Perception Of Surface Texture Research Articles

Monolithic integrated optoelectronic chip for vector force detection

Sensors with a small footprint and real-time detection capabilities are crucial in robotic surgery and smart wearable equipment. Reducing device footprint while maintaining its high performance is a major challenge and a significant limitation to their development. Here, we proposed a monolithic integrated micro-scale sensor, which can be used for vector force detection. This sensor combines an optical source, four photodetectors, and a hemispherical silicone elastomer component on the same sapphire-based AlGaInP wafer. The chip-scale optical coupling is achieved by employing the laser lift-off techniques and the flip-chip bonding to a processed sapphire substrate. This hemispherical structure device can detect normal and shear forces as low as 1 mN within a measurement range of 0–220 mN for normal force and 0–15 mN for shear force. After packaging, the sensor is capable of detecting forces over a broader range, with measurement capabilities extending up to 10 N for normal forces and 0.2 N for shear forces. It has an accuracy of detecting a minimum normal force of 25 mN and a minimum shear force of 20 mN. Furthermore, this sensor has been validated to have a compact footprint of approximately 1.5 mm2, while maintaining high real-time response. We also demonstrate its promising potential by combining this sensor with fine surface texture perception in the fields of compact medical robot interaction and wearable devices.

Tactile discrimination of real and simulated isotropic textures by Friction-Induced Vibrations

Friction-induced vibrations are one of the main mechanical signals that, stimulating the mechanoreceptors, mediate the fine surface texture perception. In this work, isotropic textures are simulated by means of a tactile device reproducing the friction-induced vibrations previously measured during the exploration of real textures. Texture discrimination campaigns have been carried out, showing excellent results in discriminating both the real textures and the ones simulated by the device. Discrimination errors and correct associations of real and simulated samples have been explained through the spectra of the friction-induced vibrations, highlighting that the overall amplitude of the induced vibrations and their spectra play a fundamental role in the discrimination of isotropic textures.

Greenery as an Element of Imageability in Window Views

A window view affects a person’s well-being and comfort. The effect of visual contact with nature on people depends on the quality of the outside scenery, which in turn depends on parameters such as the number of visible layers, the distance to visual elements and environmental information (content) in the window view. Many studies have concluded that views of nature are preferable, while in urban environments a high-quality window view should include greenery. In our study, a survey was conducted among two groups of students at the Faculty of Architecture, University of Ljubljana, to find out how the respondents perceived urban imageability in a window view. Using the example of five neighborhoods in Ljubljana (Slovenia), which have different urban planning and design concepts and greeneries, we investigated whether respondents perceived the presence of greenery as an important element of visual comfort. They ranked the quality of window views using eight indicators. The analysis of the ranking of the answers showed that the responses were similar for the two survey approaches (with single-selection and with multiple-selection techniques), except for the perception of surface texture. This indicates a common understanding of the role of greenery and an ambiguity in the perception of what is meant by the term ‘texture’.

Cortical Representation of Tactile Stickiness Evoked by Skin Contact and Glove Contact.

Even when we are wearing gloves, we can easily detect whether a surface that we are touching is sticky or not. However, we know little about the similarities between brain activations elicited by this glove contact and by direct contact with our bare skin. In this functional magnetic resonance imaging (fMRI) study, we investigated which brain regions represent stickiness intensity information obtained in both touch conditions, i.e., skin contact and glove contact. First, we searched for neural representations mediating stickiness for each touch condition separately and found regions responding to both mainly in the supramarginal gyrus and the secondary somatosensory cortex. Second, we explored whether surface stickiness is encoded in common neural patterns irrespective of how participants touched the sticky stimuli. Using a cross-condition decoding method, we tested whether the stickiness intensities could be decoded from fMRI signals evoked by skin contact using a classifier trained on the responses elicited by glove contact, and vice versa. Our results found shared neural encoding patterns in the bilateral angular gyri and the inferior frontal gyrus (IFG) and suggest that these areas represent stickiness intensity information regardless of how participants touched the sticky stimuli. Interestingly, we observed that neural encoding patterns of these areas were reflected in participants’ intensity ratings. This study revealed common and distinct brain activation patterns of tactile stickiness using two different touch conditions, which may broaden the understanding of neural mechanisms related to surface texture perception.

Complexity, rate, and scale in sliding friction dynamics between a finger and textured surface

Sliding friction between the skin and a touched surface is highly complex, but lies at the heart of our ability to discriminate surface texture through touch. Prior research has elucidated neural mechanisms of tactile texture perception, but our understanding of the nonlinear dynamics of frictional sliding between the finger and textured surfaces, with which the neural signals that encode texture originate, is incomplete. To address this, we compared measurements from human fingertips sliding against textured counter surfaces with predictions of numerical simulations of a model finger that resembled a real finger, with similar geometry, tissue heterogeneity, hyperelasticity, and interfacial adhesion. Modeled and measured forces exhibited similar complex, nonlinear sliding friction dynamics, force fluctuations, and prominent regularities related to the surface geometry. We comparatively analysed measured and simulated forces patterns in matched conditions using linear and nonlinear methods, including recurrence analysis. The model had greatest predictive power for faster sliding and for surface textures with length scales greater than about one millimeter. This could be attributed to the the tendency of sliding at slower speeds, or on finer surfaces, to complexly engage fine features of skin or surface, such as fingerprints or surface asperities. The results elucidate the dynamical forces felt during tactile exploration and highlight the challenges involved in the biological perception of surface texture via touch.

Holistic Processing Affects Surface Texture Perception: Approach from Japanese Sound Symbolic Words

The human visual system is able to perceive not only the macrostructure (form and shape) of a surface, but also its microstructure (texture). Some evidence suggests that microstructural characteristics are processed independently of macrostructural features. However, the human visual system can interpret a variety of information about the physical world, enabling the recognition and semantic categorization of complex visual scenes at a glance. This remarkable perceptual ability relies heavily on holistic processing, which is achieved by estimating the global statistical summary of an image. On the other hand, texture is an important source of information for distinguishing between artificial and naturally occurring surfaces in images. In addition, it is reported that Japanese sound symbolic words are useful to express fine differences in texture and synesthetic characteristics. However, there is no evidence comparing the characteristics of surface texture perception between whole- and part-based images using sound symbolic words. The objective of the present study was to examine whether sound symbolic words for describing the surface texture perception differs between whole-based images related to the holistic processing and part-based images. In Experiment 1, we examined the effect of wholebased images in surface texture perception using sound symbolic words. In Experiment 2, we examined the effect of part-based images in surface texture perception using sound symbolic words. The results revealed that the sensory and symbolic descriptors differed in texture perceptions between whole-based and part-based image processing. These findings suggest that sound symbolic words can describe differences in surface texture between whole-based and part-based images at a fine resolution.

Effect of color, gloss, and surface texture perception on scratch and mar visibility in polymers

Abstract Scratch and mar can critically impact the aesthetics of polymeric surfaces. Their quantification poses considerable challenges, especially for subtle mar damages. Here, we report a new standardized approach that utilizes a modified ASTM/ISO scratch test standard and a psychophysical tool to quantify scratch and mar visibility. The new methodology was then used to study the influence of color, gloss, and texture perception on scratch and mar visibility resistance. These factors have limited influence on scratch visibility onset. However, faint mar damage is more sensitive to surface perceptual properties. It has been found that overall visibility throughout the entire damage path is a better indicator for ranking mar damage. Results show that contrast slope variation parameter can consistently quantify mar visibility and simulate human perception. Green, glossy, and smooth surfaces tend to have less mar visibility resistance. The effect of a fatty amide slip agent was also investigated. These modifiers improved both scratch and mar visibility resistance. This unique approach paves the way for a straightforward universal standard that can be utilized to reliably quantify scratch and mar visibility in polymers, thereby opening up a new avenue for the design of polymeric materials with better scratch and mar visibility resistance.

Are visual texture-selective areas recruited during haptic texture discrimination?

Shape and surface texture provide salient cues to object identity, both when objects are explored using vision and via touch (haptics). In vision, shape information is processed within the lateral occipital complex (LOC), while surface texture is selectively processed in medial ventro-temporal cortex, in the collateral sulcus (CoS) and parahippocampul gyrus (pHG). Accumulating evidence indicates that the LOC, despite its location within the ventral visual system, is also consistently recruited during haptic shape processing. Here we used fMRI to examine whether ventral ‘visual’ texture-selective areas are similarly recruited when observers discriminate surface texture via touch. We used a blocked design in which participants attended to, and made same/different judgments about, sequential pairs of 3-dimensional plastic objects. During each block, the stimuli varied either in their shape (but not surface texture), or their surface texture (but not shape). In half of the scans, participants explored the stimuli using vision alone, and in the remaining scans the stimuli were explored via touch alone. In vision, the strongest fMRI responses to surface texture (versus shape) perception were observed within medial ventral temporal cortex – a result consistent with recent fMRI findings in vision. When stimuli were explored via touch, however, the strongest fMRI responses to surface texture (versus shape) perception were observed dorsally, within the parietal operculum (in the vicinity of secondary somatosensory cortex) and inferior frontal cortex. Importantly, however, we also observed significant texture-selective fMRI responses in medial ventral temporal cortex within areas analogous to those recruited during visual texture discrimination. Our imaging data demonstrate for the first time that ventro-medial temporal areas known to process visual textures are also recruited during the perception of surface texture via touch. Meeting abstract presented at VSS 2013

Crossmodal interactions of haptic and visual texture information in early sensory cortex

Both visual and haptic information add to the perception of surface texture. While prior studies have reported crossmodal interactions of both sensory modalities at the behavioral level, neuroimaging studies primarily investigated texture perception in separate visual and haptic paradigms. These experimental designs, however, only allowed to identify overlap in both sensory processing streams but no interaction of visual and haptic texture processing. By varying texture characteristics in a bimodal task, the current study investigated how these crossmodal interactions are reflected at the cortical level. We used fMRI to compare cortical activation in response to matching versus non-matching visual-haptic texture information. We expected that passive simultaneous presentation of matching visual-haptic input would be sufficient to induce BOLD responses graded with varying texture characteristics. Since no cognitive evaluation of the stimuli was required, we expected to find changes primarily at a rather early processing stage. Our results confirmed our assumptions by showing crossmodal interactions of visual-haptic texture information in early somatosensory and visual cortex. However, the nature of the crossmodal effects was slightly different in both sensory cortices. In early visual cortex, matching visual-haptic information increased the average activation level and induced parametric BOLD signal variations with varying texture characteristics. In early somatosensory cortex only the latter was true. These results challenge the notion that visual and haptic texture information is processed independently and indicate a crossmodal interaction of sensory information already at an early cortical processing stage.

Infant Perception of Surface Texture and Relative Height as Distance Information: A Preferential-Reaching Study.

Two preferential-reaching experiments explored 5- and 7-month-olds' sensitivity to pictorial depth cues. In the first experiment, infants viewed a display in which texture gradients, linear perspective of the surface contours, and relative height in the visual field provided information that two objects were at different distances. Five- and 7-month-old infants reached preferentially for the apparently nearer object under monocular but not binocular viewing conditions, indicating that infants in both age groups respond to pictorial depth cues. In the second experiment, texture gradients and linear perspective of the surface contours were eliminated from the experimental display, making relative height the sole pictorial depth cue. Seven-month-olds again reached more often for the apparently nearer object under monocular, but not binocular viewing conditions. By contrast, the 5-month-olds' reaching behavior did not differ between viewing conditions. These results indicate that 7-month-olds respond to the depth cue of relative height but provide no evidence of responsiveness to relative height in 5-month-olds. Both age groups responded more consistently to pictorial depth in Experiment 1 than in Experiment 2.

Perceptual dimensions of tactile surface texture: a multidimensional scaling analysis.

The purpose of this study was to examine the subjective dimensionality of tactile surface texture perception. Seventeen tactile stimuli, such as wood, sandpaper, and velvet, were moved across the index finger of the subject, who sorted them into categories on the basis of perceived similarity. Multidimensional scaling (MDS) techniques were then used to position the stimuli in a perceptual space on the basis of combined data of 20 subjects. A three-dimensional space was judged to give a satisfactory representation of the data. Subjects' ratings of each stimulus on five scales representing putative dimensions of perceived surface texture were then fitted by regression analysis into the MDS space. Roughness-smoothness and hardness-softness were found to be robust and orthogonal dimensions; the third dimension did not correspond closely with any of the rating scales used, but post hoc inspection of the data suggested that it may reflect the compressional elasticity ("springiness") of the surface.

The visual perception of surface texture in photographs.

A theoretical and empirical investigation was undertaken to investigate the role of surface texture in ecological optics. Forty-nine subjects each viewed a set of 30 professionally produced photographs of rectangular samples of surface textures. The photographs included common textures such as sand, fur, rock, and so forth. These photographs were flat and, therefore, these static surfaces provide only a fraction of the information afforded by normal textures. Subjects answered questions about the identity, physical properties, and viewing conditions of each texture. Correct identifications were made in about two-thirds of the cases. When no identification, or an incorrect one, was given, subjects were still able to identify physical state (solid, liquid, gas), planarity (planar, rough), and pigmentation (homogeneous, uneven) at a better than chance level, though hardness could not be accurately assessed. Diffuseness versus directionality of incident light could be distinguished, though mistakes were more frequent on this discrimination. The direction of incident light, in cases where it was sharply defined, could be determined accurately for only a few cases of rough textures; in some others, light was reported as incident from either the correct side or its 180° opposite — a “polarization effect”. Most subjects correctly detected the orientation of textures photographed in the frontal plane, but only a few textures' slants were accurately perceived. The results are interpreted in terms of properties of substances as specified by invariants of the optic way.

Texture perception: studies of intersensory organization using a discrepancy paradigm, and visual versus tactual psychophysics.

Three experiments were performed involving the perception of surface texture. Experiment 1 indicated that when vision and touch are presented with discrepant information concerning texture, the two senses appear to weight the information about equally. Moreover, Experiment 2 showed that using touch, vision, or touch and vision, subjects performed a texture identification task with comparable matching accuracy and precision. Experiment 3 demonstrated that using the same three modes, subjects performed a magnitude estimation task similarly, in terms of magnitude estimates of roughness, the rates of growth of perceived roughness, and response precision. The comparability of the two senses in texture-related tasks may underlie the relatively equal compromise between discrepant sources of texture information demonstrated in Experiment (modality superiority interpretation). Such a compromise is somewhat different from that commonly reported in the sensory conflict literature. The relative weighting of multiple sources of sensory information about surface texture was also considered in terms of a directed-attention interpretation of intersensory organization.

Auditory Texture Perception

A set of three studies was designed to investigate the role of touch-produced sounds in the perception of surface texture. Subjects were capable of judging roughness on the basis of sounds alone. Auditory judgments were similar, but not identical to corresponding haptic touch judgments. When both sources of information were available, subjects tended to use the tactile cues. The nature of the auditory stimulus for roughness is considered.