# US 10,371,872 B1 · 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

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- Number: US 10,371,872 B1
- Document ID: US10371872B1
- Status: Granted
- Kind: B1
- Application number: 16/163,306
- Filed: 2018-10-17
- Granted: 2019-08-06
- Earliest claimed: 2016-11-16
- Assignees: Facebook Technologies, LLC
- Applicants: Facebook Technologies, LLC
- Inventors: Lu Lu; Scott Charles McEldowney; Pasi Saarikko
- Web page: https://patentgrep.com/patent/US10371872B1

## CPC

- G02B 3/14: of variable focal length
- G02B 26/004: {based on a displacement or a deformation of a fluid}
- G02F 1/13: based on liquid crystals, e.g. single liquid crystal display cells
- G02F 1/133528: {Polarisers}
- G02F 1/13363: Birefringent elements, e.g. for optical compensation
- G02F 1/29: for the control of the position or the direction of light beams, i.e. deflection
- G02B 27/0093: {with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking}
- G02B 27/0172: {characterised by optical features}
- G02F 1/133541: {Circular polarisers}
- G02F 1/133638: {Waveplates, i.e. plates with a retardation value of lambda/n}
- G02F 2413/01: Number of plates being 1
- G02F 2413/05: Single plate on one side of the LC cell
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

A varifocal block includes liquid crystal (LC) lens and a liquid lens structure in optical series. The LC lens has a 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. The liquid lens structure comprises a transparent substrate layer, a deformable membrane, and a volume of liquid enclosed between the transparent substrate layer and the deformable membrane. The deformable membrane has an adjustable range of optical power dependent on an adjustable curvature of the deformable membrane. The plurality of optical states of the LC lens and the adjustable range of optical power of the liquid lens structure together provide a continuous range of optical power for the varifocal block.

## Claims

### Claim 1

A 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.

### Claim 2 (depends on 1)

The varifocal block of claim 1, wherein the adjustable range of optical power of the liquid lens structure is a continuous adjustable range of optical power.

### Claim 3 (depends on 1)

The varifocal block of claim 1, wherein the range of adjustment of optical power for the varifocal block is a continuous range of adjustment of optical power.

### Claim 4 (depends on 1)

The varifocal block of claim 1, further comprising a switchable half waveplate, and the LC lens is positioned between the liquid lens structure and the switchable half waveplate.

### Claim 5 (depends on 4)

The varifocal block of claim 4, wherein, based in part on a state of the switchable half waveplate and a state of the LC lens, the range of adjustment of optical power for the varifocal block is selected from the group consisting of:
d to (D+d), −d to (−d+D), and 0 to D,
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.

### Claim 6 (depends on 1)

The varifocal block of claim 1, further comprising a circular polarizer, and the LC lens is positioned between the liquid lens structure and the circular polarizer.

### Claim 7 (depends on 1)

The varifocal block of claim 1, further comprising a circular polarizer that is positioned between the liquid lens structure and the LC lens.

### Claim 8 (depends on 1)

The varifocal block of claim 1, wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.

### Claim 9 (depends on 1)

The varifocal block of claim 1, wherein a color dispersion caused by the liquid lens structure is opposite of a color dispersion caused by the LC lens.

### Claim 10 (depends on 1)

The varifocal block of claim 1, wherein the liquid lens structure comprises:
a transparent substrate layer;
a deformable membrane, wherein the deformable membrane has an adjustable curvature; and
a volume of liquid enclosed between the transparent substrate layer and the deformable membrane;
wherein the adjustable range of optical power of the liquid lens structure is based in part on the adjustable curvature of the deformable membrane.

### Claim 11

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.

### Claim 12 (depends on 11)

The HMD of claim 11, wherein the adjustable range of optical power of the liquid lens structure is a continuous adjustable range of optical power.

### Claim 13 (depends on 11)

The HMD of claim 11, wherein the range of adjustment of optical power for the varifocal block is a continuous range of adjustment of optical power.

### Claim 14 (depends on 11)

The HMD of claim 11, further comprising one of:
a switchable half waveplate, and the LC lens is positioned between the liquid lens structure and the switchable half waveplate;
a first circular polarizer, and the LC lens is positioned between the liquid lens structure and the first circular polarizer; and
a second circular polarizer that is positioned between the liquid lens structure and the LC lens.

### Claim 15 (depends on 11)

The HMD of claim 11, wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.

### Claim 16 (depends on 11)

The HMD of claim 11, wherein a color dispersion caused by the liquid lens structure is opposite of a color dispersion caused by the LC lens.

### Claim 17 (depends on 11)

The HMD of claim 11, wherein the liquid lens structure comprises:
a transparent substrate layer;
a deformable membrane, wherein the deformable membrane has an adjustable curvature; and
a volume of liquid enclosed between the transparent substrate layer and the deformable membrane;
wherein the adjustable range of optical power of the liquid lens structure is based in part on the adjustable curvature of the deformable membrane.

### Claim 18

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.

### Claim 19 (depends on 18)

The method of claim 18, further comprising:
presenting content from an electronic display of a head-mounted display at an image plane associated with the optical power of the varifocal block.

### Claim 20 (depends on 18)

The method of claim 18, wherein selecting the optical power of the liquid lens structure from the adjustable range of optical powers, comprises:
selecting a curvature for a deformable membrane of the liquid lens.