Polarization conversion using a polarizing volume grating

Abstract

An example provides an optical device, comprising: a light source configured to output unpolarized light; a polarization beam splitter configured to split the unpolarized light into light of a first polarization state and light of a second polarization state; and a polarization volume grating configured to receive the light of the first polarization state and the light of the second polarization state, and transmit the light of the first polarization state without changing the light of the first polarization state into a different polarization state, and convert the light of the second polarization state into the first polarization state, thereby forming polarized output light.

Description

BACKGROUND OF THE INVENTION

[0001] Many optical systems use the polarization of light as a property to direct and / or modulate light within the optical system. For example, many display devices use liquid crystal display (LCD) panels to spatially modulate the angle and / or phase of polarized light to display an image. Similarly, optical systems can also use polarization-sensitive components to direct light within the system, such as by using polarization beam splitters and liquid crystal elements and other optical components. SUMMARY OF THE INVENTION

[0002] The present invention content is provided to introduce a selection of concepts in a simplified form that will be further described in the detailed description below. The present invention content is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. In addition, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages noted in any part of this disclosure.

[0003] One example provides an optical device including a light source configured to output unpolarized light; a polarization beam splitter configured to divide the unpolarized light into light of a first polarization state and light of a second polarization state; and a polarization volume grating configured to receive the light of the first polarization state and the light of the second polarization state, transmit the light of the first polarization state without changing it to a different polarization state, and convert the light of the second polarization state to the first polarization state, thereby forming polarized output light. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 The polarization volume grating is schematically shown.

[0005] Figure 2 Light passing through the transmissive polarization volume grating is schematically shown.

[0006] Figure 3 A polarization converter including a polarization grating and a transmissive polarization volume grating is schematically shown.

[0007] Figure 4 A polarization converter including a first polarization grating, a transmissive polarization volume grating, and a second polarization grating is schematically shown.

[0008] Figure 5 An optical device including an unpolarized light source and an exemplary polarization converter is schematically shown.

[0009] Figure 6 A flowchart depicting an example method for operating an optical device is shown.

[0010] Figure 7 A block diagram of an example computing device is shown. DETAILED DESCRIPTION

[0011] As described above, many optical systems use polarization as a property to direct and / or modulate light within the optical system. For example, many display devices use liquid crystal display (LCD) panels to spatially modulate the amplitude and / or phase of polarized light to display an image. Similarly, an optical system can use polarization-sensitive components to direct light within the system, and / or direct light exiting the system, e.g., by using components such as polarization beam splitters and liquid crystal or other birefringent beam control elements.

[0012] Some such optical devices can use a light source that emits unpolarized light. Examples of such light sources include vertical cavity surface emitting lasers (VCSELs) and light emitting diodes. In such devices, various types of polarizers can be used to form polarized light from the unpolarized light generated by the light source. Examples include absorption polarizers, such absorption polarizers being used in liquid crystal displays (LCDs), as well as beam splitting polarizers.

[0013] Using a polarizer to form polarized light from unpolarized light results in a loss of more than half of the intensity from the light source. To compensate for this intensity loss, the light source can be operated at a relatively high power to increase the brightness of the light output by the optical device. However, operating the light source at a relatively high intensity also increases the power usage compared to operating the light source at a lower intensity. For mobile battery-powered devices, this can affect how long the device can operate before the battery needs to be recharged.

[0014] To avoid this intensity loss, an optical system can utilize a polarization beam splitter to split the unpolarized light into two components of opposite polarization, rotate the polarization of one component (e.g., with a half-wave plate or other suitable component), and then recombine the light. However, such an arrangement would utilize more space than is available on smaller mobile devices.

[0015] Accordingly, examples related to thin film polarization converters are disclosed that can convert unpolarized light to polarized light with a small intensity loss in a relatively small amount of space. In short, the disclosed examples utilize a polarization beam splitter in combination with a polarization volume grating to form polarized light. These components can be implemented as thin films, and thus can be arranged in a stack to convert unpolarized light to polarized light within a small volume of space. In some examples, an additional polarization grating can be used to redirect the polarized light output by the polarization volume grating. Where used, this additional polarization grating can also be implemented as a thin film. The disclosed examples can be used in any optical system that converts unpolarized light to polarized light, and can be particularly useful in battery-powered devices, where lower power operation can help increase the operating time between battery recharges.

[0016] Figure 1A schematic diagram of a polarization volume grating (PVG) 100 utilizing liquid crystal is shown. An example PVG is described in more detail in "Polarization volume grating with high efficiency and large diffraction angle" by Y. Weng, D. Xu, Y. Zhang, X. Li, and S. Wu in Opt. Express 24, 17746 - 17759 (2016). In the shown PVG 100, the top substrate 116 is configured to change the rotational position of the optical axis of liquid crystal molecules (schematically shown by the helical arrays 102, 104, 106, 108, 110, 112, 114 of arrows) in the xz plane. In addition, the liquid crystal molecules exhibit a helical structure with a period Λ along the y - axis. x This structure generates a series of tilted and periodic refractive index planes 118a, 118b, 118c, and 118d with an inclination angle y , where Λ and Λ x and Λ y are the period lengths in x and y, respectively.

[0017] Depending on the tilt angle the PVG can operate in reflection or transmission. Figure 2 An exemplary transmission PVG 200 is shown. When the incident angle θ i = 0°, the relationship between the tilt angle and the first - order diffraction angle θ diff is given by the following for reflection and transmission PVGs.

[0018]

[0019] The PVG diffracts circularly polarized light with the same handedness as the helical twist. For a transmission PVG, the polarization of the diffracted beam is converted to the orthogonal direction. More specifically, light with right - hand circular polarization (RCP) is converted to light with left - hand circular polarization (LCP), and vice versa. When the incident beam has a right - handedness opposite to the helical twist of the PVG, the incident beam passes through the PVG at the zero - order with no change in its polarization or direction.

[0020] Therefore, a PVG operating in the transmission mode, combined with a polarization beam splitter upstream of the PVG, can be used as a polarization converter to convert unpolarized light to polarized light. Figure 3An exemplary polarization converter 300 including a polarization beam splitter 304 and a PVG 306 is schematically shown. Unpolarized light from a light source 302 is directed onto a polarization beam splitter 304 (PG1). The polarization beam splitter 304 splits the light into a right - hand circularly polarized (RCP) component and a left - hand circularly polarized (LCP) component. Splitting the unpolarized light into two orthogonally polarized components can be done with very little intensity loss. Next, the RCP and LCP light components pass through a PVG 306, which is exemplarily a right - hand PVG here, which converts the incident RCP light into LCP while transmitting the incident LCP light without changing its polarization. The conversion of RCP light to LCP light also results in very little intensity loss. The resulting polarized output light can have an intensity of 95% or more of the original unpolarized light and can be provided to other polarization - sensitive optical components. For example, in the case where the polarization converter 300 is incorporated into a display device (whether a display panel or a display projector), the resulting polarized output light can be provided to an LCD panel or other polarization - sensitive spatial light modulator for image generation. Similarly, in the case where the polarization converter 300 is incorporated into a projector for a depth sensor, the resulting polarized output light can be provided to a polarization - sensitive beam steerer to direct the light to a selected region of the environment being imaged. Although the depicted example uses a right - hand PVG, it should be understood that a left - hand PVG can also be used, which would result in the generation of RCP output light.

[0021] In Figure 3 the example of, based on the periods of the PVG and the polarization beam splitter grating, the output light exits the PVG 306 at an angle with respect to the optical axis of the system (as shown by the arrow between the light source and PG1). PG1 and PVG can be configured to output light at any suitable angle. In some examples, the polarized output light can be emitted at an angle relatively closer to the optical axis, which can facilitate the design of an anti - reflection coating (ARC), help reduce stray light, and reduce the aperture size compared to a polarization converter where the polarized output light is emitted at a higher angle with respect to the optical axis.

[0022] In other examples, additional polarization gratings can be used to redirect the polarized light from the PVG at a desired angle, either along the optical axis or in any other suitable direction. Figure 4 An example polarization converter 400 is schematically shown, which includes a second polarization grating (PG2) 408 optically downstream of a light source 402, a first polarization grating (PG1) 404 serving as a polarization beam splitter, and a PVG 406, as Figure 4 shown, the use of PG2 408 rotates the polarization of the incident light such that the light output from PG2 408 has an orthogonal polarization state compared to the light incident on PG2 408.

[0023] The above-described polarization grating and PVG can be implemented as thin films. In some examples, PG1, PVG, and optional PG2 can each be implemented on their own substrates, where each substrate can have a thickness on the order of a few tens of micrometers. Thus, the total thickness of the polarization converter film stack including PG1, PVG, and PG2 can be in the range of a few tens of micrometers. Additionally, in some examples, PVG and one of PG1 or PG2 can be formed on the same substrate, which can help reduce the film thickness.

[0024] The disclosed exemplary polarization converter can offer the advantage of not having a limited aperture. As such, the disclosed polarization converter can be as wide as the light source or light source array. The disclosed exemplary polarization converter can be used in a variety of different devices, including but not limited to augmented reality and mixed reality head-mounted display systems (which may utilize liquid crystal on silicon or micro LCD displays), mobile phones and other portable devices, as well as televisions, monitors, and other larger format devices. In some examples, the polarization converter including the film stack can be placed directly on a non-polarized light source (e.g., in contact with the light source). In other examples, the polarization converter including the film stack can be placed at any other suitable location within an optical system, such as on the surface of another optical component.

[0025] Figure 5FIG. 0 shows a schematic diagram of an optical device 500 that includes an unpolarized light source 502, a thin-film polarization converter 504 located above the light source, and a polarization-sensitive optical component 512 that receives light from the polarization converter 504. The thin-film polarization converter 504 includes a first PG 506, a PVG 508, and a second PG 510. In other examples, the second PG 510 may be omitted. In some examples, various optical components may be located between the polarization-sensitive optical component 512 and the polarization converter 504, while in other examples, the polarization-sensitive optical component 512 receives the polarized output light directly from the polarization converter 504 (i.e., the light source and the polarization converter may be combined in an integrated backlight unit for display). The polarization-sensitive optical component 512 may represent any suitable optical component in an optical system. For example, the polarization-sensitive optical component 512 may be a liquid crystal panel configured to modulate the polarization angle and / or phase of light, or a birefringent beam steering device (e.g., a liquid crystal beam steering device). The polarization converters 300 and 400 are non-limiting examples of suitable structures that serve as the polarization converter 504. The optical device 500 further includes a controller 514 in communication with the polarization-sensitive optical component 512 and the unpolarized light source 502. The controller 514 may be used to form a display image (e.g., component 512 is a display panel) or direct light projection into the environment (e.g., component 512 is a beam steerer). The optical device 500 further includes an optional battery 516, such as in an example where the optical device 500 represents a mobile device that includes a polarization-based display (e.g., an LCD or LCOS display) and / or a depth sensor that utilizes a birefringent beam steerer. As described above, compared to a conventional polarizer, using the polarization converter 504 can help maintain the brightness of the light output by the light source and, as a result, can allow for lower power operation, which can help extend the amount of time that the device 500 can be used between battery charges.

[0026] Figure 6 FIG. 4 shows a flow chart depicting an example method 600 for operating an optical device. Example optical devices include, but are not limited to, display devices and depth sensors that include projectors. Method 600 includes emitting unpolarized light from a light source at 602. Any suitable unpolarized light source may be used, including, but not limited to, a VCSEL array and an LED. Method 600 further includes, at 604, passing the unpolarized light through a polarization beam splitter, thereby splitting the unpolarized light into light of a first polarization state and light of a second polarization state, where the light of the first polarization state is one of right-circularly polarized light and left-circularly polarized light, and where the second polarization state is the other of right-circularly polarized light and left-circularly polarized light.

[0027] Method 600 further includes, at 606, passing light of a first polarization state and light of a second polarization state through a PVG that is configured to transmit light of the first polarization state without changing the first polarization state of the light to a different polarization state and to convert the light of the second polarization state to the first polarization state, thereby forming polarized output light. In various examples, the PVG can be a right-handed PVG or a left-handed PVG. Additionally, in some examples, the polarization beam splitter and the polarization volume grating include layers in a film stack.

[0028] In some examples, a second polarization grating can be used optically downstream of the PVG. Thus, method 600 includes, at 608, passing the polarized output light through a second polarization grating optically downstream of the polarization volume grating to redirect the polarized output light. After forming the polarized output light from the unpolarized light, method 600 includes, at 610, providing the polarized light to a polarization-sensitive optical component. In various examples, the polarization-sensitive optical component can include a liquid crystal display panel, a birefringent beam steerer, or any other suitable polarization-sensitive component.

[0029] In some embodiments, the methods and processes described herein can be bound to a computing system of one or more computing devices. In particular, such methods and processes can be implemented as a computer application or service, an application programming interface (API), a library, and / or other computer program products.

[0030] Figure 7 A non-limiting embodiment of a computing system 700 is schematically illustrated that can implement one or more of the above methods and processes. Computing system 700 is shown in simplified form. Computing system 700 can take the form of one or more personal computers, server computers, tablet computers, home entertainment computers, network computing devices, gaming devices, mobile computing devices, mobile communication devices (e.g., smart phones), and / or other computing devices. By way of example, computing system 700 can represent controller 514.

[0031] Computing system 700 includes a logic subsystem 702 and a storage subsystem 704. Computing system 700 can optionally include a display subsystem 706, an input subsystem 708, a communication subsystem 710, and / or Figure 7 other components not shown.

[0032] The logic subsystem 702 includes one or more physical devices configured to execute instructions. For example, the logic subsystem 702 can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform tasks, implement data types, transform the state of one or more components, achieve a technical effect, or otherwise obtain a desired result.

[0033] The logic subsystem 702 may include one or more processors configured to execute software instructions. Additionally or alternatively, the logic subsystem 702 may include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. The processors of the logic subsystem 702 may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and / or distributed processing. Optionally, the various components of the logic subsystem 702 may be distributed among two or more separate devices, which may be remotely located and / or configured for coordinated processing. Aspects of the logic subsystem 702 may be virtualized and executed by remotely accessible networked computing devices configured in a cloud computing configuration.

[0034] The storage subsystem 704 includes one or more physical devices configured to store instructions executable by a logic machine, the instructions for implementing the methods and processes described herein. When implementing such methods and processes, the state of the storage subsystem 704 may be transformed, e.g., to store different data.

[0035] The storage subsystem 704 may include removable and / or built-in devices. The storage subsystem 704 may include optical memory (e.g., CD, DVD, HD-DVD, Blu-ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and / or magnetic memory (e.g., hard disk drive, floppy disk drive, tape drive, MRAM, etc.), among others. The storage subsystem 704 may include volatile, non-volatile, dynamic, static, read / write, read-only, random access, sequential access, location-addressable, file-addressable, and / or content-addressable devices.

[0036] It should be understood that the storage subsystem 704 includes one or more physical devices. However, aspects of the instructions described herein may alternatively be propagated by a communication medium (e.g., electromagnetic signals, optical signals, etc.) that a physical device does not hold for a limited duration.

[0037] Aspects of the logic subsystem 702 and the storage subsystem 704 may be integrated together into one or more hardware logic components. For example, such hardware logic components may include field-programmable gate arrays (FPGAs), program-specific application-specific integrated circuits (PASIC / ASICs), program and application-specific standard products (PSSP / ASSPs), systems-on-a-chip (SOCs), and complex programmable logic devices (CPLDs).

[0038] When included, the display subsystem 706 can be used to present a visual representation of data saved by the storage subsystem 704. The visual representation can take the form of a graphical user interface (GUI). Since the methods and processes described herein change the data held by the storage machine and thus change the state of the storage computer, the state of the display subsystem 706 can likewise be transformed to visually represent the changes in the underlying data. The display subsystem 706 can include one or more display devices utilizing almost any type of technology. Such display devices can be combined with the logic subsystem 702 and / or the storage subsystem 704 in a shared enclosure, or such display devices can be peripheral display devices.

[0039] When included, the input subsystem 708 can include one or more user input devices, such as a keyboard, mouse, touch screen, or game controller, or interface with one or more user input devices. In some embodiments, the input subsystem 708 can include or interact with selected natural user input (NUI) components. Such components can be integrated or peripheral and can process the conversion and / or processing of input actions on-board or off-board. Example NUI components can include a microphone for voice and / or speech recognition; infrared, color, stereo, and / or depth cameras for machine vision and / or gesture recognition; head trackers, eye trackers, accelerometers, and / or gyroscopes for motion detection and / or intent recognition; and electrofield sensing components for evaluating brain activity.

[0040] When included, the communication subsystem 710 can be configured to communicatively couple the computing system 700 with one or more other computing devices. The communication subsystem 710 can include wired and / or wireless communication devices compatible with one or more different communication protocols. As a non-limiting example, the communication subsystem can be configured to communicate via a wireless telephone network or a wired or wireless local area network or wide area network. In some embodiments, the communication subsystem can allow the computing system 700 to send and / or receive messages to / from other devices via a network such as the Internet.

[0041] Another example provides an optical device, including a light source configured to output unpolarized light; a polarization beam splitter configured to split the unpolarized light into light of a first polarization state and light of a second polarization state; and a polarization volume grating configured to receive the light of the first polarization state and the light of the second polarization state, and transmit the light of the first polarization state without changing the light of the first polarization state into a different polarization state, and convert the light of the second polarization state into the first polarization state, thereby forming polarized output light. The light of the first polarization state can additionally or alternatively be one of right-handed circularly polarized light and left-handed circularly polarized light, and the second polarization state can additionally or alternatively be the other of left-handed circularly polarized light and right-handed circularly polarized light. The polarization beam splitter and the polarization volume grating can additionally or alternatively include layers in a film stack. In the case where the polarization beam splitter is a first polarization grating, the optical device can additionally or alternatively include a second polarization grating optically downstream of the polarization volume grating to redirect the polarized output light. In the case where the optical device is a display device, the optical device can additionally or alternatively include a liquid crystal display panel. The optical device can additionally or alternatively include a projector. The optical device can additionally or alternatively include a battery. The light source can additionally or alternatively include one or more of a vertical cavity surface emitting laser and a light emitting diode.

[0042] Another embodiment provides a method implemented on an optical device, the method including emitting unpolarized light from a light source, passing the unpolarized light through a polarization beam splitter to split the unpolarized light into light of a first polarization state and light of a second polarization state, and passing the light of the first polarization state and the light of the second polarization state through a polarization volume grating configured to transmit the light of the first polarization state without changing the light of the first polarization state into a different polarization state, and convert the light of the second polarization state into the first polarization state, thereby forming polarized output light. The light of the first polarization state can additionally or alternatively be one of right-handed circularly polarized light and left-handed circularly polarized light, and the second polarization state can additionally or alternatively be the other of left-handed circularly polarized light and right-handed circularly polarized light. The polarization beam splitter and the polarization volume grating can additionally or alternatively include layers in a film stack. In the case where the polarization beam splitter is a first polarization grating, the method can additionally or alternatively include passing the polarized output light through a second polarization grating optically downstream of the polarization volume grating to redirect the polarized output light. The method can additionally or alternatively include forming an image via a liquid crystal display panel using the polarized output light. The method can additionally or alternatively include using the polarized output light in a projector. Emitting unpolarized light can additionally or alternatively include emitting unpolarized light via a vertical cavity surface emitting laser and emitting unpolarized light via a light emitting diode, one or more of which.

[0043] Another example provides an optical device including a light source configured to output unpolarized light. A first polarization grating includes a polarization beam splitter configured to split the unpolarized light into light of a first polarization state and light of a second polarization state. A volume polarization grating is configured to receive the light of the first polarization state and the light of the second polarization state, transmit the light of the first polarization state without changing the light of the first polarization state to a different polarization state, and convert the light of the second polarization state to the first polarization state, thereby forming polarized output light, and a second polarization grating optically downstream of the volume polarization grating to redirect the polarized output light. The light of the first polarization state can additionally or alternatively be one of right circularly polarized light and left circularly polarized light, and the second polarization state can additionally or alternatively be the other of left circularly polarized light and right circularly polarized light. The polarization beam splitter and the volume polarization grating can additionally or alternatively include layers in a film stack. In the case where the optical device is a display device, the optical device can additionally or alternatively include a liquid crystal display panel. The light source can additionally or alternatively include one or more of a vertical cavity surface emitting laser and a light emitting diode.

[0044] It should be understood that the configurations and / or methods described herein are exemplary in nature and these specific embodiments or examples should not be considered limiting as many variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, the various acts shown and / or described may be performed in the order shown and / or described, in other orders, in parallel, or omitted. Likewise, the order of the above-described processing may be changed.

[0045] The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems, and configurations and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

1. An optical device, comprising: a light source configured to output unpolarized light; a polarization beam splitter configured to split the unpolarized light into light of a first polarization state and light of a second polarization state; and a volume holographic grating configured to receive the light of the first polarization state and the light of the second polarization state, transmit the light of the first polarization state without changing the light of the first polarization state to a different polarization state and without changing the direction of the light of the first polarization state by diffraction, and convert the light of the second polarization state to the first polarization state and change the direction of the light of the second polarization state by diffraction, thereby forming polarized output light.

2. The optical device according to claim 1, wherein the light of the first polarization state is one of right-handed circularly polarized light and left-handed circularly polarized light, and wherein the second polarization state is the other of right-handed circularly polarized light and left-handed circularly polarized light.

3. The optical device according to claim 1, wherein the polarization beam splitter and the volume holographic grating comprise layers in a film stack.

4. The optical device according to claim 1, wherein the polarization beam splitter is a first polarization grating, and further comprises a second polarization grating optically downstream of the volume holographic grating to redirect the polarized output light.

5. The optical device according to claim 1, wherein the optical device is a display device, and further comprises a liquid crystal display panel.

6. The optical device according to claim 1, wherein the optical device is a projector.

7. The optical device according to claim 1, further comprising a battery.

8. The optical device according to claim 1, wherein the light source comprises: One or more of a vertical cavity surface emitting laser and a light emitting diode.

9. A method implemented on an optical device, comprising: emitting unpolarized light from a light source; passing the unpolarized light through a polarization beam splitter, thereby splitting the unpolarized light into light of a first polarization state and light of a second polarization state; and passing the light of the first polarization state and the light of the second polarization state through a volume holographic grating configured to transmit the light of the first polarization state without changing the light of the first polarization state to a different polarization state and without changing the direction of the light of the first polarization state by diffraction, and convert the light of the second polarization state to the first polarization state and change the direction of the light of the second polarization state by diffraction, thereby forming polarized output light.

10. The method according to claim 9, wherein the light of the first polarization state is one of right-handed circularly polarized light and left-handed circularly polarized light, and wherein the second polarization state is the other of right-handed circularly polarized light and left-handed circularly polarized light.

11. The method according to claim 9, wherein the polarization beam splitter and the volume holographic grating comprise layers in a film stack.

12. The method according to claim 9, wherein the polarization beam splitter is a first polarization grating, and further comprises passing the polarized output light through a second polarization grating optically downstream of the volume holographic grating to redirect the polarized output light.

13. The method according to claim 9 further comprises: Use the polarized output light to form an image via a liquid crystal display panel.

14. The method according to claim 9 further comprises: Use the polarized output light in a projector.

15. The method according to claim 9, wherein emitting non-polarized light comprises: Emit one or more of the unpolarized light via a vertical cavity surface emitting laser and the unpolarized light via a light emitting diode.

16. An optical device, comprising: A light source configured to output unpolarized light; A first polarization grating, the first polarization grating including a polarization beam splitter configured to split the unpolarized light into light of a first polarization state and light of a second polarization state; A polarization volume grating configured to receive the light of the first polarization state and the light of the second polarization state, Transmit the light of the first polarization state without changing the first polarization state of the light to a different polarization state and without changing the direction of the light of the first polarization state by diffraction, and convert the light of the second polarization state to the first polarization state and change the direction of the light of the second polarization state by diffraction, thereby forming a polarized output light; And A second polarization grating optically downstream of the polarization volume grating to redirect the polarized output light.

17. The optical device according to claim 16, wherein the light of the first polarization state is one of right-handed circularly polarized light and left-handed circularly polarized light, and wherein the second polarization state is the other of right-handed circularly polarized light and left-handed circularly polarized light.

18. The optical device according to claim 16, wherein the polarization beam splitter and the polarization volume grating include layers in a film stack.

19. The optical device according to claim 16, wherein the optical device is a display device and further includes a liquid crystal display panel.

20. The optical device according to claim 16, wherein the light source comprises: One or more of a vertical cavity surface emitting laser and a light emitting diode.

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