METHOD AND SYSTEM FOR PATTERNING A LIQUID CRYSTAL LAYER
An optical master is created by using a nanoimprint alignment layer to pattern a liquid crystal (LC) layer. The nanoimprint alignment layer and the LC layer constitute the optical master. The optical master is positioned above a photoalignment layer. The optical master is illuminated and light propagating through the nanoimprinted alignment layer and the LC layer is diffracted and subsequently strikes the photo-alignment layer. The incident diffracted light causes the pattern in the LC layer to be transferred to the photo-alignment layer. A second LC layer is deposited onto the patterned photo-alignment layer, which subsequently is used to align the molecules of the second LC layer. The second LC layer in the patterned photo-alignment layer may be utilized as a replica optical master or as a diffractive optical element for directing light in optical devices such as augmented reality display devices.
1 . An eye-tracking system usable in a wearable display device, the eye-tracking system comprising:
a liquid crystal reflector comprising one or more cholesteric liquid crystal (CLC) layers each comprising a plurality of chiral structures, wherein each of the chiral structures comprises a plurality of liquid crystal molecules that extend in a layer depth direction that is substantially perpendicular to a major surface of the liquid crystal reflector and that are successively rotated in a first rotation direction, wherein the liquid crystal reflector is arranged to be substantially reflective of first light in a first wavelength range, and wherein the liquid crystal reflector is arranged to be substantially transmissive of second light in a second wavelength range;
an illumination source configured to emit, toward the liquid crystal reflector, the first light in the first wavelength range such that the first light is reflected by the liquid crystal reflector and directed toward an eye of a user of the wearable display device; and
a camera configured to generate eye images of the eye by receiving a portion of the first light that is reflected by the eye and that is subsequently reflected by the liquid crystal reflector toward the camera.
2 . The eye-tracking system of claim 1 , wherein the first light is infrared light, and wherein the second light is visible light.
3 . The eye-tracking system of claim 1 , wherein the first light is infrared light, and wherein the first wavelength range is about 600 nm to about 1.4 μm.
4 . The eye-tracking system of claim 1 , wherein each of the CLC layers are configured to:
reflect light that has a same handedness of polarization as the first rotation direction; and
transmit light that has an opposite handedness of polarization relative to the first rotation direction.
5 . The eye-tracking system of claim 1 , wherein arrangements of the liquid crystal molecules of the chiral structures vary, with a period, in a lateral direction that is substantially perpendicular to the layer depth direction.
6 . The eye-tracking system of claim 5 , wherein a ratio between a first wavelength of the first light and the period is between about 0.5 and 2.0.
7 . The eye-tracking system of claim 1 , wherein the liquid crystal molecules of the chiral structures are tilted relative to a direction substantially normal to the layer depth direction.
8 . The eye-tracking system of claim 1 , wherein the illumination source and the camera are arranged off-axis relative to an optical axis of the second light incident on the eye.
9 . The eye-tracking system of claim 1 , wherein the illumination source is arranged such that the first light emitted by the illumination source is incident on the liquid crystal reflector at an angle exceeding about 50° relative to the layer depth direction, and wherein the camera is arranged to receive the first light reflected by the liquid crystal reflector at the angle exceeding about 50° relative to the layer depth direction.
10 . The eye-tracking system of claim 1 , wherein the illumination source is arranged such that the first light emitted by the illumination source is incident on the liquid crystal reflector at an angle exceeding about 60° relative to the layer depth direction, and wherein the camera is arranged to receive the first light reflected by the liquid crystal reflector at the angle exceeding about 60° relative to the layer depth direction.
11 . The eye-tracking system of claim 1 , wherein the illumination source is arranged such that the first light emitted by the illumination source is incident on the liquid crystal reflector at an angle exceeding about 70° relative to the layer depth direction, and wherein the camera is arranged to receive the first light reflected by the liquid crystal reflector at the angle exceeding about 70° relative to the layer depth direction.
12 . The eye-tracking system of claim 1 , wherein the illumination source is arranged such that the first light emitted by the illumination source is incident on the liquid crystal reflector at an angle exceeding about 80° relative to the layer depth direction, and wherein the camera is arranged to receive the first light reflected by the liquid crystal reflector at the angle exceeding about 80° relative to the layer depth direction.
13 . The wearable display device comprising the eye-tracking system of claim 1 .
14 . The wearable display device of claim 13 , further comprising one or more waveguides arranged to convey virtual image content to the eye of the user, wherein the liquid crystal reflector is arranged on a surface of one of the one or more waveguides.