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Book ChapterDOI

Exploring Fingers’ Limitation of Texture Density Perception on Ultrasonic Haptic Displays

13 Jun 2018-Vol. 10893, pp 354-365

TL;DR: Psychophysical experiments to investigate the perceptual threshold of individual fingers on both the right and left hand of right-handed participants using active dynamic touch for spatial period discrimination of both sinusoidal and square-wave gratings on ultrasonic haptic touchscreens indicate that users’ finger identity significantly affect the perception of both gratings in the case of one-finger exploration.
Abstract: Recent research in haptic feedback is motivated by the crucial role that tactile perception plays in everyday touch interactions. In this paper, we describe psychophysical experiments to investigate the perceptual threshold of individual fingers on both the right and left hand of right-handed participants using active dynamic touch for spatial period discrimination of both sinusoidal and square-wave gratings on ultrasonic haptic touchscreens. Both one-finger and multi-finger touch were studied and compared. Our results indicate that users’ finger identity (index finger, middle finger, etc.) significantly affect the perception of both gratings in the case of one-finger exploration. We show that index finger and thumb are the most sensitive in all conditions whereas little finger followed by ring are the least sensitive for haptic perception. For multi-finger exploration, the right hand was found to be more sensitive than the left hand for both gratings. Our findings also demonstrate similar perception sensitivity between multi-finger exploration and the index finger of users’ right hands (i.e. dominant hand in our study), while significant difference was found between single and multi-finger perception sensitivity for the left hand.
Topics: Middle finger (66%), Index finger (66%), Haptic perception (66%), Tactile perception (60%), Little finger (54%)

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Exploring Fingers’ Limitation of Texture Density
Perception on Ultrasonic Haptic Displays
Farzan Kalantari, David Gueorguiev, Edward Lank, Nicolas Bremard, Laurent
Grisoni
To cite this version:
Farzan Kalantari, David Gueorguiev, Edward Lank, Nicolas Bremard, Laurent Grisoni. Exploring
Fingers’ Limitation of Texture Density Perception on Ultrasonic Haptic Displays. EuroHaptics 2018
- 11th International Conference on Haptics: Science, Technology, and Applications, Jun 2018, Pisa,
Italy. �hal-01837910�

Exploring Fingers’ Limitation of Texture Density
Perception on Ultrasonic Haptic Displays
Farzan Kalantari
1
, David Gueorguiev
2
, Edward Lank
3
, Nicolas Bremard
1
, and
Laurent Grisoni
1
1
University of Lille - Science & Technology, CNRS, Lille, France
farzan.kalantari@ed.univ-lille1.fr, nicolas.bremard@inria.fr,
laurent.grisoni@univ-lille1.fr
2
Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
dgueorguiev@is.mpg.de
3
University of Waterloo, Waterloo, Canada
lank@uwaterloo.ca
Abstract. Recent research in haptic feedback is motivated by the cru-
cial role that tactile perception plays in everyday touch interactions.
In this paper, we describe psychophysical experiments to investigate the
perceptual threshold of individual fingers on both the right and left hand
of right-handed participants using active dynamic touch for spatial pe-
riod discrimination of both sinusoidal and square-wave gratings on ultra-
sonic haptic touchscreens. Both one-finger and multi-finger touch were
studied and compared. Our results indicate that users’ finger identity
(index finger, middle finger, etc.) significantly affect the perception of
both gratings in the case of one-finger exploration. We show that index
finger and thumb are the most sensitive in all conditions whereas little
finger followed by ring are the least sensitive for haptic perception. For
multi-finger exploration, the right hand was found to be more sensitive
than the left hand for both gratings. Our findings also demonstrate simi-
lar perception sensitivity between multi-finger exploration and the index
finger of users’ right hands (i.e. dominant hand in our study), while sig-
nificant difference was found between single and multi-finger perception
sensitivity for the left hand.
Keywords: Haptic display; Tactile perception; Ultrasonic vibration; Fin-
ger sensitivity; Spatial texture density
1 Introduction
Current commercial touchscreen devices rarely provide a compelling haptic feed-
back to human fingers despite the use of touch as input; haptic feedback is
typically limited to vibration. As Buxton et al. [5] investigated in 1985, flat
touchscreens need haptic feedback in order to ease end users’ common interac-
tion tasks, to enhance the efficiency of interfaces, and to increase the realism of
visual environments. Therefore, researchers have explored different technologies
to generate dynamic haptic feedback to enhance input on touchscreen devices.

2 Farzan Kalantari et al.
Within this space of dynamic haptic effects, different technologies are commonly
used. First, vibrotactile actuators such as solenoids, vibrotactile coils, and ERM
motors can be utilized for tactile rendering on touchscreens as discussed in [6].
These actuators are used presently on smartwatches, mobile phones and tablets,
but typically provide for on-or-off sensation. Alongside vibrotactile actuation,
two techniques, electrostatic-vibration [2, 18] and electroadhesion [22] use elec-
trostatic force generated, respectively, by applying a voltage to the screen sur-
face or by applying DC excitation of the tactile display. Both of these techniques
increase the friction between the finger and the interaction surface when acti-
vated, thus varying the perceived stickiness of the surface. Finally, a fourth type
of haptic feedback leverages ultrasonic vibrations to create an air-gap between
a user’s finger and the display to reduce friction when activated, a phenomenon
called the “squeeze film effect” [4, 1, 7, 28]. In the remainder of this paper, we are
particularly interested in the user’s tactile perception of the latter technology.
It is well-documented in literature that the human sense of touch has a
fundamental role in the haptic perception of different surfaces. Touch is quite
sensitive in perceiving different materials [10] and textures [16], and we leverage
this sensitivity in haptic effects by taking into account its fundamental limits
[23]. The texture perception of the human sense of touch remains a complex
phenomenon which varies between different people and is mediated by the user’s
fingers’ mechanoreceptors [21].
This complexity of touch perception has resulted in various investigations
to better understand and explore haptic perception difficulties, particularly on
tactile surfaces. Yoshioka et al. [29] have shown that the neural mechanisms
underlying texture perception of a variety of real textured surfaces and objects
differ between direct touch (through a finger) and indirect touch (through a
probe). Hughes et al. [12] investigated participants’ abilities to discriminate spa-
tial density gradients of different textures. Nefs et al. [20] measured discrimi-
nation thresholds for sinusoidal gratings using active dynamic touch and found
that amplitude differences as small as 2 µm can be detected with spatial periods
between 0.25 and 1 cm. Verrillo et al. [25] studied the relationship between vibra-
tion frequency and perceived intensity of the stimuli and showed that it obeys a
power law function with an exponent of 0.89 for frequencies under 350 Hz. Wi-
jekoon et al. [27] demonstrated that there are significant correlations between
intensity perception and signal frequency and amplitude of texture waveform for
texture perception on electrovibration haptic displays, and the highest sensitivity
was found at a frequency of 80 Hz.
In the case of tactile perception of ultrasonic haptic displays, those that
leverage the squeeze film effect, several studies have also been performed on
touch perception. Biet al. [3] studied the differential sensory thresholds for the
spatial periods of real and virtual square-wave gratings on an ultrasonic haptic
plate. Kalantari et al. [14] studied the limitation of tactile elements for texture
perception and how to optimize interaction performance of end users through
the perception of different haptic effects [15], as well as how tactile and auditory
signals can be combined to enhance the user’s spatial perception in musical

Title Suppressed Due to Excessive Length 3
interactions on ultrasonic displays [13]. Gueorguiev et al. [9, 11] investigated the
tactile perception of transient changes of different frictional signals on ultrasonic
based haptic devices.
Despite all of this work, however, in all of the mentioned studies only one
finger (index in most cases) for texture perception of tactile surfaces has been
examined; we are aware of no work that has contrasted finger sensitivity, nor any
work that explores single versus multi-finger sensitivity. Given that single-touch
interaction need not be limited to the index finger, and given the prevalence of
multi-touch as an input paradigm on touch screens, one can ask the followings:
Do we have identical texture perception among all our fingers and hands while
interacting with a haptic display? Do we have the same sensory threshold for
perceiving different kind of textures? What are the differences between the tactile
perception of one-finger and multi-finger explorations on haptic displays? In this
paper, we explore the limitation of individual human fingers and different hands
on texture density perception in the case of two waveform types for ultrasonic-
based haptic displays.
2 Experiment
We carried out a psychophysical experiment to explore the limitations of touch
perception of different finger types (index, middle, etc.) in dynamic active touch.
We investigated both single and multi-finger tactile explorations of sinusoidal and
square-wave textures on ultrasonic-based tactile displays. In this study, texture
is defined as the sequence of periodic haptic feedback effects generated by a
specific type of signal waveform (such as square or sine) and accordingly its
specific value of spatial period and amplitude. We have investigated the spatial
period of determined textures (with a constant amplitude of 1.25 µm peak to
peak) which can be accurately perceivable by participants.
The experiment conformed to the principles of the Declaration of Helsinki
and a general explanation of the experimental task was given to each participant
before beginning the experimental procedure.
2.1 Participants
Fifteen healthy volunteers (5 females) from the age of 22 to 34 with a mean age
of 28.4 (SD=3.48) took part in our experiment. By design, all of the participants
were right-handed. The total experiment time was 50-60 minutes for each par-
ticipant. Participants wore active noise-cancelling headphones (Panasonic RP-
DJS200, Japan) during the experiment, while Gaussian white noise was played
at a comfortable listening level in order to prevent potential interference from
external auditory cues.
2.2 Experimental set-up
We used an enhanced visual-tactile actuator (E-ViTa), a tactile feedback display
based on ultrasonic vibrations for haptic rendering [26]. E-ViTa is developed

4 Farzan Kalantari et al.
on a Banana Pi, a single-board computer (Shenzhen LeMaker Technology Co.
Ltd, China) with a 1 GHz ARM Cortex-A7, dual-core CPU and 1 GB of RAM
working in parallel with STM32f4 microcontroller (STMicroelectronics, France).
The communication between the microcontroller and the single board computer
is provided via the Serial Peripheral Interface (SPI) bus at 10 kHz. This single-
board computer is connected to a 12.5cm capacitive touchscreen (Banana-LCD
5"-TS, MAREL, China) for detecting the user’s finger position on the display
with a sampling frequency of 62 Hz.
Ten 14 × 6 × 0.5 mm piezoelectric cells actuate a 154 × 81 × 1.6 mm fixed glass
plate, resonating at 60750 Hz with a half wavelength of 8 mm. A power electronic
circuit converts a 12V DC voltage source into an AC voltage, controlled in am-
plitude and frequency and supplied to the piezoelectric cells. The microcontroller
synthesizes a pulse-width modulation (PWM) signal to drive a voltage inverter
that actuates the piezoceramics. The detailed structure of E-ViTa haptic display
is illustrated in figure 1.
Fig. 1: Structure of the E-Vita ultrasonic based haptic display used in our ex-
periment [26]
2.3 General procedure
A one-up-one-down staircase procedure (adaptive procedure) with fixed step sizes,
commonly used in psychophysics [24, 17] was used in our investigation. In this
procedure the stimulus level at any trial is determined by the previous response
of a participant. The 1-up-1-down staircase procedure offers the compelling ad-
vantage of reducing the total time of our experiment, since we investigate a high
number of trials and conditions for each participant.
The stimuli consisted of textures with sinusoidal and square wave gratings,
which were tested on all fingers of both hands. Tactile exploration was also
performed with the right and left hands (multi-finger exploration) for the two
types of gratings. In the latter experimental situation, the participants were
asked to use all their fingers except thumb in order to have sufficient active
region of haptic feedback on the E-ViTa 5" display. The procedure for each

Figures (7)
Citations
More filters

06 May 2016
TL;DR: This result demonstrates that differences in interfacial mechanics between the finger and a material can be sensed by touch and that the evanescent mechanics that take place before the onset of steady slip have perceptual value.
Abstract: In a forced-choice task, we asked human participants to discriminate by touch alone glass plates from transparent polymethyl methacrylate (PMMA) plastic plates. While the surfaces were flat and did not exhibit geometric features beyond a few tens of nanometres, the materials differed by their molecular structures. They produced similar coefficients of friction and thermal effects were controlled. Most participants performed well above chance and participants with dry fingers discriminated the materials especially well. Current models of tactile surface perception appeal to surface topography and cannot explain our results. A correlation analysis between detailed measurements of the interfacial forces and discrimination performance suggested that the perceptual task depended on the transitory contact phase leading to full slip. This result demonstrates that differences in interfacial mechanics between the finger and a material can be sensed by touch and that the evanescent mechanics that take place before the onset of steady slip have perceptual value.

1 citations


Journal ArticleDOI
Abstract: Electrovibration holds great potential for creating vivid and realistic haptic sensations on touchscreens. Ideally, a designer should be able to control what users feel independent of the number of fingers they use, the movements they make, and how hard they press. We sought to understand the perception and physics of such interactions by determining the smallest 125 Hz electrovibration voltage that 15 participants could reliably feel when performing four different touch interactions at two normal forces. The results proved for the first time that both finger motion and contact by a second finger significantly affect what the user feels. At a given voltage, a single moving finger experiences much larger fluctuating electrovibration forces than a single stationary finger, making electrovibration much easier to feel during interactions involving finger movement. Indeed, only about 30% of participants could detect the stimulus without motion. Part of this difference comes from the fact that relative motion greatly increases the electrical impedance between a finger and the screen, as shown via detailed measurements from one individual. By contrast, threshold-level electrovibration did not significantly affect the coefficient of kinetic friction in any conditions. These findings help lay the groundwork for delivering consistent haptic feedback via electrovibration.

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TL;DR: This tutorial focuses on the sense of touch within the context of a fully active human observer and describes an extensive body of research on “what” and “where” channels, the former dealing with haptic perception of objects, surfaces, and their properties, and the latter with perception of spatial layout on the skin and in external space relative to the perceiver.
Abstract: This tutorial focuses on the sense of touch within the context of a fully active human observer. It is intended for graduate students and researchers outside the discipline who seek an introduction to the rapidly evolving field of human haptics. The tutorial begins with a review of peripheral sensory receptors in skin, muscles, tendons, and joints. We then describe an extensive body of research on “what” and “where” channels, the former dealing with haptic perception of objects, surfaces, and their properties, and the latter with perception of spatial layout on the skin and in external space relative to the perceiver. We conclude with a brief discussion of other significant issues in the field, including vision-touch interactions, affective touch, neural plasticity, and applications.

687 citations


"Exploring Fingers’ Limitation of Te..." refers background in this paper

  • ...Touch is quite sensitive in perceiving different materials [10] and textures [16], and we leverage this sensitivity in haptic effects by taking into account its fundamental limits [23]....

    [...]


Proceedings ArticleDOI
03 Oct 2010
TL;DR: The proposed technology is based on the electrovibration principle, does not use any moving parts and provides a wide range of tactile feedback sensations to fingers moving across a touch surface, which enables the design of a wide variety of interfaces that allow the user to feel virtual elements through touch.
Abstract: We present a new technology for enhancing touch interfaces with tactile feedback. The proposed technology is based on the electrovibration principle, does not use any moving parts and provides a wide range of tactile feedback sensations to fingers moving across a touch surface. When combined with an interactive display and touch input, it enables the design of a wide variety of interfaces that allow the user to feel virtual elements through touch. We present the principles of operation and an implementation of the technology. We also report the results of three controlled psychophysical experiments and a subjective user evaluation that describe and characterize users' perception of this technology. We conclude with an exploration of the design space of tactile touch screens using two comparable setups, one based on electrovibration and another on mechanical vibrotactile actuation.

673 citations


"Exploring Fingers’ Limitation of Te..." refers methods in this paper

  • ...Alongside vibrotactile actuation, two techniques, electrostatic-vibration [2, 18] and electroadhesion [22] use electrostatic force generated, respectively, by applying a voltage to the screen surface or by applying DC excitation of the tactile display....

    [...]


Journal ArticleDOI
Marjorie R. Leek1Institutions (1)
TL;DR: The general development of adaptive procedures is described, and typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed.
Abstract: As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each trial are determined by the stimuli and responses that occurred in the previous trial or sequence of trials. In this paper, the general development of adaptive procedures is described, and three commonly used methods are reviewed. Typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed. Results of simulations and experiments with human subjects are reviewed to evaluate the utility of these adaptive procedures and the special circumstances under which one might be superior to another.

662 citations


"Exploring Fingers’ Limitation of Te..." refers methods in this paper

  • ...A one-up-one-down staircase procedure (adaptive procedure) with fixed step sizes, commonly used in psychophysics [24, 17] was used in our investigation....

    [...]


Journal ArticleDOI
Bernhard Treutwein1Institutions (1)
TL;DR: This review tries to illuminate the historical background of adaptive procedures, explain their differences and similarities, and provide criteria for choosing among the various techniques.
Abstract: Improvements in measuring thresholds, or points on a psychometric function, have advanced the field of psychophysics in the last 30 years. The arrival of laboratory computers allowed the introduction of adaptive procedures, where the presentation of the next stimulus depends on previous responses of the subject. Unfortunately, these procedures present themselves in a bewildering variety, though some of them differ only slightly. Even someone familiar with several methods cannot easily name the differences, or decide which method would be best suited for a particular application. This review tries to illuminate the historical background of adaptive procedures, explain their differences and similarities, and provide criteria for choosing among the various techniques.

593 citations


"Exploring Fingers’ Limitation of Te..." refers methods in this paper

  • ...A one-up-one-down staircase procedure (adaptive procedure) with fixed step sizes, commonly used in psychophysics [24, 17] was used in our investigation....

    [...]


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William Buxton1, Ralph Hill1, Peter Rowley1Institutions (1)
01 Jul 1985
Abstract: Touch-sensitive tablets and their use in human-computer interaction are discussed. It is shown that such devices have some important properties that differentiate them from other input devices (such as mice and joysticks). The analysis serves two purposes: (1) it sheds light on touch tablets, and (2) it demonstrates how other devices might be approached. Three specific distinctions between touch tablets and one button mice are drawn. These concern the signaling of events, multiple point sensing and the use of templates. These distinctions are reinforced, and possible uses of touch tablets are illustrated, in an example application. Potential enhancements to touch tablets and other input devices are discussed, as are some inherent problems. The paper concludes with recommendations for future work.

351 citations