Browse Prior Art Database

Optical Contact Sensor for Input Stylus

IP.com Disclosure Number: IPCOM000103976D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Garwin, RL: AUTHOR [+3]

Abstract

A stylus contact sensor for computer input of handwritten material is disclosed. The sensor makes use of frustrated internal reflection to sense contact force between the stylus and writing surface. The operating force is below 20 grams and longitudinal motion is imperceptible, giving the stylus a natural feel.

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Optical Contact Sensor for Input Stylus

      A stylus contact sensor for computer input of handwritten
material is disclosed.  The sensor makes use of frustrated internal
reflection to sense contact force between the stylus and writing
surface.  The operating force is below 20 grams and longitudinal
motion is imperceptible, giving the stylus a natural feel.

      The principle of the device is illustrated in Figures 1 and 2A.
Light from emitter 1 is incident on the flat side 2 of a transparent,
shown in top, end, and side views in Figures 1a through 1c
respectively, and in perspective in Figure 1d.  The top surface is
embossed with vee-grooves 3.  The angle of incidence of the light on
the inside surfaces of the grooves is such that it undergoes total
internal reflection (TIR), following the dashed lines of Figures 1b
and 1c to reach optical detector 4.

      TIR is substantially decreased if an absorbing material makes
intimate contact with the reflecting surface.  Figure 2a  illustrates
the construction of a force sensor, in which a rubbery material 6 is
pressed against the grooves  7.  The area of contact between the
rubber and the grooves increases with the applied force,
progressively lowering the optical coupling between emitter and
sensor.

      A complete contact sensor is shown in Figure  2b.  The contact
force is applied to rubber pad 8 from push-rod 9, which serves as the
tip of the stylus.  The push-rod is  made of a low-friction...