Patent Application
20060214920
The present invention relates generally to touch sensing apparatuses such as those used in certain personal computers, and particularly to a touch sensing apparatus for sensing a noise generated by a user's touch.
There are several available touch-sense technologies which may be employed for use as a position indicator in an apparatus such as a personal computer. Resistive-membrane position sensors are known and used in several applications. However, these sensors generally have poor resolution. In addition, the sensor surface is exposed to the user and is thus subject to wear. Further, resistive-membrane touch sensors are relatively expensive. A one-surface sensor configuration requires a user to be grounded relative to the sensor for reliable operation. This cannot be guaranteed in applications such as with portable computers. An example of a one-surface sensor configuration is the UnMouse product available from MicroTouch, of Wilmington, Mass.
A touch sensitive control device translates touch location into output signals. The device includes a substrate which supports first and second interleaved, closely spaced, non-overlapping arrays of conductive plates. An insulating layer overlies the first and second arrays so that when the outer surface of the insulating layer is touched, the capacitance of at least one of the columns of plates of the first array and the rows of plates of the second array underlying the insulating layer at the location being touched exhibits a change of capacitance with respect to ambient ground. Based upon the measured capacitance of each column of the first array and row of the second array, the microcomputer produces output signals which represent the coordinates of the location being touched. These output signals can be used, for example, to control the position of a cursor on a display screen of a personal computer or to make selected function commands.
In a second kind of conventional apparatus, a tablet for sensing the position of a stylus is provided. The stylus alters the transcapacitance coupling between row and column electrodes, which are scanned sequentially. In a third kind of conventional apparatus, a radial electrode arrangement is provided adjacent the space bar of a keyboard. The radial electrode arrangement is part of a trackball system, and can be activated by a user touching the trackball with his/her thumb. This third kind of apparatus teaches the use of total touch capacitance as an indication of the touch pressure, in order to control the velocity of motion of a display screen cursor. Pulsed sequential polling is employed to address the effects of electrical interference.
What is still needed is a touch sensing apparatus with reduced circuitry complexity, low power consumption, improved sense accuracy, improved efficiency, and lower manufacturing costs.
A preferred embodiment of a touch sensing apparatus includes a plurality of sensing units, and a plurality of grounding lines. Each sensing unit includes an antenna, a controlling circuit, a detector, and a feedback line. The antenna is for receiving a noise of a user's finger. The controlling circuit preferably includes a diode and a capacitor. The diode is for filtering out a static electrical signal of the user's finger and attenuating the noise, and the capacitor is for attenuating the noise from the diode. The detector is for converting the noise into a digital signal, and transmitting the digital signal to an MCU (Microprogrammed Control Unit). The feedback line forms a feedback circuit with the antenna, thereby improving the accuracy of sensitivity of the sensing unit. The grounding lines are for insulating the sensing units.
Other advantages and novel features will be drawn from the following detailed description of the preferred embodiment with reference to the attached drawings, in which:
The human body is itself electrically conductive with a noise and a static electrical signal. Therefore, when a user touches the sensor 101, namely the antenna 201, the noise and the static electrical signal of the user flow through the antenna 201. The antenna 201 transmits the noise and the static electrical signal to the clamping circuit 202. However, the static electrical signal can cause interference to the noise, and can even cause the detector 203 to break down. In addition, a strong noise may adversely influence a result output to the MCU 206; that is, the sensitivity of the sensing unit 10 may be diminished. Accordingly, the clamping circuit 202 is for eliminating the static electrical signal and attenuating the noise, and thus improving the accuracy of sensitivity of the sensing unit 10. The clamping circuit 202 includes a diode 2021 having an anode and a cathode, and a capacitor 2022 having two ends. The anode is connected to the antenna 201, and the cathode is connected to ground. Upon receiving the static electrical signal and the noise, the diode 2021 filters out the static electrical signal to ground so as to avoid breakdown of the detector 203, and attenuates the noise and transmits the attenuated noise to the capacitor 2022. The capacitor 2022 leaks a portion of the attenuated noise through to ground. Thus the attenuated noise is further attenuated, thereby obtaining an accurate sensitivity. The detector 203 has a high input impedance, so as to easily detect the further attenuated noise received from the input end of the detector 203. Then the detector 203 converts the further attenuated noise into a digital signal, and transmits the digital signal through the output end of the detector 203 to the MCU 206 for the MCU 206 to perform corresponding control. Furthermore, because the feedback line 204 forms a positive feedback circuit with the antenna 201, the noise generated as the user touches the edge of the sensing unit 10 is attenuated, thereby further improving the accuracy of sensitivity of the sensing unit 10.
Although the present invention has been specifically described on the basis of a preferred embodiment, the invention is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiment without departing from the scope and spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200510033852.1 | Mar 2005 | CN | national |
