TECHNICAL FIELD

The present disclosure relates to a stereoscopic display system. Particularly, but not exclusively, the disclosure relates to a multi-view autostereoscopic head-up display, such as a windscreen, for use in a vehicle.

BACKGROUND

Heads-up displays (HUDs) are known displays where images are projected onto a transparent surface, such as a windscreen or visor. Such displays are well known in a number of different environments including in vehicles.

In automotive HUDs information regarding car conditions (speed etc.), or navigation, may be displayed onto the windscreen. Such displays are typically limited in size and project the image at a fixed depth to the user. Due to the limited size, the HUD may be cluttered with information that is less relevant to the user taking up real estate on the display. Such displays are also known to suffer from a limited field of view, low resolution and low brightness. Furthermore, as the image is of a fixed depth all information presented to the user is given equally prominence. This further reduces the efficiency of such displays.

A further consideration is that in vehicles there is typically limited physical space in which such systems can be installed. Typically, such systems must be incorporated into existing spaces present in a vehicle, or installed in as small a space as possible to minimise the need to remove, and reinstall, existing components. Furthermore, in such systems there is a cost associated with the introduction and installation.

An object of the present invention is to mitigate some of the deficiencies of the prior art mentioned above.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an apparatus as claimed in the appended claims. An advantage according to an aspect of the invention is that there is provided an imaging system for generating a stereoscopic image on a display, the imaging system comprising a first picture generation unit for generating a first image of a first stereo image pair, a second picture generation unit for generating a second image of the first stereo image pair, and projection optics for rendering images on the display, wherein the first picture generation unit is arranged such that the first image is projected through the projection optics onto a first virtual area of the display, and wherein the second picture generation unit is arranged such that the second image is projected through the projection optics onto a second virtual area of the display, wherein the projection optics are configured such that a copy of the first image is projected onto a third virtual area of the display, and a copy of the second image is projected onto a fourth virtual area of the display, wherein the first image on the first virtual area of the display and the second image on the second virtual area of the display form a first stereoscopic image on the display, and wherein the copy of the first image on the third virtual area of the display and copy of the second image on the fourth virtual area of the display form a second stereoscopic image on the display.

Accordingly, the apparent depth of an image is provided by binocular disparity rather than by varying the distance between a diffuser and magnifying optics a projector and a diffuser. The imaging system can therefore produce an effective 3D display whilst taking up less space than conventional HUDs. Further, the same stereo image pair can be projected onto two pairs of eye-boxes, allowing the user to look from different angles and/or at different parts of the display without losing sight of any of the projected information.

Optionally, the first and second images are substantially identical to their respective copies.

Optionally, the first and second virtual areas at least partially overlap.

Optionally, the third and fourth virtual areas at least partially overlap.

Optionally, the first, second, third and fourth virtual areas at least partially overlap with each other.

Optionally, the first, second, third and fourth virtual areas correspond to a first, second, third and fourth eye-boxes respectively. Optionally, the projection optics comprise focussing optics. This allows for addition fine tuning or any necessary redirection of the resulting virtual images on the display screen of the head- up display.

Optionally, the projection optics comprise magnifying optics.

Optionally, the focussing optics comprise a Fresnel lens.

Optionally, the projection optics comprise a beam splitter arranged such that light from both the first and second picture generation units is directed towards the Fresnel lens.

Optionally, the first and second picture generation units and the projection optics are arranged such that the first, second, third and fourth image are projected through the projection optics with a spatial offset, resulting in their separation on the display.

Optionally, the first and second picture generation units and the projection optics are arranged such that the first, second, third and fourth image are projected through the projection optics with an angular offset, resulting in their separation on the display.

Optionally, the relative spatial offset of each of the images is equal.

Optionally, the relative angular offset of each of the images is equal.

An advantage according to a second aspect of the invention is that there is provided an imaging system for generating a stereoscopic image on a display, the imaging system comprising a first picture generation unit for generating a first image of a first stereo image pair, a second picture generation unit for generating a second image of the first stereo image pair, a third picture generation unit for generating a third image of a second stereo image pair, and a fourth picture generation unit for generating a fourth image of the second stereo image pair, projection optics for rendering images on the display; wherein the first picture generation unit is arranged such that the first image is projected through the projection optics onto a first virtual area of the display, and wherein the second picture generation unit is arranged such that the second image is projected through the projection optics onto a second virtual area of the display such that the first and second image form a first stereoscopic image on the display wherein the third picture generation unit is arranged such that the third image is projected through the projection optics onto a third virtual area of the display, and wherein the fourth picture generation unit is arranged such that the fourth image is projected through the projection optics onto a fourth virtual area of the display such that the third and fourth image form a second stereoscopic image on the display.

Accordingly, multiple stereo images can be projected onto neighbouring eye-boxes via different regions of the windscreen, allowing for a greater range of movement of the user's head/eyes before the projected images can no longer be seen. Further, neighbouring eye- boxes can display corresponding images in order to effectively increase the range of apparent depths at which an object can be displayed. Moreover, the autostereoscopic display is effectively extended to a multi-view display, which can be a multi-stereoscopic display. The additional PGUs can be used to add further directionality, such that the viewed compound image may be viewed at different angles as the user shifts their head in either of two dimensions.

Optionally, the first, second, third and fourth virtual areas of the display correspond to a first, second, third and fourth eye-box respectively.

Optionally, one or more of the picture generation units comprise a neutral density filter at their output.

Optionally, one or more of the picture generation units comprise a projector and a diffuser for realising the projected image.

Optionally, the picture generation units comprise a laser and a 2D scanning mirror for rendering the images on the diffuser.

Optionally, the picture generation units comprise a holographic unit to produce computer generated holograms and a diffuser for realising the holograms.

Optionally, the picture generation units comprise a light field unit to produce 3-dimentional light field images. The projection of 3-dimentional images through the imaging system enables such images to be displayed with the appropriate varying depth so as to produce a convincing representation of a real object.

Optionally, the picture generation units comprise OLED, microLED, QLED and/or LED devices. Such devices are capable of being activated by the application of current, which can be localised and modulated as desired. They can further provide a flexible, multi-colour display Optionally, the picture generation units comprise one of a digital light processing digital micromirror device, a liquid crystal on silicon device and a liquid crystal display device.

Optionally, the projection optics are translatable so as to change the size and offset of the stereoscopic images.

Optionally, the imaging system further comprises eye tracking means and a controller, the controller configured to track the eyes of one or more users and calculate the location of the corresponding eye boxes, and adjust the arrangement of the projection optics and/or the picture generation units such that a stereoscopic image is projected onto the portion of the display corresponding to the respective eye-box.

Other aspects of the invention will be apparent from the appended claim set.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic of the imaging system according to an aspect of the invention;

Figure 2 is a schematic of the imaging system according to an aspect of the invention;

Figure 3 is a schematic of the imaging system according to an aspect of the invention;

Figure 4 is a schematic of the imaging systems according to an aspect of the invention; Figure 5 is a schematic of the imaging system according to an aspect of the invention;

Figure 6 is a schematic of the imaging system according to an aspect of the invention;

Figure 7 is a schematic of the imaging system according to an aspect of the invention;

Figure 8 is a schematic of the imaging system according to an aspect of the invention;

Figure 9 is a schematic of the imaging system according to an aspect of the invention; and Figure 10 is a schematic of the imaging system according to an aspect of the invention.

DETAILED DESCRIPTION

In an aspect of the invention the apparatus and the display are installed in a vehicle, such as a motor vehicle. Whilst the following description is described with reference to a HUD of a motor vehicle, the disclosure, and concepts described herein are applicable to other forms of HUD (for example those installed on other forms of vehicles or wearable platforms such as helmets or goggles), as well as displays in general, not just HUDs.

In particular, where the invention is installed for use in a confined environment such as a vehicle which can be operated on land (on/off road or track), under or over sea, in air or space. The examples can be, but not limited to, cars, buses, lorries, excavators, exoskeleton suit for heavy-duty tasks, motorcycles, trains, theme park rides; submarines, ships, boats, yachts, jet- skies for see vehicles; planes, gliders for air crafts, spaceships, shuttles for space crafts. Furthermore, the technology can be installed/integrated in a mobile platform such as a driver’s/operator’s head/eye protection apparatus such as a helmet or goggles. Therefore, any activity, which involves in wearing protective helmets/goggles, can benefit from this technology. These can be worn, but not limited to, by motorcyclist/cyclist, skiers, astronauts, exoskeleton operators, military personnel, miners, scuba divers, construction workers. Moreover, it can be used in a standalone environment for game consoles, arcade machines and with a combination of an external 2D/3D display it can be used as a simulation platform. Also, it can be used in institutions and museums for educational and entertainment purposes.

The apparatus described herein is able to generate an image which can be presented at various depths. Whilst the generation of the images at multiple depths on the HUD provides many advantages over a flat, single depth image the ability to correct for factors such as the curvature of the windscreen results in further improvements in terms of depth control and image manipulation.

Figure 1 shows an imaging system 10 made up of a first picture generation unit (PGU) 100 and a second picture generation unit 200. Each picture generation unit 100, 200 comprises imaging optics 701 and 702 respectively. In some optional embodiments, each picture generation unit 100, 200 has a corresponding light filter (not shown) located at an output of the picture generation unit 100 200. In such embodiments pictures generated by the picture generation unit 100 200 will pass through the corresponding light filter. In embodiments where there is no light filter the pictures generated by the picture generation unit 100200 pass directly to the imaging optics as explained below.

The picture generation units 100, 200 are provided by a digital light processing (DMD) projector, though the skilled person would appreciate that any suitable light source and imaging means may be used provided they were capable of operating in the manner described below. Accordingly, in an embodiment the picture generation units 100, 200 are formed of a laser and a 2D scanning mirror, or a holographic unit which produces computer generated holograms for forming on the image realisation surfaces. In an alternative embodiment, the picture generation units 100, 200 are light field units to produce 3-dimentional light field images for forming on the image realisation surfaces. Liquid crystal display (LCD) device, liquid crystal on silicon (LCoS) display, laser projector, light-emitting diode (LED) display, organic light- emitting diode (OLED) display, quantum-dot light-emitting diode (QLED) display and micro- light-emitting diode (pLED) display may also be used in the PGUs or as the PGUs. The skilled person would understand that in the DMD, LCOS and LCD embodiments each PGU would further comprise an initial light source. In contrast, PGUs comprising LEDs would not require any further light emitting components.

The first and second picture generation units 100 and 200 are configured to project light onto a beam-splitter 110 which subsequently directs a portion of the light from both PGUs through a Fresnel lens 150 and onto a windscreen 600. The Fresnel lens 150 converges the projected images onto the windscreen 600. The skilled person would appreciate that any suitable focussing optics may be used. The PGUs and beam splitter are arranged such that light from the first picture generation unit is transmitted through to the Fresnel lens 150, whilst light from the second picture generation unit is reflected onto the Fresnel lens 150 and onto the windscreen 600.

The path of the light from the picture generation units 100, 200, transmitted through or reflected by the beam splitter 1 10 and through the Fresnel lens 150 and onto the windscreen 600 is referred to as the optical path. The skilled person would understand that any number of intervening reflectors/lens or other optical components may be placed along the optical path between the picture generation units 100, 200, the beam splitter 1 10 and the Fresnel lens 150, to manipulate the optical path as necessary (for example, to minimize the overall size of the imaging system 10). In use, a first image 101 is generated by the first picture generation unit 100 through the beam splitter and is subsequently transmitted through the Fresnel lens 150. The first image 101 is then reflected off the windscreen onto one eye of a user. A second image 201 generated by the second picture generation unit 200 is similarly projected onto the other eye of the user. The brightness of each image can be independently controlled by the light filters (if present) or by varying the current supplied to the light source of the PGUs. In an embodiment, the picture generation units are able to account for any distortion resulting from the transmission of light through components used to manipulate the optical path, such that the final images visible to the user are correctly displayed. In an embodiment, this is achieved by a software- based distortion correction module in (or otherwise in communication with) the picture generation units that applies a pre-compensating inverse distortion to the image in the digital domain before it is projected. In an embodiment, the distortion correction module calculates the expected distortion from the optical components of the projecting optics and the display and determines the inverse distortion that must be applied such that the final images visible to a user are undistorted. In a further embodiment, the pre-compensating distortion applied to one image can be different to that applied to another. This allows for the PGUs to account for asymmetries in the optical path of each image. Such pre-compensating distortions can be determined by software in a known manner. This obviates the need for any post-image generation corrections as well as bulky correction optics. Furthermore, it provides a higher degree of flexibility which can adapt to different display/mirror surfaces and optical setups.

By varying the tilt of either the picture generation unit 100, 200 or the beam splitter 110 relative to the Fresnel lens 150, the system 10 can vary the exact location of the windscreen 600 onto which each of the first and second image 101 , 201 are projected, so as to ensure the image is reflected into the corresponding eye of the user. The portion of the windscreen 600 that reflects an image to an eye of the user is referred to as a directional display region 611/621. The area of the viewing plane within which a user's eye must be located in order to see the image reflected by the directional display region 611/621 is referred to as an eye-box. In an embodiment, the distance between the centres of any two neighbouring eye-boxes 51 1 , 521 is the average inter-pupil distance of 65 mm. In further embodiments other sizes of eye-box may be used.

In an embodiment, the first and second images 101 , 201 are the same image, such that the system 10 provides a 2D display. In an alternative embodiment, the first and second images 101 , 201 are stereo pairs, providing a 3D effect. In a further embodiment the images are a mixture of stereo and non-stereo images, with portions of the first and second image are the same, whereas other portions form stereo pairs across the two images 101 , 201. In this way, the system can project both 2D and 3D images to a user.

Accordingly, the apparatus described above allows the creation of the 2D and 3D images in a space saving manner. In embodiment in which the PGU comprises one of a DMD, LCoS, LCD or LED, OLED, QLED, pLED, further space saving is achieved as no image realisation surface or diffuser is required.

Figures 2 and 3 show an alternative set up according to an aspect of the invention.

In Figures 2 and 3, the first and second picture generation units 100, 200 are arranged to project light onto the beam splitter 110 which is transmitted/reflected towards the Fresnel lens 150 as described in relation to Figure 1.

A first portion of the light from the first picture generation unit 100 is transmitted through the beam splitter 1 10 and reflected by a first mirror 1 1 1 back towards the beam splitter 1 10 and through to the Fresnel lens 150. A second portion of the light from the first picture generation unit 100 is reflected by the beam splitter 110 onto a second mirror 112 which reflects the light back towards the beam splitter 1 10 and through to the Fresnel lens 150.

Similarly, a first portion of the light from the second picture generation unit 200 is transmitted through the beam splitter 110 and reflected by the second mirror 112 back towards the beam splitter 1 10 and through to the Fresnel lens 150. A second portion of the light from the second picture generation unit 200 is reflected by the beam splitter 110 onto the first mirror 11 1 which reflects the light back towards the beam splitter 110 and through to the Fresnel lens 150. Any light that is transmitted or reflected away from the Fresnel lens 150 is captured by a beam dump 130. Though mirrors 1 11 and 1 12 are shown as planar, the skilled person would understand that they may also be curved and still function as described. In an embodiment, mirrors 1 1 1 and 1 12 are curved so as to reduce the diverging angle of the light coming out of the picture generation units.

This setup provides four images 101 , 201 , 102 and 202 which are directed towards corresponding first, second, third and fourth eye-boxes 51 1 , 521 , 512, 522 respectively via corresponding directional display regions 61 1 , 621 , 612, 622 of the windscreen 600 (not shown in Figure 3). In use, because the four images are generated from only two picture generation units, the third and fourth image 102, 202 are the same as the first and second image 101 , 201 respectively. Accordingly, the same stereo image pair can be projected onto two pairs of eye-boxes, allowing the user to look from different angles and/or at different parts of the windscreen 600 without losing sight of any of the projected information.

In Figure 2, the first and second projector 100, 200 are arranged to project light onto different incident points of the beam splitter 1 10 resulting in a spatial offset of the first, second, third and fourth images 101 , 201 , 102, 202.

In Figure 3, the first and second projector 100, 200 are arranged to project light onto the same incident point of the beam splitter 110 but at a relative angle such that the transmitted and reflected light from each PGU diverges and produces each of the first, second, third and fourth images 101 , 201 , 102, 202 at relative angular offset.

In the depicted embodiments, the images are equally offset, either spatially or by angle. In alternative embodiment, the relative offset can vary. In a further embodiment, the distance between the centres of any two neighbouring eye-boxes 51 1 , 512, 521 , 522 is equal to the average inter-pupil distance of 65 mm.

Figure 4 shows an alternative embodiment to that of Figures 2 and 3 in which the beam dump 130 is replaced with a third mirror 113. In use, light is emitted from the first and second projectors 100, 200 and interacts with the first and second mirrors 1 11 , 1 12 and the beam splitter 1 10 as described above in relation to either of Figures 2 and 3. The third mirror 113 is then positioned to ensure all reflected and transmitted light originating from the projectors 100, 200 is directed towards the Fresnel lens 150.

This setup provides an additional four images 103, 203, 104 and 204 which are directed towards corresponding fifth, sixth, seventh and eighth eye-boxes 513, 523, 514, 524 respectively via corresponding directional display regions (which are not shown, for simplicity). Accordingly, the same stereo image pair is be projected onto four pairs of eye-boxes, further broadening the angular range from which a user may view the windscreen 600 without losing sight of any of the projected information.

Figure 5 shows an alternative setup according to an aspect of the invention. In figure 5 a first, second, third and fourth picture generation units 100, 200, 300, 400 are arranged to project a first, second, third and fourth image 101 , 102, 103, 104 through Fresnel lens 150 at a different angle relative to the axis of the lens. In an embodiment each picture generation unit has a light filter at its output. In further embodiments no filter is present at the output of the PGUs.

This produces angularly tilted images exiting the lens 150 which are thus spread across four eye-boxes.

In an embodiment, all four picture generation units are at an equal angle to their neighbours. In an alternative embodiment, the angle of each picture generation unit can take any value.

In one embodiment, the four images provide two stereo image pairs. As a result, the user can see a first pair of stereo images when their eyes are in two neighbouring eye-boxes. When the user moves their head/eyes, they see the second pair of stereo images. In an embodiment, the second pair relates to the first pair so as to display a corresponding image at a different angle, providing an effective 3D image across a wide range of user movement. Any two neighbouring eye-boxes can provide a pair of stereo images of a different viewing angle.

Figures 6 and 7 show embodiments of the invention that utilise scanning mirrors 801 and 802. The remaining reference numerals correspond to the same components as those of Figures 1-5 and have the same functionality as described above.

Figure 6 depicts an embodiment in which light from the PGU 100 is directed towards a single scanning mirror 801 before being reflected through the Fresnel lens 150.

The scanning mirror 801 selectively directed different images generated by the PGU 100 towards different eye-boxes 511 , 521 by imparting an angular offset. In the depicted embodiment, the scanning mirror 801 directs images towards two eye-boxes 51 1 , 521 , separated along a first axis. It should be noted that the maximum number of separate images and corresponding eye-boxes is limited only by the scanning mirror speed, such that embodiments with more than two images/eye-boxes are envisaged.

In use, the PGU 100 and the scanning mirror 801 are synchronised such that images 101 and 201 form a stereo image pair. These images are then displayed to neighbouring eye-boxes 511 and 521 in the same manner as described above in relation to Figure 1. Figure 7 depicts and embodiment in which light from the PGH 100 is directed towards a first scanning mirror 801 before being directed onto a second scanning mirror 802.

The two scanning mirrors 801 , 802 work in unison to direct the images projected by the PGU towards four eye-boxes 511 , 521 , 512, 522, with the eye-boxes 51 1 , 521 corresponding to the first scanning mirror 801 being offset from the eye-boxes corresponding to the second scanning mirror 802 along a second axis. Otherwise, this embodiment functions in the same way as the embodiment of Figure 6.

Figures 8, 9 and 10 show embodiments of the invention that utilise one, or more, digital micro mirror devices 803, 804 in conjunction with a prism 805. The remaining reference numerals correspond to the same components as those of Figures 1-7.

The digital micro mirror device (DMD) is a DMD known in the art. DMD 803 performs a similar function to the scanning mirror 801 , with the PGU 100 being arranged so as to project light into the prism 805 which is subsequently reflected onto the DMD 803. The DMD has a number of micro-mirrors that rotate depending on whether the DMD is in an on-state or an off-state. When the DMD 803 is in the on-state, light from the PGU 100 is directed towards a first eye- box 51 1. When the DMD 803 is in the off-state, light from the PGU 100 is directed towards a second eye-box 521. In an embodiment, the number of micro-mirrors preferably corresponds to the number of pixels in the image generated by the PGU 100.

In use, light reflected onto the DMD is directed towards a particular eye-box 511 , 521 depending on the state of the DMD, with the two eye-boxes 51 1 , 521 being separated along a first axis. PGU and DMD are synchronised so that images 101 , 201 displayed at the eye- boxes 511 , 521 form a stereo image pair.

Figures 9 and 10 depict embodiments in which a first and second DMD 803, 804 is used. The DMDs are arranged such that light from the PGU 100 is reflected by the prism 805 towards the first DMD 803, whilst light transmitted by the prism 805 is directed towards the second DMD 804.

As in the embodiment shown in Figures 9 and 10, each DMD is able to direct light from the PGU 100 to one of two eye-boxes, providing a total of four eye-boxes 51 1 , 521 , 512, 522.

In the depicted embodiment, the first DMD 803 has a smaller steering angle than the second DMD 804, such that the images 101 , 201 in the middle two eye-boxes 511 , 521 correspond to light reflected by the first DMD 803, with the second DMD 804 directing images 102, 202 towards the outer eye-boxes 512, 522.

In an alternative embodiment, the first and second DMDs 803, 804 have the same steering angle, such that the two left-most eye-boxes correspond to one DMD, with the two right-most eye-boxes corresponding to the other DMD.

Figure 10 depicts a further embodiment in which the first and second DMDs 803, 804 are arranged such that the eye-boxes corresponding to the first DMD 803 are offset to those corresponding to the second DMD 804 along a second axis, as with the embodiment of Figure 7.

Accordingly, there is provided an imaging system in accordance with an aspect of the invention.