WO1993019393A1 - Head-up display system - Google Patents

Head-up display system Download PDF

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Publication number
WO1993019393A1
WO1993019393A1 PCT/GB1993/000564 GB9300564W WO9319393A1 WO 1993019393 A1 WO1993019393 A1 WO 1993019393A1 GB 9300564 W GB9300564 W GB 9300564W WO 9319393 A1 WO9319393 A1 WO 9319393A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter
head
display system
display
reflection
Prior art date
Application number
PCT/GB1993/000564
Other languages
French (fr)
Inventor
Michael George Clark
Noorallah Nourshargh
Original Assignee
Gec-Marconi Limited
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
Application filed by Gec-Marconi Limited filed Critical Gec-Marconi Limited
Publication of WO1993019393A1 publication Critical patent/WO1993019393A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/289—Rugate filters
    • 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
    • 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

Definitions

  • This invention relates mainly to head-up display systems, such systems comprising a combiner through which an observer can view a scene, and an optical unit arranged to project matter to be displayed on to the combiner for reflection to the observer, thereby to provide the observer with an image of the display superimposed on his view through the combiner.
  • Head-up display systems are commonly used in aircraft, the display in such a case being, for example, instrument readings, radar presentations, maps or other information, although they may have alternative applications.
  • the display is generally formed by a narrow waveband of light, for example in the green region of the visible spectrum.
  • the combiner in such a system is then in the form of a filter which is capable of reflecting this narrow waveband without significantly affecting the observer's view through the combiner. It would, however, be desirable, in some instances, to be able to provide a multicolour display. This is, however, not practicable with combiners formed by conventional multilayer stack filter fabrication techniques, and an object of the invention is to provide a form of head-up display system capable of providing such a multicolour display.
  • a head-up display system incorporates means for providing a multicolour display, and a combiner in the form of a rugate filter having a reflection characteristic with a plurality of narrow reflection bands, capable of reflecting different respective wavelengths generated by the display.
  • rugate filters which are optical interference filters which have continuously modulated refractive indices throughout their thickness
  • rugate filters can be formed in such a way that they provide a multiresponse narrow band reflection characteristic in a single filter thickness.
  • the invention therefore inlcudes within its scope rugate filters providing such multiresponse narrow band reflection characteristics.
  • Such filters can be formed of materials, for example silicon oxynitride, rendering them hard and relatively scratchproof.
  • the filters are readily formed using a microwave plasma assisted chemical vapour deposition technique, as will subsequently be described.
  • the reflection bands can readily be chosen to match the spectra of the phosphors employed in the tube.
  • the filter Preferably there are three reflection bands in the red, blue and green regions of the spectrum. However in some cases it might be adequate to form the filter with two reflection bands only, depending upon the display required.
  • the invention is applicable to both helmet-mounted and separately mounted head-up display systems.
  • FIGS 1 and 2 represent, in diagrammatic form only, two types of head-up display systems embodying the invention
  • FIG 3 illustrates the reflectance response of one rugate filter combiner suitable for use in the systems shown in Figures 1 and 2,
  • FIG. 4 illustrates the manner in which the combiner is formed
  • Figures 5 and 6 illustrate the reflectance response of alternative rugate filters.
  • this shows a form of aircraft cockpit head-up display unit in which the display on the screen of a cathode ray tube 1, for example in the form of a map, is reflected by a mirror 2 through a collimating lens 3 on to a combiner 4.
  • This is substantially transparent so that a viewer 5, for example the pilot of the aircraft, can see forwardly through it, but is arranged to reflect towards the eye of the viewer an image of the display, represented at 6.
  • FIG. 2 An alternative form of head-up display unit is shown in Figure 2. This similarly incorporates a cathode ray tube 1, mirror 2, collimating lens 3 and combiner 4, and operates in the same manner as the unit illustrated in Figure 1, but in this case the unit is mounted within the helmet 7 of, say, the pilot.
  • the combiner 4 in each case is a rugate filter having a reflection characteristic with three narrow peaks 11, 12 and 13 in the red, blue and green regions of the visible spectrum as shown in Figure 3.
  • a method of depositing a layer on a substrate by such a process is described in GB-A-2194966.
  • the substrate is supported within a heated evacuated chamber, and a gaseous reaction mixture, comprising two or more gases and/or vapours, capable of reacting together to form a solid deposit, is directed towards the surface of the substrate through a multiplicity of perforations whilst a microwave plasma is produced in the chamber such as to cause a chemical reaction to take place and form the 1ayer.
  • the reaction mixture consists of silicon tetrachloride, oxygen and nitrogen in an inert carrier gas such as argon.
  • the components of the reaction mixture react chemically to produce a layer of silicon oxynitride on the surface of the substrate which may, for example, consist of silica.
  • a variation in the refractive index is achieved by varying the relative flow rates of the components of the reaction mixture which are introduced into the reaction space using precision mass flow controllers operated by computer.
  • a silicon oxynitride system retains a glassy phase throughout its composition from silica (refractice index 1.46) to silicon nitride (refractive index 2.04) so that by smoothly varying the flow rates of the components of the reaction mixture in a sinusoidal manner a layer whose refractive index varies sinusoidally as a smooth and continuous function of optical thickness can be obtained.
  • the manner in which the refractive index is varied by varying the flow rates of the reaction mixture components is readily ascertainable by trial.
  • the variation in frequency of the refractive index will determine the wavelengths of the reflection peaks.
  • the three peaks are obtained by intermodulating three sinusoidal variations as indicated in Figure 4.
  • the reflection peaks do not significantly reduce the pilot's view through the combiner, but provide a means of forming a multi-coloured image of a coloured display on the cathode ray tube screen.
  • the invention is applicable to other forms of head-up display systems, besides those described, in which a multi-coloured display is required.
  • the invention also includes within its scope multiresponse narrow band reflection filters in the form of rugate filters suitable for use in such displays.
  • Other materials besides silica may also be used to form the substrate on which the varying refractive index layer is formed, for example glass, sapphire, polycarbonate.
  • rugate filters comprising, on a supportive substrate, a deposited layer having refractive indices which vary in a manner giving multiresponse reflection characteristics in a single filter thickness
  • a deposited layer having refractive indices which vary in a manner giving multiresponse reflection characteristics in a single filter thickness
  • one reflection band at least may lie outside the visible region of the spectrum.
  • the reflection response of one such filter is illustrated in Figure 6, the filter, which is also formed by a microwave plasma assisted chemical deposition process in a similar manner to those previously described, has narrow peaks 16, 17 lying in the infra-red and red regions of the spectrum.
  • the substrate employed should be appropriate to the use for which the particular filter is designed.

Abstract

A head-up display system has means for providing a multicolour display, and a combiner in the form of a rugate filter having a reflection characteristic with a plurality of narrow reflection bands capable of reflecting different respective wavelengths generated by the display. The invention also includes within its scope ruguate filters comprising, on a supportive substrate, a deposited layer having a refractive index which varies as a function of optical thickness so as to provide multiresponse reflection characteristic.

Description

HEAD-UP DISPLAY SYSTEM
This invention relates mainly to head-up display systems, such systems comprising a combiner through which an observer can view a scene, and an optical unit arranged to project matter to be displayed on to the combiner for reflection to the observer, thereby to provide the observer with an image of the display superimposed on his view through the combiner.
Head-up display systems are commonly used in aircraft, the display in such a case being, for example, instrument readings, radar presentations, maps or other information, although they may have alternative applications.
In head-up display systems at present in use the display is generally formed by a narrow waveband of light, for example in the green region of the visible spectrum. The combiner in such a system is then in the form of a filter which is capable of reflecting this narrow waveband without significantly affecting the observer's view through the combiner. It would, however, be desirable, in some instances, to be able to provide a multicolour display. This is, however, not practicable with combiners formed by conventional multilayer stack filter fabrication techniques, and an object of the invention is to provide a form of head-up display system capable of providing such a multicolour display.
According, therefore, to one aspect of the invention a head-up display system incorporates means for providing a multicolour display, and a combiner in the form of a rugate filter having a reflection characteristic with a plurality of narrow reflection bands, capable of reflecting different respective wavelengths generated by the display.
Thus, we have established that rugate filters, which are optical interference filters which have continuously modulated refractive indices throughout their thickness, can be formed in such a way that they provide a multiresponse narrow band reflection characteristic in a single filter thickness. The invention therefore inlcudes within its scope rugate filters providing such multiresponse narrow band reflection characteristics. Such filters can be formed of materials, for example silicon oxynitride, rendering them hard and relatively scratchproof. The filters are readily formed using a microwave plasma assisted chemical vapour deposition technique, as will subsequently be described.
Where the display is provided by a cathode ray tube the reflection bands can readily be chosen to match the spectra of the phosphors employed in the tube.
Preferably there are three reflection bands in the red, blue and green regions of the spectrum. However in some cases it might be adequate to form the filter with two reflection bands only, depending upon the display required.
The invention is applicable to both helmet-mounted and separately mounted head-up display systems.
A number of different embodiments of the invention will now be described by way of example with reference to Figures 1 to 6 of the accompanying schematic drawings, in which
Figures 1 and 2 represent, in diagrammatic form only, two types of head-up display systems embodying the invention,
Figure 3 illustrates the reflectance response of one rugate filter combiner suitable for use in the systems shown in Figures 1 and 2,
Figure 4 illustrates the manner in which the combiner is formed, and
Figures 5 and 6 illustrate the reflectance response of alternative rugate filters. Referring first to Figure 1, this shows a form of aircraft cockpit head-up display unit in which the display on the screen of a cathode ray tube 1, for example in the form of a map, is reflected by a mirror 2 through a collimating lens 3 on to a combiner 4. This is substantially transparent so that a viewer 5, for example the pilot of the aircraft, can see forwardly through it, but is arranged to reflect towards the eye of the viewer an image of the display, represented at 6.
An alternative form of head-up display unit is shown in Figure 2. This similarly incorporates a cathode ray tube 1, mirror 2, collimating lens 3 and combiner 4, and operates in the same manner as the unit illustrated in Figure 1, but in this case the unit is mounted within the helmet 7 of, say, the pilot.
The combiner 4 in each case is a rugate filter having a reflection characteristic with three narrow peaks 11, 12 and 13 in the red, blue and green regions of the visible spectrum as shown in Figure 3.
This is formed by a microwave plasma assisted chemical vapour deposition process.
One method of depositing a layer on a substrate by such a process is described in GB-A-2194966. In the method described the substrate is supported within a heated evacuated chamber, and a gaseous reaction mixture, comprising two or more gases and/or vapours, capable of reacting together to form a solid deposit, is directed towards the surface of the substrate through a multiplicity of perforations whilst a microwave plasma is produced in the chamber such as to cause a chemical reaction to take place and form the 1ayer.
In applying the technique to the manufacture of a rugate filter in accordance with the invention the reaction mixture consists of silicon tetrachloride, oxygen and nitrogen in an inert carrier gas such as argon. The components of the reaction mixture react chemically to produce a layer of silicon oxynitride on the surface of the substrate which may, for example, consist of silica. A variation in the refractive index is achieved by varying the relative flow rates of the components of the reaction mixture which are introduced into the reaction space using precision mass flow controllers operated by computer. Now a silicon oxynitride system retains a glassy phase throughout its composition from silica (refractice index 1.46) to silicon nitride (refractive index 2.04) so that by smoothly varying the flow rates of the components of the reaction mixture in a sinusoidal manner a layer whose refractive index varies sinusoidally as a smooth and continuous function of optical thickness can be obtained. The manner in which the refractive index is varied by varying the flow rates of the reaction mixture components is readily ascertainable by trial.
The variation in frequency of the refractive index will determine the wavelengths of the reflection peaks. Thus, in the filter described, the three peaks are obtained by intermodulating three sinusoidal variations as indicated in Figure 4. The reflection peaks do not significantly reduce the pilot's view through the combiner, but provide a means of forming a multi-coloured image of a coloured display on the cathode ray tube screen.
An alternative rugate filter having two narrow peaks 14, 15 in the red and blue/green regions of the visible spectrum is shown in Figure 5, the filter being formed in by a microwave plasma assisted chemical vapour deposition process in a similar manner to the filter previously described.
It will be appreciated that the invention is applicable to other forms of head-up display systems, besides those described, in which a multi-coloured display is required. The invention also includes within its scope multiresponse narrow band reflection filters in the form of rugate filters suitable for use in such displays. Other materials besides silica may also be used to form the substrate on which the varying refractive index layer is formed, for example glass, sapphire, polycarbonate.
Moreover rugate filters comprising, on a supportive substrate, a deposited layer having refractive indices which vary in a manner giving multiresponse reflection characteristics in a single filter thickness can have uses in a variety of other applications apart from head-up display systems and, for some purposes, one reflection band at least may lie outside the visible region of the spectrum. The reflection response of one such filter is illustrated in Figure 6, the filter, which is also formed by a microwave plasma assisted chemical deposition process in a similar manner to those previously described, has narrow peaks 16, 17 lying in the infra-red and red regions of the spectrum. Other variations are clearly also possible. It will be appreciated that the substrate employed should be appropriate to the use for which the particular filter is designed.

Claims

1. A head-up display system incorporating means for providing a multicolour display, and a combiner in the form of a rugate filter having a reflection characteristic with a plurality of narrow reflection bands, capable of reflecting different respective wavelengths generated by the display.
2. A head-up display system according to Claim 1 wherein the filter is formed of silicon oxynitride.
3. A head-up display system according to Claim 1 or 2 wherein the filter has two or three narrow reflection bands.
4. A head-up display system according to any preceding claim wherein the filter has reflection bands in the red, blue and green regions of the spectrum.
5. A head-up display system according to any preceding claim wherein the filter has reflection bands in the red and blue/green regions of the spectrum.
6. A head-up display system according to any preceding claim in which the display is provided by a cathode ray tube, the reflection bands of the filter matching the spectra of the phosphors employed in the tube.
7. A head-up display system substantially as shown in and as hereinbefore described with reference to Figures 1, 3 and 4 or Figures 2, 3 and 4 of the accompanying drawings.
8. A multi-response narrow band reflection filter for use in a display system according to any preceding claim, which filter consists of a rugate filter.
9. The manufacture of a multi-response narrow band reflection filter according to Claim 8 in which the filter is formed by depositing on a light-transmitting substrate, by a microwave assisted chemical vapour deposition process, a layer having a refractive index which varies sinusoidally as a smooth and continuous function of optical thickness.
10. The manufacture of a filter according to Claim 9 wherein the layer consists of silicon oxynitride.
11. The manufacture according to Claim 10 wherein the layer is formed by introducing into an evacuated heated chamber, containing the substrate, a gaseous reaction mixture comprising silicon tetrachloride vapour, oxygen and nitrogen in an inert carrier gas, and directing the mixture towards a surface of the substrate through a multiplicty of perforations, coupling microwave power into the chamber to produce a plasma in the chamber, and varying the relative flow rates of the components of the reaction mixture in a smooth sinusoidal manner to produce a layer of silicon oxynitride on the surface having a sinusoidally varying refractive index.
12. The manufacture of a filter for a head-up display system carried out substantially as described with reference to Figures 3 and 4 or Figure 5 of the accompanying drawings.
13. A rugate filter comprising, on a supportive substrate, a deposited layer having a refractive index which varies as a function of optical thickness, so as to provide a multiresponse reflection characteristic.
14. A rugate filter according to Claim 13 wherein the deposited layer consists of silicon oxynitride.
15. A rugate filter according to Claim 13 or 14 wherein the refractive index of the deposited layer varies sinusoidally as a smooth and continuous function of its optical thickness.
16. A rugate filter substantially as shown in and as hereinbefore described with reference to Figure 6 of the accompanying drawings.
17. The manufacture of a rugate filter according to
Claim 13, 14, 15 or 16 wherein the layer is formed by a microwave plasma assisted chemical vapour deposition process.
PCT/GB1993/000564 1992-03-25 1993-03-19 Head-up display system WO1993019393A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9206463.3 1992-03-25
GB929206463A GB9206463D0 (en) 1992-03-25 1992-03-25 Head-up display system

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WO1993019393A1 true WO1993019393A1 (en) 1993-09-30

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6956702B2 (en) 2003-04-23 2005-10-18 Hewlett-Packard Development Company, L.P. Projector with spectral filter
WO2016135288A1 (en) * 2015-02-27 2016-09-01 Jaguar Land Rover Limited Head up display apparatus and display surface therefor
CN106143152A (en) * 2015-03-26 2016-11-23 中航联创科技有限公司 Vehicle-mounted flat aobvious device
CN106143151A (en) * 2015-03-26 2016-11-23 中航联创科技有限公司 Vehicle-mounted flat aobvious device
US10365482B1 (en) * 2014-05-15 2019-07-30 Rockwell Collins, Inc. Light control system
EP4270092A4 (en) * 2020-12-28 2024-02-14 Fujifilm Corp Light guide and image display device

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FR2840692B1 (en) * 2002-06-10 2004-10-15 Sagem DIRECT VISION DEVICE WITH PROTECTION AGAINST OPTICAL ASSAULT AND EYE RESTORATION
DE102007047232A1 (en) * 2007-10-02 2009-04-16 Linos Photonics Gmbh & Co. Kg Head-up display for motor vehicle
US8023195B2 (en) 2008-10-23 2011-09-20 Gentex Corporation Split laser eye protection system
CN103487942B (en) * 2013-09-29 2016-08-10 惠州市华阳多媒体电子有限公司 A kind of HUD brightness improving device

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WO1987001211A2 (en) * 1985-08-14 1987-02-26 Hughes Aircraft Company Graded index aspheric combiners and display system utilizing same
GB2194966A (en) * 1986-08-20 1988-03-23 Gen Electric Plc Deposition of films
US4837044A (en) * 1987-01-23 1989-06-06 Itt Research Institute Rugate optical filter systems
US4984872A (en) * 1989-06-16 1991-01-15 Rockwell International Corporation Wide viewing angle avionics liquid crystal display
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JOURNAL OF THE CERAMIC SOCIETY OF JAPAN vol. 99, no. 10, October 1991, pages 894 - 902 KERSTEN 'THICK COATINGS OF DOPED SYNTHETIC SILICA GLASS BY PLASMA IMPULSED CVD' pages 898 - 899, paragraph 3.2 : 'Rugate filters made with PICVD inside quartz glass tubes' *
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6956702B2 (en) 2003-04-23 2005-10-18 Hewlett-Packard Development Company, L.P. Projector with spectral filter
US10365482B1 (en) * 2014-05-15 2019-07-30 Rockwell Collins, Inc. Light control system
WO2016135288A1 (en) * 2015-02-27 2016-09-01 Jaguar Land Rover Limited Head up display apparatus and display surface therefor
CN106143152A (en) * 2015-03-26 2016-11-23 中航联创科技有限公司 Vehicle-mounted flat aobvious device
CN106143151A (en) * 2015-03-26 2016-11-23 中航联创科技有限公司 Vehicle-mounted flat aobvious device
EP4270092A4 (en) * 2020-12-28 2024-02-14 Fujifilm Corp Light guide and image display device

Also Published As

Publication number Publication date
GB9305662D0 (en) 1993-05-19
GB2265726A (en) 1993-10-06
GB9206463D0 (en) 1992-07-22

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