Laser based scanned beam displays typically may exhibit an artifact in the image known as speckle. Speckle is as a pattern of random intensities appearing in the projected image via interference at the plane of a display surface of the wavefronts of the scanned beam, for example via scattering of the beam off of the display surface having a surface plane that is not perfectly smooth.
Claimed subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, such subject matter may be understood by reference to the following detailed description when read with the accompanying drawings in which:
It will be appreciated that for simplicity and/or clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.
In the following detailed description, numerous specific details are set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and/or circuits have not been described in detail.
In the following description and/or claims, the terms coupled and/or connected, along with their derivatives, may be used. In particular embodiments, connected may be used to indicate that two or more elements are in direct physical and/or electrical contact with each other. Coupled may mean that two or more elements are in direct physical and/or electrical contact. However, coupled may also mean that two or more elements may not be in direct contact with each other, but yet may still cooperate and/or interact with each other. For example, “coupled” may mean that two or more elements do not contact each other but are indirectly joined together via another element or intermediate elements. Finally, the terms “on,” “overlying,” and “over” may be used in the following description and claims. “On,” “overlying,” and “over” may be used to indicate that two or more elements are in direct physical contact with each other. However, “over” may also mean that two or more elements are not in direct contact with each other. For example, “over” may mean that one element is above another element but not contact each other and may have another element or elements in between the two elements. Furthermore, the term “and/or” may mean “and”, it may mean “or”, it may mean “exclusive-or”, it may mean “one”, it may mean “some, but not all”, it may mean “neither”, and/or it may mean “both”, although the scope of claimed subject matter is not limited in this respect. In the following description and/or claims, the terms “comprise” and “include,” along with their derivatives, may be used and are intended as synonyms for each other.
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In one or more embodiments, scanned beam projector 100 may include two or more lasers to generate a multi-color displayed image. In the embodiment shown, scanned beam projector 100 may include a green laser 110, a blue 112, and/or a red laser 114, for example to generate a red-green-blue (RGB) color image. The lasers may emit a laser beam of its respective color in which beam shaping optics 116, beam shaping optics 118, and/or beam shaping optics 120 may be disposed in the emitted beam path of the green laser 110, blue laser 112, and/or the red laser 114, respectively. For example, the beam shaping optics may include a beam collimator, a circularizer, a top-hat lens, a polarizer, and so on to shape or control the emitted beam to have a desired characteristic or profile. After passing through beam shaping optics 116, the green laser beam may be reflected off of a reflector 122 and combined with the blue laser beam emitted from beam shaping optics 118 via combiner 124. Likewise, the combined green/blue laser beams may be combined with the red laser beam emitted from beam shaping optics 120 via combiner 126 to be directed toward scanner module 138 for scanning. In one or more embodiments, scanner module 138 may comprise a microelectromechanical system (MEMS) scanner, however other types of scanning technologies may likewise be utilized, and the scope of the claimed subject matter is not limited in this respect.
The combined laser beam 154 may pass through a transmissive phase modulator 128 before it is incident onto scanner module 138. In accordance with one or more embodiments, transmissive phase modulator 128 is capable of performing transverse phase modulation on the combined laser beam 154 prior to being scanned by scanner module 138 which scans the beam to generate a projected image and before the beam reaches the image plane located on projection surface 142 in order to reduce or eliminate speckle in the projected image. In one or more embodiments, speckle may be defined herein as a pattern of random intensities appearing in the projected image via interference at the plane of display surface 142 of the wavefronts of the scanned beam 140, for example via scattering of the beam off of projector surface 142 having a surface that is not perfectly smooth.
In one or more embodiments, the combined laser beam 154 may be directed onto the scanner module 138 which in turn may scan the projected beam 140 onto projector surface. An optional optic 132 may be provided at the point of entry of the laser beam 154 into beam coupler 130, for example to provide focusing of laser beam 154 or to provide a clipping aperture to allow for a desired amount of clipping of laser beam 154 and/or to couple laser beam 154 to scanner module 138. In one or more embodiments, modulation states of the modulator and aperture size may be utilized in combination to result in the same or nearly the same intensity of the laser beam 154 for all or nearly all of the modulation states. After entering beam redirector 130, laser beam 154 may be redirected via one or more reflector surfaces to impinge on scanner module 138. In one or more embodiments, a reflective spatial phase modulator 134 may be utilized to implement at least part of the redirection of laser beam 154, for example to provide the functions of a fold mirror, and/or to provide transverse phase modulation of laser beam 154 to reduce or eliminate speckle in the projected image in a manner substantially similar to transmissive phase modulator 128 except that reflective phase modulator is reflective rather than transmissive. An internal reflector 138 may redirect the laser beam emitted from reflective spatial phase modulator 134 to impinge on scanner module 138 at a desired input angle suitable for scanning by scanner module 138. In one or more embodiments, scanner module 138 comprises one or two one-dimensional (1-D) scanners or alternatively a two-dimensional (2-D) scanner capable of being modulated to redirect the laser beam into a controlled pattern to generate the projected image at projection surface 142 that may be a one-dimensional or a two-dimensional image. In one or more embodiments, scanner module 138 may be driven to operate resonantly in one or more dimensions, or alternatively may be driven to operate non-resonantly in one or more dimensions, and the scope of the claimed subject matter is not limited in this respect. A controller 144 of scanned beam display 100 may be utilized to control transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134 to control the amount of transverse phase modulation of laser beam 154 to result in a desired amount of speckle reduction.
In accordance with one or more embodiments, speckle reduction may be accomplished via the averaging of multiple speckle patterns with the eye. In such embodiments, multiple speckle patterns may be presented to the eye wherein the speckle patterns are changed or modulated within the integration time, also known as persistence, of the image presented to the eye. The multiple speckle patterns are created by changing the modulation pattern or profile of the spatial phase modulator such as transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134. Furthermore, it should be noted that in accordance with one or more embodiments the spatial phase modulators discussed herein such as spatial phase modulator 128 and/or reflective spatial phase modulator 134, at least in part in some embodiments and entirely in other embodiments, are not disposed in an image plane such as at projection surface 142. Thus, in one or more embodiments, the modulation pattern may be changed at a location other than at the image plane, although the scope of the claimed subject matter is not limited in this respect.
In one or more embodiments, one or both of transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134 may comprise various structures or apparatuses that are capable of controlling the transverse phase of the laser beam 154. For example, the spatial phase modulators may comprise a multi-pixel phase modulator for a combined laser beam path before laser beam 154 reaches scanner module 138. Possible technologies for transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134 may include liquid crystal devices such as a nematic liquid crystal (NLC) device or a ferroelectric liquid crystal (FLC) device, other electro-optic materials, a flexible membrane, a transmissive device with locally addressable index of refraction, a reflective device with locally addressable index of refraction, a pixilated device comprising multiple plungers each of which is capable of being actuated to reflect laser beam 154 from different longitudinal positions, a single cell liquid crystal (LC) device comprising an electrode on one surface sufficient enough resistance such that different voltages placed on two sides of the electrode will cause a gradient or varying electric field to be imposed across the LC cell, among many examples. In some embodiments, reflective spatial modulator 134 may comprise a single cell such as a reflective membrane the surface profile of which may be deformed for example by electrical actuation or mechanical actuation. In alternative embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may comprise a diffraction grating or blazed diffracting grating that induces a tilt in order to alter the phase of the light beam 154. In some embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may comprise an acoustically actuated device to select the desired modulation states of the modulators. In some particular embodiments, reflective spatial phase modulator 134 may comprise a liquid crystal phase modulator utilized as a fold mirror by compensating for the angle of incidence of laser beam 154 on the liquid crystal. However, these are merely example tangible embodiments of transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134, and the scope of the claimed subject matter is not limited in this respect.
In one or more embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may be capable of implementing spatial phase modulation on laser beam 154 without affecting the beam size and/or quality. For example, spatial phase modulator 128 and/or spatial phase modulator 134 may comprise a single pixel liquid crystal phase modulator for scanned beam projector 100. In such a spatial phase modulator, there will be two polarizations states of the modulator. Therefore, the beam quality will not be affected, and the spot size will not change. In some embodiments, more allowance may be provided for spot size growth for the vertical direction than for the horizontal direction, although the scope of the claimed subject matter is not limited in this respect.
In some embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may be utilized to optimize both phase modulation and polarization modulation. The added polarization diversity that can be achieved using the modulator in this way can further reduce speckle via polarization diversity. Some liquid crystal modulators can be configured to both modulate the spatial phase profile and also change the polarization profile.
The modulation states of spatial phase modulator 128 and/or spatial phase modulator 134 may be designed to be orthogonal or as orthogonal as possible for the highest or nearly highest speckle reduction effect. In such an arrangement, the term orthogonal may refer to independent states where a maximum or nearly maximum potential speckle reduction may be achieved such that the states are at least partially or completely uncorrelated and/or produce independent or nearly independent speckle patterns for one or more of the states. By providing orthogonal or sufficiently different modulation states, N number of states may result a reduction in speckle contrast in an amount of 1/√N. If the speckle patterns induced by the spatial phase modulators may not be sufficiently different or orthogonal, which may result in at least a partial overlap of the modulation states and the speckle reduction may be somewhat less than 1/√N. In some embodiments, the modulation states of spatial phase modulator 128 and/or spatial phase modulator 134 may be orthogonal or nearly orthogonal to result in a speckle reduction of about 1/√N, and in other embodiments the modulation states of spatial phase modulator 128 and/or spatial phase modulator 134 may be somewhat less than orthogonal yet still yield a sufficient amount of speckle reduction that is acceptable to a user of scanned beam projector 100, and the scope of the claimed subject mater is not limited in this respect. In certain embodiment, the user may select from a set of preset modulation patterns to choose a modulation pattern results in speckle reduction that is amenable to the user. In some embodiment of scanned beam display 100, transmissive spatial phase modulator 128 and/or reflective spatial phase modulator may be designed in such a manner that the modulators are not sensitive to the polarization state of the incoming laser beam 154, and more specifically not sensitive to orthogonal polarization states of the incoming laser beam 154.
In one or more embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may be utilized to optimize both the phase modulation and polarization modulation such that further speckle reduction may be accomplished by using polarization modulation to induce polarization variations in the speckle patterns. In such embodiments, an additional modulation apparatus may be utilized to provide polarization modulation that is separate from spatial phase modulator 128 and/or spatial phase modulator 134, or alternatively the polarization modulation may be accomplished via the same device that also provides phase modulation. For example spatial phase modulator 128 and/or spatial phase modulator 134 may comprise a liquid crystal device that is capable of modulating both the spatial phase and the polarization of laser beam 154, although the scope of the claimed subject matter is not limited in this respect.
In some embodiments of scanned beam display 100, orthogonal phase modulation states for spatial phase modulator 128 and/or spatial phase modulator 134 may be obtained by using Hadamard transforms, Hermite, Laguerre, and/or Zernike polynomials, or combinations thereof. In particular embodiments, modulation states for modulator 128 and/or modulator 134 may be selected to be free-space Eigen functions so that the laser beam 154 will propagate at greater efficiency. In certain embodiments, a combination of the selected modulation states of spatial phase modulator 128 and/or spatial phase modulator 134 with the aperture size for laser beam 154 may be selected to optimize a desired amount of speckle reduction. For example, optic 132 may include a clipping aperture to provide an appropriate aperture for laser beam 154 in combination with the modulation states.
In one or more embodiments, scanned beam display 100 may comprise spatial phase modulator 128 and/or spatial phase modulator 134 that is capable of modulating both polarization and phase as a single device. In some embodiments, modulator 128 and/or modulator 134 may be capable of implementing continuous or analog phase modulation states and/or discrete phase modulation states such as binary quantized phase modulation and/or multi-state quantized phase modulation. In some embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may comprise a single phase modulator device capable of modulating two or more colors such as all three RGB colors, optionally in an optimum arrangement for two or more colors, for example by having each individual beam hit the spatial phase modulator at a slightly different angle. In one or more alternative embodiments, speckle reduction may be obtained through a separate phase modulator and polarization modulator.
In one or more embodiments, transmissive spatial phase modulator 128 and/or reflective spatial phase modulator 134 may be designed, along with the selected modulation states, so that the spot growth of laser beam 154 is minimized or nearly minimized. Furthermore, in some embodiments, modulator 128 and/or modulator 134 may be designed, along with the modulation state, so that impact to the resolution of the image projected by scanned beam projector 100 is minimized or nearly minimized. For example, in some embodiments, changes to the spot size in the vertical direction may be limited to the vertical direction, where the spot can grow in a vertical direction without impacting resolution of the displayed image. In some embodiments, vertical spot growth may be selected and/or optimized to reduce raster pinch issues in the raster scan. In some embodiments, spatial phase modulator 128 and/or spatial phase modulator 134 may be designed, along with the modulation states, so that any spot growth may be constant or nearly constant in all or nearly all modulation states. In some particular embodiments, the user of scanned beam display may be capable of manually adjusting the spot growth to achieve a desired ratio of pixel size to spot size that is visually appealing to the user for a given projection distance, image content, specific screen material of display surface 142, personal preference, lighting conditions, and so on. In some embodiments, the set of adjustments used could be optimized for the particular application and/or customer, for example to optimize efficiency, spot size growth, polarization, and so on. In some embodiments, scanned beam display 100 could be adapted for non-projection applications, for example in eyewear or head-up displays (HUD), and so on, wherein the shape of the spot and the energy distribution in the spot may impact performance. In such embodiments, scanned beam projector may include a control to allow optimization which may be set during manufacturing, and/or which may be user adjustable for example to provide adjustments over the life scanned beam display and/or for each individual user optimize his or her experience. In some embodiments, an additional adjustment mechanism may be provided to allow altering the polarization of laser beam. In some embodiments, such adjustments may be performed statically, that is adjusted to a fixed setting, or dynamically in which adjustments are continually made as needed, for example via feedback into controller 144 to dynamically alter the spot growth and/or to reduce speckle. In such embodiments, a feedback mechanism may be used to obtain an indication of the amount of speckle and/or spot size such as proximity detection, machine vision, and so on, and the scope of the claimed subject matter is not limited in these respects.
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Although the claimed subject matter has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and/or scope of claimed subject matter. It is believed that the subject matter pertaining to speckle reduction in display systems using transverse phase modulation in a non-image plane and/or many of its attendant utilities will be understood by the forgoing description, and it will be apparent that various changes may be made in the form, construction and/or arrangement of the components thereof without departing from the scope and/or spirit of the claimed subject matter or without sacrificing all of its material advantages, the form herein before described being merely an explanatory embodiment thereof, and/or further without providing substantial change thereto. It is the intention of the claims to encompass and/or include such changes.