Patent Application
20240036307
This disclosure relates to the technical field of optical display system, and more specifically, to an exit pupil steering device, an optical display system and an electronics apparatus.
An head-mounted display (HMD) projects virtual images to a viewer's eye. Field of view of an HMD determines the size of virtual image perceived by the viewer. Eye box size measures the movable range of viewer's eye, out of which no image light enters use's eye.
In conventional HMDs, there is generally a trade-off between field of view and exit pupil size due to the conservation of optical etendue. To increase optical etendue often means to enlarge size of optical modules, which compromises wearing comfort. To steer the location of exit pupil can significantly improve the movable range of viewer's eye and can avoid the issue of optical etendue conservation. Conventional pupil steering methods are generally based on changing incident light angle on optical elements like a diffraction lens. These methods can induce serious aberrations because the wave front of optical element is usually fixed and work well only for one incident angle.
One object of this disclosure is to provide a new technical solution for exit pupil steering.
According to a first aspect of the present disclosure, there is provided an exit pupil steering device, comprising: at least one first lens coupler module, each of which includes: a first controllable polarization converter, which can convert an incident light of a first polarization state into a second polarization state under control, and a first diffractive lens, which diffracts the incident light of the first polarization state to a first pupil location of a viewer and passes the incident light of the second polarization state, or which passes the incident light of the first polarization state and diffracts the incident light of the second polarization state to the first pupil location; and a second lens coupler module, which is placed after the first lens coupler module and diffracts the incident light to a second pupil location of the viewer.
According to a second aspect of the present disclosure, there is provided an optical display system, comprising: an optical image-generating display apparatus, which generates display light; and the exit pupil steering device according to an embodiment, which receives the display light as the incident light and diffracts the incident light so that an exit pupil of the optical display system is steered to match a pupil location of a viewer.
According to a third aspect of the present disclosure, there is provided an electronics apparatus, including the optical display system according to an embodiment.
According to an embodiment of this disclosure, an optical display system can provide a relatively large movable range without significantly compromising the optical performance.
Further features of the present disclosure and advantages thereof will become apparent from the following detailed description of exemplary embodiments according to the present disclosure with reference to the attached drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention.
Various exemplary embodiments of the disclosure will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the disclosure unless it is specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods and apparatus as known by one of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all of the examples illustrated and discussed herein, any specific values should be interpreted to be illustrative only and non-limiting. Thus, other examples of the exemplary embodiments could have different values.
Notice that similar reference numerals and letters refer to similar items in the following figures, and thus once an item is defined in one figure, it is possible that it need not be further discussed for following figures.
In various embodiments, an exit pupil steering device may comprises: at least one first lens coupler module and a second lens coupler module. Each of the first lens coupler module includes: a first controllable polarization converter and a first diffractive lens. The first controllable polarization converter can convert an incident light of a first polarization state into a second polarization state under control. The first diffractive lens diffracts the incident light of the first polarization state to a first pupil location of a viewer and passes the incident light of the second polarization state, or which passes the incident light of the first polarization state and diffracts the incident light of the second polarization state to the first pupil location. The second lens coupler module is placed after the first lens coupler module and diffracts the incident light to a second pupil location of the viewer. The first pupil location and the first pupil location are different. That is, the first diffractive lens diffracts the incident light at a first exit pupil, and the second lens coupler module diffracts the incident light at a second exit pupil different from the first exit pupil.
Here, with the exit pupil steering device, an optical display system can provide a relatively large movable range without significantly compromising the optical performance.
For example, the first diffractive lens is a diffractive liquid crystal lens. The incident light may be circularly polarized. The first polarization state and the second polarization state are of opposite handedness. In an example, the first polarization state is right handedness polarization state and the second polarization state is left handedness polarization state. Alternatively, the first polarization state is left handedness polarization state and the second polarization state is right handedness polarization state.
In an example, the first controllable polarization converter is controlled to convert the incident light of the first polarization state into a second polarization state, and the first diffractive lens passes the incident light of the second polarization state.
In another example, the first controllable polarization converter is controlled to convert the incident light of the first polarization state into a second polarization state, and the first diffractive lens diffracts the incident light of the second polarization state.
In a still another example, the first controllable polarization converter is controlled to pass the incident light of the first polarization state, and the first diffractive lens passes the incident light of the first polarization state.
In a further another example, the first controllable polarization converter is controlled to pass the incident light of the first polarization state, and the first diffractive lens diffracts the incident light of the first polarization state.
For example, the at least one first lens coupler module includes two first lens coupler modules, and the first diffractive lenses of the two first lens coupler modules diffract the incident lights of different polarization states. Furthermore, the first diffractive lenses of the at least two lens coupler modules may diffract the incident light to different first pupil locations or at different first exit pupils.
In an embodiment, the second lens coupler module may include: a second controllable polarization converter and a second diffractive lens. The second controllable polarization converter converts the incident light of the first polarization state into the second polarization state. The second diffractive lens diffracts the incident light of the second polarization state.
For example, the second diffractive lens diffracts the incident light which has a polarization state opposite to that of that of the first diffractive lens of the last first lens coupler module.
The first diffractive lens of the last first lens coupler module may pass the incident light of the first polarization state or the second polarization state, and the second diffractive lens can diffract the incident light of the first polarization state or the second polarization state.
In another embodiment, the second lens coupler module may include: a second controllable polarization converter and a second diffractive lens. The second controllable polarization converter converts the incident light of the second polarization state into the first polarization state. The second diffractive lens diffracts the incident light of the first polarization state. The second diffractive lens may be a diffractive liquid crystal lens.
In an embodiment, the second lens coupler module includes a second diffractive lens diffracts the incident light from a last first lens coupler module before the second lens coupler module.
For example, the second diffractive lens diffracts the incident light which has a polarization state opposite to that of that of the first diffractive lens of the last first lens coupler module. In this situation, the first diffractive lens of the last first lens coupler module passes the incident light of the first polarization state or the second polarization state, and the second diffractive lens diffracts the incident light of the first polarization state or the second polarization state.
The first and/or second diffractive lens, which may be diffractive liquid crystal lens, may focus the incident light into a first reflective order. The diffractive lens may be fabricated with a patterned bottom photo-alignment layer and cholesteric liquid crystal placed on the photo-alignment layer. The diffractive lens is fabricated by polarization volume holography to directly record volume birefringence by exposure of two interfering beams.
For example, the polarization converter may be made of a homogeneous LC cell. The cell gap of the homogeneous LC cell may be 2 micrometers. The LC cell may have birefringence of 0.284.
In various embodiments, an optical display system may comprises: an optical image-generating display apparatus, which generates display light; and the exit pupil steering device as described above. The exit pupil steering device receives the display light as the incident light and diffracts the incident light so that an exit pupil of the optical display system is steered to match a pupil location of a viewer.
For example, the optical image-generating display apparatus is programmable/controllable, and may be configured to output circularly polarized light, such as right handedness light or left handedness light. The optical image-generating display apparatus may include a programmable image-generating component and an imaging optical component. The imaging optical component may include a bi-convex lens. For example, the image-generating component is at least one of an organic light emitting diode (OLED) display, a liquid crystal on silicon (LCOS) display, a laser-scanning display with micro-electromechanical system (MEMS), and a micro light emitting diode (μLED) display. In an example, a circular polarizer is incorporated between the image-generating component and the imaging optical component to produce circularly polarized light output. The imaging optical component may include a plurality of lenses, which are refractive-type or diffractive-type, and have a plurality of reflective surfaces.
In an embodiment, the optical display system may further comprises a controlling unit, which controls the first controllable polarization converter of the first lens coupler module.
In another embodiment, the optical display system may further comprises an eye tracking apparatus. The eye tracking apparatus detects the location of a viewer's eye pupil and provides the location to the controlling unit. The controlling unit can control the first controllable polarization converter according to the location.
For example, the controlling unit steers light from the optical image-generating display apparatus to viewer's eye pupil by turning on the lens coupler module with closer distance to viewer's eye pupil, according to the location of the eye pupil determined by the eye tracing apparatus. The plurality of lens coupler modules can be independently controlled whether to diffract or transmit light. According to the eye pupil location determined by the eye tracking system, the controlling unit can turn on the lens coupler module with the closest focus point to the eye pupil, so that light can be steered to viewer's eye.
In another example, the lens coupler module can be turned on or off, or the first diffractive lens may be activated, by the controllable polarization converter. For example, the first controllable polarization converter has two possible states that can be selected by programming. In state one, the first controllable polarization converter reverts the handedness of incident circularly polarized light. In state two, the first controllable polarization converter preserves the polarization state of incident circularly polarized light.
In this disclosure, various embodiments relate to exit pupil steering device, which can be used in an optical display system. The optical display system can be an augmented reality system that includes a controllable optical image-generating apparatus and an optical image-viewing apparatus. Various embodiments may also relate to associated methods and applications. In various embodiments, exit pupil of optical display system can be steered to match the location of a viewer's pupil. Various embodiments can be used in wearable display devices including virtual and/or augmented reality devices.
For example, the electronics apparatus may be an HMD. The HMD includes an optical display system, which includes an exit pupil steering device. The exit pupil steering device is used for exit pupil steering for the HMD. The HMD can have a wide field of view and a large exit pupil size.
In an exemplary, non-limiting embodiment, the optical display system can include a controllable optical image-generating display apparatus, an exit pupil steering apparatus, an eye tracking apparatus and a controlling unit. In a non-limiting exemplary embodiment, the optical image-generating apparatus has an optical axis and includes a programmable/controllable image-generating component; an imaging optical component. For example, the imaging optical component is disposed to magnify and collimate the image-generating component. The programmable/controllable image-generating component may be configured to output circularly polarized light, i.e. it is adapted to generate a polarized image output.
The exit pupil steering apparatus may include a plurality of lens coupler modules. Each lens coupler module includes a controllable polarization converter and a diffractive liquid crystal lens. The controllable polarization converter can change the polarization state of light with a certain oblique incident angle under an applied controlling voltage from the controlling unit. The polarization state is changed between circular polarization with opposite handedness. The diffractive liquid crystal lens focuses the light with one circular polarization state to a point and let light with the other polarization state pass directly through. The eye tracking apparatus detects the location of viewer's eye pupil and provides this information to the controlling unit.
In some embodiments, the exit pupil steering apparatus includes a plurality of lens coupler modules. Each lens coupler module has a distinct focus point. By controlling the polarization converter in each lens coupler module, the lens function can be switched between on and off state. The input light can be selectively diffracted by a specific lens coupler module. With the pupil position information provided by the eye tracking apparatus, the controlling unit can decide which lens coupler module to function. The wave front of each diffractive liquid crystal is recorded separately and can be designed to minimize optical aberrations.
The eye tracing apparatus 120 tracks the position of eye pupil and deliver the information to controlling unit 130. When the viewer's eye 150 is moved and the eye pupil position is changed to 152 in
The relation of handedness among display light 140, diffractive liquid crystal lenses 111 and 113 are only for purpose of description and should not be a limitation. For example, in some embodiments, light 140 may have the same handedness as that can be processed by the diffractive liquid crystal lens 113. In this situation, the electronic switch 132 shall be turned off in order for light 140 to be diffracted by the liquid crystal lens 113. In some embodiments, the light handedness for liquid crystal lens 111 may be different from that for the liquid crystal lens 113. When display light 140 passes liquid crystal lens 113, the electronic switch 131 should be turned off in order for display light 140 to be diffracted by liquid crystal lens 113. In this situation, the electronic switch 131 may be omitted.
As shown in
The controllable polarization converter has the function of switching the handedness of incident circularly polarized light, which can be controlled with an electronic switch. In some embodiments, it includes a homogeneous liquid crystal cell with two compensation films, as shown in
In one embodiment of the disclosure, the polarization converter 112/114 is made of a homogeneous LC cell. The cell gap is 2 micrometers. The LC material has birefringence of 0.284. The input light is right circularly polarized light with Stokes parameter S3=1, with 45 degrees of incident angle. When a voltage is applied, the measured Stokes parameter S3 of output light is shown in
In one embodiment of the disclosure, two diffractive liquid crystal lenses with opposite responses to circularly polarized light are used. One has high efficiency for LCP light. The other has high efficiency for RCP light. The two lenses both work for oblique incident light with incident angle of 45 degrees. The focal points of two lenses have a spatial separation of 8 millimeters. The lenses are shown in
In one embodiment of the disclosure, the diffractive lens set 501 with two diffractive liquid crystal lenses whose polarization responses are opposite are used to form images with laser beam scanner. The polarization converter 112/114 is used to switch between two viewpoints. The image 601 viewed through the first viewpoint is shown in
Although some specific embodiments of the disclosure have been demonstrated in detail with examples, it should be understood by a person skilled in the art that the above examples are only intended to be illustrative but not to limit the scope of the disclosure.
This application is a National Stage of International Application No. PCT/CN2022/075506, filed on Feb. 8, 2022, which claims priority to U.S. Application No. 63/146,781, filed Feb. 8, 2021, both of which are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/075506 | 2/8/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63146781 | Feb 2021 | US |
