tactile displays
DESCRIPTION
Tactile Displays. Kaczmarek, K.A. and Bach-Y-Rita, P. (1995), Tactile displays, in Virtual Environments and Advanced Interface Design , Barfield and Furness, pp. 349-414. Summarized by Geb Thomas. Your 2m 2 of skin. 90% hairy, 10% glabrous (hairless) Accessible Richly innervated - PowerPoint PPT PresentationTRANSCRIPT
Tactile Displays
Kaczmarek, K.A. and Bach-Y-Rita, P. (1995), Tactile displays, in Virtual Environments and
Advanced Interface Design, Barfield and Furness, pp. 349-414.
Summarized by Geb Thomas
Your 2m2 of skin
90% hairy, 10% glabrous (hairless) Accessible Richly innervated Precise discrimination Adaptable to spatial and temporal displays
Covered Here
Present and potential applications
Mechanisms of normal touch perception
Technology for producing tactile displays
Practical considerations
Traditional displays for the blind
Braille (6-dot matrix, 2.3mm separation,
125 words*min-1)
Sign language: finger spelling: 6 letters*
sec-1, American Sign Language: 4-5
syllables*sec-1)
Tadoma 3 syllables*sec-1
Tactile Feedback from tactile sensors For people with poor haptic perception in their
hands (Hansen’s disease, suited astronauts) strain guages on a glove to forhead electrodes:
can detect shape and texture! Movable pins, enhanced fingerpads, tactile
pads, glove-hand adhesion, removable glove fingertip
Sample task: no feedback: 92s, force feedback 63s, barehanded: 14s
Tactile auditory substitution
Auditory prosthesis which adjusts the perceived intensity of 16 electrodes, each corresponding to the sound intensity of a given passband in the audio spectrum.
Improve speech clarity for deaf children Improve auditory discrimination and
comprehension in older patients
Tactile vision substitution (TVS)
Television Camera to users skin with a vibrotactile or electrotactile stimulators array.
Stimulation intensity is controlled by grayscale
Distal attribution -- with practice, user perceives the stimulation to be in front of them
Tactile Reading
Optacon 6x24-row vibrating fingerpad 90 words*min-1 exceptional 28 words*min-1
normal Now discontinued Significant underground calling for its
resurgance
Static tactile displays
64-solenoid, four level display presenting graphical information
Another model has one prime mover and many piezoelectric latches
Muscle wire display
Virtual tactile tablet
Fingerpad vibrotactile stimulation array on a mouse
5x20 array of pin vibrotactors mounted directly above t-shaped mouse
Minsky’s sandpaper display
Human Tactile Perception
Six types of cutaneous receptors, four functions– Fast adapting, broad receptive field (FAII) --
high-frequency vibration– Fast adapting, small receptive field (FAI) --
localized movement fine form and texture– Slow adapting, large-field (SAII) -- maybe not
involved in haptics– Slow adapting, small-field (SAI) -- form and
roughness
Measures
Smallest amount of pressure Two-point limen (two point discrimination
threshold TPDT) Affected by location, practice, fatigue,
distraction Modeling attempts include convolving
integral, low-pass filter or Gaussian blur
Design Criteria
Static tactile displays Vibrotactile displays Electrotactile displays
Static
High power consumption Rapid adaptation to static stimuli 12-20mm height to match Optacon
accuracy
Vibrotactile
Threshold: 5 micro-m at 25-650 Hz for small areas (<.05 cm2)
Adaptation to strong stimuli Full recovery requires 2 min. 160 Hz is best 10dB over threshold 1 mm diameter stimulator with .5mm
movement
Electrotactile Displays
Current through skin Current-limited Balanced, biphasic pulses with zero net DC
current Electrodes to produce appropriate ions (gold,
platinum, silver) Electrode size is important Some are implantable
Important Issues
Pain threshold Skin condition Sensory adaptation Subjective magnitude of electrotactile
stimulation