With Apple's device, signals from fingertip nodes can be wirelessly transmitted to host controllers. (Pixabay)

Apple has filed a patent application for a magnetic sensor-based proximity sensing system that can measure the movement of individual finger and thumb bones. The company has filed patents for similar research related to possible future virtual reality gloves for gamers and military training, and finger devices for a mixed-reality headset that could replace sensor gloves.

The proximity sensing architecture enables precise positioning of electronic devices in proximity to a modulated magnetic source. Multiple magnetic sensors aligned to detect magnetic field changes in different field directions axes can also be used to determine the 3D position of the magnetic field and can provide more information in locating the fingers and the hands.

Apple has filed a patent application for a magnetic sensor-based proximity sensing
system that can measure the movement of individual finger and thumb bones. (Apple)

One potential application is a device with fingertip nodes that can include multiple magnetic sensors to track the movement of one or more finger and/or hand sections. By placing a magnetic sensor on each fingertip, for example, inverse kinematics can be applied to compute the orientation, position, and angle of objects, using proximity signals detected by the magnetic sensors.

What is a proximity sensor?

An essential sensing function is the ability to detect the presence or proximity of an object. (Getty Images)

A proximity sensor is a non-contact sensor that detects the presence of an object (often referred to as the ¡°target¡±) when the target enters the sensor¡¯s field. Depending on the type of proximity sensor, sound, light, infrared radiation (IR), or electromagnetic fields may be utilized by the sensor to detect a target. Proximity sensors are used in phones, recycling plants, self-driving cars, anti-aircraft systems, and assembly lines. There are many types of proximity sensors, and they each sense targets in distinct ways. The two most commonly used proximity sensors are the inductive proximity sensor and the capacitive proximity sensor.  

An inductive proximity sensor can only detect metal targets. This is because the sensor utilizes an electromagnetic field. When a metal target enters the electromagnetic field, the inductive characteristics of the metal change the field¡¯s properties, thereby alerting the proximity sensor of the presence of a metallic target. Depending on how inductive the metal is, the target can be detected at either a greater or shorter distance.

Capacitive proximity sensors, on the other hand, are not limited to metallic targets. These proximity sensors are capable of detecting anything that can carry an electrical charge. Capacitive sensors are commonly used in liquid-level detection. Possible targets for capacitive sensors include but are but not limited to: glass, plastic, water, wood, metals, and a myriad of targets of other materials.

Diagram of Reflective Photoelectric Sensor.  Source: Omron

Another type of proximity sensor is called a photoelectric proximity sensor. There are two main types of photoelectric proximity sensors: reflective and through-beam. Reflective proximity sensors detect objects when the light emitted from the sensor is reflected back at the photoelectric receiver. Through-beam sensors detect targets when the target breaks the beam of light between the sensor¡¯s emitter and receiver. 

Two other commonly used proximity sensors are the magnetic proximity sensors and ultrasonic proximity sensors. Magnetic proximity sensors are only used to detect permanent magnets. Ultrasonic proximity sensors emit a high pitch sound. The distance between the sensor and the target is determined by how long the sound takes to reflect back to the sensor.

The control device with fingertip nodes can also include one or more other electronic components, such as electrodes for enabling capacitive touch, and/or contact sensing between finger tips. It can also include force sensors, actuators for haptic feedback, temperature sensors and heaters.

Apple also says the control device with fingertip nodes can incorporate logic such as an on-board controller, a connector, a transceiver, a battery, and the like. It can also include a host controller that renders the profile of the hand on the screen. Signals from the fingertip nodes can be wirelessly transmitted to the host controllers.