GB2155199A - Viewing apparatus having line of sight deviating elements - Google Patents

Abstract

To provide both a stereoscopic view and separate views, display apparatus comprising two display means e.g. cathode ray tubes (1,2) viewed through biocular magnifying lenses (3,4) has deviating prisms (6,7). When the prisms are in the respective lines of sight the display images appear superposed. At least one prism is movable into the other line of sight where it cancels the deviating effect of the other prism to permit separate viewing of the display images. The apparatus may be used in an armoured military vehicle. <IMAGE>

Description

SPECIFICATION Improvements in or relating to display apparatus This invention concerns improvements in or relating to display apparatus.

It is now generally well established that two eyed viewing of a display, such as that provided on a cathode ray tube, has significant advantages over one eyed viewing, particularly in military applications. Two eyed viewing can be provided either by a double system which gives an independent view for each eye, or by a single large system which allows a common view to both eyes.

Large sized optics generally have the advantage of permitting greater head movement and more comfortable viewing, but the common view system has the disadvantage of making it difficult to provide stereoscopic viewing. In some circumstances, and in particular in certain military applications, a high quality stereoscopic viewing capability is required, but separate non-stereoscopic views can also be useful.

According to the present invention there is provided display apparatus comprising first and second display means providing two respective displays which are viewable along respective lines of sight, and first and second light deviating elements, one for each line of sight and each arranged to deviate light from the respective display so as to locate the two display images in one desired positional relationship, at least one of the light deviating elements being movable between its position in a respective line of sight and a position in the other line of sight at which it cancels the deviating effect of the other light deviating element in that other line of sight so that the display images then appear in another desired positional relationship.Said one desired positional relationship may be a superposed relationship so that an observer can, with the light deviating elements located in the respective lines of sight, view both display images simultaneously in superposed relationship, or can, after moving one of the light deviating elements so as to locate both the light deviating elements in the same line of sight but with their deviating effects mutually cancelled, view either of the two display images separately, said other desired positional relationship being an adjacent relationship.Alternatively, said one desired positional relationship may be an adjacent relationship so that an observer can, with the light deviating elements located in the respective lines of sight, view either of the display images separately, or can, after moving one of the light deviating elements so as to locate both the light deviating elements in the same line of sight but with their deviating effects mutually cancelled, view both display images simultaneously in superposed relationship, such superposed relationship being said other desired positional relationship.

The first and second display means may be so arranged that the superposed images provide a stereoscopic picture of a scene or object under viaw so that the observer can, by suitable location of the light deviating elements, achieve a stereoscopic view when required.

The observer's independent or separate view of the first or second display means respectively can be a two eyed view provided by respective biocular optics arrangements. Thus the respective display means, which may for example by a cathode ray tube, may be viewed through a magnifier which may in particular be a biocular magnifying lens.

If the deviating elements in the respective lines of sight cause superposition of the display images, then the undeviated lines of sight (which may ef fectiveiy be defined by the magnifier axes) may be angled so as to converge in a direction towards the observer to a degree such that the respective first and second display images are located in adjacent, and preferably contiguous, relationship at the required distance from the observer's eyes. Alternatively the undeviated lines of sight may be parallel and at a spacing such that the display images are in adjacent, and preferably contiguous, relationship at the required distance from the observer's eyes, the size of the displays being such as to permit the required display image location and positional relationship.If the deviating elements in the respective lines of sight locate the two display images in adjacent, and preferably contiguous, relationship at the required distance from the observer's eyes, then the undeviated lines of sight may be angled so as to converge in a direction away from the observer to a degree such that the display images appear in superposed relationship. It will be appreciated that the display images should preferably not have any direct overlap when in adjacent relationship but a gap between them may be tolerable although contiguity is preferred.

The light deviating elements may conveniently be prisms which separately effect deviation in the respective lines of sight, but which when together in one line of sight effectively form a glass block having parallel faces through which the light is transmitted without substantial angular deviation.

One or both of the light deviating elements may be movable between the lines of sight so that the pair of elements can be put together in one or either of the lines of sight. Conveniently there may be a transparent plate extending across both lines of sight with the deviating elements lying adjacent to that plate.

Apparatus according to the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic representation of an embodiment of display apparatus, Figure 2 schematically shows part of the apparatus of Figure 1 in a different position, Figure 3 diagrammatically represents an aspect of the apparatus of Figure 1, Figure 4 diagrammatically represents an alternative arrangement of apparatus corresponding to that shown in Figure 3, Figure 5 is a schematic representation of another embodiment of display apparatus, and Figure 6 schematically shows part of the appara tus of Figure 5 in a different position.

Figure 1 schematically shows two display devices in the form of respective cathode ray tubes 1 and 2 having in front of them respective biocular magnifier lenses 3 and 4 through which an observer can view the display on the phosphor of the respective cathode ray tube. In accordance with the invention there is disposed in front of the magnifier lenses 3 and 4 a device comprising a transparent glass plate 5 which extends across the field of view of both displays and a prism arrangement comprising two complementary prisms 6 and 7 of right-angled triangular cross section.When, as shown in Figure 1, the prism 6 is located in the iight path from the cathode ray tube 1, and the prism 7 is located in the light path from the cathode ray tube 2, then these respective prisms serve to deviate or bend the light paths such that the lines of sight from the observer's respective eyes El and E2 converge to a position 8. At that position the respective displays are superimposed so that the observer is viewing both displays with both eyes. If the two respective displays are such as to provide a stereoscopic view, then the observer sees such stereoscopic view in the image at the position 8.In an armoured military vehicle the displays may represent views of the outside world and the stereoscopic effect may be achieved by providing views for display on the respective cath ode ray tubes 1 and 2 which differ in the way that each eye givers a different view for normal binocu lar vision. Such different views may be effected by the use of suitably spaced optical components, e.g.

two mirrors mounted about 70 or 80 mm apart, as sociated with respective cameras or the like con nected with the cathode ray tubes 1 and 2 to generate the displays thereon.

However, if the prism 7 is slid across into com plementary engagement with the prism 6, i.e. with their hypotenuse faces together, such that the de viating effects of the prisms are mutually cancelled and the prisms together simply form a rectangular block, then light from the cathode ray tube 1 can pass through parallel faces of that block substan tially angularly undeviated, while light from the cathode ray tube 2 also passes undeviated since there is now no prism in that light path. An ob server can therefore view either the display on the cathode ray tube 1 or the display on the cathode ray tube 2 independently and separately. Since the magnifying lenses 3 and 4 are biocular, the ob server can view the required display with both eyes in either case.

The effect of sliding across the prism 7 into en gagement with the prism 6 is further shown in Fig ure 2. It will be understood, however, that one or both of the prisms 6 and 7 may be slidable so that the combined block can be located either in the light path from the cathode ray tube 1 or in the light path from the cathode ray tube 2.

Figure 3 diagrammatically shows the basic dis play arrangement of Figure 1 and illustrates how in that arrangement the cathode ray tubes 1 and 2 and their respective magnifier lenses 3 and 4 have their axes tilted so as to diverge in a direction away from the observer. These axes effectively define the undeviated lines of sight. Viewable images 11 and 12 are thus disposed in mutually angled adjacent relationship, and are preferably in contiguous relationship such that the two images meet at the centre. However, some space between the two images may be permissible but generally it would not be very satisfactory if the two images were to overlap. The viewed images may appear as if they were, for example, about 500 mm from the observer's eyes and the magnifier axes may be, for example, about 65 mm apart at the nominal viewing position.It will be appreciated that locating the separately viewable images in adjacent, preferably contiguous, relationship can assist in giving the observer an orientation awareness, particularly when the images represent views of the outside world in, for example, an armoured military vehicle. It will be understood that the images viewed in adjacent, separately viewable mode, may be different from those viewed in superposed, stereoscopic mode, for example by appropriate control of cameras or associated optics connected with the cathode ray tubes 1 and 2 to generate the displays thereon. The adjacent image views may, in particular, be such as to provide a continuum of the viewed scene from one display to the other.

Figure 4 diagrammatically shows an alternative arrangement in which the axes of the cathode ray tubes 1 and 2 and their respective magnifier lenses 3 and 4 are parallel, the spacings between those axes being such as to provide the required adjacent positional relationship between the images 11 and 12. In this case the images 11 and 12 are coplanar, but are again preferably arranged in contiguous relationship (the cathode ray tube display size being adapted, and in particular reduced, if necessary, to achieve such relationship) although again some spacing between the images may be acceptable while overlap between the images is generally not desirable. Again, the viewed images may appear as if located, for example, about 500 mm from the eyes and the parallel magnifier axes may be spaced, for example, 65 mm apart.

In the embodiments described above with reference to Figures 1 to 4 the two display images appear in superposed relationship when the deviating prisms are located in the respective lines of sight, and are in adjacent relationship when the two prisms are in the same line of sight so that their deviating effects are mutually cancelled. It will be appreciated that this approach may be effectively reversed and the apparatus could be arranged so that the two display images appear in adjacent re lationship when the deviating prisms are located in the respective lines of sight, and are in superposed relationship when the deviating effects are cancelled by having both prisms in the same line of sight. This is schematically. shown in Figures 5 and 6.

Figure 5 shows the axes of the cathode ray tubes 1 and 2 and their respective biocular magnifiers 3 and 4, which axes effectively define the undeviated lines of sight, converging in a direction away from the observer so as to locate the display images in superposed relationship without the deviation.

However, with the deviating prisms 6 and 7 located in the respective lines of sight, the images II and 12 appear in adjacent, preferably contiguous, relationship. In this case the deviating prisms 6 and 7 serve effectively to divide or separate the two images and are oriented accordingly. When the superposed image relationship is required, one of the prisms is slid across so as to locate both in the same line of sight with their deviating effects mutually cancelled. This is illustrated in Figure 6 which shows the right angled triangular cross-section prisms 6 and 7 with their longer non-hypotenuse faces together to form a parallelogram block.

In the line of sight in which the composite block is located the light is transmitted through parallel faces of the block substantially angularly undeviated, while in the other line of sight the light passes undeviated in the absence of the prism.

It will be seen that apparatus as described above can provide a stereoscopic viewing capability, whilst also permitting individually and separate two -eyed viewing of the two displays independently. The sliding prism arrangement is relatively simple and requires no storage of out of use components. It will be appreciated that in practice a plurality of sets of apparatus as described above may be used in association, for example in a single armoured vehicle to provide an extended surveillance capability.

It will be understood that light deviating elements other than prisms could be employed, and in particular diffractive optical elements which in the respective light paths effect the deviation necessary to achieve the required effect, but which when located in the same path have their deviating effects mutually cancelled.

Claims (16)

1. Display apparatus comprising first and second display means providing two respective displays which are viewable along respective lines of sight, and first and second light deviating elements, one for each line of sight and each arranged to deviate light from the respective display so as to locate the two display images in one desired positional relationship, at least one of the light deviating elements being movable between its position in a respective line of sight and a position in the other line of sight at which it cancels the deviating effect of the other light deviating element in that other line of sight so that the display images then appear in another desired positional relationship.

2. Apparatus according to Claim 1 arranged so that said one desired positional relationship is a superposed relationship and said other desired positional relationship is an adjacent relationship.

3. Apparatus according to Claim 1 arranged so that said one desired positional relationship is an adjacent relationship and said other desired positional relationship is a superposed relationship.

4. Apparatus according to Claim 2 or Claim 3 in which the first and second display means are so arranged that the superposed images provide a stereoscopic picture.

5. Apparatus according to any preceding claim comprising respective biocular optics arrangements for providing a two eyed separate view of the first or second display means respectively.

6. Apparatus according to any preceding claim in which said display means are cathode ray tubes.

7. Apparatus according to any preceding claim in which said display means are viewed through respective magnifiers.

8. Apparatus according to Claim 7 in which the magnifiers are biocular magnifying lenses.

9. Apparatus according to Claim 2, or any of Claims 4 to 8 when dependent from Claim 2, in which the undeviated lines of sight are angled so as to converge in a direction towards the observer.

10. Apparatus according to Claim 2, or any of Claims 4 to 8 when dependent from Claim 2, in which the undeviated lines of sight are parallel.

11. Apparatus according to Claim 3, or any of Claims 4 to 8 when dependent from Claim 3, in which the undeviated lines of sight are angled so as to converge in a direction away from the observer.

12. Apparatus according to Claim 9 or Claim 10 or Claim 11 arranged so that the display images in said adjacent relationship appear in contiguous relationship.

13. Apparatus according to any preceding claim in which the light deviating elements are prisms.

14. Apparatus according to any preceding claim in which both the light deviating elements are movable between the lines of sight.

15. Apparatus according to any preceding claim comprising a transparent plate extending across both lines of sight with the deviating elements lying adjacent that transparent plate.

16. Display apparatus substantially as described herein with reference to Figures 1, 2 and 3, or Figure 4, or Figures 5 and 6 of the accompanying drawings.