US Patent 10989927 Image frame synchronization in a near eye display

A method includes providing frames of video data for being displayed by a head mounted display (HMD). Pixel data is encoded in a pixel of at least some of the video data frames, the encoded pixel data defining a focal state of an optics block of the HMD for displaying the respective frame of the video data to a user. The predetermined focal state is determined from a plurality of available focal states of the optics block, each focal state corresponding to a different focal plane of a virtual image generated based on the video data. The pixel used for encoding may be disposed outside a region of the frame that is displayable by the HMD.