GB2570688A - Light source for illuminating a display, image generator, display, and method for illuminating a display - Google Patents

Light source for illuminating a display, image generator, display, and method for illuminating a display Download PDF

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Publication number
GB2570688A
GB2570688A GB1801740.0A GB201801740A GB2570688A GB 2570688 A GB2570688 A GB 2570688A GB 201801740 A GB201801740 A GB 201801740A GB 2570688 A GB2570688 A GB 2570688A
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United Kingdom
Prior art keywords
light
display
quantum dot
head
wavelengths
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB1801740.0A
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GB201801740D0 (en
Inventor
Paul Freeman Jonathan
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BAE Systems PLC
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BAE Systems PLC
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.)
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Publication date
Application filed by BAE Systems PLC filed Critical BAE Systems PLC
Priority to GB1801740.0A priority Critical patent/GB2570688A/en
Publication of GB201801740D0 publication Critical patent/GB201801740D0/en
Publication of GB2570688A publication Critical patent/GB2570688A/en
Withdrawn legal-status Critical Current

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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
    • 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
    • G02B27/0101—Head-up displays characterised by optical features
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • 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
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B2027/0112—Head-up displays characterised by optical features comprising device for genereting colour display
    • 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
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B2027/0118—Head-up displays characterised by optical features comprising devices for improving the contrast of the display / brillance control visibility

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Instrument Panels (AREA)

Abstract

A light source 25 for an image generator 10 in a display system 5 such as a head-up, head-down, head-mounted or helmet mounted display, comprising a quantum dot layer 30 to convert light generated by the light source into light of a longer, predetermined wavelength for illuminating the display. The quantum dot layer may be selected to emit light having different ranges of wavelengths within a predetermined range of wavelengths that is greater than the range of wavelengths of light emitted by a single quantum dot, such that the quantum dot layer emits light having a substantially even distribution of wavelengths within the predetermined range of wavelengths. The light source may comprise one or more LEDs each having the quantum dot layer formed upon their surfaces. The LEDs may emit blue light and the quantum dot emits green light; or the LEDs comprise a colour display and the quantum dot layers are arranged to emit red, green and blue light. The wavelength of light emitted by the quantum dot layer may be different to a wavelength of light output by another display system intended for use with the display system.

Description

LIGHT SOURCE FOR ILLUMINATING A DISPLAY, IMAGE GENERATOR, DISPLAY, AND METHOD FOR ILLUMINATING A DISPLAY
Technical Field
This invention relates to a light source for illuminating a display, to an image generator, to a display, and to a method for illuminating a display.
Background
Digital image generators, for example in the form of digital image projectors or so-called ‘Digital Light Engines’ (DLEs), find use in various types of display system. For example, in a military aircraft, digital image generators are used in Head-Up Displays (HUDs), Head-Down Displays (HDDs) and Helmet-Mounted Displays (HMDs). In one example, a digital image generator may comprise a light source, for example one or more Light-Emitting Diodes (LEDs) for illuminating a display device such as a Digital Micro-mirror Display (DMD) device, and an optical system to convey light from the display device to enable viewing by a user of an image generated by the display device.
Challenges arise in achieving a required display brightness in the different use circumstances of the display system and in ensuring compatibility between different display systems likely to be used together, e.g. between a HUD and an HMD.
Summary of the Invention
According to a first aspect disclosed herein, there is provided a light source for a head-up, head-down, head-mounted or helmet-mounted display, comprising a quantum dot layer to convert light generated by the light source into light of a longer, predetermined wavelength for illuminating the display.
In this way, when light of a wavelength different to that emitted by easily available lights sources is required, an available light source may be combined
-2with an appropriate quantum dot layer to generate light of the required wavelength or range of wavelengths in an energy-efficient manner.
In an example, the quantum dot layer comprises quantum dots selected to emit light having different ranges of wavelengths within a predetermined range of wavelengths greater than the range of wavelengths of light emitted by a single quantum dot such that the quantum dot layer emits light having a substantially even distribution of wavelengths within the predetermined range of wavelengths.
Quantum dots emit light within a narrow range of wavelengths, e.g. 30nm. However, by selecting quantum dots having adjacent or overlapping ranges of wavelengths within a wider required range of wavelengths, light having a substantially even distribution of wavelengths across the required range may be generated.
In an example, the light source comprises one or more LEDs each having the quantum dot layer formed upon an output surface of the LED.
In an example, the one or more LEDs emit blue light and the quantum dot layer is arranged to emit green light.
In an example, the display comprises a colour display and the one or more LEDs comprise LEDs having quantum dot layers arranged to emit red, green and blue light respectively.
According to a second aspect disclosed herein, there is provided an image generator for a display system, the image generator comprising:
a light source;
a display device for generating an image when illuminated by light from the light source; and an optical system for conveying light from the display device for viewing, the light source having a quantum dot layer to convert light generated by the light source into light of a longer, predetermined wavelength for illuminating the display device.
-3The image generator may be provided as a self-contained unit, for example, that may be used with a variety of different display types.
In an example of the image generator, the display system comprises a head-up display (HUD).
In an example of the image generator, the display system comprises a head-down display (HDD).
In an example of the image generator, the display system comprises a head-mounted or helmet-mounted display (HMD).
In an example, the wavelength of light emitted by the quantum dot layer is selected to be different to a wavelength of light output by another display system intended for use with the display system.
Such differences in wavelength may be difficult to achieve in conventional display systems without the inefficiencies associated with converting the wavelength of light emitted by available LEDs, for example. However, the use of a quantum dot layer enables such wavelength constraints to be achieved very efficiently.
In an example, the quantum dot layer comprises quantum dots selected to emit light having different ranges of wavelengths within a predetermined range of wavelengths greater than the range of wavelengths of light emitted by a single quantum dot such that the quantum dot layer emits light having a substantially even distribution of wavelengths within the predetermined range of wavelengths.
In an example, the light source comprises one or more LEDs each having the quantum dot layer formed upon an output surface of the LED.
In an example, the one or more LEDs emit blue light and the quantum dot layer is arranged to emit green light.
In an example, the display system comprises a colour display and the one or more LEDs comprise LEDs having quantum dot layers arranged to emit red, green and blue light respectively.
-4According to a third aspect disclosed herein, there is provided a head-up, head-down, head-mounted or helmet-mounted display comprising a light source according to the first aspect described above and disclosed herein, to illuminate the display.
According to a fourth aspect disclosed herein, there is provided a headup, head-down, head-mounted or helmet-mounted display comprising an image generator according to the second aspect described above and disclosed herein.
According to a fifth aspect disclosed herein, there is provided a method for generating light to illuminate a head-up, head-down, head-mounted or helmet-mounted display, comprising applying a quantum dot layer to a light source of the display thereby to emit light of a predetermined wavelength or range or wavelengths for illuminating the display.
Brief Description of the Drawing
Example embodiments of the invention will now be described in more detail with reference to the accompanying drawing, Figure 1, providing a schematic view of components of a head-up display (HUD) according an example disclosed herein.
Detailed Description
Display systems intended for use in a military aircraft often need to operate with light of a wavelength that is slightly different to the wavelengths of light naturally emitted by any of the available LEDs. This may be necessary to achieve compatibility between different display systems likely to be used together, for example a HUD and an HMD. In that example, light emitted by the HUD needs to be visible with sufficient brightness through the visor of a helmet which is itself acting as a combiner for the HMD.
Conventionally, phosphor-coated LEDs are used in display systems to generate light of a required range of wavelengths, often in combination with one
-5or more filters to block light of wavelengths outside the required range. The combination of a phosphor coating and one or more filters may lead to a loss of up to 80% of the light emitted by the LED itself which is highly inefficient, requiring the LED to be driven with high power levels and so generate a lot of heat simply to ensure that the display brightness is sufficient.
According to embodiments of the present invention, a digital image generator of a display system employs a light source having a quantum dot layer selected to emit light of a required wavelength when stimulated by a blue LED, for example. Wavelength conversion by quantum dots is highly efficient and the quantum dot layer may be tailored to emit light of any required display wavelength from light received from an appropriately selected light source, such as a blue LED, without necessarily needing to include filters to filter the light. For example, in a colour display, red, green and blue light sources may be provided using appropriate quantum dot layers. For a monochrome display, a green light source may be provided. A HUD comprising a monochrome digital image generator according to the present invention will be now be described with reference to Figure 1.
Referring to Figure 1, a schematic diagram is provided showing simplified image generating and optical components of a HUD 5 in one example embodiment of the present invention. The HUD comprises three main components: a digital image generator or DLE 10; HUD projection optics 15; and a combiner 20. The digital image generator 10 comprises an LED 25 having a quantum dot layer 30 deposited onto a light-emitting face of the LED 25. Illumination optics 35 are provided to focus the light emitted by the quantum dot layer 30 onto an image generating device 40, such as a DMD. Activated pixel mirrors of the DMD are arranged to reflect the incident light towards and through an arrangement of lenses 45, 50, 55 to focus the light to form an image on a diffuser screen 60. If necessary a filter 65 may be inserted at an appropriate position within the train of lenses 45, 50, 55 to provide any filtering required to the light before the image is formed on the screen 60.
The HUD projection optics 15 comprise a collimating lens arrangement using lenses 70, 75 to collimate the image-bearing light passed by the diffuser
-6screen 60. The collimated light is reflected within a prism 80 towards the combiner 20 and from there the light is reflected towards a user 85.
In an HMD having a visor-projection display system, HMD projection optics perform a similar role to the projection optics 15 of the HUD to collimate and to direct the image-bearing light to project it onto the inside surface of the helmet visor, thereby to be reflected into the eyes of the wearer of the helmet.
In a waveguide display, the optical system of the digital image generator collimates the light from the display device 40 before injecting it into a waveguide.
Any compatibility issues constraining the choice of wavelength of light to be used in generating images in the HUD 5 may be satisfied by the choice of quantum dots in the quantum dot layer 30 applied to the LED 25. This solution enables a required HUD image brightness to be achieved without driving the light source LED 25 to the high brightness levels required of conventional display systems using phosphor-coated LEDs and optical filtering to achieve a required wavelength of display light.
In some applications, for example with waveguide displays, it may be desirable to be able to generate light for the display within a predetermined spectral band, with light of different wavelengths evenly distributed within that predetermined spectral band. The predetermined spectral band may typically be wider than the spectral band of light emitted by any one quantum dot. However, by selecting quantum dots having adjacent or overlapping spectral bands and in appropriate relative numbers, an even spread of wavelengths of light covering the predetermined spectral band may be achieved by the selected quantum dot layer 30.
There are various ways in which a quantum dot layer 30 may be applied to an LED 25 or other light source to generate light of a required wavelength or range of wavelengths. The options available will vary from one type of LED 25 to another according to the packaging of the light-emitting portion of the LED 25. For example, a pre-formed transparent cover having a quantum dot layer already deposited onto a surface of the cover may be supplied separately and
-7fixed to an LED 25. Alternatively, the LED 25 may be supplied with a quantum dot layer already applied to an appropriate surface by a manufacturer of the LED 25.
The examples described herein are to be understood as illustrative examples of embodiments of the invention. Further embodiments and examples are envisaged. Any feature described in relation to any one example or embodiment may be used alone or in combination with other features. In addition, any feature described in relation to any one example or embodiment may also be used in combination with one or more features of any other of the 10 examples or embodiments, or any combination of any other of the examples or embodiments. Furthermore, equivalents and modifications not described herein may also be employed within the scope of the invention, which is defined in the claims.

Claims (15)

1. A light source for a head-up, head-down, head-mounted or helmetmounted display, comprising a quantum dot layer to convert light generated by the light source into light of a longer, predetermined wavelength for illuminating the display.
2. The light source according to claim 1, wherein the quantum dot layer comprises quantum dots selected to emit light having different ranges of wavelengths within a predetermined range of wavelengths greater than the range of wavelengths of light emitted by a single quantum dot such that the quantum dot layer emits light having a substantially even distribution of wavelengths within the predetermined range of wavelengths.
3. The light source according to claim 1 or claim 2, wherein the light source comprises one or more LEDs each having the quantum dot layer formed upon an output surface of the LED.
4. The light source according to claim 3, wherein the one or more LEDs emit blue light and the quantum dot layer is arranged to emit green light.
5. The light source according to claim 3, wherein the display comprises a colour display and the one or more LEDs comprise LEDs having quantum dot layers arranged to emit red, green and blue light respectively.
6. An image generator for a display system, the image generator comprising:
a light source;
-9a display device for generating an image when illuminated by light from the light source; and an optical system for conveying light from the display device for viewing, the light source having a quantum dot layer to convert light generated by the light source into light of a longer, predetermined wavelength for illuminating the display device.
7. The image generator according to claim 6, wherein the display system comprises any one of: a head-up display (HUD), a head-down display (HDD); a head mounted; and a helmet-mounted display (HMD).
8. The image generator according to claim 6 or claim 7, wherein the wavelength of light emitted by the quantum dot layer is selected to be different to a wavelength of light output by another display system intended for use with the display system.
9. The image generator according to any one of claims 6 to 8, wherein the quantum dot layer comprises quantum dots selected to emit light having different ranges of wavelengths within a predetermined range of wavelengths greater than the range of wavelengths of light emitted by a single quantum dot such that the quantum dot layer emits light having a substantially even distribution of wavelengths within the predetermined range of wavelengths.
10. The image generator according to any one of claims 6 to 9, wherein the light source comprises one or more LEDs each having the quantum dot layer formed upon an output surface of the LED.
11. The image generator according to claim 10, wherein the one or more LEDs emit blue light and the quantum dot layer is arranged to emit green light.
- ΙΟΙ 2. The image generator according to claim 10, wherein the display system comprises a colour display and the one or more LEDs comprise LEDs having quantum dot layers arranged to emit red, green and blue light respectively.
13. A head-up, head-down, head-mounted or helmet-mounted display comprising a light source according to any one of claims 1 to 5 to illuminate the display.
10
14. A head-up, head-down, head-mounted or helmet-mounted display comprising an image generator according to any one of claims 6 to 12.
15. A method for generating light to illuminate a head-up, head-down, headmounted or helmet-mounted display, comprising applying a quantum dot layer 15 to a light source of the display thereby to emit light of a predetermined wavelength or range or wavelengths for illuminating the display.
GB1801740.0A 2018-02-02 2018-02-02 Light source for illuminating a display, image generator, display, and method for illuminating a display Withdrawn GB2570688A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1801740.0A GB2570688A (en) 2018-02-02 2018-02-02 Light source for illuminating a display, image generator, display, and method for illuminating a display

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1801740.0A GB2570688A (en) 2018-02-02 2018-02-02 Light source for illuminating a display, image generator, display, and method for illuminating a display

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GB201801740D0 GB201801740D0 (en) 2018-03-21
GB2570688A true GB2570688A (en) 2019-08-07

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GB1801740.0A Withdrawn GB2570688A (en) 2018-02-02 2018-02-02 Light source for illuminating a display, image generator, display, and method for illuminating a display

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150002528A1 (en) * 2013-06-28 2015-01-01 David D. Bohn Display efficiency optimization by color filtering
WO2017007770A2 (en) * 2015-07-07 2017-01-12 Sxaymiq Technologies Llc Quantum dot integration schemes
WO2017066556A1 (en) * 2015-10-15 2017-04-20 Osterhout Group, Inc. Compact optical system for head-worn computer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150002528A1 (en) * 2013-06-28 2015-01-01 David D. Bohn Display efficiency optimization by color filtering
WO2017007770A2 (en) * 2015-07-07 2017-01-12 Sxaymiq Technologies Llc Quantum dot integration schemes
WO2017066556A1 (en) * 2015-10-15 2017-04-20 Osterhout Group, Inc. Compact optical system for head-worn computer

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