Virtual and augmented reality system and method for reducing speckles

Abstract

The invention relates to speckle attenuating virtual and augmented reality systems and methods. 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 frequency spectrum having an envelope with a width of 3 to 10 nanometers. The system further includes a diffusing element at a distance of at least 0.1 mm to 0.5 mm from the diode laser to couple a portion of the beam back into the laser diode. Another embodiment relates to illuminating a flat panel display or a spatial light modulator using a diffusing element.

Description

[0001] This application is a divisional application of an application with a filing date of July 5, 2018, a PCT international application number of PCT / US2018 / 040954, a Chinese national phase application number of 201880044941.1, and an invention name of “Virtual and augmented reality systems and methods for reducing speckle”. Background Art

[0002] Modern computing and display technologies have 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 users in a manner that they appear to be real or can be perceived as real. Virtual reality or "VR" scenes typically involve the presentation of digital or virtual image information, while the actual real-world visual background is invisible, so that the user perceives only the digital or virtual image, without any light / image directly from the real world. Augmented reality or "AR" scenes will involve the presentation of digital or virtual image information as an enhancement of the perception of the actual world around the user (i.e., visible to other actual real-world visual inputs), so that the user perceives digital or virtual content as an object (i.e., a virtual object) in a real-world environment. Therefore, AR scenes involve the presentation of digital or virtual image information accompanied by views of other actual real-world visual inputs. The human visual perception system is very complex. Therefore, it is challenging to produce VR or AR technologies that facilitate the comfortable, natural, and rich presentation of virtual image elements outside of other virtual or real-world image elements.

[0003] A speckle pattern is an intensity pattern produced by the mutual interference of multiple wavefronts emitted from a coherent source. Speckle refers to the random granular pattern that can be observed when a highly coherent light beam (e.g., a beam from a laser) is diffusely reflected at a rough surface (such as paper, white paint, display screens, or metal surfaces). This phenomenon is caused by the interference of different reflected parts of the incident light beam with random relative optical phases. Laser speckle structures are generated whenever a laser beam propagates through a diffuser or reflects from a diffusely reflecting surface. The speckle structure depends on the coherent properties of the laser radiation and appears due to the interference of a large number of scattered waves with random initial phases.

[0004] Speckle patterns can severely degrade the image quality of a projection display that includes a laser source. Since lasers are coherent narrow-band light sources, lasers produce interference patterns. As such, the quality of images generated using a projection display with a laser source can be degraded because the lasers tend to interfere at various points. Additionally, interference generated by diffraction at large numbers of scattering particles (e.g., dust) on the projection optics will also degrade the image quality. The accumulation of degraded quality of images from various sources causes the final image to appear grainy and distorted.

[0005] Therefore, there is a need to reduce laser speckle in virtual reality or augmented reality systems. Summary of the invention

[0006] Embodiments of the present disclosure provide a system for reducing 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 random pattern or pseudo-random pattern surface that causes multiple beam rays to bounce from different locations of the diffuse surface and scatter back into the laser diode, thereby producing a complex superposition of modes in the laser gain medium, thereby inducing mode jumps in the laser resonator. These mode jumps reduce coherence because each of them is associated with a slightly different emission frequency. The laser is also further driven into chaotic operation by a combination of received optical feedback and current modulation. In other embodiments, the diffuser and changes in power from the laser work together to push the laser into chaos.

[0007] In one embodiment, an imaging system for reducing laser speckle includes a diode laser for generating a light beam, wherein the light beam has a wavelength in the visible spectrum. The system also includes a modulator for changing a current used to drive 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 beam to generate a chaotic laser pattern.

[0008] In one or more embodiments, the modulator changes 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 may also include a second diffuser, which is disposed on the side of the diffuser opposite to the laser diode, wherein the second diffuser receives a second portion of the light beam. The system may also include a lens, which is disposed on the side of the diffuser opposite to the laser diode to receive another portion of the light beam propagating through the diffuser. The system may further include a multimode optical fiber, which is disposed on the side of the lens opposite to the diffuser to adjust the timing of the portion of the light beam as the portion of the light beam 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 light beam after the portion of the light beam travels through the lens, the distal end corresponding to the light source.

[0009] In one or more embodiments, the system further includes: a projection light source; a beam splitter disposed on a side of the diffuser opposite to 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 a liquid crystal on silicon or a digital light processor. The system may also include a homogenizer for smoothing irregularities in the light beam to produce a uniform pattern.

[0010] 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. In addition, the system includes a 2D spatial light modulator optically coupled to the diffuser.

[0011] 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.

[0012] 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 also include a polarizing beam splitter disposed 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.

[0013] In one or more embodiments, the waveguide eyepiece includes an incoupling grating and an exit pupil expansion grating, which is coupled to the incoupling grating through the waveguide eyepiece.

[0014] 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 illustrative and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings illustrate the design and utility of various embodiments of the present disclosure. It should be noted that the drawings are not drawn to scale and that elements of similar structure or function are represented by the same reference numerals in all drawings. In order to better understand how to obtain the above and other advantages and purposes of the various embodiments of the present disclosure, the present disclosure briefly described above will be described in more detail by reference to the specific embodiments of the present disclosure illustrated in the drawings. It should be understood that these drawings depict only typical embodiments of the present disclosure and therefore should not be considered to limit its scope. The present disclosure will be described and explained with additional features and details through the use of the following drawings, in which:

[0016] Figure 1A Depicted is a graph of amplitude versus wavelength for a laser operating in a single mode, according to some embodiments.

[0017] Figure 1B Depicted is a graph of amplitude versus wavelength for a laser operating in chaotic mode, according to some embodiments.

[0018] FIG. 2A to FIG. 2D Schematically depicted are views of a wearable AR device according to various embodiments.

[0019] Figure 3 Depicted are exemplary speckle patterns according to some embodiments.

[0020] Figure 4 An alternative method of reducing laser speckle according to some embodiments is schematically depicted.

[0021] Figure 5 An optical system for reducing laser speckle via a diffuser is schematically depicted in accordance with some embodiments.

[0022] Figure 6 An optical system for reducing laser speckle via two diffusers is schematically depicted in accordance with some embodiments.

[0023] FIG. 7A to FIG. 7B An optical system for reducing laser speckle through multimode optical fiber is schematically depicted in accordance with some embodiments.

[0024] Figure 8 An optical system for reducing laser speckle using a light source is schematically depicted in accordance with some embodiments.

[0025] Fig. 9An optical system for reducing laser speckle via a homogenizer is schematically depicted in accordance with some embodiments. DETAILED DESCRIPTION

[0026] Various embodiments will now be described in detail with reference to the accompanying drawings, which are provided as illustrative examples of the present disclosure, so that those skilled in the art can practice the present disclosure. It should be noted that the following drawings and examples are not meant to limit the scope of the present disclosure. In the case where some elements of the present disclosure can be partially or completely realized using known components (or methods or processes), only those parts in such known components (or methods or processes) necessary for understanding the present disclosure will be described, and the detailed description of other parts in such known components (or methods or processes) will be omitted, so as not to obscure the present disclosure. In addition, various embodiments encompass the current and future known equivalents of the components mentioned in this article by way of example.

[0027] Throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0028] Many embodiments are shown and described. To facilitate understanding, the same reference numerals are used between the various figures to identify the same or similar structures, even though in some cases these structures may not be the same.

[0029] The optical systems 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 an AR system.

[0030] Overview of Problems and Solutions

[0031] The following disclosure describes various embodiments of systems and methods for mitigating laser speckle. According to certain embodiments, speckle is reduced by using a laser source driven into a chaotic regime ("coherence collapsed 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 causes chaotic operation of the laser. A laser operating in a chaotic mode exhibits a wider spectrum than a laser operating in a single mode. In certain embodiments described herein, a diffuser is used to cause a laser that would otherwise operate in a single mode to operate chaotically. In some embodiments, the current driving the laser is additionally modulated to increase the chaotic behavior of the laser.

[0032] Illustrative Optical Systems

[0033] Before describing the details of embodiments of the light distribution system, a brief description of an illustrative optical system will be given. Although the embodiments can be used with any optical system, a specific system (eg, an AR system) is described to illustrate the technology underlying the embodiments.

[0034] In order to present 3D virtual content to the user, the augmented reality (AR) system projects images of the virtual content into the user's eyes so that they appear to originate from various depth planes spaced apart at various distances in front of the user (i.e., orthogonally away from the user's eyes). In other words, the virtual content can 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 can also appear to change depth in the Z direction so that the user can perceive the object to be close, at an infinite distance, or at any distance in between. In other embodiments, the user can perceive multiple objects at different depth planes at the same time. For example, the user can see a virtual dragon appear at a very long distance and then run towards the user. Alternatively, the user can simultaneously see a virtual bird at a distance of 3 meters away from the user and a virtual coffee cup at an arm's length (about 1 meter) from the user.

[0035] In some embodiments, each eyepiece includes a stack of transparent waveguides. Each waveguide can be provided with an incoupling optical feature, an outcoupling feature, and optionally one or more additional optical features for distributing light on the outcoupling feature. Each specific waveguide outputs light at an angle corresponding to the angle at which the light is input into the specific waveguide. The stack of waveguides can include waveguides that are dedicated to a specific color component (e.g., red, green, or blue) and that impart a specific convex wavefront curvature to the outgoing light. One way to impart the wavefront curvature is to implement the outcoupling feature as a transmission diffraction grating with curved grating grooves, as taught in U.S. Provisional Patent Application No. 62 / 384,552, filed on September 9, 2016, entitled “Mixed Reality Systems Including ThickMedia and Related Methods”. Each wavefront curvature corresponds to a specific virtual image distance. By providing multiple waveguides imparting different curvatures, multiple virtual image distances can be generated. In one example, each eyepiece can 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 a second of the two sets may be configured to impart a second wavefront curvature.

[0036] As will be explained in further detail below, the light from a single-mode laser is monochromatic and coherent. When such coherent light is reflected by a diffuse surface with some optical-scale surface features, each point on the surface becomes a virtual wave source, and the waves from different points interfere constructively and destructively, according to Huygens' principle. This results in the generation of an interference pattern, also called a speckle pattern.

[0037] FIG. 1a is a graph showing the relationship between amplitude and wavelength of a laser having a spectral line width. 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 narrow curve 100a in FIG. 1a. The laser produces a spatially and temporally coherent beam. This spatial coherence allows the light from the laser to be collimated into a small divergence diffraction-limited beam. The narrow spectrum of a single-mode coherent laser (denoted as ΔΛ in FIG. 1a) shows only one peak.

[0038] FIG1b is a graph showing the amplitude versus wavelength of a chaotic laser. The laser has multiple peaks 100b, rather than just a single peak (as compared to the narrow spectrum 100a in FIG1a). In some embodiments, the bandwidth (ΔΛ) of the light emitted by the laser is in the range of 2 nanometers to 15 nanometers. This wider wavelength range causes the laser to exhibit much lower coherence, which reduces the contrast of the speckle pattern produced by the light from the laser and makes the laser operate more like a conventional white light source. In contrast to coherent light, incoherent light does not have a fixed phase relationship between different spatial points in the emitted light beam. Chaotic mode jumps include temporal incoherence and spatial incoherence.

[0039] Using a laser source can have several advantages. In some embodiments, a laser source can have a smaller etendue than other light sources. In some embodiments, light can be more easily collimated 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, a laser source can be more efficient than other light sources.

[0040] In some embodiments, all photons emitted by a laser source may be in phase and may be coherent with each other. These characteristics may, among other things, produce speckle. Each group of coherent photons may correspond to a mode. In some embodiments, a laser source may have a single mode. For example, a laser source may have a longitudinal mode in the spectral domain. In some embodiments, a laser source may have multiple modes. Coherence may be determined by how many spectra a plurality of modes pass through. 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 lower coherence. A laser with lower coherence may be achieved by performing chaotic mode hopping on the laser.

[0041] refer to FIG. 2A to FIG. 2D , showing some general widget options. FIG. 2A to FIG. 2D In the sections of the detailed description that follow the discussion of the present invention, various systems, subsystems, and components are presented to achieve the purpose of providing a high-quality, comfortable perception display system for mixed reality (e.g., VR and / or AR).

[0042] like Figure 2A As shown, an AR system user 60 is depicted wearing a head-mounted assembly 58 that features a frame 64 structure coupled to a display system that includes an eyepiece waveguide 62 positioned in front of the user's eyes. A speaker 66 is coupled to the frame 64 in the depicted configuration and is positioned adjacent to the user's ear canal (in one embodiment, another speaker not shown is positioned adjacent to the user's other ear canal to provide stereo / shapeable sound control). The display system can be operably coupled 68 to a local processing and data module 70, such as by a wired lead or a wireless connection, which can be mounted in a variety of configurations, such as fixedly attached to the frame 64, fixedly attached to a display system such as in FIG. Figure 2B The helmet or hat 80 shown in the embodiment of FIG. 1 is embedded in the earphones to Figure 2C The backpack configuration shown in the embodiment of FIG. 1 may be removably attached to the torso 82 of the user 60, or in a manner as in Figure 2D The belt-coupled configuration shown in the embodiment of FIG. 8 is removably attached to the hip 84 of the user 60 .

[0043] The local processing and data module 70 may include an energy-efficient processor or controller, and digital memory (such as flash memory), both of which may be used to facilitate processing, caching, and storage of (a) data captured from sensors that may be operably coupled to the frame 64, such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radios, and / or gyroscopes; and / or (b) data acquired and / or processed using the remote processing module 72 and / or remote data repository 74, possibly for transmission to a display after such processing or retrieval. The local processing and data module 70 may be operably coupled 76, 78 to the remote processing module 72 and remote data repository 74, such as via a wired or wireless communication link, so that these remote modules 72, 74 are operably coupled to each other and can be used as resources for the local processing and data module 70.

[0044] In one embodiment, the remote processing module 72 may include one or more relatively powerful processors or controllers configured to analyze and process data and / or image information. In one embodiment, the remote data repository 74 may include a relatively large-scale digital data storage facility that may be available via the Internet or other network configuration in a "cloud" resource configuration. In one embodiment, all data may be stored in the local processing and data module and all calculations may be performed in the local processing and data module, allowing fully autonomous use from any remote module.

[0045] As reference FIG. 2A to FIG. 2D As described, 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 can be received is a light source from various embodiments of a diffuser system that is used to minimize laser speckle in AR and other mixed reality systems, as explained in further detail below.

[0046] Figure 3 300 is an illustration of a laser speckle pattern from a conventional coherent laser beam. Laser speckle 300 refers to the random particle pattern observed when a highly coherent beam of light is diffusely reflected at a complex surface (e.g., a rough surface) such as a metal surface, a display screen, white paint, or paper. As shown, the random particle pattern includes randomly distributed light and dark spots.

[0047] These speckle patterns 300 appear as unwanted granular noise on the projected image and can severely degrade the image quality of a projection display system using laser illumination. The speckle pattern is caused by the interference of the differently reflected portions of the incident light beam, which may have a random relative optical phase due to the differences in their travel paths. For each pixel of a display system using a laser illumination source, the interference from the reflected portions may also contribute to the intensity variation.

[0048] One approach to generating chaos in laser diodes is to use external optical feedback. The chaos is caused by scaling the sensitivity of the time delay relative to the internal time scale of the laser and the phase of the return field from the external optical feedback. In some embodiments, the delayed reflection back to the laser and its interaction with the field within the gain medium can cause chaos. However, in practice, this approach may not succeed in completely eliminating the speckle pattern because, as an example, the broadening of the emission spectrum may be insufficient.

[0049] Figure 4A schematic diagram of an optical system for reducing laser speckle by a reflector according to some embodiments is shown. The optical system includes: a laser diode 401, which includes a laser driven by a modulator 403; and an external optical feedback mechanism (including a reflector 405). The laser diode 401 emits a laser beam 407. Under the right conditions, the laser beam 407 can bounce off the reflector 405 so that a small portion of the laser emission returns to the laser diode 401. The reflection back into the laser diode 401 may result in some chaotic outputs with different types of waveforms and characteristics. Feedback can be provided from a simple external reflector, or feedback can be provided by a more complex configuration, resulting in different paths to chaos. This embodiment may not be very effective in eliminating laser speckle because a single reflection from the reflector 405 into the laser diode 401 may not produce a mode pattern in the laser diode 401 that is complex enough to excite a large number of chaotic modes.

[0050] Figure 5 A schematic diagram of an optical system for reducing laser speckle by a diffuser according to some embodiments is shown. The system includes: a laser diode 501, which includes a laser driven by a modulator 505; and an external optical feedback mechanism (including a diffuser 503). The laser diode 501 emits a laser beam 507 having one or more wavelengths, which are typically within 5 nanometers of each other. In some embodiments, the diffuser 503 can be anywhere between 0.1 and 2 millimeters away from the laser diode 501. In some embodiments, the beam diameter of the laser beam 507 can typically be 50 to 500 microns. The diffuser 503 can be stabilized by mounting the diffuser 503 in a fixture that does not allow the diffuser 503 to move. If the diffuser 503 moves relative to the laser diode 501, the laser diode 501 will not operate in a chaotic mode. The laser diode 501 must be stable because if the diffuser 503 moves relative to the laser diode 501, the reflected pattern may be incoherent with the mode inside the laser diode 501 (and therefore, the reflected pattern may not interfere with the mode inside the laser diode 501 to produce chaos). Therefore, in some embodiments, the laser diode 501 has zero velocity relative to the diffuser 503 so that the reflected pattern and the mode inside the laser diode 501 can interfere and produce a chaotic pattern.

[0051] Diffuser 503 is a random or pseudo-random pattern that diffuses light. Diffuser 503 is particularly suitable for generating chaotic patterns due to the uneven diffusing surface. In some embodiments, diffuser 503 is a reflective diffuser.

[0052] The diffuser 503 reflects one or more randomly reflected rays 509 back into the laser diode 501. Due to the uneven surface of the diffuser 503, the diffuser 503 couples the reflected rays 509 back into the laser diode 501, but most of this light will propagate through the diffuser 503. Photons associated with the reflected rays 509 bounce back from every portion of the surface of the diffuser 503 to produce a large number of scattered beams in the reflected rays 509. In some embodiments, 2% to 4% of the light impinging on the diffuser 503 will be reflected back toward the laser diode 501. The diffuser 503 scatters the light back into the laser diode 501 to produce a complex mode superposition 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 emission frequency.

[0053] The modulator 505 is coupled to the laser diode 501 and drives the laser diode 501 by a modulated current. The modulator 505 works in conjunction with the diffuser 503 to add to the chaotic laser pattern. Each laser diode will work slightly differently from the other laser diodes, but modulation may promote the chaotic operation of the laser diode 501. The light emission scattered in the total spectral wavelength range of 3 to 5 nanometers is generated by the combination of the modulator 505, the pattern of the diffuser 503, and other features and characteristics of the laser diode 501. The parameters corresponding to the modulation waveform, the texture of the diffuser 503, and the reflectivity of the diffuser 503 determine the amount of speckle reduction. The output of the modulator 505 is coupled to the laser diode 501. The modulator 505 can modulate the light, for example, at a frequency in the range of 10kHz to 10MHz. The temporal modulation rate should be much faster than the frame rate of the display system so that the chaotic light is output flat in each image frame. In the absence of modulation, the width of the light emitted by the laser diode 501 is small, but modulation allows the display system to obtain a spectral wavelength of up to 10 nanometers.

[0054] In some embodiments, both the diffuser 503 and the variation of the power to the laser diode 501 work together to push the laser light emitted by the laser diode 501 into chaos. Most of the variation in the power of the laser diode 501 may be caused by the modulation signal from the modulator 505, but the diffuser 503 may also cause the internal power of the laser diode 501 to fluctuate. Diffusers with different structures may allow the modulator to have different spectra of both power variation and time variation, because different diffusers may produce different spectral power distributions. In some embodiments, the characteristic size of the diffuser may be in the range of 1 to 100 microns.

[0055] In some embodiments, the combination of feedback from the diffuser 503 to the laser diode 501 via reflected light 509 and modulation of the current in amplitude and frequency by the modulator 505 drives the laser pattern from the laser diode 501 into chaos. The reflected light 509 may include repeating patterns and pseudo-random patterns. Specifically, the interaction between the current modulation and the reflected light 509 makes the laser chaotic. In some embodiments, about 4% of the light from the laser diode 501 will be reflected from the diffuser 503 and returned to the laser diode 501 as reflected light 509, and a portion of this light will be diffused by the diffuser 503. The reflected light 509 interferes with different modes of the laser diode 501 to drive the light into chaos.

[0056] Figure 6 A schematic diagram of an optical system for reducing laser speckle by two diffusers according to some embodiments is shown. The second diffuser 607 is placed behind the first diffuser 603 to help diffuse the light beam 611 become more uniform.

[0057] The pseudo-random diffuse surface of the first diffuser 603 reflects reflected light 609 back into the laser diode 601. Photons associated with reflected light 609 bounce back from each portion of the first diffuser 603, thereby generating a large number of reflected light 609 to scatter the light. A diffused light beam 611 (e.g., light propagating through the first diffuser 603) will enter the second diffuser 607. The modulator 605 also helps to produce a less speckled pattern due to the chaotic laser pattern.

[0058] The first diffuser 603 and the change in power to the laser diode 601 work together to push the light into chaos. In some embodiments, the combination of feedback from the backscattered light pattern (e.g., reflected light 609) and the modulation of the laser current by the modulator 605 drives the laser pattern into chaos. The first diffuser 603 can include a repeating pattern as well as a random or pseudo-random pattern. The interaction of the modulation from the modulator 605 and the reflected light 609 reflected by the first diffuser 603 makes the laser diode 601 chaotic. When the reflected light 609 is reflected back into the laser diode 601, they can interfere with different modes of the laser diode 601.

[0059] FIG. 7A to FIG. 7B A schematic diagram of an optical system for reducing laser speckle through an optical multimode fiber according to some embodiments is shown. Multimode fiber 707 is a type of optical fiber designed to carry multiple light rays or multiple modes simultaneously. Most multimode optical fibers have a large core diameter, which helps multiple light modes propagate within the fiber core at slightly different reflection angles.

[0060] Fig. 7AA pseudo-random first diffuser 703 is shown that causes reflected light rays 709 to reflect back into the laser diode 701. Photons from the beam 708 bounce back from each portion in the first diffuser 703, causing a large number of reflected light rays 709 to scatter light. The modulator 705 also helps to produce less speckle pattern due to the chaotic laser pattern.

[0061] Laser light from a laser diode 701 driven by a modulator 705 propagates through a first diffuser 703. The light beam propagating through the first diffuser 703 also propagates through a separate focusing lens 705 before entering and propagating through a multimode optical fiber 707. The lens 705 helps to couple the light into the multimode optical fiber 707.

[0062] Propagating the light through multimode optical fiber 707 can further homogenize the light. In some embodiments, the light output from multimode optical fiber 707 can be used to illuminate a spatial light modulator used in augmented reality glasses.

[0063] Figure 7B A schematic representation of an optical system of augmented reality glasses according to some embodiments is shown. The optical system of the augmented reality glasses may include an eyepiece waveguide 102, an optical coupler subsystem 104, and a control subsystem 106. The waveguide 102 includes one or more main planar waveguides 1, and one or more diffractive optical elements (DOEs) 2 associated with each of at least some of the main planar waveguides 1.

[0064] The optical coupler subsystem 104 optically couples light into the waveguide 102 by coupling image wise modulated light to the user's eyes. Figure 7B As shown, the optical coupler subsystem 104 may include an optical element 5, such as a reflective surface, a mirror, a dichroic mirror, or a prism, to optically couple light into the edge 122 of the main planar waveguide 1. The optical coupler subsystem 104 may additionally or alternatively include a collimating element 6 that collimates light from one or more light sources (e.g., a multimode optical fiber 707 that transmits light from a laser diode 701).

[0065] The control subsystem 106 includes one or more light sources and drive electronics that generate image data encoded in the form of spatially and / or temporally varying light. As described above, the collimating element 6 can collimate the light, and the collimated light is coupled into one or more main planar waveguides 1. Figure 7B A specific laser diode 701 / diffuser 703 combination is depicted as the light source in , but other embodiments of diffuser systems for minimizing laser speckle, such as those described in other areas of the specification, may also be used as the light source.

[0066] Figure 8 A schematic diagram of an optical system for reducing laser speckle to illuminate a flat panel display is shown in accordance with some embodiments.

[0067] Figure 8 A laser diode 801 driven by a modulator 805 is shown. The laser diode 801 emits one or more wavelengths that are typically within 5 nanometers of each other. In some embodiments, the diffuser 803 can be anywhere between 0.1 and 2 millimeters away from the laser diode 801. The diffuser 803 can be stabilized by mounting the diffuser 803 in a support that does not allow the diffuser 803 to move relative to the laser diode 801. Fixing the position of the diffuser 803 relative to the laser diode 801 is beneficial for operating the laser diode 801 in a chaotic mode. If the diffuser 803 moves relative to the laser diode 801, the reflected light 809 reflected by the diffuser 803 may be incoherent with the mode of the laser diode 801.

[0068] During operation, modulator 805 provides a drive signal to laser diode 801. Laser diode 801 emits light that is mostly transmitted through diffuser 803. Laser diode 801 is optically coupled (as shown by free space propagation, but alternatively, via an optical element) to diffuser 803. Reflected light 809 (the portion of the light emitted by laser diode 801 that is reflected by diffuser 803) is coupled into laser diode 801. The modulation of the drive signal combined with the reflected light 809 causes laser diode 801 to operate in a chaotic (reduced coherence mode).

[0069] After propagating through diffuser 803, the light is optically coupled to a microdisplay (two-dimensional (2D) spatial light modulator) 807 through an illumination-side collimating lens 819 and a polarizing beam splitter (PBS) 809, which spatially modulates the light to present an image. The microdisplay includes a 2D pixel array (in Figure 8807 is not visible in the microdisplay 807). The microdisplay 807 may, for example, take the form of a liquid crystal on silicon (LCoS) spatial light modulator (SLM). Alternatively, a digital micromirror device (DMD) may be used as the microdisplay 807, in which case the PBS 809 may be replaced by an arrangement of two opposing prisms separated by an air gap. The DMD selectively deflects light to angles above and below the angle of total internal reflection at the face of the closest one of the two opposing prisms facing the air gap. The light is reflected by the microdisplay 807 back to the projection lens 811 through the PBS 809. The projection lens 811 forms a collimated light beam based on the light modulated by each pixel in the microdisplay 807. The collimated light generated by each specific pixel from the microdisplay 807 propagates at an angle determined by the position of the specific pixel. Therefore, the projection lens 811 forms a virtual image located at infinity. The light collimated by the projection lens 811 is coupled to the coupling optical element (grating) 817 located on the surface of the waveguide eyepiece 62. Thus, the microdisplay 807 is optically coupled to the incoupling grating 817 through an optical path traversing the PBS 809 and the projection lens 811. The light is coupled to the user's eye 821 via the waveguide eyepiece 62 containing the exit pupil expansion grating 819 which incrementally outcouples the light.

[0070] Diffuser 803 may have a random or pseudo-random profile surface that reflects reflected light 809 back into laser diode 801. Photons associated with reflected light 809 produce reflected scattered light. Modulator 805 also helps produce a less speckle pattern, making the mode hops of laser diode 801 more chaotic.

[0071] Speckle can be avoided by using a light source. The light coming out of the diffuser 803 will propagate through the PBS 809 to illuminate a flat panel display (e.g., a microdisplay 807). The light beam from the first diffuser 803 can also be used to directly illuminate a microdisplay 807 such as an LCoS or a digital light processor (DLP) to eliminate the flat panel display.

[0072] Fig. 9 A schematic diagram of an optical system for reducing laser speckle by a homogenizer according to some embodiments is shown. A homogenizer 905 is a device that smoothes irregularities in the laser beam profile to produce a more uniform pattern. Many homogenizers use a polygonal mirror with square facets. The mirror reflects light at different angles to produce a beam with uniform power across the beam profile.

[0073] The laser diode 901 is driven by a modulator 911. The laser diode 901 emits one or more wavelengths that are typically within 5 nanometers of each other. In some embodiments, the diffuser 903 can be anywhere between 0.1 and 2 millimeters away from the laser diode 915. The diffuser 903 can be stabilized by mounting the diffuser 903 in a fixture that does not allow the diffuser 903 to move relative to the laser diode 901. If the diffuser 903 is not securely attached relative to the laser diode 901 and moves relative to the laser diode 901 during operation, the laser diode 901 may not operate in a chaotic mode.

[0074] Fig. 9 Also shown is a diffuser 903 having a pseudo-random diffuse surface that reflects reflected light 909 back into the laser diode 901. Photons from reflected light 909 reflect back from each portion of the diffuse surface 903 to produce scattered light. The modulator 911 also helps produce less speckle pattern due to the chaotic laser pattern.

[0075] In some embodiments, a homogenizer 905 homogenizes the light coming out of the diffuser 903. The light is then re-imaged by a lens 907 to refocus the light onto the surface. This results in reduced laser speckle while having more uniform light for projecting an image.

[0076] 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 widely applicable embodiments of the present disclosure. Various changes may be made to the described disclosure, and equivalents may be substituted without departing from the true spirit and scope of the present disclosure. In addition, many modifications may be made to adapt specific circumstances, materials, material compositions, processing, one or more processing actions, or one or more processing steps to one or more purposes, spirits, or scopes of the present disclosure. In addition, as will be appreciated by those skilled in the art, each of the individual variations described and illustrated herein has discrete components and features that may be easily separated 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 the present disclosure.

[0077] The present disclosure includes methods that can be performed using subject equipment. The method may include the action of providing such appropriate equipment. Such provision may be performed by an end user. In other words, the "providing" action only requires the end user to obtain, access, approach, locate, set, activate, power on, or provide with other actions to provide the necessary equipment in the subject method. The method described herein may be implemented in any order of the events that are logically possible and the order of the events.

[0078] Exemplary embodiments of the present disclosure and details of material selection and manufacturing have been described above. As for other details of the present disclosure, these can be understood in conjunction with the patents and publications referenced above and what is generally known or understood by those skilled in the art. In terms of additional actions that are generally or logically adopted, the method-based embodiments of the present disclosure are equally applicable.

[0079] In addition, although 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 expected for each variation of the present disclosure. Various changes may be made to the described disclosure, and equivalents (whether referenced herein or not included for brevity) may be substituted without departing from the true spirit and scope of the present disclosure. In addition, where a range of values ​​is provided, it is understood that each intermediate value between the upper and lower limits of the range and any other stated value or intermediate value within the stated range is included in the present disclosure.

[0080] Likewise, it is contemplated that any optional features 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. Reference to a single item includes the possibility of the presence of multiple identical items. More specifically, as used herein and in the claims associated with this document, the singular forms "one," "an," "said," and "the" include plural indicators unless otherwise specifically stated. In other words, the use of articles allows for "at least one" in the subject items in the above specification and in the claims associated with this disclosure. It should also be noted that such claims may be written to exclude any optional elements. Therefore, this statement is intended to serve as a prior basis for the use of exclusive terms such as "alone," "only," or the use of "negative" limitations in conjunction with the narration of claim elements.

[0081] Without using such exclusive terms, the term "comprising" in the claims associated with the present disclosure shall allow for the inclusion of any additional elements, regardless of whether a given number of elements are recited in such claims, or the addition of features may be deemed to change the nature of the elements recited in such claims. Unless specifically limited herein, all technical and scientific terms used herein shall be given as broad a commonly understood meaning as possible while maintaining the validity of the claims.

[0082] In the foregoing description, the present disclosure has been described with reference to specific embodiments of the present disclosure. However, it will be apparent that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure. For example, the above-described process flow is described with reference to a specific ordering of the process actions. However, many of the orderings of the described process actions may be changed without affecting the scope or operation of the present disclosure. Therefore, the description and the accompanying drawings should be considered in an illustrative rather than a restrictive sense.

Claims

1. A near-eye display system, comprising: a laser diode configured to generate a light beam, wherein the light beam has a wavelength within the visible spectrum; a modulator coupled to the laser diode, the modulator being configured to vary a current used to drive the laser diode; a diffuser optically coupled to the laser diode, wherein the diffuser comprises a randomly patterned surface or a pseudo-random surface configured to cause a plurality of light beams including the light beam to bounce off the randomly patterned surface or the pseudo-random surface and scatter back into the laser diode as reflected light beams to generate a chaotic laser pattern; and a 2D spatial light modulator optically coupled to the diffuser, Wherein, the diffuser is further configured to allow the transmitted portion of the light beam to propagate therethrough and onto the 2D spatial light modulator.

2. The near-eye display system according to claim 1, wherein: The modulator varies the current based on at least a second chaotic laser pattern.

3. The near-eye display system according to claim 2, wherein: The power of the modulator varies based at least on the structure of the diffuser.

4. The near-eye display system according to claim 1, further comprising: A second diffuser is disposed on a side of the diffuser opposite to the laser diode, wherein the second diffuser receives a second portion of the light beam.

5. An imaging system for reducing laser speckle, the imaging system comprising: a laser diode for generating a light beam having a wavelength in the visible spectrum; a modulator for varying a current for driving the laser diode; as well as A diffuser for receiving the light beam, wherein the diffuser comprises a randomly patterned surface or a pseudo-random surface, configured to cause a reflected portion of the light beam to bounce off the randomly patterned surface or the pseudo-random surface and scatter back into the laser diode as reflected light to generate a chaotic laser pattern, and also to cause a transmitted portion of the light beam to propagate therethrough.

6. A system for reducing laser speckle, comprising: a laser diode configured to generate a light beam having a wavelength within the visible spectrum; a modulator configured to vary a current used to drive the laser diode; as well as A diffuser having a random or pseudo-random patterned surface, configured to cause at least a portion of the light beam to reflect from the random or pseudo-random patterned surface and scatter back into the laser diode as reflected light to generate a chaotic laser pattern, wherein the diffuser is also configured to cause a portion of the light beam to propagate therethrough as transmitted light.

7. A system for reducing laser speckle, comprising: a laser diode configured to generate a light beam having a wavelength within the visible spectrum; a modulator configured to vary a current used to drive the laser diode; as well as A diffuser having a random or pseudo-random patterned surface is configured to cause 2-4% of the light beam to reflect from the random or pseudo-random patterned surface and scatter back into the laser diode as reflected light to generate a chaotic laser pattern.

8. A system for reducing laser speckle, comprising: a laser diode configured to generate a light beam having a wavelength within the visible spectrum; a modulator configured to vary a current used to drive the laser diode; as well as A diffuser having a random or pseudo-random patterned surface, configured to cause at least a portion of the light beam to reflect from the random or pseudo-random patterned surface and scatter back into the laser diode as reflected light to generate a chaotic laser pattern, wherein the diffuser is spaced 0.1 mm to 0.5 mm from the laser diode.

9. A method for reducing laser speckle, comprising: generating a laser beam having a wavelength in the visible spectrum; amplitude modulating the laser beam; reflecting at least a portion of the modulated laser beam from the random or pseudo-random patterned surface back into the modulated laser beam, thereby generating a chaotic laser pattern; as well as At least a portion of the modulated laser beam is transmitted through the random or pseudo-random patterned surface.

10. A method for reducing laser speckle, comprising: generating a laser beam having a wavelength in the visible spectrum; amplitude modulating the laser beam; as well as 2-4% of the modulated laser beam is reflected from the random or pseudo-random patterned surface back into the modulated laser beam, thereby generating a chaotic laser pattern.

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