The Meta AR VR patent introduces a Pancake lens with a controlled curvature

Pancake lens with controlled curvature.

The device 100 shown in Figure 1 comprises a display 105, a first lens 115 comprising a partial reflector 120, a quarter waveplate 125 comprising a partial reflector 120 and comprising a reflective polarizer 135 and an optional substrate 140. If the reflection polarizer 135 includes a cholesteroid reflection polarizer, the quarter wave plate 125 can be omitted.

Figure 2 shows a device consisting of a display and an optical configuration containing a zoom lens assembly. The device 200 comprises a display 205, a first lens assembly 215 and a second lens assembly 230. The first lens assembly 215 has a partial reflector 220 supported by one surface of the first lens and a quarter wave plate 225 supported on the opposite surface of the first lens.

The second lens assembly 230 comprises a reflective polarizer 232 on one surface of the second lens assembly and an actuator 235 on an opposite surface of the second lens assembly. The first and second lens assemblies can each include lenses, such as refractive lenses. The actuator 235 may be a multilayer actuator. The display 205 emits display light, illustrated by an example beam 210 that forms divergent ray beams 240 and 245. The distance from the image to the user's eye may be called the adjustment distance, and the adjustment distance can be adjusted by using one or more electrical signals to control the actuator.

In one example, the adjustable lens in the second lens assembly 230 may have a radius of curvature in the range of about 150 mm, e.g., about 50 mm.

Figure 3 shows the light propagation through the cross-section of the device 300. The embodiment device 300 comprises a display 305, a first lens assembly 315 and a second lens assembly 330. The first lens assembly 315 may comprise a partial reflector 320 supported by one surface of the first lens and a quarter wave plate 325 supported by a opposite surface.

The second lens assembly 330 may include a lens supporting a reflective polarizer 332 on one surface and an actuator 335 on another surface. The display 305 may be configured to emit light, such as a beam 310 that can form a collimated ray beam 340 and a 345. The collimation of beams 340 and 345 produces images that are displayed at a greater distance from the user.

In one example, the second lens assembly 330 may include a lens, such as an adjustable lens, whose radius of curvature is in the range of about 150 mm, e.g., about 50 mm. In one example, the transmittance of the second lens assembly can be adjusted using an actuator 335.

Figure 4 is an example optical configuration of at least one lens with tunable transmittance. The device 400 may include a display 405 and an optical configuration, including a first lens assembly 470 and a second lens assembly 475. The first lens assembly 470 may include an actuator 410, a reflector 415, and an optional quarter wave plate 420.

The second lens assembly 475 may comprise a reflective polarizer 425 and a second lens 430, wherein the second lens 430 comprises an actuator supported on the surface of the second lens.

In an example, the exemplary device may include a display and at least one lens assembly. Exemplary lens assemblies can typically be planar and can include e.g. fluid lenses, diffractive elements, or Fresnel lenses or both in one or two lens assemblies.

At least one of the first and second lens assemblies can have adjustable optical parameters such as light transmittance and cylindricity. For example, at least one of the first and second lens components may include a surface with a controlled curvature, such as a membrane for a fluid lens, a curved surface for a controllable electro-optical solid lens, or an actuator-controlled lens that includes an elastomeric material.

In one embodiment, a partial reflective layer may include one or more of the three layers, such as an absorption linear polarizer, a quarter-wave plate, and a partial reflective layer. A partial reflector layer can be configured to reflect about 50% of the light and transmit about 50% of the light, for example, for visible light of at least one wavelength.

Figure 5 shows an example optical configuration of the device 5000 with at least one lens with tunable transmittance and an absorptive optical polarizer. The device 500 may include a display 505, a first lens assembly 570, and a second lens assembly 575. The first lens assembly 570 may include an actuator 510, a reflector 515, and a first lens 520 that can further support an optional quarter-waveplate. The second lens assembly 575 may include a reflective polarizer 525, a combination of a second lens and an absorbing polarizer 535, and a second actuator 530.

The optical structure of Figure 5 can be modified to reduce reflections from, for example, objects outside the device. In this example, the lens 575 supports an absorption polarizer 535, wherein the blocking polarization of the absorption polarizer 535 can be parallel to the blocking polarization of the reflective polarizer 525 to reduce the reflection effect.

Another exemplary apparatus 600 shown in Figure 6 includes an optical structure with at least one lens with tunable transmittance and at least one actuator. The device 600 comprises a display 605, a first lens assembly 670 and a second lens assembly 675. The first lens assembly 670 may include an actuator 610, a reflector 615, an optional quarter waveplate 620, a partial reflector 625, and a first lens 630.

The second lens assembly 675 may comprise a reflective polarizer 635 located on the surface of the second lens 640 and a second actuator 645 located on the opposite surface of the second lens 640. The second lens assembly may also include an absorbent polarizer. For example, the second lens 640 can support an optional absorbent polarizer layer, which can absorb any polarization of light that is blocked by the reflective polarizer 635.

The second actuator 645 can be either single or dual actuators and can be omitted in specific examples. In this and other examples, the order of the optical elements within the lens assembly can be reversed and/or rearranged. The display 605 can be configured to emit unpolarized light.

Light 650, if unpolarized, can pass through the first lens assembly 670. The actuator 610 may include a transparent multilayer structure consisting of a plurality of electrically active layers and an arrangement of transparent electrodes configured to apply an electrical signal to the electroactive layer. In one example, a controller can be used to provide an adjustable electrical signal to at least one layer of a multilayer actuator. Actuator 610 can be either single or double actuator.

The light 650 can pass through the reflector 615 and form a circularly polarized light through the quarter wave plate 620. For example, a reflector 615 may include a linear polarizer. The ray 650 passes through the first lens assembly, including a partial reflector 625 and a first lens 630, to provide the light 655. The first lens may support an optical retarder as described a quarter wave plate 620. The light 655 can then be reflected by the second lens assembly 675 to form the light 660, and then, when the user wears the device, it can be reflected back as light 665 through the second lens assembly, for example, towards the user's eyes.

The designation of the first and second lens components can be arbitrary. In one example, the device can be configured so that display light passes through the first lens assembly, is reflected by the second reflector of the second lens assembly, is reflected by the first reflector of the first lens assembly, and then reaches the user's eye through the second lens assembly.

Actuators can be used to adjust adjustable lenses within the respective lens assembly. In an example, at least one actuator can be combined with one or more optics in the sample lens assembly, such as tunable lenses or other optical elements. A lens assembly that includes an actuator may be referred to as a first lens assembly, and a second lens assembly may include an actuator and an adjustable lens, or may not include an actuator.

In one example, an actuator can change the polarization state of light transmitted through an actuator, and this can be included in the optical design of the optical structure.

Figure 7 shows an example actuator 700 with an actuator configuration that does not substantially alter the degree of polarization of light passing through the actuator 700, even for actuators with a high birefringence layer. The Actuator 700 can include a clock stack of birefringent actuator layers.

The Actuator 700 display has nine actuator layers. For example, an example actuator can include 1-50 layers, such as 1-20 layers, or another number of layers. The first actuator layer to the ninth actuator layer are represented as the actuator layer and 755, respectively, where each actuator layer has a high in-plane refractive index Nx, a low in-plane refractive index ny, and a refractive index orthogonal to the in-plane refractive index nz. The value of the orthogonal component nz can be less than ny, or greater than nx, or something between nx and ny.

In this case, the clock stack of the layers can include a multilayer structure that includes birefringent layers, each with an in-plane optical axis direction of the respective layer with an angular step shift from the optical axis direction of at least one adjacent layer.

In one example, the optical axis of the layer can be rotated in a stepwise fashion in the direction perpendicular to the layer. The optical axis direction of the layers can describe the circle that advances through a multilayer structure.

In one example, the approximate spiral structure provided by the rotation of the optical axis can provide a waveguide effect. Layers can include oriented piezoelectric materials. Example layers can include uniaxial directional PVDF. Example actuators can provide control over spherical, cylindrical, and optical axis parameters.

In one example, a multilayer actuator can include multiple electroactive layers interlaced with the electrode layer. Multilayer actuators may consist of multiple electroactive layers intertwined with non-electroactive layers, which can support the electrode layer on one or both of them.

The actuator 800 shown in Figure 8 may consist of two single-axis actuator layers 850 and 855, where the nx vectors of each layer are approximately orthogonal to each other, as shown by arrows 830 and 860.

The Actuator 800 can be configured to reduce or essentially eliminate the birefringence effect of polarization of the light transmitted through the actuator. In one example, multiple actuator layers include two birefringence layers with orthogonal optical axes, where the optical axes of each layer can be in the plane of their respective layers.

In one example, the actuator 800 can have a multi-layer structure where a single actuator layer can provide a single-axial force that can be individually controlled. A birefringent layer can be an optical uniaxial layer. Multiple actuator layers may include multiple uniaxial layers, where each uniaxial layer has an optical axis, and the orientation of the optical axis within the plane of each uniaxial layer can differ by at least 10 degrees from the orientation of the adjacent uniaxial layer.

In this case, the adjacent electrically active layers can be separated by the non-electrically active layers but are otherwise adjacent. During normal operation, the non-electrically active layer may not respond to the electrical signal supplied to the actuator, altering the light transmittance of the lens assembly to any perceptible degree.

In one example, an electric field applied to one or more actuator layers can induce electrostriction of the actuator layers, for example in a direction parallel to or orthogonal to the electric field. In one example, the curvature of the membrane can be adjusted using electrical stretching within one or more actuator layers, for example, to adjust the light transmittance of a tunable fluid lens.

In one example, the electrical expansion within one or more actuator layers can be used to adjust the transmittance and/or cylindricity of a tunable fluid lens. In one example, a symmetrical arrangement of the electrical stretching effect can be used to adjust the light transmittance. In one example, the asymmetrical arrangement of the stretching effect can be used to obtain aspheric optical parameter adjustments, such as cylindricity adjustments.

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