Extensive research has been done in haptic feedback for texture simulation in virtual reality (VR). However, it is challenging to modify the perceived tactile texture of existing physical objects which usually serve as anchors for virtual objects in mixed reality (MR). In this paper, we present ViboPneumo, a finger-worn haptic device that uses vibratory-pneumatic feedback to modulate (i.e., increase and decrease) the perceived roughness of the material surface contacted by the user's fingerpad while supporting the perceived sensation of other haptic properties (e.g., temperature or stickiness) in MR. Our device includes a silicone-based pneumatic actuator that can lift the user's fingerpad on the physical surface to reduce the contact area for roughness decreasing, and an on-finger vibrator for roughness increasing. Our user-perception experimental results showed that the participants could perceive changes in roughness, both increasing and decreasing, compared to the original material surface. We also observed the overlapping roughness ratings among certain haptic stimuli (i.e., vibrotactile and pneumatic) and the originally perceived roughness of some materials without any haptic feedback. This suggests the potential to alter the perceived texture of one type of material to another in terms of roughness (e.g., modifying the perceived texture of ceramics as glass). Lastly, a user study of MR experience showed that ViboPneumo could significantly improve the MR user experience, particularly for visual-haptic matching, compared to the condition of a bare finger. We also demonstrated a few application scenarios for ViboPneumo.

翻译：在虚拟现实（VR）中，针对纹理模拟的触觉反馈已开展大量研究。然而，在混合现实（MR）中，如何改变通常作为虚拟物体锚点的现有物理物体的感知触觉纹理仍具挑战性。本文提出ViboPneumo——一种指戴式触觉设备，通过振动-气动反馈调节（即增强和减弱）用户指垫接触材料表面的感知粗糙度，同时保留MR中其他触觉属性（如温度或粘滞感）的感知。该设备包含一个硅胶气动执行器，可抬起用户指垫以减小物理表面接触面积从而降低粗糙度，以及一个指部振动器用于增强粗糙度。用户感知实验结果表明，参与者能够感知到相较原始材料表面粗糙度的增强与减弱。我们还观察到，某些触觉刺激（如振动触觉和气动刺激）的粗糙度评分与无触觉反馈时某些材料的原始感知粗糙度存在重叠。这表明在粗糙度维度上，存在将一种材料的感知纹理改变为另一种材料的可能性（例如将陶瓷的感知纹理修改为玻璃）。最后，MR体验用户研究表明，ViboPneumo能显著提升MR用户体验，尤其在视觉-触觉匹配方面，显著优于裸指条件。我们还展示了ViboPneumo的若干应用场景。