Patent ID: 12253667

DETAILED DESCRIPTION

Embodiments of a high contrast, compact (Microelectromechanical System (MEMS) based ribbon-type spatial light modulator (SLM) and systems and methods for using the same are disclosed. In the following description, numerous specific details are set forth, such as specific materials, dimensions and processes parameters etc. to provide a thorough understanding of the present invention. However, particular embodiments may be practiced without one or more of these specific details, or in combination with other known methods, materials, and apparatuses. In other instances, well-known semiconductor design and fabrication techniques have not been described in particular detail to avoid unnecessarily obscuring the present invention. Reference throughout this specification to “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

The terms “over,” “under,” “between,” and “on” as used herein refer to a relative position of one layer with respect to other layers. As such, for example, one layer deposited or disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer deposited or disposed between layers may be directly in contact with the layers or may have one or more intervening layers. In contrast, a first layer “on” a second layer is in contact with that second layer. Additionally, the relative position of one layer with respect to other layers is provided assuming operations deposit, modify and remove films relative to a starting substrate without consideration of the absolute orientation of the substrate.

Briefly, the SLM includes a linear array of active-ribbons suspended over a surface of a substrate, each active-ribbon having a split-ribbon portion including a plurality of diffractors. Each diffractor includes an active light reflective surface on a linear segment of the split-ribbon portion and at least one opening adjacent to the linear segment through which a static light reflective surface below the ribbon is exposed. The static light reflective surface is vertically offset from the active reflective surface by a quiescent optical-gap, and has a substantially equal area with the active light reflective surface. The SLM is configured or operable to bring a coherent light reflected from the active light reflective surface into interference with coherent light reflected from the static light reflective surface when one or more of the active-ribbons are deflected towards the surface of the substrate by an electrostatic force generated between a substrate-electrode and ribbon-electrode by a driver with a number of drive channels, each coupled to the ribbon-electrode in one or more of the number of active-ribbons.

FIGS.1A and1Bare schematic block diagrams illustrating an embodiment of a Microelectromechanical System (MEMS) based ribbon-type spatial light modulator (SLM) having slotted or split ribbons. For purposes of clarity, many of the details of SLMs in general and active-compact SLMs in particular that are widely known and are not relevant to the present invention have been omitted from the following description. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions may not correspond to actual reductions to practice of the invention.

Referring toFIGS.1A and1Bin the embodiment shown the SLM is a one dimensional (1D) compact SLM100that includes a linear array102composed of thousands of free-standing, addressable electrostatically actuated or deflected active-ribbons104supported over a surface106of a substrate108, each active-ribbon having a light reflective surface110and a split-ribbon portion112including a plurality of diffractors or ribbon-pairs (not shown in these figures) to form a single pixel114.

Generally, the length of the split-ribbon portion112is less than about one third (33%) of a length of the active-ribbon104. In some embodiments, the length of the split-ribbon portion112is less than about ten percent (10%) of the length of the active-ribbon104. It is noted that as described in greater detail below with respect to a displays system including a compact, compact SLM100with split-ribbon active-ribbons104, only a portion of the linear array102, including the split-ribbon portions112needs to be illuminated.

A schematic sectional side view of an elongated element or active-ribbon104of the SLM100ofFIG.1Ais shown inFIG.1B. Referring toFIG.1B, each of the active-ribbons104includes a ribbon-electrode116and is deflectable through a gap or cavity118toward the substrate108by electrostatic forces generated when a voltage is applied between the ribbon-electrode in the active-ribbon and a base or substrate-electrode120formed in or on the substrate. The ribbon-electrodes116are driven by a drive channel122in a driver124, which may be integrally formed on the same substrate108with the linear array102.

In the embodiment shown inFIG.1A, each of the active-ribbons104are driven by a single drive channel122to form a compact SLM100having a large number of pixels114. It will be understood however that alternatively two or more of the active-ribbons104can be ganged or electrically coupled together so that a single drive channel122drives ribbon-electrodes116in both active-ribbons, either to form larger pixels114having a greater number of diffractors in each pixel, or to form a repeating blaze pattern.

Referring again toFIG.1B, the active-ribbon104includes an elastic mechanical layer126to support the active-ribbon above the surface106of the substrate108, a conducting layer128forming the ribbon-electrode116and a reflective layer130including the reflective surface110overlying the mechanical layer and conducting layer.

Generally, the mechanical layer126comprises a taut silicon-nitride film (SiNx), and is flexibly supported above the surface106of the substrate108by the mechanical layer at both ends of the active-ribbon104. The conducting layer130can be formed over and in direct physical contact with the mechanical layer126, as shown, or underneath the mechanical layer. The conducting layer128or ribbon-electrode116can include any suitable conducting or semiconducting material compatible with standard MEMS fabrication technologies. For example, the conducting layer128or ribbon-electrode116can include a doped polycrystalline silicon (poly) layer, or a metal layer. Alternatively, if the reflective layer130is metallic it may also serve as the ribbon-electrode116.

The separate, discrete reflecting layer130, where included, can include any suitable metallic, dielectric or semiconducting material compatible with standard MEMS fabrication technologies, and capable of being patterned using standard lithographic techniques to form the reflective surface110.

FIG.2is a top view of two pixels in a compact SLM with split ribbons having two diffractors or ribbon-pairs per active-ribbon or pixel to decrease pixel size and pitch to provide high contrast amplitude modulation. Referring toFIG.2, each active-ribbon200has a split-ribbon portion202including multiple diffractors204aand204b, each diffractor including an active light reflective surface206on a linear segment208of the split-ribbon portion and at least one opening210adjacent to the linear segment through which a static light reflective surface212below the active ribbon is exposed.

In prior generations of compact SLMs each pixel typically has one or more pairs of an electrostatically deformable or movable ribbon having a first, active reflective surface thereon and a second, static reflective surface. The static reflective surface can be formed either on a non-moving ribbon, such as in a Flat Light Valve (FLV™) or on a surface of the substrate adjoining the moving ribbon, such as in a Grating Light Valve (GLV™).

Moving the movable ribbon brings light reflected from the first, active surface into constructive or destructive interference with light reflected from the second, static surface, thereby enabling amplitude modulation of the light.

The compact SLM with split-ribbon portions, such as shown inFIG.2, enables each active-ribbon200to form a single pixel214a,214bper active-ribbon, as compared to a conventional compact SLM, which requires two ribbons (FLV™) or two ribbon widths (GLV™) per pixel. The slotted or split-ribbon design enables higher contrast with a single ribbon for a compact array.

FIG.3is a top view of another embodiment of active-ribbons300in a compact SLM, including split-ribbon portions302having three diffractors or ribbon-pairs304a,304b,304cper active-ribbon300or pixel. This design is particularly advantageous for visible wavelength operation by providing pixels widths or pitches of less than about 5 μm. Three-ribbon pairs304a,304b, and304chave been found to provide optimal trade-off for contrast to active-ribbon count in compact SLMs at visible wavelengths. Illumination optics and requirement for a size of a ribbon-electrode will determine a region or length of the active-ribbon300that needs to be split or slotted, and generally can be very short compared to length of the active-ribbon. For example, for an active-ribbon300having total length of greater than 200 micrometers (μm) a split-ribbon portion302having a length of about 20 μm has been found to have a minimal effect on electric profile.

FIG.4is a block diagram in cross-sectional side view of three active-ribbons400or pixels of a compact SLM, each active-ribbon including a split-ribbon portion with three diffractors402, and each diffractor including an active light reflective surface404on a linear segment406of the split-ribbon portion and at least one opening408adjacent to the linear segment through which static light reflective surfaces410are exposed. In the embodiment shown, the static light reflective surfaces410are formed on a surface412of a substrate414. Referring toFIG.4it is seen that the split-ribbon portions replace three-ribbon pairs in a conventional compact SLM, such as a GLV™. Amplitude modulation is achieved via spatial filtering, where the 1storder diffraction is approximately equal to:

Diffraction⁢⁢pitchλThus, spatial filtering may be desirable to account for diffraction from neighboring pixels, where:

Pixel⁢⁢pitchλ

In the embodiment shown grayscale amplitude modulation depends on the distance from active light reflective surface404to the static light reflective surfaces410. Thus, for the active ribbon400on a left-hand side ofFIG.4where the active light reflective surface404is separated from the static light reflective surfaces410by a distance a, a 1storder reflection from this ribbon (shown by arrows416) is given by:

a=n⁢λ2+λ4where λ is a wavelength of an incident coherent light and n is an integer, all first order light reflected from the active light reflective surface404destructively interferes with that from the static light reflective surfaces410and the pixel is dark or black.

For the active ribbon400in the middle ofFIG.4where the active light reflective surface404is separated from the static light reflective surfaces410by a distance b, a 0thorder reflection from this ribbon (shown by arrow418) is given by:

b=n⁢λ2where λ is the wavelength of an incident coherent light and n is an integer, all 0thorder light reflected from the active light reflective surface404constructively interferes with that from the static light reflective surfaces410and the pixel is white.

For the active ribbon400on the right-hand side ofFIG.4where the active light reflective surface404is separated from the static light reflective surfaces410by a distance c, between a and b, the reflected light (shown by arrows420) is gray.

FIG.5is simplified optics diagram of the compact SLM500, such as that shown inFIGS.3and4, further including an lens502for directing modulated light towards or to a spatial filter504for zero order spatial or Fourier filtering, and a projection lens506for directing a selected order of light towards an imaging plane508to for an image510thereon.

It is noted that in the embodiments of the compact SLM described above and shown inFIG.4, the static light reflective surface410, is formed directly on a substantially planar surface412of the substrate414. It is will be understood that this need not always be the case. In other embodiments, the static light reflective surfaces are formed on a structure raised above the surface of the substrate to decouple a quiescent optical-gap between the static reflective surfaces and active reflective surfaces from an electrical-gap separating the active-ribbons or ribbon-electrodes therein from the surface of the substrate or substrate-electrode. Such embodiments are particularly useful to enable tuning of the compact SLM to modulate a specific wavelength or narrow range of wavelengths, while still optimizing the electrical-gap to improve driving of the active-ribbons.

One such embodiment of a compact SLM including active-ribbons with split-ribbon portions and structured substrate will now be described with reference toFIGS.6A and6B.FIG.6Ais a block diagram in cross-sectional side view of a portion of a compact SLM including a structured substrate. Referring toFIG.6A, each active-ribbon600including a split-ribbon portion with three diffractors602, and each diffractor including an active light reflective surface604on a linear segment606of the split-ribbon portion and at least one opening608adjacent to the linear segment through which static light reflective surfaces610are exposed. In the embodiment shown, the static light reflective surfaces610are formed on ridges or structures612raised above a surface614of a substrate618. Alternatively, channels or trenches can be formed into the surface614of the substrate618immediately underlying the linear segment606of the split-ribbon portion. It is noted that the substrate need only be structured or patterned in a region of the split ribbons near a center of the active-ribbons or linear array where the maximum deflection occurs. It is further noted the compact SLM can multiple substrate-electrodes620immediately underlying the linear segment606of the split-ribbon portion of the active-ribbons600, as in the embodiment shown. Alternatively, the substrate-electrode620can include a single electrode formed in the substrate618and underlying both the structures612and the linear segments606of the split-ribbon portion of the active-ribbons600.

FIG.6Bis a top view of the portion of the compact SLM ofFIG.6A.

In another embodiment, a compact SLM including active-ribbons having a split-ribbon can further including a damping structure with an electrically permeable structure under the active-ribbon on which a static light reflective surface is formed. One such embodiment and method of forming the same will now be described with respect toFIGS.7through9.FIG.7is a block diagram illustrating a portion of a compact SLM700with a damping structure including electrically permeable structure and a second air-gap under the ribbon at an intermediate point during fabrication of the compact SLM.FIG.8is a flowchart illustrating a method of fabricating the compact SLM with a damping structure.FIG.9is a block diagram illustrating a compact SLM with a damping structure fabricated according to the embodiments ofFIGS.7and8.

Referring toFIGS.7and8, the method begins with forming a lower or substrate-electrode702over a wafer or substrate704(step801). Generally, the substrate can include any suitable semiconductor or dielectric material such as silicon, and the substrate-electrode can include one or more layers of any suitable conducting material such as aluminum, copper, tungsten, titanium or alloys thereof and can be deposited using any suitable CVD or PVD technique and patterned using standard photolithographic techniques and etches. Optionally, as in the embodiment shown, the method can further include depositing a thin intermediate dielectric layer706, such as a silicon oxide over the substrate704prior to forming the substrate-electrode702.

Next, a layer of a sacrificial material is conformably deposited over the substrate-electrode702and patterned to form a first sacrificial layer708(step803). Generally, the sacrificial material of the first sacrificial layer708can include any suitable material exhibiting a etch selectivity to the materials of the SLM and can be patterned using standard photolithographic techniques and etches. In one embodiment the sacrificial material of the first sacrificial layer708can include an amorphous silicon or polysilicon deposited by CVD to a suitable thickness. It is noted that the thickness of the first sacrificial layer708determines a thickness of a first air gap (not shown in this figure) of the electrically permeable damping structure. Generally, this first air gap is about ⅔ of an electrical gap between the ribbons710and the substrate-electrode702. Furthermore, since a second air gap, which is subsequently formed between the ribbons710and the electrically permeable damping structure is selected to have a thickness about equal to the maximum desired stroke; the thickness of the first sacrificial layer708in one embodiment is about equal to twice the desired stroke. Generally the first sacrificial layer708has a thickness from about 0.2 μm to about 2 μm.

Next, a dielectric material is deposited and patterned to form a dielectric layer712of the electrically permeable damping structure over the first sacrificial layer708(step805). This dielectric layer712can include one or more layers of dielectric material such as silicon oxide, silicon nitride or silicon oxynitride and can be deposited by CVD, atomic layer deposition (ALD) or, in the case of silicon oxides, can be thermally grown. The dielectric material is patterned using standard photolithographic techniques and etches to form openings through which the first sacrificial material is exposed for subsequent removal. Generally the thin dielectric layer712has a thickness from about 0.1 μm to about 0.5 μm.

Next, a conformal second sacrificial layer714is formed over the dielectric layer712(step807). As with the first sacrificial layer708, the sacrificial material of the second sacrificial layer714can include any suitable material exhibiting a etch selectivity to the materials of the SLM and can be patterned using standard photolithographic techniques and etches. In a preferred embodiment, the sacrificial material of the second sacrificial layer714is the same as that of the first sacrificial layer708to enable it to be removed in single etch step, after the ribbons710are formed. Thus, in one embodiment the sacrificial material can include polysilicon deposited by CVD to a suitable thickness. As noted above, the thickness of the second sacrificial layer714determines the thickness of a second air gap between the ribbons710and the electrically permeable damping structure, and is selected to have a thickness about equal to the maximum desired stroke. Generally the second sacrificial layer714has a thickness from about 0.1 μm to about 1.0 μm.

Next, a plurality of ribbons710are formed over the second sacrificial layer714(step809). Generally, this involves two to three separate depositions, beginning with deposition of a taut silicon nitride mechanical layer, a top or ribbon-electrode layer, and deposition of a reflective layer, as shown inFIG.1B. The taut silicon nitride mechanical layer can be deposited by CVD or ALD. The top or ribbon-electrode layer can include any suitable conducting materials used for the substrate-electrode and can be deposited by PVD, CVD or ALD. The reflective layer can include any suitable metal, dielectric or semiconducting material capable of providing a light reflective surface at the desired frequencies and can be deposited by PVD, CVD or ALD, depending on the material. In some embodiments, the ribbon-electrode layer can include a metal that provides a light reflective surface to enable it to also serve as the reflecting layer. After deposition of the mechanical layer, a ribbon-electrode layer, and reflective layer, a drive bus716is formed, electrically coupling each ribbon-electrode to a drive channel in a driver (not shown), integrally formed on the same substrate704with the compact SLM700. Next, the mechanical, electrode and reflective layers are patterned or rib-cut using standard photolithographic techniques and one or more etch steps to form the plurality of ribbons710including split-ribbon portions. It is noted that this patterning step exposes the first and second sacrificial layers708,714between the ribbons710and through openings in the split-ribbon portions facilitating subsequent removal of the underlying sacrificial layers.

Finally, the first and second sacrificial layers708,714are etched or removed using a noble gas fluoride, such Xenon difluoride (XeF2) to form a first air-gap (first air-gap902inFIG.9) between a dielectric layer712and a substrate-electrode702, and a second air-gap (second air-gap904inFIG.9) between the dielectric layer and a plurality of ribbons710, such that each of the plurality of ribbons are free to deflect towards the substrate-electrode upon application of a voltage potential between the substrate-electrode and the ribbon (step811).

Finally, first and second light reflective surfaces on the ribbons and exposed dielectric layer (step813). Generally, the reflective surfaces can include a reflective metal such as, aluminum (Al), gold (Au), or silver (Ag), or a multilayer Bragg mirror, deposited using CVD, PECVD, ALD of sputtering.

In another aspect the present invention is directed to a compact SLM having a single, tunable array of active ribbons to enable modulation of different wavelengths of light from a multi-wavelength light source or multiple single-wavelength light sources to form color images through sequential modulation or time multiplexing.FIG.10is a graph of intensity of normal-incidence (zero order) reflection from a compact SLM as a function of vertical offset between first, active light reflective surfaces on the active-ribbons and static light reflective surface for three different wavelengths of incident light, line1002represents blue light having a wavelength of about 450-495 nm, line1004represents green light having a wavelength of about 495-570, and line1006represents red light having a wavelength of about 630-700 nm. Referring toFIG.10, it is noted that any calibration scheme for three sequentially modulated colors requires a bright and dark rollover for every color. It is further noted that although this graph assumes operation of a compact SLM operated using the zero (0th) order, first (1st) order operation could be used with a half-wavelength shift from this graph. The graph also holds true for flat light valve operation in which the static light reflective surfaces are formed on passive ribbons always maintained in an undeflected or 0 position.

Referring toFIG.10it is noted the graph in shows two different ranges or windows of operation. In the leftmost window1008of operation, the non-actuated offset is set to 315 nanometers (nm), or just a little more for margin of error. Operation in this window1008can be combined with a minimum, actuated offset of 135 nm, so that a maximum actuation of 180 nm is all that is required to switch from fully on (bright) to fully off (dark) for any the colors illustrated. In particular, operating in this window1008it will be possible to modulate red light (line1006) from its second maximum to its first minimum and the same for green light (line1004), while blue light (line1002) will be modulated from its second minimum to its second maximum. The operation windows for the GLV shown inFIG.10are determined by ribbon-substrate distance when inactive and at maximum deflection. Generally, the required maximum deflection will be slightly bigger than a quarter of the longest wavelength, for a well-chosen gap.

In an alternative embodiment, to avoid the extra processing required to make a structured substrate, the compact SLM can include static reflective surfaces formed directly on a substantially planar surface of the substrate and can be operated in the right most window1010inFIG.10. In this case the non-actuated offset is set to about 675 nm. This should be combined with a minimum, actuated offset of 457.5 nm, so that we need an actuation of 217.5 nm. Red light (line1006) will then be possible to modulate from its third maximum to is second minimum, and green light (line1004) can be modulated from its third minimum to its third maximum, while blue light (line1002) will be modulated from its fourth maximum to its third minimum. The advantage of operating in window1008is that less actuation or deflection of the active-ribbons is needed. On the other hand, operating in window1010of not requiring structuring of the substrate.

FIG.11is a block diagram depicting a display system including a compact SLM having active-ribbons with split-ribbon portions, capable of being operated in a time multiplexed mode operation according to an embodiment of the present disclosure to provide a color display. It is note that the display system can include either a projector system or a head mounted unit (HMU). Where the display system is a HMU, the system can be or be included in a near eye display, such as glasses, goggles or helmet used in an augmented reality (AR), virtual reality (VR), mixed reality (MR) or cross reality (XR) system. Where the display system is a projector system, it can be a pico projector, pocket projector or mobile projector. Referring toFIG.11, the display system1100is coupled to an external computer to receive digital imaging data, and includes in addition to compact SLM1102a number of coherent light sources1104, such as lasers, illumination optics1106configured or operable to illuminate the compact SLM with light from the light sources, a driver1108configured to drive active-ribbons in the compact SLM to modulate light incident thereon, imaging optics1110configured or operable to spatially filter modulated light from the compact SLM, scanning the filtered modulated light along a second axis and project it onto an imaging plane to form a two-dimensional (2D) image thereon, and a controller1112to control operation of the light sources1104, driver1108, and a second axis scanner1114in the imaging optics1110.

Generally, the light sources1104can include multiple light sources, such as lasers, each generating a coherent light at a different wavelength, or a single light source or laser capable of sequentially generating coherent light at different wavelengths at different times. In one embodiment particularly useful for laser marking systems the coherent light sources1104are capable of operating in visible wavelength (λ) to generate blue, green and red light to provide a time multiplexed color image in the imaging plane.

The illumination optics1106is configured or operable to illuminate at least the split-ribbon portions of the active-ribbons in the compact SLM with a substantially rectangular swath or area of light.

Preferably, the compact SLM1102includes a multi-pixel, linear array of from about 10 to about 1088 individual active-ribbons, each including a split-ribbon portion. Generally, the compact SLM1102produces a substantially rectangular multi-pixel swath of modulated light that can be scanned along a second axis on the imaging plane to produce the 2D image thereon.

As noted above, the imaging optics1110includes a second axis scanner1114to scan the swath of modulated light along a second axis, typically perpendicular to the long axis of the swath of modulated light, to produce the 2D image. The second axis scanner1114can include dynamic optical elements, such as galvanometric mirrors, to scan the linear swath of modulated light across the surface of the workpiece, and a number of static optical elements to direct modulated light to the galvanometric mirrors and/or to focus the modulated light from the galvanometric mirrors onto the surface of the workpiece. Generally, as in the embodiment shown, the imaging optics1110further includes a spatial filter1116, such as a Fourier filter to select an order, such as a 0thorder, in the reflected, modulated light, and projection optics1118, such as one or more lenses, mirrors or prisms to focus the modulated and filtered light onto the imaging plane. In some embodiments, the second axis scanner1114may also function as the spatial filter1116.

FIGS.12A and12Bare block optic diagrams depicting folded illumination and secondary axis scanning for a display system1200suitable for use in projector and including a compact SLM1202having active-ribbons with split-ribbon portions, capable of being operated in a time multiplexed mode operation. In particular,FIG.12Aillustrates a side-view of the system, andFIG.12Billustrates a top-view of the display system1200.

Referring toFIGS.12A and12Bit is noted that the display system1200further multiple light sources1204, each generating a different wavelength or color designated here as R, G, and B for red, green and blue light, a fiber optic color combiner1206and sequenced by controller (not shown in this figure), illumination optics1208including a fast axis collimator1210and a spherical lens1212for sheet illumination onto the compact SLM1202, and a quarter wave polarizer1214in a beam splitter1216that rotates the sheet illumination onto the compact SLM. Imaging optics1217, shown in the figure ofFIG.12A, includes in addition to the beam splitter1216a second spherical lens1218, secondary axis scanning mirror or scanner1220, a third spherical lens1222, and projection optics1224to direct the light onto an imaging plane in a far-field or screen. In the embodiment shown the scanning mirror or scanner1220not only provides scanning along the second axis to form the 2D image, it also acts as a spatial filter to select the appropriate order of the reflected, modulate light. Typically, a 0thorder.

FIGS.13and14are optic diagrams near eye optics for an HMU or system including a compact SLM according to an embodiment of the present disclosure. In both figures the input light is amplitude modulated sheet scanned in an orthogonal direction.

FIG.13depicts projector optics for a projector system1300including a compact SLM1302. Referring toFIG.13, in addition to the compact SLM1302the projector system1300further includes projection optics1304including a first spherical lens1306aand a second spherical lens1306b. The additional spherical lens1306breforms the amplitude modulated image on an imaging plane in a far-field. Generally, the swath of modulated light from the compact SLM1302can be scanned in an orthogonal direction as shown in the top figure to form a 2D image.

FIG.14depicts optic diagrams for near eye optics in an HMU system1400. Referring toFIG.14it is noted that the focal lengths of a SLM1402in the system1400are chosen to create virtual image that is then formed onto a retina in a user's eye1404. Because the retina is directly conjugate to SLM1402of the HMU system1400, the image will appear to form at infinity, and can be scanned in an orthogonal direction as shown in the top figure.

FIG.15illustrates an embodiment of a HMU1500including glasses or goggles1502to be worn on the head of a user in which a compact display system is in a housing affixed to the glasses or goggles in various locations. Referring toFIG.15, in the embodiment shown the goggles1502include more than one housing, including housing1504a, affixed to a side arm of the glasses or goggles, while another (housing1504b) is affixed elsewhere on the body of the glasses or goggles, such as a point near the bridge thereof. It is noted that while multiple cameras enclosed in multiple housings1504a,1504b, are shown inFIG.15, a single display system enclosed in a single housing, either1504aor1504b, may be sufficient to depending on the application for which the HMU1500is being used. For example, for an augmented reality (AR) application it may be sufficient or even desirable that an image is presented into only one of the user's eyes. Alternatively, in some applications it may be desirable to have multiple cameras enclosed in multiple linked display systems, housed in one or more housings1504a,1504b, each positioned and configured or operable to present an image to a separate eye of the user to provide a more immersive experience, for example in a virtual reality (VR) application.

FIG.16is a flow chart of a method for operating a compact display system including a single MEMS-based SLM and calibrated to sequential modulate three separate wavelengths for a full color display. Referring toFIG.16, the method begins with providing a display system including multiple light sources each generating a coherent light at a different wavelength (or a single light source capable of sequentially generating coherent light at different wavelengths at different times), and a single, compact SLM tuned including a single, linear array of active-ribbons with split ribbon portions (step1602). Preferably, the linear array of the compact SLM is tuned modulate wavelengths from each of the multiple light sources using broadband tuning as described above with reference toFIG.10. Next, at a first time at least a portion of the linear array including the split ribbon portions is illuminated with a coherent light from one of the multiple light sources (step1604), and a driver including a number of drive channels operated to deflect one or more of the active-ribbons is towards the surface of the substrate to bring coherent light reflected from the active-ribbons into interference with light reflected from a static light reflective surface (step1606). Preferably, the driver is further operated to sequentially offset an amount by which the active-ribbons are driven depending on the wavelength of light being modulated. The modulated light is then spatially filtered to select the desired order of the reflected light, for example the 0th order, scanned along a second axis and projected onto an imaging plane (step1608). At a second or subsequent time the linear array is illuminated with a coherent light from another one of the multiple light sources and process repeated to provide time multiplexed color image in the imaging plane (step1610).

Thus, embodiments of high-contrast compact, compact SLM and display systems including the same have been disclosed. Embodiments of the present invention have been described above with the aid of functional and schematic block diagrams illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

It is to be understood that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.

The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.