Varifocal head-mounted display including modular air spaced optical assembly

• US 10,416,766 B1
• Filed: 04/19/2019
• Issued: 09/17/2019
• Est. Priority Date: 01/17/2017
• Status: Active Grant

• Current Assignee: META Platforms Technologies LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Original Assignee: Facebook Technologies, LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Inventors: Trail, Nicholas Daniel, Lanman, Douglas Robert
• Primary Examiner(s): Sherman, Stephen G
• Assistant Examiner(s): Midkiff, Aaron
• Application Number:
  US16/389,685
• Time in Patent Office: 151 Days
• Field of Search: 345 8, 345156, 382103, 359630
• CPC Class Codes: G02B 2027/0138 comprising image capture systems, e.g. camera
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 2027/0185 Displaying image at variable distance
• CPC Class Codes: G02B 27/0093 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02C 7/081 Ophthalmic lenses with variable focal length
• CPC Class Codes: G06F 1/163 Wearable computers, e.g. on a belt
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/013 Eye tracking input arrangements G06F3/015 takes precedence

Abstract

A head-mounted display (HMD) includes an electronic display configured to emit image light, an optical assembly that provides optical correction to the image light, an eye tracking system, and a varifocal module. The optical assembly includes a back optical element configured to receive the image light from the electronic display, and a coupling assembly configured to couple a front optical element to a location within the optical assembly such that the front optical element receives light transmitted by the back optical element. The optical correction is determined in part by an optical characteristic of the front optical element that is replaceable. The eye tracking system determines eye tracking information for a first eye of a user of the HMD. A varifocal module adjusts focus of images displayed on the electronic display, based on the eye tracking information and the optical correction.

Claims

1. An eye tracker comprising:

an illumination source located between a first optical element and a second optical element which share an optical axis, the eye tracker configured to;

output light generated by the illumination source, and

determine a gaze direction for an eye relative to the optical axis based at least in part on a modified version of the output light,

the output light being modified by an optical power of the first optical element prior to reflection from the eye.

2. The eye tracker of claim 1, wherein the first optical element is replaceable and selected from a set of optical elements, each optical element from the set having a unique optical power.

3. The eye tracker of claim 2, wherein the set of optical elements comprises spherical lenses with spherical optical powers of −

6, −

3, 0, and 3 diopters, and other lenses with the same spherical optical powers having additional diopters for astigmatism.

4. The eye tracker of claim 1, wherein the first optical element is rotatable to compensate for astigmatism.

5. The eye tracker of claim 1, wherein the eye tracker is positioned optically after reflection from the second optical element.

6. The eye tracker of claim 1, wherein the eye tracker is positioned optically folded between the first optical element and the second optical element.

7. The eye tracker of claim 1, wherein a surface of the second optical element is configured to reflect light of a defined range of wavelengths, and the eye tracker comprises:

the illumination source positioned optically between the first optical element and the second optical element, the illumination source configured to illuminate the surface of the back optical element with the output light having one or more wavelengths within the defined range of wavelengths;

an imaging device positioned optically between the first optical element and the second optical element, the imaging device configured to capture an image of the eye illuminated with the modified version of the output light having the one or more wavelengths and reflected from the surface of the back optical element; and

a controller coupled to the imaging device and the illumination source, the controller configured to determine the gaze direction for the eye based on the captured image.

8. The eye tracker of claim 7, wherein the surface of the second optical element is coated to reflect light of the defined range of wavelengths and transmit visible light.

9. The eye tracker of claim 7, wherein the surface of the second optical element is spherical, aspherical, consisting of a polynominal basis, or of a free-form.

10. The eye tracker of claim 7, wherein the imaging device is oriented to capture the image of the eye illuminated with the modified version of the output light reflected from the eye and then from the surface of the second optical element.

11. The eye tracker of claim 7, wherein:

the modified version of the output light having the one or more wavelengths reflected from the surface of the second optical element comprises infra-red (IR) light; and

the imaging device comprises a camera configured to capture images in the IR.

12. The eye tracker of claim 1, wherein the illumination source and an imaging device of the eye tracker are positioned outside of an optical path to the eye and at opposite sides of an optical axis.

13. The eye tracker of claim 1, wherein the first optical element shares an optical axis with the second optical element.

14. The eye tracker of claim 1, wherein the eye tracker, the first optical element and the second optical element are part of a head-mounted display (HMD).

15. The eye tracker of claim 14, wherein the HMD comprises:

a display sharing an optical axis with the first optical element and the second optical element, the display being adjacent to the second optical element; and

a varifocal module configured to adjust focus of one or more images displayed on the display, based on the determined gaze direction and the optical power.

16. The eye tracker of claim 15, wherein the varifocal module is configured to compensate for a difference between a prescription of a user of the HMD and the optical power to provide optical correction to image light emitted from the display.

17. The eye tracker of claim 15, wherein the varifocal module is configured to adjust focus of the one or more images displayed on the display by adjusting position of at least one of the display, the first optical element and the second optical element based on the determined gaze direction and the optical power.

18. The eye tracker of claim 14, wherein the HMD comprises:

a coupling assembly configured to couple the first optical element to a location within the HMD such that the first optical element receives light transmitted by the second optical element, and that there is an air gap between the location and the second optical element.

19. A method comprising:

instructing an illumination source located between a first optical element and a second optical element which share an optical axis to emit light, and

determining a gaze direction for an eye relative to the optical axis based at least in part on a modified version of the emitted light,

the emitted light being modified by an optical power of the first optical element prior to reflection from the eye.

20. The method of claim 19, wherein a surface of the second optical element is configured to reflect light of a defined range of wavelengths, the method further comprising:

instructing the illumination source to illuminate the surface of the second optical element with the emitted light having one or more wavelengths within the defined range of wavelengths;

capturing an image of the eye illuminated with the modified version of the emitted light having the one or more wavelengths and reflected from the surface of the second optical element; and

determining the gaze direction for the eye based on the captured image.