Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
2001-02-28
2003-04-08
Wu, Xiao (Department: 2674)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C702S066000
Reexamination Certificate
active
06545681
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to methods of graphically displaying digital data and, more particularly, to a method of representing a continuous stream containing a predetermined number of digital values, on a display area containing a lower, predetermined number of graphical display elements.
Graphical display of a stream of digital data has numerous practical uses in various diagnostic and analytic applications. One such useful application is, for example, the graphical display of digital samples representing a digitized electrical signal. In some cases, the display of a digitized signal will be used to examine the performance of the instrument which generated the electrical signal, for example, to evaluate the stability of an electrical generator. In other cases, an electrical signal may be generated as an analog electrical imitation of other natural phenomena, such as acoustic oscillation, temperature, pressure, acceleration, or physical position, among others. In the latter cases, display of the electrical signal will be used as a tool for observing and examining the behavior of the physical phenomenon represented by the electrical signal.
Present day techniques of displaying a digitized electrical signal, for example, using a Digital Storage Oscilloscope (“DSO”), typically include: converting an electrical signal of interest into a stream of digital samples or “readings” using an analog to digital converter (“ADC”); sending the digital stream to a digital computing device, for example, a computer or a microprocessor; processing the digital data with the digital computing device, in order to prepare the digital data for display; and displaying the processed data on a graphical display device, for example, a cathode-ray tube (“CRT”), a dot-matrix liquid crystal display (“LCD”) or any other type of display known in the art.
A contemporary DSO typically includes an ADC capable of sampling electrical signals at sampling rates of as high as millions (MHz) or even billions (GHz) of readings per second. The increase in sampling rate capabilities is highly advantageous, since a greater sampling rate means greater accuracy in the digital representation of a sampled signal. As opposed to high sampling rates of existing ADCs, present day display devices are still confined to much lower resolutions of display. A standard display device, such as a personal computer monitor, will usually accommodate a maximum number of graphical display elements, namely “pixels”, on the order of only a few hundreds by a few hundreds (e.g. 800 by 600 pixels, 1024 by 768 pixels, etc.).
Thus, it is common practice in present day techniques for displaying digitized signals, that the number of digital readings produced by an ADC exceeds by far the number of pixels available for displaying the same. In order to display a high number of digital readings on a display which is able to accommodate a much lower number of pixels, every pixel must represent more than one digital reading at a given time. Several known methods attempt to cope with the problem of displaying a high number of digital readings on a display including a lower number of pixels.
U.S. Pat. No. 5,684,507 to Rasnake et al. discloses a method of displaying continuously acquired data on a fixed length display. According to teachings of this patent an ADC receives an input electrical signal and produces a continuous stream of “measurement data” (i.e. digital readings). The stream is continuously sent to a digital computing device. The digital computing device continuously converts incoming readings into pixel information in such a manner that every pixel plotted on the display represents a predetermined number of readings. Pixel information is continuously plotted on the display area, for example, from the leftmost pixel column to the rightmost pixel column. As the last available pixel (e.g. the rightmost pixel) on the display is reached, all the pixel information currently displayed on the display area, is then compressed into a fraction of the display area (e.g. into the left half of the display area), thus continuously providing room for newly arriving pixel information to be plotted on the remaining fraction of the display area.
These teachings include several inherent disadvantages. First, the teachings of Rasnake result in a disproportional, non-linear distribution of readings per pixel throughout the display area. Each time data is compressed into a fraction of the display area, compressed data will appear on a smaller scale than newly plotted data. For example, let us consider an example in which the compression ratio is 2 to 1, meaning that the total display area is repeatedly compressed into a half of the display area (for example, the left half). In such a case, after the first compression operation is completed, the compressed pixel information will appear on the left half of the display area on a scale of 2 to 1. In other words, every pixel column on the left half of the display area will represent pixel information which, prior to the compression, was represented by two pixels. The problem is that, according to the Rasnake method, newly arriving pixel information will still be plotted on the display area on a scale of 1 to 1. Consequently, data displayed on the compressed fraction (i.e. the left half of the display area) will appear on a scale of 2 to 1, whilst at the same time data displayed on the remaining fraction (i.e. the right half of the display data) will appear on a scale of 1 to 1. This problem is inherent to the Rasnake method, and therefore will persist regardless of which compression ratio is chosen and regardless of how many compressions were made (provided that at least one compression was made).
Second, the teachings of Rasnake do not guarantee that when the plotting process is ended, all available pixels on the display area will be utilized. According to these teachings, newly arriving pixel information is plotted on the display area until no more pixels on the display are available, at which point the displayed data is compressed into a fraction of the display area. However, if the process is halted exactly after a compression was made, then the remaining portion of the display area (i.e. the total display area excluding the fraction into which data was compressed) will remain empty and unused. Similarly, if the plotting process is ended after some pixel information was already plotted on the display, but before the last available pixel is reached, then again some pixel columns on the display area will remain unused. Only if the process is stopped exactly when the last available pixel is plotted (a statistically rare case indeed), will the complete display area be utilized. Even if such a rare case occurs, there will still be the problem of disproportionality between the compressed fraction and the remaining portion of the display area, as explained heretofore. Therefore these teachings are unsuitable for displaying a batch of digital data, that is, displaying a stream of digital data in cases where the number of digital values contained in the stream is known in advance.
Third, the teachings of Rasnake do not enable the user to choose, in advance, a desired ratio of readings per pixel. Instead, pixel information representing digital readings is repeatedly compressed, so that the number of readings represented by a single pixel in the compressed fraction of the display increases with every compression. As a result, after a certain number of compressions, any further compression will assign too many readings per one pixel, to the extent that such a display of the readings will no longer be meaningful or useful for the user. According to the method, the user has no ability to determine, in advance, a target ratio of readings per pixel, after which no further compressions will be made.
Fourth, the teachings of Rasnake require dedicated hardware, namely a special microprocessor, containing special firmware. Such a solution is expensive, inflexible and difficult to achieve. Impleme
Eitan Alon
Passi Alex
Passi Garri
Friedman Mark M.
Medson Ltd.
Wu Xiao
LandOfFree
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