GB2508404A

GB2508404A - Display Projecting Image onto Inclined Transparent Panel with Semi-Reflective Coating

Info

Publication number: GB2508404A
Application number: GB1221596.8A
Authority: GB
Inventors: Barry Patrick Skinner; Michael Scott
Original assignee: Individual
Current assignee: BARRY PATRICK SKINNER; MICHAEL SCOTT
Priority date: 2012-11-30
Filing date: 2012-11-30
Publication date: 2014-06-04

Abstract

A display comprises a transparent glass panel with front and rear surfaces, with an image forming device projecting an image onto the front surface. The panel is inclined relative to the projected image, such that the projected image appears superimposed onto the background visible through the transparent panel (e.g. peppers ghost); with the transparent panel having a semi-reflective coating on the front and anti-reflective coating on the rear. The semi-reflective coating may have luminous reflectance (Pva) of 36% Â± 5% and luminous transmittance (Tva) of 59% Â± 5%. The panel may be at 45Â± 10 degrees from the image forming device. A frame supports the panel/s, and the transparent panel is visible within 90 degrees of the front of the display. Image forming device has a minimum resolution of 2 million pixels with brightness of 2000 cd/m2 or 2500 cd/m2 for 2D or 3D images respectively.

Description

Display And Method Of Displaying An Image The present invention relates to a display and to a method of displaying an image.

Preferred embodiments of the present invention may find application in displays in a wide range of commercial applications, not least for advertising or promotions, employed in retail shop windows and stores, shopping centres, information displays in airports as well as many other applications. The displays can be employed free standing, elevated and suspended and of any size. The displays are capable of projecting 2D or 3D images. The preferred displays are particularly effective in displaying a virtual hologram image in a high ambient light conditions and where a wide viewing angle is desired.

The preferred embodiment work on the general principle of "Pepper's ghost".

Pepper's ghost is a well irnown optical illusion used in theatres and the like named after John Henry Pepper who popularised the effect. Using plate glass and special lighting techniques, objects can be made to seemingly appear or disappear. In operation, the viewer looks onto a scene in a first room. A semi-reflective piece of plate glass is positioned between the viewer and the first room and angled to partially reflect a hidden room off to the side. The hidden room has a black background or a background that matches the first room. An object in the hidden room, when appropriately lighted, has its image reflected towards the user by the glass sheet and seems to the viewer to be superimposed on their view of the first room, making it seem as if a "ghostly" object or hologram has appeared in the first room. This effect has been used in television, film and concerts to achieve various optical effects. In more modern implementations, a projector is used to project an image from the side onto the glass sheet to be superimposed onto the scene seen by the viewer. Current known techniques suffer from requiring particular lighting conditions to be effective and!or restricting viewing angles, as well as suffering from image "ghosting", all of which makes them unsuitable for being used in high ambient light conditions. Thus, current techniques are oflimited applicability.

WO-A-2009/105847 discloses a device for visualising images using the Pepper's ghost principle wherein an image generating element projects on to a partly transparent minor and is projected to the viewer. These elements are enclosed by a cuboid housing with a window through which the viewer can see the projected image. The housing has light absorbing layers on the interior surfaces to reduce undesirable interference by scattered light. Thus the viewer sees the image against a black backgmund. A thin mirror is said to be preferred to reduce ghosting in the image. A drawback ofthis arrangement is that the viewing angle of the image is relatively restricted due to the housing and the limited size of the window. The image also appears against a black background. These constraints tend to reduce the realism for the viewer of the effect of a 3D object floating in space and thus preclude a true "virtual hologram" being produced as well as restricting the uses to which the device can be put.

Back projection screens are also known for virtual displays in which a projector is used to project an image on a surface, such as a semi-transparent screen. These typically suffer from the problem that there is a limited viewing angle from which a realistic view of the image can be seen, and that a realistic virtual hologram effect is difficult to achieve.

According to a first aspect of the present invention, there is provided a display comprising: a transparent panel having a front surface and a rear surface; a image forming device arranged to project an image onto the front surface of the transparent panel, the transparent panel being inclined relative to the projected image, such that in use for a viewer looking from the front of the display, the image is superimposed onto the background visible through the transparent panel, the transparent panel having a semi-reflective coating on the front surface, and an anti-reflective coating on the rear surface.

According to a second aspect of the present invention, there is provided a method of displaying an image using a display comprising a transparent panel having a front surface and a rear surface a image forming device, the method comprising projecting an image onto the front surface of the transparent panel, the transparent panel being inclined relative to the projected image, such that for a viewer looking from the front of the display, the image is superimposed onto the background visible through the transparent panel, wherein the transparent panel has a semi-reflective coating on the front surface, and an anti-rcflcctivc coating on thc rcar surfacc.

The invention provides an improved display compared with prior art techniques whereby the image can be displayed with more clarity in high ambient light conditions without the need for masking or shielding of the transparent panel. This allows a natural, realistic looking image to be displayed in a wide range of lighting conditions. In preferred embodiments, the ability to do away with masking or shielding of the transparcnt pancl mcans that thc imagc can bc sccn from a widc vicwing anglc ffirthcr increasing the realism attainable by the projected image. The use of an anti-reflective coating helps minimise possible ghosting effects.

Prcfcrably, thc scmi-rcflcctivc coating has a Luminous rcflcctancc (Pva) of 36% 5% and a Luminous transmittance (Tva) ofS9% + 5%. These are particularly preferred charactcristics of thc coatings to achicvc a strong, clcar iniagc in high ambicnt light conditions without the use of masking.

In an cmbodimcnt, thc rcflcctivc coating is Titanium.

Preferably, the transparent panel is a glass panel. In an embodiment, the glass panel is a thermally tempered or laminated safety glass. This allows the display to be uscd safcly in public arcas whilst having good optical propcrtics such as clarity and homogeneity.

Preferably, the transparent panel is at least 4mm thick. This allows the panel to be stronger. For thicker transparent panels, the problem of potential double images being generated increases. The anti-reflective coating is particularly useful in this embodiment for eliminating or at least reducing significantly the possibility of double images being gcncratcd.

Preferably, the transparent panel is at 45 + 10 degrees from the image forming device. This achieves a good clarity of image. In preferred embodiments, the image forming device is generally horizontal and transparcnt panel is at 45 degrees to the horizontal. The image forming device may be positioned above the transparent panel. In this way, a wide viewing angle from the sides may be achieved by suitably sizing and positioning of the panel and image forming device.

Preferably, the display comprises a frame for supporting the transparent panel and/or the image forming device, where the transparent panel is visible on all sides at the front of the display to an angle of at least 90 degrees. More preferably the panel is visible to at least 120 degrees. Preferably the frame does not extend beyond the front of the transparent panel at the sides to allow the surface to be seen from a wide angle.

Preferably the frame does not extend beyond the rear of the transparent panel at the sides so that the viewer can see through the display around the periphery of the imagc to see the background, so that the image appears to be floating in space, i.e. to achieve a virtual hologram effect. Alternatively or additionally, transparent frame members may be used at the sides of the panel to avoid impinging on the display of the image. Alternatively, the transparent panel and/or the image forming device may be suspended by cables or similar ties to avoid the need for a large frame.

Preferably, in the case that the image forming device is a 2D device, the image forming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2000 cd!m2 and in the case that the image forming device is a 3D device, the image forming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2500 cd/rn2. These preferred parameters achieve a good visual display in high ambient light conditions.

In embodiments, the display is used for displaying advertising or promotional materials or other message delivery.

It will be appreciated that any features expressed herein as being provided "in one example" or as being "preferable" may be provided in combination with any one or more other such features together with any one or more of the aspects of the present invention.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure I shows a perspective view of an example of a display according to an embodiment of the present invention; l0 Figure 2 shows a schematic view from thc sidc of the display of Figure 1; Figure 3 shows a schematic view from the front of the display of Figure I; Figure 4 shows a cross section of the glass of the display of Figure 1; An example of the present method will now be described with reference to Figure 1 which illustrates an example of a display 10 according to an embodiment of the present invention. The display 10 comprises a framework 20, a transparent panel, in this example a glass panel 30, and an image forming device 40.

The framework 20 can be any suitable structure for holding the glass panel 30 and the image forming device 40 in position. In this example, the framework 20 comprises a base 21, side members 22 for holding the glass panel 30, a frame 23 for holding the image forming device 40. The display 10 in this example is free standing and approximately 2 meters tall, 1 meter in width and 1.8 meters in length. As will be appreciated from the following description, practically any size or dimensions are possible.

A video or static image is delivered from the image forming device 40 at top of the structure onto the front surface of the glass panel 30. The glass panel 30 has a semi minored finish which reflects the image from the image forming device 40 to a view positioned in front of the display 10. The image forming device 40 can be for example a standard TV monitor, or similar. In theory any image forming device 40 could be used to create the image. Preferably though the image forming device 40 nccds to meet the resolution and brightness criteria set out below. Currently LCD panels are a preferred choice for the image forming device 40, but it is anticipated that other technologies will become possible as they develop. For example, a projector could be used, but at the present time a suitable projector would be too big and expensive to be a preferred solution. There are also several 3D image technologies currently available. In any case, the transparent panel does not need to be adjusted to work with each variant. The image forming device 40 is preferably high intensity. For 2D images, a 2D output panel device is used preferably having a minimum screen resolution of 2 million pixels with a brightness no less than 2000 cdlm2. For 3D images, a 3D output panel device is used preferably having a minimum screen resolution of 2 million pixels with a brightness no less than 2500 cd!m2.

The glass panel 30 can be a single sheet of glass or a laminate of two or more sheets of glass. Preferably mineral glass is used for the sheets of glass. Preferably the glass panel 30 is between 4mm up to 10mm in overall thickness. The glass is preferably thermally tempered (or toughened) safcty glass or a laminated safety glass so the display can be used safely in public places. As mentioned above, a glass panel 30 is the preferred choice for implementing the transparent panel for reflecting the image, but nonetheless other options may be used in certain embodiments, for example transparent plastics or films.

Figure 4 shows in cross section an example of a suitable laminated glass panel 30 where two sheets 31,33 of low iron glass each having a thickness of 4mm are laminated together with a 0.76mm Polyvinyl butyral (or PVB) interlayer 32. As is known per se, PVB is a resin used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. The glass panel 30 has low absorption losses and is extremely homogenous with respect to reflection (shown by arrow 36) and transmission (shown by arrow 37).

The front and rear surfaces 34,35 of the glass panel 30 have optical interference coating layers that have precisely defined states of reflection and transmission.

The front surface 34 ofthe glass panel 30 has a semi-reflective coating 36 to achieve a semi mirror finish. The semi-reflective coating 36 preferably has a Luminous reflectance (Pva) of 36% + 5%. The semi-reflective coating 36 also preferably has a Luminous transmiftance (Tva) of 59% + 5%. This coating 36 is provided so that when an image is delivered to the surface of the glass, high ambient lighting does not wash out the image projected to the viewer. At the same time, the glass panel 30 is see-thmugh to the viewer in areas where the image is not incident on the glass so the background can be seen through the display tO. The semi-reflective coating 36 is the determining factor in both reflectance and transmittance as it reflects some of the light and lets the remainder pass through the rest of the glass panel 30. This is not a perfect process and there are some losses, which is why the two % values do not add up to 100%.

Titanium is a preferred coating to achieve a semi-reflective coating 36 on the front surface 34. The glass 30 is masked on one side and then dipped into a vat to provide an even coating across one surface of the glass 30. Other types of reflective coating and method of applying them to glass substrates are known and it is expected that other suitable choices to achieve the reflective coating could be made within the scope of the invention.

The rear surface 35 of the glass panel 30 has been treated with an anti-reflective coating 37. Various options to achieve an anti-reflective coating are known per se. This coating 37 prevents a double image or ghosting being presented to the viewer. In other words, this stops the image partially travelling through the glass panel 30 and reflecting back from the second sheet of glass, so that only the image reflected from the front edge of the glass is seen by the viewer.

Using a semi-reflective reflective coating 36 having a Luminous reflectance (Pva) of 36% + 5% and Luminous transmittance (Na) of 59% + 5% and an anti-reflective coating, thc glass panel 30 delivers both a particularly high quality 2D and 3D images without any ghosting compared with other choices. This combination is uniquely bencficial over prior art techniques. Other coatings outside the range specified will work to some extent, but will not deliver an image able to be seen so well in high ambient light.

A unique holographic illusion can thus be createdby reflecting a specially produced movie or image onto the glass panel 30. For the viewer, looking at the front of the display 10, the glass panel 30 simply merges with the surrounding foreground and background such that the reflected image 50 appears to be in mid air, i.e. a virtual hologram, thus creating a realistic illusion in a real-life setting. In other words, referring to the side view schematic ofthe display 10 shown by Figure 2, the view sees the reflected image 50 from the image forming device 40 superimposed on the view of the background SI which passes through the glass panel 30 outside the periphery of the reflected image 50. In a prcfclTcd usc, the image displaycd is an object without a background, so that when displayed the object appears to be floating in space against whatever background there is behind the display 10, thus achieving a virtual hologram effect for the viewer. The image 50 is only seen on the front side 34 of the glass panel 30, i.e. from the reverse side 35 no image is seen. This can be useful, as there may be situations where it is desirable to see through the display 10 from the back unimpeded.

Also, as will be appreciated, if the viewer could see the content from the rear ofthe display 10, it would appear the wrong way round, and therefore not convey the message correctly and give a detrimental display of the content/brand/advert, etc. The display 10 is thus able to deliver 2D and 3D, virtual holographic, still and moving video images onto a range of receiving substrates of any size and proportions.

The combination ofthe semi mirrored coating, applied at the correct thickness, and the intensity of the output from the image forming device 40 that delivers an image able to be viewed effectively in high ambient indoor and outdoor lighting conditions without any protection or masking of the screen delivery substrate. Images will appear in open space in fUll colour. The 3D images can be clearly seen by the viewer without the need for special eyewear, in any lighting conditions. Screen images can be manipulated by means of external devices through viewer interaction.

By laminating two sheets of glass together, the glass can be fttsed into a single product thereby turning the glass panel 30 into a safety glass. This is an important consideration where the display 10 is to be used in a public sefting. This is also important where a large display is required, needing a panel of glass 30 with a large area. Turning the glass into safety glass, with an overall thickness of 10mm + 6mm also gives the glass much more strength, which allows the glass to be used with minimum additional structural members for support. In a preferred embodiment, the glass panel may be made strong enough to support some or all of its own weight and/or that of the image forming device. This allows the supporting structure 20 around the panel 30 to be minimised or eliminated.

As mentioned above, the glass panel 30 is preferably relatively thick, which introduces the possible problem of double images/ghosting being formed. To eliminate or at least substantially reduce this possibility, the anti-reflective coating 37 is provided on the rear surface 35 of the glass panel 30. Prior art displays using the Pepper's Ghost' principle usually use a single sheet of glass or some other thin substrate that does not suffer from appreciable ghosting.

Referring to the front schematic view of the display of Figure 3, preferably the display can be viewed from a wide range of viewing angles 61 relative to the front centreline 60 ofthe display 10. Preferably the display 10 has little or no structure at the sides to allow the images on the glass surface from a wide angle approaching the display from left or right. Alternatively, the side supports 22 of the frame 20 may be made from transparent material such as Perspex to increase the viewing angle. Preferably, there is no structure or no non-transparent structure in front of the glass panel 30 at the sides so that the front surface 34 on \vhich the image is displayed can be viewed from approaching degrees, i.e. 90 degrees left and right ofthe centreline 60. As will be appreciated, as the angle to the centreline 60 increases, the projected width of the glass panel visible to the view is reduced. This means that the fUll image 50 may not be visible at extreme angles, unless the glass panel 30 is very large compared to the size of the image 50.

Thus, the actual viewable angle may in practice be somewhat less than 180 degrees. In general, preferred embodiments have a viewing angle of at least 90 degrees, and preferably at least 120 degrees. Similarly, it is preferred that there is no structure or no non-transparent structure to the rear of the glass panel 30 at the sides so that the viewer's view of the background is not restricted from the sides. l0

The glass panel 30 can be of any dimension. A standard shcet of thc glass is 3000 mm x 1770mm in size. However if a larger panel 30 is required, plural sheets of glass can be positioned together, abutting each other thereby making a glass panel 30 with a much larger areas on which to deliver images 50.

The configuration between the glass panel 30 and image forming device 40 is preferably at an angle of about 45 degrees. This will dcliver an evenly distributed image across the glass surface enhancing clarity and legibility of the image seen by the viewer.

However, other angles, for example 45 + 10 degrees will work to some extent, but are less prefcrred because the imagc will lose intensity at the extreme edge of the glass and will not be seen as part of the overall image.

The image forming device 40 is preferably positioned above the glass panel 30.

Howevcr, other positions of the imagc forming device 40 are possible. For example the image forming device 40 can be positioned to project the image from underneath, or from the side, etc, with the glass panel 30 being orientated appropriately to maintain the viewing angle.

The display 10 could for example be suspended, e.g. by cables or similar ties, from a ceiling or other structure, or resting on the floor or some other structure.

This technology can be employed in a wide range of commercial applications, not least ibr advertising or promotions, employed in retail shop windows and stores, shopping centres, information displays in airports as well as many other applications.

Thc displays 10 can be employed free standing, elevated and suspended.

The technology can also be used to deliver Augmented Reality applications.

Augmented Reality is the technique of overlaying graphics on a real-world image so the graphics are brought to life. Most of the techniques today are generated using a compute?s webeam. By holding a 2D flat or shaped printed image to a web cam, the experience begins.

Embodiments of the present invention have been described with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope ofthe present invention.

Claims

Claims 1. A display comprising: a transparent panel having a front surface and a rear surface; a image forming device arranged to project an image onto the front surface of the transparent panel, the transparent panel being inclined relative to the projected image, such that in use for a viewer looking from the front of the display, the image is superimposed onto the background visible through the transparent panel, the transparent panel having a semi-reflective coating on the front surface, and an anti-reflective coating on the rear surface.
2. A display according to claim I, wherein the semi-reflective coating has a Luminous reflectance (Pva) of 36% + 5% and a Luminous transmittance (Tva) of 59% + 5%.
3. A display according to claim I or claim 2, wherein the transparent panel is a glass pancl.
4. A display according to claim 3, wherein the transparent panel is a thermally tempered or laminated safety glass.
5. A display according to any of claims ito 4, wherein the transparent panel is at least 4mm thick.
6. A display according to any of claims 1 to 5, wherein the transparent panel is at 45 + 10 degrees from the image forming device.
7. A display according to any of claims I to 6, comprising a frame for supporting the panel and/or the transparent panel, where the transparent panel is visible on all sides at the front of the display to an angle of at least 90 degrees.
8. A display according to any of claims ito 7, wherein in the case that the image forming device is a 2D device, the image forming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2000 cd/m2 and in the case that the image foirning device is a 3D device, the image forming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2500 cd/m2.
9. A method of displaying an image using a display comprising a transparent panel having a front surface and a rear surface a image forming device, the method comprising projecting an image onto the front surface of the transparent panel, the transparent panel being inclined relative to the projected image, such that for a viewer looking from the front of the display, the image is superimposed onto the background visible through the transparent panel, wherein the transparent panel has a semi-reflective coating on the front surface, and an anti-reflective coating on the rear surface.tO. A method according to claim 9, wherein the semi-reflective coating has a Luminous reflectance (Pva) of 36% ± 5% and Luminous transmittance (Tva) of 59% ± 5%.11. A method according to claim 9 or claim 10, wherein the transparent panel is a glass panel.12. A method according to claim 11, wherein the transparent panel is a thermally tempered or laminated safety glass.13. A method according to any of claims 9 to 12, wherein the transparent panel is at least 4mm thick.14. A method according to any of claims 9 to 13, wherein where the transparent panel is at 45 + 10 degrees from the image forming device.15. A method according to any of claims 9 to 14, wherein comprising a frame ibr supporting the panel and/or the transparent panel, where the transparent panel is visible on all sides at the front of the device to an angle of at least 90 degrees.16. A method according to any of claims 9 to 15, wherein in the case that the image forming device is a 20 device, the image forming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2000 cd/m2 and in the case that the image Ibiming device is a 3D device, the image fbrming device has a minimum screen resolution of 2 million pixels with a brightness no less than 2500 ai/m2. I017. A method acconling to any of claims 9 to 16, wherein the display is used for displaying advertising or promotional materials or other message delivery.