CA2217639A1 - A visual display system having a large field of view - Google Patents
A visual display system having a large field of view Download PDFInfo
- Publication number
- CA2217639A1 CA2217639A1 CA 2217639 CA2217639A CA2217639A1 CA 2217639 A1 CA2217639 A1 CA 2217639A1 CA 2217639 CA2217639 CA 2217639 CA 2217639 A CA2217639 A CA 2217639A CA 2217639 A1 CA2217639 A1 CA 2217639A1
- Authority
- CA
- Canada
- Prior art keywords
- projector
- display system
- visual display
- user
- view
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B9/00—Simulators for teaching or training purposes
- G09B9/02—Simulators for teaching or training purposes for teaching control of vehicles or other craft
- G09B9/08—Simulators for teaching or training purposes for teaching control of vehicles or other craft for teaching control of aircraft, e.g. Link trainer
- G09B9/30—Simulation of view from aircraft
- G09B9/307—Simulation of view from aircraft by helmet-mounted projector or display
Landscapes
- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Business, Economics & Management (AREA)
- Physics & Mathematics (AREA)
- Educational Administration (AREA)
- Educational Technology (AREA)
- General Physics & Mathematics (AREA)
- Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
Abstract
A visual display system (2) having a large field of view, which visual display system (2) comprises at least one projector (12) which has at least one exit pupil (14) and which in use is positioned remote from a head of a user of the visual display system, optical imaging means (6) for imaging the exit pupil (14) of the projector (12) onto eye pupils of the user (4), tracking means (18) for tracking the head (10) of the user (4), and control means (20) for positioning and orientating the projector (12) such that the exit pupil (14) of the projector (12) remains imaged on the eye pupils of the user (4) as the head (10) of the user (4) moves throughout the field of view and viewing volume.
Description
A ~S~A~ DISP~Y SY-~L~ HU~I~G A
~UR&E FIE~D OF ~EW
This invention relates to a visual display system and, more especially, this invention relates to a ~isual display system having a large field of view.
T~e visual display system may be used for simulators for use in training, research, ~eisure or entertainment.
Simulators used in tr~inin~, research, leisure and entertainment are usually required to provide a highly realistic vlsual representation of the user's en~ironment. Thus, for example, a simulator used in aircraft training is required to provide a highly realistic Yisual representation of the view from an aircraf t cockpit. Irrespective of whether the simulator is used for training, research, leisure or entertainment, the required highly realistic visual representation should ideally co~er as large a field of view as the real wor}d original, with image resolution approaching that of the human eye.
The visual display system used in the simulators comprises a database of information describing the simulated wor}d, an image generator ~or converting the databa6e of information into signals suitable for ~eeding to a display, and the display itself which turns the signals into a form which can be perceived by the human eye/brain. The database is usually stored in digital form, the image generator is usually a powerful graphics computer, and the display may take one of several known forms as described below.
One known type of display is such as to surround the user with a ~creen on to which the image is projected. For field of views with a large angular subtense, both horizontally and vertically, the screen naturally takes the form of a spherical dome or partial dome. If the required ~ield of view is limited in one ~m~n~ion~ for example the restricted field of view of a ship's bridge simulator, then a truncated cone or cylinder may also be appropriate.
In order that the image on the screen is not perceived by the user to be too close, the domes tend to have a radius o~ several meters. Thus the domes are physically large and they give rise to consequent problems of facility space, transport and mass. This is especially so if the domes are placed on a movable plat~orm to simulate motion. The large surface area of the domes results in a dim image because of the limited light output o~ available projection devices, and the integrating sphere effect severely reduces image contrast. Practical limits to the radius of domes means tnat the image is still ~oo close to W O 97/29472 PCT/~B97/00322 provide correct perspective to two users ~ simultaneously over a large horizontal and vertical field of view.
T~e projectors used to illuminate the screen have a limited number of resolvable pixels. To simultaneously cover a large field of view at adequate resolution re~uires a number of such projectors.
Alternatively, at least one projector can be steerable such that its image is concentrated where it is required at a particular time. The image can follow a target in a scene, the user~s head direction, eye direction or some combination. These area of interest displays have an instantaneous field of view within a larger total field o~ view or what is called field o~
regard.
The area of interest approach addresses the problem o~ providing good image resolution over a large field of view, but does not remove the disadvantage associated with the dome screen.
Another known technique which overcomes the size problems associated with domes is the use o~
collimation. The image is projected on to a small radius screen and viewed via an optical component, usually a concave mirror, such that the ~inal image is virtual and nom~n~1ly at optical in~inity. The image distance is now considerably greater than the physical W O 97~29472 PCT/GB97/W322 extent o~ the display. The smaller screen radius also reduces screen area for a given field o~ view, giving a somewhat brighter image. The difficulty of placing the screen in an acceptable position relative to the mirror for good collimation, without it blocking the field of view, means that in practice the field of view of these displays is limited in at least one direction, that is either horizontally or vertically.
Both of the dome and the collimated techni~ues described above require a screen to hold the image.
The function c~f the screen is to scatter light into the viewing volume of the display. The viewing volume is the space around the design eye point from which a quality image is ~isible. In a flight simulator, for example, the viewing volume should be most or all o~
the cockpit, or at least that part of the cockpit which the head of the or each pilot in the cockpit can occupy. The screen surface is covered with a light-diffusing coating. An important parameter of this coating is its ~ain. A perfectly diffusing (Lambertian) coating on a dome screen would have a gain of unity and would scatter light evenly in all directiol~. It would appear equally bright from any eye point. Higher gain coatings can be used to concentrate the scattered light into the viewing volume. This increases the image brightness as seen W O 97~29472 PCT/GB97100322 from the design e~e point and improves image contrast ~as less light is scattered into unwanted directions) but tends to degrade uni~ormity of ~rightness across ehe field of view. However, it is not possible to ~ormulate or apply a coating that scatters light only into the viewing volume. Moreover, since in practice the eye point is off the illumination axis of the projector, a min;mltm scatter is required in order to get enough light into the viewing volume. Thus much light is inevitably wasted, resulting in low image brightness and contrast, for both the dome and the collimated case.
A further known technique, which o~ercomes the problem of display size and portability is to have a helmet mounted display. The helmet mounted display i8 sometimes referred to as a head mounted display. With a helmet mounted display, one or more usually both of the eyes of a user view a display device through collimating optics mounted on the helmet. The display device may be a small cathode ray tube, a liquid crystal display, or simllar. The display device may alternatively be a large projector coupled to the helmet optics by fibre optic bundles. The helmet mounted display is inherently an area of interest ~isplay. Since the field of view of the helmet mcunted display moves with the head of the user, the helmet mounted display has a very large field of regard.
It is also possible to inset a small eye-tracked or centrally ~ixed high resolution field of view within the main helmet mounted display field of view.
If images with the correct disparity are fed to each eye, then a stereoscopic display is possible.
In the absence of a large diffusing screen, image brightness and contrast are much improved. However, the lle]met becomes non-standard, bulky and heavy. The mass and inertia of the helmet are unrepresentative of the original, thereby producing unrealistic head loading. In small cockpits, the bulk of the helmet mounted display restricts the head movements of the user.
A helmet mounted display also puts severe demand on the image generator. More specifically, because the head of the user can move at such high rates and the helmet mounted display is directly coupled to the head of the user, the image is prone to instability due to image generator time lags. This is a more difficult problem than for a head tracking projector that is mounted off the head. In order not to further load the image generator by ha~ing it generate a simulated view o:E the coc3cpit interior, the helmet mounted display also has to be see-through. The image generator is still required to ~lank those parts of the image that would otherwise overlay the view of the cockpit, to avoid the appearance of a transparent cockpit. So the helmet mounted display is also prone to some spill of its image onto the cockpit during rapid head movements.
In some applications where a helmet is not worn in the real world, for example in the case of civil airline pilots, a helmet mounted display is unacceptable.
Major deficiencies of the prior art as described above may therefore be summarised as size/brightness/contrast problems for domes, limited field of view/brightness/contrast problems for collimators, and helmet~image generator problems for helmet mounted displays.
It is an aim of the present invention to provide a visual display system able to provide an image with high brightness and contrast over a large field of view. The present invention also aims to provide the image without display hardware on the head of the user.
Accordingly, in one non-limiting embodiment of the present invention, there is provided a visual display system having a large field of view, which visual display system comprises at least one projector which has at least one exit pupil and which in use is posi~ioned remote from a head of a user of the visual display system, optical imaging means for imaging the exit pupil of the projector onto eye pupils of the user, tracking means for tracking the head of the user, and control means for positioning~ ~nd orientating the projector such that the exit pupil of ~he projector remains imaged onto the eye pupils of the ~Iser as the head o~ the user moves throughout the field of view and viewing ~olume.
The visual display system of the present invention may be one in which the optical imaging means is a concave mirror. Other optical imaging systems may be employed.
There may be two pupils per user providing a binocular display. If it is desired that the binocular display is stereoscopic, then each pupil should contain an image with correct disparity.
The image of the pupil o~ the projector may be large enough to cover both eyes of the user.
The field of vision may have at least one high resolution inset.
The visual display system may comprisè a first projector or projectors for a first user of the visual display system, a second projector or projectors for a second user of the visual display system, and a common -W O 97/29472 PCT/GB97/~0322 mirror which is shared by the first projector or projectors and the second projector or projectors.
The visual display system may include optical replication means for enlarging the pupil of the projector.
The projector may be a multi-channel pupil projector or a pupil-switching projector.
The visual display system may include corrector means in f ront of the projector or the optical imaging means.
The visual display system may be apparatus which is such that the image is of moving or static scenes.
Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:
Figure 1 shows a visual display system having a large field of view, and for use by a single users;
Figure 2 shows a visual display system having a large field of view, and for use by two users;
Figures 3 and 4 are plan and side views of a visual display system utilising a multi-channel pupil projector;
Figure 5 shows a visual display system utilising a pupil-switching proje,ctor;
Figure 6 shows a visual display system with corrector means in front of a mirror, and Figure 7 shows a visual display system with corrector means in front of a projector.
Referring to Figure 1, there is shown a visual display system 2 having a large field of view and for use ~y a single user 4. The user 4 may be, for example, a trainee pilot.
The visual display system 2 comprises a large concave mirror 6 p~sitioned in fron~ of the user 4 such that the centre of curvature 8 of the mirror 6 is somewhat above the head 10 of the user 4. The angular subtense of the mirror 6 at the eye of the user 4 is substantially equal to the total field of view of the display. A movable projector 12 having two exit pupils 14 i.s positioned with i.ts exit pupils 14 somewhat above the centre of curvature 8 of the mirror 6. Relay optics 16 are employed as shown.
The mirror 6 has the inherent property that an object near the centre of curvature 8 of the mirror 6 i~ imaged by the mirror 6 at unit magnification to a su~stantially symmetrical position on the other side of the centre of curvature ~. If the object is the ex~t pupil 14 of the projector 12, and the eye of the user 4 is placed at the image of the exit pupil 14, then a bright view of the projected display will be seen. Thus, as will be appreciated from Figure 1, the two exit pupils 14 of the projector 12 are imaged ~y ~ the mirror 6 onto the eyes of the user 4.
Tracking means in the form of a head position sensor la is provided to measure the position and orientation of the head 10 of the user 4. The tracking means may be a known tracking means using, for example, either magnetic fields, ultrasonics or video cameras. The head 10 wears a helmet 22. As the head 10 o~ the user 4 mo~es, either in translation, or in rotation to look around the total ~ield o~ view, signals from the head position sensor 18 are fed to control means in the form of a servo system 20. The servo system moves the exit pupils 14 of the projector 12 such that the exit pupils 14 remain imaged on to the eyes of the user 4. The effect is of looking into the optics of the projector 12 so the image is very bright. For example, a cathode ray tube projector capable of producing a brightness of a few ftL on a dome screen will have a phosphor brightness of more than 10,000 ftL. When looking into the projector 12, the user sees the phosphor directly, minus any transmission losses in the pro~ection optics. Making reasonable estimates o~ transmission loss (50~) and ~irror reflection loss (10%) disp~ayed brightness s~ould be greater than 4000 ftL.
W O 97/29472 . PCT/GB97/00322 The above described principle of operation works with any sultable and appropriate kind of projector 12, for example a cathode ray tube projector 12, a liquid crystal display projector 12, or a light valve projector 12. The principle does not depend on a particular source or illumination arrangement in the pro~ector 12. In addition, because the projected light is imaged onto the pupils of the user 4, very little light is wasted in unwanted directions and so image contrast is also high. Since the user 4 has no helmet mounted display optics, the user 4 has a clear view of his or her environment, ~or example a cockpit.
If the projector 12 is focused onto the focal surface of the mirror 6, then the image seen by the user 4 will be collimated.
The display is inherently of the area of interest type. Previously developed area of interest display techni~ues can be applied. Thus, for example, the projector 12 may have a high resolution area inset within the main instantaneous head tracked field of view. Alterna~ively, the main field of view may have variable acuity, the resolution falling off away from the centre in a way that mimics eye resolution fall o~
Referring now to Figure 2, there is shown a visual display system 24 which is for use by two users 4 having heads 10. The heads 10 of the users 4 are symmetrically disposed,about the centre of curvature 8 with their respective projectors 12. For clarity of illustration, the mirror 6 has been omitted.
The users 4 share a common mirror 6 and the principle of operation of the visual display system 16 is the same as described above for the visual display system 2 shown in Figure 1. The significant difference is that in Figure 2, the heads 10 of the users 4 and the projectors 12 must be displaced both horizontally and vertically around the centre of curvature 8.
In a third embodiment of tne invention (no~
shown), the two exit pupils 14 of the projector 12 may contain images with the correct relative disparity.
In this case, a stereoscopic display results.
A further embodiment of the invention is shown in Fiqures 3 and 4 in which the pro~ector is a multi-ch~nn~l pupil projector. The projector's field-of-view is covered by a number of channels of projection optics 26, each with its own pupil 28. The exit pupils 28 are optically overlapped by, for example, an arrangement of ~lat mirrors 30, to form an apparent composite pupil 32. The smalier fiel~-cf-view per pro3ector allows the overall field-of-view to be increased, or alternatively the projection optics to CA 022l7639 l997-l0-06 W O 97/~9472 PCT/GB97/00322 be simpler, or the exit pupil to be larger. The latter is particularly use~ul for a biocular display, where the exit pupil must be large for its image to cover both eyes of the user simultaneously.
Multiple channels also provide an alternative to a high-resolution inset as a way to increase the resolution of the display.
A further embodiment of the invention is shown in Figure 5 in which the projector is a pupil-swltching projector. In a display with a large field of view and separate projectors ~or each eye, the exit pupils may get in the way of each other, that is the optics for one pupil may block some of the light emitted by the other, This clash may be avoided by a single projector with a single exit pupil 34, the pupil being sequentially ~witched between the locations required for the le~t and right eyes. Pupil switching optics 36 are employed and the switching would take place too fast to be visible to the human eye.
A further embodiment o~ the invention is shown in Figure 6 in which corrector means in front o~ a main ~irror 40 are employed. Aberrations of the main mirror 40, which may limit the field of view or require large exit pupils, may be corrected to some extent by an additional optical element 42 in front of the mirror 40. This may be a thin concave element with a lenticular structure 44 on its surface to re-direct rays 4~ from the exit pupil 48 that would otherwise miss the eye 50, after reflecting~off the mirror 40.
A further embodiment of the invention is shown in Figure 7 in which corrector means in front of a proiectQr 52 are employed. Aberrations of a main mirror 54, which may limit the field of vi~w or require large exit pupils, may be corrected to some extent by an additiorlal optical element 56 in front of the projector 52. This may be, for example, a thin cylindrical optical element.
It is tO be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been gi~en by way of example only and that modifications may be effected.
Thus, ~or example, ~he embodiments of the invention described above with reference to Figures 1 and 2 are binocular insofar as they have provided a separate exit pupil and image ~or each eye. If the exit pupil 14 of the pro3ec~or 1~ is made large enough such that its image encompasses both eyes of the user 4, then a ~inocular display results. If desired, in order to reduce the load on projector servos, only the latter stages of the projection optics need to be fully mobile, allowing the bulk of the or each projector 12 CA 022l7639 l997-l0-06 W 097/29472 PCTIG~97/00322 16 to be stationary or of a restric~ed movement. The apparatus of the invention may be such that the optical imaging means images the exit pupil o~ the projector onto the eye pupils o~ two or more users.
If desired, the visual display system of the inventioll may utilise a high gain screen. A mirror with a certain amount of surface scatter can be thought of as a very high gain screen. Thus the invention may use a high gain screen in place of a mirror. The scatter at the screen surface e~fectively enlarges the projector exit pupil, increasing the viewing volume of the display. I~ the projector is focussed on the e~uivalent location to the mirror's focal sur~ace, the scatter also blurs the image. This blurring is removed i~ the projector is re-focussed onto the screen surface. The visual display system no longer simply images the exit pupil or pupils onto the viewer as ~or the pure reflective case, but the high brightness and contrast advantages o~ the display are retained. The projector still tracks the viewer's head as it moves, maintaining the high brightness which is lost in conventional displays with high gain screens as soon as the viewer moves away ~rom the design eyepoint. By correcting the picture geometry as the head moves, it is also possible to retain the same parallax as in a collimated display. The visual CA 022l7639 l997-l0-06 display system would look like the visual display system shown in Figure 1 except ~or the mirror 6.
-
~UR&E FIE~D OF ~EW
This invention relates to a visual display system and, more especially, this invention relates to a ~isual display system having a large field of view.
T~e visual display system may be used for simulators for use in training, research, ~eisure or entertainment.
Simulators used in tr~inin~, research, leisure and entertainment are usually required to provide a highly realistic vlsual representation of the user's en~ironment. Thus, for example, a simulator used in aircraft training is required to provide a highly realistic Yisual representation of the view from an aircraf t cockpit. Irrespective of whether the simulator is used for training, research, leisure or entertainment, the required highly realistic visual representation should ideally co~er as large a field of view as the real wor}d original, with image resolution approaching that of the human eye.
The visual display system used in the simulators comprises a database of information describing the simulated wor}d, an image generator ~or converting the databa6e of information into signals suitable for ~eeding to a display, and the display itself which turns the signals into a form which can be perceived by the human eye/brain. The database is usually stored in digital form, the image generator is usually a powerful graphics computer, and the display may take one of several known forms as described below.
One known type of display is such as to surround the user with a ~creen on to which the image is projected. For field of views with a large angular subtense, both horizontally and vertically, the screen naturally takes the form of a spherical dome or partial dome. If the required ~ield of view is limited in one ~m~n~ion~ for example the restricted field of view of a ship's bridge simulator, then a truncated cone or cylinder may also be appropriate.
In order that the image on the screen is not perceived by the user to be too close, the domes tend to have a radius o~ several meters. Thus the domes are physically large and they give rise to consequent problems of facility space, transport and mass. This is especially so if the domes are placed on a movable plat~orm to simulate motion. The large surface area of the domes results in a dim image because of the limited light output o~ available projection devices, and the integrating sphere effect severely reduces image contrast. Practical limits to the radius of domes means tnat the image is still ~oo close to W O 97/29472 PCT/~B97/00322 provide correct perspective to two users ~ simultaneously over a large horizontal and vertical field of view.
T~e projectors used to illuminate the screen have a limited number of resolvable pixels. To simultaneously cover a large field of view at adequate resolution re~uires a number of such projectors.
Alternatively, at least one projector can be steerable such that its image is concentrated where it is required at a particular time. The image can follow a target in a scene, the user~s head direction, eye direction or some combination. These area of interest displays have an instantaneous field of view within a larger total field o~ view or what is called field o~
regard.
The area of interest approach addresses the problem o~ providing good image resolution over a large field of view, but does not remove the disadvantage associated with the dome screen.
Another known technique which overcomes the size problems associated with domes is the use o~
collimation. The image is projected on to a small radius screen and viewed via an optical component, usually a concave mirror, such that the ~inal image is virtual and nom~n~1ly at optical in~inity. The image distance is now considerably greater than the physical W O 97~29472 PCT/GB97/W322 extent o~ the display. The smaller screen radius also reduces screen area for a given field o~ view, giving a somewhat brighter image. The difficulty of placing the screen in an acceptable position relative to the mirror for good collimation, without it blocking the field of view, means that in practice the field of view of these displays is limited in at least one direction, that is either horizontally or vertically.
Both of the dome and the collimated techni~ues described above require a screen to hold the image.
The function c~f the screen is to scatter light into the viewing volume of the display. The viewing volume is the space around the design eye point from which a quality image is ~isible. In a flight simulator, for example, the viewing volume should be most or all o~
the cockpit, or at least that part of the cockpit which the head of the or each pilot in the cockpit can occupy. The screen surface is covered with a light-diffusing coating. An important parameter of this coating is its ~ain. A perfectly diffusing (Lambertian) coating on a dome screen would have a gain of unity and would scatter light evenly in all directiol~. It would appear equally bright from any eye point. Higher gain coatings can be used to concentrate the scattered light into the viewing volume. This increases the image brightness as seen W O 97~29472 PCT/GB97100322 from the design e~e point and improves image contrast ~as less light is scattered into unwanted directions) but tends to degrade uni~ormity of ~rightness across ehe field of view. However, it is not possible to ~ormulate or apply a coating that scatters light only into the viewing volume. Moreover, since in practice the eye point is off the illumination axis of the projector, a min;mltm scatter is required in order to get enough light into the viewing volume. Thus much light is inevitably wasted, resulting in low image brightness and contrast, for both the dome and the collimated case.
A further known technique, which o~ercomes the problem of display size and portability is to have a helmet mounted display. The helmet mounted display i8 sometimes referred to as a head mounted display. With a helmet mounted display, one or more usually both of the eyes of a user view a display device through collimating optics mounted on the helmet. The display device may be a small cathode ray tube, a liquid crystal display, or simllar. The display device may alternatively be a large projector coupled to the helmet optics by fibre optic bundles. The helmet mounted display is inherently an area of interest ~isplay. Since the field of view of the helmet mcunted display moves with the head of the user, the helmet mounted display has a very large field of regard.
It is also possible to inset a small eye-tracked or centrally ~ixed high resolution field of view within the main helmet mounted display field of view.
If images with the correct disparity are fed to each eye, then a stereoscopic display is possible.
In the absence of a large diffusing screen, image brightness and contrast are much improved. However, the lle]met becomes non-standard, bulky and heavy. The mass and inertia of the helmet are unrepresentative of the original, thereby producing unrealistic head loading. In small cockpits, the bulk of the helmet mounted display restricts the head movements of the user.
A helmet mounted display also puts severe demand on the image generator. More specifically, because the head of the user can move at such high rates and the helmet mounted display is directly coupled to the head of the user, the image is prone to instability due to image generator time lags. This is a more difficult problem than for a head tracking projector that is mounted off the head. In order not to further load the image generator by ha~ing it generate a simulated view o:E the coc3cpit interior, the helmet mounted display also has to be see-through. The image generator is still required to ~lank those parts of the image that would otherwise overlay the view of the cockpit, to avoid the appearance of a transparent cockpit. So the helmet mounted display is also prone to some spill of its image onto the cockpit during rapid head movements.
In some applications where a helmet is not worn in the real world, for example in the case of civil airline pilots, a helmet mounted display is unacceptable.
Major deficiencies of the prior art as described above may therefore be summarised as size/brightness/contrast problems for domes, limited field of view/brightness/contrast problems for collimators, and helmet~image generator problems for helmet mounted displays.
It is an aim of the present invention to provide a visual display system able to provide an image with high brightness and contrast over a large field of view. The present invention also aims to provide the image without display hardware on the head of the user.
Accordingly, in one non-limiting embodiment of the present invention, there is provided a visual display system having a large field of view, which visual display system comprises at least one projector which has at least one exit pupil and which in use is posi~ioned remote from a head of a user of the visual display system, optical imaging means for imaging the exit pupil of the projector onto eye pupils of the user, tracking means for tracking the head of the user, and control means for positioning~ ~nd orientating the projector such that the exit pupil of ~he projector remains imaged onto the eye pupils of the ~Iser as the head o~ the user moves throughout the field of view and viewing ~olume.
The visual display system of the present invention may be one in which the optical imaging means is a concave mirror. Other optical imaging systems may be employed.
There may be two pupils per user providing a binocular display. If it is desired that the binocular display is stereoscopic, then each pupil should contain an image with correct disparity.
The image of the pupil o~ the projector may be large enough to cover both eyes of the user.
The field of vision may have at least one high resolution inset.
The visual display system may comprisè a first projector or projectors for a first user of the visual display system, a second projector or projectors for a second user of the visual display system, and a common -W O 97/29472 PCT/GB97/~0322 mirror which is shared by the first projector or projectors and the second projector or projectors.
The visual display system may include optical replication means for enlarging the pupil of the projector.
The projector may be a multi-channel pupil projector or a pupil-switching projector.
The visual display system may include corrector means in f ront of the projector or the optical imaging means.
The visual display system may be apparatus which is such that the image is of moving or static scenes.
Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:
Figure 1 shows a visual display system having a large field of view, and for use by a single users;
Figure 2 shows a visual display system having a large field of view, and for use by two users;
Figures 3 and 4 are plan and side views of a visual display system utilising a multi-channel pupil projector;
Figure 5 shows a visual display system utilising a pupil-switching proje,ctor;
Figure 6 shows a visual display system with corrector means in front of a mirror, and Figure 7 shows a visual display system with corrector means in front of a projector.
Referring to Figure 1, there is shown a visual display system 2 having a large field of view and for use ~y a single user 4. The user 4 may be, for example, a trainee pilot.
The visual display system 2 comprises a large concave mirror 6 p~sitioned in fron~ of the user 4 such that the centre of curvature 8 of the mirror 6 is somewhat above the head 10 of the user 4. The angular subtense of the mirror 6 at the eye of the user 4 is substantially equal to the total field of view of the display. A movable projector 12 having two exit pupils 14 i.s positioned with i.ts exit pupils 14 somewhat above the centre of curvature 8 of the mirror 6. Relay optics 16 are employed as shown.
The mirror 6 has the inherent property that an object near the centre of curvature 8 of the mirror 6 i~ imaged by the mirror 6 at unit magnification to a su~stantially symmetrical position on the other side of the centre of curvature ~. If the object is the ex~t pupil 14 of the projector 12, and the eye of the user 4 is placed at the image of the exit pupil 14, then a bright view of the projected display will be seen. Thus, as will be appreciated from Figure 1, the two exit pupils 14 of the projector 12 are imaged ~y ~ the mirror 6 onto the eyes of the user 4.
Tracking means in the form of a head position sensor la is provided to measure the position and orientation of the head 10 of the user 4. The tracking means may be a known tracking means using, for example, either magnetic fields, ultrasonics or video cameras. The head 10 wears a helmet 22. As the head 10 o~ the user 4 mo~es, either in translation, or in rotation to look around the total ~ield o~ view, signals from the head position sensor 18 are fed to control means in the form of a servo system 20. The servo system moves the exit pupils 14 of the projector 12 such that the exit pupils 14 remain imaged on to the eyes of the user 4. The effect is of looking into the optics of the projector 12 so the image is very bright. For example, a cathode ray tube projector capable of producing a brightness of a few ftL on a dome screen will have a phosphor brightness of more than 10,000 ftL. When looking into the projector 12, the user sees the phosphor directly, minus any transmission losses in the pro~ection optics. Making reasonable estimates o~ transmission loss (50~) and ~irror reflection loss (10%) disp~ayed brightness s~ould be greater than 4000 ftL.
W O 97/29472 . PCT/GB97/00322 The above described principle of operation works with any sultable and appropriate kind of projector 12, for example a cathode ray tube projector 12, a liquid crystal display projector 12, or a light valve projector 12. The principle does not depend on a particular source or illumination arrangement in the pro~ector 12. In addition, because the projected light is imaged onto the pupils of the user 4, very little light is wasted in unwanted directions and so image contrast is also high. Since the user 4 has no helmet mounted display optics, the user 4 has a clear view of his or her environment, ~or example a cockpit.
If the projector 12 is focused onto the focal surface of the mirror 6, then the image seen by the user 4 will be collimated.
The display is inherently of the area of interest type. Previously developed area of interest display techni~ues can be applied. Thus, for example, the projector 12 may have a high resolution area inset within the main instantaneous head tracked field of view. Alterna~ively, the main field of view may have variable acuity, the resolution falling off away from the centre in a way that mimics eye resolution fall o~
Referring now to Figure 2, there is shown a visual display system 24 which is for use by two users 4 having heads 10. The heads 10 of the users 4 are symmetrically disposed,about the centre of curvature 8 with their respective projectors 12. For clarity of illustration, the mirror 6 has been omitted.
The users 4 share a common mirror 6 and the principle of operation of the visual display system 16 is the same as described above for the visual display system 2 shown in Figure 1. The significant difference is that in Figure 2, the heads 10 of the users 4 and the projectors 12 must be displaced both horizontally and vertically around the centre of curvature 8.
In a third embodiment of tne invention (no~
shown), the two exit pupils 14 of the projector 12 may contain images with the correct relative disparity.
In this case, a stereoscopic display results.
A further embodiment of the invention is shown in Fiqures 3 and 4 in which the pro~ector is a multi-ch~nn~l pupil projector. The projector's field-of-view is covered by a number of channels of projection optics 26, each with its own pupil 28. The exit pupils 28 are optically overlapped by, for example, an arrangement of ~lat mirrors 30, to form an apparent composite pupil 32. The smalier fiel~-cf-view per pro3ector allows the overall field-of-view to be increased, or alternatively the projection optics to CA 022l7639 l997-l0-06 W O 97/~9472 PCT/GB97/00322 be simpler, or the exit pupil to be larger. The latter is particularly use~ul for a biocular display, where the exit pupil must be large for its image to cover both eyes of the user simultaneously.
Multiple channels also provide an alternative to a high-resolution inset as a way to increase the resolution of the display.
A further embodiment of the invention is shown in Figure 5 in which the projector is a pupil-swltching projector. In a display with a large field of view and separate projectors ~or each eye, the exit pupils may get in the way of each other, that is the optics for one pupil may block some of the light emitted by the other, This clash may be avoided by a single projector with a single exit pupil 34, the pupil being sequentially ~witched between the locations required for the le~t and right eyes. Pupil switching optics 36 are employed and the switching would take place too fast to be visible to the human eye.
A further embodiment o~ the invention is shown in Figure 6 in which corrector means in front o~ a main ~irror 40 are employed. Aberrations of the main mirror 40, which may limit the field of view or require large exit pupils, may be corrected to some extent by an additional optical element 42 in front of the mirror 40. This may be a thin concave element with a lenticular structure 44 on its surface to re-direct rays 4~ from the exit pupil 48 that would otherwise miss the eye 50, after reflecting~off the mirror 40.
A further embodiment of the invention is shown in Figure 7 in which corrector means in front of a proiectQr 52 are employed. Aberrations of a main mirror 54, which may limit the field of vi~w or require large exit pupils, may be corrected to some extent by an additiorlal optical element 56 in front of the projector 52. This may be, for example, a thin cylindrical optical element.
It is tO be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been gi~en by way of example only and that modifications may be effected.
Thus, ~or example, ~he embodiments of the invention described above with reference to Figures 1 and 2 are binocular insofar as they have provided a separate exit pupil and image ~or each eye. If the exit pupil 14 of the pro3ec~or 1~ is made large enough such that its image encompasses both eyes of the user 4, then a ~inocular display results. If desired, in order to reduce the load on projector servos, only the latter stages of the projection optics need to be fully mobile, allowing the bulk of the or each projector 12 CA 022l7639 l997-l0-06 W 097/29472 PCTIG~97/00322 16 to be stationary or of a restric~ed movement. The apparatus of the invention may be such that the optical imaging means images the exit pupil o~ the projector onto the eye pupils o~ two or more users.
If desired, the visual display system of the inventioll may utilise a high gain screen. A mirror with a certain amount of surface scatter can be thought of as a very high gain screen. Thus the invention may use a high gain screen in place of a mirror. The scatter at the screen surface e~fectively enlarges the projector exit pupil, increasing the viewing volume of the display. I~ the projector is focussed on the e~uivalent location to the mirror's focal sur~ace, the scatter also blurs the image. This blurring is removed i~ the projector is re-focussed onto the screen surface. The visual display system no longer simply images the exit pupil or pupils onto the viewer as ~or the pure reflective case, but the high brightness and contrast advantages o~ the display are retained. The projector still tracks the viewer's head as it moves, maintaining the high brightness which is lost in conventional displays with high gain screens as soon as the viewer moves away ~rom the design eyepoint. By correcting the picture geometry as the head moves, it is also possible to retain the same parallax as in a collimated display. The visual CA 022l7639 l997-l0-06 display system would look like the visual display system shown in Figure 1 except ~or the mirror 6.
-
Claims (10)
1. A visual display system having a large field of view, which visual display system comprises at least one projector which has at least one exit pupil and which in use is positioned remote from a head of a user of the visual display system, optical imaging means for imaging the exit pupil of the projector onto eye pupils of the user, tracking means for tracking the head of the user, and control means for positioning and orientating the projector such that the exit pupil of the projector remains imaged on the eye pupils of the user as the head of the user moves throughout the field of view and viewing volume.
2. A visual display system according to claim 1 in which the optical imaging means is a concave mirror.
3. A visual display system according to claim 1 or claim 2 in which there are two pupils per user for providing a binocular display.
4. A visual display system according to any one of the preceding claims in which the image of the pupil of the projector is large enough to cover both eyes of the user.
5. A visual display system according to any one of the preceding claims in which the field of view has at least one high resolution inset.
6. A visual display system according to any one of the preceding claims and comprising a first projector or projectors for a first user of the visual display system, a second projector or projectors for a second user of the visual display system, and a common mirror which is shared by the first projector or projectors and the second projector or projectors.
7. A visual display system according to any one of the preceding claims and including optical replication means for enlarging the pupil of the projector.
8. A visual display system according to any one of the preceding claims in which the projector is a multi-channel pupil projector.
9. A visual display system according to any one of claims 1-7 in which the projector is a pupil-switching projector.
10. A visual display system according to any one of the preceding claims and including corrector means in front of the projector or the optical imaging means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9602401.3 | 1996-02-07 | ||
| GBGB9602401.3A GB9602401D0 (en) | 1996-02-07 | 1996-02-07 | A visual display system a large field of view |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2217639A1 true CA2217639A1 (en) | 1997-08-14 |
Family
ID=10788217
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2217639 Abandoned CA2217639A1 (en) | 1996-02-07 | 1997-02-05 | A visual display system having a large field of view |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0819297A1 (en) |
| AU (1) | AU1611397A (en) |
| CA (1) | CA2217639A1 (en) |
| GB (2) | GB9602401D0 (en) |
| WO (1) | WO1997029472A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8033830B2 (en) * | 2005-05-30 | 2011-10-11 | Honda Motor Co., Ltd. | Vehicle simulation system |
| US8403502B2 (en) | 2008-11-18 | 2013-03-26 | Barco N.V. | Collimated visual display with elliptical front projection screen |
| US9189885B2 (en) | 2009-09-16 | 2015-11-17 | Knorr-Bremse Systeme Fur Schienenfahrzeuge Gmbh | Visual presentation system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4303394A (en) * | 1980-07-10 | 1981-12-01 | The United States Of America As Represented By The Secretary Of The Navy | Computer generated image simulator |
| GB2101948B (en) * | 1981-07-16 | 1984-09-26 | Rediffusion Simulation Ltd | Air combat simulator |
| US5071209A (en) * | 1990-05-07 | 1991-12-10 | Hughes Aircraft Company | Variable acuity non-linear projection system |
| FR2680017B1 (en) * | 1991-07-30 | 1994-08-26 | Thomson Csf | VISUAL WITH AREA OF INTEREST, ESPECIALLY FOR A SIMULATOR. |
-
1996
- 1996-02-07 GB GBGB9602401.3A patent/GB9602401D0/en active Pending
-
1997
- 1997-02-05 WO PCT/GB1997/000322 patent/WO1997029472A1/en not_active Application Discontinuation
- 1997-02-05 GB GB9720335A patent/GB2314722B/en not_active Expired - Fee Related
- 1997-02-05 CA CA 2217639 patent/CA2217639A1/en not_active Abandoned
- 1997-02-05 AU AU16113/97A patent/AU1611397A/en not_active Abandoned
- 1997-02-05 EP EP97902475A patent/EP0819297A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB9720335D0 (en) | 1997-11-26 |
| GB9602401D0 (en) | 1996-04-03 |
| WO1997029472A1 (en) | 1997-08-14 |
| AU1611397A (en) | 1997-08-28 |
| GB2314722A (en) | 1998-01-07 |
| EP0819297A1 (en) | 1998-01-21 |
| GB2314722B (en) | 2000-08-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4634384A (en) | Head and/or eye tracked optically blended display system | |
| US5582518A (en) | System for restoring the visual environment of a pilot in a simulator | |
| US6814578B2 (en) | Visual display system and method for displaying images utilizing a holographic collimator | |
| US4048653A (en) | Visual display apparatus | |
| US6222675B1 (en) | Area of interest head-mounted display using low resolution, wide angle; high resolution, narrow angle; and see-through views | |
| US4347508A (en) | Visual display apparatus | |
| US5320534A (en) | Helmet mounted area of interest (HMAoI) for the display for advanced research and training (DART) | |
| US5572229A (en) | Head-mounted projection display system featuring beam splitter and method of making same | |
| US6078427A (en) | Smooth transition device for area of interest head-mounted display | |
| US5137450A (en) | Display for advanced research and training (DART) for use in a flight simulator and the like | |
| US4348185A (en) | Wide angle infinity display system | |
| US5348477A (en) | High definition television head mounted display unit | |
| US6890077B2 (en) | Method and apparatus for high resolution video image display | |
| US4347507A (en) | Visual display apparatus | |
| US4322726A (en) | Apparatus for providing a simulated view to hand held binoculars | |
| US5253116A (en) | Collimated viewing device with off-axis spherical mirror for simulator | |
| JPH03110593A (en) | Display device carried on head of observer for flight simulator | |
| US3880509A (en) | Wide-angle on-axis projection system | |
| CA2402226A1 (en) | Vehicle simulator having head-up display | |
| US4348187A (en) | Aerial image visual display | |
| US4340274A (en) | Visual display apparatus | |
| US3895861A (en) | Rear-screen wide-angle on-axis projection system | |
| US4205224A (en) | Binocular viewing technique | |
| Schwartz | Head tracking stereoscopic display | |
| US4167311A (en) | Projection system and process |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |