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Browse Prior Art Database

Shielding Method for a Digitizer Tablet

IP.com Disclosure Number: IPCOM000106132D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 122K

Publishing Venue

IBM

Related People

Benck, JW: AUTHOR [+5]

Abstract

Disclosed is a method for shielding a digitizer tablet, in which the work surface is shielded using a glass protective panel having an indium tin oxide coating. This method controls electromagnetic emissions that could otherwise increase radio frequency interference by coupling through the hand of a user operating the tablet with an active stylus.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Shielding Method for a Digitizer Tablet

      Disclosed is a method for shielding a digitizer tablet, in
which the work surface is shielded using a glass protective panel
having an indium tin oxide coating.  This method controls
electromagnetic emissions that could otherwise increase radio
frequency interference by coupling through the hand of a user
operating the tablet with an active stylus.

      A digitizer tablet is an input device with which information
may be provided to a data processing system, such as a personal
computer.  The tablet includes a work surface covering a grid of
wires.  Information is entered by the user through moving an
electronic stylus over the work surface.  The stylus contains an
electromagnet, which interacts with the grid of wires to produce
signals indicating stylus position.  A liquid crystal display (LCD)
assembly is placed over the grid of wires to present visual
information, including a trace of stylus movement, to the user.

      The Figure provides a fragmentary view of an edge portion of
the digitizer tablet, showing particularly the means used to shield
work surface 2, which forms a rectangular portion of the top of the
digitizer tablet, extending inward from four beveled edges 4
providing an aperture within an LCD sealing block 6.  The active
portions of the work surface include an LCD assembly 8 and a
digitizer assembly 10, within which the grid of wires (not shown) is
mounted.  A spacer 11 maintains the proper separation between the LCD
and digitizer assemblies.

      Various electronic components of the tablet are located within
a cavity 12 below the work surface, being effectively shielded by a
metal base 14, by a metal cover 16, and by a metal shield 18
extending under digitizer assembly 10.  Base 14 and cover 16 are
electrically connected by a conductive elastomeric insert 20, which
is compressed between these metal parts as they are brought together.

      The LCD assembly 8 includes a metal outer frame 21, which is
electrically connected to cover 16 by means of tin-plated beryllium
copper springs 22 extending along edges of assembly 8.  This
connection takes place through a number of cantilever tabs 24, which
extend upward as parts of springs 22 through slots 26 in LCD sealing
block 6, to contact an underside of upper surface 28 of cover 16.
Since the accuracy of the method used to detect stylus location is
easily...