Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-08-31
2001-03-13
Hjerpe, Richard A. (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S061000, C345S067000, C345S068000
Reexamination Certificate
active
06201518
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a Plasma Display Panel (PDP) and method of operating the display panel. More specifically, the present invention is related to a continuous-drive high-frequency AC Plasma Display Panel and a method of addressing the display panel.
BACKGROUND OF THE INVENTION
Plasma Display Panels (PDPs) offer promising technology for implementing large, flat video screens. A typical PDP may be formed by enclosing a gas, for example, a mixture of helium and neon between a transparent front panel and a back panel. Electrodes may be routed on the front panel and on the back panel and phosphors may be printed on either the front panel or the back panel. The electrodes are used to ionize the gas, forming a plasma which emits ultraviolet radiation. The ultraviolet radiation, in turn, causes the phosphors to emit visible light. Color displays are made by forming adjacent columns having red, green and blue phosphors, respectively.
A common type of PDP is the three-electrode pulsed Alternating Current (AC) device. In this configuration, each display row includes two parallel row electrodes, for example, on the inside surface of the back panel and each column includes one column electrode, for example, on the inside surface of the front panel. The row electrodes on the back panel may be covered with a dielectric layer so that no direct current (DC) flows between the electrodes when the plasma is ignited. The electrodes on the front panel may also be covered with a dielectric layer.
In order to generate gray-scale values, each field interval of a video image may be divided into multiple sub-field intervals. Each sub-field interval includes a writing phase and an illumination phase. The illumination phases of the different sub-fields of an image field have respective durations. These durations are programmed such that each individual pixel position on the screen may be illuminated for an amount of time proportional to the binary value of an image picture element.
Briefly, an AC plasma display operates as follows. Operation is divided into two phases or states, the writing phase (writing state) and the illumination phase (sustain state). In the writing phase of a given sub-field, data values are written into each pixel position of the display device one row at a time. The rows are selected one at a time by successively applying a select potential to each row. At the same time, voltages are applied to the column electrodes to establish a relatively high potential between the column electrodes and the selected row electrode for pixels that are to be illuminated during the sustain state of the sub-field interval, and to establish a relatively low potential between the column electrodes and the selected row electrode for pixels that are not to be illuminated during the sustain state. The relatively high potential causes an electric charge to be deposited between the front and back panels, on the inside walls of the dielectric layers, at the respective pixel position. This electric charge is commonly known as a “wall charge.”
In other words, a pixel which will be bright has a wall charge written into it, and thus receives “ON” data. A pixel which will be dark does not have a wall charge written into it, and thus receives “OFF” data. In some implementations, the writing phase includes a preliminary erase step in which wall charges from the previous frame of data are erased.
After the wall charge has been written for each row of the display, the sustain state of the sub-field begins. During the sustain state a predetermined potential is applied in pulses between the two parallel row electrodes across the entire display. If a pixel position has a wall charge (“ON” data), the predetermined potential ignites the plasma at that pixel position. If the pixel position does not have a wall charge (“OFF” data), the plasma does not ignite.
In conventional PDPs, illumination is prohibited in the writing phase while rows are being written. If illumination is attempted while rows are being written, crosstalk may occur as data voltages on the column electrodes may interfere with the discharge in unselected rows. Thus the display may be relatively dimmer because it is not illuminated while data values are written into the display. In some conventional displays, about 50% of the display time is taken up by the writing phase.
Further, in conventional PDPs, alternating pulses are applied to row electrodes during the illumination phase. Hence, the display generates light as narrow impulses at pulse edges, and each light impulse is allowed to decay fully in order to completely invert the wall charge in preparation for the next pulse. Therefore, the display is dimmer than it would be if light were generated continuously.
Moreover, in a conventional PDP, the use of pulses to write and illuminate the display causes the driver electronics to dissipatively charge and discharge the column and row electrodes. Hence, the power dissipation in conventional PDPs is inefficient.
SUMMARY OF THE INVENTION
The present invention is embodied in a plasma display apparatus having a plurality of pixels. Each pixel has an ON state and an OFF state. Each pixel of the display apparatus comprises: a top substrate; a bottom substrate disposed parallel to the top substrate; a first select electrode provided on one of the top substrate and the bottom substrate; a second select electrode, adjacent to the first select electrode, provided on the same substrate; a data electrode provided on the opposite substrate. A signal source supplies an AC signal having either a first phase or a second phase.
A first switch is connected to the AC signal source and to the first select electrode to selectively apply the first phase or the second phase of the AC signal source to the first select electrode. A second switch is connected to the AC signal source and to the second select electrode to selectively apply the first phase or the second phase of the AC signal source to the second select electrode. A third switch is connected to the AC signal source and to the data electrode to selectively apply the first phase or the second phase of the AC signal source to the data electrode.
When the same phase is applied to both the first and second select electrodes, the phase of the AC signal source applied to the data electrode determines the state of the pixel; and when the phase applied to the first select electrode differs from the phase applied to the second select electrode, the state of the pixel remains unchanged.
According to one aspect of the invention, each pixel of the plurality of pixels further comprises a gas capsule, formed by a transparent tube or a transparent sphere, interposed between the top substrate and the bottom substrate and aligned with the first select electrode and the second select electrode.
According to another aspect of the invention, a first dielectric layer is formed on the top substrate, and a second, thicker, dielectric layer is formed on the bottom substrate.
According to yet another aspect of the invention, select electrodes are shared between pixels, so that the second select electrode of one pixel is the first select electrode of another successive pixel.
According to another aspect of the invention, an ON state is written to a selected pixel of the plurality of pixels by applying the second phase to the data electrode if the first phase is applied to both the first select electrode and the second select electrode. An ON state is also written to a selected pixel by applying the first phase to the data electrode if the second phase is applied to both the first select electrode and the second select electrode. An OFF state is written to the selected pixel by applying the first phase to the data electrode if the first phase is applied to both the first select electrode and the second select electrode. An OFF state is also written to the selected pixel by applying the second phase to the data electrode if the second phase is applied to both the first select electrode and the second select
Kane Michael Gillis
Roach William Ronald
Bowers Benjamin D.
Burke William J.
Hjerpe Richard A.
Sarnoff Corporation
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