Finexus

Abstract

With the resurgence of head-mounted displays for virtual reality, users need new input devices that can accurately track their hands and fingers in motion. We introduce Finexus, a multipoint tracking system using magnetic field sensing. By instrumenting the fingertips with electromagnets, the system can track fine fingertip movements in real time using only four magnetic sensors. To keep the system robust to noise, we operate each electromagnet at a different frequency and leverage bandpass filters to distinguish signals attributed to individual sensing points. We develop a novel algorithm to efficiently calculate the 3D positions of multiple electromagnets from corresponding field strengths. In our evaluation, we report an average accuracy of 1.33 mm, as compared to results from an optical tracker. Our real-time implementation shows Finexus is applicable to a wide variety of human input tasks, such as writing in the air.

High Precision Electromagnetic Momentum Positioning with Current Loop

“…[7], can be simplified if the observations are made in the region very close to the small loop, i.e., kr << 1. Thus, (1) where, I 0 denotes the current amplitude, a is the radius of the small loop, k is the wave-number and r denotes the distance to the center of the small loop, j = . The notation H and E with angle subscripts represent the components of magnetic and electric field strengths.…”

“…The SNR of the magnetic sensor in 3-axis directions are denoted as , and . In typical personal wearable devices, such as data gloves, the relative distance between the transmitter and receiver is p y p x ---- usually within 0.4 m, i.e., the small loops can be put on the fingertips, and the receiver unit can be installed on the back of the hand or on the forearm [1]. Therefore, under this circumstance, the positioning accuracy of millimeter is required within the range of 0.4 m. For our devices, according to the experimental data, the SNR can exceed 15 dB at the distance of 0.4 m from the source.…”

“…Over the past few years, Virtual Reality (VR), Augmented Reality (AR) and other personal wearable devices have become popular [1]. Wearing head-mounted displays for VR, users need new input devices that can accurately track their hands and fingers in motion.…”

“…Magnetic Field Positioning (MFP), which is proposed by Raab et al, is one typical approach for continuous, accurate, and occlusion-free finger tracking [2]. Polhemus is one of the earliest systems utilizing MFP sensing, and can track objects with six degrees of freedom [1]. Some commercial products, such as Razer Hydra, use similar MFP approaches in combination with Inertial Measurement Units (IMUs) to enable game-controllerbased tracking [3].…”

Nail tip sensor: Toward reliable daylong monitoring of heart rate

“…As sensor devices attached to fingernails, force sensors , touchpads , hand and finger motion sensors , visual displays , tactile displays , and small photoplethysmographic (PPG) recording circuits are reported. Katsuyuki et al .…”