Display-integrated type tablet device
First Claim
1. A display-integrated type tablet device including a display panel which has a display material interposed between segment electrodes and common electrodes crossing each other at right angles and is driven by a duty ratio control type drive method, a detection pen having at a tip of the detection pen an electrode electrostatically coupled with the segment electrodes and the common electrodes of the display panel, a segment electrode drive circuit for driving the segment electrodes, a common electrode drive circuit for driving the common electrodes, a display control circuit for displaying an image on the display panel by controlling the segment electrode drive circuit and the common electrode drive circuit in a period of displaying the image, a detection control circuit for controlling the segment electrode drive circuit to sequentially scan the segment electrodes of the display panel by applying a scanning voltage successively to the segment electrodes and controlling the common electrode drive circuit to sequentially scan the common electrodes by applying a scanning voltage successively to the common electrodes in a coordinate detection period, an x-coordinate detection circuit for detecting an x-coordinate value designated on the display panel by the tip of the detection pen according to an output signal generating timing of the detection pen and a scanning timing of the segment electrodes, and a y-coordinate detection circuit for detecting a y-coordinate value designated on the display panel by the tip of the detection pen according to an output signal generating timing of the detection pen and a scanning timing of the common electrodes,the display-integrated type tablet device comprising a correction voltage generation means for generating a correction voltage for canceling a voltage induced at an electrode closer to the detection pen and placed in an upper position attributed to a scanning voltage applied to an electrode farther to the detection pen and placed in a lower position, the electrodes being one and the other of the segment electrode and the common electrode,thereby canceling the voltage induced at the electrode placed in the upper position by applying the correction voltage generated by the correction voltage generation means to the electrode placed in the upper position at least in a period when the electrode placed in the lower position is scanned.
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Accused Products
Abstract
A detection and hold circuit outputs a reference signal having a level proportional to an x-coordinate detection pulse input from an X-coordinate signal amplifier. A delay element delays the reference signal. An adder adds the x-coordinate detection pulse from the X-coordinate signal amplifier and a delayed signal from the delay element. Comparators obtain a coordinate detection pulse making a detection signal from another detection and hold circuit for an LCD voltage inversion pulse serve as a reference signal. Thus noise following the x-coordinate detection pulse is removed to generate a coordinate detection pulse with a reference value corresponding to the level of the LCD voltage inversion pulse to allow a stable coordinate detection to be achieved. A correction signal generation circuit reads out correction data stored in an internal memory and transmits the data as a correction signal to a correction voltage generation circuit in an x-coordinate detection period when the segment electrode placed in the lower position is scanned. The correction voltage generation circuit generates a correction voltage for canceling a voltage induced at the common electrode placed in the upper position based on the input correction signal and a bias power source input from a DC power supply circuit.
38 Citations
6 Claims
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1. A display-integrated type tablet device including a display panel which has a display material interposed between segment electrodes and common electrodes crossing each other at right angles and is driven by a duty ratio control type drive method, a detection pen having at a tip of the detection pen an electrode electrostatically coupled with the segment electrodes and the common electrodes of the display panel, a segment electrode drive circuit for driving the segment electrodes, a common electrode drive circuit for driving the common electrodes, a display control circuit for displaying an image on the display panel by controlling the segment electrode drive circuit and the common electrode drive circuit in a period of displaying the image, a detection control circuit for controlling the segment electrode drive circuit to sequentially scan the segment electrodes of the display panel by applying a scanning voltage successively to the segment electrodes and controlling the common electrode drive circuit to sequentially scan the common electrodes by applying a scanning voltage successively to the common electrodes in a coordinate detection period, an x-coordinate detection circuit for detecting an x-coordinate value designated on the display panel by the tip of the detection pen according to an output signal generating timing of the detection pen and a scanning timing of the segment electrodes, and a y-coordinate detection circuit for detecting a y-coordinate value designated on the display panel by the tip of the detection pen according to an output signal generating timing of the detection pen and a scanning timing of the common electrodes,
the display-integrated type tablet device comprising a correction voltage generation means for generating a correction voltage for canceling a voltage induced at an electrode closer to the detection pen and placed in an upper position attributed to a scanning voltage applied to an electrode farther to the detection pen and placed in a lower position, the electrodes being one and the other of the segment electrode and the common electrode, thereby canceling the voltage induced at the electrode placed in the upper position by applying the correction voltage generated by the correction voltage generation means to the electrode placed in the upper position at least in a period when the electrode placed in the lower position is scanned.
Specification