Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1997-07-11
2001-01-16
Chang, Kent (Department: 2778)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S182000, C345S089000
Reexamination Certificate
active
06175355
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of modulating pixels of a display panel for forming a greyscale image on the display. More particularly, the invention relates to the field of dispersing over time a sequence for modulating each pixel of a display panel for forming a greyscale image on the display.
BACKGROUND OF THE INVENTION
A collection of pixels is modulated for displaying an image on a digital display, a pixel is either in an ‘on’ condition or in an ‘off’ condition. For example, the ‘on’ condition can represent white and the ‘off’ condition can represent black. To provide more information and realism in the image, it is generally desired to provide intermediate intensities or greyscale levels. Pulse width modulation (PWM) is a well known technique for achieving intermediate greyscale levels. According to PWM, the pixels are rapidly toggled a varying portion of the time between ‘on’ and ‘off’. The larger the percentage of time the pixel is ‘on’, the closer to white the pixel is displayed. Assuming the clock rate is sufficiently fast, a viewer's eye integrates the intensity of a toggled pixel to perceive grey rather than merely black or white. The intensity level for the pixel depends upon the relative durations of the ‘on’ state and the ‘off’ state. It is well understood that pulse-width modulation can also be applied to color systems for forming varying intensities and shades of color.
Digital display systems generally include a plurality of pixels arranged in an array of rows and columns. Conventionally, a row of image data to be displayed is loaded from a video memory into a shift register and then utilized to pulse-width modulate each pixel in a corresponding row of a display panel according to the data in the register. Modulation for each row of pixels is generally performed in a regular sequence beginning with a left-most pixel in the row and ending with a right-most pixel. Once the row is complete, image data for a next row of pixels is loaded into the register. According to prior art systems, this process repeats for each row in the display, thus, forming a complete frame. Once the frame is completed, the image is continually updated by repeating this process.
A drawback to this conventional display system is that because the pixels are modulated in a regular sequence and in the order in which they appear in the display, the updating process can induce false motion artifacts into the image. For example, lines can appear to move in the image or the image can appear to flicker, especially in the presence of fluorescent lighting systems.
What is needed is a technique for updating a digital display system with image data according to a pulse-width modulation technique that does not induce motion artifacts into the image.
SUMMARY OF THE INVENTION
The invention is a dispersion-based technique for modulating pixels of a digital display panel for forming an image on the display panel. The display panel includes a plurality of pixels arranged in rows and in columns. Each pixel has an associated pixel frame, which is a period of time during which the pixel is modulated to achieve an appropriate greyscale level for the pixel. Each pixel frame includes a plurality of sub-frames. During each of the sub-frames, the pixel is configured in an ‘on’ condition or in an ‘off’ condition according to a selected one of a plurality of predetermined greyscale sequences. Each PWM greyscale sequence corresponds to a greyscale level for the pixel frame. A display frame is formed when each pixel in the display is appropriately modulated according to an image to be displayed. The displayed image is continually updated by displaying a next display frame in a sequence of display frames.
Sequences for modulating the pixels are spatially and temporally dispersed in a non-regular sequence to reduce or eliminate motion artifacts introduced into the displayed image by the process of updating the image. This is accomplished by dividing the display panel into blocks of pixels. Each pixel block preferably includes sixteen pixels arranged in a four-by-four array. The greyscale sequences for pixels in a block are offset from one another by various numbers of sub-frames. This offset is termed pixel dispersion. The amount of pixel dispersion is preferably not related to an order in which the pixels are arranged in rows and columns within the blocks. The pixel blocks are grouped in four-by-four arrays of sixteen pixel blocks. Greyscale sequences for modulating the pixels in a block are offset from sequences for pixels in other blocks in the array by various numbers of sub-frames. This is termed block dispersion. The amount of block dispersion is preferably not related to an order in which the blocks are arranged in rows and columns in the array of blocks. Multiple arrays of blocks are updated in an identical manner to form a complete display panel.
REFERENCES:
patent: 4709995 (1987-12-01), Kuribayashi et al.
patent: 4747671 (1988-05-01), Takahashi et al.
patent: 5185602 (1993-02-01), Bassetti, Jr. et al.
patent: 5293159 (1994-03-01), Bassetti, Jr. et al.
patent: 5298915 (1994-03-01), Bassetti, Jr.
patent: 5404427 (1995-04-01), Cawley et al.
patent: 5455600 (1995-10-01), Friedman et al.
patent: 5469190 (1995-11-01), Masterson
patent: 5479188 (1995-12-01), Moriyama
patent: 5495346 (1996-02-01), Choi et al.
patent: 5508822 (1996-04-01), Ulichney et al.
patent: 5553200 (1996-09-01), Accad
patent: 5586203 (1996-12-01), Spaulding et al.
patent: 5619230 (1997-04-01), Edgar
patent: 5621825 (1997-04-01), Masaki et al.
patent: 5673065 (1997-09-01), DeLeeuw
patent: 5818419 (1998-10-01), Tajima et al.
patent: 5896122 (1999-04-01), MacDonald et al.
patent: 0 654 777 A1 (1995-05-01), None
Chang Kent
Limbach & Limbach L.L.P.
National Semiconductor Corporation
LandOfFree
Dispersion-based technique for modulating pixels of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dispersion-based technique for modulating pixels of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dispersion-based technique for modulating pixels of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2518770