Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1998-10-21
2004-05-04
Hjerpe, Richard (Department: 2774)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S177000, C345S179000, C345S175000, C345S176000, C178S018060, C178S018070, C178S018010, C178S018020, C178S018030, C178S018040, C178S018050, C178S019010, C178S019020, C178S019030, C178S019040, C178S019050, C178S019060
Reexamination Certificate
active
06731270
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of electromechanical transducers. More particularly, the invention relates to a piezoelectric transducer for a data entry device.
BACKGROUND OF THE INVENTION
Electromechanical transducers are used for a variety of applications, including data entry applications such as digitizing pen-and-tablet systems. Data entry systems typically include a writing area, such as a tablet or white board, a position indicating pen, and associated electronics for determining the interaction between the position-indicating pen and the writing area. A digital data entry signal is typically derived to represent the relative position of the position-indicating pen and the tablet.
Ultrasound-based electronic tablets and whiteboards are based on either through-the-air transmission (air transmission) or through-the-surface-of-the-board (solid transmission) of ultrasonic pulses. The position of a movable data-entry device on the writing surface is calculated, typically by the geometric intersection of travel times of ultrasonic pulses measured between the data-entry device and a plurality of fixed-location sensor stations, which are located on the periphery of the writing area. Full coverage of a writing area, such as a tablet or a whiteboard, typically requires a minimum of two fixed-location sensors, and one movable sensor for geometric triangulation.
The actual number of required sensors depends on the radiation angle of the ultrasound transmitter or transmitters (the transmission directivity), the strength of the transmitted signal, the acceptance angle of the ultrasound receivers (the reception directivity), and the sensitivity of the receivers to the vibrational frequency of the transmitted pulses.
Many prior art tablets or writing surfaces which use pen shaped data-entry devices are based on touch-panel technologies. Typically, complicated grid layers extend across the surface, and are held apart by tension underneath the writing surface. The location of a data-entry device, such as a data-entry pen, is determined by the location at which the pen presses the grid layers together. Ibid™ whiteboard from Microtouch, of Methuen, Mass., the SmartBoard™ from Microfield Graphics, of Calgary, Alberta, Canada, and pen-based digitizing tablets from Wacom Co, Ltd., of Saitama, Japan are examples of touch-panel technology electronic whiteboards.
A drawback of touch-panel prior art tablets and whiteboards is that the writing surface is an integral component of the system. As the size of the writing area increases, their portability, ease of installation, and product cost become increasingly problematic.
S. Sindeband, and T. Stone,
Position Determining Apparatus
, U.S. Pat. No. 5,379,269 (Jan. 3, 1995) disclose an apparatus for determining the position of a movable element over a surface of a solid medium. Sindeband et al. describe an electronic whiteboard system which uses ultrasound to determine the position of a pen-shaped stylus on a writing surface. While Sindeband et al. disclose a movable transmitter, the transmitted ultrasonic energy is required to travel through a solid medium. To obtain a consistent signal through a solid medium, therefore, the transmission characteristics of the solid surface must be uniform.
The establishment of a large homogenous writing structure can be difficult and expensive, and precludes the use of the transmitter pen on a generic surface, such as a white board. Standard white boards are not homogenous structures, typically having a common particle board or Masonite™ composite backing, with an applied top surface that typically has non-uniform surface characteristics.
Therefore, an electronic whiteboard based on the principles of operation disclosed by Sindeband et al. would require that a special whiteboard writing surface be included in the product cost. As well, Sindeband et al. disclose a tethered movable stylus, wherein a transmitter is acoustically coupled to the solid medium, which precludes a writing tip within the stylus.
Despite these drawbacks, prior art grid-based tablets and whiteboards typically include data-entry devices which have the look and feel of a pen, and they are designed to be gripped and used like a pen. The user is not required to orient the data-entry device in any special manner.
Ultrasound-based electronic whiteboards that rely on through-the-air transmission of ultrasound pulses, rather than transmission through the solid medium of the whiteboard, offer the opportunity for a product which excludes a dedicated whiteboard writing surface. As an example of such an implementation, an ultrasound transmitter can be located in the movable, pen-style data-entry device. A fixed-position array of ultrasound receivers is located along the periphery of the writing surface. These sensors are used to triangulate the position of the data-entry device on the surface of the whiteboard. The receivers are typically attached directly to a whiteboard, or are mounted to a frame, which is then attached to a whiteboard or other approximately flat writing surface.
Optimally, a sensor for a pen-shaped data-entry device has a transmission directivity that is omni-directional from the writing tip, thus providing cylindrical symmetry to the transmitted signal, which allows the user to hold the device as any pen would be held, without the need to orient a sensor located on the data-entry device toward other receiving sensors located at the periphery of the writing surface.
In the past, most working examples of omnidirectional ultrasonic transmitters were based on spark-gap designs. L. Roberts, “
The Lincoln Wand
”, MIT Lincoln Lab Report, Lexington Mass., June 1966, and P. De Bruyne, “
Compact Large-Area Graphic Digitizer for Personal Computers
”, Dec. 1986, pp 49-53, IEEE, disclosed examples of spark-gap data-entry devices for electronic whiteboards.
One significant drawback of spark-gap transmitters is the audible, repeated “snap” sound associated with the generation of ultrasound pulses. Another significant drawback with spark-gap transmitters is high power consumption, which makes untethered battery-powered operation impractical, since batteries must be changed or recharged on a frequent basis.
As well, spark gap transmitters typically have a transmitter tip that resides on the entire pointing tip of the movable device. The mechanism for producing a spark gap signal has to act as a point source, requiring that the end of the transmitter pen is used as an acoustic horn. This hardware configuration prevents the use of a writing tip, such as a standard writing implement or pen cartridge, from being placed within the device, with a writing tip extending from the pointing tip of the device, as such that a user can write upon a surface, such as a white board, while simultaneously sending a position signal from the pointing tip to external receivers.
R. Herrington and K. Burgess,
Wireless Cursor Control System
, U.S. Pat. No. 4,654,648 (Mar. 31, 1987) disclose a “wireless movable steering means which emits acoustic signals”. While Herrington et al. disclose a movable transmitter stylus, the spark gap mechanism inherently precludes the use of a writing pen within the pointing tip of the hand-held stylus.
Similarly, A. Whetstone, S. Fine, W. Banks, and S. Phillips,
Graphical Data Device
, U.S. Pat. No. 3,838,212 (Jan. 3, 1995) disclose a graphical data device employing a stylus moving over an area to be digitized and utilizing a fast rise time sound energy shock, generated by a spark at the location of the stylus and propagated though the air.
R. Davis and J. Howells,
Position Determining Apparatus and Transducer Therefor
, U.S. Pat. No. 4,012,588 (Mar. 15, 1977) disclose an apparatus for determining the position of a movable element, wherein “each receiver comprises a hollow shell of piezoelectric material, which may be cylindrical or spherical in shape, and resilient conductive means coupled across the inner and outer surface of the shell”. While Davis et al. disclose a cylindrical symmetry for a complicated, statio
Dov Rosenfeld Inventek
Hjerpe Richard
Lesperance Jean
Luidia Inc.
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