not set.
In other words, the method according to the invention is characterized in that a flag is set if the phase of the flat screen has been set by the user, in that the flag is interrogated upon a switch-on of the flat screen and/or upon a changeover of the video mode at the computer and/or an exchange of the graphics card and/or upon an exchange of the computer, and in that a display is provided or a setting of the phase is initiated if, during the interrogation, it is ascertained that the flag is not set. In other words, in addition to the settings which are already stored for each mode, a flag is also inserted which is set as soon as the phase has been set by the user. As a result, the user is not just informed by manuals and other accompanying material of the necessity of effecting phase setting, rather the user is, as it were, compelled to perform the phase setting whenever this is necessary.
If the flat screen is switched on and/or the video mode of the computer is changed over, the processor situated in the flat screen will interrogate the flag stored with respect to the present mode. If the flag is set, that is to say that the flat screen has already been set to the user's system, further operation of the system would proceed as usual. By contrast, if the flag has not yet been set, the flat screen shows a reaction, and a corresponding display takes place or automatic setting of the phase is initiated.
One advanta
Hase Paul Von
Soemantri Albertus
Awad Amr
Fujitsu Siemens Computers GmbH
Greenberg Laurence A.
Locher Ralph E.
Stemer Werner H.
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