Dianne T. V. Pawluk

Haptic Perception of Material Properties and Implications for Applications

Perceiving the material properties of objects through touch is generally superior to the perception of shape. We review major material properties accessible through haptic interaction, along with theoretical accounts of the underlying perceptual processes. These include roughness, friction, compliance, and thermal properties. Subsequently, we describe algorithms that have been used to render these same material properties on haptic devices. We then point to applications that have capitalized on the accessibility of material through touch, including tactile displays, simulation of mechanical mechanisms in the automobile, and medical training simulators.

Issues of Using Tactile Mice by Individuals Who Are Blind and Visually Impaired

Tactile mice, computer mice modified to have tactile pin displays on their upper surface, have been developed to enable access to 2-D graphical information for individuals who are blind or visually impaired; however, they have yet to really be adopted by the community. We suggest that this is due to the significant lack of accuracy in the haptic position information, which is critical for individuals to haptically piece together a 2-D graphic. We have identified two main design issues that affect this accuracy. Making simple modifications to correct these problems, we show a significant improvement in performance.

An improved, low-cost tactile 'mouse' for use by individuals who are blind and visually impaired

Although tactile mice, such as the VT Player by virTouch, have been developed to enable access to 2-D graphical information by individuals who are blind and visually impaired, they have yet to really be adapted by the community. We suggest that this is due to the significant lack of accuracy in the haptic position information, which is critical for individuals to haptically piece together a 2-D graphic. In addition, the VT Player suffers from a noticeable lack of spatial and temporal concordance between the kinesthetic and tactile information. In this paper, we present a low-cost (<400 US) alternative that avoids these problems. Furthermore, the dynamic response of the pins of our improved mouse can range from 0 to > 300Hz. This will facilitate the use of vibration and texture, which our preliminary results show improves the saliency of graphical information.

Designing Haptic Assistive Technology for Individuals Who Are Blind or Visually Impaired

This paper considers issues relevant for the design and use of haptic technology for assistive devices for individuals who are blind or visually impaired in some of the major areas of importance: Braille reading, tactile graphics, orientation and mobility. We show that there is a wealth of behavioral research that is highly applicable to assistive technology design. In a few cases, conclusions from behavioral experiments have been directly applied to design with positive results. Differences in brain organization and performance capabilities between individuals who are “early blind” and “late blind” from using the same tactile/haptic accommodations, such as the use of Braille, suggest the importance of training and assessing these groups individually. Practical restrictions on device design, such as performance limitations of the technology and cost, raise questions as to which aspects of these restrictions are truly important to overcome to achieve high performance. In general, this raises the question of what it means to provide functional equivalence as opposed to sensory equivalence.

Using multiple contacts with texture-enhanced graphics

We present a multi-finger 2-D haptic display device to potentially provide the opportunity of parallel processing of coarse haptic information, with the intended benefit of improving performance in 2-D haptic object recognition. Combined with a novel method for producing “texture” image representations, we found that multiple contacts does improve performance compared to a single contact in terms of both time and accuracy. However, we also found no benefit for additional contacts with only raised-line representations of objects. This suggests that the use of texture made a key contribution in improving performance from one to multiple fingers.

A cheap, portable haptic device for a method to relay 2-D texture-enriched graphical information to individuals who are visually impaired

This paper considers the development of a haptic device needed for a method of relaying 2-D texture enriched graphical information. The focus here is on the conversion of the optical, color-based representation of the formatted diagram, which is efficient for storage and distribution, to its haptic texture enriched form. For this, the device has two main components, an RGB color sensor and piezoelectric actuator, mounted in a casing that is wrapped around the finger. The resulting device has a spatial sensitivity (<2mm) comparable to natural touch (1.0mm), a temporal frequency bandwidth of 1 to 200 Hz, and can be used to output a variety of textures. The point contact device developed can also easily be expanded to the use of multiple devices on multiple fingerpads, while remaining affordable (<100) and portable (<500g).

Displaying braille and graphics on a mouse-like tactile display

For presenting graphics on small, moveable tactile displays such as those that resemble computer mice, word labels can be as important as the diagram itself. In addition, the ability to present Braille with these displays offers an alternative for accessing full pages of Braille with a cost effective system. In this work, we consider the inherent difficulties arising from presenting Braille on these displays and propose algorithms to circumvent these problems. Lastly, we present preliminary results from individuals who are visually impaired that suggests the promise of this approach.

Figure/Ground Segmentation via a Haptic Glance: Attributing Initial Finger Contacts to Objects or Their Supporting Surfaces

The current study addresses the well-known “figure/ground” problem in human perception, a fundamental topic that has received surprisingly little attention from touch scientists to date. Our approach is grounded in, and directly guided by, current knowledge concerning the nature of haptic processing. Given inherent figure/ground ambiguity in natural scenes and limited sensory inputs from first contact (a “haptic glance”), we consider first whether people are even capable of differentiating figure from ground (Experiments 1 and 2). Participants were required to estimate the strength of their subjective impression that they were feeling an object (i.e., figure) as opposed to just the supporting structure (i.e., ground). Second, we propose a tripartite factor classification scheme to further assess the influence of kinetic, geometric (Experiments 1 and 2), and material (Experiment 2) factors on haptic figure/ground segmentation, complemented by more open-ended subjective responses obtained at the end of the experiment. Collectively, the results indicate that under certain conditions it is possible to segment figure from ground via a single haptic glance with a reasonable degree of certainty, and that all three factor classes influence the estimated likelihood that brief, spatially distributed fingertip contacts represent contact with an object and/or its background supporting structure.

A low-cost, variable-amplitude haptic distributed display for persons who are blind and visually impaired

Previously in our lab, we developed a low-cost mouse-like device that has high position accuracy, very good temporal and spatial collocation between kinesthetic and tactile information, a fairly large temporal bandwidth and a short time delay. However, it can still be limiting when generating texture-like patterns. We have therefore extended the function of the device to be able to vary the amplitude as well, while maintaining its low cost (under

A tactile-thermal display for haptic exploration of virtual paintings

500). Various virtual textures have been developed which can be used to create salient graphics that can be perceived through this device. Preliminary investigations suggest that having multiple amplitude levels increases the number of distinguishable textures as well as the amount of information that can be displayed.