Patent Application
20240288684
The present disclosure is related to display devices of virtual reality (VR) and/or augmented reality (AR) headsets. More specifically, the present disclosure is directed to efficient and compact devices that expand an illuminating beam in two dimensions for illuminating a pixelated display device in a VR/AR headset.
Two-dimensional display devices, for example, liquid crystal displays (LCDs) are illuminated in the backend by collimated light sources such as white light-emitting diode (LED) or a coherent source such as a red-green-blue (RGB) laser that desirably illuminate the entire area of the backend of the display device. These backlights can impose design constraints, for instance, restrictions related to the display size. Additionally, multilayered display devices for VR/AR applications typically have low transmission efficiency, which exacerbates the power usage of the display device, in detriment of battery lifetime, which is critical for headset applications.
An aspect of the subject technology is directed to an apparatus that includes a light source to generate a light beam, a first grating illuminated by the light beam, and a second grating optically coupled to the first grating. The first grating performs a first diffraction to expand the light beam in a first dimension to form a first beam. The second grating performs a second diffraction to expand the first beam in a second dimension to provide a backlight for a display device.
Another aspect of the disclosure is related to a beam expander system including a laser to generate a first beam, a first Bragg grating illuminated by the first beam, a polarizing component and a second Bragg grating optically coupled to the first Bragg grating. The first Bragg grating creates a first diffracted beam in a first dimension, and the polarizing component changes a polarization state of the first diffracted beam. The second Bragg grating creates a second diffracted beam to expand the first polarized diffracted beam in a second dimension to provide a backlight for a display device.
Yet another aspect of the disclosure is related to a beam expander system that includes a first volume Bragg grating (VBG) illuminated by a first collimated beam to form a first diffracted beam along a length of the first VBG and a polarizing component configured to switch polarization state of the first diffracted beam. The beam expander system further includes a second VBG to expand the first polarized diffracted beam to form a backlight for a display device.
To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.
In the figures, elements having the same or similar reference numerals are associated with the same or similar attributes, unless explicitly stated otherwise.
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art, that embodiments of the present disclosure may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure. Embodiments as disclosed herein will be described with the description of the attached figures.
Example architectures of the subject technology is directed to an apparatus that includes a light source to generate a light beam and a first grating illuminated by the light beam, and a second grating optically coupled to the first grating. The first grating is used to perform a first diffraction that can expand the light beam in a first dimension and form a first beam. The second grating is used to perform a second diffraction to expand the first beam in a second dimension and provide a backlight for a display device (e.g., an LCD or LCOS).
In some implementations, the first grating is illuminated by a collimated light beam of a laser source.
In one or more implementations, the first diffraction is a first single diffraction that creates a first single-diffracted beam that can expand the light beam in the first dimension of the first grating coupled to the second grating.
In some implementations, the second diffraction is a second single diffraction that creates a second single-diffracted beam that expands the expanded first beam in the second dimension to form a two-dimensional beam perpendicular to a plane of the second grating.
In one or more implementations, the first grating is a first Bragg grating such as a first VBG, and the second grating is a second Bragg grating such as a second VBG.
In some implementations, the first VBG and the second VBG are single-diffraction VBGs.
In one or more implementations, at least one of the first VBG and the second VBG is a multiplexed (MUX) VBG including multiple gratings with different pitches used to generate a MUX diffracted beam to increase a diffracted angle range.
In one or more implementations, the display device comprises an LCD or an LCOS display device.
In some implementations, the apparatus of the subject technology further includes a polarizing component between the first grating and the second grating.
In one or more implementations, the polarizing component comprises a half-wave plate used to change a polarization state of the first beam.
In some implementations, the apparatus of the subject technology further includes a reflector plate that is used to steer the light beam at various angles to increase a pupil size of the backlight.
In one or more implementations, the light source is a grid of lasers, and each laser of the grid is selectively controllable to be switched on or off to form a zonal beam pattern that can convert the backlight to a zonal backlight with a zonal pattern.
The display device of the subject technology can advantageously be used in various applications including AR and VR devices to make these devices more compact. Further, the application of the subject technology can improve image uniformity and diffraction efficiency and mitigate some artifact issues, for example, due to particles in the rays of the illumination beam and scratches in optics. Some implementations of the subject technology can allow zonal illumination, which results in power saving and improved contrast, as further described herein.
Now turning to the description of figures,
The compact beam expander system 100B includes a light source 110 (e.g., an RGB laser), a beam shaper 112, a VBG beam expander 114, a phase mask 116, and a display device 118. The beam shaper 112 can be a collimating element that receives, in a first surface, a collimated gaussian beam, for example, as provided by a graded index (GRIN) lens placed in front of an LED or a laser diode. The output surface of the collimating element is shaped such as to provide a collimated beam with a uniform intensity profile over a cross-section (e.g., a top-hat profile). Such a collimated beam can produce a uniform intensity in the display of the VR/AR headset, as desirable.
The phase mask 116 is a phase-shift mask that is an optical element that can encode the entire spectral response of the VBG beam expander 114 including the Bragg wavelength and the type of spectral response. The display device 118 can be an LCD display or an LCD-thin film transistor (TFT) display. The TFTs are active elements (e.g., transistors) made of a semiconductor (e.g., silicon) that act as switches for each pixel of the LCD display, turning them on or off. The addition of TFT in the LCD displays has vastly improved the use of LCDs in various display applications.
This overall throughput is smaller than the throughput of about 95% of the compact beam expander system 100B of the subject technology. Furthermore, the compact beam expander system 100B, other than being a monolithic structure that is more compact and enabling a higher throughput than the existing LCD structure 100C, has other advantageous features. For example, the compact beam expander system of the subject technology can mitigate fringe speckles, improve angular spread of a compact LCOS solution and allow for a zonal illumination with a compact VBG illumination, resulting in power saving.
The phase plate structure 100D shows a more detailed structure of the phase plate 122 of the LCD structure 100C and includes a waveguide 140, a microlens array 142 and an LC pane with TFT 144.
In some implementations, the phase mask 208 can be a microlens array (MLA) that can encode the spectral response of the beam expander 206, as described above. In one or more implementations, the display panel 210 can be made of LCD or TFT LCD, as described above.
The display 200B is formed of a number of pixels 212, a representation of which pixel 214 shows a shaded region that is used by an electrode and conductors of a circuit on the LCD pixel. This would limit the LCD fill factor. In addition, the LCDs generally have larger areas compared to LCOS display devices.
The input collimated beam is diffracted off of the first VBG 410 with maximum efficiency along the Y-direction because the Z-polarization is aligned along the grooves of first VBG 410 (S-polarization). After passing through the waveplate 414, the diffracted beam switches to X-polarization, aligned along the grooves of the second VBG 412 (S-polarization). The light is then diffracted off of the second VBG 412 with a high diffraction efficiency (e.g., >95%) along the Z direction. Accordingly, the VBG illuminator 400, by including the waveplate 414, exploits the maximum diffraction efficiency of the first VBG 410 and the second VBG 412.
It should be noted that a VBG behave as a series of reflectors. When constructive interference occurs at Bragg condition, it result in high diffraction efficiency. This diffraction efficiency is a function of light polarization. Similar to a general reflector, S-polarized reflection diffraction efficiency is higher than P-polarization. Especially at Brewster angle, S-reflection diffraction efficiency can reach to about 100% while P-reflection diffraction may be about 0%. The dual diffraction in a compact illuminator occurs in an orthogonal plane, and therefore the optimal polarization diffracted from the first diffraction is orthogonal to the polarization optimal for the second diffraction. To link the two diffractions with optimal polarization, the waveplate 414 is in the light path between the two diffractions.
The bonding between the substrates of the first VBG 610 and the second VBG 620 is optional. This bonding at the half-wave film 640 can reduce the film/air and substrate/air reflection losses. The bonding of the first VBG 610 and the second VBG 620 together can be more manufacture-friendly in terms of alignment for the overall system. As seen from
The cross-sectional view 600B of the half-wave film shown in
VBGs typically have higher diffraction efficiency on S-polarized (perpendicular to the plane) light. To make both VBGs (first VBG 710 and the second VBG 720) have high diffraction efficiency, a polarization manipulation component such as a polarizing component 730 is placed in between the VBGs to rotate the light polarization to be S-polarized for the plane of the second VBG 720.
The backlight system 900A of the subject technology is an improved version of the backlight system 800A of
The compact beam expander 1000A with MUX VBG is another implementation for achieving the desirable angular spread for the input pupil, as performed by the beam scanner 930 of
The compact beam expander 1100A has an additional advantageous feature beyond saving power in that it can improve the image contrast as well, because only the zones of interest receive light.
The compact beam expanders of the subject technology, including the compact beam expander 1100A, can be used in various optical devices such as AR/VR headsets.
As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (e.g., each item). The phrase “at least one of” does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Phrases such as an aspect, the aspect, another aspect, some aspects, one or more aspects, an implementation, the implementation, another implementation, some implementations, one or more implementations, an embodiment, the embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, the configuration, another configuration, some configurations, one or more configurations, the subject technology, the disclosure, the present disclosure, other variations thereof and alike are for convenience and do not imply that a disclosure relating to such phrase(s) is essential to the subject technology or that such disclosure applies to all configurations of the subject technology. A disclosure relating to such phrase(s) may apply to all configurations, or one or more configurations. A disclosure relating to such phrase(s) may provide one or more examples. A phrase such as an aspect or some aspects may refer to one or more aspects and vice versa, and this applies similarly to other foregoing phrases.
A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” Pronouns in the masculine (e.g., his) include the feminine and neuter gender (e.g., her and its) and vice versa. The term “some” refers to one or more. Underlined and/or italicized headings and subheadings are used for convenience only, do not limit the subject technology, and are not referred to in connection with the interpretation of the description of the subject technology. Relational terms such as first and second and the like may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly recited in the above description. No clause element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method clause, the element is recited using the phrase “step for.”
While this specification contains many specifics, these should not be construed as limitations on the scope of what may be described, but rather as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially described as such, one or more features from a described combination can in some cases be excised from the combination, and the described combination may be directed to a sub-combination or variation of a sub-combination.
The subject matter of this specification has been described in terms of particular aspects, but other aspects can be implemented and are within the scope of the following clauses. For example, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. The actions recited in the clauses can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the aspects described above should not be understood as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.
The title, background, brief description of the drawings, abstract, and drawings are hereby incorporated into the disclosure and are provided as illustrative examples of the disclosure, not as restrictive descriptions. It is submitted with the understanding that they will not be used to limit the scope or meaning of the clauses. In addition, in the detailed description, it can be seen that the description provides illustrative examples, and the various features are grouped together in various implementations for the purpose of streamlining the disclosure. The method of disclosure is not to be interpreted as reflecting an intention that the described subject matter requires more features than are expressly recited in each clause. Rather, as the clauses reflect, inventive subject matter lies in less than all features of a single disclosed configuration or operation. The clauses are hereby incorporated into the detailed description, with each clause standing on its own as a separately described subject matter.
Aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The described techniques may be implemented to support a range of benefits and significant advantages of the disclosed eye tracking system. It should be noted that the subject technology enables fabrication of a depth-sensing apparatus that is a fully solid-state device with small size, low power, and low cost.
A significant aspect of the disclosed technology is that it provides a solid state (e.g., silicon) photonic interference system that is capable of depth sensing of the corneal shape to determine a gaze direction.
As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item).
To the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim.
A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description.
While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
The present disclosure is related and claims priority under 35 USC § 119(e) to U.S. Provisional Application No. 63/448,475, entitled “EFFICIENT AND COMPACT BEAM EXPANDER FOR VR/AR HEADSETS,” filed on Feb. 27, 2023, the contents of which are herein incorporated by reference, in their entirety, for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63448475 | Feb 2023 | US |
