Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
2001-11-20
2004-09-07
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S173000, C178S018090, C250S227140, C250S227160
Reexamination Certificate
active
06788295
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to touch pads for controlling electronic equipment. More particularly the invention relates to a deformable pressure sensor for detecting the position of an indentor, mediated by changes in light intensity within the interior of a touch pad caused by local application of pressure, to control electronic equipment.
BACKGROUND OF THE PRIOR ART
So called “touch pads” are commonly used to control electronic equipment. A well-known application of this device is for control of a computer, namely the familiar “touch pad” associated with many laptop computers. Touch pads can also be used to control other types of equipment, and they have the potential within many fields of application to provide a simple, highly accurate and easy to use control means.
Touch pads consist of devices which detect the position of an “indentor” and use this information to effect some form of control over an electronic device. The indentor can be a user's finger or fingers or another part of the user's body, or a tool like a pen or stylus which is wielded by the user. A touch pad may respond to one or more indentors. A touch pad can also respond both to positional information and the amount of pressure exerted on the pad.
Virtually all touch pads now in use rely in one respect or other on electrical circuitry within the pad to convert a user's touch into an electronic signal. Some touch pads, like those used on many laptop computers, are based on sensing of the electrical properties of the indentor, such as its capacitance. These pads are well suited to locating the position of a finger, which is used to control a pointer on the computer display. They typically do not register the amount of pressure exerted by a finger, nor do they respond to an electrically inert indentor such as a pencil.
Other touch pads are based upon force sensitive resistor technology. This technique allows the detection of the amount of pressure exerted by an indentor, as well as the position of the indentor on the surface of the pad. The indentor may comprise the user's finger, or any other electrically inert object. Touch pads based on this technology are becoming widely used as computer control devices. Yet other touch pads are commonly called graphics tablets. These require specialized indentors, which work in conjunction with the tablets. With some tablets, the indentors emit acoustic energy which is timed by the tablet to compute the location of the indentor. Others use an inductive principle to locate the position of the indentor, sometimes the quantum of pressure and even its tilt with respect to the horizontal plane.
There is a need for touch pads that do not require specialized indentors; such indentors can be expensive and not as convenient or expressive as fingers. There is a need for touch pads which can simultaneously locate several indentors—this would allow for the capture of gestures made by several fingers, and the use of those gestures to control equipment in a complex manner. There is also the need for touch pads that are relatively inexpensive to produce, and which do not rely on electrical sensing systems to measure the location of indentors.
Humans typically use several fingers simultaneously to control various tools, musical instruments and toys. Computer applications such as control systems for machines, drawing programs, musical synthesizers and video games would benefit from the use of expressive control means which allow the input of complex multi-touch gestures. Touch pads to capture such gestures could be produced using electrical sensing techniques. However, the multiplicity of individual touch sensor elements that would be required would lead to an expensive device, and the low level electrical signals from such sensors are susceptible to electrical noise at a level which could drown the usable signal.
It is herein proposed to provide a touch pad that relies on a pressure sensor of the type described within PCT publication No. WO 99/04234. This type of pressure sensor relies on a deformable integrating optical cavity (i.e. one capable of scattering and/or diffusing light) formed within a deformable material such as polymeric foam for detecting a pressure applied to the material. Light or other wave energy is beamed into the material from a source, to form an optical cavity with the material, consisting of a region of fully scattered light from the source. A detector within or adjacent to the optical cavity and spaced apart from the source detects intensity of the scattered and diffused light within the compressible material. The sensor operates on the principle whereby deformation of the material decreases the effective size of the integrating optical cavity and thereby increases the light intensity in the region around the source. Thus, in the case where the emitter and detector are adjacent to each other or in the vicinity of each other, they will both reside within the same optical cavity, the boundaries of which are established by the illuminated zone created by the light source. Light within the cavity is fully integrated (i.e. scattered) by the scattering centers evenly disbursed within the sensor body. That is, light received at any single point within the optical cavity emanates from all directions generally evenly. An increase in pressure on the material and consequent deformation in the region of the light source results in a consequent increase in the intensity of light within the optical cavity and detected by the detector. The signal corresponding to the intensity detected by the detector is transmitted to a processing unit which in turn quantifies the pressure experienced by the material.
Throughout the present patent specification, it will be understood that the term “light” embraces wave energy of any suitable form, including electromagnetic radiation in the non-visible spectra.
In one version of a prior art pressure sensor of this type, the light emitter and detector each comprise multiple fiber optic strands leading to and from a central controller. With this arrangement, multiple detectors and emitters can be spaced throughout the sensor body in such a way that they can detect the pressures from multiple indentors. For example, a sheet of deformable material may be underlain with a planar array of light emitter/detector pairs, which detect and localize deformation of a particular portion of the sheet.
This principle is particularly advantageous for use with touch pads, since it allows the provision of a plurality of spaced-apart light sensors within the pad body material, with the spacing and the material itself optimized to detect the range of pressures expected from particular types of indentors.
It is an object of this invention to provide a touch pad which addresses the above requirement. It is also an object of this invention, in order to minimize cost and complexity, to provide a light-based sensor which achieves a highly sensitive, multi-indentor detectability with a minimum number of light emitters and detectors.
SUMMARY OF THE INVENTION
The invention comprises in one aspect a touch pad for controlling an electronic apparatus comprising a flat, resilient pad having means to detect the position of an indentor bearing down on the pad and means to convert localized pressure into an electronic signal, characterized by:
the pad body comprising a light-translucent compressible material having light scattering centers evenly disbursed therein and capable of forming within the interior of the pad body an integrated optical cavity defined by a region of fully scattered or diffused light;
multiple spaced apart light emitter and detector pairs in communication with the pad body, positioned to form within the pad body an array of adjacent cells, each cell comprising an optical integrating cavity whereby localized compression of the pad by one or more indentors increases the light intensity within one or more corresponding cells;
signal processing means for receiving signals from the detectors and converting the sign
Lao Lun-Yi
McFadden Fincham
Tactex Controls Inc.
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