GB2416859A

GB2416859A - Articulated light guide apparatus

Info

Publication number: GB2416859A
Application number: GB0417288A
Authority: GB
Inventors: Iain Chapman
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-08-03
Filing date: 2004-08-03
Publication date: 2006-02-08
Also published as: GB0417288D0; WO2006013356A1

Abstract

The present invention provides articulated image guide apparatus for guiding light from an image generator (3)to a user of the apparatus comprising: a plurality of linking member (2); a plurality of joint members each connected between a pair of the linking members and permitting articulation of each linking member with respect to an adjacent linking member; input means at a first end of the image guide apparatus which can be directed at the image generator; and output means at a second end of the image guide apparatus which enables the user to view transmitted light; wherein, in use, light from an image generated by the image generator is received by the input means and then guided through the linking members and delivered at the output means to be viewed by the user, the apparatus delivering a virtual image directly to the eye(s) of the user.

Description

IMAGE GUIDE APPARATUS

The present invention relates to an image guide apparatus. More specifically, but not exclusively, there is provided a virtual reality head mounted device.

Virtual reality systems are becoming popular in a wide variety of applications including simulation of complex objects, role-play computer games and entertainment as well as training for doctors and surgeons. Such systems allow access to situations in a "virtual" world, for example building a prototype of a bridge or learning to carry out open-heart surgery.

Virtual reality displays may also use the output of cameras in the real world as their source, to view the inside of a nuclear reactor for instance.

Virtual reality systems appear in many different forms, but the present invention relates to a virtual reality system that is designed to be placed on the head of the user.

The majority of head mounted devices on the market today have Liquid Crystal Displays (LCD) or Cathode Ray Tube (CRT) Screens which are firmly attached to a headset on the user's head. Lenses and/or mirrors within an image guide direct the images produced by an image generator to the user's eyes.

It is known from US 4,048,653 (Spooner) and US 4,411,627 (Breglia et al.) to have a head mounted device which comprises a movable image guide that directs light from a light source or image generator to the headset of a user from where the light or image is projected onto a screen located in front of the user. The screens onto which the images are projected - 2 must be sufficiently large to show the whole of the projected images and to prevent small movements of the user's head from resulting in the user seeing the edge of the screen. The screens are thus expensive and cumbersome.

According to the present invention there is therefore provided an articulated image guide apparatus for guiding light from an image generator to a user of the apparatus comprising: a plurality of linking members; a plurality of joint members each connected between a pair of the linking members and permitting articulation of each linking member with respect to an adjacent linking member; input means at a first end of the image guide apparatus which can be directed at the image generator; and output means at a second end of the image guide apparatus which enables the user to view transmitted light; wherein, in use, light from an image generated by the image generator is received by the input means and then guided through the linking members and delivered at the output means to be viewed by the user, the apparatus delivering a virtual image directly to the eye(s) of the user.

The joint members are each preferably provided with one or more mirrors or prisms to guide light through the image guide apparatus.

Viewed from a further aspect, the present invention relates to image guide apparatus for guiding light from an image generator to an user of the - 3 - apparatus comprising: input means at a first end of the image guide apparatus which can be directed at the image generator; output means at a second end of the image guide apparatus which enables the user to view light guided though the apparatus; and movable optical means defining a movable optical path between the input means and the output means; the movable optical means comprising a series of reflective elements provided at intervals along the optical path; wherein, in use, light from an image generated by the image generator is received by the input means and then guided along the movable optical path defined by the movable optical means and delivered at the output means to be viewed by the user, the apparatus delivering a virtual image to the eye(s) of the user.

The reflective elements may be mirrors or prisms and the term is not intended to refer to the internal reflectance of light in an optical fibre. As such, the optical means is not a fibre optic cable.

The image guide apparatus is preferably adapted for use with an image generator which comprises a screen on which the generated image or images is displayed; the input means comprises a system of lenses to optically reduce in size the displayed generated image or images prior to onward transmission of the image through the image guide apparatus. The image generator may comprise a single screen on which different parts of the complete image to be guided through the image guide apparatus is displayed. - 4 -

Preferably, however, a plurality of screens are provided each of which displays a portion of the complete image.

The input means may translate parts of the image displayed on at least one screen so that the image parts are adjacent to each other prior to onward guidance through the link members and the joint members.

Alternatively, first and second images may be generated by the image generator. These first and second images are preferably polarised in first and second directions, the first and second directions not being parallel to each other. The first and second images are preferably polarised orthogonally relative to each other. The polarised first and second images are preferably combined in a single image suitable for guiding to the output means. This process is particularly advantageous as the combined image may be guided through a central portion of the articulated guide apparatus such that distortion and the like which may otherwise occur at the edge of the image may be reduced.

Irrespective of whether the first and second images guided through the image guide apparatus are translated so that they are adjacent to each other or transposed on top of each other, the output means preferably splits the transmitted image into two separate images, one image for each of the user's eyes.

The image guide apparatus may further comprise

-

sensor means for producing an indication of the path in which the transmitted image passes from the input means to the output means. The image guide apparatus may further comprise correction means for effecting correction of the transmitted image. The correction means may, for example, compensate for distortion or changes in orientation of the image during transmission. The sensor means may, for example, comprise rotation sensors for indicating rotation of a mirror relative to one or more of the other mirrors.

The sensor means may advantageously also allow the position of the output means, and thereby the head of the user relative to the input means to be determined.

The sensor means may additionally comprise photosensitive cells for producing signals indicative of the orientation of the transmitted image at the output means.

The correction means may comprise a rotatable prism and preferably also rotation means for rotating the prism. Alternatively, the correction means may comprise image display control means operable to control the orientation of an image or images generated by the image generator.

The image guide apparatus may further comprise a tracking system for tracking movement of one or both of the user's pupils. The tracking system may comprise a camera for recording the image of one or both of the user's pupils and image display control means for varying the image generated by the image generator in response to movement of the pupil or pupils. The camera means is preferably an infra-red camera and the apparatus preferably additionally - 6 - comprises infra-red illumination means for illuminating the user's pupil(s).

In arrangements comprising one or more mirrors, each mirror may be movable relative to the joint member in which it is housed. Motor means may be provided to move each mirror and control means may also be provided to control the motor means to position each mirror so that a line normal to the mirror surface bisects an angle between the link members adjacent the joint member.

In order to minimise deterioration of the image as it is guided from the input means to the output means, at least one telecentric relay is preferably provided. Telecentric relays are unaffected by the mirrors or prisms and may be evenly spaced along the optical path.

To counteract the weight of the image guide apparatus, a counter-balance system is preferably provided at least partially to balance the weight of the apparatus. The counter-balance may, for example, be a spring balance.

The output means is preferably connected to a headset to be worn by the user. The output means may be connected to the headset via a connected joint member which facilitates a pitching movement of the headset. The joint member adjacent to the connecting joint member preferably facilitates a rolling motion of the headset and, preferably, the second joint member from the connecting joint member facilitates a yawing motion of the headset. It will be appreciated, however, that any combination of joints which facilitate pitching, rolling and yawing may be provided to connect the headset to the guide apparatus. s

The term "virtual image" used herein refers to the formation in, for example, a plane mirror of an image of an object located in front of the mirror.

The rays reflected from the mirror appear to pass through a point behind the mirror and the resulting image cannot be received on a screen because the image is behind the mirror. The resulting image is therefore called a virtual image. It will, of course, be appreciated that the present invention is not limited to virtual images formed in plane mirrors.

For example, a virtual image may be formed from light passing through a diffuser screen before being guided into the eye(s) of the user by one or more lenses or optical guidance means.

Viewed from a still further aspect, the present invention relates to image guide apparatus for guiding light from an image generator to a user, the apparatus comprising an input means at the first end of the image guide apparatus and an output means at the second end of the image guide apparatus; the image guide apparatus including means for polarizing light from the image generator; wherein, in use, first and second images are generated by the image generator, the first and second images being polarized by the polarization means and combined into a single image.

The first and second images in said combined image are preferably polarised in first and second 8 - directions respectively; the first and second directions being angularly offset relative to each other. Preferably, the first and second images are polarised orthogonally. The apparatus preferably further comprises means to separate the two polarized images from said single image.

Viewed from a further aspect, the present invention relates to a method of guiding an image through an image guide apparatus, the method comprising the steps of: (a) generating first and second images; (b) polarising said first and second images; (c) combining the first and second polarised images into a single image.

The first and second images in said combined image are preferably polarised in first and second directions, said first and second directions being angularly offset relative to each other.

Alternatively, the first and second image may undergo elliptical or circular polarization with different phase differences between the electric and magnetic

field components of the propagated light.

The first and second images are preferably orthogonally polarised.

The method preferably further comprises separating the two polarized images from said single image.

Preferred embodiments of the present invention will now be described by way of example only and with 9 reference to the accompanying drawings, in which: Figure 1 is a front perspective view of an image guide apparatus according to the present invention.

Figure 2 is a view of the apparatus of Figure 1 with certain components shown transparent to reveal internal detail; Figure 3 is a back perspective view of the portion of the light guide apparatus of Figure 1 connected to the headset with certain components shown transparent to reveal internal detail; Figure 4 is a front perspective view of the light guide apparatus of Figure 1 between the headset and the input housing; Figure 5 is a back perspective view of the apparatus shown in Figure 5; Figure 6 is a perspective view of a bearing of the apparatus of Figure 1; Figure 7 is an exploded view of the apparatus of figure 6; Figure 8 is a further exploded view of the apparatus of figure 6; Figure 9 is a schematic flowchart which represents the apparatus of Figure 1; Figure 10 illustrates schematically the combination of images which takes place in the apparatus of figure 1; - 10 Figure 11 illustrates schematically an alternative method for combining images; Figure 12 is a perspective view of an alternative embodiment of the correction mechanism for an image guide apparatus; Figure 13 is a perspective view of a second alternative embodiment of the correction mechanism for an image guide apparatus; Figure 14 shows an exploded view of the apparatus of Figure 13; Figures 15 and 16 illustrate an image shown on a screen in a second embodiment of an image guide apparatus; Figures 17 and 18 illustrate images on a pair of screens in a third embodiment of an image guide apparatus; Figure 19 shows a composite image resulting from putting together the images shown on the screens in Figures 17 and 18; Figure 20 shows a front perspective view of a fourth embodiment of an image guide apparatus; Figures 1 and 2 show an image guide apparatus according to a first embodiment of the present invention. The image guide apparatus comprises a headset 1 and an image guide 2. At an end of the image guide remote from the headset 1 there is provided an input housing 3 in which monitor screens 4,5 are located. - 11

Left and right monitor screens 4,5 are provided within the housing 3 for the display of computer- generated images, with one image being displayed on each screen and there being two images in total. s

Objective lens assemblies 6,7 above the screens 4,5 reduce the area of each computer-generated image without reducing its resolution in order to prevent any loss in detail of the images.

The two separate images from the two objective assemblies pass through a polarising beamsplitter assembly 8. The resulting image passing out of the polarizing beamsplitter assembly 8 contains both the IS original images centred on the principal axis but orthogonally polarised. This resulting image is referred to herein as a combined image. Figure 10 shows this combination schematically.

The combined image then passes through the image guide 2. The image guide 2 contains a system of relay optics 9-20 (see also figure 3). In the first embodiment, the relay optics comprise a series of three telecentric relays and one magnifying telecentric relay, as shown schematically in figure 9.

In this embodiment two beamsplitters 8,21 and a Dove prism assembly 22 lie between the first two lens elements of the first telecentric relay. Accordingly the first lens 9,10 is duplicated - one for each objective lens assembly 6, 7. The provision of telecentric relays along the image guide apparatus advantageously helps to avoid deterioration of the image quality as it is guided to the headset 1.

At the output of the image guide, a polarising beamsplitter assembly 23 separates the two orthogonally polarized images, one for each eye. The images then pass through separate eyepiece assemblies 24,25 to the user's left and right eyes. Figure 10 shows this schematically. In this embodiment the beamsplitter assembly 23 allows the inter-pupillary S distance to be varied. The eyepieces 24,25 then deliver virtual images of screens 4,5 to the eyes of the user. The virtual images are focussed at some point between approximately loom and infinity, and this distance is preferably adjustable by moving elements of the eyepiece assemblies.

Referring now to Figures 4 and 5, the image guide 2 consists of joint members comprising rotating bearings 26-32, and linking members comprising mirror housings 33-44 and rigid sections 45-50. The relay optics 9-20 are held in place within the image guide.

Bearings 26-29, combined with rigid sections 45-46, permit a wide envelope of movement of the user's head.

Rigid bars 51,52 are mounted by bearings to holders 53,54,55. The holders 53,54,55 are in turn attached to the image guide 2. The central holder 54 is attached to the image guide 2 by a bearing 68 such that it is free to rotate about the same axis as the joint 28 that it is attached to. This arrangement of rigid bars 51,52 constrains the attitude of the fifth bearing 30, such that it remains orientated in a direction parallel to the direction of the first bearing 26. This ensures that bearings 30-32 combined with rigid sections 47-50 allow an extensive range of local yaw, roll, and pitch head movements for the user.

Springs 56,57 are provided to reduce or eliminate the weight of the image guide and headset bearing upon the user.

As can be seen in Figure 7, each mirror housing 33-44 contains a mirror 58. Apparatus known in the art may optionally be provided to finely align the mirror 58. The high-precision bearings 26-32 allow the mirror housings to rotate with respect to one another. Irrespective of the angle of rotation of each bearing 26-32, the mirror 58 still reflects the reflected image precisely towards the next mirror along the image guide 2.

Rotation of each of the bearings 26-32 does however affect the orientation of the image about the principal axis. For this reason, optical encoder assemblies 59-65 are provided on the bearings 26-32 to measure the degree of rotation of each bearing.

For example, Figures 7 and 8 show an optical encoder 66 for measuring the degree of rotation of the fourth mirror housing 36 relative to the third mirror housing 35. The bearing 28 comprises bearing elements 28a - 28e. The bearing elements 28a,28b and rotary encoder disk 67 are rigidly attached to the fourth mirror housing 36, bearing elements 28c, 28d,28e and the optical encoder 66 are rigidly attached to the third mirror housing 35 and the optical encoder 66 measures the rotation of the rotary encoder disk, and thus the relative rotation. This information is fed back electronically to a processor (not shown), which calculates the total angle of rotation of the transmitted image resulting from the combination of the rotations of all the joints together and thus the required correction. The correction is then effected by rotating Dove prism 22, mounted on bearings 69,70, to the corresponding angle with an electric motor 71 (as shown in Figure 2). Such corrections are made at a frequency which is high enough not to be perceptible to the user.

A beamsplitter 21 and a COD (charge coupled device) camera 72 (as shown in Figure 2) may optionally be used as a mechanism to track the user's pupils (direction of gaze). An image of the user's eyes is transmitted along the image guide in the opposite direction to the computer-generated image.

The image of the user's eyes may be lit by an infrared light source near the camera aperture and the camera can be an infrared camera.

The housing 3 which covers the screens and optical elements around the screens is substantially light-tight. The headset 1 holds the various optical elements at one end of the articulated image guide 2 rigidly against the user's head and preferably contains speakers 73 for 2D or 3D sound.

Figure 9 shows schematically the functioning of the apparatus and shows how the encoders provide signals which are processed to provide a control signal for a motor rotating the prism. As all the joints contain encoders, the output of the encoders can be used to determine the position of the user's head (relative to the input means). This can be used to alter the generated images, for instance to give the impression of looking around a room in response to head movements. Movements of the user's pupils can be treated in a similar way, using the image of the eyes recorded by the camera to alter the generated view, to increase the quality of the image generated in the direction of gaze, for instance.

In the above described embodiment, the eyepieces form virtual images of the final real images in the image guide. These last real images may optionally be focussed on diffusive or reflective screens, the eyepieces forming virtual images of the real images appearing on those screens. In such a case the use of a camera to distantly view an image the user's eyes Whilst linking members and joint members are easily distinguished in the above described embodiment, this need not be so. For example, several joint members and linking members may be manufactured as a single entity.

The two images from the objective assemblies may be combined in a different manner from that described above. Circular or elliptical polarization may be used, for instance. Alternatively the two images may be translated by translation means to close proximity without overlapping, and delivered through the image guide in this way, being separated in the equivalent manner at the other end. Figure ll shows this method schematically.

In the above described embodiment of the invention, two screens have been provided. However, the invention would also function with any number of screens. It is not necessary to have separate objective assemblies for each screen, but it would be possible to deliver images from more than two objectives through the image guide if required by the translation method described above, possibly in combination with a polarization technique. A single screen would not require polarization or translation at all. The apparatus may also be used as a monoscopic device.

With regard to the various optical systems, the number and type of assemblies and lenses used are not an essential feature of the invention, but can be optimised for each application. A greater or a lesser - 16 number of lenses could be used, and plane, concave or convex mirrors could be used in addition to or in place of some or all of the lenses.

It is understood that correction of aberrations will be effected for the optical system as a whole, and not necessarily for the individual components.

Distortion or lateral chromatic aberration of the image may be corrected by using the software or hardware that produces the image on the screen(s) .

The Dove prism may be replaced by a different prism or series of prisms, or by a series of mirrors.

Figure 12, for example, shows two Dove prisms 73,74 in series. Figures 13 and 14 show mirrors 75,76,77 mounted in a formation (with the mirror 75 and the mirror 77 being at 22.5 degrees to the mirror 76) on the bearings 78,79 and controlled by a motor 80. The net effect of this series of mirrors is equivalent to that of a K prism. Many other permutations also exist. The screens may alternatively be rotated to adjust the orientation of the image.

The Dove prism may be replaced by hardware or software that changes the orientation of the image on the display screen. This is illustrated schematically in Figures 15 and 16, which illustrate the rotation on a screen 81 of an image 82 from a first orientation in Figure 15 to a second orientation in Figure 16. To make more efficient use of screen area a single image can be split into sections 83,84,85,86 spread across the two screens 87 and 88 as shown in Figures 17 and 18, with a more complex arrangement of optical assemblies used to form the image of figure 19 from the components 83-86.

The orientation of the image at the user end of the image guide can be measured using photosensitive cells surrounding the required image transmission area. This would negate the need for rotation sensors on the articulated image guide bearings.

The mirrors 58 in the mirror housings, for example in the embodiment shown in Figure 7, need not be at 90 degrees to one another as described above and could, for example, lie at 110 degrees to one another.

The mirrors may be replaced by prisms.

In the image guide 2 each joint member can comprise a single mirror whose orientation is controlled so that a line perpendicular to the face of the mirror bisects the angle between the two adjacent linking members as is known in the art (see US 3,642,352 (Beach) or US 3,658,406 (Karube et al) for example). A mechanical system comprising gears, levers, electro-mechanical actuators or pulleys can be used to control the orientation of each mirror. The mirror can be moved in two or three dimension (for three dimensional movement the known Coude optics system may be used) (See US 5,1115,355 (Dunn) or US 5,204,785 (Tang et al) for example). If each joint member is constructed in this way, the orientation of the transmitted image should not be altered during transmission and thus it would not be necessary to measure the rotation of each joint or use a Dove prism to correct the orientation of the image. Similarly, a Dove prism (or equivalent) may be placed between each pair of rotating mirrors, and controlled to rotate by half the angle by which one mirror rotates with respect to the other. A mechanical system comprising gears, levers, electro-mechanical actuators or pulleys can be used to control the orientation of the Dove prism. - 18

The image guide can have more or less joints than described above.

In a further embodiment of the present invention shown in Figure 20, sliding parts 89, 90, 9l allow lengthening or shortening of a linking member in a direction parallel to the direction of travel of the transmitted image. Such an embodiment would make use of an optical relay with individual components moving longitudinally to enable the overall length from object to image to be varied. The rigid bars 51,52 to hold bearing 30 upright are not shown in figure 20.

The guide apparatus 2 may be adapted to direct an image into only one eye of a user.

Furthermore, pupil movement could be measured in ways other than described above (e.g. by electrodes near the eyes) or apparatus produced without this feature. Other characteristics of the user's eyes such as pupil diameter, aspect ratio, etc. could also be measured.

One or more of the many alternative ways of measuring head position and orientation from prior art (such as magnetic systems, electro-optical methods, ultrasonic sensors, inertial sensors) could be used instead of or in addition to the rotation sensors on the articulated image guide.

Any of the numerous methods known in the art for reducing or eliminating the weight of the headset on the user may be used, notably the use of a counterweight.

More than one image guide may be provided for each headset; for instance one from the left of the user for the left eye image, and one from the right of the user for the right eye image.

It will be appreciated that various changes and modifications may be made to the apparatus described herein without departing from the present invention. - 20

Claims

CLAIMS: 1. Articulated image guide apparatus for guiding light from an

image generator to a user of the apparatus comprising: a plurality of linking members; a plurality of joint members each connected between a pair of the linking members and permitting articulation of each linking member with respect to an adjacent linking member; input means at a first end of the image guide apparatus which can be directed at the image generator; and output means at a second end of the image guide apparatus which enables the user to view transmitted light; wherein, in use, light from an image generated by the image generator is received by the input means and then guided through the linking members and delivered at the output means to be viewed by the user, the apparatus delivering a virtual image directly to the eye(s) of the user.
2. Articulated image guide apparatus as claimed in claim l, wherein in each joint member one or more mirrors and/or prisms are used to guide light through the apparatus.
3. Articulated image guide apparatus as claimed in claim l or 2 for use with an image generator which comprises a screen by which the generated image is displayed; wherein the input means comprises a system of lenses to optically reduce in size the displayed generated image prior to onward transmission of the image through the image guide apparatus.
4. Articulated image guide apparatus as claimed in claim 3, wherein the image generator comprises a plurality of screens each of which displays a part of the complete image which is to be guided by the apparatus.
5. Articulated image guide apparatus as claimed in claim 4, wherein the input means translates the images displayed by the screens so that they are adjacent to each other prior to onward transmission through the link members and the joint members.
6. Articulated image guide apparatus as claimed in any one of claims 1 to 4, wherein at least first and second images are generated by the image generator.
7. Articulated image guide apparatus as claimed in claim 6 further comprising polarization means for polarising the first and second images in first and second directions respectively.
8. Articulated image guide apparatus as claimed in claim 7, wherein the first and second directions are orthogonal to each other and the apparatus further comprises means for combining said first and second polarised images into a single image.
9. Articulated image guide apparatus as claimed in any preceding claim, wherein the output means splits the image into two images, one image for each of the user's eyes. - 22
10. Articulated image guide apparatus as claimed in any one of the preceding claims further comprising sensor means for producing an indication of the path through which the transmitted image passes from the input means to the output means.
11. Articulated image guide apparatus as claimed in claim 10 further comprising correction means for effecting correction of the transmitted image.
12. Articulated image guide apparatus as claimed in claim 10 or 11 when dependent directly or indirectly on claim 2, wherein the sensor means comprises rotation sensors indicating rotation of a mirror or prism relative to one or more of the other mirrors or prisms.
13. Articulated image guide apparatus as claimed in claim 10, 11, or 12 wherein the sensor means comprises sensor means attached to the output means which gives an indication of the position of the input means and thereby the head of the user.
14. Articulated image guide apparatus as claimed in any one of claims 10 to 13, wherein the sensor means comprises photosensitive cells for producing signals indicative of the orientation of the transmitted image at the output means.
15. Articulated image guide apparatus as claimed in any one of claims 11 to 14 wherein the correction means comprises at least one rotatable prism or a plurality of rotatable mirrors. - 23
16. Articulated image guide apparatus as claimed in any one of claims 11 to 15 wherein the correction means comprises image display control means operable to control orientation of an image generated by the image generator.
17. Articulated image guide apparatus as claimed in any one of the preceding claims comprising additionally a tracking system for tracking movement of the user's pupil(s) comprising camera means for recording an image of the user's pupil(s) and image display control means for varying the image generated by the image generator in response to movement of the user's pupil(s).
18. Articulated image guide apparatus as claimed in claim 17 wherein the camera means is an infrared camera and the apparatus additionally comprises infrared illumination means for illuminating the user's pupil(s) .
19. Articulated image guide apparatus as claimed in claim 2 or any one of claims 3 to 18 when dependent directly or indirectly on claim 2, wherein each mirror is movable relative to the joint member in which the mirror is housed and motor means is provided to move each mirror and control means is provided to control the motor means to position each mirror so that a line normal to the mirror surface bisects an angle between the link members adjacent the joint member.
20. Articulated image guide apparatus as claimed in any preceding claim further comprising at least one telecentric relay.
21. Articulated image guide apparatus as claimed in any preceding claim further comprising a counter balance at least partially to balance the weight of the apparatus.
22. Articulated image guide apparatus as claimed in claim 21 wherein the counter-balance is a spring balance.
23. Articulated image guide apparatus as claimed in any preceding claim wherein the output means is connected to a headset to be worn by the user, the output means being connected to the headset via a IS connecting joint member which facilitates a pitching movement of the headset.
24. Articulated image guide apparatus as claimed in claim 23, wherein the joint member adjacent to the connecting joint member facilitates a rolling motion of the headset.
25. Articulated image guide apparatus as claimed in claim 24, wherein the second joint member from the connecting joint member facilitates a yawing motion of the headset.
26. Image guide apparatus for guiding light from an image generator to a user of the apparatus comprising: input means at a first end of the image guide apparatus which can be directed at the image generator; and output means at a second end of the image guide apparatus which enables the user to view transmitted - 25 light; and movable optical means defining a movable optical path between the input means and the output means; the movable optical means comprising a series of reflective elements provided at intervals along the optical path; wherein, in use, light from an image generated by the image generator is received by the input means and then guided along the movable optical path defined by the movable optical means and delivered at the output means to be viewed by the user, the apparatus delivering a virtual image directly to the eye(s) of the user.
27. Image guide apparatus as claimed in claim 26, wherein the series of reflective elements comprise mirrors and/or prisms.
28. Image guide apparatus as claimed in claim 26 or 27 further comprising means for controlling the position and orientation of each reflective element with respect to an adjacent reflective element in the series.
29. Image guide apparatus as claimed in any one of claims 26, 27 or 28 wherein the means for controlling the position and orientation of each reflective element comprises a mechanical structure to which the reflective elements are attached.
30. Image guide apparatus as claimed in claim 29 wherein the mechanical structure comprises: a plurality of linking members; a plurality of joint members each connected between a pair of the linking members and permitting articulation of each linking member with respect to an adjacent linking member.
31. A method of guiding an image through an image guide apparatus, the method comprising the steps of: (a) generating first and second images; (b) polarising said first and second images; and (c) combining the first and second polarised images into a single image.
32. A method as claimed in claim 31, wherein the first and second images in said combined image are polarised in first and second directions, said first and second directions being angularly offset relative to each other.
33. A method as claimed in claim 31, wherein the first and second images are elliptically or circularly polarised with different phase differences between the

electric and magnetic field components of the

propagated light.
34. A method as claimed in any one of claims 31, 32 or 33, wherein the first and second images are orthogonally polarised.
35. A method as claimed in any one of claims 31 to 34 further comprising the step of separating the first and second polarised images from said single image.
36. Image guide apparatus for guiding light from an image generator to a user, the apparatus comprising an input means at the first end of the image guide apparatus and an output means at the second end of the image guide apparatus; the image guide apparatus including means for polarising light from the image generator; wherein, in use, first and second images S are generated by the image generator, the first and second images being polarised by the polarization means and combined into a single image.
37. Apparatus as claimed in claim 36 further comprising means for separating said first and second polarised images from said single image.
38. Apparatus as claimed in claim 36 or 37, wherein said means for polarising light from the image generator effects linear, elliptical or circular polarization.
39. Articulated image guide apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
40. Articulated image guide apparatus substantially as hereinbefore described with reference to and as shown in Figures 1 to 10; Figures 1 to 9 and 11; Figures 1 to 9, 17, 18 and 19; or Figure 20.

545215 TOT; SMD