GB1581926A

GB1581926A - Visual display apparatus

Info

Publication number: GB1581926A
Application number: GB723176A
Authority: GB
Original assignee: Elliott Brothers London Ltd
Current assignee: Allard Way Holdings Ltd
Priority date: 1977-05-18
Filing date: 1977-05-18
Publication date: 1980-12-31

Description

(54) IMPROVEMENTS IN OR RELATING TO VISUAL DISPLAY APPARATUS ,(71) We,- ELLIOT BROTHERS (LONDON) LIMITED, of Marconi House, New Street, Chelmsford,-Essex CMl 1PL, a British company, do hereby declare the invention, for which we-pray that a patent may be granted to..us, and the method by which it is two be performed to be particularly -described in and by the following statement: This invention relates to visual display apparatus for use- in -enabling an observer enclosed within a vehicle such as an aircraft or a tank to observe a scene outside the vehicle independently of normal vision through a.windscreen, and has an important application to such display apparatus for use at night or in conditions of poor visibility.

According to the present invention a visual display apparatus for use in a visual display system for enabling an observer within a vehicle to observe an image of a scene outside the vehicle comprises : - a mounting arrangement adapted for location on the observer's head; a viewing arrangement carried on said mounting arrangement for providing.a display in the observer's normal field of view when the mounting arrangement is worn; .and optical fibre means for transmitting said image to said viewing arrangement, the visual display apparatus further including part of a position sensing arrangement for providing an output signal indicative of the position of said mounting arrangement with respect to at least one plane.in an.external frame of reference.

The output signal may be used to control the image of the scene being observed so that the-image..changes. with movement of the observer's head.

Preferably said part of the position sensing arrangement includes means carried on said mounting arrangement for emitting radiation to be sensed by..a- sensor fixed within said frame of reference. The mounting arrangement may be constituted by, incorporated in, or arranged to be attached to a helmet worn by the observer. -The optical fibre means may then be supported on the mounting arrangement so that it extends from the front to the rear of the helmet.

Preferably said mounting arrangement incorporates a helmet to be worn by said observer and support means for detachably securing said visual display apparatus on said helmet. In this way the mounting arrangement can be transferred from one observer's helmet to another.

Preferably said mounting arrangement includes pivot means to allow said support means to be pivotted between a position in which said viewing arrangement is adjacent at least one eye of said observer and a position - in which said viewing arrangement-is clear of the normal field of view of said observer. Preferably said pivot means comprises two lugs attached to said support means, each lug being receivable in a respective one of two sockets located-one on each side of said helmet, and a springloaded pin attached to said. support means for engagement.in either of two holes associated with said helmet, -which holes define said two positions of the support means.

Preferably the viewing arrangement is monocular.

-The.image of the scene may be derived from an- .image producing arrangement mounted on the.vehicle. The- image.producing arrangement may be of a kind which will operate in low ambient light or of a kind which will respond to radiation in the infra-red spectrum.

will respond to radiation in the infra-red spectrum.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side view of the head of a helicopter pilot wearing a protective helmet on which is mounted a viewing head and other components.of a visual display apparatus in-accordance with the invention; Figure 2 is a side view of a cathode ray tube and other components which may be used to introduce the image into the optical fibre means of the visual display apparatus in accordance with the invention Figure 3 is a front view of the helicopter pilot's head and apparatus shown in Figure 1; Figure 4 is a plan view of the apparatus shown in Figure 1; Figure 5 is a perspective view of a position sensing arrangement which may be used in conjunction with the visual display apparatus in accordance with the invention, and Figure 6 is a perspective view of a tele vision camera mounted on the side of a helicopter and forming part of the image producing arrangement.

Referring to the drawings, the visual display apparatus comprises a framework 1 formed from tubular members of a light but rigid material such as aluminium, which supports a monocular viewing head 2 in an operative position so that an eyepiece 3 is adjacent the right eye of a helicopter pilot 4. The framework 1 is detachably mounted on a protective helmet 5 worn by the helicopter pilot 4 and.arranged so that it can be pivoted between the operative position shown in full line in Figure 1 and a 'parked' position, indicated by the chain line 7, in which the viewing head 2 does not obstruct the pilot's normal view forward. To this end two cylindrical lugs 8 secured to respective side members 9 of the framework 1 are located in co-operating holes 10 provided in bosses 11 secured to the helmet 5, while a spring-loaded detent pin 12 mounted on a front member 13 of the framework 1 is arranged to engage in either of two holes 14 in.an upstanding vane 15 on the front of the helmet 5.

The viewing head 2 accommodates one end 16 of a flexible cable 17 containing a multiplicity of optical fibres 18 arranged to transmit'to the viewing head 2 an image displayed on the screen 19 of a cathode ray tube 20 contained in the housing 21. The image on the screen 19 is derived from signals provided by a television camera 40 mounted for movement on gimbals 41 and 42 located on an exterior surface of the air frame 43 of the helicopter and rotated.in elevation and azimuth by electric motors 44 and 45 respectively. Preferably the television camera 40 is of the kind which.will operate in low ambient light or will respond to radiation in the infra-red spectrum. A lens system 25 is arranged to focus. the image from the screen 19 on to the end 26 of the flexible cable 17 which is connected to the housing 21. The viewing head 2 also contains a collimating optical system comprising a lens 27 and a lens 28 mounted in the eyepiece 3. A mirror 29 disposed at an angle of 45 degrees to the lens 28 and a lens 30 parallel to the end 16 of the flexible cable 17 enables the end 16 of the flexible cable 17 to be viewed through the eyepiece 3 although the path between the end 16 of the flexible cable 17 and the eyepiece turns through 90 degrees.

Also mounted on the framework 1 is a plurality of point light sources in the form of light emissive diodes 31 which form part of a position sensing arrangement of the kind described in U.K. Patent Specification No. 1,550,339. As can be seen in Figure 5, each light emissive diode 31 is associated with a light sensor 32 mounted on the airframe 43 of the helicopter. Each light sensor 32 comprises an opaque housing 33 provided with an aperture 34 formed by two mutually inclined rectilinear slits 35 and 36 and accommodating a linear array 37 of light sensitive elements. The linear array 37 of light sensitive elements is spaced from the aperture 34 and so orientated relative thereto, that laminar light beams 38 and 39 developed by the rectilinear slits 35 and 36 from the light emissive diode 31 intersect the linear array 37, the positions of intersection constituting a measure of the angular position about two orthogonal axes of the light emissive diode 31 to the sensor 32.

The sensors 32 are calibrated to provide output signals indicative of the position of the light emissive diodes 31 relative to the sensors 32 and thus indicative of the position of the framework 1 relative to the. sensors 32. The output signals from the sensors 32 are arranged to energise electric motors 44 and - 45 arranged to adjust the angular positions in elevation and in azimuth of the television camera in accordance with the movement of the framework 1 brought about by. the pilot's head 4. - In the use of the visual display apparatus the television camera 40 provides an image of the scene outside the helicopter which is displayed on the screen 19 of the cathode ray tube 20. The image displayed on the screen 19 is transmitted by the flexible cable 17 of optical fibres 18 to the lens 30 in the viewing head 2 and is reflected by the mirror 29 through the lenses 27 and.28 to the pilot's eye which is adjacent the ceyepiece 3. Should the helicopter pilot wish to change the scene displaced on the screen 19 of the cathode ray tube 20, .the pilot 4 moves his head in the appropriate direction in azimuth or in elevation as the case may be, thus moving the framework 1 in.a corresponding direction. The movement of. the framework 1 is sensed by the light emissive diodes 31 and co-operating light sensors 32, which provide output signals indicative of the movement, these signals being used to adjust the attitude of the television camera 40 in elevation or in azimuth to change the image displayed.

Although the position sensing arrangement used in the embodiment of the invention described above utilizes light emissives diodes, it is envisaged that other kinds of position sensing arrangements may be used, for example, position sensing arrangements utilizing magnetic elements.

Moreover although the invention has been described with reference to visual display apparatus mounted in a helicopter, the invention can be adapted for use in other vehicles, for example, tanks or other types of aircraft. It is also envisaged that the ima may contain information relating to navigation,weapon-aiming or other matters in addition to an exterior scene.

WHAT WE CLAIM IS:1. A visual display apparatus for use in a visual display system for enabling an observer within a vehicle to observe an image of a scene outside said vehicle comprising: a mounting arrangement for location on the observer's head; a viewing arrangement carried on said mounting arrangement for providing a display in the observer's normal field of view when the mounting arrangement is worn; and optical fibre means carried on said mounting arrangement for transmitting said image to said viewing arrangement, the visual display apparatus further including part of a position sensing arrangement for providing an output signal indicative of the position of said mounting arrangement with respect to at least one plane in an external frame of reference.

2. A visual display apparatus as claimed in claim 1 wherein said part of the position sensing arrangement includes means carried on said mounting arrangement for emitting radiation to be sensed by a sensor fixed within said frame of reference.

3. A visual display apparatus as claimed in claim 1 or 2 wherein said mounting arrangement incorporates a helmet to be worn by said observer and support means for detachably securing said visual display apparatus on said helmet.

4. A visual display apparatus as claimed in claim 3 wherein said mounting arrangement includes pivot means to allow said support means to be pivotted between a Dosition in which said viewing arrangement is adjacent at least one eye of said observer and a position in which said viewing arrangement is clear of the normal field of view of said observer.

5. A visual display apparatus as claimed in claim 4 wherein said pivot means comprises two lugs attached to said support means, each lug being receivable in a re spective one of two sockets located one on each side of said helmet, and a springloaded pin attached to said support means for engagement in either of two holes associated with said helmet, which holes define said two positions of the support means.

6. A visual display apparatus as claimed in any preceding claim wherein the view ing arrangement is monocular.

7. A visual display apparatus substantiallv as hereinbefore described with reference to the accomnanying drawings.

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Claims

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diodes 31 and co-operating light sensors 32, which provide output signals indicative of the movement, these signals being used to adjust the attitude of the television camera 40 in elevation or in azimuth to change the image displayed.

Although the position sensing arrangement used in the embodiment of the invention described above utilizes light emissives diodes, it is envisaged that other kinds of position sensing arrangements may be used, for example, position sensing arrangements utilizing magnetic elements.

Moreover although the invention has been described with reference to visual display apparatus mounted in a helicopter, the invention can be adapted for use in other vehicles, for example, tanks or other types of aircraft. It is also envisaged that the ima may contain information relating to navigation,weapon-aiming or other matters in addition to an exterior scene.

WHAT WE CLAIM IS:1. A visual display apparatus for use in a visual display system for enabling an observer within a vehicle to observe an image of a scene outside said vehicle comprising: a mounting arrangement for location on the observer's head; a viewing arrangement carried on said mounting arrangement for providing a display in the observer's normal field of view when the mounting arrangement is worn; and optical fibre means carried on said mounting arrangement for transmitting said image to said viewing arrangement, the visual display apparatus further including part of a position sensing arrangement for providing an output signal indicative of the position of said mounting arrangement with respect to at least one plane in an external frame of reference.
2. A visual display apparatus as claimed in claim 1 wherein said part of the position sensing arrangement includes means carried on said mounting arrangement for emitting radiation to be sensed by a sensor fixed within said frame of reference.
3. A visual display apparatus as claimed in claim 1 or 2 wherein said mounting arrangement incorporates a helmet to be worn by said observer and support means for detachably securing said visual display apparatus on said helmet.
4. A visual display apparatus as claimed in claim 3 wherein said mounting arrangement includes pivot means to allow said support means to be pivotted between a Dosition in which said viewing arrangement is adjacent at least one eye of said observer and a position in which said viewing arrangement is clear of the normal field of view of said observer.
5. A visual display apparatus as claimed in claim 4 wherein said pivot means comprises two lugs attached to said support means, each lug being receivable in a re spective one of two sockets located one on each side of said helmet, and a springloaded pin attached to said support means for engagement in either of two holes associated with said helmet, which holes define said two positions of the support means.
6. A visual display apparatus as claimed in any preceding claim wherein the view ing arrangement is monocular.
7. A visual display apparatus substantiallv as hereinbefore described with reference to the accomnanying drawings.