WO2022178406A1 - Dispositif d'affichage comprenant un réseau de microlentilles à polarisation sélective - Google Patents

Dispositif d'affichage comprenant un réseau de microlentilles à polarisation sélective Download PDF

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Publication number
WO2022178406A1
WO2022178406A1 PCT/US2022/017273 US2022017273W WO2022178406A1 WO 2022178406 A1 WO2022178406 A1 WO 2022178406A1 US 2022017273 W US2022017273 W US 2022017273W WO 2022178406 A1 WO2022178406 A1 WO 2022178406A1
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WO
WIPO (PCT)
Prior art keywords
light
polarized light
microlens
microlens array
polarization
Prior art date
Application number
PCT/US2022/017273
Other languages
English (en)
Inventor
Stefanie Taushanoff
Hyunmin SONG
Fenglin Peng
Yun-Han Lee
Mengfei WANG
Sanaz ALALI
Chia-Hsuan Tai
Junren WANG
Original Assignee
Meta Platforms Technologies, Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US17/541,232 external-priority patent/US20220269092A1/en
Application filed by Meta Platforms Technologies, Llc filed Critical Meta Platforms Technologies, Llc
Publication of WO2022178406A1 publication Critical patent/WO2022178406A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C7/00—Optical parts
    • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
    • G02C7/08—Auxiliary lenses; Arrangements for varying focal length
    • G02C7/086—Auxiliary lenses located directly on a main spectacle lens or in the immediate vicinity of main spectacles
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133526—Lenses, e.g. microlenses or Fresnel lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/13362—Illuminating devices providing polarized light, e.g. by converting a polarisation component into another one
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/294—Variable focal length devices

Definitions

  • the present disclosure generally relates to optical devices and, more specifically, to a display device including a polarization selective microlens array.
  • Non-emissive displays such as liquid crystal displays (“LCDs”), liquid-crystal-on-silicon (“LCoS”) displays, or digital light processing (“DLP”) displays, may require a backlight unit to illuminate a display panel. LCDs are attractive candidates for transparent displays and high luminance displays. Self-emissive displays may display images through emitting lights with different intensities and colors from light-emitting elements.
  • Self-emissive displays may also function as a locally dimmable backlight unit for LCDs having a highly dynamic range.
  • Self-emissive displays such as organic light-emitting diode (“OLED”) displays
  • OLED organic light-emitting diode
  • An OLED display can provide a high power efficiency, a superior dark state, a thin thickness, and a freeform factor, and has been widely used in TVs and smartphones.
  • Emerging self-emissive displays such as micro organic light-emitting diode (“pOLED”) displays, micro light-emitting diode (“pLED”) displays, mini-LED (“mLED”) displays, are promising technologies for next-generation displays. These displays offer ultra-high luminance and long lifetimes, which are highly desirable for sunlight readable displays, such as smartphones, public information displays, and vehicle displays.
  • the device includes a light source configured to output a light.
  • the device also includes a display panel including a plurality of subpixel areas.
  • the device also includes a microlens assembly disposed between the light source and the display panel.
  • the microlens assembly includes a first microlens array configured to substantially collimate the light into a first polarized light, and a second microlens array configured to focus the first polarized light as a second polarized light propagating through apertures of the subpixel areas.
  • the second polarized light may propagate substantially entirely through the apertures of the subpixel areas.
  • the display panel may include a plurality of color filters, and wherein the second polarized light propagates substantially entirely through the color filters.
  • the first microlens array may be a first Pancharatnam Berry Phase (“PBP”) microlens array
  • the second microlens array is a second PBP microlens array.
  • PBP Pancharatnam Berry Phase
  • each subpixel area of the plurality of subpixel areas may include a subpixel electrode and a switching element of the subpixel electrode, the subpixel electrode corresponding to an aperture of the subpixel area, and the switching element corresponding to a non-transparent portion of the subpixel area.
  • the first polarized light and the second polarized light may be circularly polarized lights having opposite handednesses.
  • the light output from the light source may be a circularly polarized light.
  • an alignment offset between the first or second microlens array and an array formed by the apertures of the subpixel regions may be less than or equal to 2 pm.
  • the first polarized light may have a collimation angle that is within a range of about 5° to about 15°.
  • the microlens assembly may include a waveplate disposed between the second microlens array and the display panel.
  • the microlens assembly may include a reflective polarizer disposed between the waveplate and the display panel, and a linear polarizer disposed between the reflective polarizer and the display panel.
  • the device includes a plurality of light-emitting elements configured to emit an image light.
  • the device also includes a polarization converter including a plurality of converting regions and non converting regions.
  • the device further includes a microlens array disposed between the light- emitting elements and the polarization converter.
  • the microlens array includes a plurality of microlenses configured to transform a first portion of the image light as a first polarized light that is incident onto the converting regions, and transform a second portion of the image light as a second polarized light that is incident onto both of the converting regions and the non converting regions.
  • the microlens array may include a transmissive polarization volume hologram (“PVH”) microlens array.
  • PVH transmissive polarization volume hologram
  • the microlenses may include a plurality of central portions and periphery portions, the first portion of the image light includes portions of the image light that are incident onto central portions of the microlenses and that are circularly polarized with a first handedness, and the second portion of the image light includes a combination of portions of the image light that are incident onto the central portions of the microlenses and that are circularly polarized with a second handedness, and portions of the image light that are incident onto the periphery portions of the microlenses.
  • a beam size of the first polarized light at a plane intersecting one of the converting regions may be configured to be the same as or smaller than a size of the one of the converting regions.
  • an alignment offset between the microlens array and the light-emitting elements may be less than or equal to 2 pm.
  • the first polarized light may have a first polarization
  • the second polarized light has a second polarization that is orthogonal to the first polarization.
  • the second polarized light may include first portions incident onto the converting regions and second portions incident onto the non-converting regions, the converting regions are configured to convert the first polarized light having the first polarization into a third polarized light having the second polarization, and convert the first portions of the second polarized light having the second polarization into a fourth polarized light having the first polarization, and the non-converting regions are configured to transmit the second portions of the second polarized light having the second polarization as a fifth polarized light having the second polarization.
  • the device may further comprise a circular polarizer configured to substantially transmit the third polarized light having the second polarization and the fifth polarized light having the second polarization, and substantially block the fourth polarized light having the first polarization.
  • the circular polarizer may include a first waveplate, a linear polarizer, and a second waveplate stacked together.
  • FIG. 1A schematically illustrates a display device, according to an embodiment of the present disclosure
  • FIG. IB schematically illustrates a thin-film transistor (“TFT”) array substrate that may be included in the display device shown in FIG. 1 A, according to an embodiment of the present disclosure
  • FIG. 1C schematically illustrates a color filter substate that may be included in the display device shown in FIG. 1A, according to an embodiment of the present disclosure
  • FIG. ID schematically illustrates an optical path of a backlight in the display device shown in FIG. 1 A, according to an embodiment of the present disclosure
  • FIG. IE schematically illustrates a beam spot of a backlight at a plane intersecting a subpixel area of the display device shown in FIG. 1 A, according to an embodiment of the present disclosure
  • FIG. IF schematically illustrates a beam spot of a backlight at a plane intersecting a color filter of the display device shown in FIG. 1 A, according to an embodiment of the present disclosure
  • FIG. 1G schematically illustrates a display device, according to an embodiment of the present disclosure
  • FIG. 1H schematically illustrates an optical path of a backlight in the display device shown in FIG. 1G, according to an embodiment of the present disclosure
  • FIG. 2 schematically illustrates an optical path of a backlight in a conventional non-emissive display device
  • FIGs. 3A and 3B schematically illustrate in-plane orientations of optically anisotropic molecules included in a Pancharatnam Berry Phase (“PBP”) microlens, according to an embodiment of the present disclosure
  • FIGs. 3C and 3D schematically illustrate polarization selective focusing/defocusing of the PBP microlens shown in FIGs. 3A and 3B, according to an embodiment of the present disclosure
  • FIG. 4A schematically illustrates a display device, according to an embodiment of the present disclosure
  • FIG. 4B schematically illustrates an optical path of one of two orthogonally circularly polarized components of an image light in the display device shown in 4A, according to an embodiment of the present disclosure
  • FIG. 4C schematically illustrates an optical path of the other one of two orthogonally circularly polarized components of the image light in the display device shown in 4A, according to an embodiment of the present disclosure
  • FIG. 4D schematically illustrates a display device, according to an embodiment of the present disclosure
  • FIGs. 5A-5C schematically illustrate polarization selective diffractions of a polarization volume hologram (“PVH”) microlens, according to an embodiment of the present disclosure
  • FIG. 6 schematically illustrates an optical path of an image light in a conventional emissive display device
  • FIG. 7A illustrates a schematic diagram of a near-eye display (“NED”), according to an embodiment of the present disclosure
  • FIG. 7B illustrates a schematic cross sectional view of half of the NED shown in FIG. 7A, according to an embodiment of the present disclosure
  • FIG. 8A schematically illustrates a diagram of an optical system, according to an embodiment of the present disclosure.
  • FIG. 8B schematically illustrates a cross-sectional view of an optical path of an image light propagating through the optical system shown in FIG. 8A, according to an embodiment of the present disclosure.
  • the disclosed embodiments and the features of the disclosed embodiments may be combined.
  • the described embodiments are some but not all of the embodiments of the present disclosure.
  • persons of ordinary skill in the art may derive other embodiments consistent with the present disclosure.
  • modifications, adaptations, substitutions, additions, or other variations may be made based on the disclosed embodiments.
  • Such variations of the disclosed embodiments are still within the scope of the present disclosure. Accordingly, the present disclosure is not limited to the disclosed embodiments. Instead, the scope of the present disclosure is defined by the appended claims.
  • the terms “couple,” “coupled,” “coupling,” or the like may encompass an optical coupling, a mechanical coupling, an electrical coupling, an electromagnetic coupling, or any combination thereof.
  • An “optical coupling” between two optical elements refers to a configuration in which the two optical elements are arranged in an optical series, and a light output from one optical element may be directly or indirectly received by the other optical element.
  • An optical series refers to optical positioning of a plurality of optical elements in a light path, such that a light output from one optical element may be transmitted, reflected, diffracted, converted, modified, or otherwise processed or manipulated by one or more of other optical elements.
  • the sequence in which the plurality of optical elements are arranged may or may not affect an overall output of the plurality of optical elements.
  • a coupling may be a direct coupling or an indirect coupling (e.g., coupling through an intermediate element).
  • the phrase “at least one of A or B” may encompass all combinations of A and B, such as A only, B only, or A and B.
  • the phrase “at least one of A, B, or C” may encompass all combinations of A, B, and C, such as A only, B only, C only, A and B, A and C, B and C, or A and B and C.
  • the phrase “A and/or B” may be interpreted in a manner similar to that of the phrase “at least one of A or B.”
  • the phrase “A and/or B” may encompass all combinations of A and B, such as A only, B only, or A and B.
  • phrase “A, B, and/or C” has a meaning similar to that of the phrase “at least one of A, B, or C.”
  • the phrase “A, B, and/or C” may encompass all combinations of A, B, and C, such as A only, B only, C only, A and B, A and C, B and C, or A and B and C.
  • first element When a first element is described as “attached,” “provided,” “formed,” “affixed,” “mounted,” “secured,” “connected,” “bonded,” “recorded,” or “disposed,” to, on, at, or at least partially in a second element, the first element may be “attached,” “provided,”
  • first element may be in direct contact with the second element, or there may be an intermediate element between the first element and the second element.
  • the first element may be disposed at any suitable side of the second element, such as left, right, front, back, top, or bottom.
  • first element When the first element is shown or described as being disposed or arranged “on” the second element, term “on” is merely used to indicate an example relative orientation between the first element and the second element. The description may be based on a reference coordinate system shown in a figure, or may be based on a current view or example configuration shown in a figure. For example, when a view shown in a figure is described, the first element may be described as being disposed “on” the second element. It is understood that the term “on” may not necessarily imply that the first element is over the second element in the vertical, gravitational direction.
  • the first element when the assembly of the first element and the second element is turned 180 degrees, the first element may be “under” the second element (or the second element may be “on” the first element).
  • the configuration is merely an illustrative example.
  • the first element may be disposed or arranged at any suitable orientation relative to the second element (e.g., over or above the second element, below or under the second element, left to the second element, right to the second element, behind the second element, in front of the second element, etc.).
  • the first element When the first element is described as being disposed “on” the second element, the first element may be directly or indirectly disposed on the second element.
  • the first element being directly disposed on the second element indicates that no additional element is disposed between the first element and the second element.
  • the first element being indirectly disposed on the second element indicates that one or more additional elements are disposed between the first element and the second element.
  • processor used herein may encompass any suitable processor, such as a central processing unit (“CPU”), a graphics processing unit (“GPU”), an application- specific integrated circuit (“ASIC”), a programmable logic device (“PLD”), or any combination thereof. Other processors not listed above may also be used.
  • a processor may be implemented as software, hardware, firmware, or any combination thereof.
  • controller may encompass any suitable electrical circuit, software, or processor configured to generate a control signal for controlling a device, a circuit, an optical element, etc.
  • a “controller” may be implemented as software, hardware, firmware, or any combination thereof.
  • a controller may include a processor, or may be included as a part of a processor.
  • non-transitory computer-readable medium may encompass any suitable medium for storing, transferring, communicating, broadcasting, or transmitting data, signal, or information.
  • the non-transitory computer-readable medium may include a memory, a hard disk, a magnetic disk, an optical disk, a tape, etc.
  • the memory may include a read-only memory (“ROM”), a random-access memory (“RAM”), a flash memory, etc.
  • film may include rigid or flexible, self- supporting or free-standing film, layer, coating, or plate, which may be disposed on a supporting substrate or between substrates.
  • film may be interchangeable.
  • in-plane direction refers to a direction, an orientation, a rotation, an alignment pattern, and a pitch in a plane of a film or a layer (e.g., a surface plane of the film or layer, or a plane parallel to the surface plane of the film or layer), respectively.
  • the term “out-of-plane direction” or “out-of-plane orientation” indicates a direction or orientation that is non-parallel to the plane of the film or layer (e.g., perpendicular to the surface plane of the film or layer, e.g., perpendicular to a plane parallel to the surface plane).
  • an “in-plane” direction or orientation refers to a direction or orientation within a surface plane
  • an “out-of-plane” direction or orientation may refer to a thickness direction or orientation perpendicular to the surface plane, or a direction or orientation that is not parallel with the surface plane.
  • orthogonal polarizations or the term “orthogonally” as used in “orthogonally polarized” means that an inner product of two vectors representing the two polarizations is substantially zero.
  • two lights with orthogonal polarizations or two orthogonally polarized lights may be two linearly polarized lights with polarizations in two orthogonal directions (e.g., an x-axis direction and ay-axis direction in a Cartesian coordinate system) or two circularly polarized lights with opposite handednesses (e.g., a left-handed circularly polarized light and a right-handed circularly polarized light).
  • an angle of a beam (e.g., a diffraction angle of a diffracted beam or an incidence angle of an incident beam) with respect to a normal of a surface can be defined as a positive angle or a negative angle, depending on the angular relationship between a propagating direction of the beam and the normal of the surface.
  • the angle of the propagating direction may be defined as a positive angle
  • the angle of the propagating direction may be defined as a negative angle.
  • substantially or “primarily” used to modify an optical response action, such as “transmit,” “reflect,” “diffract,” “block” or the like that describes processing of a light means that a majority portion, including all, of the light is transmitted, reflected, diffracted, or blocked, etc.
  • the majority portion may be a predetermined percentage (greater than 50%) of the entire light, such as 100%, 95%, 90%, 85%, 80%, etc., which may be determined based on specific application needs.
  • Conventional LCD displays have a limited energy efficiency, as polarizers and color filters block more than 70% of the backlight.
  • Conventional OLED displays may be more energy efficient that LCD displays.
  • An OLED display may include an OLED panel and a circular polarizer laminated on top of the OLED panel.
  • the circular polarizer is used to block a reflected ambient light from bottom reflective electrodes of OLED chips in the OLE panel, thereby increasing the contrast ratio of the OLED display.
  • the circular polarizer may also reduce the energy efficiency of the OLED display. High energy efficiency and high resolution displays are desirable in various applications.
  • the present disclosure provides display devices with enhanced light transmittance.
  • the present disclosure provides non-emissive display devices (e.g., LCD displays) with enhanced light transmittance.
  • the device may include a light source configured to output a light.
  • the device may also include a display panel including a plurality of subpixel areas.
  • the device may also include a microlens assembly disposed between the light source and the display panel.
  • the microlens assembly may include a first microlens array configured to substantially collimate the light into a first polarized light, and a second microlens array configured to focus the first polarized light as a second polarized light propagating through apertures of the subpixel areas.
  • the second polarized light may propagate substantially entirely through the apertures of the subpixel areas.
  • the display panel may include a plurality of color filters, and the second polarized light may propagate substantially entirely through the color filters.
  • the first microlens array may be a first Pancharatnam Berry Phase (“PBP”) microlens array
  • the second microlens array may be a second PBP microlens array.
  • each subpixel area of the plurality of subpixel areas may include a subpixel electrode and a switching element of the subpixel electrode, the subpixel electrode corresponding to an aperture of the subpixel area, and the switching element corresponding to a non-transparent portion of the subpixel area.
  • the first polarized light and the second polarized light may be circularly polarized lights having opposite handednesses.
  • the light output from the light source may be a circularly polarized light.
  • an alignment offset between the first microlens array or the second microlens array and an array formed by the apertures of the subpixel regions may be less than or equal to 2 pm.
  • the first polarized light may have a collimation angle that is within a range of about 5° to about 15°.
  • the microlens assembly may include a waveplate disposed between the second microlens array and the display panel.
  • the microlens assembly may include a reflective polarizer disposed between the waveplate and the display panel, and a linear polarizer disposed between the reflective polarizer and the display panel.
  • the present disclosure also provides emissive display devices (e.g., LED, OLED displays) with enhanced light transmittance.
  • the device may include a plurality of light-emitting elements configured to emit an image light.
  • the device may also include a polarization converter including a plurality of converting regions and non-converting regions.
  • the device may include a microlens array disposed between the light-emitting elements and the polarization converter.
  • the microlens array may include a plurality of microlenses configured to transform a first portion of the image light as a first polarized light that is incident onto the converting regions, and transform a second portion of the image light as a second polarized light that is incident onto both of the converting regions and the non-converting regions.
  • the microlens array may include a transmissive polarization volume hologram (“PVH”) microlens array.
  • the microlens may include a plurality of central portions and periphery portions.
  • the microlenses may include a plurality of central portions and periphery portions.
  • the first portion of the image light may include portions of the image light that are incident onto central portions of the microlenses and that are circularly polarized with a first handedness.
  • the second portion of the image light may include a combination of portions of the image light that are incident onto the central portions of the microlenses and that are circularly polarized with a second handedness, and portions of the image light that are incident onto the periphery portions of the microlenses.
  • a beam size of the first polarized light at a plane intersecting one of the converting regions may be configured to be the same as or smaller than a size of the one of the converting regions.
  • an alignment offset between the microlens array and the light-emitting elements may be less than or equal to 2 mhi.
  • the first polarized light may have a first polarization
  • the second polarized light may have a second polarization that is orthogonal to the first polarization.
  • the second polarized light may include first portions incident onto the converting regions and second portions incident onto the non-converting regions.
  • the converting regions may be configured to convert the first polarized light having the first polarization into a third polarized light having the second polarization, and convert the first portions of the second polarized light having the second polarization into a fourth polarized light having the first polarization.
  • the non-converting regions may be configured to transmit the second portions of the second polarized light having the second polarization as a fifth polarized light having the second polarization.
  • the device may further include a circular polarizer configured to substantially transmit the third polarized light having the second polarization and the fifth polarized light having the second polarization, and substantially block the fourth polarized light having the first polarization.
  • the circular polarizer may include a first waveplate, a linear polarizer, and a second waveplate stacked together.
  • FIG. 1A schematically illustrates ay-z sectional view of a display device 100, according to an embodiment of the present disclosure.
  • the display device 100 may include a display panel 140, a light source 160, and a microlens assembly 150 disposed between the display panel 140 and the light source 160.
  • the light source 160 may be a backlight unit.
  • the backlight unit is used as an example of the light source 160.
  • the light source 160 is also referred to as the backlight unit 160.
  • FIG. 1 A shows the display panel 140, the microlens assembly 150, and the backlight unit 160 as having flat surfaces.
  • one or more of the display panel 140, the microlens assembly 150, and the backlight unit 160 may include one or more elements having curved surfaces.
  • the backlight unit 160 may be configured to emit a backlight for illuminating the display panel 140.
  • the microlens assembly 150 may be configured to redirect the backlight output from the backlight unit 160 to illuminate the display panel 140.
  • the backlight unit 160 may include a backlight source assembly 162, a light guide plate 164, a back frame 166.
  • the backlight source assembly 162 may be disposed adjacent a light incident surface 164-1 of the light guide plate 164, and may output a backlight to the light incident surface 164-1.
  • the backlight source assembly 162 may include one or more light-emitting diodes (“LEDs”), one or more organic light-emitting diodes (“OLEDs”), an electroluminescent panel (“ELP”), one or more cold cathode fluorescent lamps (“CCFLs”), one or more hot cathode fluorescent lamps (“HCFLs”), or one or more external electrode fluorescent lamps (“EEFLs”), etc.
  • LEDs light-emitting diodes
  • OLEDs organic light-emitting diodes
  • ELP electroluminescent panel
  • CCFLs cold cathode fluorescent lamps
  • HCFLs hot cathode fluorescent lamps
  • EEFLs external electrode fluorescent lamps
  • the LED (or OLED) backlight source may include a plurality of white LEDs (or OLEDs), or a plurality of red LEDs (or OLEDs), green LEDs (or OLEDs), and blue LEDs (or OLEDs), etc.
  • the light guide plate 164 may be fabricated based on a light transmitting material, such as a transparent acryl resin or the like. The backlight entering from the light incident surface 164-1 of the light guide plate 164 may propagate inside the light guide plate 164, and may exit the light guide plate 164 at a light output surface 164-2 toward the microlens assembly 150.
  • the backlight unit 160 may also include one or more optical elements arranged between the light guide plate 164 and the microlens assembly 150, and configured to transform the backlight output from the light guide plate 164 into a polarized light having a predetermined polarization.
  • the backlight output from the light guide plate 164 may be a linearly polarized light
  • the backlight unit 160 may include a waveplate 168 arranged between the light guide plate 164 and the microlens assembly 150.
  • the waveplate 168 may be configured to convert the linearly polarized light output from the light guide plate 164 into a circularly polarized light having a predetermined handedness.
  • the waveplate 168 may function as a broadband and wide angle quarter-wave plate (“QWP”) configured to provide a quarter-wave birefringence (or quarter- wave phase retardance) across a wide spectral range (or wavelength range) (e.g., visible spectrum) to the linearly polarized light.
  • QWP broadband and wide angle quarter-wave plate
  • the waveplate 168 may include a multi-layer birefringent material (e.g., a polymer or liquid crystals) configured to provide a quarter-wave birefringence (or quarter-wave phase retardance) across a wide spectral range (or wavelength range) (e.g., visible spectrum).
  • the backlight output from the light guide plate 164 may be a circularly polarized light having a predetermined handedness, and the waveplate 168 may be omitted.
  • the backlight unit 160 may also include one or more diffuser sheets and/or prism sheets (not shown) arranged between the light guide plate 164 and the microlens assembly 150, or between the waveplate 168 (when included) and the microlens assembly 150.
  • the one or more diffuser sheets and/or prism sheets may be configured to improve the brightness uniformity of the backlight output from the light guide plate 164, suppress or reduce undesirable hotspots with point or linear light sources in the backlight source assembly 162, etc.
  • the display panel 140 may be any suitable non-emissive display panel, such as a liquid crystal display (“LCD”) panel, a liquid crystal on silicon (“LCoS”) panel, etc.
  • the display panel 140 may include a thin-film transistor (“TFT”) array substate 110, a liquid crystal (“LC”) layer 130, and a color filter substrate 120 stacked together.
  • the LC layer 130 may be disposed between the TFT array substate 110 and the color filter substate 120.
  • the display panel 140 may include other elements, such as a polarizer disposed at an outer surface of the TFT array substate 110, and an analyzer disposed at an outer surface of the color filter substate 120.
  • FIG. IB schematically illustrates an A-A’ sectional view of the TFT array substrate 110 included in the display panel 140 shown in FIG. 1 A, according to an embodiment of the present disclosure.
  • the TFT array substate 110 may include a first substrate 115.
  • the TFT array substate 110 may include a plurality of subpixel areas 119 or subpixels 119, in which a pixel electrode layer 117 is formed.
  • the pixel electrode layer 117 and the subpixel areas 119 may be formed at a surface of the first substrate 115.
  • the plurality of subpixel areas 119 may be defined by a plurality of data lines 116 and a plurality of gate lines 118. As shown in FIG.
  • the data lines 116 may be arranged in parallel and may extend in a first direction (e.g., an x-axis direction in FIG. IB).
  • the gate lines 118 may be arranged in parallel and may extend in a second, different direction (e.g., ay-axis direction in FIG. IB).
  • the data lines 116 and the gate lines 118 may intersect one another.
  • the pixel electrode layer 117 may be formed by a plurality of subpixel electrodes 114 formed within the subpixel areas 119.
  • the TFT array substrate 110 may also include a plurality of TFTs 112 arranged in an array. As shown in FIG. 1A, the TFTs 112 may be also disposed at the first substrate 115. Each subpixel area 119 is shown in FIG.
  • IB as a small rectangular area enclosed by portions of the data lines 116 and portions of the gate lines 118, and including a subpixel electrode 114, and a TFT 112 disposed at a comer where a portion of a data line 116 and a portion of a gate line 118 intersect.
  • the rectangular shape is for illustration purpose, and the subpixel area 119 may include any suitable shape.
  • the plurality of subpixel areas 119 may have the same structure, and may be repeatedly defined at the first substrate 115.
  • a pixel may include three subpixels, e.g., red (“R”), green (“G”), and blue (“B”) subpixels. Thus, a pixel may be formed by three subpixel areas 119.
  • the pixel electrode layer 117 including the subpixel electrodes 114 may be a conductive transparent electrode layer. As shown in FIG. 1A and FIG. IB, each subpixel electrode 114 may occupy a portion of the subpixel area 119 other than the area where the TFT 112 and the corresponding metal wires (e.g., portions of the data line 116 and gate line 118) are located.
  • the TFT 112 may be a switching element of the subpixel area 119.
  • the TFT 112 may be electrically connected to a corresponding subpixel electrode 114, a corresponding gate line 118, and a corresponding data line 116.
  • the TFT 112 may be controlled by the corresponding gate line 118 and the corresponding data line 116.
  • FIG. 1C schematically illustrates a B-B’ sectional view of the color filter substate 120 included in the display panel 140 shown in FIG. 1 A, according to an embodiment of the present disclosure.
  • the color filter substrate 120 and the TFT array substrate 110 may be stacked, and may include components corresponding to one another in spatial positions.
  • the color filter substate 120 may include a second substate 125 disposed in parallel with the first substrate 115 of the TFT array substate 110.
  • the color filter substrate 120 may also include a light shielding material layer 122 (formed by all of the thick black portions shown in FIG. 1C) and a color filter layer 127 disposed at a surface of the second substate 125 facing the TFT array substrate 110.
  • the color filter layer 127 may include a plurality of color filters 124 disposed within regions enclosed by the light shielding material layer 122.
  • the light shielding material layer 122 may include a black matrix.
  • the light blocking material layer 122 is also referred to the black matrix 122 in the following descriptions.
  • the color filters 124 may be separated from one another by the black matrix 122 disposed at the peripheries of the color filters 124. Corresponding to each subpixel area 119 shown in FIG.
  • the black matrix 122 include portions covering the gate lines 118 and the data lines 116 that define the rectangular area (subpixel area 119), and a portion covering the TFT 112 disposed at the comer where the gate line 118 and the data line 116 intersect.
  • the shape of the black matrix 122 is substantially the same as the shape of the data lines 116, the gate lines 118, and the TFTs 112
  • the color filters 124 may include red (R), green (G) and blue (B) color filters, denoted by different patterns in FIGs. 1A and 1C.
  • the color filter layer 127 may include color filters 124 other than the red (R), green (G), or blue (B) color filters, which are not limited by the present disclosure.
  • the color filter 124 may include any suitable material that substantially transmits the backlight having a predetermined color and/or emits a light having a predetermined color when illuminated by the backlight.
  • the color filter 124 may include a color resist configured to substantially transmit the backlight having a predetermined color.
  • the color filter 124 may include one or more color conversion materials that absorbs the backlight and emit lights having one or more predetermined colors.
  • the color conversion material may include a quantum dot material that may enhance the energy efficiency and the color performance.
  • the color filter 124 including the color resist is used as example in the following description.
  • the subpixel electrodes 114 of the TFT array substate 110 and the color filters 124 of the color filter substrate 120 may correspond to one another in position and shape. That is, the gray portions in FIG. IB may correspond to the black portions in FIG. 1C in the thickness direction of the display device 100, as shown in FIG. 1A.
  • the TFT 112 may be opaque, and may at least partially block a backlight incident onto the TFT 112. For example, the TFT 112 may at least partially reflect and/or absorb the backlight incident onto the TFT 112.
  • the subpixel electrode 114 may be substantially transparent to the backlight, and may substantially not reflect and/or absorb the backlight.
  • the subpixel electrode 114 may also be referred to as a transparent portion of the subpixel area 119, or an aperture of the subpixel area 119.
  • the backlight output from the backlight unit 160 may be guided to propagate through the apertures of the subpixel areas 119. In some embodiments, substantially the entire backlight may propagate through the apertures.
  • a combination of the apertures of the plurality of subpixel areas 119 in the TFT array substate 110 may form an overall aperture of the TFT array substate 110. With the disclosed microlens assembly 150, substantially the entire backlight output from the backlight unit 160 may be guided to propagate through the overall aperture of the TFT array substrate 110, thereby increasing the light transmittance or efficiency.
  • the metal wires e.g., portions of the data lines 116 and the gate lines 118
  • the black matrix 122 may include a light-shielding material, e.g., for absorbing the backlight, thereby hiding the TFTs 112 and various metal wires from being perceived by a viewer of the display device 100.
  • the portion of the subpixel area 119 including various metal wires (e.g., the data lines 116 and the gate lines 118) and the TFT 112 may be referred to as a non-transparent portion of the subpixel area 119.
  • a combination of the non-transparent portions of the plurality of the subpixel area 119 included in the TFT array substate 110 may form an overall non transparent portion of the TFT array substate 110.
  • An aperture ratio of the display panel 140 may be referred to as a ratio between the area of the transparent portion (or aperture) and the area of the subpixel area 119.
  • the light transmittance of the display panel 140 may increase as the aperture ratio increases.
  • the color filters 124 may be illuminated by the backlight, and may output lights of corresponding colors. In other words, the color filters 124 may be substantially transparent to the lights of the corresponding colors.
  • the black matrix 122 may substantially block (e.g., absorb, and/or reflect) the backlight.
  • a combination of the color filters 124 may form an overall aperture of the color filter substate 120.
  • the black matrix 122 may form an overall non-transparent portion of the color filter substate 120.
  • the display panel 140 may include a common electrode layer (e.g., conductive transparent electrode layer, not shown) disposed at one of the color filter substrate 120 or the TFT array substate 110.
  • the display panel 140 may individually control (e.g., through the corresponding TFTs 112) the light transmittance of the subpixels 119 by controlling orientations of corresponding liquid crystal molecules 132. The orientations may be controlled by supplying and controlling electric fields generated between the respective subpixel electrodes 114 and the common electrode layer.
  • a backlight output from the backlight unit 160 may be transmitted through the display panel 140 to display a color image.
  • the display panel 140 may include other elements not shown in FIGs. 1A-1C.
  • the display panel 140 may include two alignment layers respectively disposed at each of the color filter substrate 120 and the TFT array substate 110, two crossed polarizers (e.g., a polarizer and an analyzer) respectively disposed at outer surfaces of the color filter substrate 120 and the TFT array substate 110, one or more insulating layers disposed between different groups of metal wires (e.g., between the data lines 116 and the gate lines 118), one or more insulating layers disposed between the pixel electrode layer 127 and the common electrode layer, one or more insulating layers disposed between the electrode layer (e.g., the pixel electrode layer 127 and/or the common electrode layer) and the metal wires, and/or storage capacitors disposed in overlapping regions between the pixel electrode layer 127 and the common electrode layer.
  • two crossed polarizers e.g., a polarizer and an analyzer
  • the display panel 140 may include two alignment layers respectively disposed at each of the color filter substrate 120 and the TFT array substate 110, two crossed polar
  • the microlens assembly 150 may be disposed at a light output side of the backlight unit 160, and at a light incident side of the display panel 140. In other words, the microlens assembly 150 may be disposed “on-cell” with respect to the display panel 140.
  • the microlens assembly 150 may include a first microlens array 151 and a second microlens array 153 disposed in parallel. In the embodiment shown in FIG. 1 A, the first microlens array 151 is shown as spaced apart from the second microlens array 153 by a gap. In some embodiments, the first microlens array 151 and the second microlens array 153 may be stacked without a gap.
  • the first microlens array 151 may include a plurality of first microlenses 152 arranged in a first array.
  • the second microlens array 153 may include a plurality of second microlenses 154 arranged in a second array.
  • the first microlens array 151 and the second microlens array 153 may be substantially aligned with one another.
  • Each of the plurality of first microlenses 152 may correspond to each of the plurality of second microlenses 154 in shape and position.
  • the first microlens array 151 and/or the second microlens array 153 may be optically patterned with the first microlenses 152 and/or the second microlenses 154.
  • neighboring first microlenses 152 in the first microlens array 151 and/or neighboring second microlenses 154 in the second microlens array 153 may be separated by dividers 156, which may be virtual dividers or actual dividers.
  • the first microlens array 151 and/or the second microlens array 153 may be substantially aligned with an array formed by the subpixels 119. In some embodiments, the first microlens array 151 and/or the second microlens array 153 may be substantially aligned with an array formed by the apertures (or the transparent portions) of the subpixels 119. For example, the first microlenses 152 and/or the second microlenses 152 may be substantially aligned with the subpixel electrodes 114 of the subpixel areas 119.
  • the first microlens array 151 and/or the second microlens array 153 may be aligned “on-cell” with an alignment offset (or alignment displacement) of less than or equal to 2 pm with respect to the array of apertures (or subpixel electrodes 114) of the subpixels 119. In some embodiments, the first microlens array 151 and/or the second microlens array 153 may be aligned “on-cell” with an alignment offset (or alignment displacement) of less than or equal to 1 pm with respect to the array of apertures (or subpixel electrodes 114) of the subpixels 119.
  • the first microlens array 151 and/or the second microlens array 153 may be aligned “on-cell” with an alignment offset (or alignment displacement) of less than or equal to 100 nanometers (“nm”) with respect to the array of apertures (or subpixel electrodes 114) of the subpixels 119.
  • the microlens assembly 150 may be a polarization selective microlens assembly (also referred to as 150 for discussion purposes).
  • the first microlens array 151 or (and) the second microlens array 153 may be polarization selective microlens array configured to provide a polarization selective optical response.
  • the first microlenses 152 may be polarization selective microlenses.
  • the second microlenses 154 may be polarization selective microlenses.
  • the first microlenses 152 and the second microlenses 154 may all be polarization selective microlenses.
  • the first microlens array 151 and the second microlens array 153 may also be referred to as a first polarization selective microlens array 151 and a second polarization selective microlens array 153, respectively.
  • the first microlenses 152 and second microlenses 154 may also be referred to as first polarization selective microlenses 152 and second polarization selective microlenses 154, respectively.
  • At least one (e.g., both) of the first polarization selective microlens array 151 or (and) the second polarization selective microlens array 153 may be circularly polarization selective.
  • at least one of the first polarization selective microlens array 151 or the second polarization selective microlens array 153 may be configured to operate in a first optical state to provide a first optical response to a circularly polarized light having a predetermined handedness, and operate in a second optical state to provide a second optical response different from the first optical response to a circularly polarized light having a handedness that is opposite to the predetermined handedness.
  • At least one (e.g., both) of the first polarization selective microlens array 151 or (and) the second polarization selective microlens array 153 may be a Pancharatnam Berry Phase (“PBP”) microlens array, and at least one (e.g., both) of the first polarization selective microlenses 152 or (and) the second polarization selective microlenses 154 may be PBP microlenses.
  • PBP Pancharatnam Berry Phase
  • the PBP microlens array may include at least one of sub-wavelength structures (e.g., a metamaterial), a birefringent material (e.g., an LC material), or a photo-refractive holographic material (e.g., an amorphous polymer).
  • the PBP microlens array may be a liquid crystal polymer (“LCP”) microlens array.
  • LCP liquid crystal polymer
  • the first polarization selective microlens array 151 or the second polarization selective microlens array 153 may be an LCP-based PBP microlens array.
  • a PBP microlens array or a PBP microlens may be configured to modulate a circularly polarized light based on a phase profile provided through a geometric phase.
  • a PBP microlens array or a PBP microlens may be configured to operate in a focusing (or converging) state for a circularly polarized light having a predetermined handedness, and operate in a defocusing (or diverging) state for a circularly polarized light having a handedness that is opposite to the predetermined handedness.
  • a PBP microlens array or a PBP microlens may reverse the handedness of a circularly polarized light transmitted therethrough while focusing or defocusing the circularly polarized light.
  • a PBP microlens or PBP microlens array may be configured to operate in a focusing (or converging) state to focus (or converge) a right-handed circularly polarized (“RHCP”) light as a left-handed circularly polarized (“LHCP”) light, and operate in a defocusing (or diverging) state to defocus (or diverge) an LHCP light as an RHCP light.
  • RHCP right-handed circularly polarized
  • LHCP left-handed circularly polarized
  • a PBP microlens or PBP microlens array may be configured to operate in a focusing (or converging) state to focus (or converge) an LHCP light as an RHCP light, and operate in a defocusing (or diverging) state to defocus (or diverge) an RHCP light as an LHCP light.
  • FIG. ID schematically illustrates an optical path of a backlight propagating in the display device 100 shown in FIG. 1 A, according to an embodiment of the present disclosure.
  • FIG. ID shows a portion of the optical path of the backlight propagating through a single subpixel or subpixel area 119.
  • Optical paths of the backlight propagating through other areas of the display device 100 may be substantially the same as that shown in FIG. ID.
  • the backlight unit 160 (not shown) may be configured to output a diffused backlight 171 that is a circularly polarized light having a predetermined handedness (e.g., an RHCP light).
  • the diffused backlight 171 may also be referred to as a circularly polarized light 171 for discussion purposes.
  • the light guide plate 164 may be configured to output a linearly polarized light
  • the waveplate 168 may be configured to convert the linearly polarized light to a circularly polarized light having the predetermined handedness (e.g., an RHCP light).
  • the light guide plate 164 may be configured to directly output a circularly polarized light having the predetermined handedness (e.g., an RHCP light), and the waveplate 168 may be omitted.
  • the one or more diffuser sheets and/or prism sheets (not shown) arranged between the light guide plate 164 and the microlens assembly 150 (or between the waveplate 168 when included and the microlens assembly 150) may be configured to diffuse the circularly polarized light output from the light guide plate 164 (or the waveplate 168 when included) as the circularly polarized light (e.g., RHCP light) 171 propagating toward the microlens assembly 150.
  • the circularly polarized light e.g., RHCP light
  • the polarization selective microlens assembly 150 may be configured to focus the circularly polarized light (e.g., RHCP light) 171, such that the circularly polarized light may propagate through the aperture of the subpixel area 119 in the TFT array substate 110 and the color filter 124 in the color filter substrate 120.
  • the circularly polarized light 171 may have a larger beam size at a plane intersecting the aperture of the subpixel area 119 and/or a plane intersecting the color filter 124 .
  • a portion of the circularly polarized light 171 may be incident onto the TFTs 112 and/or the black matrix 122 surrounding the aperture of the subpixel area 119, and may be reflected back toward the backlight unit 160 by the TFTs 112, absorbed by the TFTs 112, and/or absorbed by the black matrix 122.
  • the polarization selective microlens assembly 150 With the polarization selective microlens assembly 150 reducing the beam size of the circularly polarized light 171 at the plane intersecting the aperture of the subpixel area 119 and/or the plane intersecting the color filter 124 through focusing the circularly polarized light 171, an increased amount of the circularly polarized light 171 may propagate through the aperture area (i.e., the subpixel electrode 114) of the subpixel area 119 and/or the color filter 124.
  • substantially the entire circularly polarized light 171 may propagate through the subpixel electrode 114 of the subpixel area 119 and the color filter 124, with no portion or only a negligible portion of the circularly polarized light 171 being incident onto the TFTs 112 and being blocked (e.g., absorbed and/or reflected) by the TFTs 112.
  • the light transmittance of the display panel 140 may be increased, and the power efficiency of the entire display device 100 may be enhanced.
  • the first PBP microlens array 151 when the circularly polarized light 171 incident onto the polarization selective microlens assembly 150 is an RHCP light, the first PBP microlens array 151 may be configured to focus an RHCP light as an LHCP light, and defocus an LHCP light as an RHCP light.
  • the second PBP microlens array 153 may be configured to focus an LHCP light as an RHCP light, and defocus an RHCP light as an LHCP light.
  • the first PBP microlens array 151 may be configured to focus an LHCP light as an RHCP light, and defocus an RHCP light as an LHCP light.
  • the second PBP microlens array 153 may be configured to focus an RHCP light as an LHCP light, and defocus an LHCP light as an RHCP light.
  • the first PBP microlens array 151 may function as a condenser microlens array configured to collect and collimate the circularly polarized light (e.g., RHCP light) 171 as a circularly polarized light (e.g., an LHCP light) 173 propagating toward the second PBP microlens array 153.
  • the second PBP microlens array 153 may be configured to focus the circularly polarized light (e.g., LHCP light) 173 as a circularly polarized light (e.g., an RHCP light) 175.
  • LHCP light circularly polarized light
  • substantially the entire circularly polarized light 175 may propagate through the aperture of the subpixel area 119 in the TFT array substate 110 and the color filter 124 in the color filter substrate 120.
  • No portion of the circularly polarized light (e.g., RHCP light) 175 output from the second PBP microlens array 153 may be incident onto the TFTs 112 and/or the black matrix 122 (or the portion incident onto the TFTs 112 and/or the black matrix 122 may be significantly reduced to a negligible amount).
  • the light transmittance of the display panel 140 may be increased as compared to conventional technologies.
  • the circularly polarized light (e.g., RHCP light) 175 output from the second PBP microlens array 153 may be configured with a collimation angle within a range of about 1° to 20°, thereby maintaining a balance between a high light transmittance and a large eye-box of the display panel 140 (e.g., an LCD panel).
  • the collimation angle may be defined by the angle between an outmost ray of the circularly polarized light 175 and a surface normal of the second PBP microlens array 153.
  • the collimation angle may be within a range of about 5° to 15°.
  • the collimation angle may be within a range of about 1° to 2°, which may be desirable for high efficiency displays and waveguide in-coupling.
  • the polarization selective microlens assembly 150 may also include a waveplate 155 disposed between the display panel 140 and the second PBP microlens array 153.
  • the display panel 140 may include a polarizer (e.g., a linear polarizer) 180 and an analyzer (e.g., a linear polarizer) 182 disposed at outer surfaces of the TFT array substrate 110 and the color filter substrate 120, respectively.
  • the polarizer (e.g., linear polarizer) 180 and the analyzer (e.g., linear polarizer) 182 may have orthogonal polarization axes.
  • the waveplate 155 may be disposed between the polarizer 180 and the polarization selective microlens assembly 150.
  • the polarizer 180 may be disposed between the waveplate 155 and the TFT array substrate 110.
  • the display panel 140 may be disposed between the polarizer 182 and the TFT array substrate 110.
  • the waveplate 155 may function as a QWP configured to convert the circularly polarized light (e.g., RHCP light) 175 output from the second PBP microlens array 153 as a linearly polarized light 177, while transmitting the circularly polarized light 175.
  • the linearly polarized light 177 may be configured with a polarization direction that substantially matches with a direction of a polarization axis of the polarizer 180.
  • the linearly polarized light 177 may be a p-polarized light.
  • the waveplate 155 may function as a broadband and wide angle QWP configured to provide a quarter-wave birefringence (or quarter-wave phase retardance) across a wide spectral range (e.g., visible spectrum) and a wide incidence angle range.
  • the waveplate 155 may include a multi-layer birefringent material (e.g., a polymer or liquid crystals) configured to provide a quarter-wave birefringence (or quarter-wave phase retardance) across a wide spectral range and a wide incidence angle range.
  • the polarizer 180 may be configured to substantially transmit the linearly polarized light (e.g., p-polarized light) 177 as a linearly polarized light (e.g., a p-polarized light) 179 propagating toward the TFT array substrate 110. Substantially the entire linearly polarized light (e.g., p-polarized light) 179 may propagate through the aperture of the subpixel area 119 in the TFT array substate 110 and the color filter 124 in the color filter substrate 120.
  • the light transmittance of the display panel 140 may be improved.
  • FIG. IE schematically illustrates a beam spot 174 of the linearly polarized light (e.g., p-polarized light) 177 at a plane intersecting a single subpixel area 119 of the TFT array substate 110 shown in FIG. 1 A, according to an embodiment of the present disclosure.
  • the beam spot 174 may be configured with a size (or dimension) that is smaller than or equal to the size (or dimension) of the aperture of the subpixel area 119.
  • the beam spot 174 is shown with a circular shape. In some embodiments, the beam spot 174 may have other shapes.
  • the beam spot 174 may not overlap with the TFT 112 or the wires (e.g., the data line 116 and/or the gate line 118). Thus, the linearly polarized light 177 may not be incident onto the TFT 112 and the wires, and hence may not be back-reflected by the TFT 112 and the wires toward the microlens assembly 150, and/or absorbed by the TFT 112 and/or the wires.
  • the size (or dimension) of the beam spot 174 may also be referred to as a beam size of the linearly polarized light 177 at the plane intersecting the subpixel area 119. As shown in FIG.
  • the beam size of the linearly polarized light 177 may be configured to be smaller than or equal to the size of the aperture of the subpixel area 119.
  • a diameter of the beam spot 174 may be smaller than or equal to a width and a length of the aperture of the subpixel area 119.
  • the width of the aperture of the subpixel area 119 may be a dimension of the aperture along a direction parallel with the gate lines 118, and the length of the aperture of the of the subpixel area 119 may be a dimension of the aperture along a direction parallel with the data lines 116.
  • FIG. IF schematically illustrates a beam spot 176 of the linearly polarized light 177 at a plane intersecting a single color filter 124 of the color filter substate 120 shown in FIG. 1A, according to an embodiment of the present disclosure.
  • the beam spot 176 may be configured with a size (or dimension) that is equal to or smaller than the size (or dimension) of the color filter 124.
  • the beam spot 176 may not overlap with the black matrix 122.
  • the linearly polarized light 177 may not be incident onto the black matrix 122, and hence may not be absorbed by the black matrix 122.
  • the size (or dimension) of the beam spot 176 may also be referred to as a beam size of the linearly polarized light 177 at the plane intersecting the color filter 124.
  • the beam size of the linearly polarized light 177 may be configured to be smaller than the size of the color filter 124.
  • the beam spot 176 of the linearly polarized light 177 may have a circular shape.
  • a diameter of the beam spot 176 may be smaller than a width and a length of the color filter 124.
  • the width of the color filter 124 may be a dimension along a direction parallel with the gate lines 118, and the length of the color filter 124 may be a dimension along a direction parallel with the data lines 116.
  • the beam spot 176 of the linearly polarized light 177 at a plane intersecting the color filter 124 may be configured to have a size (or dimension) that is equal to or smaller than the size (or dimension) of the beam spot 174 of the linearly polarized light 177 at a plane intersecting the aperture of the subpixel areas 119.
  • the size of the beam spot 176 shown in FIG. IF may be smaller than the size of the beam spot 174 shown in FIG. IE.
  • the diameter of the beam spot 176 may be configured to be smaller than the diameter of the beam spot 176.
  • FIG. 1G schematically illustrates a y-z sectional of a portion of a display device 190, according to an embodiment of the present disclosure.
  • the display device 190 may include elements, structures, and/or functions that are the same as or similar to those included in the display device 100 shown in FIG. 1A. Descriptions of the same or similar elements, structures, and/or functions can refer to the above descriptions rendered in connection with FIG. 1A.
  • the display device 190 may include the backlight unit 160 (not shown), a microlens assembly 195, and the display panel 140 arranged in an optical series.
  • FIG. 1G shows the display panel 140, the microlens assembly 195, and the backlight unit 160 as having flat surfaces.
  • one or more of the display panel 140, the microlens assembly 195, and the backlight unit 160 may include one or more elements having curved surfaces.
  • the microlens assembly 195 may be polarization selective.
  • the microlens assembly 195 may include components similar to the components included in the polarization selective microlens assembly 150 shown in FIGs. 1A-1F.
  • the microlens assembly 195 may include the first polarization selective microlens array (e.g., first PBP microlens array) 151, the second polarization selective microlens array (e.g., second PBP microlens array) 153, and the waveplate 155 arranged in an optical series.
  • the microlens assembly 195 may further include a first polarizer 157 disposed between the waveplate 155 and the display panel 140, and a second polarizer 159 disposed between the first polarizer 157 and the display panel 140.
  • the combination of the first polarizer 157 and the second polarizer 159 may be configured to reduce a leakage of a light having an undesirable polarization.
  • the first polarizer 157 may be a linear reflective polarizer configured to substantially reflect a linearly polarized light having a predetermined polarization, and substantially transmit a linearly polarized light having a polarization orthogonal to the predetermined polarization.
  • the second polarizer 159 may be a linear absorption polarizer configured to substantially transmit a linearly polarized light having a predetermined polarization, and substantially block, via absorption, a linearly polarized light having a polarization direction orthogonal to the predetermined polarization.
  • the combination of the first polarizer 157 and the second polarizer 159 may substantially transmit a linearly polarized light with a desirable polarization, and substantially block (via absorption) a linearly polarized light with an orthogonal polarization, thereby suppressing the ghost images caused by the linearly polarized light with the orthogonal polarization.
  • FIG. 1H illustrates an optical path of the backlight 171 in the display device 190, according to an embodiment of the present disclosure.
  • FIG. 1H shows an optical path of the backlight 171 in a portion of the display device 190 corresponding to a single subpixel area 119.
  • Optical paths of the backlight 171 in the entire display device 190 may be substantially the same as that shown in FIG. 1H.
  • the optical path of the backlight 171 propagating through the first PBP microlens array 151, the second PBP microlens array 153, and the waveplate 155 may be similar to that shown in FIG. ID.
  • the light 175 output from the second PBP microlens array 153 may include a desirable component (e.g., an RHCP component) and an undesirable component (e.g., an LHCP component).
  • the waveplate 155 may be configured to convert the light 175 to the light 177.
  • the light 177 may propagate toward the first polarizer (e.g., linear reflective polarizer) 157.
  • the light 177 may include a desirable component (e.g., a p-polarized component) and an undesirable component (e.g., an s-polarized component).
  • the first polarizer 157 may be configured to substantially transmit the desirable component (e.g., p-polarized component) of the light 177 as a p-polarized light 181 toward the second polarizer (e.g., linear absorption polarizer) 159, and substantially reflect the undesirable component (e.g., s-polarized component) of the light 177 as an s- polarized light (not shown).
  • the first polarizer 157 may transform the light 177 as a light 181 propagating toward the second polarizer (e.g., linear absorption polarizer) 159.
  • the light 181 may also include a desirable component (e.g., a p- polarized component transmitted by the first polarizer 157) and an undesirable component (e.g., an s-polarized component transmitted by the first polarizer 157).
  • a desirable component e.g., a p- polarized component transmitted by the first polarizer 15
  • an undesirable component e.g., an s-polarized component transmitted by the first polarizer 157.
  • the second polarizer 159 may be configured to substantially transmit the desirable component (e.g., p-polarized component) of the light 181 as a linearly polarized light (e.g., a p-polarized light) 183, and substantially block, via absorption, the undesirable component (e.g., s-polarized component) of the light 181.
  • a leakage of the undesirable component (e.g., LHCP component) output from the second PBP microlens array 153 may be reduced by the first polarizer 157 and the second polarizer 159. Accordingly, a ghost image caused by the light leakage may be suppressed.
  • Substantially the entire linearly polarized light (e.g., p- polarized light) 183 may propagate through the aperture of the subpixel area 119 in the TFT array substate 110 and the color filter 124 in the color filter substrate 120. No portion (or only a negligible portion) of the linearly polarized light 183 may be incident onto the TFTs 112 and/or the black matrix 122, and be back-reflected by the TFTs 112 toward the microlens assembly 195, absorbed by the TFTs 112, and/or absorbed by the black matrix 122.
  • the second polarizer 159 shown in FIG. 1H may also function as the polarizer 180 included in the display panel 140 shown in FIG. 1G.
  • the second polarizer 159 and the analyzer 182 shown in FIG. 1H may have orthogonal polarization axes.
  • the first polarizer 157 shown in FIG. 1H may be omitted.
  • a combination of the waveplate 155, the first polarizer 157, and the second polarizer 159 may be replaced by a combination of a circular reflective polarizer, the waveplate 155, and the second polarizer 159.
  • FIG. 2 schematically illustrates an optical path of a backlight 205 in a conventional display device 200.
  • the conventional display device 200 may include a backlight unit 260 and a display panel 240.
  • the backlight unit 260 may include a backlight source assembly 262, a light guide plate 264, and a back frame 266.
  • the light guide plate 264 may include a light incident surface 264-1 and a light output surface 264-2.
  • the display panel 240 may include a TFT array substrate 210 and a color filter substrate 220.
  • the TFT array substrate 210 may include a first substrate 215 and a plurality of subpixel areas 219 formed on a surface of the first substrate 215.
  • the subpixel areas 219 may be defined by wires similar to the gate lines 118 and the data lines 116. Within each subpixel area 219, there may be a subpixel electrode 214, a TFT 212, and portions of the corresponding wires.
  • the color filter substrate 220 may be provided at a surface of a second substrate 225 facing the first substrate 215.
  • the color filter substrate 220 may include a plurality of color filters 224 and a black matrix 222.
  • the display panel 240 may include an LC layer 230 including LC molecules 232.
  • the LC layer 230 may be disposed between the TFT array substrate 210 and the color filter substrate 220.
  • the conventional display device 200 may not include the microlens assembly 150 shown in FIG. 1A.
  • the display panel 240 may be directly coupled to the backlight unit 260.
  • the backlight unit 260 may emit a backlight 205 for illuminating the display panel 240.
  • FIG. 2 shows an optical path of the backlight 205 in a portion of the display device 200 corresponding to a single subpixel area 219.
  • Optical paths of the backlight 205 in corresponding to other subpixel areas 219 in the rest of the display device 200 may be substantially the same as that shown in FIG. 2.
  • the backlight unit 260 may output the diffused backlight 205 toward the display panel 240.
  • a portion of the backlight 205 may be incident onto the TFTs 212 and the black matrix 222.
  • a portion of the diffused backlight 205 may be reflected and/or absorbed by the TFTs 212, and absorbed by the black matrix 122.
  • the light transmittance of the display panel 240 may be decreased, and the power efficiency of the display device 200 may be reduced.
  • the decrease of the light transmittance of the display panel 240 may become more severe for LCD panels with a high pixel density (or high pixel per inch (“ppi”), high resolution), e.g., LCD panels with over 1000 ppi.
  • the display device 100 or 190 of the present disclosure as shown in FIGs. 1A-1H may include the microlens assembly 150 or 195 disposed between the display panel 140 and the backlight unit 160.
  • the microlens assembly 150 or 195 may be polarization selective.
  • the microlens assembly 150 or 195 may transform the diffused backlight 171 into a focused light 177 or 183 that propagates through the apertures of the subpixel areas 119 in the TFT array substate 110 and the color filters 124 in the color filter substrate 120, with no portion of (or only a negligible portion of) the light 177 or 183 being back-reflected by the TFTs 112, being absorbed by the TFTs 112, and/or being absorbed by the black matrix 122.
  • the disclosed display device 100 or 190 shown in FIGs. 1 A-1H provides an enhanced light transmittance and an increased power efficiency.
  • the increase in the light transmittance and the power efficiency may become more prominent when the display panel 140 is an LCD panel having a high pixel density (or high ppi, or high resolution), e.g., an LCD panel with over 100 or 1900 ppi.
  • the first microlens array 151 and the second microlens array 153 are shown to be spherical microlens arrays, which are for illustrative purposes.
  • each of the first microlens array 151 and the second microlens array 153 may be a spherical microlens array, an aspherical microlens array, a cylindrical microlens array, or a freeform microlens array, etc.
  • Each of the first microlens 152 and the second microlens 154 may be a spherical microlens, an aspherical microlens, a cylindrical microlens, or a freeform microlens, etc.
  • the microlens assembly 150 or 195 is shown to include two microlens arrays stacked in parallel: the first microlens array 151 configured to substantially collimate the backlight into a first polarized light, and the second microlens array 153 configured to focus the first polarized light as a second polarized light propagating through apertures of the subpixel areas.
  • This configuration is for illustrative purposes.
  • the microlens assembly 150 or 195 may include more than two microlens arrays arranged in parallel.
  • Each microlens array may be a spherical microlens array, an aspherical microlens array, a cylindrical microlens array, or a freeform microlens array, etc.
  • the more than two microlens arrays may include at least one freeform microlens array, which may enable a high collimation of the backlight output from the second microlens array 153, e.g., within a range of about 1° to 2°.
  • the microlens arrays included in the microlens assembly 150 or 195 may be fabricated using any suitable fabrication method, such as holographic interference, laser direct writing, ink-jet printing, or various other forms of lithography.
  • a photo-alignment material may be disposed at the display panel 140 and optically patterned (e.g., via a polarization interference) to form an alignment layer corresponding to a desirable microlens array.
  • a polymerizable LC material may be disposed on the alignment layer, and aligned by the alignment layer to form the desirable microlens array.
  • the LC material may be further polymerized to stabilize the microlens array.
  • a birefringent photo-refractive holographic material other than the LC material may be disposed at the display panel 140 and optically patterned (e.g., via a polarization interference) to form a desirable microlens array directly.
  • the above-mentioned steps may be repeated to fabricate a plurality of microlens arrays on the display panel 140.
  • the microlens array may be fabricated “on-cell” with an alignment offset (or alignment displacement) of less than or equal to 2 pm (or 1 pm, or 100 nm) with respect to the array of apertures (or subpixel electrodes 114) of the subpixels 119.
  • two-photon polarization laser writing may be used to fabricate a freeform microlens array.
  • the TFTs 112 and the color filters 124 are disposed at different sides of the LC layer 130.
  • This configuration is for illustrative purposes, and other suitable configurations may be used.
  • the TFTs 112 and the color filters 124 may be disposed at the same side of the LC layer 130, e.g., both of the TFTs 112 and the color filters 124 may be disposed at the first substate 115 or the second substate 125.
  • the TFT array substate 110 or the color filter substate 120 may include both of the TFTs 112 and the color filters 124.
  • the principle described above for increasing the light transmittance and power efficiency of the display device 100 or 190 via the polarization selective microlens assembly 150 or 195 may be applicable to any suitable display device including a non-emissive display panel and a backlight unit, and is not limited to the display device 100 or 190 shown in FIGs. 1A-1H.
  • the non-emissive display panel may be any suitable non-emissive display panel, such as any suitable LCD panel, any suitable LCoS display panel, etc.
  • the non-emissive display panel may include any suitable elements and structures arranged in any suitable configurations.
  • the LCD panel and the LCoS display panel may operate in any suitable operation mode, such as a twisted-nematic (“TN”) mode, an in-plane-switching (“IPS”) mode, a fringe field switching (“FFS”) mode, a vertical alignment (“VA”) mode, a multidomain vertical alignment (“MV A”) mode, or a blue phase mode, etc.
  • the backlight unit may be any suitable backlight units, such as an edge-lit backlight unit, or a direct-lit backlight unit, etc.
  • FIGs. 3A-3D illustrate a PBP microlens 300, according to an embodiment of the present disclosure.
  • the PBP microlens 300 may be an embodiment of the microlens 152 or 154 included in the first PBP microlens array 151 or the second PBP microlens array 153 shown in FIG. 1A.
  • the PBP microlens 300 may include a birefringent film 305.
  • An optic axis of the birefringent film 305 may be configured with an in-plane orientation pattern, in which the orientation of the optic axis may continuously vary in at least two opposite in-plane directions (e.g., a plurality of opposite radial directions) from a center of the in-plane orientation pattern to two opposite peripheries of the in-plane orientation pattern with a varying pitch (e.g., decreasing from center to peripheries).
  • the birefringent film 305 may include optical anisotropic molecules 312.
  • FIG. 3A schematically illustrates an x-y sectional view of an in-plane orientation pattern of optical anisotropic molecules 312 in the birefringent film 305 of the PBP microlens 300, according to an embodiment of the present disclosure.
  • FIG. 3B illustrates a section of the in-plane orientation pattern taken along ay-axis in the birefringent film 305 of the PBP microlens 300 shown in FIG. 3A, according to an embodiment of the present disclosure.
  • the birefringent film 305 may include an LC material, and rod-like LC molecules 312 are used as examples of the optically anisotropic molecules 312 of the birefringent film 305.
  • the rod-like LC molecule 312 may have a longitudinal direction (or a length direction) and a lateral direction (or a width direction).
  • the longitudinal direction of the LC molecule 312 may be referred to as a director of the LC molecule 312 or an LC director.
  • An orientation of the LC director may determine a local optic axis orientation or an orientation of the optic axis at a local point of the birefringent film 305.
  • the term “optic axis” may refer to a direction in a crystal. A light propagating in the optic axis direction may not experience birefringence (or double refraction). An optic axis may be a direction rather than a single line: lights propagating in directions parallel to that direction may experience no birefringence.
  • the local optic axis may refer to an optic axis within a predetermined region of a crystal.
  • the LC molecules 312 located in close proximity to or at a surface (e.g., at least one of a first surface or a second surface) of the birefringent film 305 may be configured with an in-plane orientation pattern having a varying pitch in at least two opposite in-plane directions (e.g., a plurality of radial directions) from a lens center 310 to opposite lens peripheries 315.
  • orientations of LC directors of LC molecules 312 located in close proximity to or at the surface of the birefringent film 305 may exhibit a continuously rotation in at least two opposite in-plane directions from the lens center 310 to the opposite lens peripheries 315 with a varying pitch A.
  • the orientations of the LC directors may exhibit a rotation in a same rotation direction (e.g., clockwise, or counter-clockwise) from the lens center 310 to the opposite lens peripheries 315.
  • a pitch A of the in-plane orientation pattern may be defined as a distance in the in-plane direction (e.g., a radial direction) over which the orientation of the LC director (or an azimuthal angle f of the LC molecule 312) changes by a predetermined angle (e.g., 180°) from a predetermined initial state.
  • the pitch A of the in-plane orientation pattern may also be referred to as an in-plane pitch of the in-plane orientation pattern. As shown in FIG.
  • the pitch A may be a function of the distance from the lens center 310.
  • the pitch A may monotonically decrease from the lens center 310 to the lens peripheries 315 in the at least two opposite in-plane directions (e.g., a plurality of opposite radial directions) in the x-y plane, e.g., Ao > Ai > ... > A r .
  • Ao is the pitch at a central region of the PBP microlens 300, which may be the largest.
  • the pitch A r is the pitch at an edge region (e.g., periphery 315) of the PBP microlens 300, which may be the smallest.
  • the azimuthal angle f of the LC molecule 312 may change in proportional to the distance from the lens center 310 to a local point of the birefringent film 305 at which the LC molecule 312 is located.
  • the LC directors (or the azimuth angles f) of the LC molecules 312 may remain in the same orientation (or value) from the first surface to the second surface of the birefringent film 305.
  • a twist structure may be introduced along the thickness direction of the birefringent film 305 and may be compensated for by its mirror twist structure, which may enable the PBP microlens 300 to have an achromatic performance.
  • the PBP microlens 300 may be a passive PBP microlens.
  • a passive PBP lens may have, or may be configurable to operate in, two optical states, i.e., a focusing (or converging) state and a defocusing (or diverging) state.
  • the optical state of the passive PBP lens may depend on the handedness of a circularly polarized input light and the rotation direction of the LC directors in the at least two opposite in-plane directions from the lens center 310 to the opposite lens peripheries 315. For example, as shown in FIG.
  • the PBP microlens 300 may operate in the focusing state (or the converging state) for an RHCP light 330 having a wavelength in a predetermined wavelength range. As shown in FIG. 3D, the PBP microlens 300 may operate in the defocusing state (or the diverging state) for an LHCP light 335 having a wavelength in a predetermined wavelength range. In addition, the PBP microlens 300 may reverse the handedness of a circularly polarized light transmitted therethrough in addition to focusing/defocusing the light. For example, as shown in FIG. 3C, the PBP microlens 300 may focus the RHCP light 330 as an LHCP light 340. As shown in FIG.
  • the PBP microlens 300 may defocus the LHCP light 335 as an RHCP light 345.
  • the PBP microlens 300 may be indirectly switchable between the positive state and the negative state when a handedness of an input light is changed through an external polarization switch.
  • the PBP microlens 300 based on LCs shown in FIGs. 3A-3D are for illustrative purposes.
  • the PBP microlens may be based on sub-wavelength structures, a birefringent material (e.g., LCs), a photo-refractive holographic material, or any combination thereof.
  • FIG. 4A schematically illustrates a y-z sectional view of a display device 400, according to an embodiment of the present disclosure.
  • the display device 400 may be an emissive display device.
  • the display device 400 may include a plurality of light-emitting diodes.
  • the display device 400 may be an OLED display device, an LED display device, a pOLED display device, an mLED display device, or a pLED display device, etc. As shown in FIG.
  • the display device 400 may include a display panel 410, a microlens array 420, a polarization converter 430, a first waveplate 440, a polarizer 450, and a second waveplate 460 arranged in an optical series.
  • the display panel 410, the microlens array 420, the polarization converter 430, the first waveplate 440, the polarizer 450, and the second waveplate 460 are drawn as having flat surfaces.
  • one or more of the display panel 410, the microlens array 420, the polarization converter 430, the first waveplate 440, the polarizer 450, and the second waveplate 460 may have curved surfaces.
  • the display device 400 may also include other elements that are not shown in FIG. 4A. In some embodiments, one or more components shown in FIG. 4A may be omitted.
  • the display panel 410 may include a self-emissive panel that includes a plurality of light-emitting elements (e.g., light-emitting chips) 411 arranged in an array.
  • the light- emitting elements 411 may function as subpixels (also referred to as 411 for discussion purposes).
  • the display panel 410 may include an OLED display panel, a pOLED display panel, an mLED display panel, or a pLED display panel, etc., in which OLED chips, pOLED chips, mLED chips, or pLED chips, etc., may function as subpixels 411.
  • the light-emitting elements 411 may include red (“R”), green (“G”), and blue (“B”) light-emitting elements.
  • the display panel 410 may include red (“R”), green (“G”), and blue (“B”) subpixels 411.
  • an elementary pixel may include three subpixels, e.g., red (“R”), green (“G”), and blue (“B”) subpixels.
  • the light-emitting element 411 may include a light-emitting area 415 and a non emitting area 413.
  • the non-emitting area 413 may surround or define the light-emitting area 415.
  • the display panel 410 may include a light shielding material, such as a black matrix (not shown) configured to cover (or conceal) the non-emitting area 413 from being perceived by a viewer of the display device 400.
  • the microlens array 420 may be polarization selective.
  • the microlens array 420 may be disposed between the display panel 410 and the polarization converter 430.
  • the polarization converter 430 may be a patterned polarization converter.
  • the microlens array 420 is shown as spaced apart from the display panel 410 by a gap.
  • the microlens array 420 and the display panel 410 may be stacked without a gap.
  • the microlens array 420 may be directly disposed on the display panel 410 without a gap. In such an embodiment, the crosstalk between neighboring subpixels 411 may be suppressed.
  • the microlens array 420 may include a plurality of microlenses 421 arranged in an array. FIG.
  • the microlenses 421 may be polarization selective microlenses.
  • the microlenses 421 may be substantially aligned with the light-emitting elements (or subpixels) 411 in the display panel 410.
  • an alignment displacement (or an alignment offset) between the array of the light-emitting elements (or subpixels) 411 and the microlens array 420 may be less than or equal to 2 pm.
  • an alignment displacement (or an alignment offset) between the array of the light-emitting elements (or subpixels) 411 and the microlens array 420 may be less than or equal to 1 pm.
  • an alignment displacement (or an alignment offset) between the array of the light-emitting elements (or subpixels) 411 and the microlens array 420 may be less than or equal to 100 nm.
  • the microlens array 420 may be circular polarization selective.
  • the microlens array 420 may be a transmissive polarization volume hologram (“T-PVH”) microlens array, and the microlenses 421 may be T-PVH microlenses.
  • the microlens array 420 may be configured to modulate a circularly polarized light via Bragg diffraction.
  • the microlens array 420 may include at least one of sub-wavelength structures (e.g., a metamaterial), a birefringent material (e.g., an LC material), or a photo-refractive holographic material (e.g., an amorphous polymer).
  • the microlens array 420 may be a liquid crystal polymer (“LCP”) microlens array.
  • LCP liquid crystal polymer
  • the microlens array 420 may be an LCP-based T-PVH microlens array.
  • the microlens array 420 or microlenses 421 may be fabricated using various methods, such as holographic interference, laser direct writing, ink jet printing, or various other forms of lithography.
  • a “hologram” as described herein is not limited to the fabrication by holographic interference, or “holography.”
  • FIG. 5A illustrates ay-z sectional view of a T-PVH microlens 500, according to an embodiment of the present disclosure.
  • the T-PVH microlens 500 may be an embodiment of the microlens lens 421 shown in FIG. 4A, when the microlens lens 421 is circular polarization selective.
  • the T-PVH microlens 500 may include at least one of sub-wavelength structures (e.g., a metamaterial), a birefringent material (e.g., an LC material), or a photo-refractive holographic material (e.g., an amorphous polymer).
  • sub-wavelength structures e.g., a metamaterial
  • a birefringent material e.g., an LC material
  • a photo-refractive holographic material e.g., an amorphous polymer
  • the T-PVH microlens 500 may include a birefringent film 505 that includes optical anisotropic molecules (e.g., LC molecules).
  • LC molecules located in close proximity to or at a surface of the birefringent film 505 of the T-PVH microlens 500 may be configured with an in-plane orientation pattern that is similar to the x-y sectional view of the in-plane orientations of the LC molecules 312 in the birefringent film 305 of the PBP microlens 300 shown in FIGs. 3A and 3B.
  • the LC molecules within a volume of the birefringent film 505 of the T-PVH microlens 500, the LC molecules may be arranged in a plurality of helical structures.
  • the orientations of the LC directors of the LC molecules in a single helical structure may exhibit a continuous rotation in a predetermined rotation direction along a helical axis.
  • the helical axis of the helical structures may be substantially perpendicular to the surface of the birefringent film 505.
  • the helical axes of the helical structures may extend in a thickness direction of the birefringent film 505.
  • the LC molecules from the plurality of helical structures having a same orientation of the LC directors may form a series of parallel refractive index planes 501 periodically distributed within the volume of the birefringent film 505.
  • Different series of parallel refractive index planes 501 may be formed by the LC molecules having different orientations.
  • the LC molecules may have the same orientation and the refractive index may be the same.
  • Different series of refractive index planes 501 may correspond to different refractive indices.
  • the series of parallel refractive index planes 501 may be slanted with respect to the surface of the birefringent film 505.
  • Bragg diffraction may be established according to the principles of volume gratings.
  • the periodically distributed refractive index planes may also be referred to as Bragg planes 501.
  • the different series of Bragg planes 501 formed within the volume of the birefringent film 505 may produce a varying refractive index profile that is periodically distributed in the volume of the birefringent film 505.
  • the T-PVH microlens 500 may modulate (e.g., diffract) an input light satisfying a Bragg condition through Bragg diffraction.
  • the T-PVH microlens 500 may include a central portion 515 and a periphery portion 510 surrounding the central portion 515.
  • the central portion 515 may be a central portion of the circular aperture
  • the periphery portion 510 may be the rest of the circular aperture surrounding the central portion 515.
  • the Bragg planes 501 may be increasingly slanted (with respect to a normal of a surface of the T-PVH microlens 500) from the central portion 515 to the periphery portion 510 in at least two opposite radial directions of the T-PVH microlens 500, e.g., the two opposite radial directions along the y axis.
  • the Bragg planes 501 may be increasingly slanted (with respect to a normal of a surface of the T-PVH microlens 500) from the central portion 515 to the periphery portion 510 in at least two opposite radial directions of the T-PVH microlens 500, e.g., the two opposite radial directions along the y axis.
  • the in-plane pitch A of the in-plane orientation pattern of the T-PVH microlens 500 may monotonically decrease from a lens center (or the central portion 515) to lens peripheries (or the periphery portion 510) in at least two opposite radial direchons of the T-PVH microlens 500, e.g., the two opposite radial directions along the y axis.
  • the central portion 515 of the T-PVH microlens 500 may have a relatively large in-plane pitch (e.g., larger than or equal to 1 pm), and the periphery portion 510 of the T-PVH microlens 500 may have a relatively small in-plane pitch (e.g., smaller than 1 pm).
  • the in-plane pitch at the central portion 515 of the T-PVH microlens 500 may be configured to be larger than or equal to 1 pm.
  • the central portion 515 of the T-PVH microlens 500 may function similar to a PBP microlens (similar to that shown in FIGs. 3C and 3D).
  • the central portion 515 of the T-PVH microlens 500 may focus (or converge) a circularly polarized light with a predetermined handedness, and defocus (or diverge) a circularly polarized light with a handedness that is opposite to the predetermined handedness.
  • the central portion 515 of the T-PVH microlens 500 may also reverse the handednesses of the focused light and the defocused light.
  • the in-plane pitch at the periphery portion 510 of the T-PVH microlens 500 may be configured to be smaller than 1 pm.
  • the periphery portion 510 of the T-PVH microlens 500 may function as a T-PVH grating with an optical power.
  • the periphery portion 510 of the T- PVH microlens 500 may substantially forwardly diffract a circularly polarized light with a predetermined handedness, and substantially transmit, with negligible diffraction, a circularly polarized light with a handedness that is opposite to the predetermined handedness.
  • the periphery portion 510 of the T-PVH microlens 500 may reverse a handedness of the diffracted light, and substantially maintain a handedness of the transmitted light.
  • orientations of the Bragg planes 501 within the volume of the T-PVH microlens 500 are configured, such that the periphery portion 510 of the T-PVH microlens 500 may diverge, via forward diffraction, the circularly polarized light with the predetermined handedness.
  • FIGs. 5A-5C illustrate polarization selective diffractions of the T-PVH microlens 500, according to an embodiment of the present disclosure.
  • R denotes an RHCP light
  • L denotes an LHCP light.
  • the handednesses of the lights shown in FIGs. 5A- 5C are for illustrative purposes. In other embodiments, the handednesses may be reversed or switched (e.g., R switched to L, and L switched to R) from those shown in FIGs. 5A-5C. In the embodiment shown in FIGs.
  • the central portion 515 of the T-PVH microlens 500 may function as a PBP microlens configured to focus (or converge) a circularly polarized light with a first handedness (e.g., an LHCP light), and defocus (or diverge) a circularly polarized light with a second handedness that is opposite to the first handedness (e.g., an RHCP light).
  • a first handedness e.g., an LHCP light
  • defocus or diverge
  • a circularly polarized light with a second handedness that is opposite to the first handedness e.g., an RHCP light
  • the periphery portion 510 of the T-PVH microlens 500 may function as a T- PVH grating configured to substantially forwardly diffract a circularly polarized light with the second handedness (e.g., an RHCP light), and substantially transmit, with negligible diffraction, a circularly polarized light with the first handedness (e.g., an LHCP light).
  • the orientations of the Bragg planes 501 within the volume of the T-PVH microlens 500 are configured, such that the periphery portion 510 of the T-PVH microlens 500 may diverge, via forward diffraction, the circularly polarized light with the second handedness (e.g., the RHCP light)
  • a circularly polarized light 502 with the first handedness may be incident onto the T-PVH microlens 500.
  • the LHCP light 502 may be a substantially collimated light, e.g., a fully collimated light or a non-fully collimated light with a negligible divergence.
  • the LHCP light 502 may include a central portion 502a incident onto the central portion 515 of the T-PVH microlens 500, and a periphery portion 502b incident onto the periphery portion 510 of the T-PVH microlens 500.
  • the central portion 515 of the T-PVH microlens 500 may be configured to focus (or converge) the central portion 502a of the LHCP light 502 as a focused RHCP light 504a.
  • the periphery portion 510 of the T-PVH microlens 500 may be configured to substantially transmit, with negligible diffraction, the periphery portion 502b of the LHCP light 502 as a substantially collimated LHCP light 504b.
  • the T-PVH microlens 500 may output the focused light (e.g., RHCP light) 504a from the central portion 515 of the T-PVH microlens 500, and the substantially collimated periphery light (e.g., RHCP light) 504a from the central portion 515 of the T-PVH microlens 500, and the substantially collimated periphery light (e.g., RHCP light) 504a from the central portion 515 of the T-PVH microlens 500, and the substantially collimated periphery light (e.g., RHCP light) 504a from the central portion 515 of the T-PVH microlens 500, and the substantially collimated periphery light (e.g., RHCP light) 504a from the central portion 515 of the T-PVH microlens 500, and the substantially collimated periphery light (e.g., RHCP light) 504a from the central portion
  • the focused light (e.g., RHCP light) 504a and the substantially collimated periphery light (e.g., LHCP light) 504b may be combined to be visually observed as a light 504.
  • a circularly polarized light 512 with the second handedness may be incident onto the T-PVH microlens 500.
  • the RHCP light 512 may be a substantially collimated light, e.g., a fully collimated light or a non-fully collimated light with a negligible divergence.
  • the RHCP light 512 may include a central portion 512a incident onto the central portion 515 of the T-PVH microlens 500, and a periphery portion 512b incident onto the periphery portion 510 of the T-PVH microlens 500.
  • the central portion 515 of the T-PVH microlens 500 may be configured to forwardly diffract and defocus (or diverge) the central portion 512a of the LHCP light 512 as a defocused LHCP light 514a.
  • the periphery portion 510 of the T- PVH microlens 500 may be configured to forwardly diffract and defocus (or diverge) the periphery portion 512b of the LHCP light 512 as an LHCP light 514b.
  • the T-PVH microlens 500 may output the defocused LHCP light 514a from the central portion 515 of the T-PVH microlens 500, and the defocused LHCP light 514b from the periphery portion 510 of the T-PVH microlens 500.
  • defocused LHCP light 514a and the defocused LHCP light 514b may be combined to be visually observed as a defocused LHCP light 514.
  • a light 552 incident onto the T-PVH microlens 500 may include a central portion 552a incident onto the central portion 515 of the T-PVH microlens 500, and a periphery portion 552b incident onto the periphery portion 510 of the T-PVH microlens 500.
  • Each of the central portion 552a and the periphery portion 552b may include two orthogonally circularly polarized components: a first circularly polarized component having a first handedness (e.g., left handedness or “L”), and a second circularly polarized component having a second handedness (e.g., right handedness or “R”) opposite to the first handedness.
  • the first circularly polarized component having the first handedness (e.g., left handedness or “L”) of the light 552 includes the first circularly polarized components having the first handedness (e.g., left handedness or “L”) of the central portion 552a and the periphery portion 552b.
  • the second circularly polarized component having the second handedness (e.g., right handedness or “R”) of the light 552 includes the second circularly polarized components having the second handedness (e.g., right handedness or “R”) of central portion 552a and the periphery portion 552b.
  • the light 552 may be an unpolarized light.
  • the light 552 may be or a linearly polarized light.
  • the light 552 may include two orthogonally circularly polarized components: a first circularly polarized component (e.g., an LHCP component) having a first handedness (e.g., left handedness or “L”), and a second circularly polarized component (e.g., an RHCP component) having a second handedness (e.g., right handedness or “R”) opposite to the first handedness.
  • a first circularly polarized component e.g., an LHCP component
  • first handedness e.g., left handedness or “L”
  • RHCP component e.g., right handedness or “R”
  • the first circularly polarized component may include a central portion 552a (L) incident onto the central portion 515 of the T-PVH microlens 500, and a periphery portion 552b (L) incident onto the periphery portion 510 of the T-PVH microlens 500.
  • the second circularly polarized component e.g., RHCP component
  • RHCP component may include a central portion 552a (R) incident onto the central portion 515 of the T-PVH microlens 500, and a periphery portion 552b (R) incident onto the periphery portion 510 of the T-PVH microlens 500.
  • a first portion of the light 552 is defined as the LHCP component (L) of the central portion 552a, i.e., 552a (L) (similar to the central portion 502a of the LHCP light 502 shown in FIG. 5A).
  • a second portion of the light 552 is defined as the RHCP component (R) of the central portion 552a (i.e., 552a (R)) and the entire periphery portion 552b that includes both the LHCP component (L) (i.e., 552b (L)) and the RHCP component (R) (i.e., 552b (R)).
  • the second portion of the light 552 is defined as a combination of the entire RHCP component (R) of the light 552(i.e., 552a (R)) and 552b (R)), and the periphery portion of the LHCP component (L) of the light 552 (i.e., 552b (L)).
  • the incident light 552 is shown in FIG.
  • the incident light 552 may be a non-collimated light.
  • the T-PVH microlens 500 may be configured to transform the first portion of the incident light 552 as a first polarized light 564 (e.g., similar to the focused RHCP light 504a shown in FIG. 5A), and transform the second portion of the incident light 552 as a second polarized light 554 (e.g., similar to a combination of the substantially collimated LHCP light 504b shown in FIG. 5A and the defocused LHCP light 514 shown in FIG. 5B).
  • a first polarized light 564 e.g., similar to the focused RHCP light 504a shown in FIG. 5A
  • the second portion of the incident light 552 e.g., similar to a combination of the substantially collimated LHCP light 504b shown in FIG. 5A and the defocused LHCP light 514 shown in FIG. 5B.
  • Detailed descriptions of the light propagations paths can refer to the above descriptions
  • the first polarized light 564 and the second polarized light 554 may be orthogonally circularly polarized lights.
  • the first polarized light 564 may be an RHCP light
  • the second polarized light 554 may be an LHCP light.
  • the first polarized light 564 may be a focused (or convergent) light output from the central portion 515 of the T-PVH microlens 500
  • the second polarized light 554 may be a defocused (or divergent) light output from both of the central portion 515 and the periphery portion 510 of the T-PVH microlens 500.
  • the T-PVH microlens 500 may focus (or converge) the first portion of the incident light 552 as the first polarized light 564 that is focused to a positive focal point of the T-PVH microlens 500, and defocus (or diverge) the second portion of the incident light 552 as the second polarized light 554.
  • a positive focal point may be referred to as a focal point of a lens that is on the other side of the lens from where an object is placed, or on the light outputting side of the lens, rather than on the light input side of the lens.
  • the first polarized light 564 may be first focused to the positive focal point of the T-PVH microlens 500, then defocused beyond the positive focal point (not shown in FIG. 5C).
  • the T-PVH microlens 500 may be configured to defocus (or diverge) the second portion of the incident light 552 as the second polarized light 554, with a substantially small divergence.
  • the configuration shown in FIG. 5C may be understood as a combination of the configurations shown in FIG. 5 A and FIG. 5B. As shown in FIG.
  • the parameters of the T-PVH microlens 500 may be configured, such that the central portion 515 of the T-PVH microlens 500 may be configured to forwardly diffract and defocus (or diverge) the central portion 512a of the LHCP light 512 as the LHCP light 514a in a substantially small diffraction angle.
  • the periphery portion 510 of the T-PVH microlens 500 may be configured to forwardly diffract and defocus (or diverge) the periphery portion 512b of the LHCP light 512 as the LHCP light 514b in a substantially small diffraction angle.
  • each microlens 421 included in the microlens array (e.g., T-PVH microlens array) 420 may function similar to the T-PVH microlens 500 shown in FIGs. 5A-5C.
  • each microlens 421 may be configured to transform a first portion of an incident light (that is incident onto each microlens) as a first polarized light, and transform a second portion of the incident light as a second polarized light, in a manner similar to that described above in connection with FIGs.
  • the incident light may be a substantially collimated light.
  • the first polarized light may be a focused or convergent light
  • the second polarized light may be a defocused or divergent light.
  • the first polarized light and the second polarized light may be orthogonally circularly polarized lights.
  • the first portion and the second portion of the incident light that is incident onto each microlens may be defined in a manner similar to the first portion and the second portion of the light 552 shown in FIG. 5C.
  • the first portion of the incident light may include an RHCP component (or an LHCP component) of a central portion of the incident light that is incident onto a central portion of each microlens 421.
  • the second portion of the incident light may include the LHCP component (or the RHCP component) of the central portion of the incident light, and a periphery portion (including both the RHCP component and the LHCP component) of the incident light.
  • the second portion of the incident light may include a combination of the entire LHCP component (or the RHCP component) of the incident light and the periphery portion of the RHCP component of the incident light.
  • the first portion of the incident light may include the central portion of the RHCP component (or LHCP component) of the incident light that is incident onto a central portion of each microlens 421.
  • the polarization converter 430 (which may be a patterned polarization converter) may be disposed between the microlens array 420 and the first waveplate 440.
  • the polarization converter 430 may include a plurality of polarization converting segments 431 arranged in an array.
  • the polarization converting segments 431 may be substantially aligned with the microlenses 421, and substantially aligned with the light-emitting elements (or subpixels) 411.
  • Each polarization converting segment 431 may include a converting region (or portion) 435 and a non-converting region (or portion) 433.
  • the non-converting region 433 may be disposed surrounding the converting region 435.
  • a size (or dimension) of the non-converting region 433 may be equal to or greater than a size (or dimension) S of the converting region 435.
  • the converting region 435 may be configured to convert a polarization of a polarized light incident thereon to an orthogonal polarization, while transmitting the polarized light.
  • the non-converting region 433 may be configured to substantially maintain a polarization of a polarized light incident thereon, while transmitting the polarized light.
  • the polarization converting segment 431 may be configured to output two lights having orthogonal polarizations.
  • the polarization converter 430 may include a patterned half-wave plate (“HWP”), in which the converting regions 435 may be configured to provide a half-wave birefringence (or half-wave phase retardance), and the non-converting region 433 may be configured to provide a zero or full wave birefringence (or zero or full wave phase retardance).
  • HWP patterned half-wave plate
  • the converting regions 435 may convert a polarization of a polarized light incident thereon into an orthogonal polarization while transmitting the polarized light, and the non-converting regions 433 may substantially maintain a polarization of a polarized light incident thereon while transmitting the polarized light.
  • the converting regions 435 may be configured to provide a half-wave birefringence (or half-wave phase retardance) across a wide spectral (or wavelength) range (e.g., visible spectrum) and/or a wide incidence angle range.
  • the polarization converter (e.g., patterned HWP) 430 may be broadband.
  • the converting regions 435 may include a multi-layer birefringent material (e.g., a polymer, or an LC material) configured to provide a half-wave birefringence (or half-wave phase retardance) across a wide spectral range and/or a wide incidence angle range.
  • the converting regions 435 of the polarization converting segments 431, which are aligned with subpixels emitting image lights having a predetermined wavelength range may be configured to provide a half wave birefringence (or half-wave phase retardance) for the predetermined wavelength range.
  • the converting regions 435 of the polarization converting segments 431, which are substantially aligned with subpixels emitting image lights having different wavelength ranges may be configured to provide a half-wave birefringence (or half-wave phase retardance) for different wavelength ranges.
  • the converting regions 435 of the polarization converting segments 431, which are aligned with subpixels emitting red, blue, or green lights may be configured to provide a half-wave birefringence (or half-wave phase retardance) for a red, blue, or green wavelength range.
  • the converting regions 435 may include an optically anisotropic (or birefringent) material (e.g., an LC material), and the non-converting regions 433 may include an optically isotropic material (e.g., a glass, a polymer, etc.)
  • both of the converting regions 435 and the non-converting regions 433 may include an optically anisotropic (or birefringent) material (e.g., an LC material).
  • the optically anisotropic molecules e.g., LC molecules
  • the optically anisotropic may be configured with an anti-parallel alignment in the converting regions 435, and have a vertical alignment in the non-converting region 433.
  • At least one of the first waveplate 440 or the second waveplate 460 may function as a QWP. In some embodiments, at least one of the first waveplate 440 or the second waveplate 460 may function as a broadband QWP configured to provide a quarter-wave birefringence (or quarter-wave phase retardance) across a wide spectral (or wavelength) range (e.g., visible spectrum) and/or a wide incidence angle range.
  • At least one of the first waveplate 440 or the second waveplate 460 may include a multi-layer birefringent material (e.g., a polymer, or an LC material) configured to provide a half-wave birefringence (or half wave phase retardance) across a wide spectral range (e.g., visible spectrum) and/or a wide incidence angle range.
  • the polarizer 450 may be disposed between the first waveplate 440 and the second waveplate 460, and may be a linear absorption polarizer.
  • the combination of the first waveplate (e.g., QWP) 440, the polarizer (e.g., linear absorption polarizer) 450, and the second waveplate (e.g., QWP) 460 may function as a circular polarizer 470 (e.g., an absorption type), e.g., across a wide spectral range and/or a wide incidence angle range.
  • a circular polarizer 470 e.g., an absorption type
  • FIG. 4A the first waveplate 440, the polarizer 450, and the second waveplate 460 are shown as spaced apart from one another by a gap. In some embodiments, the first waveplate 440, the polarizer 450, and the second waveplate 460 may be stacked without a gap. In the embodiment shown in FIG. 4A, the first waveplate 440 is shown as spaced apart from the polarization converter 430 by a gap. In some embodiments, the first waveplate 440 and the polarization converter 430 may be stacked without a gap.
  • FIGs. 4A-4C show an optical path of an image light 471 in the display device 400, according to an embodiment of the present disclosure. For discussion purposes, FIGs.
  • FIGs. 4A-4C show the optical path of the image light 471 in a portion of the display device 400 corresponding to a single light-emitting element 411.
  • Optical paths of the image light 471 in the entire display device 400 may be substantially the same as that shown in FIGs. 4A-4C.
  • R denotes an RHCP light
  • L denotes an LHCP light
  • s denotes an s- polarized light
  • p denotes a p-polarized light.
  • An s-polarized light and a p-polarized light are linearly polarized lights with orthogonal polarizations.
  • An RHCP light and an LHCP light are circularly polarized lights with orthogonal polarizations.
  • the light-emitting elements 411 of the display panel 410 may be configured to emit lights (e.g., image lights) in both forward and backward directions.
  • the image lights may be linearly polarized lights or unpolarized lights.
  • the light-emitting elements 411 may emit the image light 471 in a forward direction toward the microlens array 420 (e.g., T-PVH microlens array), and emit an image light 472 in a backward direction.
  • the image light 471 and the image light 472 may be unpolarized lights including an RHCP component and an LHCP component.
  • the image light 471 may be incident onto both a central portion and a periphery portion of the microlens 421.
  • the microlens array 420 may be configured to transform (e.g., via forward diffraction) a first portion of the image light 471 to a first polarized light (e.g., an RHCP light) 473, and transform (e.g., via forward diffraction and/or transmission with negligible diffraction) a second portion of the image light 471 to a second polarized light (e.g., an LHCP light) 474.
  • the first portion and the second portion of the image light 471 may be defined in a manner similar to the first portion and the second portion of the light 552 (shown in FIG. 5C), as described above.
  • the first polarized light (e.g., RHCP light) 473 may be a focused or convergent light that is focused to a point “O” on an optical axis of the microlens 421.
  • the point “O” may be within a plane 465 that is perpendicular to the optical axis of the microlens 421.
  • the plane 465 may be referred to as an image plane of the microlens array 420.
  • the image light 471 output from the display panel 410 may be a substantially collimated light, e.g., a fully collimated light or anon-fully collimated light with a negligible divergence.
  • the point O may be at or in proximity to a positive focal point of the microlens 421
  • the image plane 465 may be at or in proximity to a positive focal plane of the microlens array 420.
  • the second polarized light (e.g., LHCP light) 474 may be a defocused or divergent light.
  • the first polarized light (e.g., RHCP light) 473 and the second polarized light (e.g., LHCP light) 474 may be orthogonally circularly polarized lights.
  • the microlens array 420 may be configured with a high diffraction efficiency at both of the central portion and the peripherical portion of the microlenses 421, e.g., an efficiency greater than 95%.
  • a combination of the first polarized light (e.g., RHCP light) 473 and the second polarized light (e.g., LHCP light) 474 output from the microlens array 420 may have an energy that is substantially the same as the energy of the image light 471.
  • the energy of the first polarized light 473 may be smaller than the energy of the second polarized light 474.
  • the first polarized light 473 and the second polarized light 474 may propagate toward the polarization converter 430.
  • the polarization converter 430 may be spaced apart from the microlens array 420 by a distance d.
  • a beam size of the second polarized light 474 may be configured to be the same as or smaller than a size of the polarization converting segment 431, and greater than a size of the converting region 435 of the polarization converting segment 431.
  • the second polarized light 474 may be incident onto both of the converting region 435 and the non-converting region 433 of the polarization converting segment 431.
  • a beam size of the first polarized light 473 may be configured to be the same as or smaller than a size of the converting region 435 of the polarization converting segment 431.
  • the first polarized light 473 may be incident onto the converting region 435 of the polarization converting segment 431, and may not be incident onto the non-converting region 433 of the polarization converting segment 431.
  • the beam size of the first polarized light 473 may be configured to be smaller than the beam size of the second polarized light 474.
  • the microlens array 420 may be configured to transform the first portion of the image light 471 as the first polarized light 473 that is incident onto the converting region 435 of the polarization converting segment 431.
  • the microlens array 420 may transform the second portion of the image light 471 as the second polarized light 474 that is incident onto both of the converting region 435 and the non-converting region 433 of the polarization converting segment 431.
  • the polarization converting segment 431 may be configured with a first circular shape having a first radius
  • the converting region 435 may be configured with a second circular shape having a second radius that is smaller than the first radius.
  • the beam spot of the second polarized light 474 at a plane intersecting both of the converting region 435 and the non-converting region 433 may be configured with a third circular shape having a third radius.
  • the beam spot of the first polarized light 473 at a plane intersecting the converting region 435 may be configured with a fourth circular shape having a fourth radius.
  • the third radius may be the same as or smaller than the first radius, and greater than the second radius.
  • the fourth radius may be smaller than the third radius.
  • the fourth radius may be the same as or smaller than the second radius.
  • FIG. 4B illustrates an optical path of the first polarized light (e.g., RHCP light) 473 output from the microlens array 420.
  • the substantially entire first polarized light 473 may be incident onto the converting region 435 of the polarization converting segment 431, and no portion (or only a negligible portion) of the first polarized light 473 is incident onto the non-converting region 433 of the polarization converting segment 431.
  • the converting region 435 may be configured to convert the polarization of the first polarized light 473 into an orthogonal polarization while transmitting the first polarized light 473.
  • the converting region 435 may output a circularly polarized light (e.g., an LHCP) light 475 propagating toward the circular polarizer 470.
  • the circular polarizer 470 may be configured to substantially transmit an LHCP light and substantially block an RHCP light via absorption.
  • the circular polarizer 470 may substantially transmit the circularly polarized light 475 as a circularly polarized light (e.g., an LHCP light) 481.
  • the circularly polarized light 481 may propagate toward a viewer of the display device 400.
  • the first waveplate 440 may be configured to convert the circularly polarized light 475 into a linearly polarized light (e.g., an s-polarized light) 477 propagating toward the polarizer 450.
  • the polarizer 450 may be configured to substantially transmit an s-polarized light and substantially block a p-polarized light.
  • the polarizer 450 may be configured to substantially transmit the s-polarized light477 as an s-polarized light 479 propagating toward the second waveplate 460.
  • the second waveplate 460 may be configured to convert the s-polarized light 479 into the circularly polarized light (e.g., LHCP light) 481.
  • the circularly polarized light 475 output from the converting region 435 of the polarization converter 430 may be output from the display device 400 as the circularly polarized light 481 that may be perceived by the viewer.
  • substantially the entire first polarized light (e.g., RHCP light) 473 output from the microlens array 420 may be delivered to the viewer.
  • the first portion of the image light 471 that is transformed to the first polarized light 473 by the microlens array 420 may be substantially entirely delivered to the viewer.
  • the circularly polarized light 481 output from the display device 400 is presumed to have an energy that is substantially the same as the first portion of the image light 471.
  • FIG. 4C illustrates an optical path of the second polarized light (e.g., LHCP light) 474 output from the microlens array 420 (e.g., T-PVH microlens array).
  • the microlens array 420 e.g., T-PVH microlens array.
  • the second polarized light 474 output from the microlens array 420 may be incident onto both of the converting region 435 and the corresponding non-converting region 433 of the polarization converting segment 431.
  • the second polarized light 474 may include a central portion that is incident onto the converting region 435, and a periphery portion that is incident onto the corresponding non-converting region 433 surrounding the converting region 435.
  • the converting region 435 may be configured to convert the polarization of the central portion of the second polarized light 474 into an orthogonal polarization, while transmitting the central portion of the second polarized light 474.
  • the converting region 435 may be configured to output a circularly polarized light (e.g., an RHCP) light 478 toward the circular polarizer 470.
  • the non-converting region 433 may be configured to substantially maintain the polarization of the periphery portion of the second polarized light 474, and may output a circularly polarized light (e.g., an LHCP light) 476 toward the circular polarizer 470.
  • the circular polarizer 470 may substantially transmit the circularly polarized light 476 as a circularly polarized light (e.g., an LHCP light) 486 propagating toward the viewer of the display device 400, and substantially block the circularly polarized light (e.g., RHCP light) 478.
  • a circularly polarized light e.g., an LHCP light
  • RHCP light substantially block the circularly polarized light
  • the first waveplate 440 may be configured to convert the circularly polarized light 476 and the circularly polarized light 478 into a linearly polarized light (e.g., an s-polarized light) 480 and a linearly polarized light (e.g., a p-polarized light) 482, respectively.
  • the polarizer (450 may be configured to substantially transmit an s-polarized light and substantially block a p-polarized light
  • the polarizer 450 may substantially transmit the s-polarized light 480 as an s-polarized light 484 propagating toward the second waveplate 460, and substantially block the p-polarized light 482 via absorption.
  • the second waveplate 460 may be configured to convert the s-polarized light 484 into the circularly polarized light (e.g., LHCP light) 486, while transmitting the s- polarized light 484.
  • the circularly polarized light (e.g., LHCP light) 476 output from the non converting region 433 of the polarization converter 430 may be delivered to the viewer.
  • the central portion of the second polarized light (e.g., LHCP light) 474 output from the microlens array 420 may not be output by the display device 400, while the periphery portion of the second polarized light 474 may be output by the display device 400, and delivered to the viewer, as shown in FIGs. 4A and 4C.
  • the central portion of the second portion of the image light 471 emitted from the display panel 410 may not be output by the display device 400, while the periphery portion of the second portion of the image light 471 may be output by the display device 400 and delivered to the viewer.
  • the display device 400 may be configured to output the first portion of the image light 471 as the circularly polarized light (e.g., LHCP light) 481, the first portion being the LHCP component of the central portion of the image light 471.
  • the display device 400 may be configured to output the periphery portion of the second portion of the image light 471 as the circularly polarized light (e.g., LHCP light) 486, the second portion being a combination of the RHCP component of the central portion of the image light 471 and the periphery portion of the image light 471 including both the LHCP component and the RHCP component.
  • an overall output light 488 of the display device 400 may include the circularly polarized light (e.g., LHCP light) 481 and the circularly polarized light (e.g., LHCP light) 486.
  • the circularly polarized light e.g., LHCP light
  • the circularly polarized light e.g., LHCP light
  • the microlens array 420 may be configured to defocus (or diverge) the second portion of the image light 471 as the second polarized light (e.g., LHCP light) 474, with a substantially small divergence, which may be desirable for high resolution displays.
  • the parameters of the microlens array 420 may be configured, such that the microlens array 420 may transform (e.g., via forward diffraction and/or transmission with negligible diffraction) the second portion of the image light 471 to the second polarized light (e.g., LHCP light) 474 in a substantially small diffraction angle.
  • the transmittance or efficiency may be no more than 50%.
  • the disclosed display device can provide a transmittance or efficiency greater than 50%.
  • the circularly polarized light (e.g., LHCP light) 481 output by the display device 400 is presumed to have an energy that is substantially the same as the energy of the first portion of the image light 471.
  • the circularly polarized light (e.g., LHCP light) 486 output by the display device 400 is presumed to have an energy that is substantially the same as the energy of the periphery portion of the second portion of the image light 471.
  • the overall output light 488 may have an energy that is greater than half (or 50%) of the energy of the image light 471.
  • the overall output light 488 may have an energy that is about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55% of the energy of the image light 471.
  • a reflective electrode (not shown) may be disposed at the bottom of the light-emitting elements 411 (referred to as a bottom reflective electrode).
  • the reflective electrode may be configured to reflect the image light 472 back to the microlens array 420.
  • the image light 472 may also be output by the display device 400.
  • the reflected light (not shown) from the reflective electrode may have an optical path that is similar to that of the image light 471 when the reflected light propagates through the microlens array 420, the polarization converter 430, and the circular polarizer 470.
  • an overall output light of the display device 400 corresponding to the image light 472 may have an energy that is greater than half (or 50%) of the energy of the image light 472, such as about 95%, 90%,
  • an overall output light of the display device 400 may have an energy that is greater than half (or 50%) of the energy of the overall image light, such as about 95%,
  • the overall light transmittance of the display device 400 may be greater than 50%, such as 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55%.
  • the overall light transmittance of the display device 400 may be determined, in part, by the size S of the converting region 435 included in the polarization converter 430, and the distance d between the polarization converter 430 and the microlens array 420.
  • the beam size of the first polarized light (e.g., focused RHCP light) 473 at a plane intersecting the polarization converting segment 431 may be configured to be substantially the same as (e.g., equal to or slightly smaller than) the size (or dimension) S of the converting region 435.
  • the beam size of the second polarized light (e.g., defocused LHCP light) 474 at a plane intersecting the polarization converting segment 431 may be configured to be larger than the size S of the converting region 435, and the same as or smaller than the size of the polarization converting segment 431. As the distance d increases (e.g. when the polarization converter 430 moves away from the microlens array 420), the converting region 435 having a reduced size S may be used.
  • the energy of the circularly polarized light (e.g., LHCP light) 481 output from the display device 400 may be substantially unchanged as the distance d varies, while the energy of the circularly polarized light (e.g., LHCP light) 486 output from the display device 400 may increase, as the central portion of the defocused light 474 that is absorbed by the polarizer 450 is reduced. Thus, the energy of the overall output light 488 of the display device 400 may increase.
  • the polarization converter 430 may be disposed substantially at (e.g., within a predetermined range of distance from) the image plane 465 of the microlens array 420.
  • the converting region 435 having a predetermined minimum size may be used.
  • the energy of the overall output light 488 of the display device 400 may have a predetermined maximum value.
  • the converting region 435 and the beam spot of the focused light 473 at a plane intersecting the polarization converter 430 may be aligned with one another at a high accuracy.
  • the polarization converter 430 may be disposed adjacent the image plane 465 of the microlens array 420, for example, within a predetermined distance range of the image plane 465. For example, when the distance between the image plane 465 and the microlens array 420 is D, the distance d between the polarization converter 430 and the microlens array 420 may be configured to be within a predetermined percentage of the distance D.
  • the predetermined percentage may be about 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%.
  • the image plane 465 of the microlens array 420 may be the positive focal plane of the microlens array 420, and the distance D between the image plane 465 and microlens array 420 may be a focal length of the microlens array 420.
  • FIG. 6 schematically illustrates an optical path of an image light in a conventional emissive display device 600.
  • the conventional emissive display device 600 may include a display panel 610, and a circular polarizer 670 laminated over the display panel 610.
  • the circular polarizer 670 may include a waveplate 640 and a linear polarizer 650.
  • the display panel 610 may include a plurality of light-emitting elements 611. Each light-emitting element 611 may include a light-emitting area 615 and a non-emitting area 613 surrounding the light-emitting area 615.
  • the circular polarizer 670 may be configured to block the reflected ambient light from the bottom reflective electrode (not shown) of the light-emitting elements 611 in the display panel 610.
  • the conventional emissive display device 600 may not include the microlens assembly 420 and the polarization converter 430 shown in FIGs. 4A-4C. At least half of the energy of an image light 671 (and an image light 672) emitted from the display panel 610 (in the forward direction and the backward direction) may be absorbed by the circular polarizer 670.
  • an overall light transmittance of the conventional emissive display device 600 may be less than 50%. In other words, the power efficiency of the conventional emissive display device 600 may be less than 50%.
  • the disclosed display device 400 shown in FIGs. 4A-4C may include the microlens array 420 (e.g., T-PVH microlens array) and the polarization converter 430 (which may be a patterned polarization converter) disposed between the display panel 410 and the circular polarizer 470.
  • the microlens array 420 and the polarization converter 430 may be referred to as a polarization converting device.
  • the microlens array 420 may be configured to output the focused light 473 and the defocused light 474 with a high diffraction efficiency (e.g., larger than 95%) from the center to the peripheries of the microlens 421.
  • the display device 400 disclosed herein may be configured to provide an overall light transmittance that is greater than 50%.
  • the overall light transmittance of the display device 400 disclosed herein may be 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55%.
  • the power efficiency of the display device 400 may be significantly increased as compared to a conventional emissive display device.
  • the microlens array 420 may enlarge an emission cone of the light-emitting elements 411 of the display panel 410, thereby expanding an eye-box of the display device 400.
  • FIG. 4D schematically illustrates a y-z sectional view of a display device 455, according to an embodiment of the present disclosure.
  • the display device 455 may include elements, structures, and/or functions that are the same as or similar to those included in the display device 400 shown in FIGs. 4A-4C. Descriptions of the same or similar elements, structures, and/or functions can refer to the above descriptions rendered in connection with FIGs. 4A-4C.
  • the display device 455 may include the display panel 410, the microlens array 420, the polarization converter 430 (which may be a patterned polarization converter), the polarizer 450, and the second waveplate 460 arranged in an optical series.
  • the polarization converter 430 which may be a patterned polarization converter
  • the display panel 410, the microlens array 420, the polarization converter 430, the polarizer 450, and the second waveplate 460 are shown as having flat surfaces.
  • one or more of the display panel 410, the microlens array 420, the polarization converter 430, the polarizer 450, and the second waveplate 460 may have curved surfaces.
  • the microlens array 420 may be linear polarization selective.
  • the microlens array 420 may be a liquid crystal microlens array configured to focus a first linearly polarized light with a predetermined polarization direction, and transmit a second linearly polarized light with a polarization direction that is orthogonal to the predetermined polarization direction.
  • the microlens array 420 may be configured to change a propagation direction and a wavefront of the first linearly polarized light while transmitting the first linearly polarized light, and substantially maintain a propagation direction and a wavefront of the second linearly polarized light, while transmitting the second linearly polarized light.
  • the microlens array 420 may be configured to focus one of the two orthogonally linearly polarized components and output a focused light, and transmit the other one of the two orthogonally linearly polarized components and output an unfocused light.
  • the microlens array 420 may substantially maintain the polarization of the two orthogonally linearly polarized components, while transmitting the two orthogonally linearly polarized components.
  • FIG. 4D illustrates an optical path of the image light 471 in the display device 455 according to an embodiment of the present discourse.
  • FIG. 4D shows the optical path of the image light 471 in a portion of the display device 455 corresponding to a single light-emitting element 411.
  • Optical paths of the image light in the other portions of the display device 455 corresponding to other light emitting elements may be substantially the same as that shown in FIG. 4D.
  • “L” denotes an LHCP light
  • s denotes an s-polarized light
  • p denotes a p-polarized light.
  • An s-polarized light and a p-polarized light are orthogonally linearly polarized lights.
  • the image light 471 may be an unpolarized light and may be substantially collimated.
  • the microlens array 420 may be configured to transform a first portion of the image light 471 as a first polarized light 491, and transform a second portion of the image light 471 as a second polarized light 490.
  • the first portion of the image light 471 may be a p-polarized component of the image light 471
  • the second portion of the image light 471 may be an s-polarized component of the image light 471.
  • the first polarized light 491 may be a focused (or convergent) light
  • the second polarized light 491 may be an unfocused (or substantially collimated) light.
  • the microlens array 420 may be configured to focus (or converge) the first portion of the image light 471 (e.g., p-polarized component of the image light 471) as the first polarized light (e.g., focused (or convergent)) light 491.
  • the microlens array 420 may substantially transmit, without negligible converging or diverging effect, the second portion of the image light 471 (e.g., s-polarized component of the light 471) as the second polarized light (e.g., unfocused light 490).
  • the first polarized light (e.g. focused light) 491 output from the microlens array 420 may be a linearly polarized light (e.g., a p-polarized light), which may be referred to as a p-polarized light 491 for discussion purposes.
  • the second polarized light (e.g., unfocused light) 490 output from the microlens array 420 may be a linearly polarized light (e.g., an s-polarized light), which may be referred to as an s-polarized light 490 for discussion purposes.
  • the energies of the p-polarized light 491 and the s-polarized light 490 output from the microlens array 420 may be substantially the same, e.g., about 50% of the energy of the light 471 output from the display panel 410.
  • substantially the entire linearly polarized light (e.g., p- polarized light) 491 output from the microlens array 420 may be incident onto the converting region 435 of the polarization converting segment 431, and may not be incident onto the non converting region 433 of the polarization converting segment 431.
  • the converting region 435 may be configured to convert the polarization of the p-polarized light 491 into an orthogonal polarization (i.e., s-polarization) while transmitting the p-polarized light 491.
  • the converting region 435 may output an s-polarized light 493 toward the polarizer (e.g., linear absorption polarizer) 450.
  • the polarizer 450 may be configured to substantially transmit an s-polarized light and substantially block (e.g., via absorption) a p-polarized light. Thus, the polarizer 450 may substantially transmit the s-polarized light 493 as an s-polarized light 495 propagating toward the second waveplate 460.
  • the second waveplate 460 may be configured to convert the s-polarized light 495 into a circularly polarized light (e.g., LHCP light) 497 propagating toward a viewer of the display device 455, while transmitting the s-polarized light 495.
  • the combination of the linear absorption polarizer 450 and the second waveplate 460 may also be referred to as a circular polarizer (e.g., circular absorption polarizer) 489.
  • the linearly polarized light (e.g., s-polarized light) 493 output from the converting region 435 of the polarization converter 430 may be delivered to the viewer.
  • the p-polarized light 491 output from the microlens array 420 may be output by the display device 455, and may be perceived by the viewer.
  • the first portion (e.g., the p-polarized component) of the image light 471 emitted from the display panel 410 may be output by the display device 455, and may be perceived by the viewer.
  • the first portion (e.g., the p-polarized component) of the image light 471 may include half (or 50%) of the energy of the image light 471.
  • the circularly polarized light (e.g., LHCP light) 497 output from the display device 455 is presumed to have an energy that is substantially the same as the energy of the first portion (e.g., the p-polarized component) of the image light 471.
  • the circularly polarized light (e.g., LHCP light) 497 may include half (or 50%) of the energy of the image light 471.
  • the linearly polarized light (e.g., s-polarized light) 490 output from the microlens array 420 may be incident on both of the converting region 435 and the non-converting region 433 of the polarization converting segment 431.
  • the s-polarized light 490 may include a central portion that is incident onto the converting region 435, and a periphery portion that is incident onto the non-converting region 433.
  • the converting region 435 may be configured to convert the polarization of the central portion of the s-polarized light 490 into an orthogonal polarization (i.e., the p-polarization) while transmitting the central portion of the s-polarized light 490.
  • the converting region 435 may output a linearly polarized light (e.g., a p-polarized light) 494 toward the polarizer 450.
  • the non-converting region 433 may be configured to substantially maintain the polarization of the periphery portion of the s- polarized light 490, and output a linearly polarized light (e.g., an s-polarized light) 492 propagating toward the polarizer 450.
  • the polarizer 450 may be configured to substantially transmit an s-polarized light and substantially block a p-polarized light
  • the polarizer 450 may transmit the s- polarized light 492 as an s-polarized light 496 propagating toward the second waveplate 460, and may substantially block the p-polarized light 494 via absorption.
  • the second waveplate 460 may be configured to convert the s-polarized light 496 into an LHCP light 498, while transmitting the s-polarized light 496.
  • the s-polarized light 492 output from the non-converting region 433 of the polarization converting segment 431 may be output by the display device 455 as the LHCP light 498, which may be perceived by a viewer.
  • the periphery portion of the s-polarized light 490 output from the microlens array 420 may be output by the display device 455 as the LHCP light 498, which may be perceived by the viewer.
  • a central portion of the second portion (e.g., the s-polarized component) of the image light 471 emitted from the display panel 410 may not be output by the display device 455, while a periphery portion of the second portion (e.g., s-polarized component) of the image light 471 may be output from by display device 455 as the LHCP light 498, which may be perceived by the viewer.
  • the periphery portion of the second portion (e.g., s- polarized component) of the image light 471 may have an energy that is less than half (or 50%) of the energy of the image light 471 and greater than zero.
  • the LHCP light 498 output from the display device 455 is presumed to have an energy that is substantially the same as the energy of the periphery portion of the second portion of the image light 471.
  • the LHCP light 498 output from the display device 455 may have an energy that is less than half (or 50%) of the energy of the image light 471 and greater than zero.
  • the LHCP light 498 output from the display device 455 may have an energy that is about 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5% of the energy of the image light 471.
  • the display device 455 may be configured to output the first portion (e.g., p- polarized component) of the image light 471 as the LHCP light 497, and output the periphery portion of the second portion (e.g., s-polarized component) of the image light 471 as the LHCP light 498.
  • the LHCP light 497 may have an energy that is substantially half (or 50%) of the energy of the image light 471.
  • the LHCP light 498 may have an energy that is less than half (or 50%) of the energy of the image light 471 and greater than zero.
  • an overall output light 499 of the display device 455 may include the LHCP light 497 and the LHCP light 498.
  • the overall output light 499 may have an energy that is greater than half (or 50%) of the energy of the image light 471.
  • the overall output light 499 may have an energy that is about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55% of the energy of the image light 471.
  • the image light 472 emitted from the light- emitting elements 411 in the backward direction may be reflected by the reflective electrode disposed at the bottom of the display panel 410 back to the microlens array 420.
  • the reflected light (not shown) may have an optical path that is similar to that of the image light 471 when propagating through the microlens array 420, the polarization converter 430, the polarizer 450, and the second waveplate 460.
  • the overall light transmittance of the display device 455 may be determined, in part, by the size S of the converting region 435 included in the polarization converter 430, and the distance d between the polarization converter 430 and the microlens array 420.
  • the beam size of the focused light 491 at a plane intersecting the polarization converting segment 431 may be configured to be the same as or slightly smaller than the size (or dimension) S of the converting region 435.
  • the beam size of the unfocused light 490 at a plane intersecting the polarization converting segment 431 may be configured to be larger than the size (or dimension) S of the converting region 435, and the same as or smaller than the size (or dimension) of the polarization converting segment 431.
  • a reduced size S may be used for the converting region 435.
  • the energy of the circularly polarized light (e.g., LHCP light) 497 output from the display device 455 may be substantially unchanged as the distance d varies.
  • the energy of the circularly polarized light (e.g., LHCP light) 498 output from the display device 455 may increase, as the central portion of the unfocused light 490 that is absorbed by the polarizer 450 is reduced. Thus, the energy of the overall output light 499 of the display device 455 may increase.
  • LHCP light circularly polarized light
  • the disclosed display device 455 shown in FIG. 4D may be configured to provide an overall light transmittance that is greater than 50%. For example, through configuring the size of the converting region 435 included in the polarization converter 430, and the distance d between the polarization converter 430 and the microlens array 420, the overall light transmittance of the disclosed display device 455 may be configured to be 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55%.
  • the disclosed display device 455 may provide a significantly increased power efficiency as compared to the conventional emissive display device 600 shown in FIG. 6.
  • the microlens array 420 is shown to be a spherical microlens array, which is for illustrative purposes.
  • the microlens array 420 may be a spherical microlens array, an aspherical microlens array, a cylindrical microlens array, or a freeform microlens array, etc.
  • the microlens 421 may be a spherical microlens, an aspherical microlens, a cylindrical microlens, or a freeform microlens, etc.
  • the microlens array 420 may be fabricated using any suitable fabrication method, such as holographic interference, laser direct writing, ink-jet printing, or various other forms of lithography.
  • a photo-alignment material may be disposed at the display panel 410 and optically patterned (e.g., via a polarization interference) to form an alignment layer corresponding to a desirable microlens array.
  • a polymerizable LC material may be disposed on the alignment layer, and aligned by the alignment layer to form the desirable microlens array.
  • the LC material may be further polymerized to stabilize the microlens array.
  • a birefringent photo- refractive holographic material other than the LC material may be disposed at the display panel 410 and optically patterned (e.g., via a polarization interference) to form a desirable microlens array directly.
  • the above-mentioned steps may be repeated to fabricate a plurality of microlens arrays on the display panel 410.
  • the microlens array may be fabricated “in- cell” with an alignment offset (or alignment displacement) of less than or equal to 2 pm (or 1 pm, or 100 nm) with respect to the array of the light-emitting elements (or subpixels) 411.
  • two-photon polarization laser writing may be used to fabricate a freeform microlens array.
  • the disclosed display systems with improved resolution, light transmittance and power efficiency may have numerous applications in a large variety of fields, e.g., near-eye displays (“NEDs”), head-up displays (“HUDs”), head-mounted displays (“HMDs”), smart phones, laptops, televisions, monitors, projectors, vehicles, etc.
  • NEDs near-eye displays
  • HUDs head-up displays
  • HMDs head-mounted displays
  • smart phones laptops
  • laptops televisions, monitors, projectors, vehicles, etc.
  • the display devices disclosed herein may be implemented into an optical system to boost the display brightness, improve the battery time, and reduce the ghost images and increase the contrast ratio in a bright environment.
  • AR augmented reality
  • VR virtual reality
  • MR mixed reality
  • NEDs Near-eye displays
  • One application of NEDs is to realize VR, AR, MR or some combination thereof.
  • Desirable characteristics of NEDs include compactness, light weight, high resolution, large field of view (“FOV”), and small form factor.
  • An NED may include a display element configured to generate an image light and a lens system configured to direct the image light toward eyes of a user.
  • the lens system may include a plurality of optical elements, such as lenses, waveplates, reflectors, etc., for focusing the image light to the eyes of the user.
  • an NED may adopt a pancake lens assembly in the lens system to fold the optical path, thereby reducing a back focal distance in the NED.
  • FIG. 8A illustrates a schematic diagram of an optical system 800 according to an embodiment of the present disclosure.
  • the optical system 800 may include a display device 850, and a pancake lens assembly 801 coupled to the display device 850.
  • the display device 850 may be configured to display a virtual image with high brightness and contrast ratio.
  • the display device 850 may be a monochromatic display device, e.g., a red, green, or blue display device.
  • the display device 850 may be a polychromatic display device, e.g., a red-green-blue (“RGB”) display device.
  • RGB red-green-blue
  • the display device 850 may be a polychromatic display device including a stack of a plurality of monochromatic displays, e.g., an RGB display device including a stack of red, green, and blue display devices.
  • the display device 850 may be an embodiment of the display devices disclosed herein, such as the display device 100 shown in FIG. 1A, the display device 190 shown in FIG. 1G, the display device 400 shown in FIG. 4A, or the display device 455 shown in FIG. 4D.
  • the display device 850 may be configured to output a polarized image light 821 (that forms the virtual image) toward the pancake lens assembly 801.
  • the pancake lens assembly 801 may be configured to focus the polarized image light 821 to an eye-box located at an exit pupil 860.
  • the exit pupil 860 may be at a location where an eye 865 is positioned in an eye-box region when a user wears the NED.
  • the pancake lens assembly 801 may include a first optical element 805 and a second optical element 810.
  • the pancake lens assembly 801 may be configured as a monolithic pancake lens assembly without any air gaps between optical elements included in the pancake lens assembly.
  • one or more surfaces of the first optical element 805 and the second optical element 810 may be shaped (e.g., curved) to compensate for the field curvature.
  • one or more surfaces of the first optical element 805 and/or the second optical element 810 may be shaped to be spherically concave (e.g., a portion of a sphere), spherically convex, a rotationally symmetric asphere, a freeform shape, or some other shape that can mitigate the field curvature.
  • the shape of one or more surfaces of the first optical element 805 and/or the second optical element 810 may be designed to additionally compensate for other forms of optical aberration.
  • one or more of the optical elements within the pancake lens assembly 801 may have one or more coatings, such as an anti -reflective coating, configured to reduce ghost images and enhance contrast.
  • the first optical element 805 and the second optical element 810 may be coupled together by an adhesive 815.
  • Each of the first optical element 805 and the second optical element 810 may include one or more optical lenses.
  • at least one of the first optical element 805 or the second optical element 810 may have at least one flat surface.
  • the first optical element 805 may include a first surface 805-1 facing the display device 850 and an opposing second surface 805-2 facing the eye 865.
  • the first optical element 805 may be configured to receive an image light from the display device 850 at the first surface 805-1 and output an image light with an altered property at the second surface 805-2.
  • the pancake lens assembly 801 may also include a mirror 806 that may be an individual layer, film, or coating disposed at (e.g., bonded to or formed at) the first optical element 805.
  • the mirror 806 may be disposed at (e.g., bonded to or formed at) the first surface 805-1 or the second surface 805-2 of the first optical element 805.
  • FIG. 8 A shows that the mirror 806 is disposed at (e.g., bonded to or formed at) the first surface 805-1.
  • the mirror 806 may be disposed at the second surface 805-2 of the first optical element 805.
  • the mirror 806 may be a partial reflector that is partially reflective to reflect a portion of a received light.
  • the mirror 806 may be configured to transmit about 50% and reflect about 50% of a received light, and may be referred to as a “50/50 mirror.”
  • the second optical element 810 may have a first surface 810-1 facing the first optical element 805 and an opposing second surface 810-2 facing the eye 865.
  • the pancake lens assembly 801 may also include a linear reflective polarizer 808, which may be an individual layer, film, or coating disposed at (e.g., bonded to or formed at) the second optical element 810.
  • the linear reflective polarizer 808 may be disposed at (e.g., bonded to or formed at) the first surface 810-1 or the second surface 810-2 of the second optical element 810 and may receive a light output from the mirror 806.
  • FIG. 8A shows that the linear reflective polarizer 808 is disposed at (e.g., bonded to or formed at) the first surface 810-1 of the second optical element 810. That is, the linear reflective polarizer 808 may be disposed between the first optical element 805 and the second optical element 810.
  • the linear reflective polarizer 808 may be disposed at the second surface 810-2 of the second optical element 810.
  • the pancake lens assembly 801 shown in FIG. 8A is for illustrative purposes.
  • one or more of the first surface 805-1 and the second surface 805-2 of the first optical element 805 and the first surface 810-1 and the second surface 810-2 of the second optical element 810 may be curved surface(s) or flat surface(s).
  • the pancake lens assembly 801 may have one optical element or more than two optical elements.
  • FIG. 8B illustrates a schematic cross-sectional view of an optical path 880 of an image light propagating in the pancake lens assembly 801 shown in FIG. 8A, according to an embodiment of the present disclosure.
  • the first optical element 805 and the second optical element 810 which are presumed to be lenses that do not affect the polarization of the light, are omitted for the simplicity of illustration.
  • “s” denotes an s-polarized light
  • “p” denotes a p-polarized light.
  • the display device 850, the mirror 806, and the linear reflective polarizer 808 are illustrated as flat surfaces in FIG. 8B.
  • one or more of the display device 850, the mirror 806, and the linear reflective polarizer 808 may include a curved surface.
  • the display device 850 may output a p-polarized image light 82 lp covering a predetermined spectrum, such as a portion of the visible spectral range or substantially the entire visible spectral range.
  • the mirror 806 may reflect a first portion of the p-polarized image light 821p as an s-polarized image light 823s toward the display device 850, and transmit a second portion of the p-polarized image light 821p as a p-polarized image light 825p toward the linear reflective polarizer 808.
  • the s-polarized image light 823s may be absorbed by a linear polarizer (e.g., similar to the linear polarizer 130 shown in FIGs.
  • the linear reflective polarizer 808 may be configured to substantially reflect a p-polarized light, and substantially transmit an s- polarized light.
  • the linear reflective polarizer 808 may reflect the p-polarized image light 825p as a p-polarized image light 827p back toward the mirror 806.
  • the mirror 806 may reflect the p-polarized image light 827p as an s-polarized image light 829s toward the linear reflective polarizer 808, which may be transmitted through the linear reflective polarizer 808 as an s-polarized image light 831s.
  • the s-polarized image light 831s may be focused onto the eye 865.
  • FIG. 7A illustrates a schematic diagram of a near-eye display (“NED”) 700 according to an embodiment of the disclosure.
  • FIG. 7B is a cross-sectional view of half of the NED 700 shown in FIG. 7A according to an embodiment of the disclosure.
  • FIG. 7B shows the cross-sectional view associated with a left-eye display system 710L.
  • the NED 700 may include a controller (e.g., the controller 217), which is not shown in FIG. 7A or 7B.
  • the NED 700 may include a frame 705 configured to mount to a user’s head.
  • the frame 705 is merely an example structure to which various components of the NED 700 may be mounted. Other suitable fixtures may be used in place of or in combination with the frame 705.
  • the NED 700 may include right-eye and left-eye display systems 71 OR and 710L mounted to the frame 705.
  • the NED 700 may function as a VR device, an AR device, an MR device, or any combination thereof.
  • the right-eye and left-eye display systems 71 OR and 710L may be entirely or partially transparent from the perspective of the user, which may provide the user with a view of a surrounding real-world environment.
  • the NED 700 when the NED 700 functions as a VR device, the right-eye and left-eye display systems 71 OR and 710L may be opaque, such that the user may be immersed in the VR imagery based on computer-generated images.
  • the right-eye and left-eye display systems 71 OR and 710L may include image display components configured to project computer-generated virtual images into left and right display windows 715L and 715R in a field of view (“FOV”).
  • the right-eye and left-eye display systems 71 OR and 710L may include any disclosed display devices, such as the display device 100 shown in FIG. 1A, the display device 190 shown in FIG. 1G, the display device 400 shown in FIG. 4A, or the display device 455 shown in FIG. 4D.
  • FIG. 7A shows that the right-eye and left-eye display systems 71 OR and 710L may include a micro-display device 735 coupled to the frame 705.
  • the micro-display device 735 may be any disclosed display device, such as the display device 100 shown in FIG. 1A, the display device 190 shown in FIG. 1G, the display device 400 shown in FIG. 4A, or the display device 455 shown in FIG. 4D.
  • the micro-display device 735 may be configured with a high display resolution and a high power efficiency.
  • the micro display device 735 may generate an image light representing a virtual image.
  • the NED 700 may also include a lens system (or viewing optical system) 785 and an object tracking system 750 (e.g., eye tracking system and/or face tracking system).
  • the lens system 785 may be disposed between the object tracking system 750 and the left-eye display system 710L.
  • the lens system 785 may be configured to guide the image light output from the left-eye display system 710L to an exit pupil 760.
  • the exit pupil 760 may be a location where an eye pupil 755 of an eye 765 of the user is positioned in an eye-box region 730 of the left-eye display system 710L.
  • the lens system (or viewing optical system) 785 may be polarization selective or non-polarization selective.
  • the lens system 785 may be configured to correct aberrations in the image light output from the left-eye display system 710L, magnify the image light output from the left- eye display system 710L, or perform another type of optical adjustment to the image light output from the left-eye display system 710L.
  • the lens system 785 may include multiple optical elements, such as lenses, waveplates, reflectors, etc.
  • the lens system 785 may include a pancake lens configured to fold the optical path, thereby reducing the back focal distance in the NED 700.
  • the pancake lens assembly may be any embodiment of the pancake lens assemblies disclosed herein, such as the pancake lens assembly 801 shown in FIG. 8A.
  • the object tracking system 750 may include an IR light source 751 configured to illuminate the eye 765 and/or the face, a deflecting element 752 configured to deflect the IR light reflected by the eye 765, and an optical sensor 753 configured to receive the IR light deflected by the deflecting element 752 and generate a tracking signal.
  • a software module is implemented with a computer program product including a computer-readable medium containing computer program code, which can be executed by a computer processor for performing any or all of the steps, operations, or processes described.
  • a hardware module may include hardware components such as a device, a system, an optical element, a controller, an electrical circuit, a logic gate, etc.
  • any optical device disclosed herein including one or more optical layers, films, plates, or elements including one or more optical layers, films, plates, or elements, the numbers of the layers, films, plates, or elements shown in the figures are for illustrative purposes only. In other embodiments not shown in the figures, which are still within the scope of the present disclosure, the same or different layers, films, plates, or elements shown in the same or different figures/embodiments may be combined or repeated in various manners to form a stack.

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Abstract

Un dispositif comprend une source de lumière conçue pour émettre une lumière. Le dispositif comprend également un panneau d'affichage comprenant une pluralité de zones de sous-pixels. Le dispositif comprend également un ensemble de microlentilles disposé entre la source de lumière et le panneau d'affichage. L'ensemble de microlentilles comprend un premier réseau de microlentilles conçu pour collimater sensiblement la lumière en une première lumière polarisée, et un second réseau de microlentilles conçu pour focaliser la première lumière polarisée en tant que seconde lumière polarisée se propageant à travers les ouvertures des zones de sous-pixels.
PCT/US2022/017273 2021-02-22 2022-02-22 Dispositif d'affichage comprenant un réseau de microlentilles à polarisation sélective WO2022178406A1 (fr)

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US202163152334P 2021-02-22 2021-02-22
US63/152,334 2021-02-22
US202163192556P 2021-05-24 2021-05-24
US63/192,556 2021-05-24
US17/541,232 US20220269092A1 (en) 2021-02-22 2021-12-02 Display device including polarization selective microlens array
US17/541,232 2021-12-02

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5315418A (en) * 1992-06-17 1994-05-24 Xerox Corporation Two path liquid crystal light valve color display with light coupling lens array disposed along the red-green light path
US20190250459A1 (en) * 2018-02-09 2019-08-15 Coretronic Corporation Display device
CN111465887A (zh) * 2017-10-11 2020-07-28 奇跃公司 包括具有透明发射显示器的目镜的增强现实显示器

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5315418A (en) * 1992-06-17 1994-05-24 Xerox Corporation Two path liquid crystal light valve color display with light coupling lens array disposed along the red-green light path
CN111465887A (zh) * 2017-10-11 2020-07-28 奇跃公司 包括具有透明发射显示器的目镜的增强现实显示器
US20190250459A1 (en) * 2018-02-09 2019-08-15 Coretronic Corporation Display device

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