Beamsplitter assembly for eye tracking in head-mounted displays

A head-mounted display (HMD) comprising:

• an electronic display configured to output image light;
• a pancake lens configured to direct image light in a first band from the electronic display to an eye box, the pancake lens including a front optical element and a back optical element that are positioned along an optical axis, and the eye box is a region in space occupied by an eye of a user of the HMD;
• a compound curved beamsplitter including a first region with a first curvature, a second region with a second curvature, a first portion with a distinct third curvature joining the first region and the second region curved such that an angle between the first region and the optical axis is larger than an angle between second region and the optical axis, a third region, and a second portion joining the second region and the third region curved such that an angle between the third region and the optical axis is larger than the angle between the second region and the optical axis, the beamsplitter positioned along the optical axis between the back optical element and the electronic display and configured to redirect light in a second band passing through the pancake lens toward a first position and transmit the image light in the first band;
• and
• an eye tracking unit configured to generate eye tracking information, the eye tracking unit comprising:
• an illuminator configured to illuminate portions of the eye of the user of the HMD with light in the second band,
• a detector located in the first position, the detector configured to capture light in the second band reflected from the eye of the user through the pancake lens and reflected from the beamsplitter, and
• a varifocal element configured to adjust at least one of the front optical element or the back optical element to change a focal length of the pancake lens based at least in part on the determined eye tracking information.

A head-mounted display (HMD) comprising:

• an optics assembly configured to direct image light in a first band from an electronic display to an eye box, the optics assembly including one or more optical elements that are positioned along an optical axis, and the eye box is a region in space occupied by an eye of a user of the HMD;
• a compound curved beamsplitter including a first region with a first curvature, a second region with a second curvature, a first portion with a distinct third curvature joining the first region and the second region curved such that an angle between the first region and the optical axis is larger than an angle between second region and the optical axis, a third region, and a second portion joining the second region and the third region curved such that an angle between the third region and the optical axis is larger than the angle between the second region and the optical axis, the beamsplitter positioned along the optical axis between the optics assembly and the electronic display and is configured to redirect light in a second band passing through the optics assembly toward a first position and transmit light in the first band;
• and
• an eye tracking unit configured to generate eye tracking information, the eye tracking unit comprising:
• a detector located in the first position, the detector configured to capture light in the second band reflected from the eye of the user through the optics assembly and reflected from the beamsplitter, and
• a controller configured to determine eye tracking information using the captured light in the second band;
• and
• wherein the HMD is configured to adjust an image displayed on the electronic display based on the eye tracking information.