Varifocal structure comprising a liquid lens structure in optical series with a liquid crystal lens in a head-mounted display and method of adjusting an optical power of the varifocal structure

A head-mounted display (HMD) comprising:

• a varifocal block that receives content from an electronic display, and presents the content over a plurality of image planes that are associated with different optical powers of the varifocal block, the varifocal block comprising:
• a liquid crystal (LC) lens that has an additive state that adds optical power to the LC lens and a subtractive state that removes optical power from the LC lens;
• and
• a liquid lens structure in optical series with the LC lens, the liquid lens structure having an adjustable range of optical power;
• wherein a range of adjustment of optical power for the varifocal block is based in part on the additive state of the LC lens, the subtractive state of the LC lens, and the adjustable range of optical power of the liquid lens structure, and each value of optical power over the range of adjustment of optical power for the varifocal block corresponds to a different image plane of the plurality of image planes.

A method comprising:

• adjusting an optical power of a varifocal block, comprising:
• selecting a liquid crystal (LC) optical state from a plurality of optical states for a LC lens of the varifocal block, the plurality of optical states including an additive state that adds optical power to the LC lens and a subtractive state that removes optical power from the LC lens,
• selecting an optical power of a liquid lens structure of the varifocal block from an adjustable range of optical power, the liquid lens structure in optical series with the LC lens,
• adjusting the LC lens to the selected optical state and the liquid lens structure to the selected optical power, and a combined optical power of the LC lens and the liquid lens structure is the optical power of the varifocal block selected from a range of adjustment of optical power for the varifocal block that is based in part on the additive state of the LC lens, the subtractive state of the LC lens, and the adjustable range of optical power of the liquid lens structure.