Virtual and augmented reality system and method for speckle reduction
阅读说明:本技术 减弱散斑的虚拟和增强现实系统及方法 (Virtual and augmented reality system and method for speckle reduction ) 是由 P·圣西莱尔 于 2018-07-05 设计创作,主要内容包括:一种成像系统包括漫射元件,该漫射元件被配置为将光束中的部分耦合回到激光二极管中。该系统包括二极管激光器,该二极管激光器由漫射器和调制驱动电流的组合驱动进入混沌状态,以使其发射横跨具有3至10纳米宽的包络线的频谱的光。该系统进一步包括与二极管激光器相距至少0.1mm至0.5mm的漫射元件,以将光束中的部分耦合回到激光二极管中。另一个实施例涉及使用漫射元件来照亮平板显示器或空间光调制器。(An imaging system includes a diffusing element configured to couple a portion of a light beam back into a laser diode. The system includes a diode laser driven into a chaotic state by a combination of a diffuser and a modulated drive current such that it emits light across a spectrum having an envelope 3 to 10 nanometers wide. The system further comprises a diffusing element at least 0.1mm to 0.5mm from the diode laser to couple part of the light beam back into the laser diode. Another embodiment relates to the use of a diffusing element to illuminate a flat panel display or spatial light modulator.)
1. An imaging system for mitigating laser speckle, the imaging system comprising:
a diode laser for generating a light beam, wherein the light beam has a wavelength within the visible spectrum;
a modulator for varying a current for driving the diode laser; and
a diffuser for receiving the light beam, wherein the diffuser is configured to reflect a portion of the light beam back into the laser diode as a reflected light beam to generate a chaotic laser light pattern.
2. The imaging system of claim 1, wherein the modulator varies the current based on at least a second chaotic laser pattern.
3. The imaging system of claim 2, wherein the power variation of the modulator is based at least on a structure of the diffuser.
4. The imaging system of claim 1, further comprising:
a second diffuser disposed on an opposite side of the diffuser from the laser diode, wherein the second diffuser receives a second portion of the light beam.
5. The imaging system of claim 1, further comprising:
a lens disposed on an opposite side of the diffuser from the laser diode to receive another portion of the light beam propagating through the diffuser; and
a multimode optical fiber disposed on an opposite side of the lens from the diffuser to adjust a timing of the portion of the beam as it travels through the multimode optical fiber, the multimode optical fiber having a proximal end and a distal end, the distal end receiving the portion of the beam after the portion of the beam travels through the lens, the distal end corresponding to a light source.
6. The imaging system of claim 1, further comprising:
a projection light source;
a beam splitter disposed on an opposite side of the diffuser from the laser diode to receive light from the projection light source and the diffuser; and
a micro-display for receiving light from the beam splitter.
7. The imaging system of claim 6, wherein the micro-display comprises at least one of liquid crystal on silicon or a digital light processor.
8. The imaging system of claim 1, further comprising a homogenizer to smooth irregularities in the beam to produce a uniform pattern.
9. A near-eye display system comprising:
a laser diode;
a modulator coupled to the laser diode;
a diffuser optically coupled to the laser diode; and
a 2D spatial light modulator optically coupled to the diffuser.
10. The near-eye display system of claim 9, wherein the 2D spatial light modulator comprises a liquid crystal on silicon 2D spatial light modulator.
11. The near-eye display system of claim 9, further comprising a waveguide eyepiece optically coupled to the 2D spatial light modulator.
12. The near-eye display system of claim 11, further comprising a projection lens disposed between a microdisplay and the waveguide eyepiece.
13. The near-eye display system of claim 12, wherein the waveguide eyepiece comprises an incoupling grating and the projection lens is positioned to couple light into the incoupling grating.
14. The near-eye display system of claim 12, further comprising a polarizing beam splitter disposed between the projection lens and the 2D spatial light modulator.
15. The near-eye display system of claim 14, further comprising an illumination-side collimating lens positioned between the diffuser and the polarizing beam splitter.
16. The near-eye display system of claim 11, wherein the waveguide eyepiece comprises an incoupling grating and an exit pupil expansion grating, the exit pupil expansion grating being coupled to the incoupling grating by the waveguide eyepiece.
Background
Modern computing and display technology has facilitated the development of systems for so-called "mixed reality" experiences, including "virtual reality" or "augmented reality", in which digitally reproduced images, or portions thereof, are presented to a user in such a way that they appear to be, or can be perceived as, real. Virtual reality or "VR" scenes typically involve the presentation of digital or virtual image information, but are not visible to the actual real-world visual background, so that the user perceives only the digital or virtual image, and not any light/image directly from the real world. An augmented reality or "AR" scene will involve the presentation of digital or virtual image information as an enhancement to the perception of the real world around the user (i.e., visible to other real world visual inputs) such that the user perceives the digital or virtual content as an object in the real world environment (i.e., a virtual object). Thus, AR scenes involve the presentation of digital or virtual image information along with a view to other actual real-world visual input. The human visual perception system is very complex. Therefore, it is challenging to generate VR or AR techniques that facilitate comfortable, natural-feeling, and rich presentation of virtual image elements in addition to other virtual or real-world image elements.
A speckle (speckle) pattern is an intensity pattern produced by the mutual interference of wavefronts emanating from a coherent source. Speckle refers to a random pattern of particles (granular pattern) that can be observed when a highly coherent light beam (e.g., from a laser) is diffusely reflected at a rough surface, such as paper, white paint, a display screen, or a metal surface. This phenomenon is caused by interference of different reflected portions of the incident beam with random relative optical phases. Laser speckle structures are created whenever a laser beam propagates through a diffuser or reflects from a diffusely reflective surface. Speckle structures depend on the coherent nature of the laser radiation and arise due to interference of a large number of scattered waves of random initial phase.
Speckle patterns can severely degrade the image quality of projection displays that include laser sources. Since the laser is a coherent narrow-band light source, the laser generates an interference pattern. As such, the quality of images generated using projection displays with laser sources may be reduced because the laser light tends to interfere at various points. In addition, interference generated by diffraction at a large number of scattering particles (e.g., dust) on the projection optics will also degrade image quality. The accumulation of the degradation in quality of images from various sources causes the final image to appear grainy and distorted.
Therefore, there is a need to mitigate laser speckle in virtual reality or augmented reality systems.
Disclosure of Invention
Embodiments of the present disclosure provide a system for mitigating laser speckle by placing a diffuser in front of a laser diode to generate a chaotic laser pattern in the laser diode. The diffuser is a randomly or pseudo-randomly patterned surface that causes multiple beam rays to bounce from different locations on the diffusing surface and scatter back into the laser diode, thereby creating a complex superposition of modes in the laser gain medium, thus inducing mode hops in the laser resonator. These mode hops reduce coherence because each of them is associated with a slightly different transmit frequency. The laser is also driven into chaotic operation by a combination of received optical feedback and current modulation. In other embodiments, the diffuser and the change in power from the laser cooperate to push the laser into the chaos.
In one embodiment, an imaging system for mitigating laser speckle includes a diode laser for generating a light beam, wherein the light beam has a wavelength within the visible spectrum. The system further comprises a modulator for varying the current for driving the diode laser. The system further includes a diffuser for receiving the light beam, wherein the diffuser is configured to reflect a portion of the light beam back into the laser diode as a reflected light beam to generate a chaotic laser light pattern.
In one or more embodiments, the modulator varies the current based on at least the second chaotic laser pattern. The power variation of the modulator may be based at least on the structure of the diffuser. The system can also include a second diffuser disposed on an opposite side of the diffuser from the laser diode, wherein the second diffuser receives a second portion of the light beam. The system may further include a lens disposed on an opposite side of the diffuser from the laser diode to receive another portion of the light beam propagating through the diffuser. The system may further include a multimode optical fiber disposed on an opposite side of the lens from the diffuser to adjust a timing of a portion of the beam as the portion travels through the multimode optical fiber, the multimode optical fiber having a proximal end and a distal end, the distal end receiving the portion of the beam after the portion of the beam travels through the lens, the distal end corresponding to the light source.
In one or more embodiments, the system further comprises: a projection light source; a beam splitter disposed on an opposite side of the diffuser from the laser diode to receive light from the projection light source and the diffuser; and a microdisplay for receiving light from the beam splitter. The microdisplay may include at least one of liquid crystal on silicon or a digital light processor. The system may also include a homogenizer (homogenizer) for smoothing irregularities in the beam to produce a uniform pattern.
In another embodiment, a near-eye display system includes a laser diode. The system also includes a modulator coupled to the laser diode. The system further includes a diffuser optically coupled to the laser diode. Further, the system includes a 2D spatial light modulator optically coupled to the diffuser.
In one or more embodiments, the 2D spatial light modulator comprises a liquid crystal on silicon 2D spatial light modulator. The system may also include a waveguide eyepiece optically coupled to the 2D spatial light modulator. The system may also include a projection lens disposed between the microdisplay and the waveguide eyepiece.
In one or more embodiments, the waveguide eyepiece includes an incoupling grating and the projection lens is positioned to couple light into the incoupling grating. The system may further comprise a polarizing beam splitter arranged between the projection lens and the 2D spatial light modulator. The system may also include an illumination side collimating lens positioned between the diffuser and the polarizing beam splitter.
16. The near-eye display system of claim 11, wherein the waveguide eyepiece comprises an incoupling grating and an exit pupil expansion grating, the exit pupil expansion grating being coupled to the incoupling grating by the waveguide eyepiece.
Further details of embodiments, objects, and advantages of the present disclosure are described below in the detailed description, drawings, and claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the scope of the disclosure.
Drawings
The drawings illustrate the design and utility of various embodiments of the present disclosure. It should be noted that the figures are not drawn to scale and that elements of similar structure or function are represented by the same reference numerals throughout the figures. In order to better appreciate how the above-recited and other advantages and objects of various embodiments of the present disclosure are obtained, a more particular description of the disclosure briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:
fig. 1A depicts a plot of amplitude versus wavelength for a laser operating in a single mode in accordance with some embodiments.
Fig. 1B depicts a graph of amplitude versus wavelength for a laser operating in chaotic mode in accordance with some embodiments.
Fig. 2A-2D schematically depict views of a wearable AR device, in accordance with various embodiments.
Fig. 3 depicts an exemplary speckle pattern in accordance with some embodiments.
Fig. 4 schematically depicts an alternative method of mitigating laser speckle, in accordance with some embodiments.
Fig. 5 schematically depicts an optical system for reducing laser speckle through a diffuser according to some embodiments.
Fig. 6 schematically depicts an optical system that attenuates laser speckle through two diffusers, according to some embodiments.
Fig. 7A-7B schematically depict optical systems for reducing laser speckle through multimode fibers, in accordance with some embodiments.
Fig. 8 schematically depicts an optical system for reducing laser speckle by using a light source, in accordance with some embodiments.
Fig. 9 schematically depicts an optical system for reducing laser speckle by a homogenizer, in accordance with some embodiments.
Detailed Description
Various embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the present disclosure so as to enable those skilled in the art to practice the disclosure. It should be noted that the following figures and examples are not meant to limit the scope of the present disclosure. Where certain elements of the present disclosure may be partially or fully implemented using known components (or methods or processes), only those portions of such known components (or methods or processes) that are necessary for an understanding of the present disclosure will be described, and detailed descriptions of other portions of such known components (or methods or processes) will be omitted so as not to obscure the present disclosure. Furthermore, various embodiments encompass current and future known equivalents to the components referred to herein by way of illustration.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
A number of embodiments are shown and described. To facilitate understanding, identical or similar structures are identified with the same reference numerals between the various figures, even though the structures may in some cases be different.
The optical system described herein may be implemented independently of an Augmented Reality (AR) system, but for illustrative purposes only, many embodiments are described below with respect to AR systems.
Overview of problems and solutions
The following disclosure describes various embodiments of systems and methods for mitigating laser speckle. According to some embodiments, speckle is mitigated by using a laser source driven into a chaotic state ("coherent collapse state"). One method of reducing laser speckle is to optimize the spectral line width. Another method of reducing laser speckle is to optimize the beam diameter. In particular, a diffusing element is used to couple a portion of the emitted light back into the laser to produce optical feedback that results in chaotic operation of the laser. Lasers operating in chaotic mode exhibit a wider spectrum than lasers operating in single mode. In certain embodiments described herein, a diffuser is used to chaotically operate a laser that would otherwise operate in a single mode. In some embodiments, the current driving the laser is additionally modulated to increase the chaotic behavior of the laser.
Illustrative optical system
Before describing the details of embodiments of the light distribution system, a brief description of an illustrative optical system will be given. Although embodiments may be used with any optical system, a specific system (e.g., an AR system) is described to illustrate the technology on which embodiments are based.
To present 3D virtual content to a user, Augmented Reality (AR) systems project images of the virtual content into the user's eyes such that they appear to originate from various depth planes spaced at various distances in front of (i.e., orthogonally away from) the user's eyes. In other words, the virtual content may not only extend in the X and Y directions (i.e., in a 2D plane orthogonal to the central visual axis of the user's eyes), but may also appear to change in depth in the Z direction so that the user may perceive the object as approaching, at an infinite distance, or at any distance in between. In other embodiments, the user may perceive multiple objects at different depth planes simultaneously. For example, the user may see that a virtual dragon appears at an extremely long distance and then runs towards the user. Alternatively, the user may see both a virtual bird at a distance of 3 meters from the user and a virtual coffee cup at one arm length (about 1 meter) from the user.
In certain embodiments, each eyepiece includes a stack of transparent waveguides. Each waveguide may be provided with an incoupling optical feature, an outcoupling feature and optionally one or more additional optical features for distributing light over the outcoupling feature. Each particular waveguide outputs light at an angle corresponding to the angle at which the light is input into that particular waveguide. The stack of waveguides may include waveguides dedicated to a particular color component (e.g., red, green, or blue) and imparting a particular convex wavefront curvature to the outgoing light. One way to impart curvature to the wavefront is to implement the outcoupling features as a transmissive diffraction grating with curved grating grooves, as taught in U.S. provisional patent application entitled "Mixed Reality Systems incorporating thin media and Related Methods," serial No. 62/384,552, filed on 9/2016. Each wavefront curvature corresponds to a particular virtual image distance. By providing multiple waveguides that impart different curvatures, multiple virtual image distances may be generated. In one example, each eyepiece may include two sets of red, blue, and green dedicated waveguides. One of the two sets may be configured to impart a first wavefront curvature and the second of the two sets may be configured to impart a second wavefront curvature.
As will be explained in further detail below, light from a single mode laser is monochromatic and coherent. When such coherent light is reflected by a diffusing surface with some optically-scaled surface features, each point on the surface becomes a virtual wave source according to Huygens (Huygens) principle, and waves from different points will constructively and destructively interfere. This results in the generation of an interference pattern, also known as a speckle pattern.
FIG. 1a is a graph showing amplitude versus wavelength for a laser having one linewidth. The spectral lines shown in fig. 1a are caused by emitting light in a narrow frequency range. Typically, a normal laser will emit a narrow spectral line (i.e., less than 1 nanometer), such as shown by the
FIG. 1b is a graph showing the amplitude versus wavelength of a chaotic laser. The laser has multiple peaks 100b instead of only a single peak (as compared to the
The use of a laser source may have several advantages. In some embodiments, the laser source may have a smaller etendue (etendue) than the other light sources. In some embodiments, it may be easier to collimate light into a tight (e.g., small) spot for scanning a display by using a laser source than by using other light sources. In some embodiments, the laser source may be more efficient than other light sources.
In some embodiments, all photons emitted by the laser source may be in phase and may be coherent with each other. These characteristics may produce, among other things, speckle. Each group of coherent photons may correspond to a mode. In some embodiments, the laser source may have a single mode. For example, the laser source may have a longitudinal mode in the spectral domain. In some embodiments, the laser source may have multiple modes. Coherence can be determined by how many spectra multiple modes pass. For example, the more modes, the wider the spectrum and the lower the coherence of the light. In some embodiments, it may be desirable to have a laser with low coherence. A less coherent laser can be achieved by chaotic mode hopping the laser.
Referring to fig. 2A-2D, some general component options are shown. In portions of the detailed description that follows the discussion of fig. 2A-2D, various systems, subsystems, and components are presented for purposes of a display system that provides high-quality comfort perception for mixed reality (e.g., VR and/or AR).
As shown in fig. 2A, an
The local processing and
In one embodiment, the
As described with reference to fig. 2A-2D, the AR system continuously receives input from various devices that collect data about the AR user and the surrounding environment. One of the inputs that may be received is a light source from various embodiments of a diffuser system for minimizing laser speckle in AR and other mixed reality systems, as explained in further detail below.
FIG. 3 is a graphical representation of a laser speckle pattern from a conventional coherent laser beam.
These
One method of generating the laser diode chaos is to use external optical feedback. The time delay relative to the internal time scale of the laser and the sensitivity of the phase of the return field from the external optical feedback are scaled to cause chaos. In some embodiments, the delayed reflection back to the laser and its interaction with the field in the gain medium may cause chaos. However, in practice, this approach cannot successfully completely eliminate the speckle pattern because, by way of example, the broadening of the emission spectrum may be insufficient.
FIG. 4 illustrates a schematic diagram of an optical system for reducing laser speckle through a mirror, according to some embodiments. The optical system includes: a
Fig. 5 shows a schematic diagram of an optical system for reducing laser speckle through a diffuser, according to some embodiments. The system comprises: a
The
In some embodiments, both
In some embodiments, the combination of feedback from
Fig. 6 shows a schematic diagram of an optical system for reducing laser speckle through two diffusers, according to some embodiments. A second diffuser 607 is placed behind the first diffuser 603 to help diffuse the beam 611 more uniformly.
The pseudo-random diffusing surface of the first diffuser 603 causes the reflected light rays 609 to be reflected back into the laser diode 601. Photons associated with the reflected light rays 609 bounce back from each portion in the first diffuser 603, thereby generating a large number of reflected light rays 609 to scatter the light. The diffuse light beam 611 (e.g., light propagating through the first diffuser 603) will enter the second diffuser 607. Modulator 605 also helps produce a less speckle pattern due to the chaotic laser pattern.
The first diffuser 603 acts in concert with the change in power to the laser diode 601 to push the light into the chaos. In some embodiments, the combination of feedback from the backscattered light pattern (e.g., reflected light rays 609) and the modulation of the laser current by modulator 605 drives the laser light pattern into chaos. The first diffuser 603 may include a repeating pattern as well as a random or pseudo-random pattern. The interaction of the modulation from the modulator 605 with the reflected light rays 609 reflected by the first diffuser 603 causes the laser diode 601 to be chaotic. When the reflected rays 609 are reflected back into the laser diode 601, they may interfere with different modes of the laser diode 601.
Fig. 7A-7B show schematic diagrams of optical systems for reducing laser speckle through optical multimode fibers, according to some embodiments. Multimode fiber 707 is a fiber designed to carry multiple light rays or multiple modes simultaneously. Most multimode optical fibers have a large core diameter that helps to propagate multiple optical modes at slightly different angles of reflection within the fiber core.
Fig. 7A shows the pseudo-random
Laser light from a
Propagating the light through the multimode optical fiber 707 may further homogenize the light. In some embodiments, the light output from multimode fiber 707 can be used to illuminate a spatial light modulator used in augmented reality glasses.
Fig. 7B shows a schematic representation of an optical system of augmented reality glasses according to some embodiments. The optical system of the augmented reality glasses may include an
The
FIG. 8 illustrates a schematic diagram of an optical system for reducing laser speckle to illuminate a flat panel display, in accordance with some embodiments.
Fig. 8 shows a
During operation, the
After propagating through
The
Speckle can be avoided by using a light source.
Fig. 9 shows a schematic diagram of an optical system for reducing laser speckle with a homogenizer, according to some embodiments.
The
Fig. 9 also shows a
In some embodiments,
Various exemplary embodiments of the present disclosure are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable embodiments of the present disclosure. Various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the disclosure. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process action or actions, or process step or steps, to the objective or objectives, spirit or scope of the present disclosure. Furthermore, as will be understood by those of skill in the art, each of the individual variations described and illustrated herein has discrete components and features that may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. All such modifications are intended to fall within the scope of the claims associated with this disclosure.
The present disclosure includes methods that may be performed using the subject devices. The method may include the act of providing such an appropriate device. Such provision may be performed by the end user. In other words, the act of "providing" merely requires the end user to obtain, access, approach, locate, set, activate, power up, or otherwise provide the necessary equipment in the subject method. The methods described herein may be implemented in any order of events and in any sequence of events that is logically possible.
Exemplary embodiments of the present disclosure and details regarding material selection and fabrication have been set forth above. As to other details of the present disclosure, these may be understood in conjunction with the above referenced patents and publications and as generally known or understood by those skilled in the art. Method-based embodiments of the present disclosure are equally applicable in terms of additional acts that are commonly or logically employed.
Additionally, while the present disclosure has been described with reference to several examples that optionally include various features, the present disclosure is not limited to those described or indicated as contemplated for each variation of the present disclosure. Various changes may be made and equivalents may be substituted for those described (whether referred to herein or not for the sake of brevity) without departing from the true spirit and scope of the disclosure. Further, where a range of values is provided, it is understood that each intervening value, to the extent that there is a stated upper and lower limit to that range, and any other stated or intervening value in that stated range, is encompassed within the disclosure.
Likewise, it is contemplated that any optional feature of the described inventive variations may be set forth and claimed independently or in combination with any one or more of the features described herein. References to a single item include the possibility that there are multiple of the same item. More specifically, as used herein and in the claims associated therewith, the singular forms "a," "an," "the," and "the" include plural referents unless the context clearly dictates otherwise. In other words, use of the article allows for "at least one" of the subject item in the description above and in the claims associated with this disclosure. It should also be noted that such claims may be drafted to exclude any optional element. Accordingly, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only," and the like in connection with the recitation of claim elements, or use of a "negative" limitation.
The term "comprising" in the claims associated with this disclosure should, without the use of such exclusive terminology, be taken to permit the inclusion of any additional element, whether or not a given number of elements are recited in such claims, or the addition of a feature may be viewed as altering the nature of elements set forth in such claims. Unless specifically defined herein, all technical and scientific terms used herein are to be given their broadest possible, commonly understood, meaning while maintaining the validity of the claims.
In the foregoing specification, the disclosure has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure. For example, the process flow described above is described with reference to a particular ordering of process actions. However, the ordering of many of the described process actions may be changed without affecting the scope or operation of the disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
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