Haptic Edge Sharpness Perception with a Contact Location Display

The effect of contact location information on virtual edge perception was investigated in two experiments. In Experiment 1, participants discriminated edge sharpness under force-alone and force-plus-contact-location conditions using a 4.8 mm radius contact roller. Virtual objects were 2D profiles of edges with two adjoining surfaces. For both conditions, the Just Noticeable Difference (JND) in change of edge radius increased from 2.3 to 7.4 mm as edge radii increased from 2.5 to 20.0 mm; there was no significant difference between the two conditions. A follow-up experiment with contact location alone resulted in higher edge sharpness JNDs. In Experiment 2, the same edge sharpness discrimination task was performed using a smaller contact roller (R = 1.5 mm) to investigate the effect of roller size. The JNDs for the smaller roller were not statistically significant from those of the larger roller. Our results suggest that 1) contact location cues alone are capable of conveying edge sharpness information, but that force cues are dominant when both types of cues are available; and 2) the radius of the contact roller does not significantly affect the user´s ability to discriminate edge sharpness, indicating that the participants could use the changes in contact location to judge curvature.