Phased array of ultrasound transducers for depth sensing
A depth sensing system is configured to track one or both eyes of a user. The depth sensing system includes a transducer chip comprising a phased array of ultrasound transducers that transmit a signal at an eye of the user and detect a reflected signal from the eye. A controller estimates an orientation of the eye based on the reflected signals received by the phased array. The depth sensing system may be part of a headset that includes a display element configured to display content to a user wearing the headset.
1. A headset comprising:
a frame;
a transducer chip coupled to the frame, the transducer chip comprising a plurality of ultrasound transducers in a phased array configured to transmit ultrasonic beams and receive reflected ultrasonic signals, each ultrasound transducer of the plurality of ultrasound transducers comprising a membrane and an anchor portion located at each corner of the membrane, a width of the anchor portion affecting acoustic properties of the ultrasonic beams; and
a controller configured to estimate an orientation of an eye of a user of the headset based on the reflected ultrasonic signals.
2. The headset of claim 1 , wherein the plurality of ultrasound transducers comprise a plurality of Piezoelectric Micromachined Ultrasonic Transducer (PMUT) transducers or a plurality of Capacitive Micromachined Ultrasonic Transducer (CMUT) transducers.
3. The headset of claim 1 , wherein the controller is further configured to steer the ultrasonic beams transmitted by the plurality of ultrasound transducers.
4. The headset of claim 1 , wherein the transducer chip is centered relative to a vertical axis or a horizontal axis of a display element of the headset.
5. The headset of claim 1 , wherein each of the plurality of ultrasound transducers comprises a cutout section on at least one side of the membrane.
6. The headset of claim 1 , wherein the controller is further configured to scan the eye of the user by calculating depth measurements to a plurality of locations of the eye.
7. The headset of claim 1 , wherein the controller is further configured to adjust a focus of the transmitted ultrasonic beams and steer the transmitted ultrasonic beams.
8. A transducer chip comprising:
a substrate; and
a phased array of ultrasound transducers positioned on the substrate, the phased array configured to:
steer ultrasonic beams to different locations of an eye, and
receive reflected ultrasound signals from the ultrasonic beams reflecting off the eye,
wherein each of the ultrasound transducers comprises:
a Piezoelectric Micromachined Ultrasonic Transducer (PMUT) transducer,
a membrane, and
an anchor portion located at each corner of the membrane, a width of the anchor portion affecting acoustic properties of the ultrasonic beams.
9. The transducer chip of claim 8 , wherein each of the ultrasound transducers is individually controllable.
10. The transducer chip of claim 8 , wherein a width of each of the ultrasound transducers is between 100-1000 microns.
11. The transducer chip of claim 8 , wherein the membrane comprises a cutout section on at least one side of the membrane, and the cutout section reduces a resonance frequency of the membrane.
12. The transducer chip of claim 11 , wherein a width of the cutout section is between 1-10 microns.
13. The transducer chip of claim 8 , wherein the ultrasound transducers are configured to emit ultrasonic waves at between 100-1000 kHz.
14. A method comprising:
transmitting, by a transducer chip comprising a plurality of ultrasound transducers, a plurality of ultrasonic beams toward an eye, each ultrasound transducer of the plurality of ultrasound transducers comprising a membrane and an anchor portion located at each corner of the membrane, a width of the anchor portion affecting acoustic properties of the plurality of ultrasonic beams;
receiving, by the transducer chip, reflected ultrasonic signals from the eye;
calculating, by a controller, a distance measurement based on the reflected ultrasonic signals;
generating, by the controller, a scan based on the calculated distance measurement; and
estimating, by the controller, a gaze direction of the eye based on the generated scan.
15. The method of claim 14 , further comprising:
steering a first ultrasonic beam of the plurality of ultrasonic beams to a first location on the eye; and
steering a second ultrasonic beam of the plurality of ultrasonic beams to a second location on the eye.
16. The method of claim 14 , further comprising converting, by the transducer chip, the reflected ultrasonic signals into an electronic signal which is measured by the controller.
17. The method of claim 14 , wherein the scan comprises a training scan comprising distance measurements at a first number of locations on the eye, and further comprising generating a tracking scan, the tracking scan comprises distance measurements at a second number of locations on the eye, and the second number is less than the first number.
18. The method of claim 14 , wherein estimating the gaze direction comprises:
estimating a direction of a pupillary axis of the eye; and
estimating a direction of a foveal axis of the eye based on the estimated direction of the pupillary axis and an offset between the pupillary axis and the foveal axis.
19. The method of claim 14 , wherein each of the plurality of ultrasound transducers comprises a Piezoelectric Micromachined Ultrasonic Transducer (PMUT) transducer.