FIELD OF INVENTION The present invention relates to a multi-display system, a projection unit and a method of displaying images. In particular, it relates to a multi-display system, a projection unit and a method of displaying images as electronic wallpaper.

BACKGROUND OF INVENTION Multiple displays may be used for providing an electronic wallpaper. By displaying, for example, one or more photographs or images on multiple displays, a panoramic representation is achieved. A multi-display, i. e. a multiple of coordinated displaying units, displaying in coordination a panoramic scenery is generally disclosed in US patent 6,247, 815. The invention described discloses a workdesk having a panoramic display utilising an edge-blending system as disclosed in US patent 5,136, 390. The edge-blending system encompasses a method of smoothing the brightness of two adjoining overlapping video images produced from two discrete video signals each having a plurality of detail elements (which may comprise a fraction of a pixel or a plurality of pixels) each with a brightness component. The system allows a seamless multiple video image display to appear more consistent and uniform in brightness than a conventional single video display and is therefore useful for multi-displays.

In order to achieve blending of multiple video images to be displayed relative to one another, the system identifies the brightness of each individual image and performs an adjustment or alignment of brightness around the edge areas of the images so as to construct a seamless display. This operation requires real-time handling during display of video signals on a multi-display, thus requiring significant processor means in order to handle the edge- matching in a satisfactory manner.

In addition, the workdesk and the system disclosed in the above-mentioned US patents, which are hereby incorporated by reference, utilise tremendous calculation powers for simply providing a wallpaper or background. Furthermore, during the processing of the edge areas of the images, the system performs adjustment to any number of pixels defined as edge areas. Hence, the system employs a non-discretionary calculation and adjustment

causing an edge-matching irrespective of whether some of the edge area, in fact, should be kept un-adjusted.

OBJECT AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the problem of generating an electronic wallpaper or background without performing a non-discretionary calculation on pixel information stored in edge areas of images used for said electronic wallpaper.

It is a further object of the present invention to provide a first presentation of an electronic wallpaper and a second presentation incorporated in the electronic wallpaper.

A particular advantage of the present invention is the generation of a simple and inexpensive panoramic view based on very little information.

A particular feature of the present invention is the provision of enabling one or more images to be overlaid e. g. so as to achieve an electronic wallpaper as background and additional images as foreground.

The above objects, advantages and features together with numerous other objects, advantages and features, which will become evident from the detailed description below, is obtained according to a first aspect of the present invention by a multi-display system for generating an electronic wallpaper from a first image and for displaying said electronic wallpaper on a display surface, and characterized in that said multi-display system comprises a device for displaying said electronic wallpaper on said display surface and is adapted to mirror said first image to a second image and align said second image next to said first image, thereby generating said electronic wallpaper.

The device of the multi-display system according to the first aspect of the present invention provides an electronic wallpaper utilising a first image and reproducing the first image mirrored to form a second image. By aligning the first and the second image next to one another along the mirroring axis, a seamless and contiguous panoramic representation may be generated for display on a display surface.

The device according to the first aspect of the present invention may be adapted to mirror the first image across a vertical mirror line and/or a horizontal mirror line.

Hence, the final electronic wallpaper may be generated by a first mirroring operation being vertical and a second mirroring operation being horizontal, thus providing a"chessboard"of first and second images constituting the electronic wallpaper. Thus, the device may be

adapted to generate an electronic wallpaper from a series of copies of the first image each aligned next to a copy of the second image.

The first image according to the first aspect of the present invention may be aligned with the second image at the vertical mirror line and/or the horizontal mirror line.

In addition to displaying the electronic wallpaper, the device according to the first aspect of the present invention may be adapted to display a window overlaying the electronic wallpaper. The window may comprise a text, series of texts, pictures, series of pictures, videos, sequences of videos, audio tracks or series of audio tracks or any combination thereof. This feature presents an excellent tool for first generating an appropriate electronic wallpaper and still utilise the device for displaying further information on the display surface. The information contained in the window may be any information provided from various sources e. g. DVD players, video players, televisions, any household electronics or computer networks such as the Internet, or telecommunication networks such as television networks or mobile or ordinary telephone networks. Thus, the operator of a device may open as many windows as required, each window containing information from various sources.

The device according to the first aspect of the present invention may have an input adapted to receive the first image as a stream of data defining a start and an end of stream, a memory adapted to store the stream of data, and a processor adapted to read the stream of data from the start, so as to provide the first image, and from the end, so as to provide the second image. The first image and the second image may be obtained by providing a line memory for an input stream, which line memory may be adapted to read in both directions.

The device according to the first aspect of the present invention may comprise a projection unit for displaying the electronic wallpaper on the display surface, or a cathode ray tube (CRT), a liquid crystal display (LCD), a display based on light-emitting diodes (LED) or polymer light-emitting diodes (poly LED), or a plasma display panel displaying the electronic wallpaper on the incorporated display surface.

The above objects, advantages and features together with numerous other objects, advantages and features, which will become evident from the detailed description below, is obtained according to a second aspect of the present invention by a projection unit for projecting an electronic wallpaper on a display surface and being adapted to mirror a first image to a second image and align said second image next to said first image, thereby generating said electronic wallpaper.

The projection unit according to the second aspect of the present invention may incorporate any features of the multi-display system according to the first aspect of the present invention.

The projection unit is particular advantageous as a multi-display unit because the projection unit provides an electronic wallpaper created on the basis of a first image, which is multiplied alternately as mirrored and un-mirrored and at the same time enables an operator to open windows overlaying the electronic wallpaper, which windows may contain a wide variety of types of information.

The above objects, advantages and features together with numerous other objects, advantages and features, which will become evident from the detailed description below, is obtained according to a third aspect of the present invention by a method of generating an electronic wallpaper from a first image, the method comprising the steps of a) generating a mirror image of said first image; b) displaying said first image and said mirror image next to each other, thereby generating an electronic wallpaper.

The method according to the third aspect of the present invention provides an electronic wallpaper which is larger than the first image, while retaining a high resolution, and further avoids visual boundaries. This is preferably obtained by displaying the image and the mirror image in close proximity.

Similarly to the multi-display system according to the first aspect of the method according to the third aspect, the mirroring operation may be performed as a horizontal and/or vertical mirror image. That is, the mirror image of the first image may be e. g. under, above or besides the first image. For example, if a mirror image is created with respect to a vertical line, the mirror image may be displayed beside the first image. The first image and the mirror image of the first image are displayed dimensionally alternately next to each other.

The method according to the third aspect of the present invention may incorporate any features of the multi-display system according to the first aspect of the present invention and/or any features according to the second aspect of the present invention.

In this context, the term image is to be construed as a frame of a video sequence, a still photograph or still digital representation or any combination thereof.

In this context the indefinite article"a"or"an"is to be construed as"one","a single", "one or more", or"at least one".

BRIEF DESCRIPTION OF THE DRAWINGS The above, as well as additional features and advantages of the present invention, will be better understood from the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, wherein: Figure 1 is a three-dimensional view of a multi-display system according to a first embodiment of the present invention; and Figure 2 is a two-dimensional view of a multi-display system according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 shows a multi-display system according to a first embodiment of the present invention, which multi-display system is denoted in its entirety by reference numeral 10. The multi-display system 10 comprises a projection unit 12, such as a LCD front projection unit, projecting an electronic wallpaper 14 on a display surface 16, such as a white wall or a projector screen. In an alternative embodiment of the present invention, the projection unit 12 and the display surface 16 are substituted by a display unit such as a cathode ray tube (CRT) or liquid crystal display (LCD) monitor or TV.

The electronic wallpaper 14 comprises a first image 18 projected by the projection unit 12 on a first section 20 of the display surface 16, which projection is visualised in Figure 1 by dotted lines 22. The electronic wallpaper 14 further comprises a second image 24 projected by the projection unit 12 on a second section 26 of the display surface 16, which projection is visualised in Figure 1 by broken lines 28.

The second image 24 is generated from the first image 18 by the multi-display system 10 utilising a mirroring operation. The first image 18 is mirrored across a mirror line 30 to the second image 24, thereby obtaining the seamless contiguous electronic wallpaper 14. By mirroring the first image 18 to the second image 24, the interface or border between the first and second image 18,24 becomes smooth, thus achieving an electronic wallpaper having a clean transition between the first and second image 18,24.

In addition to providing the electronic wallpaper 14, the multi-display system 10 is capable of further projecting a text box 32 and/or an additional graphics window 34, which overlay the electronic wallpaper 14. The projection of the additional graphics window 34 is illustrated in Figure 1 by solid lines 36. The multi-display system 10 does not perform the mirroring operation of the overlaying text box 32 or overlaying graphics window 34, and

therefore the text 32, the graphics window 34 or a combination thereof is projected un- mirrored.

Obviously, the text box 32 and the additional window 34 shown in Figure 1 are entirely illustrative examples of the present invention. The multi-display system 10 may project any number of text boxes or graphics windows overlaying the electronic wallpaper 14.

Figure 2 shows a multi-display system according to a second embodiment of the present invention, which multi-display system is denoted in its entirety by reference numeral 40. For simplicity, the projection unit is not shown per se in Figure 2. However, it should be understood that some of the elements shown in Figure 2 are projections of a projection unit as described with reference to Figure 1.

Similarly as the multi-display system 10, described with reference to Figure 1, the multi-display system 40 comprises an electronic wallpaper 42 projected on a display surface 44. The electronic wallpaper 42 comprises a first image 46 projected on a first section 48 and on a second section 50 of the display surface 44, and comprises a second image 52 projected on a third section 54 and on a fourth section 56 of the display surface 44. As described with reference to Figure 1, the second image 52 is the result of a mirroring operation performed on the first image 46. The first image 46 is mirrored across mirroring lines 58.

Figure 2 shows a series of four images aligned next to one another for illustrative purposes only. A series of first and second images 46,52 aligned next to one another may comprise any number of first and second images alternately placed next to one another, thus providing a seamless and contiguous electronic wallpaper having any desired number of images in the range from two to several million.

In addition, the series may extend horizontally, as shown in Figures 1 and 2, as well as vertically, thus providing a multi-display system 10,40 enabling fulfillment of customer requirements.

The multi-display system 40 may further provide a projection of a text box 60 and/or a graphics window 62 overlaying the electronic wallpaper 42. The multi-display system 40 projects the text box 60 and/or the graphics window 62 without performing a mirroring operation. The text box 60 and the graphics box 62 are thus projected in an un- mirrored copy on the display surface 44.

As described with reference to Figure 1, the text box 60 and the additional window 62 shown in Figure 2 are entirely illustrative examples of the present invention. The multi-display system 40 may project any number of text boxes or graphics windows overlaying the electronic wallpaper 42.