Lateral Modulation of Midair Ultrasound Focus for Intensified Vibrotactile Stimuli

Investigating the Recognition of Local Shapes Using Mid-air Ultrasound Haptics

“…Both detection and identification thresholds for line patterns generated through STM were found to be lower than detection thresholds for a single point generated through AM (which is consistent with prior results from Takahashi et al [18]). This result can be attributed to a number of factors, such as the change in modulation and possible constructive interference between successive focal points in STM, the stimulation of a larger surface area (which is consistent with previous findings on contact vibrotactile displays [19]), and even the fact that lines aligned with the y-axis allowed subjects to feel out the pattern with more sensitive parts of the hand than the palm (e.g., the fingertips).…”

Direct Finger Manipulation of 3D Object Image with Ultrasound Haptic Feedback

“…In previous systems [22] [25] [21], a perceptible vibrotactile sensation was generated by applying an amplitude modulation of about 100-250 Hz because this method has a low acoustic power efficiency. Recently, it has been reported that a stronger stimulation is perceived by vibrating the focus position along the skin while keeping the acoustic power constant [27]. By moving the focal points around the contact surfaces of the finger and the object, our system efficiently generates a perceptible vibrotactile sensation and pressure pattern on the finger surface according to the shape of the contact surface.…”

HaptiGlow: Helping Users Position their Hands for Better Mid-Air Gestures and Ultrasound Haptic Feedback

“…250 Hz). Alternative methods include moving the point continuously, instead [14], [15]. Many focal points can be perceived simultaneously [2], but a single point can be used to create feelings of movement or shapes [16].…”

“…For example, if the hand is 60 mm from sweet spot (p = 0.6), the circle diameter would be 16 mm. The haptic circle was rendered using lateral modulation [14], [15]: one ultrasound haptic focal point traversed the circumference of the circle at 75 Hz. We found that 75 Hz offered the strongest sensation for this shape and size range.…”