Optical system for near-eye display

Embodiments are disclosed herein that relate to compact optical systems for incorporation into near-eye display devices. For example, one disclosed embodiment provides a near-eye display system may comprising a light source, a first polarizing beam splitting surface configured to receive light from the light source, a mirror configured to reflect light passed by the first polarizing beam splitting surface, and a quarter wave plate positioned between the first polarizing beam splitting surface and the mirror. The near-eye display system may further include a second polarizing beam splitting surface positioned at an angle relative to the first polarizing beam splitting surface and a microdisplay configured to produce an image via light received from the second polarizing beam splitting surface.

BACKGROUND

A near-eye display device, such as a head-mounted display, may include various optical components arranged within the device, such as light sources, image producing elements, lens systems, and/or other optical elements. Such optical components may occupy a considerable amount of space, which may result in a near-eye display having a bulky design. As some near-eye displays may be configured to be worn by users, a bulky design may cause a near-eye display to be uncomfortable, unattractive from a design standpoint, and/or otherwise unappealing to end users.

SUMMARY

Embodiments are disclosed herein that relate to compact optical systems for incorporation into near-eye display devices. For example, one disclosed embodiment provides a near-eye display system comprising a light source, a first polarizing beam splitting surface configured to receive light from the light source, a mirror configured to reflect light passed by the first polarizing beam splitting surface, and a quarter wave plate positioned between the first polarizing beam splitting surface and the mirror. The near-eye display system further includes a second polarizing beam splitting surface positioned at an angle relative to the first polarizing beam splitting surface and a microdisplay configured to receive light reflected by the second polarizing beam-splitting surface and produce an image.

DETAILED DESCRIPTION

Embodiments are disclosed herein that relate to compact optical systems for use in near-eye display systems. Briefly, the disclosed embodiments comprise a compact folded optical path that utilizes polarized light and polarization-sensitive optical components to direct light through the optical path. The disclosed embodiments permit an illumination system to be arranged at an angle to other components of the optical system, and therefore may permit the optical system to be incorporated into a portion of a head-mounted display device that follows a curvature of a user's head. As such, the optical system may facilitate the design of a compact and low-profile near-eye display device.

FIG. 1shows a non-limiting example of a display device102in the form of a head-mounted display device including a display104. The display104may comprise any suitable display system, including but not limited to a waveguide display system. The display104may be at least partially transparent, thus allowing light from a background scene to pass through the see-through display to the eyes of a user. This may allow the display device102to be utilized to visually augment an appearance of the background scene by displaying virtual objects viewable along with real objects in the background scene.

The display device102may include various input and output devices. For example, the display device102may comprise an audio output, such as one or more speakers, in addition to the display104. Likewise, the display device102may comprise various input sensors, such as a microphone, one or more forward-facing (e.g. facing away from user) infrared and/or visible light cameras, and/or one or more rearward-facing (e.g. facing towards user) infrared and/or visible light cameras. In some embodiments, the forward-facing camera(s) may include one or more depth cameras and associated light projectors. Likewise, in some embodiments, the rearward-facing cameras may include one or more eye-tracking cameras. Further, in some embodiments, an onboard sensor system may communicate with one or more off-board sensors that send sensor data to the onboard sensor system via a wireless and/or wired communication system of the display device102.

The display device102also includes one or more features that allow the display device to be worn on the head of a user. In the illustrated example, the display device102takes the form of eyeglasses and includes a nose rest106, side pieces108, and ear rests110. In other embodiments, a head-mounted display may include a hat or helmet with a display in the form of a see-through visor, for example. While described herein in the context of a head-mounted see-through display, the concepts described herein may be applied to any other suitable display system, including displays that are not see-through.

FIG. 2shows an example embodiment of an optical system200suitable for use with display device102. As depicted, the optical system200may be positioned to a side of the display104, e.g. adjacent to side piece108of the frame. The optical system200may include an illumination system202for producing light to illuminate a microdisplay204. The illumination system202may be mounted at an angle relative to a plane of other optical components of the optical system200, as described below, so that the optical system may conform generally to a curvature of a temple area of a user's head. The illumination system202may utilize any suitable light sources, including but not limited to one or more color light-emitting diodes (LEDs) one or more laser diodes, one or more white LEDs, etc.

FIG. 3shows an example of an illumination system300suitable for use as illumination system202ofFIG. 2. The illumination system300includes a first light source302a, a second light source302b, and a third light source302c. In some embodiments, the light sources302a-cmay correspond to red, green, and blue LEDs of an RGB LED assembly. In other embodiments, RGB lasers may be utilized. The use of RGB lasers may offer the potential advantage of outputting polarized light. As depicted, the second and third light sources302band302cmay be positioned at an angle to the first light source302a, and to a direction in which light exits the illumination system300. Light emitted from each of light source may pass through a collector and focusing lens, shown respectively at304a-cand306a-cfor light sources302a-c. The collectors and focusing lenses may be configured to direct light emitted from the light sources through dichroic beam splitters308to focus on a microlens array. The dichroic beam splitters308may be configured to pass light from the first light source302aand reflect light from the second and third light sources302band302cso that light from each of the light sources exit the dichroic beam splitters308in a same direction. It will be noted that illumination system310may be rotated about the optical axis of light that exits the illumination system relative to downstream optics without affecting light passing through the downstream optics. This may allow illumination system310to be positioned relative to other optics to generally conform to a contour of a user's temple.

Referring again toFIG. 2, light exiting the illumination system may pass through other optical elements to a polarizing beam splitter206.FIG. 2depicts an example location of the polarizing beam splitter206in optical system200, andFIG. 4shows a schematic depiction of a path of light through example components in the form of a microlens array400and a negative element402before reaching the polarizing beam splitter206. In some embodiments, one or more of the lens elements (e.g. the negative element402) near the light source may be aspheric. Further, the microlens array400may be configured to match etendue of a microdisplay of the system. WhileFIG. 4shows a single light source302for clarity, it will be understood that a plurality of light sources may be combined via dichroic beam splitters308, as described above with reference toFIG. 3.

The polarizing beam splitter206may include a first polarizing beam splitting surface404and a second polarizing beam splitting surface406for directing light in a folded optical path toward the microdisplay204. The first polarizing beam splitting surface404may be configured to polarize light received from the light sources302a-cand pass the polarized light through a quarter wave plate408to a mirror410. The mirror410is configured to reflect the light back through the quarter wave plate408. After passing through the quarter wave plate408two times, the polarization state of the light is rotated by 90 degrees compared to its state before its initial pass through the first quarter wave plate408. Thus, light from the mirror410is then reflected by the first polarizing beam splitting surface404toward a total internal reflection (TIR) surface412of the polarizing beam splitter206, where the light is reflected by total internal reflection toward the second polarizing beam splitting surface406. The second polarizing beam splitting surface406then reflects the light toward TIR surface412at a sufficient angle to exit the TIR surface without total internal reflection. Light exiting the polarizing beam splitter206may then pass through additional elements, such as a doublet lens414, and a polarization-adjusting element416, such as another quarter wave plate or a compensator, to the microdisplay204, as described in more detail below. The polarizing beam splitter206may be immersed in a suitable medium such that light reflected by the first and second polarizing beams splitting surfaces and the total internal reflection surface is maintained within the medium.

The first and second polarizing beam splitting surfaces may be positioned at any suitable angle relative to each other. Likewise, the second polarizing beam splitting surface may also be positioned at any suitable angle relative to the microdisplay204. For example, in some embodiments, the second polarizing beam splitting surface may be oriented at an angle of 20 to 50 degrees with respect to a longitudinal axis208of the microdisplay204. In a more specific example, the second polarizing beam splitting surface may be oriented at an angle of 30 degrees relative to a longitudinal axis208of the microdisplay204.

Any suitable type of microdisplay device may be used as microdisplay204. For example, in some embodiments, the microdisplay204may comprise a liquid crystal on silicon (LCoS) display. In such embodiments, light incident on the microdisplay204is spatially modulated to produce an image and reflected back toward the second polarizing beam splitting surface406. The polarization state of light reflected from the LCoS is rotated compared to light incident on the LCoS. However, due to such factors as manufacturing tolerances, the LCoS may not rotate the polarization state of the reflected light a full ninety degrees. Therefore, in such embodiments, the polarization adjuster416may comprise a compensator to complete the rotation of the light from the LCoS prior to passing the light through the second polarizing beam splitting surface. Referring again toFIG. 2, this light may then pass through projection optics210, and be directed to display104(e.g. via a waveguide or other suitable optics).

In other embodiments, the microdisplay204may comprise another type of reflective microdisplay, such as a digital light processing (DLP) display. In such embodiments, the polarization adjuster416may comprise a quarter wave plate to rotate the light for transmission through the second polarizing beam splitting surface. In yet other embodiments, the microdisplay may comprise a transmissive microdisplay, such as a transmissive liquid crystal microdisplay. In such embodiments, the polarization adjuster416may be omitted.

FIG. 5shows a flow diagram depicting an example method500of directing light through a near-eye display system in accordance with an embodiment of the present disclosure. As indicated at502, method500includes outputting light from a light source. Light from the light source may be directed through various components, such as a microlens array, as indicated at504, and then through a first polarizing beam splitting surface, as indicated at506, which linearly polarizes the light. It will be understood that, in other embodiments, another polarizer located optically upstream of the polarizing beam splitter may be used to polarize the light.

Method500further includes directing the portion of the light through a first quarter wave plate toward a mirror, as indicated at508. The mirror reflects the portion of the light back through the first quarter wave plate, such that the polarization state is rotated a total of ninety degrees from the two passes through the quarter wave plate, and toward the first polarizing beam splitting surface, as indicated at510. Next, method500includes reflecting the portion of the light via the first polarizing beam splitting surface toward a second polarizing beam splitting surface. In some embodiments, light reflected by the first polarizing beam splitting surface may reflect from a TIR surface toward the second polarizing beam surface, as described above with regard toFIG. 4.

Continuing, method500next includes, at514, reflecting the portion of the light from the second polarizing beam splitting surface through the TIR surface, through a polarization adjuster in some embodiments, and toward a microdisplay for the production of an image, as indicated at516. In some embodiments, a reflective microdisplay, such as an LCOS or DLP (digital light processing) display, may be used such that the microdisplay reflects light back toward the second polarizing beam splitting surface, as indicated at518. In other embodiments, a transmissive microdisplay may be used. In embodiments that utilize a LCoS display, the polarization adjuster may comprise a compensator, while in embodiments that utilize another type of reflective microdisplay (e.g. a DLP display), the polarization adjuster may comprise a second quarter wave plate.

Thus, the embodiments disclosed herein may provide for a compact optical system configured to conform to a contour of a user's head, and thus that may allow the construction of a more compact and attractive near-eye display system. In some embodiments, the methods and processes described herein may be tied to a computing system of one or more computing devices. In particular, such methods and processes may be implemented as a computer-application program or service, an application-programming interface (API), a library, and/or other computer-program product.

FIG. 6schematically shows a non-limiting embodiment of a computing system600that can enact one or more of the methods and processes described above. The computing system600is shown in simplified form. The computing system600may take the form of one or more near-eye display devices, head-mounted display devices, mobile communication devices (e.g., smart phone), mobile computing devices, tablet computers, server computers, gaming consoles, home-entertainment computers, network computing devices, personal computers, and/or other computing devices.

The computing system600includes a logic machine602and a storage machine604. The computing system600further may include a display subsystem606, an input subsystem608, a communication subsystem610, and/or other components not shown inFIG. 6.

The storage machine604includes one or more physical devices configured to store and hold instructions (e.g., computer- and/or machine-readable instructions) executable by the logic machine to implement the methods and processes described herein. For example, the logic machine602may be in operative communication with a sensor interface (e.g. an interface of the input sensors of display device102ofFIG. 1), and the storage machine604. When such methods and processes are implemented, the state of the storage machine604may be transformed—e.g., to hold different data.

It will be appreciated that the storage machine604includes one or more physical devices. However, aspects of the instructions described herein alternatively may be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.).

The display subsystem606may be used to present a visual representation of data held by the storage machine604. For example, the display subsystem606may include one or more elements of the display104and/or the optical system200ofFIG. 1. This visual representation may take the form of a graphical user interface (GUI), potentially presented as an augmented reality image in which real and virtual objects are both viewable through a see-through display. As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem606may likewise be transformed to visually represent changes in the underlying data. The display subsystem606may include one or more display devices utilizing virtually any type of technology. Such display devices may be combined with the logic machine602and/or the storage machine604in a shared enclosure, or such display devices may be peripheral display devices.

When included, the communication subsystem610may be configured to communicatively couple the computing system600with one or more other computing devices. The communication subsystem610may include wired and/or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some embodiments, the communication subsystem may allow the computing system600to send and/or receive messages to and/or from other devices via a network such as the Internet.