CA1319282C - Holographic optical element for instrument panel displays - Google Patents

Abstract

HOLOGRAPHIC OPTICAL ELEMENT FOR INSTRUMENT PANEL DISPLAYS

ABSTRACT OF THE DISCLOSURE

A holographic optical system includes a hologram which is located at an instrument panel co as to reflect or transmit an image from a source located off the panel.
The image is redirected only to an area at which the viewer may observe the image and is not directed to other areas so as to prevent unwanted reflections and glare such as where the instrument panel is within an aircraft cockpit.

Description

`--13~9282 HOLOGRAPHIC OPTICAL ELEMENT FOR INSTRUMENT PANEL DISPLAYS

~ACKGROUND OF THE INVENTION

This invention relates to a display system. In a situation such as in an aircraft, where space i~ limited, there is a restriction on the number of instruments and displays that will fit in a ~iven amount of panel space.
For example, it would be desirable to locate an artificial horizon display near other navigatjonal and control displays in fighter aircraft at the top of the instrument pane].. However, in most modern fighters, the artificial horizon is placed near the bottom of the instrument panel, ~' 13~28~

and the pilot, with his oxygen mask on, must alter his direction of gaze by more than 30 to check the instrument. Problems of size and space restrictions for instruments are heiqhtened by the need for redundancy of critical instruments. Due to the tight space restrictions, the panel layouts are not easily modified when an aircraft is reconfigured.
Conventional cockpit displays are typically of two types -- electro-mechanical and cathode ray tube (CRT) --although liquid crystal displays, light emitting diode displays, and electroluminescent displays are also used.
Beyond the space restrictions, other problems of conventional instrument displays include the production of canopy qlare from instrument lightinq which is distracting to the pilot. Conventional electro-mechanical multi-instrument panels are complex and the servicing of such panels is time-consuming and expensive. Electro-mechanical instruments provide a limited symbology, i.e.
they are limited to alphanumeric characters or mechanica]
analoq dials and read-outs.
To increase the amount of information displayed on the instrument panel without increasing the space requirements of the instruments, it may be desirable to selectively project an imaqe, such as an imaqe of an artificial horizon, onto a portion of the instrument panel which is occupied by existing switches, key pads, controls, and otller non-display components. However, such light projection can he impractical because of the power required to compete with direct sunlight, and since normal reflection would introduce liqht into the cockpit area as unwanted reflections and glare, inc~uding reflections off of the cockpit canopy, a particularly siqnificant problem during night-time flying.

_3_ 13~282 SUMMARY OF T~E INVENTION

The presen~ invention provides a holographic optical system for use with an instrument panel, th~ holographic optical system comp~ising:
(a) a hologram positioned so as to redirect an image generated at a place other than the instrument panel, the hologram being formed to act in the manner of a diffuser and such that the viewing window of the redirected image is controlled so as to prevent light ~rom the hologram from shining towards regions other than a region to be occupied by the viewer's head; and (b) means for producing an image at a position away from the instrument panel and for projecting and focusing the image onto the hologram.
Preferably the image source is a cathode ray tube (CRT) and the hologram is preferably superimposed with and positioned on or adjacent an existing instrument of the instrument panel. Thus, the pilot sees the additional information as beinq overlaid on the existinq instruments, controls and panel. The reflected symbols are desiqned to be sufficiently distinct from those alrea~y in use on the panel that they would not be confused with each other. In addition, the medium of the ~isplay is located in such a way as not to interfere with the normal operation of the instruments or controls over which it is superimposed.
The display screen can be in the form of a medium which can be applied over existing controls or instruments on an instrument panel, and cut out, if necessary, so as to permit knohs or touch keys to protrude through the screen. The superior surfaces of the knobs or keys can he covered in the same medium, so as to substantially fill the area over which it has been applied. The medium is optically c]ear, so AS not to interfere with the viewing of the controls or instruments over which it has been a pp lied.
The display screen medium behaves as a reflector or transmitter of hiqh efficiency for a specific, narrow halldwidth of liqht and may be optically clear to all other visible liqht. The diffuse reflecting or transmittinq properties of the medium are optimi`zed such that an ohserver at a specific distance from the medium is able to see the display imaqe only if his eyes are within a predetermined area. This property of the display prevents 131~82 its luminence from being directly radiated into areas where it i8 not desired. The medium is referred to herein as the projection or display screen.
Further objects, featl~res, and advantaqes of the invention will be apparent from the followinq detailed description when taken in conjunction with the accompanying drawinqs.

~RIEF DESCRIPTIO~ OF THE bRAWINGS

In the drawings:
Fig. 1 is an exemplary layout of the display system of the invention, where the display information is reflected off of the projection screen.
Piq. 2 is a layout showing detail of a projector in accordance~ w;th the present inyention.
Fig. 3 (on the sheet containing Fig. 1) is a perspective view of a projection screen in accordance with the invention mounted over a section of an instrument panel.
Fig. ~ illustrates the qeometry required to construct the transmission master ho]ogram.
Fig. 5 illustrates the qeometry required to construct the reflection copy hologram which comprises the projection screen.
Fig. 6 is an exempJary layout of the display system of the invention where the display information is transmitted through the projection screen, and where the recording geometry for projection and the viewing axes are not coaxial.
Fiq. 7 is an exemplary layout of the display system of the invention where the display ~information is transmitted by three independent projectors of different colors, each of the projectors transmitting different information.

131~82 Fig. 8 is an exemplary layout of the display system of the invention where the display information is transmitted by two projectors of identical colors, each of the projectors transmitting the same information to provide redundancy.
Fiq. 9 illustrates an exemplary geometry which may be used in the present invention to create a stereoscopic image.
Fig. 10 illustrates the geometry required to construct the holographic optical element that is used in a display where information i8 transmitted through the projection screen and where the projection and viewing axes are not coaxial.
Fig. 11 is an exemplary layout of the display system of the invention when the disp]ay information is transmitted through the projection screen, and where the projection and the viewing axes are coaxial.
Fig. 12 illustrates the geometry required to construct the holographic optical element where the ~isplay information is transmitted through the projection screen and where the recordinq geometry for the projection and the viewing axes are coaxial.

DESCRIPTION OF THE PREFERRED EM~ODIMENT

The typical layout of the display system of the invention i~ shown in Fig. 1. The display system consists of a projector 1, projection screen 2, and the necessary electronics 3 to support the projector 1. The projection screen 2 is mounted in a position which is overlaying a section of the instrument panel 4,`and which is shown magnified in Fiq. 3. It can be seen that the projection screen 2 is not perpendicular to the pro~ector 1 nor to the observer 5.

131~28~

The instrument panel 4 is a device that depicts a large amount of symbolic information about the status and situation of the aircraft to the pilot. The instrument panel 4 also contains a number of devices that allow the pilot to present information to the aircraft, such as display selection, altimeter settings, weapons set-up, enqine controls, etc. Input to the aircraft is accomp]ished by means of various knobs, switches, and buttons. The instruments are arranged so that they are functionally grouped, and all of the instruments must be visih]e from the "design eye," i.e., the area of the normal head posltion and the normal range of head movements of all pilots who will fly the aircraft. The knohs, switches, and buttons must all be reachable by the pilot without movinq from his normal flyinq position, with the exception of those items used only infrequently, or during .start-up or shut-down.
~ s shown in Fig. 2, the projector 1 consists of a 1-1.5 inch diameter cathode ray tube (CRT) 50 with a phosphor coating 52 of narrow spectral emission such as P-~3, and a relay lens assembly 29. The relay lens assembly 29 consists of conventional optical elements but may be implemented using holographic optical elements the properties of which are well known to those skilled in the art of holography. The optical elements ~ay ~e tilted and decentered to accommodate for the aberations that arise from the fact that the projector is not perpendicular to the projection screen. The aperture of the relay lens assembly 29 is preferably two inches in diameter, and the focal length is preferably such as to yield a 5X
magnification of the CRT image when~focused on the projection screen 2.
The projection screen 2 is implemented as a holoqraphic optical element sandwiched between two layers 1319~82 of fine Lexan, polymethyl methacrylate tPMMA), Plexiglas*
or glass, or, conversely, embossed on a suitable plastic such asr~ylar* polyester, or made from a holographic material sud~ as Polaroid DMP 128 (T.M. ~eg d), all of which are techniques well known in the art. The media for making the master holographs may be dichromated gelatin, while the techniques for makinq the hGloqraphic optical element tl~OE) are well-known two-step processes for qenerating imaqe-plane holoqrams. ~le source of light for generating the holograms is a green laser with its spectral output in the vicinity of the spectral emission of P-~3 phosphor.
~ny sma]l difference in matching the wavelengths can be compensated for by adjusting the geometry of the exposures, A technique which is well known in the art.
Fiq. 3 shows more clearly how the resulting HOE, which makes up the projection screen, is superimposed over the existing features of the instrument panel, such as gauges 26, switches 25, and the panel itself 24. Since the switches 25 extend outwardly from the panel, the ~OE is cut or punched out to permit said extension throuqh the ~IO~, and the cut out portions can be affixed to the surface of said switches, so as to provide a more or less continuous surface when seen from the optimal viewing area. Knobs, or other such narrow features 27 would simply protrude through the HOE and would not be covered witll a holographic cap .
Fig. ~ illustrates the geometry required to construct the transmission master hologram. The object to be holographed is an optical diffuser plate 6 which is back-lit with a wave front 7 propagating in a direction indicated by the arrow 8. This wil~ cause the diffuse light 9 to fa].l primarily on the film plate 10, which is dichromated qelatin or other such photographic material as is usual for holography. The plate 10 is also illuminated by a reference wave front 11 propaqating in the direction indicated by the arrow 12. After suitable exposure, the *Trade Mark 13192~

plate 10 is appropriately processed to yield the transmission master holoqram 13.
Fiq. 5 illustrates the qeometry required to construct the reflection copy hologram which will comprise the projection screen. The transmission master hologram 13 is illuminated with wave front 14 which is the conjugate of wave front 11. Wave front 1~ is propagatinq in the ~irection indicated by the arrow 15. This conjugate il]umination accomplishes the spatially undistorted projection of a real image of the diffuser 16. Film plate l7 is place~ adjacent to the real image of the diffuser 16 and is illuminated by a reference wave front 18 which propagates in the direction of arrow 19. The reference wave front 18 is converged to the point 20 by a lens 21.
Point 20 relative to the film plate 17 represents the relative location of the projector 1 with respect to the projection screen 2 in Fig. 1.
The trans~ission master hologram is masked by opaque material 22, 23 in a way such that the unmasked area corresponds to the observer's optimal viewing area(s).
After suitable exposure and subsequent processing, the film plate 17 becomes a reflection copy holoqram which comprises the projection screen of the display system. In commercial production, the plate 17 may be produced by holographic, printinq or embossing techniques which are well-Xnown in the art.
When the reflection copy holoqram is used as the projection screen 2, in the qeometry illustrated in Fiq.
1, it will have the followin~ properties: An imaqe comprised of symbols qenerated on the face of the CRT will be ~rojected onto the projection screen; an observer placinq his eyes in the viewinq area will see the image, maqnified 5X, coplanar or not with the projection screen;
the optimal viewing area will be uniformly illuminated with the light reflecting from the projection screen, by virtue of the diffusing element; no light will be 13~9282 _9_ reflected into areas other than the optimum viewing area;
and the projection screen will reflect only the liqht from the CRT, and will appear otherwise substantially transparent, so that symbols and features beneath the projection screen will be clearly visible throuqh the projection screen.
The instrument panel 4 may alternately employ a transmission hologram rather than the above-described reflection hologram. The transmission holographic instrument panel is analogous to the hologram of the reflection variety, except for the location of the CRT projector. As shown in Fig.
6, the projector 101 is located behind the instrument panel 104, facing the "design eye" of the observer 105. The projector 101 is supported by electronics 103. Fig. 6 illustratec the use of a transmission hologram 102 where the projection and viewing axes are not coaxial. The light projected from the CRT projector 101 is focused onto the hologram 102 of the holographic instrument panel 104 by means of the relay lens assembly 129. The hologram 102 is unimpeded by other features of the instrument panel and causes all of the light emanating from the relay lens 129 to be directed toward the design eye of the observer 115. This is a task that requires, among other things, that the HOE act as a semi-diffuser, since the design eye is a virtual aperture rather than a point in space.
Achromatization of the HOE display screens may be accomplished by varying the thickness of dichromated gelatin emulsion and using other well known practices.
~is may be done if it is necessary to display full color imaqes from a full color projector or from a plura]ity of di~ferent monochrome projectors of different co~ors.
Fig. 7 shows a holographic disp~lay for an instrument panel which is illuminated hy three projectors lOla, lOlh and lOlc, each presenting a different primary color although it is apparent that a single m~lticolor CR1' projector may also be used. In practice the projectors lO]a, lOlh, and lOlc should be positioned out of the line 13i~8~

of siqht of the observer 105, otherwise the images on the projectors may be seen directly through the holoqrams.
This happens because the holoqrams, as a practical matter, are not 100% efficient at redirecting the light focused upon them. As a consequence, some of the light from the projectors will pass through the holographic instrument panel as though the holograms were not there, and interfere with the viewing of the intended image. The positioning of the projectors and relay lenses out of the line of sight can be done in many ways, including the use of mirrors. Fiqs. 7-9 show only that the projectors are located to one side of the line of sight.
If a hologram is made from three beams, a reference and two object beams, then upon viewing, hoth objects will be visible. In like manner, the light from two separately located projectors could be directed toward the desiqn eye by a single hologram. Fig. 8 shows how such an arrangement can be used to satisfy the requirement for redundancy. Two projectors 101 of identical colors simultaneously have their images focused onto the holographic instrument panel 104 by their respective relay lenses. With suitable care, the images will overlap and appear as a single image, if both projectors are displaying identical images. If one of the projectors should fail, then the image from the other one would remain, and the only effect noticed by the viewer is that the brightness is diminished to half of the original. The above principle could be used to provide redundancy for each of the three primary colors, such as are projected by the projectors lOla, lOlb, and lOlc of Fig. 7. It should be apparent that the use of redund~nt projectors would apply equally to both transmis~ion and reflection holograms.
It would be possible to have the holographic instrument panel present images which appear to be three-dimensional. This can be done in several ways. As shown in Fi~. 9, the most effective i8 to have a liquid ~31 ~2 crystal lightgate or shutter 154 positioned in front o~
each eye 105, by means of a pair of qoggles. Signals from a computer 156 alternately render each crystal opaque, then clear. The two gates or shutters alternate exactly out of phase with each other, so that when one eye can see, the other can not, and vice versa. This alternation is synchroni~ed with the times at which the computer 156 generates the imaqes on the C~T projector, so that while the left eye was viewing the CRTs would be showing the image appropriate for the left eye and so forth. The system could be made to run at 60Hz or faster, so that the viewer would not be aware of the flicker. Rather the observer wou]d simply see a different image in each eye, which would be interpreted by the brain as normal stereopsis. Suitable systems for carryinq out this function are commercially available, a~ described in the article entitled "3-D TV", Popular Science, June 1988, pp.
58-63, 110. In the event that the system should fail, it can be so desi~ned that the liquid crystal shutters fail in the clear mode, and if that should happen, the computer can be instructed to present only one image, as with all the other examples described ahove.
Fiq. 10 illustrates the geometry required to construct the holoqraphic optical element in a transmission mode where the projection and viewing axe~ are not coaxial.
The source of light for generating the holograms is a qreen laser with its spectral output in the near vicinity of the spectral emission of P-~3 phosphor. Any small differences in spectra can be compensated for by a small adjustment in the geometry of the exposures. All other practice~ that are we]l-known to those skilled in the art of holography such as vibration isolation, path length matching, liquid gates, etc. are assumed.
The object to be holographed is an optical diffuser plate 159 which is back-lit with a wave front 160 propagating in a direction indicated by an arrow 161.

13192~

When the wave front 160 passes through the diffuser 159, the light appears to emanate from many point sources, as depicted by 162. The now diffuse wave front 162 is win~owe~ and/or apodized by a film transparency 163 and propagated towards a lens 164 as indicated by an arrow 165. The lens 164 relays the image of the apodi~ed and windowed diffuser via an object wave front 166 through a film plate (for example, of dichromated qelatin) 167 and an observer's viewing window 168. The focal length of the lens 164 and the location of the diffuser 159 and the film transparency 16~ are dependent on the required shape and location of the observer's viewing window 168 and may be calcu]ated using well-known optics formulae that relate the relaying of images through len~es. The film plate 167 must be entirely located in a triangular area bounded by a line 169, a line 170, and the lens 164. The lines 169 and 170 are lines of converqence from the perimeter of the lens 164.
A reference wave front 171 is made to appear to emanate from a point 172 by the focusing properties of a lens 173 which is illuminated by a wave front 174 propagatinq in a direction indicated by an arrow 175. The reference wave front 171 propagates in the direction indicated by an arrow 176 and passes through the film plate 167, totally illuminating the film plate 167. The reference wave front 171 must not pass through the lens 164 hefore it illuminates the film plate 167. The interference pattern formed by the reference wave front 171 and the object wave front 166 exposes the film plate 167. After suitable exposure time and subsequent processing, the film plate 167 beco~es a transmission holoqram which comprises the projection screen 102 of the display system of Fig. 6. The wave front 174 and the wave front 160 are derived from a common green laser source and thus maintain a common phase relationship to each other.
Multiple viewing windows may be generated by having a 13~ ~282 p]urality of transparent areas on th0 film transparency 163 or a multiplicity of diffuser/transparency/lens arrangements. Multiple exposures of the film plate 167 using different diffuser/transparency/lens arrangement~
while retaining the same reference beam would also yield multiple viewing windows.
The film transparency 16~ is made of a transparent substrate such as plastic or glass and is covered with a material that blocks the passage of light in varying amounts. The pattern of the light blocking material on the film transparency 163 is distributed in accordance with the requirements of the observer viewinq window 68 as seen throuqh the lens 164. The relationship of the pattern on the film transparency 163 to the shape and intensity profile requirements of the observer viewing window 168 as seen through the lens 164 is relatefl using well-known formulae for the relaying of images through lenses.
It should be noted that in using the recordinq method shown in Fig. 10, the geometry may be moflified such that the observer viewing window 168 and the reference wave front 171 may have angles of orientation with respect to the film plate 167 which can be varied to allow for off axis projection angles or on axis observer viewing windows. The limitation of this recording geometry is that having an on axis observer viewing window and on axis projection is not possible simultaneously.
A typical layout of the display system for a transmission hologram where the projection and viewing axes are coaxial is shown in Fig. 11. The display system comprises a projector 177, a project'ion screen 178, and tlle necessary electronics 179, to support the projector 177. It can be seen that the projection screen 178 is perpendicular to the observer 180 as well as to the projector 177.

~ 3192~2 Fig. 12 illustrates the geometry required to construct the holographic optical element in a transmission hologram where the projection and viewing axes are coaxial. The source of light for qenerating the holograms is a qreen laser with its spectral output in the near vicinity of the spectral emission of P-43 phosphor. Any sma]l difference in .spectra can be compensated for by a small adjustment in the qeometry of the exposures. All other practices that are well-known to those skillefl in the art of holography, such as vibration isolation, path length matching, etc.
are assumed.
The object to be holographed is an optical diffuser plate 181 which is back-lit with a wave front 182 propagated in a direction indicated by an arrow 183. When the wave front 182 passes through the diffu~er plate 181, the liqht appears to emanate from many point ~ources as depicted by 184. The now diffuse wave front 184 is windowed and apodized by a film transparency 185 and propagates towards a beam splitter 186 as indicated by an arrow 187. The diffuse wave front 184 passes through the beam splitter 186 and a lens 202 relays the image of the apodized and windowed diffuser via an object wave front 188 through a film plate (dichromated gelatin) 189 to an observer's viewing window 190. The focal length of the len~ 202 and the location of the diffuser 181 and film transparency 185 are dependent on the required shape and location of observer's viewing window 190 and may be calculated using well-known optics formulae that relate the relaying of images through lenses. The film plate 189 must be located entirely within a triangular area bounded by a line 191, a line 192, and the ~ens 202. The lines 191 and 192 are lines of convergence from the perimeter of the lens 202.
A reference wave front 193 is made to appear to emanate from the point 194 by the focusing properties of a lens 195 which is illuminated by a wave front 196 13~9282 propagating in a direction indicated by an arrow 197. The reference wave front 193 propa~ates in the direction indicated by an arrow 198, substantially reflect~ from the beam splitter 186, is redirected in a direction indicated by an arrow 199 and passes through the lens 202. By the optical combining properties of the beam splitter 186, the reference beam 193 is made to appear to be emanating from a direction which is to the left of perpendicular to the lens 202. When viewed from the location of the film plate 189 due to optical refractinq properties of the lens 202, the distance from which the reference beam appear~ to be coming is longer than the sum of the distances from the film plate 189 to a point 200 and from the point 200 to the point 19~. The distance from which the reference beam appears to be coming must match the di~tance between the projector 177 and the display screen 178 in Fig. 10.
Knowing the distance between the projector 177 and the display screen 178 and knowin~ the focal length of the lens 202 allows the required location of point 194 to be easily calculated using well-known formulas that relate conjugate points of refracting lenses.
The reference beam 193 which is reflected towards the lens 202 by the beam splitter 186 is refracted through the lens 202 and passes through the film plate 189 totally illuminating the film plate 189 as a refracted reference wave front 201. The refracted reference wave front 201 must totally illuminate the film plate 189. The interference pattern formed by the refracted reference wave front 201 and the object wave front 188 exposes the film plate 189. After suitab]e exposure time and subsequent processinq the film pla~e 189 becomes a transmission hologram which comprises the projection screen 178 of the display system of Fig. 11. The wave front 196 and the wave front 182 are derived from a common green laser source and thus maintain a common phase relationship to each other.

13~ ~2~2 Multiple viewing windows may be qenerated by having a plurality of transparent areas on the film transparency 185 or a multiplicity of diffuser/transparency/lens arranqements. Multiple exposures of the film plate 189 using different diffusers/transparency/len3 arrangements while retaining the same xeference beam would also yield multiple viewing window~.
The film transparency 185 is made of a transparent substrate such as plastic or glass and is covered with a material that blocks the passage of light in varying amounts. The pattern of the light blocking material on the film transparency 185 is distributed in accordance with the requirements of the observer viewing window 190 aQ seen through the lens 202. The relationship of the pattern on the film tran~parency 185 to the shape and intensity profile requirements of the observer viewing window 190 as seen through the lens 202 is related using well-known formulae for the relaying of images through lenses.
It is understood that the invention is not limited to the particular embodiments set forth herein, but embraces such modified forms thereof as come within the scope of the following claims.

Claims (17)

1. A holographic optical system for use with an instrument panel, the holographic optical system comprising:
(a) a hologram positioned so as to redirect an image generated at a place other than the instrument panel, the hologram being formed to act in the manner of a diffuser and such that the viewing window of the redirected image is controlled so as to prevent light from the hologram from shining towards regions other than a region to be occupied by the viewer's head; and (b) means for producing an image at a position away from the instrument panel and for projecting and focusing the image onto the hologram.

2. The holographic optical system of Claim 1 wherein the hologram is superimposed with and positioned on or adjacent an existing instrument of an instrument panel.

3. The holographic optical system of Claim 1 wherein the image is redirected to transmit through the hologram to the side of the instrument panel opposite the means for producing, projecting and focusing an image.

4. The holographic optical system of Claim 1 wherein the means for producing and projecting and focusing the image includes a cathode ray tube located remote from the instrument panel and facing generally towards said panel.

5. The holographic optical system of Claim 1 wherein the hologram is formed directly onto a sheet of clear material such as plastic.

6. The holographic optical system of Claim 1 wherein the hologram is formed of a number of smaller holograms, each one directed so as to redirect the image toward the viewer' 5 eyes.

7. The holographic optical system of Claim 2 wherein the hologram has holes cut into it through which project mechanical features of the instrument panel such as knobs, keys and switches.

8. The holographic optical system of Claim 7 wherein portions of the features which protrude through the hologram are themselves covered with holograms having substantially the same function as the background hologram.

9. The holographic optical system of Claim 4 wherein the means for producing and projecting and focusing the image includes a relay lens receiving light from the cathode ray tube.

10. The holographic optical system of Claim 1 wherein there are a plurality of holograms and an equal plurality of means for producing, projecting and focusing images, each of the holograms producing an image dissimilar and independent of the other holograms and having a corresponding means for producing, projecting and focusing that image.

11. The holographic optical system of Claim 1 wherein there are a plurality of holograms and an equal plurality of means for producing, projecting and focusing images, each of the holograms producing identical images and having a corresponding means for producing and projecting that image.

12. The holographic optical system of Claim 11 wherein the plurality of images are in alignment.

13. The holographic optical system of Claim 11 further including a pair of controllable light gates wherein a viewer of the image produced away from the instrument panel has a light gate in front of each eye which alternates phases between opaque and clear so that when one gate is opaque the other gate is clear and vice versa, and wherein the plurality of means for producing and projecting images is synchronized with the alternation of phases of the gates so that during the clear phase of each gate the holographic optical system produces an image appropriate to the particular eye behind that gate to create stereopsis.

14. A method of generating an image for use with an instrument panel, the method comprising the steps of:
(a) producing an image at a position away from the instrument panel;
(b) projecting and focusing the image onto a hologram at the instrument panel;
(c) redirecting the image with the hologram to a viewing window located at a place other than the instrument panel so as to prevent light from shining towards regions other than a region to be occupied by the viewer's head.

15. The method of Claim 14 wherein the step of redirecting the image is accomplished by transmitting through the hologram with the hologram being formed to transmit the light of the image ina direction off axis from the direction in which the light of the image was projected onto the hologram.

16. The method of Claim 14 wherein the step of redirecting the image is accomplished by reflecting off of the hologram.

17. The method of Claim 16 wherein the hologram is superimposed with and positioned on or adjacent an existing instrument of the instrument panel.