Touch screen

• US 5,708,460 A
• Filed: 06/02/1995
• Issued: 01/13/1998
• Est. Priority Date: 06/02/1995
• Status: Expired due to Fees

• Current Assignee: AVI Systems Incorporated
• Original Assignee: AVI Systems Incorporated
• Inventors: Young, Thomas M., Becker, William Martin, Shamash, Joseph
• Primary Examiner(s): Powell, Mark R.
• Assistant Examiner(s): Luu, Matthew
• Application Number:
  US08/460,647
• Time in Patent Office: 956 Days
• Field of Search: 345/173, 345/174, 178/18, 178/19
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate

Abstract

A touch screen or touch panel wherein there is a monitoring of relative distribution of force via one or more, preferably symmetrically positioned, sensors such as strain gage sensors. The strain gage sensors are positioned such that bending strain on the touch screen, engendered by touch, is detected by the one or more strain gages and accurately measured by an electronic controller, connected to the strain gage(s). The electronic controller, or associated hardware, is programmed to relate relative bending force to a unique position on the screen and is a charge balancing and multiplying analog-to-digital converter which provides accurate position determination, even with very low forces and with very minor differentiation in position related forces. A sum and divide analog-to-digital converter uses charge balancing and integration, with the balance charge coming from the plus and minus sum of the corners (wherein four sensors are positioned at the corners of a square or rectangular display), and the input signal is the difference between two sides of the display panel. This, in effect, results in the input signal being divided by the sum signal and the sum of charge counts over a fixed interval, resulting in the output value and unique position determination. A unique mounting structure for flat panel displays includes using the flat panel as the bending beam and wherein a circuit board mounted behind the flat panel transmits forces to sensors mounted on the circuit board.

Claims

1. A touch screen comprising sensors for monitoring relative distribution of force thereon, said sensors being positioned relative to the touch screen such that bending strain on the touch screen, engendered by touch, is detected by the sensors, wherein said sensors transmit one or more input signals to a charge balancing and multiplying analog to digital converter configured to relate bending force to an identifiable unique position on the screen, the charge balancing and multiplying analog to digital converter comprising a sum and divide analog-to-digital converter using charge balancing and integration, wherein said sensors provide sensing and valuation of touch forces on said screen, from opposite sides of said screen, with conversion of the valuation of the touch forces from opposite sides of the screen to separate proportional charge signals, whereby a balance charge comes from the plus and minus sum of the sensing of touch forces on said screen from opposite sides thereof, and means for converting the balance charge to a position on the screen, wherein said screen is quadrilateral and wherein said sensors include at least four sensors positioned at the four corners of the quadrilateral screen, wherein an input signal is the difference between proportional charge signals from two opposite sides of the screen and wherein the input signal is divided by the sum signal and the sum of charge counts over a fixed interval, resulting in an output value used by the means for converting the balance charge to a position on the screen.

2. The touch screen of claim 1, wherein the screen is comprised of a relatively stiff, low mass material, wherein the relative stiffness is such that it permits for detectable and reproducible bending movement of the screen under exerted touch forces, and the mass is such that damping effects, which may interfere with the detection of the magnitude of the bending movement, is minimized.

3. The touch screen of claim 2, wherein the screen is fixedly held in position by a metal stand, with the screen being held by metal brackets at the corners of the screen, and wherein said metal brackets transmit the bending forces exerted on said screen to said sensors.

4. The touch screen of claim 3, wherein said sensors comprise strain gages integrated with said brackets.

5. The touch screen of claim 4, wherein pairs of strain gages at opposite sides of the quadrilateral provide input signals for both horizontal and vertical position determination on said screen.

6. The touch screen of claim 1, wherein said screen comprises a CRT.

7. The touch screen of claim 1, wherein said screen comprises a touch panel.

8. The touch screen of claim 1, further comprising touch pressure sensing means whereby pressure on a single point of the touch screen is detected by said pressure sensing means to provide sound responses to simulate tactile and communication feedback effects.

9. The touch screen of claim 1, further comprising touch pressure sensing means whereby degree of pressure on a single point of the touch screen, having operational instructions associated therewith, is detected by said pressure sensing means to provide variations in commands and interpretation.

10. The touch screen of claim 8, wherein one range of pressure causes said pressure sensing means to provide a "yes" response or command, whereas a recognizably distinct second pressure range causes said pressure sensing means to provide a "no" response or command.

11. The touch screen of claim 10, wherein the touch screen is part of a flat panel display and wherein the flat panel display functions as the bending beam when touched, wherein said display is mounted on at least one mechanical stand member and peripherally held in place by a frame member, with the mechanical stand member being sandwiched between the flat panel display and a force transmitting member, held in stationary relation to the flat panel display, said force transmitting member having force sensors affixed thereto for detecting touch pressure exerted on said flat panel display.

12. The touch screen of claim 11, wherein said force transmitting member comprises a circuit board.

13. The touch screen of claim 11, wherein said force transmitting member comprises a housing for said force sensors.

14. A touch screen device comprising:

a first sensor and a second sensor positioned relative to opposing sides of a touch screen, such that bending strain on the touch screen, engendered by touch, is detected by the first and second sensors, the first and second sensors outputting respective first and second sensor signals; and

a charge balancing and analog to digital converter having a difference signal input, a positive charge sum input, and a negative charge sum input, said difference signal input coupled to a difference of the first and second sensor signals, the positive charge sum input coupled to a sum of the first and second sensor signals, the negative charge sum input coupled to a negative sum of the first and second sensor signals, the charge balancing analog to digital converter relating a bending force applied to the touch screen to an identifiable position on the display screen as a function of the first and second sensor signals.

15. The touch screen device according to claim 14, wherein the charge balancing and analog to digital converter further comprises an integrator having an integrator input, the integrator input and the difference signal input being coupled to a common node, the positive charge sum input and negative charge sum input being selectively coupled to the common node to provide a balance charge to the common node.

16. The touch screen device according to claim 14, wherein the touch screen is a display screen.

17. The touch screen device according to claim 14, wherein the touch screen is a flat panel display.

18. The touch screen device according to claim 14, wherein the touch screen is a measuring device.