Coordinate inputting apparatus with shared line combinations of power, position and switch signals

• US 5,736,980 A
• Filed: 04/13/1995
• Issued: 04/07/1998
• Est. Priority Date: 04/28/1994
• 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: Hirano, Katsumi, Nishimura, Tomohiko, Nomiya, Kazuyoshi, Hiromoto, Kunio, Iguchi, Shigeki
• Primary Examiner(s): Powell, Mark R.
• Application Number:
  US08/421,358
• Time in Patent Office: 1,090 Days
• Field of Search: 345/156, 345/157, 345/104, 345/173, 345/179, 178/18-20, 341/5, 349/1, 349/12
• US Class Current: 345/179
• CPC Class Codes: G06F 3/03545 Pens or stylus
• 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

A coordinate inputting apparatus has a separating circuit, a cable and a position indicating pen. The separating circuit has a low pass filter for removing an alternating current component from a signal transmitted to a signal line and a band pass filter for passing only a position information signal in a predetermined frequency band with respect to the signal transmitted to the signal line. The cable is constructed by a signal line, a switching signal line and a ground line. The signal line is used to supply power to the position indicating pen and transmit a detecting signal from the position indicating pen to each of an X-coordinate detecting circuit and a Y-coordinate detecting circuit. The position indicating pen has a low pass filter for removing an alternating current component from a signal transmitted through the signal line and a band pass filter for passing only a position information signal in a predetermined frequency band. A signal transmitting system of this coordinate inputting apparatus and other coordinate inputting apparatuses are also shown.

Claims

1. A coordinate inputting apparatus comprising:

liquid crystal panel having a liquid crystal layer interposed between plural segment electrodes and plural common electrodes, said plural segment electrodes and plural common electrodes arranged perpendicular to each other;

a position indicator electrostatically coupled to said segment electrodes and said common electrodes in an indicated position for outputting a position information signal on a first signal line;

a switch arranged in the vicinity of an end tip of said position indicator and turned on and off by making the switch come in contact with said liquid crystal panel and separating this switch from said liquid crystal panel for outputting a signal indicating the state of said switch on said first signal line supplying power for said position indicator and said switch;

coordinate detector for detecting coordinates in said indicated position on the basis of an induced voltage induced in said position indicator and application timing of a scanning voltage applied to said segment electrodes and said common electrodes, including a separating circuit for separating each of said position information signal and said signal indicating the state of said switch from said first signal line; and

a cable for connecting said position indicator with said coordinate detector including signal lines of said first signal line and a second signal line connected to the ground.

2. A pen inputting apparatus comprising:

a liquid crystal panel constructed by a liquid crystal and an electrode for operating this liquid crystal;

a detecting pen having an end tip electrode electrostatically coupled to the electrode of said liquid crystal panel and detecting an induced voltage induced at each of rising and falling times of a signal for operating the liquid crystal;

an inverting signal generator for operating the liquid crystal of said liquid crystal panel and generating an inverting signal for inverting applying directions of a voltage applied to the liquid crystal;

a gate signal generator for generating a first gate signal synchronized with each of rise and fall of said inverting signal and a second gate signal provided except for a transmitting time of this first gate signal;

a first sampling processor for sampling the induced voltage induced in the end tip electrode of said detecting pen by the first gate signal and converting this induced voltage to a first direct current voltage in response to the rising and falling of said inverting signal;

a second sampling processor for sampling an induced voltage induced after the sampling of the first sampling processor by the second gate signal and converting this induced voltage to a second direct current voltage;

a judging circuit for judging whether or not an end tip of said detecting pen approaches a display screen of said liquid crystal panel on the basis of level difference between said first and second direct current voltages and outputting results of this judgment as a detecting mode/nondetecting mode signal; and

a duty ratio control circuit for controlling a duty ratio of the first and second gate signals generated by said gate signal generator and for controlling sampling times of the gate signals supplied to the first and second sampling processors by controlling the duty ratio of the first and second gate signals, and adjusting the levels of the first and second direct current voltages so that the judging circuit stably outputs the detecting mode/nondetecting mode signal.

3. A pen inputting apparatus as claimed in claim 2, wherein the duty ratio control circuit has a duty ratio setting circuit for setting said duty ratio by numeric value data.

4. A pen inputting apparatus as claimed in claim 2 or 3, wherein the pen inputting apparatus further comprises an automatic setting functional key for indicating an automatic setting function of said duty ratio;

said duty ratio control circuit controls an operation of said gate signal generator such that the duty ratio of said gate signal is sequentially changed from predetermined numeric value data when the automatic setting function is indicated by said automatic function key and said detecting pen approaches a predetermined region on the display screen of said liquid crystal panel;

said duty ratio control circuit also detects the duty ratio of the gate signals when the judging circuit outputs the detected mode signal; and

said duty ratio control circuit further controls said gate signals with numeric value data of this detected duty ratio as initial set data.

5. A tablet inputting apparatus comprising:

an input pen having a pen shaft, a main electrode attached to the pen shaft and an auxiliary electrode attached to the pen body so that the relative position of the auxiliary electrode with respect to the main electrode will change in response to a writing pressure such that an electrostatic capacity between the auxiliary electrode and a tablet can be changed in accordance with the writing pressure, and for outputting a first signal representing an electrostatic capacity between the main electrode and the tablet, and a second signal representing the electrostatic capacity between the auxiliary electrode and the tablet;

the tablet for sliding the input pen along a surface thereof;

a first detector for detecting a change in the second signal caused by the writing pressure; and

a second detector for detecting a time difference between peaks of the first and second signals representing an inclination of the pen.

6. A tablet inputting apparatus as claimed in claim 5, wherein the auxiliary electrode is formed in a ring shape having a hollow portion and the main electrode is inserted into the hollow portion of the auxiliary electrode through an insulator.