Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
  • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
  • G06F3/03545—Pens or stylus
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
  • G06F2203/041—Indexing scheme relating to G06F3/041 - G06F3/045
  • G06F2203/04105—Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position

Definitions

• a pressure sensitive stylus can be emphasized by the fact that it mimics the action of a pen that everybody has learnt to use as a kid. To a painter, a pressure sensitive stylus provides a valuable tool as a paintbrush.
• the prior art can be broadly divided into two sections where the intensity based fiber optic sensors and styluses for digitizer are disclosed.
• An optical fiber based sensor can be designed by modulating any of the light's parameters such as intensity, phase, polarization, frequency, and the wavelength.
• intensity based sensors are the easiest to design as it requires only a source, detector and/or collimating lens.
• a type of intensity sensors is based on the amount of light being coupled into the fiber from any object that acts as a reflected source. Thus, readily, a displacement sensor (the reflected source moves closer or farther away), frequency of vibration sensor (the reflection source vibrates), refractive index sensor (the amount of light reflected back depending on the refractive index of the medium) can be designed.
• the stylus is passive, and the digitizer is active, which often consists of capacitive sheets, conductors, and optical fibers.
• the stylus is active and often consists of inductor coils, conducting surfaces, and laser pointers.
• a common design for an active digitizer consists of vertical and horizontal arrays of conductors that detect finger touch or stylus through measuring capacitance or radio frequency (RF) transfer (US 4,686,332, US 5,007,085). Because the stylus is radiatively coupled to the oscillating electromagnetic (EM) wave, the digitizer can also detect the height of the stylus from the tablet (conductor array) surface.
• RF radio frequency
• a modification to the digitizer described above includes the usage of orthogonal layers of horizontal lines of conductors that are separated by an insulator from one another. The insulating layer is thin enough to allow for capacitive coupling between the finger/stylus and both layers of conductors. This modification allows for not only the position sensing but also the pressure sensitivity (US 5,488,204).
• a further modification to the above includes the utilization of a pressure sensitive conductive material which is placed on one of the orthogonal conducting surfaces as described above. This enables that any stylus (and not only conducting) can be used with the capacitive digitizer (US 5,942,733). LaGrange et al. used a conductive foam cap over the stylus to amplify the measured capacitive disturbance (US 5,914,708). As for the active stylus, there has been a wide range of modifications to the stylus design employing acoustic, optic, and EM design to engineer an active stylus.
• the stylus In an acoustic stylus, the stylus is provided with at least two acoustic sources located at different heights that can emit pulsed acoustic signals.
• the acoustic signal generated is picked by at least two microphones present on the tablet. By measuring the delay in the signals between the microphones, the position of the stylus could be located.
• the presence of two acoustic sources (instead of having one) eliminates the error in the position measurement due to the tilt and angle of the stylus (US 4,246,439).
• the display unit has a transparent surface, and carries optically detectable patterns called as tablet address cells.
• the stylus collects the micro images and decodes for determining the position of the stylus on the tablet (US 5,652,412). Or, the micro images have different absorption/ reflection compared to the non-coded part of the tablet surface (US 5,051,736).
• optical fiber is used to illuminate the plane of the tablet surface, and a stylus or a finger obstructs the light being recorded by the detectors appropriately placed (US 5,852,434).
• the stylus In a stylus using the principle of electromagnetic coupling, the stylus consists of radio frequency inductor/conductor circuit (US 5,347,295).
• the digitizer can detect when the stylus is within the proximity or in contact with the surface of the digitizer.
• the stylus is used not only to point and click, but also used as gesture based device to perform many of digitizer activities such as cut, paste, delete, and edit.
• the gesture done on the screen is compared with the predefined gesture shapes, thereby performing the action.
• Wobbrock et al designed "edgewrite", a stylus based input device.
• the text recognition is not based on the stylus tracing the text character, but rather on the order in which it touches the edges of a small rectangular notch (Wobbrock, Jacob 0., Brad A. Myers, and John A. Kembel. "EdgeWrite: a stylus-based text entry method designed for high accuracy and stability of motion.” Proceedings of the 16th annual ACM symposium on User interface software and technology. ACM, 2003).
• Distributed fiber optic overlay is also used in one design to backlit the surface of the tablet and also to help pick the menu (US 5,001,306).
• the stylus in one type, the stylus consists of movable and fixed magnetic bodies. The displacement of the movable body which is connected to the stylus tip is an indicator of the applied pressure (US 5,565,632).
• Another design consists of using pressure sensitive resistance (force sensitive resistance FSR) element at the back end of the stylus connected to the front end of the stylus through springs (US 5,581,052).
• FSR force sensitive resistance
• a modification to the FSR consists of a ball point cartridge cylinder, where the stylus tip is a ball point pen and the distal end presses against a linear strain sensor like a strain gage (US 4,111,052).
• pressure transducer either variable capacitor or inductor
• annular form coaxial to a pressure transmitting member
• the advantageous concept behind the present invention constitutes a special cap, a fiber sensor and an accordingly designed stylus.
• the design of fiber optic stylus requires that the concept of fiber optic pressure sensor be incorporated inside a cylindrical stylus with design of a special cap.
• the reflective cap (stylus tip) with reflecting property deforms locally under the applied load.
• the load exerted on to the deformable stylus tip is directly convertible into pressure information by using a fiber optic sensor according to the present invention.
• Objects of the Invention Primary object of the present invention is to develop a pressure sensitive stylus that could be used efficiently across all platforms of digitizers (capacitive, resistive, distributed fiber based, optic based, etc.). To achieve this, optical fiber based pressure sensor is utilized. Another object of the present invention is to create a pressure sensitive stylus that is independent of the nature of the computing platform (tablets, PC, smart phones, some of which may not have a digitizer).
• Fig. 1 is a schematic of a representative pressure sensitive stylus according to the present invention.
• Fig. 2 is a schematic of a representative stylus that houses an optical fiber sensor, a light source, a detector and a Bluetooth/wifi device for communicating with the digitizer, and a battery.
• Fig. 3 is a cross-sectional schematic of a representative pressure sensitive stylus with embedded components according to the first embodiment of the present invention.
• Fig. 4 is a cross-sectional schematic of a representative pressure sensitive stylus with embedded components according to the second embodiment of the present invention.
• Fig. 2 represents a schematic of a stylus that houses an optical fiber sensor, a light source, a detector, and a Bluetooth/wifi device for communicating with the digitizer, and a battery.
• the stylus according to the present invention consists of a deformable stylus tip (11), preferably having an outer rubber portion, which is either detachable or fixed.
• the interior of the stylus tip (11) is hollow, and its concave surface (12) is made of a reflective material.
• the inner surface of the stylus tip (11) according to the present invention can be made reflective through metal coating (i.e., thin and reflective aluminum coating) or any other means.
• a fiber optic probe (13) is attached at the focal point of this concave mirror, which is also referred to as the reflective surface.
• the fiber optic probe (13) consists of either 2 or 6 optical fibers; in the case of 6 fibers, they are being arranged hexagonally around a central optical fiber.
• the far end (from the reflective cap) of the central optical fiber is coupled to a laser/light source.
• the light carried by the central optical fiber onto the concave reflective surface/mirror (12) and reflected thereof is coupled to the six hexagonal fibers, which is in turn coupled to a detector (photo-detector, CCD or CMOS).
• the light source and the photo-detector for instance a LED and a photodiode, are demonstrated as a single module (14) in Fig. 3 and 4.
• a battery (15), a convenient rubber grip (16), a signal module (17) and a closing lid (18) are provided.
• the angular offset also adds to the change in intensity measurement. It is, however, not given here for simplicity, in line with the laboratory experiment of EE234 Photonics Laboratory, Lab 4 (Laser to Fiber Coupling Carsten Langrock, John XJ Zhang, October 31, 2001).
• the intensity detected is the reference intensity.
• the concave mirror, i.e. the reflective surface (12) is distorted due to the pressure applied by the user on the stylus tip (11).
• the change in intensity as given by the above equations, and measured by the detector, is an indicator of the pressure applied.
• the detector measurement is relayed to the digitizer through wifi or Bluetooth communication, and a software application in the digitizer converts the change in intensity (pressure applied on the stylus) to the thickness of the stroke.
• the first embodiment of the invention takes advantage of the position measured by the digitizer, and thus the stylus is made pressure sensitive, using the change in optical fiber intensity.
• the pressure sensitive optical fiber sensor can be made with even one single optical fiber (as against the design described here, consisting of at least two fibers - one for transmitting laser from source to the reflector and the other for transmitting reflected light from the stylus head to the detector), which carries the light from the source, and the same fiber carries the reflected light from the reflecting surface.
• the different intensity detected by the six fibers can be used to calculate the angular tilt of the stylus.
• the stroke of a stylus (when writing a character) is then traced continuously by monitoring the different intensity from the six different fibers.
• the second embodiment of the invention thus can be used across any computer system, with or without a digitizer.
• the position of the stylus, with respect to the display, can then be measured, using any of the existing technology (using linear accelerator or using modified fiber optic mouse).
• Pressure sensitive styluses in the state of the art are either digitizer specific, or are not efficient when they are digitizer independent.
• the stylus proposed overcomes these shortcomings, and can be used across all kind of digitizers (resistive, capacitive, inductive optic). Further, the use of optical fiber sensor ensures that the stylus does not suffer from electromagnetic interference (EMI). The use of intensity modulated optical fiber sensor ensures that the stylus has very high pressure sensitivity. The response time of the stylus is only constrained by the detector rise time, and the wireless transmission. Thus, the stylus proposed implements a fast and high pressure sensitive stylus that can be used across all digitizers and does not suffer from (EMI).
• EMI electromagnetic interference
• ⁇ 200pm larger diameter fibers
• ⁇ 60pm standard fibers
• six fibers forming a hexagon is used for carrying the light.
• Such groups of fibers are called probes and are also used in imaging devices such as endoscopes and spectroscopy. This hexagonal configuration of fibers carries more back reflected light than a single fiber configuration.
• a hexagon group of fibers is used for sensing the pressure of the stylus touch. Unlike most intensity based fiber sensors, which measure only the total intensity of the reflected light, and merely to maximize the reflected light, this embodiment advantageously utilizes the ratio of the light collected through each channel of the fiber group.
• the present invention therefore presents a group of optical fibers housed in a tube which has a reflective stylus cap used for pressure sensitivity.
• the pressure sensitivity is defined as the pressure applied on the reflective stylus cap.
• the reflective cap acts as a sensor itself such that it deforms as a kind of deformable mirror in the form of a reflecting surface.
• the two principal embodiments according to the present invention comprises a first stylus having two fibers and a reflective cap to obtain a pressure sensitive stylus and a second stylus having multiple fiber and a reflective cap so as to obtain a pressure sensitive angle-measuring stylus.
• the first one depends on the strength of the light captured, and the second one depends on the different strengths captured by different fibers.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Human Computer Interaction (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

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• 2013
  • 2013-07-30 EP EP13752854.3A patent/EP3028124A1/de not_active Withdrawn
  • 2013-07-30 WO PCT/EP2013/065988 patent/WO2015014389A1/en active Application Filing

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