Head mounted display with active optics feedback and calibration

A method for use with a head mounted display (HMD), the method comprising:

• focusing, with an adjustable lens, display light generated by a display layer of the HMD for presentation to a user of the HMD;
• receiving a calibration image generated by a camera of the HMD in response to calibration light emitted by an array of point light sources through the adjustable lens and directed to the camera by an optical combiner, wherein the array of point light sources are disposed between the display layer and the adjustable lens to emit the calibration light through the adjustable lens to the optical combiner, wherein the calibration image includes an array of points corresponding to the array of point light sources;
• processing the calibration image to determine a distortion in the array of points included in the calibration image;
• and
• generating one or more control signals to adjust an optical power of the adjustable lens to compensate for the distortion.

A head mounted display (HMD), comprising:

• a camera;
• a display layer configured to emit display light;
• a first illumination layer having an array of point light sources configured to emit calibration light, wherein the first illumination layer is transmissive to the display light;
• an optical combiner configured to pass the display light to a front side of the HMD and to direct the calibration light to the camera;
• a second illumination layer disposed between the optical combiner and the front side of the HMD, the second illumination layer comprising a plurality of in-field light sources configured to emit infrared light to illuminate an eye of a user;
• an active optics block that includes an adjustable lens disposed between the first illumination layer and the optical combiner, the adjustable lens configured to pass the calibration light to the optical combiner and to focus the display light for the user of the HMD, wherein the active optics block is further configured to adjust an optical power of the adjustable lens based on a calibration image captured by the camera responsive to the calibration light, and wherein the optical combiner is further configured to receive reflected infrared light that is reflected by the eye of the user and to direct the reflected infrared light towards the camera for generating an eye-tracking image for tracking the eye;
• and
• a switchable half-wave plate disposed between the camera and the optical combiner for selectively multiplexing between the calibration light and the infrared light.