Apple won a Smartglasses patent this week that relates to the use of Ultrasonic Transduces for Position Tracking
On Tuesday, the U.S. Patent and Trademark Office officially granted Apple a patent that relates to Ultrasonic Transducers that may be used to track the position of an object. For example, eyewear such as a pair of glasses or other head-mounted device may use ultrasonic transducers to track a user's eye position and gaze direction. To increase positioning accuracy over short-range distances, an array of ultrasonic transducers with different center frequencies may be formed on a common substrate.
In Apple's patent background they note that HMDs such as smartglasses may use gaze tracking circuitry to track a user's gaze. It can be challenging to design gaze tracking circuitry that performs satisfactorily. If care is not taken, the gaze tracking circuitry may produce inaccurate measurements or may exhibit other performance limitations such as excessive power consumption.
Ultrasonic Transducers for Position Tracking
Ultrasonic transducers may be used to track the position of one or more objects of interest. For example, eyewear such as a pair of glasses or other head-mounted device may use one or more ultrasonic transducers to track a user's eye position and gaze direction.
The ultrasonic transducers may include capacitive micromachined ultrasonic transducers, piezoelectric micromachined transducers, and/or other suitable ultrasonic transducers for emitting and/or detecting acoustic signals.
To increase positioning accuracy over short-range distances, multiple ultrasonic transducers with different center frequencies may be arranged in an array. An array of closely spaced ultrasonic transducers with relatively small individual bandwidths may be used to simulate a single transducer with a much larger bandwidth, without sacrificing performance.
When the transducers in the array are properly phased, the array may be able to generate an ultrasonic signal pulse with a much shorter pulse length than that which could be produced with a single transducer alone. Being able to generate short ultrasonic signal pulses may be especially beneficial for determining short-range distances and for resolving two objects that are closely spaced together. For example, a phased transducer array may be able to resolve objects that are as close as one wavelength apart or other suitable distance.
If desired, the ultrasonic transducers with different center frequencies may be operated independently of one another to independently measure signals at different frequencies. The independently measured signals can then be used to estimate time of flight and path length to the desired level of accuracy.
In arrangements where the ultrasonic transducers are used for gaze tracking in a pair of glasses or other eyewear, multiple arrays of ultrasonic transducers may be distributed at different locations around each of the user's eyes. Each array may include ultrasonic transducers with different center frequencies. One or more of the arrays may emit ultrasonic signals towards the user's eye. The ultrasonic signals may reflect off of the user's eye and may be detected by one or more of the other arrays. Control circuitry may gather data from the transducer arrays to determine the user's eye position and/or gaze direction (e.g., using time delay measurement techniques, phase delay measurement techniques, amplitude measurement techniques, and/or other suitable measurement techniques).
To review the full details of this invention, check out Apple's granted 1206716.