GB2384059A - Pancake window optical device with thin film helicoidal bianisotropic medium - Google Patents
Pancake window optical device with thin film helicoidal bianisotropic medium Download PDFInfo
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- GB2384059A GB2384059A GB0200604A GB0200604A GB2384059A GB 2384059 A GB2384059 A GB 2384059A GB 0200604 A GB0200604 A GB 0200604A GB 0200604 A GB0200604 A GB 0200604A GB 2384059 A GB2384059 A GB 2384059A
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- optical device
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- 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
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3016—Polarising elements involving passive liquid crystal elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Polarising Elements (AREA)
- Liquid Crystal (AREA)
Abstract
An optical device (44), which functions as a pancake window so as to form a collimated image at or near infinity, consists of two beam splitters, one being a semi-reflective mirror (54), the other being an optical filter comprising a thin film helicoidal bianisotropic medium (56) on a substrate (62). The optical device is such that circularly polarised light (60) is made to follow a 180{ reflex path. This can be because the circularly polarised light (60) emanating from light source (46) is first reflected by optical filter (56) and then the polarity is reversed by being reflected by semi-reflective mirror (54) whereupon the light is transmitted through optical filter (56) to the eye (58). The device may be used in a head mounted display for virtual reality equipment to provide a collimated image without the need for heavier and more bulky lenses.
Description
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AN OPTICAL DEVICE
This invention relates to an optical device and, more especially, this invention relates to an optical device known as a pancake window.
The pancake window was invented by Larussa in 1966 and is described in US-A-3444858. The pancake window is an image forming apparatus that forms an image at or near infinity. In its original form, the pancake window had a low transmission of light and a limited contrast ratio.
Several enhancements to the original pancake window have been suggested, the most recent being by Kaiser in US-A-5715023 and US-A- 6075651 and by Sharp in US-A-6094242.
Both Kaiser and Sharp have shown that the use of cholesteric liquid crystal panels in the pancake window can be used to enhance the transmission of light. Kaiser has also identified the use of polarisation selective optical elements that reflect one linear polarisation state whilst transmitting radiation of the orthogonal state of polarisation. These polarisation selective optical elements can be designed to reflect electromagnetic radiation in a broad band of wave lengths. An example of a polarisation selective optical element is that known as dual brightness enhancement film manufactured by the 3m company. Kaiser utilised this dual brightness enhancement film in conjunction with a quarter wave plate in the enhancement of the pancake window to form a compact collimating apparatus. However, the dual brightness enhancement film appears to
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suffer a loss in performance with time, it is not available as a clear material, and it is also difficult to laminate as a flat mirror surface.
Other linear reflective polarisers have been developed, for example by Moxtech Corporation in the USA, that will also work in the imaging system suggested by Kaiser.
The present invention aims to enhance known pancake window without the above mentioned disadvantages. The present invention does this by using an optical filter comprising a thin film helicoidal bianisotropic medium and a substrate.
Accordingly, in one non-limiting embodiment of the present invention there is provided an optical device comprising two beam splitters, one being a semi-reflective mirror, the other being an optical filter comprising a thin film helicoidal bianisotropic medium on a substrate, and the optical device being such that in use circularly polarised light is made to follow a 1800 reflex path.
The use of the thin film helicoidal bianisotropic medium has several advantages over the known above mentioned enhancements to the basic pancake window. The thin film helicoidal bianisotropic medium on the substrate may be regarded as a circular polarisation filter. One of the advantages is that the structure of the thin film is controllable, with manufacture able to be tailored to specific requirements. Coatings such for example as an anti-reflective layer coating may be applied making the thin film helicoidal bianisotropic mediums much more robust. This overcomes some of the practical difficulties experienced with the above mentioned dual brightness enhancement film.
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The optical device of the present invention may be one in which the first beam splitter to receive the circularly polarised light is the semireflective mirror, and in which circularly polarised light of a particular hand incident on the semi-reflective mirror is partially transmitted and partially reflected, the transmitted light of this particular hand is then reflected by the optical filter back to the semi-transparent mirror, the light is partially transmitted and partially reflected, the hand of the circularly polarised light being reversed on reflection, and this reflected circularly polarised light is now transmitted by the optical filter.
An alternative optical device of the present invention may be one in which the first beam splitter to receive the circularly polarised light is the optical filter, and in which circularly polarised light of a particular hand incident on the optical filter is transmitted, the transmitted light of this particular hand is then partially reflected by the semi-transparent mirror back towards the optical filter, the hand of the circularly polarised light being reversed on reflection, this light is now reflected by the optical filter, and this reflected circularly polarised light is now partially transmitted by the semitransparent mirror.
The optical device may be one in which the semi-reflective mirror and the optical filter are flat beam splitters and are arranged to be parallel to each other.
Alternatively, the optical device may be one in which the optical filter is a flat beam splitter, and in which the semi-reflective mirror is a curved,
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concave/convex semi-transparent mirror which gives optical power to the optical device.
Alternatively, the optical device may be one in which the optical filter is a flat beam splitter, in which the semi-reflective mirror is a curved semitransparent mirror, and in which the optical device includes a piano convex lens, and a quarter wave retarder, the optical device being an optical collimating device which operates with incident light of a linear polarisation, the incident light is linear polarised, the quarter wave retarder turning this into the circularly polarised light. The circularly polarised light then follows the same path as described above. The effect of one of the refractive elements in this optical device is increased as the light passes through it three times as the light undergoes successive reflections at the optical surfaces.
Alternatively, the optical device may be one in which the semireflective mirror is a semi-transparent mirror, and in which the optical filter, a piano concave lens, the semi-transparent mirror, a piano concave and quarter wave retarder are joined as one solid optical device. The light follows the same transmissions and reflections as described above.
The optical device may be one in which the plane surface of the piano convex lens is used as the substrate for the thin film helicoidal bianisotropic medium.
The optical device may be one in which a coating is applied to the thin film helicoidal bianisotropic medium. The coating may be for making the
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optical device more robust or for other purposes. An example of the coating is an anti-reflective coating.
The optical device may be one in which a linear polariser is positioned adjacent to the quarter wave plate, and which the incident light in this case is not polarised but instead the effect of the linear polariser and quarter wave plate is to turn the incident light into circularly polarised light.
The circularly polarised light then follows the same path as described above.
The optical device may be one in which the collimating optical device described above is used as a compact eyepiece for use in a head mounted display. The head mounted display may be one in which the source of polarised light is a rear projection screen.
The optical device may be one in which the optical filter is embedded with liquid crystal and sandwiched between two transparent electrodes thereby providing an electro-optical switching device whose properties can be used to alter the characteristics of the optical device, thereby enabling the optical device to be switched from a collimating device to a noncollimating device. When the optical filter is addressed, the transmission difference between right and left circularly polarized light is negligible, both being transmitted at the same extent, and the filter is in effect turned off. In an alternative embodiment of the invention, the light path is reversed.
The optical device may include a linear polarising filter that is rotatable through 900 adjacent to the quarter wave plate, whereby the linear polarising filter turns the optical device from a collimating optical device to a non-collimating device, the light that is partially transmitted by the semi-
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transparent mirror is of one hand of circular polarisation, light reflected by the semi-transparent mirror has its direction of polarisation reversed, this is then reflected by the optical filter and then partially transmitted by the semi- reflective mirror, the light incident on the quarter wave plate is therefore of both hands of circular polarisation, the quarter wave plate turns this into light with two different linear directions of polarisation orthogonal to each other, whereby rotating the linear polarisation filter through 900 will allow either one of these polarisations to be transmitted only, thereby enabling the optical device to be switched from collimating to non-collimating.
Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:
Figure 1 shows a first known optical device utilising a cholesteric liquid crystal panel ;
Figure 2 shows a second known optical device utilising a cholesteric liquid crystal panel ;
Figure 3 shows a known optical device utilising dual brightness enhanced film;
Figure 4 shows the known manufacture of a circular polarisation filter made from a thin film helicoidal bianisotropic medium manufactured using a serial bi-deposition technique;
Figure 5 shows a first optical device of the present invention;
Figure 6 illustrates the use of a method known as chirping;
Figures 7,8, 9 and 10 show optical reflectivity plotted against wave length.
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Referring to Figures 1 and 2, it was mentioned above that both Kaiser and Sharp have shown that the use of cholesteric liquid crystal panels in an optical device known as a pancake window can be used to enhance the transmission of light, thereby overcoming a defect in the original pancake window invented by Larussa in 1966. Figure 1 shows an optical device 2 comprising a cholesteric liquid crystal panel 4, a piano convex lens 6, a piano concave 8, a light source 10, and a partially reflective coating 12.
Figure 2 shows an optical device 14 comprising a refractive element 16, a half mirror coating 18, and a cholesteric liquid crystal panel 20.
In Figures 1 and 2, the cholesteric liquid crystal panels 4,20 are used as devices that selectively reflect or transmit light depending upon the direction of the circular polarisation of the light. The improvements in the light transmission can be as much as four fold. However, the cholesteric liquid crystal panels 4,20 only work within specific desired wave lengths of electromagnetic radiation, and are therefore narrow band devices.
Referring now to Figure 3, it was also mentioned above that Kaiser had identified the use of polarisation selective optical elements that reflect one linear polarisation state while transmitting radiation of the orthogonal state of polarisation. These materials, such as the dual brightness ehancement film, can be designed to reflect electromagnetic radiation in a broad band of wave lengths. Kaiser utilised this form in conjunction with a quarter wave plate in the enhancement of the pancake window to form a compact collimating optical device. In Figure 3, there is shown an optical device 22 comprising dual brightness enhancement film 24, a quarter wave
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plate 26, a plano convex lens 28, a plano concave lens 30, a partially reflective coating 32, and a light source 34. The dual brightness enhancement film 24 appears to suffer a loss in performance with time, is not available as a clear material, and is also difficult to laminate in a flat mirror surface.
The present invention utilises an optical filter comprising a thin film helicoidal bianisotropic medium on a substrate. Such a circular polarisation filter has been developed by Hodgkinson et al (Optical Engineering, Vol. 39
No. 7, July 2000). The circular polarisation filter is made from a thin film helicoidal bianisotropic medium manufactured using a serial bi-deposition technique as shown in Figure 4. As can be seen from Figure 4, there is disclosed a substrate 36, a thin film helicoidal bianisotropic 38, vapour 40, and a quartz crystal 42. The serial bi-deposition technique shown in Figure 4 enables thin films to be manufactured with differing structures and hence differing properties and characteristics when used as optical filters. As shown in Figure 4, the thin film 38 is deposited on the substrate 36 from the vapour 40. The structure of the thin film 38 is determined by the angle of the source of the vapour 40 relative to the substrate 36, and any rotation of the substrate 36 during the deposition. If the substrate 36 is rotated during the deposition, a helical microstructure develops. The structure comprises twisted columns normal to the substrate, grown as either a right or left handed helix. Light of one circular polarisation will pass through the filter.
The helical structure of the filter in this case winds in the same direction as the polarised light and has a pitch of the same order of magnitude of the
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polarised light. It should be noted that confusion can arise because the conventions for defining the direction of rotation of a helical structure and circular polarised light are opposite. A right hand helical structure would rotate to the right in the direction of travel. The electric vector of the right circular polarised light rotates to the right when looking into the beam, that is in opposition to its direction of travel. For this reason, right circular polarised light is transmitted by a left hand helical structure, although in reality the helices are both rotated in the same direction. Light of the opposite hand will be reflected as the filter acts in this case as a Bragg grating.
Referring now to Figure 5, there is shown an optical device 44 comprising a light source 46 that emits lights of a specific linear polarisation.
This light passes through a quarter wave retarder 48. Also shown is a doublet lens comprising two piano convex lenses 50 and 52, with a semireflective mirror 54 in between. The circularly polarised light entering the optical device 44 is partially reflected and partially transmitted by the semireflective mirror 54. The circularly polarlised light is then reflected by an optical filter 56 which is a thin film helicoidal bianisotropic medium circular polarisation filter. The optical filter 56 is of the same polarisation as the polarised light. The light is then partially reflected and partially transmitted by the semi-reflective mirror 54, the polarisation of the reflected light being reversed. This light now incident on the circular polarisation optical filter 56 is transmitted through the optical filter 56 to the eye 58. In Figure 5, the light is shown as light 60. The optical filter comprises the thin film helicoidal bianisotropic medium 61 on a substrate 62.
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Studies by Dr. Martin McCall (Imperial College, London) have determined that it is possible to manufacturer a circular polarisation filter satisfying both the required range of incident angles and the range of wave lengths necessary for use as part of an optical system enhancing a pancake window. The method used to achieve this is to gradually increase the thickness of layers. This method is known as chirping and is illustrated in Figure 6. Figure 6 shows a substrate 64 and an arrow 66 showing increased in pitch. The use of the chirping in the manufacture of thin films increases the wavelength coverage. A range of 350nm covers the whole of the visible spectrum. A range in the order of 130nm is sufficient for the optical device of the present invention.
It is known that the wavelength range that is covered also shifts as the angle of incidence moves off axis. Therefore, the wavelength range covered must be sufficient to allow for these shifts in response to off axis incident light, see Figures 7,8 and 9.
It is also possible to manufacture the thin film to respond to specific wavelengths or bands of wavelengths. Individual thin films can also be made to respond to more than one wavelength, or more than one band of wavelengths. Therefore filters can be made which respond to ranges of the visible spectrum which combine to give the desired overall wave band, see Figure 10.
A protective top layer may be added to the thin film, providing a robust finish or an anti-reflective coating to the surface.
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It will be appreciated from the above that the use of thin film helicoidal bianisotropic mediums as a circular polarisation filter enable the enhancement of the known pancake window. For example, the structure of the thin film is controllable, with manufacture able to be tailored to specific requirements. Coatings may be applied as referred to above, in order to make the thin films more robust. This overcomes some of the practical difficulties experienced using the dual brightness enhancement film.
It is also to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected.
Claims (16)
- CLAIMS 1. An optical device comprising two beam splitters, one being a semireflective mirror, the other being an optical filter comprising a thin film helicoidal bianisotropic medium on a substrate, and the optical device being such that in use circularly polarised light is made to follow a 1800 reflex path.
- 2. An optical device according to claim 1 in which the first beam splitter to receive the circularly polarised light is the semi-reflective mirror, and in which circularly polarised light of a particular hand incident on the semireflective mirror is partially transmitted and partially reflected, the transmitted light of this particular hand is then reflected by the optical filter back to the semi-transparent mirror, the light is partially transmitted and partially reflected, the hand of the circularly polarised light being reversed on reflection, and this reflected circularly polarised light is now transmitted by the optical filter.
- 3. An optical device according to claim 1 in which the first beam splitter to received the circularly polarised light is the optical filter, and in which circularly polarised light of a particular hand incident on the optical filter is transmitted, the transmitted light of this particular hand is then partially reflected by the semi-transparent mirror back towards the optical filter, the hand of the circularly polarised light being reversed on reflection, this light is<Desc/Clms Page number 13>now reflected by the optical filter, and this reflected circularly polarised light is now partially transmitted by the semi-transparent mirror.
- 4. An optical device according to any one of the preceding claims in which the semi-reflective mirror and the optical filter are flat beam splitters and are arranged to be parallel to each other.
- 5. An optical device according to any one claims 1-3 in which the optical filter is a flat beam splitter, and in which the semi-reflective mirror is a curved, concave/convex semi-transparent mirror which gives optical power to the optical device.
- 6. An optical device according to any one of claims 1-3 in which the optical filter is a flat beam splitter, in which the semi-reflective mirror is a curved semi-transparent mirror, and in which the optical device includes a piano convex lens, and a quarter wave retarder, the optical device being an optical columating device which operates with incident light of a linear polarisation, the incident light is linear polarised, the quarter wave retarder turning this into the circularly polarised light.
- 7. An optical device according to any one of claims 1-3 in which in which the semi-reflective mirror is a semi-transparent mirror, and in which the optical filter, a piano concave lens, the semi-transparent mirror, a piano concave and quarter wave retarder are joined as one solid optical device.<Desc/Clms Page number 14>
- 8. An optical device according to claim 6 or claim 7 in which the plane surface of the piano convex lens is used as a substrate for the thin film helicoidal bianisotropic medium.
- 9. An optical device according to any one of the preceding claims in which a coating is applied to the thin film helicoidal bianisotropic medium.
- 10. An optical device according to claim 9 in which the coating is an antireflective coating.
- 11. An optical device according to claim 6 in which a linear polariser is positioned adjacent to the quarter wave plate, and which the incident light in this case is not polarised but instead the effect of the linear polariser and quarter wave plate is to turn the incident light into circularly polarised light.
- 12. An optical device according to claim 6 in which the collimating device is used as a compact eyepiece for use in a head mounted display.
- 13. An optical device according to claim 12 in which the head mounted display is one in which the source of polarised light is a rear projection screen.<Desc/Clms Page number 15>
- 14. An optical device according to claim 6 in which the optical filter is embedded with liquid crystal and sandwiched between two transparent electrodes thereby providing an electro-optical switching device whose properties can be used to alter the characteristics of the optical device, thereby enabling the optical device to be switched from a collimating device to a non-collimating device.
- 15. An optical device according to claim 6 and including a linear polarising filter that is rotatable through 900 adjacent to the quarter wave plate, whereby the linear polarising filter turns the optical device from a collimating optical device to a non-collimating device, the light that is partially transmitted by the semi-transparent mirror is of one hand of circular polarisation, light reflected by the semi-transparent mirror has its direction of polarisation reversed, this is then reflected by the optical filter and then partially transmitted by the semi-reflective mirror, the light incident on the quarter wave plate is therefore of both hands of circular polarisation, the quarter wave plate turns this into light with two different linear directions of polarisation orthogonal to each other, whereby rotating the linear polarisation filter through 900 will allow either one of these polarisations to be transmitted only, thereby enabling the optical device to be switched from collimating to non-collimating.
- 16. An optical device substantially as herein described with reference to Figures 4-10 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0200604A GB2384059A (en) | 2002-01-11 | 2002-01-11 | Pancake window optical device with thin film helicoidal bianisotropic medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0200604A GB2384059A (en) | 2002-01-11 | 2002-01-11 | Pancake window optical device with thin film helicoidal bianisotropic medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0200604D0 GB0200604D0 (en) | 2002-02-27 |
| GB2384059A true GB2384059A (en) | 2003-07-16 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0200604A Withdrawn GB2384059A (en) | 2002-01-11 | 2002-01-11 | Pancake window optical device with thin film helicoidal bianisotropic medium |
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| GB (1) | GB2384059A (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10120194B2 (en) | 2016-01-22 | 2018-11-06 | Corning Incorporated | Wide field personal display |
| WO2020032943A1 (en) | 2018-08-07 | 2020-02-13 | Facebook Technologies, Llc | Reflective circular polarizer for head-mounted display |
| WO2021055298A1 (en) * | 2019-09-17 | 2021-03-25 | Facebook Technologies, Llc | Lens assembly including a volume bragg grating and display device including the same |
| US10976551B2 (en) | 2017-08-30 | 2021-04-13 | Corning Incorporated | Wide field personal display device |
| US11360308B2 (en) | 2020-01-22 | 2022-06-14 | Facebook Technologies, Llc | Optical assembly with holographic optics for folded optical path |
| US11391948B2 (en) | 2019-09-10 | 2022-07-19 | Facebook Technologies, Llc | Display illumination using a grating |
| US11467332B2 (en) | 2019-09-10 | 2022-10-11 | Meta Platforms Technologies, Llc | Display with switchable retarder array |
| US11579425B1 (en) | 2019-08-05 | 2023-02-14 | Meta Platforms Technologies, Llc | Narrow-band peripheral see-through pancake lens assembly and display device with same |
| US11586024B1 (en) | 2019-08-05 | 2023-02-21 | Meta Platforms Technologies, Llc | Peripheral see-through pancake lens assembly and display device with same |
| US11726336B2 (en) | 2019-09-10 | 2023-08-15 | Meta Platforms Technologies, Llc | Active zonal display illumination using a chopped lightguide |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10727602B2 (en) * | 2018-04-18 | 2020-07-28 | The Boeing Company | Electromagnetic reception using metamaterial |
| US10495798B1 (en) * | 2018-08-07 | 2019-12-03 | Facebook Technologies, Llc | Switchable reflective circular polarizer in head-mounted display |
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|---|---|---|---|---|
| EP0302619A2 (en) * | 1987-08-03 | 1989-02-08 | Kaiser Aerospace And Electronics Corporation | Opticle collimating apparatus |
| EP0718645A2 (en) * | 1994-12-19 | 1996-06-26 | Sharp Kabushiki Kaisha | Optical device and head-mounted display using said optical device |
| WO1998003695A1 (en) * | 1996-07-23 | 1998-01-29 | The Governors Of The University Of Alberta | Capped porous thin films |
-
2002
- 2002-01-11 GB GB0200604A patent/GB2384059A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0302619A2 (en) * | 1987-08-03 | 1989-02-08 | Kaiser Aerospace And Electronics Corporation | Opticle collimating apparatus |
| EP0718645A2 (en) * | 1994-12-19 | 1996-06-26 | Sharp Kabushiki Kaisha | Optical device and head-mounted display using said optical device |
| WO1998003695A1 (en) * | 1996-07-23 | 1998-01-29 | The Governors Of The University Of Alberta | Capped porous thin films |
Non-Patent Citations (1)
| Title |
|---|
| Optical Engineering Vol. 39, No. 7, July 2000 Hodgkinson et al, "Circular polarisation filters.....", pages 1863 to 1868 * |
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| US10649210B2 (en) | 2016-01-22 | 2020-05-12 | Corning Incorporated | Wide field personal display |
| US10120194B2 (en) | 2016-01-22 | 2018-11-06 | Corning Incorporated | Wide field personal display |
| US10976551B2 (en) | 2017-08-30 | 2021-04-13 | Corning Incorporated | Wide field personal display device |
| WO2020032943A1 (en) | 2018-08-07 | 2020-02-13 | Facebook Technologies, Llc | Reflective circular polarizer for head-mounted display |
| CN112543885A (en) * | 2018-08-07 | 2021-03-23 | 脸谱科技有限责任公司 | Reflective circular polarizer for head-mounted display |
| EP3834030A4 (en) * | 2018-08-07 | 2021-12-29 | Facebook Technologies, LLC | Reflective circular polarizer for head-mounted display |
| US11586024B1 (en) | 2019-08-05 | 2023-02-21 | Meta Platforms Technologies, Llc | Peripheral see-through pancake lens assembly and display device with same |
| US11579425B1 (en) | 2019-08-05 | 2023-02-14 | Meta Platforms Technologies, Llc | Narrow-band peripheral see-through pancake lens assembly and display device with same |
| US11391948B2 (en) | 2019-09-10 | 2022-07-19 | Facebook Technologies, Llc | Display illumination using a grating |
| US11726336B2 (en) | 2019-09-10 | 2023-08-15 | Meta Platforms Technologies, Llc | Active zonal display illumination using a chopped lightguide |
| US11592608B2 (en) | 2019-09-10 | 2023-02-28 | Meta Platforms Technologies, Llc | Switchable polarization retarder array for active zonal illumination of display |
| US11467332B2 (en) | 2019-09-10 | 2022-10-11 | Meta Platforms Technologies, Llc | Display with switchable retarder array |
| US10989928B2 (en) | 2019-09-17 | 2021-04-27 | Facebook Technologies, Llc | Thin see-through pancake lens assembly and display device including the same |
| US11372247B2 (en) | 2019-09-17 | 2022-06-28 | Facebook Technologies, Llc | Display device with diffusive display and see-through lens assembly |
| US11422375B2 (en) | 2019-09-17 | 2022-08-23 | Meta Platforms Technologies, Llc | Curved see-through pancake lens assembly and display device including the same |
| US11448885B2 (en) | 2019-09-17 | 2022-09-20 | Meta Platforms Technologies, Llc | Lens assembly including a volume Bragg grating and display device including the same |
| CN114144704A (en) * | 2019-09-17 | 2022-03-04 | 脸谱科技有限责任公司 | Lens assembly including volume bragg grating and display device |
| US11073700B2 (en) | 2019-09-17 | 2021-07-27 | Facebook Technologies, Llc | Display device with switchable diffusive display and see-through lens assembly |
| US11016304B2 (en) | 2019-09-17 | 2021-05-25 | Facebook Technologies, Llc | Lens assembly including a volume bragg grating and display device including the same |
| WO2021055298A1 (en) * | 2019-09-17 | 2021-03-25 | Facebook Technologies, Llc | Lens assembly including a volume bragg grating and display device including the same |
| US11835722B2 (en) | 2019-09-17 | 2023-12-05 | Meta Platforms Technologies, Llc | Display device with transparent emissive display and see-through lens assembly |
| US11852814B2 (en) | 2019-09-17 | 2023-12-26 | Meta Platforms Technologies, Llc | Display device with holographic diffuser display and see-through lens assembly |
| US11960090B2 (en) | 2019-09-17 | 2024-04-16 | Meta Platforms Technologies, Llc | Curved see-through pancake lens assembly and display device including the same |
| US11422373B2 (en) | 2020-01-22 | 2022-08-23 | Facebook Technologies, Llc | Optical assembly with holographic optics for folded optical path |
| US11360308B2 (en) | 2020-01-22 | 2022-06-14 | Facebook Technologies, Llc | Optical assembly with holographic optics for folded optical path |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0200604D0 (en) | 2002-02-27 |
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