Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-03
2001-11-06
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C315S169100
Reexamination Certificate
active
06313814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a drive circuit for a display panel, disposed with a common electrode and an individual electrode in each of a plurality of display cells arranged in a matrix configuration, for controlling gas discharges in each display cell by applying display pulses to the common electrode to perform display operations and by individually applying control voltages to individual electrodes to control the discharge in each display cell.
2. Description of the Related Art
Heretofore, display panels, such as plasma displays, are known for performing display operations by controlling the gas discharge of every display cell. These types of display panels are formed by disposing display cells into many matrix configurations for individually performing gas discharges.
Usually, the discharges are performed in pulses and the number of discharges in one frame in each display cell is controlled by luminance information regarding the respective display cell. For example, through the luminance data that is input, the number of discharges is set to a maximum number when the luminance of the display cell is at maximum luminance, and the number of discharges is set to 0 at minimum luminance. Furthermore, one set of three types of RGB display cells form one pixel, and the driving of each display cell is controlled by individual RGB luminance data for one pixel.
When actually performing a display operation in the display panel, it is necessary to perform various types of correction, such as adjustment of tint or gamma correction for the luminance data. These types of correction were performed for luminance data in the same manner as the correction of ordinary image data.
The data processing for these types of correction usually use the same calculations. However, if a setting is to be changed, the calculation must also be changed. This change is difficult to accomplish if an attempt is made to implement the circuit in hardware. On the other hand, if the circuit is implemented in software, a lot of time is required and the load on the processor increases.
SUMMARY OF THE INVENTION
The object of this invention is to provide a display control circuit for a display panel that has simple circuitry using a lookup table and that performs high-speed processing.
The drive circuit for a display panel concerned with in this invention comprises a sequence counter for counting the number of display pulses to be supplied to the common electrode, a lookup table for outputting an assumed luminance value corresponding to and addressed by the count value of the sequence counter, and a comparator for comparing the assumed luminance data from the lookup table with luminance data that is input. An output of the comparator controls a period of applying control voltage to the individual electrode of one display cell. According to this apparatus, discharges can be controlled to occur or not occur by a control voltage to the individual electrode corresponding to a display pulse. Therefore, controlling the time of applying the control voltage to the individual electrode enables the number of discharges to be controlled and enables the luminance in the display cell to be controlled. Rewriting the contents of the lookup table enables the time of applying the control voltage to the individual electrode to be made to correspond to luminance data that is input so that the number of discharges can be controlled. Namely, the display becomes brighter with a larger number of discharges, so that by handling the data in the lookup table, the number of discharges, which changes with single units (one step) of luminance data, can be varied when the luminance data is small or when it is large. Therefore, various types of corrections, such as gamma correction, can be performed using the contents of the lookup table, using the lookup table in this manner can speed up calculations and facilitate changes in characteristics. Having separate lookup tables to correspond with the RGB colors enables the individual brightness of the respective RGB color to be adjusted and also enables tint adjustments.
It is preferable for the above-mentioned lookup table to store differential data and to sequentially add the differential data that is output on the basis of the count value of the sequence counter so as to yield an assumed luminance value. This enables the same calculations to be performed with a narrower bit width of the lookup table.
It is also preferable to have a correction data table for storing correction data for each display cell so that the correction data corresponding to luminance data for each display cell that is input is read out from the correction data table for correction and the corrected luminance data is supplied to a comparator. This enables the adjustment of every display cell to be performed on the image data according to the correction data table, and the lookup table can store data for all display cells.
This invention is composed as described above and achieves the effects given below.
(i) The luminance of the display panel corresponding to the input luminance data is set by reading out the assumed luminance value from the lookup table according to the count value corresponding to the number of discharges, and by comparing this assumed luminance value with the luminance data that is input. Thus, the luminance in the display cell corresponding to the luminance data that is input can be changed by rewriting the contents of the lookup table.
(ii) The same calculations can be performed with a narrower bit width of the above-mentioned lookup table by storing differential data into the lookup table.
(iii) By providing a correction data table for storing correction data for each display cell and by performing correction for the luminance data of each display cell that is input, the adjustment of every display cell can be performed on the image data according to the correction data table, and for using the lookup table, it does not matter to which display cell the data corresponds.
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Arimoto Hironobu
Ito Atsushi
Hjerpe Richard
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Francis
Rothwell Figg Ernst & Manbeck
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