Display-integrated type tablet device capable of detecting correct coordinates at a tip end of a detection pen by detecting external noise

• US 5,491,706 A
• Filed: 04/05/1994
• Issued: 02/13/1996
• Est. Priority Date: 04/07/1993
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nohno, Hitoshi, Nozaki, Kiyohiro, Okamura, Kazunari, Tagawa, Takao
• Primary Examiner(s): Beausoliel, Jr., Robert W.
• Assistant Examiner(s): Decady, Albert
• Application Number:
  US08/222,907
• Time in Patent Office: 679 Days
• Field of Search: 371/48, 371/57.2, 371/57.1, 345/3, 345/33, 345/44, 345/180, 345/181, 345/182, 345/183, 345/184, 345/104, 345/174, 178/18, 178/19, 364/561, 341/5, 341/6
• US Class Current: 714/812
• CPC Class Codes: G06F 11/0754 by exceeding limits
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

An induction voltage signal induced at a detection electrode of a detection pen is binarized by a slice voltage "e_s ". The number of pulses existing in the binary signal is counted by a counting device. The resulting count value obtained by the counting device and the number of times of electrode scanning in an x-coordinate detection period or a y-coordinate detection period are compared with each other by means of a comparator. When the number of pulses is greater, an error detection alarm signal is output by an alarm device. Thus the existence of the pulses based on the error detection signal is detected in the binary signal based on the induction voltage signal from the detection electrode to output the error detection alarm signal. The above arrangement allows the coordinates at the tip end of the detection pen to be detected in a stable and correct manner even when external noise is detected.

Claims

1. A display-integrated type tablet device including a display panel having first electrodes arranged in parallel in one direction and second electrodes arranged in parallel in another direction perpendicular to the one direction, a detection pen having at a tip end a detection electrode electrostatically coupled with the first electrodes and the second electrodes, a first drive circuit for driving the first electrodes, a second drive circuit for driving the second electrodes, a display control circuit for displaying an image on the display panel by controlling the first drive circuit and the second drive circuit in an image display period, a detection control circuit for controlling the first drive circuit and the second drive circuit in a coordinate detection period so as to apply a scanning voltage to the first electrodes and the second electrodes to sequentially scan the first and second electrodes, and a coordinate detection circuit for detecting coordinates at a point pointed by the tip end of the detection pen according to a timing of generation of an output signal from the detection pen and a timing of scanning the first electrodes or the second electrodes, the display-integrated type tablet device comprising:

count means which counts a total number of times when the output signal output from the detection pen in the coordinate detection period exceeds a threshold level; and

error detection determination means which compares a count number obtained by the count means in one coordinate detection period with the number of times of scanning the electrodes in the one coordinate detection period by means of the detection control circuit, and determines that, when the count number is greater than the number of times of scanning, error detection coordinates are included in coordinates on the display panel detected by the coordinate detection circuit in the coordinate detection period.

2. A display-integrated type tablet device including a display panel having first electrodes arranged in parallel in one direction and second electrodes arranged in parallel in another direction perpendicular to the one direction, a detection pen having at a tip end a detection electrode electrostatically coupled with the first electrodes and the second electrodes, a first drive circuit for driving the first electrodes, a second drive circuit for driving the second electrodes, a display control circuit for displaying an image on the display panel by controlling the first drive circuit and the second drive circuit in an image display period, a detection control circuit for controlling the first drive circuit and the second drive circuit in a coordinate detection period so as to apply a scanning voltage to the first electrodes and the second electrodes to sequentially scan the first and second electrodes, and a coordinate detection circuit for detecting coordinates at a point pointed by the tip end of the detection pen according to a timing of generation of an output signal from the detection pen and a timing of scanning the first electrodes or the second electrodes, wherein

the detection control circuit is constructed so as to provide a non-scanning period when no electrode is scanned in the coordinate detection period, and

there is further comprised error detection determination means which observes a state of the output signal output from the detection pen in the non-scanning period, and determines that, when the state of the output signal exhibits deviation of the signal from a normal state where no external noise exists, error detection coordinates are included in coordinates on the display panel detected by the coordinate detection circuit in the coordinate detection period including the non-scanning period.

3. A display-integrated type tablet device including a display panel having first electrodes arranged in parallel in one direction and second electrodes arranged in parallel in another direction perpendicular to the one direction, a detection pen having at a tip end a detection electrode electrostatically coupled with the first electrodes and the second electrodes, a first drive circuit for driving the first electrodes, a second drive circuit for driving the second electrodes, a display control circuit for displaying an image on the display panel by controlling the first drive circuit and the second drive circuit in an image display period, a detection control circuit for controlling the first drive circuit and the second drive circuit in a coordinate detection period so as to apply a scanning voltage to the first electrodes and the second electrodes to sequentially scan the first and second electrodes, and a coordinate detection circuit for detecting coordinates at a point pointed by the tip end of the detection pen according to a timing of generation of an output signal from the detection pen and a timing of scanning the first electrodes or the second electrodes, the display-integrated type tablet device comprising:

binarization means which binarizes the output signal from the detection pen by different slice levels of a first slice level and a second slice level higher than the first slice level, and transmits a binary signal binarized by the first slice level to the coordinate detection circuit; and

error detection determination means which observes a binary signal binarized by the second slice level by the binarization means, and determines that, when the level of the output signal exceeds the second slice level, coordinates on the display panel detected by the coordinate detection circuit at a point of time in the closest proximity to the point of time when the level of the output signal exceeds the second slice level are error detection coordinates.

4. A display-integrated type tablet device including a display panel having first electrodes arranged in parallel in one direction and second electrodes arranged in parallel in another direction different from the one direction, a detection pen having at a tip end a detection electrode electrostatically coupled with the first electrodes and the second electrodes, a first drive circuit for driving the first electrodes, a second drive circuit for driving the second electrodes, a display control circuit for displaying an image on the display panel by controlling the first drive circuit and the second drive circuit in an image display period, a detection control circuit for controlling the first drive circuit and the second drive circuit in a coordinate detection period so as to apply a scanning voltage to the first electrodes and the second electrodes to sequentially scan the first and second electrodes, and a coordinate detection circuit for detecting coordinates at a point pointed by the tip end of the detection pen according to a timing of generation of an output signal from the detection pen and a timing of scanning the first electrodes or the second electrodes, wherein

the detection electrode of the detection pen is covered with a tip end member made of a dielectric material for protecting the detection electrode and a protection surface of the display panel,

the coordinate detection circuit is constructed so as to detect the coordinates using only one polarity of the output signal from the detection pen with respect to a reference voltage, and

a combination of material of the tip end member of the detection pen and material of the protection surface of the display panel is a combination such that a polarity of frictional electricity at the tip end of the detection pen is the same one polarity as the polarity of the output signal used by the coordinate detection circuit.

5. A display-integrated type tablet device as claimed in claim 4, wherein

the first drive circuit and the second drive circuit apply a scanning voltage to each of the electrodes in sequentially scanning the first electrodes and the second electrodes in the coordinate detection period, the scanning voltage being such that its polarity with respect to the reference voltage is the same one polarity as the polarity of the frictional electricity at the tip end member of the detection pen.