Transcript Haptic Technology - La Salle University

Mouse, Touch Screen, Haptic
Technology
Mouse
• Invented by Doug Engelbart
• First commercial computer to come with a
mouse: Apple Macintosh 1984.
Mouse guts
Detecting X and Y motion
• As the ball rolls, two
wheels (rollers) pick up
the x- and y- components
of the motion.
• The roller moves a disk
which has spokes that
block light. A light and
light sensor can detect
the spokes as they go by
and thus perceive motion.
Connecting a mouse
Computer mice evolved from
connecting through the
Serial port, to a specialized
PS/2 connector, to a USB
connector.
Optical mouse
• Effectively produces images of the surface the
mouse in on.
• Then analyzes the difference in those images
from one time to the next in order to produce
the motion.
Some old ideas
• Since the mouse is producing consecutive
images, two old ideas come into play:
– Resolution – how many dots per inch (dpi) does
the mouse use in its image of the surface
– Refresh rate – how often is the mouse taking
images of the surface. Also related is how quickly
it can calculate the image differences and convert
them into motion.
Touch screens
• First developed by E.A. Johnson at the Royal
Radar Establishment, Malvern, UK.
• First was “capacitive”.
• Until recently could detect only a single touch
with little to no information about the amount
of pressure, etc.
A capacitor
A capacitor
• A capacitor consists of two conducting plates
separated by a non-conductor.
• One plate gets a positive charge and the other
a negative charge.
• Among other things, the electrical properties
of a capacitor is determined by the space
between the plates.
Capacitive touch screen
• In a capacitive touch screen there is one
“plate” – for example, a thin layer of ITO
(Indium Tin Oxide) chosen for its transparency.
• The second conducting plate is the user’s
finger or conductive stylus – its presence
forms a capacitor.
• Various techniques are used to determine
where the touching occurs.
Resistive touch screen
• A resistive touch screen has two layers and the
pressure of the user’s touch moves the two
layers closer changing the capacitor’s
properties.
• The user can wear gloves or use almost any
kind of stylus.
SAW
• Surface Acoustic Wave (SAW) sends out an
ultra-sonic wave over the screen.
– As we know the human hearing range goes up to
20-some kHz (20,000 Hz). Vibrational waves with
higher frequencies are said to be ultrasonic
• When the screen is touch part of the ultrasonic wave is absorbed.
• The detection of where the wave is absorbed
determines where the screen was touched.
Infrared/Optical Imaging
• A crisscross of beams (usually in the infrared
spectrum) is sent across the display surface
and detected on the opposite side.
• The user’s finger or stylus disrupts some of the
beams and can thus be detected.
• Like resistive, no properties of the touching
object are assumed (beyond opaqueness to
infrared).
Dispersive signal technology and
acoustic pulse recognition
• Dispersive signal technology: The stresses,
strains etc. of the surface are detected at its
edges and reverse engineered to determine
where the screen was touched.
• Acoustic pulse recognition: piezo-electrics
(material where pressure and electric
properties are coupled) are placed
throughout. Pressures cause signals which can
then determine location of touch
Haptic definition
Tactile Feedback to User
• Touch screens and mice allow the user to put
information into the system, but some
systems provide tactile feedback, from letting
your finger “know” it has clicked something to
a more encompassing attempt to make a
virtual experience feel real.
Grasping haptics
• Early machines (not computers) allowed a
user to interact with a control to grasp objects
far away
– For convenience
– For added strength of machine
– For protection from dangerous situation
Variations
• Haptics: science of touch
• Human haptics: specialized to human touch
• Machine haptics: providing “touch” feedback
that allows a user to control a real object via a
machine (may include a computer)
• Computer haptics: provides “touch” feedback
that allows a user to experience a virtual
object
First “computer haptics”
• In 1993, the MIT Artificial Intelligence
Laboratory made a device that gave a user
haptic feedback – making it possible to touch
a virtual object.
Type 1: Kinesthetic
From HowStuffWorks
• “Known as proprioceptors, these receptors carry
signals to the brain, where they are processed by the
somatosensory region of the cerebral cortex. The
muscle spindle is one type of proprioceptor that
provides information about changes in muscle
length. The Golgi tendon organ is another type of
proprioceptor that provides information about
changes in muscle tension. The brain processes this
kinesthetic information to provide a sense of the
baseball's gross size and shape, as well as its position
relative to the hand, arm and body.”
Type 2: Tactile
Force Feedback
Haptic rendering
• A way of calculating how a user is interacting
with a virtual system and in turn what haptic
feedback should be given to the user is known
as “haptic rendering”.
References
• http://computer.howstuffworks.com/mouse.h
tm
• http://en.wikipedia.org/wiki/Touchscreen
• http://electronics.howstuffworks.com/gadgets
/other-gadgets/haptic-technology.htm
• http://arstechnica.com/gadgets/2013/04/fro
m-touch-displays-to-the-surface-a-briefhistory-of-touchscreen-technology/