GB2222892A - Optical display apparatus - Google Patents

Optical display apparatus Download PDF

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Publication number
GB2222892A
GB2222892A GB8918119A GB8918119A GB2222892A GB 2222892 A GB2222892 A GB 2222892A GB 8918119 A GB8918119 A GB 8918119A GB 8918119 A GB8918119 A GB 8918119A GB 2222892 A GB2222892 A GB 2222892A
Authority
GB
United Kingdom
Prior art keywords
display apparatus
optical display
optical
image source
light beam
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Withdrawn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
GB8918119A
Other versions
GB8918119D0 (en
Inventor
Michael Harold Freeman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Qioptiq Ltd
Original Assignee
Pilkington PE Ltd
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 Pilkington PE Ltd filed Critical Pilkington PE Ltd
Publication of GB8918119D0 publication Critical patent/GB8918119D0/en
Publication of GB2222892A publication Critical patent/GB2222892A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/10Beam splitting or combining systems
    • G02B27/1006Beam splitting or combining systems for splitting or combining different wavelengths
    • G02B27/102Beam splitting or combining systems for splitting or combining different wavelengths for generating a colour image from monochromatic image signal sources
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01Head-up displays
    • G02B27/0101Head-up displays characterised by optical features
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01Head-up displays
    • G02B27/0101Head-up displays characterised by optical features
    • G02B27/0103Head-up displays characterised by optical features comprising holographic elements
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/10Beam splitting or combining systems
    • G02B27/1006Beam splitting or combining systems for splitting or combining different wavelengths
    • G02B27/102Beam splitting or combining systems for splitting or combining different wavelengths for generating a colour image from monochromatic image signal sources
    • G02B27/1046Beam splitting or combining systems for splitting or combining different wavelengths for generating a colour image from monochromatic image signal sources for use with transmissive spatial light modulators
    • G02B27/1053Beam splitting or combining systems for splitting or combining different wavelengths for generating a colour image from monochromatic image signal sources for use with transmissive spatial light modulators having a single light modulator for all colour channels
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/10Beam splitting or combining systems
    • G02B27/1086Beam splitting or combining systems operating by diffraction only
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/10Beam splitting or combining systems
    • G02B27/14Beam splitting or combining systems operating by reflection only
    • G02B27/141Beam splitting or combining systems operating by reflection only using dichroic mirrors

Abstract

Optical display apparatus particularly for head-up or head-down use in fighter aircraft, comprises two separate channels, a high resolution green channel H and a low resolution blue-red channel L. Each channel has an image source in the form of a cathode ray tube 1, 2 or a liquid crystal display (LCD) Figs, 2, 4 (not shown). A beam combining means 5 combines the two images from the image sources and may be a cube comprising a pair of contacting 45 DEG prisms 6, 7 or a flat plate (5), Figs 3, 4 (not shown). The cube or the plate may include either a dichroic film HD or a holographic optical element HD. The combined images are seen by the viewer E through a partial reflector 11 which may include a holographic optical element 13. <IMAGE>

Description

OPTICAL DISPLAY APPARATUS The present invention relates to an optical display apparatus and is particularly, although not exclusively, concerned with head-up or head-down display apparatus which find utility, for example, in a fighter aircraft.
As modern fighter aircraft become faster, there is an increasing requirement to provide a pilot with accurate and readily understandable real-time information. In an attempt to meet this requirement, colour display systems have been designed which readily enable the presentation of different pieces of information to the pilot in different colours. Such systems facilitate rapid distinguishability of the different pieces of information.
Systems of this type, however, tend to become rather complex, bulky and expensive and do not necessarily provide a high degree of resolution of image for presentation to the pilot.
An aim of this invention is to provide an optical display apparatus which overcomes the aforementioned disadvantages in a relatively simple, efficient and inexpensive manner.
According to the present invention there is provided an optical display apparatus for presentation of a composite image from images from two separate image sources to a viewer, the apparatus comprising a first optical channel including a first image source which transmits a first light beam in a relatively narrow spectral wavelength band of the spectral range of the eye, a second optical channel including a second image source which transmits a second light beam in a different and relatively broad spectral wavelength band of the spectral range of the eye, and beam combining means for receiving said first and second light beams whereby the first beam is transmitted and the second beam is reflected in the same direction within a single common light beam, wherein the first optical channel is a high resolution optical channel and the second optical channel is a low resolution optical channel.
Preferably the first optical channel is arranged for operation within the green spectral wavelength band while the second optical channel is arranged for operation in the spectral wavelength band extending to cover colours other than green.
The first image source may take the form of a monochromatic high resolution green cathode ray tube.
The second image source may take the form of either a conventional three-gun three-colour cathode ray tube in which only the red and blue guns are used, or a flat colour display device, preferably a back illuminated liquid crystal display device or alternatively an electroluminescent display device.
It is envisaged that both the first and second image sources may take the form of flat display devices.
The beam combining means in one arrangement of the display apparatus may be dichroic. In another arrangement, the beam combining means may take the form of a diffractive or holographic optical element.
The beam combining means may take the form of a cube comprising two contacting 45" prisms wherein at least one of the contacting faces of the prisms includes either a dichroic film or a holographic optical element.
In another arrangement of the display device the beam combining means may take the form of a relatively thin plate of optically flat glass incorporating either a dichroic film or holographic optical element on one of the optically flat surfaces.
In the display arrangements including the cube as a beam combiner, it is preferable for a common lens element to be included in the path of the single common light beam output from the beam combiner.
In the above mentioned arrangements it is also preferable for a folding mirror to be included in the path of the single common light beam following the common lens element.
The optical display arrangements incorporated herein may incorporate a diffractive holographic optical element or a partial reflection means for transmitting the composite image to the viewer and this is usually disposed in the path of the single common light beam at an angle to the viewer's straight ahead line-of-sight.
A further lens element is preferably included in the path of the single common light beam immediately before the partial reflection means.
In the arrangement where the beam combining means takes the form of a plate, a first lens element is preferably included in the path of the first light beam output from the cathode ray tube and a second lens element is preferably included in the path of the second light beam output from the liquid crystal display.
The invention will be more readily understood from the following description of several exemplary embodiments which should be read in conjunction with the accompanying drawings in which: Fig. 1 illustrates a schematic diagram of one arrangement of the apparatus in accordance with this invention; Fig. 2 illustrates a schematic diagram of a variant arrangement of the apparatus in accordance with this invention; Fig. 3 illustrates a schematic diagram of a further variant arrangement of the apparatus in accordance with this invention; and, Fig. 4 illustrates a schematic diagram of yet a further variant arrangement of the apparatus according to this invention.
Before discussing the detailed construction of the optical display apparatus it is appropriate to appreciate the general principle by which this particular apparatus is able to provide an improved display image.
The arrangement is based on the fact that the eye/brain sensory system has the characteristic that it will recognise the combination of a high resolution picture in the central part of the spectral response range of the eye, in the green say, with a low resolution picture in any or all of the remainder of the spectrum, as sharp and acceptable as a viewable scene.
Referring now to the drawings, it should be understood that, for simplicity, like components in the various embodiments shown in Figs. 1 to 4 have been identically designated.
Referring particularly to Fig. 1, it will be seen that the arrangement shown incorporates two cathode ray tubes (c.r.t.'s) 1 and 2 arranged orthogonally with respect to one another. The screens 3 and 4, upon which images are formed, each face a dichroic beam combiner which takes the form of a cube comprising two 45" prisms 6 and 7 with at least one of the contacting surfaces of one of the prisms being dichroically treated, for example, by the deposition of a dichroic film HD.
Cathode ray tube 1 is a monochromatic high resolution green tube which transmits a high resolution image in a relatively narrow wavelength band for a high resolution optical channel H, whereas cathode ray tube 2 is a conventional low resolution three-gun three-colour (red, blue and green) tube which transmits a low resolution image in a relatively broad wavelength band for a low resolution optical channel L.
In the display apparatus, it is arranged fbr only the red and blue guns of the cathode ray tube 2 to be used. The other colour, required for providing a full colour composite image for presentation to the pilot or viewer E being obtained from the high resolution optical channel H.
Thus, in operation, the image from c.r.t. 1 at a first spectral wavelength (green) is transmitted in a first light beam by the dichroic combiner 5, whereas the image from the other c.r.t. 2 at a second spectral wavelength (including all other colours, other than green, of the spectral wavelength band) in a second light beam is reflected by the dichroic combiner 5. The first and second light beams are thus combined in a single common light beam and transmitted through a common lens element 8 located adjacent the dichroic combiner 5 and transmitted onward to a folding mirror 9 of conventional form.
The single common beam is transmitted through a further lens element 10 to a conventional partial reflector 11 inserted at an angle to the viewer's straight-ahead line of sight.
The single common light beam is received on the front of the reflector 11 (the viewer's E side) and the images from the two image sources (c.r.t.'s 1 and 2) superimposed on the external view as seen by the viewer E through the partial reflector 11.
Referring now to Fig. 2 this is substantially identical with the arrangement shown in Fig. 1 except that the c.r.t. 2 is replaced by a back-illuminated colour liquid crystal display LCD.
This display is flat and consequently does not consume as much space as the equivalent c.r.t. display. This is a distinct advantage when space is limited as is the case in a fighter aircraft cockpit.
The operation of the arrangement of Fig. 2 is identical with that described for Fig. 1, the image for the low resolution optical channel L being generated by the liquid crystal display LCD instead of the c.r.t. 2.
Referring now to Fig. 3 which shows a very similar arrangement to Fig. 1 except that the cube dichroic beam combiner has been dispensed with. The beam combining fuction is in this case performed by a modified folding mirror 5 where the low resolution channel image source is positioned directly below the mirror.
The folding mirror in this arrangement takes the form of a relatively thin plate of optically flat glass which includes a dichroic film HD on one of its surfaces.
This arrangement requires the c.r.t. 1 to be relatively close to a first lens element 8 and of course requires the addition of a similar second lens element 12 arranged in relation to the c.r.t. 2 in a manner similar to the first lens element 8 in relation to c.r.t. 1 of Fig 3.
While this arrangement will not be as heavy as the arrangement of Fig. 1 and Fig. 2 its operation is substantially identical with that described in respect of the arrangement illustrated in Fig. 1 and Fig. 2.
Referring finally to Fig. 4, this is substantially identical with that arrangement shown in Fig. 3 except that in the manner of the arrangement of Fig. 2, the low resolution channel c.r.t. 2 is replaced by a back illuminated colour liquid crystal display LCD. The liquid crystal display also requires the addition of a second lens element 12 as is required for the c.r.t. 2 in Fig 3.
This arrangement provides similar advantages as accrued, with the arrangement of Fig. 2 and is even more compact providing an additional option of the apparatus which would find particular utility in an aircraft cockpit where equipment mounting space is limited. Otherwise the arrangement of Fig. 4 operates in a manner substantially similar to that described in relation to the arrangement illustrated in Fig. 3.
It will be apparent to those skilled in the art that the low resolution optical channel L may employ other types of cathode ray tube to produce the two colours red and blue without departing from the features of this invention. One such type, for instance, is that known as a 'penetron' c.r.t. which is also known as a 'punch through' c.r.t.
It will be appreciated by those skilled in the art that the beam combiner 5 and the reflection means 11 may incorporate a diffractive or holographic optical element HD, 13, arranged for operation either in the transmit or reflection modes as appropriate.
It is envisaged that, subject to the availability of suitable high resolution devices, the image source of the high resolution optical channel H may, instead of employing a cathode ray tube, employ a flat colour display device.
While this invention has been described in relation to employment of flat display devices of the back lit liquid crystal display type by way of example, it will be apparent to those skilled in the art that other types of flat display devices may be employed, for instance, an electroluminescent type display device.

Claims (28)

1. Optical display apparatus for presentation of a composite image from images from two separate image sources to a viewer, the apparatus comprising a first optical channel including a first image source which transmits a first light beam in a relatively narrow spectral wavelength band of the spectral range of the eye, a second optical channel including a second image source which transmits a light beam in a different and relatively broad spectral wavelength band of the spectral range of the eye, and beam combining means for receiving said first and second light beams whereby the first beam is transmitted and the second beam is reflected in the same direction within a single common light beam, wherein the first optical channel is a high resolution optical channel and the second optical channel is a low resolution optical channel.
2. Optical display apparatus as claimed in claim 1, wherein the first optical channel is arranged for operation within the green spectral wavelength band.
3. Optical display apparatus as claimed in claim 2, wherein the second optical channel is arranged for operation in the spectral wavelength band extending to cover colours other than green.
4. Optical display apparatus as claimed in claim 1, 2 or 3, wherein the first image source is a monochromatic high resolution green cathode ray tube.
5. Optical display apparatus as claimed in claim 1, 2 or 3, wherein the first image source is a high resolution green flat display device.
6. Optical display apparatus as claimed n claim 4 or 5, wherein the second image source is a conventional three-gun three-colour cathode ray tube in which only the red and blue guns are used.
7. Optical display apparatus as claimed in claim 4 or 5, wherein the second image source is a flat colour display device.
8. Optical display apparatus as claimed in claim 7, wherein the flat colour display device is a back illuminated liquid crystal display device.
9. Optical display apparatus as claimed in claim 7, wherein the flat colour display device is an electroluminescent display device.
10. Optical display apparatus as claimed in any one preceding claim, wherein the beam combining means incorporates a dichroic film.
11. Optical display apparatus as claimed in any one of claims 1 to 9, wherein the beam combining means incorporates diffractive or holographic optical element.
12. Optical display apparatus as claimed in claim 10 or 11, wherein the beam combining means comprises a cube comprising - two contacting 45" prisms.
13. Optical display apparatus as claimed in claim 10 or 11, wherein the beam combining means comprises a relatively thin plate of optically flat glass.
14. Optical display apparatus as claimed in claim 13, wherein a first lens element is included in the first light beam output from the monochromatic cathode ray tube.
15. Optical display apparatus as claimed in claim 14, wherein a second lens element is included in the second light beam output from the flat colour display device.
16. Optical display apparatus as claimed in claim 10, 11 or 12, wherein a common lens element is included in the path of the single common light beam output from the beam combiner.
17. Optical display apparatus as claimed in claim 16, wherein a folding mirror is included in the path of the single common light beam following the common lens element.
18. Optical display apparatus as claimed in any preceding claim, wherein a reflection means is included in the path of the single common light beam at an angle to the viewers straight ahead line-of-sight.
19. Optical display apparatus as claimed in claim 18, wherein a further lens element is included in the path of the single common light beam immediately before the reflection means.
20. Optical display apparatus as claimed in claim 19, wherein the reflection means is constituted by a diffractive or holographic optical element.
21. Optical display apparatus as claimed in any of claim 19, wherein the reflection means is a partial reflector.
22. Optical display apparatus for presentation of a composite image derived from first and second component images, wherein the apparatus comprises: a first optical channel having a first image source operable to transmit a first light beam in a first wavelength band which is part of the spectral wavelength range of the human eye; a second optical channel of lower resolution than the first optical channel and having a second image source operable to transmit a second light beam in a second wavelength band occupying the spectral wavelength range of the human eye, the second wavelength band covering a broader range of wavelengths than the first wavelength band; and beam combining means for receiving the first and second light beams and optically combining them to be transmitted both in the same direction as a single composite beam.
23. Apparatus according to claim 18, wherein the first image source is a monochromatic source.
24. Apparatus according to claim 18, wherein the first image source is operable to generate radiation only in the green part of the spectral range of the human eye.
25. Apparatus according to claim 20, wherein the second image source is operable to generate radiation at shorter and longer wavelengths than radiation in the green part of the spectral range of the human eye.
26. Apparatus according to claim 21, wherein the second image source is a cathode ray tube having a plurality of electron guns.
27. Apparatus according to claim 22, wherein the beam combining means comprises a pair of 45" prisms.
28. Optical display apparatus substantially as herein described with reference to, and as shown, in the accompanying drawings.
GB8918119A 1988-09-20 1989-08-08 Optical display apparatus Withdrawn GB2222892A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB888822120A GB8822120D0 (en) 1988-09-20 1988-09-20 Optical display apparatus

Publications (2)

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GB8918119D0 GB8918119D0 (en) 1989-09-20
GB2222892A true GB2222892A (en) 1990-03-21

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GB888822120A Pending GB8822120D0 (en) 1988-09-20 1988-09-20 Optical display apparatus
GB8918119A Withdrawn GB2222892A (en) 1988-09-20 1989-08-08 Optical display apparatus

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2244569A (en) * 1990-06-01 1991-12-04 Delco Electronics Corp Image source for head-up display
EP0492640A1 (en) * 1990-12-27 1992-07-01 Canon Kabushiki Kaisha Projector using a hologram
FR2691549A1 (en) * 1992-05-22 1993-11-26 Thomson Csf Chromatic light separator and image projector using such a separator.
EP0646823A2 (en) * 1993-09-30 1995-04-05 Hughes Aircraft Company Automotive instrument 3-d virtual image display
EP0675476A1 (en) * 1994-03-30 1995-10-04 Nippondenso Co., Ltd. Liquid crystal display device
WO1999064914A1 (en) * 1998-06-08 1999-12-16 Vectop Ltd. Optical system for directing an auxiliary image towards an observer so as to be superimposed onto a main image
FR2790562A1 (en) * 1999-03-02 2000-09-08 Sextant Avionique Optical device for mixing images applicable to visor or a helmet, e.g. viewfinder helmet for pilots or night vision helmet
WO2000073843A1 (en) * 1999-05-26 2000-12-07 Telefonaktiebolaget Lm Ericsson (Publ) A display for head mounting
CN101626644B (en) * 2008-07-11 2010-12-29 台达电子工业股份有限公司 Optical collector used for illumination system and illumination system
US9244275B1 (en) * 2009-07-10 2016-01-26 Rockwell Collins, Inc. Visual display system using multiple image sources and heads-up-display system using the same
US11442272B2 (en) * 2020-03-12 2022-09-13 Facebook Technologies, Llc High-resolution liquid crystal displays

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1423947A (en) * 1973-04-30 1976-02-04 Hughes Aircraft Co Holographic lens and liquid crystal image source for head-up display
GB2132376A (en) * 1982-12-17 1984-07-04 Ferranti Plc Head-up display
GB2149140A (en) * 1983-10-31 1985-06-05 Gec Avionics Head-up display systems

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1423947A (en) * 1973-04-30 1976-02-04 Hughes Aircraft Co Holographic lens and liquid crystal image source for head-up display
GB2132376A (en) * 1982-12-17 1984-07-04 Ferranti Plc Head-up display
GB2149140A (en) * 1983-10-31 1985-06-05 Gec Avionics Head-up display systems

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2244569A (en) * 1990-06-01 1991-12-04 Delco Electronics Corp Image source for head-up display
EP0492640A1 (en) * 1990-12-27 1992-07-01 Canon Kabushiki Kaisha Projector using a hologram
JPH04232904A (en) * 1990-12-27 1992-08-21 Canon Inc Projection type display device using hologram
US5404234A (en) * 1990-12-27 1995-04-04 Canon Kabushiki Kaisha Projector using a hologram
JP2810241B2 (en) 1990-12-27 1998-10-15 キヤノン株式会社 Projection display device using hologram
FR2691549A1 (en) * 1992-05-22 1993-11-26 Thomson Csf Chromatic light separator and image projector using such a separator.
EP0572292A1 (en) * 1992-05-22 1993-12-01 Thomson-Csf Colour beamsplitter and image projector using the same
US5546200A (en) * 1992-05-22 1996-08-13 Thomson-Csf Chromatic light separator and picture projector using a chromatic light separator
EP0646823A3 (en) * 1993-09-30 1996-06-12 Hughes Aircraft Co Automotive instrument 3-d virtual image display.
EP0646823A2 (en) * 1993-09-30 1995-04-05 Hughes Aircraft Company Automotive instrument 3-d virtual image display
EP0675476A1 (en) * 1994-03-30 1995-10-04 Nippondenso Co., Ltd. Liquid crystal display device
US5572342A (en) * 1994-03-30 1996-11-05 Nippondenso Co., Ltd. LCD, light source, and hemispheric concave reflector mounted individually to a support and part of a heads up display
WO1999064914A1 (en) * 1998-06-08 1999-12-16 Vectop Ltd. Optical system for directing an auxiliary image towards an observer so as to be superimposed onto a main image
US6301052B1 (en) 1998-06-08 2001-10-09 Vectop Ltd. Optical system for directing an auxiliary image towards an observer so as to be superimposed onto a main image
FR2790562A1 (en) * 1999-03-02 2000-09-08 Sextant Avionique Optical device for mixing images applicable to visor or a helmet, e.g. viewfinder helmet for pilots or night vision helmet
WO2000073843A1 (en) * 1999-05-26 2000-12-07 Telefonaktiebolaget Lm Ericsson (Publ) A display for head mounting
CN101626644B (en) * 2008-07-11 2010-12-29 台达电子工业股份有限公司 Optical collector used for illumination system and illumination system
US9244275B1 (en) * 2009-07-10 2016-01-26 Rockwell Collins, Inc. Visual display system using multiple image sources and heads-up-display system using the same
US11442272B2 (en) * 2020-03-12 2022-09-13 Facebook Technologies, Llc High-resolution liquid crystal displays

Also Published As

Publication number Publication date
GB8822120D0 (en) 1988-12-14
GB8918119D0 (en) 1989-09-20

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