WO2017196270A1

WO2017196270A1 - Scanning fiber microdisplay

Info

Publication number: WO2017196270A1
Application number: PCT/TR2016/050143
Authority: WO
Inventors: Hakan Urey
Original assignee: Cy Vision Inc.
Priority date: 2016-05-13
Filing date: 2016-05-13
Publication date: 2017-11-16

Abstract

The present invention relates to a microdisplay system in optical communication with at least one fiber optic cable (11) transmitting an optical signal, said fiber optic cable (11) having a flexibly deflectable distal extremity (18) around an anchor point (14) to create an image pixel in a certain position in a time-dependable manner at a free space intermediate image plane. The microdisplay system comprises a partial ellipsoid or freeform optical reflector (19) and light rays transmitted through said at least one fiber optic cable (11) are directable to an exit pupil plane (26) by means of the reflector (19).

Description

SCANNING FIBER MICRODISPLAY

Technical Field of the Present Invention

The present invention relates to a scanning fiber based microdisplay in the form of a free space optics image relaying system.

Background of the Present Invention

Head-worn displays (HWD) typically employ a microdisplay on which a two dimensional (2D) regular image is displayed. Since the physical distance between the microdisplay and the eye is typically much smaller than 25 cm (the closest distance at which the human eye can normally focus), a blurred image forms on the retina unless relay optics are placed in between. The relay optics typically consist of several lenses which serve to form a magnified virtual image of the microdisplay beyond 25 cm (mostly at infinity) on which the eye can then focus and form a sharp retinal image. Lightweight HWD designs that employ microdisplays (those that use only a single magnifier lens, for instance) are mostly restricted to systems having small fields of view (FOV), since weight and bulk increase for large FOV designs due to additional components inserted to compensate for aberrations. On the other hand, high end Military-type displays may support a FOV approaching 150 degrees or more, but can weigh more than 1kg and may contain more than 10 different lenses, most of which are present to compensate for aberrations that emerge due to the enlarged FOV. Having so many lenses is not merely a technological problem, but a fundamental one, since no single optical component can be designed to form an aberration free image of a large size microdisplay, due to the fact that the information emerging from the microdisplay quickly gets spread in space as it propagates.

The concept of scanning the light from a single optical fiber in vibratory resonance in the manner that the pixels of a scanning fiber endoscope (SFE) are acquired in an individually time-dependent manner is known since 2000 (Eric J. Seibel, Richard S. Johnston, C. David Melville, A full-color scanning fiber endoscope, Department of Mechanical Engineering and Human Interface Technology Laboratory, Optical Fibers and Sensors for Medical Diagnosis and Treatment Applications, Ed. I. Gannot, Proc. SPIE vol. 6083). The microscanner being located at the distal tip of the flexible endoscope, small scanner diameter is critical.

A scanning fiber endoscope provides that light is distributed through one single-mode fiber and a collector/detector subsystem is realized with several multi-mode fibers. Single Fiber Scanning Endoscopy (SFSE) technology enables the fabrication and utilization of devices that can be designed to advantageously have a pixel resolution, which is determined by the illumination area in the manner that the resolution of acquired image is not limited by the number of collectors/detectors. US20080058629A1 explains a SFSE system with a fiber that has several modes and that can be moved resonantly or non-resonantly. Therefore, optical fiber scope with both non- resonant illumination and resonant collection/imaging for multiple modes of operation is taught by the disclosure of US20080058629A1.

One of the prior art documents in the technical field of the present invention can be referred to as US5715337, disclosing a compact display system including a viewing surface; a beam steering mechanism; a source of light remote from the viewing surface and the beam steering mechanism; and at least one waveguide connecting the source of light with the viewing surface for transmitting illumination from the source of light to the viewing surface. The beam steering mechanism is associated with the waveguide and the viewing surface for scanning illumination transmitted by the waveguide onto the viewing surface. There is a modulator for modulating the source of light; and a subsystem for synchronizing the modulator with the beam steering mechanism, but only the distal end of the waveguide and the beam steering mechanism are located near the viewing surface resulting in a more compact display which can be mounted on a pair of eyeglasses. US 5715337 provides that only the distal end of the waveguide and the beam steering mechanism are located near the viewing surface resulting in a more compact display which can be mounted on a pair of eyeglasses.

The present invention, on the other hand, provides a microdisplay in the form of a free space optics image relaying system with at least one fiber optic cable deflectable to provide small emission spots as embodied in Claim 1 and claims dependent thereto.

Objects of the Present Invention

Primary object of the present invention is to provide a microdisplay in the form of a free space optics image relaying system.

Another object of the present invention is to provide a microdisplay having at least one fiber optic cable deflectable that is scanning to form an intermediate image plane.

Further an object of the present invention is to provide a microdisplay offering comfortable viewing with minimal hardware with a larger field of view and larger exit pupil size.

Still further an object of the present invention is to provide a microdisplay having at least one fiber optic cable deflectable to provide near-field focusing of light by which focused spots with sizes of 1 to 5 times the smallest light wavelength used in the system can be achieved and numerical aperture and resolution can be increased.

Still further an object of the present invention is to provide a microdisplay with a fiber bundle having a plurality of different length fiber optic cables by which a multi-depth display is realized.

Brief Description of the Figures of the Present Invention Accompanying drawings are given solely for the purpose of exemplifying a free space optics image relaying system from the tip of a scanning fiber to an exit pupil plane, whose advantages over prior art were outlined above and will be explained in brief hereinafter. The drawings are not meant to delimit the scope of protection as identified in the claims nor should they be referred to alone in an effort to interpret the scope identified in said claims without recourse to the technical disclosure in the description of the present invention. Fig. 1 demonstrates a general schematic view of a scanning fiber optic cable in the form of a free space optics image relaying system according to the present invention.

Fig. 2 demonstrates a general schematic view of a fiber optic cable with a cladding layer, tapered fiber tip and an additional metallic layer coated to the tapered fiber's distal extremity according to the present invention.

Fig. 3 demonstrates a general schematic view of a fiber optic cable in the form of a free space optics image relaying system with a partial ellipsoid reflector according to the present invention. The virtual anchor point of the movable fiber optic cable and user eye are respectively positioned on the two foci of the partial ellipsoid reflector on a major axis. Fig. 4 demonstrates a general schematic view of a fiber optic cable in the form of a free space optics image relaying system with a partial semi- transparent reflector using a flat or curved diffractive optical element according to the present invention. The virtual anchor point of the movable fiber optic cable and user eye are respectively positioned on the two foci of the partial ellipsoid reflector. The light emanating from the tip of the scanning fiber is illustrated in two different scan angles. The partial reflector surface forms an exit pupil plane, wherein a viewer's eyes can be placed to see a large field of view image. Fig. 5 demonstrates a general schematic view of a fiber bundle with a plurality of different length fiber optic cables according to the present invention. Fibers preferably have tapered tips and metallic layers coated thereto with an aperture at the tip to form a point light source with effective source size in the range 1 to 5 times the light wavelength. Fiber optic cables are longitudinally bundled to be movable around a common anchor point with different respective lengths from said common anchor point. Detailed Description of the Present Invention

The following numerals are used to refer to various parts and definitions in the detailed description of the present invention:

10) Fiber cantilever bending section

11) Fiber optic cable

12) Light source

13) Fiber deflection drive system

14) Anchor point

15) Virtual anchor point

16) Fiber core

17) Cladding layer

18) Distal extremity

19) Reflector

20) Tapered fiber tip

21) Metallic layer

22) Major Axis

23) First focal point

24) Second focal point

25) User eye

26) Exit pupil plane

27) Fiber bundle

28) Diffractive lens

29) Marginal rays

30) Aperture

Abbreviations used in the detailed description of the invention are listed below: NA) Numerical aperture

e) Exit pupil size

La ) Distance from fiber anchor plane to virtual anchor plane

) Distance from virtual anchor plane to an orthogonal projection point of the deflecting fiber tips onto a central line

Distance between different length fibers (relative distance between consecutive fiber tips)

Θ) Angle of the tangent to the fiber curve at the fiber tip

The present invention proposes a microdisplay in the form of a free space optics image relaying system by using a longitudinal fiber optic cable (11) whose flexibly movable distal extremity (18) transmits optical signals from a light source (12) that emits light, as will be delineated hereinafter.

A conventional fiber deflection drive system (13) is effective in creating an image on an image plane, said image plane being defined on the free space plane. The light from the light source (12) is guided through said fiber optic cable (11) so as to reach the distal extremity (18) thereof from where it is emitted toward a free space image plane. Said fiber optic cable's (11) distal extremity (18) is flexible to be deflected relative to an anchor point (14) and the bending section of fiber cantilever (10) moves in response to the actuation signal from the fiber deflection drive system (13). Typically, a modulator is operational such that the fiber deflection drive system (13) deflects light rays in synchronization with the modulation operation. Said fiber optic cable (11) extends in free space to create the free space image plane to be perceived as an image created on said image plane. The deflected motion of the fiber optic cable (11) causes the light to be scanned over said free space image plane. The fiber optic cable's (11) distal extremity (18) is imparted a deflective motion starting from its stationary anchor point (14). Therefore, the free space image plane is a spatial area of free space image pixels.

The fiber deflection drive system (13) typically deflects light in cooperation with a scan drive circuit in the manner that its operation is synchronized with the modulator, the latter in signal communication with a video signal processor and clock, whereupon a small area of emitted light is created on the free space image plane in a time-dependent manner. Rays of light therefore create an image pixel in the correct position and at the correct time at said free space image plane. The position of the emitted light spot for every instant in time generates one pixel of the image at a time. Video signal processor generating frame and line synchronization pulses and supplying the same to the clock circuit may receive video signals in either analog or digital form. The speed and required displacement of the fiber deflection drive system (13) are adjustable to enable high resolution multi- axis imaging. More precisely, different orientations of the distal extremity (18) of the fiber optic cable (11) in respective directions correspond to different deflection positions. Various embodiments for cantilever fiber deflection drive systems (13) available to the skilled worker are disclosed in US5715337A. The cantilever can conventionally rely on energization by electrostatic, piezoelectric, or magnetic means. For a color image, three component colors should be separately modulated and combined in the fiber optic cable (13). Fiber deflection drive system (13) can be controlled to create a scan pattern in the form of a 2D raster, lissajous pattern, or concentric circles or a spiral pattern. The fiber deflection drive system (13) can be mounted to a frame portion of a head-mountable device within the housing thereof. According to the present invention, the head-mountable device comprises a free space optics image relaying system with a preferably partial (or semi-transparent) and ellipsoid reflector (19) such that light rays transmitted through said fiber optic cable (11) are directed to a user eye (25) by said partial ellipsoid reflector (19) while the outer distal extremity (18) of the movable single-mode optical fiber produces an intermediate image. The present invention provides that while the user eye's (25) position is structurally adapted to be located at one of the focal points (second focal point 24) of the ellipsoid shaped reflector (partial ellipsoid reflector (19)), a virtual anchor point (15) of the fiber optic cable (11) is configured to be positioned at the first focal point (23) of the partial ellipsoid reflector (19). In a more specific manner, the virtual anchor point (15) of the fiber optic cable (11) is an optical conjugate of the viewing box (exit pupil) of the user eye (25). The chief ray corresponding to the light emanating from the tip of the fiber can be traced back to the virtual anchor point (15) of the fiber optic cable (11). Light propagates towards the user's eye (25) and forms a light wave distribution on the exit pupil plane (26), which is defined as the plane that lies just in front of the user's eye (25).

It is to be noted that the advantageous effect by the ellipsoid reflector (19) according to the preferred embodiment of the invention can also be obtained by non-ellipsoid and general freeform surfaces so as to provide that the virtual anchor point (15) of the fiber optic cable (11) is an optical conjugate of the viewing box (exit pupil) of the user eye (25). A general optical relay or imaging from the virtual anchor point to an exit pupil plane (26) or to a viewer's pupil plane is sufficient to create a near-to-eye display system. The optical relay can be achieved using a refractive lens, reflective mirror, diffractive reflector (diffractive lens 28, representatively shown), or a combination thereof. Such a relay can also be achieved using substrate- guided optical relays employing stack of prisms with proper coatings, wedge prisms based on total partial internal reflection, or holographic reflectors and combiners. The relay optics should be designed to minimize the aberrations within a useful portion of the exit pupil, which is typically 2-4 mm in diameter, and within the central (or foveal) section of the field-of-view for a particular viewing direction. This corresponds to a small portion of the NA of the optical beam emanating from the fiber optic cable (11). In accordance with the present invention, a large exit pupil can be created by way of configuring said fiber optic cable (11) with a smaller diameter fiber core (16) and an additional distal end element as will be delineated below. To this end, the numerical aperture (NA) is increased by using the focused ion beam (FIB) technique by which the distal extremities (18) of the fiber optic cables (11) are processed to obtain a tapered fiber tip (20) optical cable with an additional metallic element and an optical aperture (30). According to the present invention, a thin metallic layer (21) is coated to the tapered fiber's distal extremity (18). FIB is a process for patterning, or cross-sectioning a fiber tip and can be used to form a sub-micron sized aperture (30).

As is known to the skilled worker, Near Field Scanning Optical Microscopy (NSOM) is a technique by which imaging of features smaller than λ/2 is possible. In the field of optoelectronics, the FIB can be utilized as a machining tool to fabricate micro-optical components such as the end facet mirrors, ring resonators, gratings and photonic crystals (Hopman, W. C. L, Ay, F. & Ridder, R. M. d. (2008). Focused ion beam milling strategy for sub- micrometer holes in silicon; Workshop FIB for Photonics, Eindhoven, the Netherlands). According to the present invention, the metallic layer (21) coated to the tapered fiber tip (20) provides a small aperture (30) that creates a point light source with size in the order of 0.2 to 5 times the light wavelength (i.e., 100 nm to 2.5 micrometer diameter assuming light wavelength is 500nm). The profile of the aperture (30) can be circular, elliptical, or other shape and the light emanating from the aperture (30) can have uniform or Gaussian beam profile across the aperture (30). While point light source size of smaller than the wavelength is possible, it is not practical when there is an optical relay present after the point light source. NA of the beam from a small aperture (30) is inversely proportional to the aperture size and already approach to a maximum value of 1.0 if the aperture size and the point light source size is approximately equal to one wavelength. Scanning fiber tip creates a free space image plane with a virtual anchor point (15) overlapping on the focal point proximate said partial ellipsoid reflector (19) in the manner that moving said fiber optic cable (11) causes light to bounce from said partial ellipsoid reflector (19) and form a viewing box at the exit pupil plane (26). The virtual anchor point (15) is defined as the projected intersection point of rays around the tilt angle of the fiber tip at the distal extremity (18) of said at least one fiber optic cable (11), as demonstrated in Fig. 1. The tilt angle of the fiber tip is defined as the angle of the tangent to the deflected fiber curve at the fiber tip. The near field focusing of light affords sub-wavelength focused spots across the intermediate image plane, thereby substantially effective in increasing the resolution or the number of resolvable spots across the scan trajectory.

A user wearing a frame structure to which the microdisplay of the invention is coupled is provided with a compact system capable of a large field of view (FOV) and high spatial resolution in front of the eyes of the user. The present invention provides that the numerical aperture (NA) is increased from around 0,1 radian to at least around 0,5 radian, by which a proportionally equal increase in the number of pixels is ensured. The increase in the numerical aperture (NA) is a result of said metallic layer (21) coated to the tapered fiber tip (20) and the aperture (30) at the tip of the fiber optic cable (11).

In a variation, the partial ellipsoid reflector (19) can be designed as a flat component such as a Fresnel reflector or diffractive reflector, which is advantageous for more compact space usage purposes as illustrated in Fig. 4. The diffractive reflector can be reflective or partially reflective. A beam splitter or additional lens elements can be used between the tip of the fiber optic cable (11) and the ellipsoid reflector (19) or diffractive reflector to allow for different placement of the components with respect to the viewer. Marginal rays (29) are collimated or slightly diverging upon reflection from the ellipsoid reflector (19) or diffractive reflector and form an exit pupil plane (26) where a user eye (25) can be placed. If marginal rays (29) are collimated, the tip of the fiber optic cable (11) appears at infinity to a user eye (25). If marginal rays (29) are diverging, the tip of the fiber optic cable (11) appears at the intersection of the extension of the marginal rays (29) to a user eye (25). Exit pupil size (e) is determined by the numerical aperture (NA) and the marginal rays (29). The tip of the fiber bundle (27) can be angle cleaved to bend the chief ray and the marginal rays (29) in a way similar to a prismatic element. Angle cleaving the fiber tip changes the illuminated region on the ellipsoid reflector (19) or diffractive reflector due to tilt of the ray bundle. In a preferred embodiment, the exit pupil plane (26) and the user eye (25) pupil are substantially overlapping.

In a further variation of the present invention, a fiber bundle (27) with a plurality of different length fiber optic cables (11) having tapered tips (20) and associated metallic layers (21) coated thereto is provided. Fiber optic cables (11) can be longitudinally bundled (for instance hexagonally) to be movable around a common anchor point (14) with different respective lengths from said common anchor point (14) to the distal extremities (18) thereof, as demonstrated in Fig. 5. More specifically, individual fiber optic cables (11) are fixedly joined to each other to be integrally deflectable and driven at the same operational frequency to create an intermediate plane image. The configuration with different length fiber optic cables (11) advantageously provides a multiple-depth image formation. While one fiber optic cable form an image at infinity (i.e., marginal rays (29) emanating from the fiber tip are collimated), longer fiber optic cables (11) in the fixedly joint arrangement form images at different virtual image distances. The image distance is determined by intersection of the extension of the marginal rays (29) to a user eye (25). Varied length of individual fibers from a common anchor point (14) is preferably configured to have at least four different length variations in accordance with the dioptric range of a human eye. All fibers separately connected to RGB modulators, when combined, provide the depth information with respect to a given pixel of the created image.

In a further variation of the present invention, a beam splitter or additional lens elements are used between the ellipsoid reflector (19) and the exit pupil plane (26).

In a further variation, the fiber optic cable (11) is operated in a higher order vibration mode, preferably in third order mode. For higher order modes, the virtual anchor point (15) is closer to the distal end and larger scan angles can be obtained. As a result, larger field-of-view can be obtained for the display system. In higher order modes, the length of the arc drawn by the tip of the fiber optic cable (11) is shorter; however, high resolution (i.e., number of resolvable spots across the scan line) can be maintained by keeping the emission spot size by using an aperture (30) or metal-coated tips as described above.

In a further variation of the present invention, different vibration modes of the fiber optic cable (11) can be excited simultaneously. 2D scanning and image formation is possible by exciting orthogonal vibration modes. 2D and 3D image patterns can be formed in air by controlling the vibration modes. This requires transformation and interpolation of the pixel data based on the location of the fiber tip as a function of time. In a preferred embodiment, concentric circular or concentric ellipsoid scan patterns are easily achievable by exciting two modes simultaneously and by changing the vibration amplitudes in each axis with time.

In a nutshell, the present invention proposes a microdisplay device comprising at least one fiber optic cable (11) transmitting an optical signal, said fiber optic cable (11) having an anchor point (14) and a flexibly deflectable distal extremity (18) movable to create an image pixel in a certain position in a time-dependable manner at a free space intermediate image plane.

In one embodiment of the present invention, the microdisplay device comprises a reflector (19) and light rays transmitted through said at least one fiber optic cable (11) are directable to an exit pupil plane (26) by means of the reflector (19) in the manner that a virtual anchor point (15) of the fiber optic cable (11) is configured to be positioned at a first position to illuminate said reflector (19) and said exit pupil plane (26) is structurally disposed to receive light from the first position after reflection from the reflector.

In a further embodiment of the present invention, said virtual anchor point (15) of the at least one fiber optic cable (11) is an optical conjugate of at least one point overlapping said exit pupil plane (26).

In a further embodiment of the present invention, said virtual anchor point (15) of the fiber optic cable (11) is configured to be positioned at a first focal point (23) of the reflector (19) and said exit pupil plane (26) is structurally disposed to be coincident with a second focal point (24) of the reflector (19).

In a further embodiment of the present invention, a beam splitter is placed between the fiber optic cable (11) and reflector (19).

In a further embodiment of the present invention, a beam splitter is placed between reflector (19) and exit pupil plane (26). In a further embodiment of the present invention, said reflector (19) is an ellipsoid reflector (19).

In a further embodiment of the present invention, said fiber optic cable (11) is operated in fundamental resonant mode.

In a further embodiment of the present invention, said fiber optic cable (11) is operated in a high order resonant mode such that the virtual anchor point (15) is close to the distal extremity (18). In a further embodiment of the present invention, said fiber optic cable (11) is operated in at least two vibration modes simultaneously.

In a further embodiment of the present invention, said at least one fiber optic cable (11) is a single-mode optical fiber. In a further embodiment of the present invention, distal extremity (18) of the at least one fiber optic cable (11) is processed to have a tapered fiber tip (20).

In a further embodiment of the present invention, a metallic layer (21) is coated to the tapered fiber tip (20) at the distal extremity (18) of said at least one fiber optic cable (11). In a further embodiment of the present invention, an aperture (30) is formed at the tapered fiber tip (20) at the distal extremity (18) of said at least one fiber optic cable (11).

In a further embodiment of the present invention, said virtual anchor point is defined as the projected intersection point of rays around the tilt angle of the fiber tip at the distal extremity (18) of said at least one fiber optic cable (11).

In a further embodiment of the present invention, said microdisplay device comprise a fiber bundle (27) with a plurality of different length fiber optic cables (11) having tapered tips and associated metallic layers (21) coated thereto.

In a further embodiment of the present invention, said fiber optic cables (11) are longitudinally bundled to be movable around a common anchor point (14) with different respective lengths from said common anchor point (14) to the distal extremities (18) thereof.

In a further embodiment of the present invention, said different length fiber optic cables (11) are fixedly joined to each other to be integrally deflectable and driven at the same operational frequency to provide a multiple-depth intermediate plane image formation.

In a further embodiment of the present invention, varied length of fiber optic cables (11) from said common anchor point (14) is configured to have at least four different length variations.

In a further embodiment of the present invention, different length fiber optic cables (11) are separately connected to red green and blue (RGB) light sources.

In a further embodiment of the present invention, the reflector (19) is realized by a flat component in the form of a Fresnel zone plate, Fresnel reflector or diffractive reflector.

In a further embodiment of the present invention, the reflector (19) is a partial ellipsoid reflector.

In a further embodiment of the present invention, the aperture (30) is configured as a sub-wavelength size nanospot so as to function as focus spot generation means.

In a further embodiment of the present invention, said aperture (30) forming a point light source has an effective source size in the range 0.2 to 5 times the light wavelength.

In a further embodiment of the present invention, the aperture (30) profile is in a shape in the manner that the light emanating therefrom has uniform or Gaussian beam profile across said aperture (30). In a further embodiment of the present invention, the aperture (30) profile is circular or ellipsoid. In a further embodiment of the present invention, the diffractive reflector is reflective or partially reflective.

In a further embodiment of the present invention, a beam splitter or additional lens elements are used between the tip of the fiber optic cable (11) and the ellipsoid reflector (19) or diffractive reflector.

In a further embodiment of the present invention, the tip of the fiber optic cable (11) is angle cleaved to bend the chief ray and marginal rays (29). In a further embodiment of the present invention, a head-mountable display device comprising a microdisplay device is proposed.

A particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the scope of the invention. In addition, it is to be noted that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the scope of the invention. The detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims to be interpreted along with the full range of equivalents to which the claims are entitled.

Claims

1) A microdisplay device comprising at least one fiber optic cable (11) transmitting an optical signal, said fiber optic cable (11) having an anchor point (14) and a flexibly deflectable distal extremity (18) movable to create an image pixel in a certain position in a time-dependable manner at a free space intermediate image plane characterized in that;

the microdisplay device comprises a reflector (19) and light rays transmitted through said at least one fiber optic cable (11) are directable to an exit pupil plane (26) by means of the reflector (19) in the manner that a virtual anchor point (15) of the fiber optic cable (11) is configured to be positioned at a first position to illuminate said reflector (19) and said exit pupil plane (26) is structurally disposed to receive light from the first position after reflection from the reflector (19).

2) A microdisplay device as set forth in Claim 1, characterized in that said virtual anchor point (15) of the at least one fiber optic cable (11) is an optical conjugate of at least one point overlapping said exit pupil plane (26).

3) A microdisplay device as set forth in Claim 2, characterized in that said virtual anchor point (15) of the fiber optic cable (11) is configured to be positioned at a first focal point (23) of the reflector (19) and said exit pupil plane (26) is structurally disposed to be coincident with a second focal point (24) of the reflector (19).

4) A microdisplay device as set forth in Claim 1, characterized in that a beam splitter is placed between the fiber optic cable (11) and reflector (19). 5) A microdisplay device as set forth in Claim 1 or 4, characterized in that a beam splitter is placed between reflector (19) and exit pupil plane (26). 6) A microdisplay device as set forth in Claim 1, 2 or 3, characterized in that said reflector (19) is a freeform optical surface.

7) A microdisplay device as set forth in Claim 1, 4, 5 or 6, characterized in that said fiber optic cable (11) is operated in fundamental resonant mode.

8) A microdisplay device as set forth in Claim 1, 4, 5 or 6, characterized in that said fiber optic cable (11) is operated in a high order resonant mode such that the virtual anchor point (15) is close to the distal extremity (18). 9) A microdisplay device as set forth in Claim 1, 4, 5 or 6, characterized in that said fiber optic cable (11) is operated in at least two vibration modes simultaneously.

10) A microdisplay device as set forth in Claim 1, 4, 5, 6, 7, 8 or 9, characterized in that said at least one fiber optic cable (11) is a single- mode optical fiber.

11) A microdisplay device as set forth in Claim 1, 4, 5, 6, 7, 8 or 9, characterized in that distal extremity (18) of the at least one fiber optic cable (11) is processed to have a tapered fiber tip.

12) A microdisplay device as set forth in Claim 11, characterized in that a metallic layer (21) is coated to the tapered fiber tip (20) at the distal extremity (18) of said at least one fiber optic cable (11). 13) A microdisplay device as set forth in Claim 11 or 12, characterized in that an aperture (30) is formed at the tapered fiber tip (20) at the distal extremity (18) of said at least one fiber optic cable (11).

14) A microdisplay device as set forth in Claim 12 or 13, characterized in that said virtual anchor point (15) is defined as the projected intersection point of rays around the tilt angle of the fiber tip at the distal extremity (18) of said at least one fiber optic cable (11).

15) A microdisplay device as set forth in Claim 14, characterized in that said microdisplay device comprise a fiber bundle (27) with a plurality of different length fiber optic cables (11) having tapered tips and associated metallic layers (21) coated thereto.

16) A microdisplay device as set forth in Claim 15, characterized in that said fiber optic cables (11) are longitudinally bundled to be movable around a common anchor point (14) with different respective lengths from said common anchor point (14) to the distal extremities (18) thereof.

17) A microdisplay device as set forth in Claim 15 or 16, characterized in that said different length fiber optic cables (11) are fixedly joined to each other to be integrally deflectable and driven at the same operational frequency to provide a multiple-depth intermediate plane image formation.

18) A microdisplay device as set forth in Claim 16, characterized in that varied length of fiber optic cables (11) from said common anchor point (14) is configured to have at least four different length variations. 19) A microdisplay device as set forth in Claim 17 or 18, characterized in that different length fiber optic cables (11) are separately connected to red, green and blue (RGB) light sources. 20) A microdisplay device as set forth in Claim 1, characterized in that the reflector (19) is realized by a flat component in the form of a Fresnel zone plate, Fresnel reflector or diffractive reflector.

21) A microdisplay device as set forth in Claim 1, characterized in that the reflector (19) is a partial ellipsoid reflector.

22) A microdisplay device as set forth in Claim 13, characterized in that the aperture (30) is configured as a 1 to 5 times the wavelength size. 23) A microdisplay device as set forth in Claim 22, characterized in that said aperture (30) forming a point light source has an effective source size in the range 1 to 5 times the light wavelength.

24) A microdisplay device as set forth in Claim 22 or 23, characterized in that the aperture (30) profile is in a shape in the manner that the light emanating therefrom has uniform or Gaussian beam profile across said aperture (30).

25) A microdisplay device as set forth in Claim 24, characterized in that the aperture (30) profile is circular or rectangular.

26) A microdisplay device as set forth in Claim 20, characterized in that the diffractive reflector is reflective or partially reflective. 27) A microdisplay device as set forth in Claim 20 or 26, characterized in that a beam splitter or lens elements are used between the tip of the fiber optic cable (11) and the ellipsoid reflector (19) or diffractive reflector. 28) A microdisplay device as set forth in Claim 11, 12 or 13, characterized in that the tip of the fiber optic cable (11) is angle cleaved to bend the chief ray and marginal rays (29).

29) A microdisplay device as set forth in Claim 1, 2 or 3, characterized in that said reflector (19) is a substrate-guided optical relay.

30) A head-mountable display device comprising a microdisplay device as set forth in any preceding Claim.