# US 11,892,649 B2 · Passive world-referenced eye tracking for smartglasses

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- Number: US 11,892,649 B2
- Document ID: US11892649B2
- Status: Granted
- Kind: B2
- Application number: 18/297,372
- Filed: 2023-04-07
- Published: 2023-10-12
- Granted: 2024-02-06
- Earliest claimed: 2022-04-07
- Assignees: Google Inc.
- Applicants: Google LLC
- Inventors: Daniel Adema; Timothy Paul Bodiya
- Web page: https://patentgrep.com/patent/US11892649B2

## CPC

- G02B 27/0179: {Display position adjusting means not related to the information to be displayed}
- G02B 6/0055: {Reflecting element, sheet or layer}
- G02B 6/0056: {for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements}
- G02B 27/0172: {characterised by optical features}
- G06F 3/013: {Eye tracking input arrangements (G06F3/015 takes precedence)}
- G09G 3/002: {to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT}
- G02B 2027/0178: {Eyeglass type (eyeglass details G02C)}
- G02B 2027/0187: {slaved to motion of at least a part of the body of the user, e.g. head, eye}
- G09G 2354/00: Aspects of interface with display user
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

Improved systems ensuring an accuracy of eye gaze measurements in an augmented reality head-mounted wearable device include a radiation direction rerouter (e.g., a partial retroreflector) configured to adjust an angle of incidence of the radiation in the waveguide at a first surface of a waveguide to produce radiation directed at an adjusted angle of incidence at an outcoupler such that the output direction is essentially parallel to the gaze angle of the user's eye. For example, a partial retroreflector may be disposed on a surface of the waveguide opposite the outcoupler provides an additional reflection so that the gaze angle of the user's eye is matched to an angle of an image of the eye pupil onto a world-facing radiation detector (e.g., a camera).

## Claims

### Claim 1

A head-mounted wearable device, including:
a frame worn by a user, including:
a world-facing radiation detector;
a gaze-tracking device configured to produce gaze-tracking radiation for measuring a gaze angle of a user's eye, the gaze-tracking radiation being reflected from the user's eye;
a waveguide including:
an incoupler configured to couple the gaze-tracking radiation into the waveguide to produce radiation in the waveguide; and
an outcoupler configured to couple the radiation in the waveguide out of the waveguide to produce outcoupled radiation, the outcoupled radiation being emitted from the outcoupler in an output direction toward the world-facing radiation detector; and
a radiation direction rerouter configured to adjust an angle of incidence of the radiation in the waveguide at a first surface of the waveguide to produce radiation directed at an adjusted angle of incidence at the outcoupler such that the output direction is essentially parallel to the gaze angle of the user's eye.

### Claim 2 (depends on 1)

The head-mounted wearable device as in claim 1, wherein the outcoupler is located on a second surface of the waveguide, the second surface being opposite the first surface.

### Claim 3 (depends on 2)

The head-mounted wearable device as in claim 2, wherein the radiation direction rerouter includes a partial retroreflector mirror.

### Claim 4 (depends on 2)

The head-mounted wearable device as in claim 2, wherein the radiation direction rerouter includes a polarizer configured to change a polarization of the radiation in the waveguide.

### Claim 5 (depends on 1)

The head-mounted wearable device as in claim 1, further comprising:
a projection system configured to emit internally generated radiation, the projection system being aligned to an orientation of the world-facing radiation detector during an initial calibration operation that is performed prior to operation of the head-mounted wearable device.

### Claim 6 (depends on 1)

The head-mounted wearable device as in claim 1, wherein the gaze-tracking radiation has a wavelength in a spectral range that includes an infrared band.

### Claim 7 (depends on 1)

The head-mounted wearable device as in claim 1, wherein the gaze-tracking radiation is emitted according to a specified temporal schedule.

### Claim 8 (depends on 1)

The head-mounted wearable device as in claim 1, wherein the gaze-tracking radiation is emitted according to a specified spatial pattern.

### Claim 9 (depends on 1)

The head-mounted wearable device as in claim 1, wherein the gaze-tracking device is separate from the world-facing radiation detector.

### Claim 10

A method, comprising:
disposing, on a waveguide included in a frame of a head-mounted wearable device worn by a user, the frame also including a world-facing radiation detector and an gaze-tracking device configured to produce gaze-tracking radiation for measuring a gaze angle of a user's eye, the gaze-tracking radiation being reflected from the user's eye, an incoupler configured to couple the gaze-tracking radiation into the waveguide to produce radiation in the waveguide;
disposing, on the waveguide, an outcoupler configured to couple the radiation in the waveguide out of the waveguide to produce outcoupled radiation, the outcoupled radiation being emitted from the outcoupler in an output direction toward the world-facing radiation detector; and
disposing, in the frame, a radiation direction rerouter configured to adjust an angle of incidence of the radiation in the waveguide at a first surface of the waveguide to produce radiation directed at an adjusted angle of incidence at the outcoupler such that the output direction is essentially parallel to the gaze angle of the user's eye.

### Claim 11 (depends on 10)

The method as in claim 10, wherein the outcoupler is located on a second surface of the waveguide, the second surface being opposite the first surface.

### Claim 12 (depends on 11)

The method as in claim 11, wherein the radiation direction rerouter includes a partial retroreflector mirror.

### Claim 13 (depends on 11)

The method as in claim 11, wherein the radiation direction rerouter includes a polarizer configured to change a polarization of the radiation in the waveguide.

### Claim 14 (depends on 10)

The method as in claim 10, wherein the head-mounted wearable device further includes a projection system configured to emit internally generated radiation, the projection system being aligned to an orientation of the world-facing radiation detector during an initial calibration operation that is performed prior to operation of the head-mounted wearable device.

### Claim 15 (depends on 10)

The method as in claim 10, wherein the gaze-tracking radiation has a wavelength in a spectral range that includes an infrared band.

### Claim 16 (depends on 10)

The method as in claim 10, wherein the gaze-tracking radiation is emitted according to a specified temporal schedule.

### Claim 17 (depends on 10)

The method as in claim 10, wherein the gaze-tracking radiation is emitted according to a specified spatial pattern.

### Claim 18 (depends on 10)

The method as in claim 10, wherein the gaze-tracking device is separate from the world-facing radiation detector.