AUTOSTEREOSCOPIC PROJECTION SCREEN

An autostereoscopic projection screen including a projection area and a control, wherein the projection area includes micromirrors, wherein the control is adapted to adjust orientation of the micromirrors such that the micromirrors can reflect light emitted by an image source into directions creating an image in each direction at a viewing distance such that each image can only be seen by one eye of a viewer located in said direction at said viewing distance, and wherein two images are created at a first viewing distance and spaced apart such that a viewer in the first viewing distance can see one of the two images with a first eye only and the other of the two images with a second eye only, wherein the viewer has the impression of seeing the two images simultaneously. The invention further relates to a method and a system for autostereoscopic projection.

The Figures show only schematic representations of exemplary embodiments of the present invention and have not been drawn to scale.

DETAILED DESCRIPTION

InFIG. 1the general principle of an autostereoscopic projection screen1according to one preferred embodiment of the present invention is outlined. Being merely a schematic representation, the projection screen1comprises only two micromirrors3,5forming a first and a second subset7,9. The orientation of the micromirrors3,5can be adjusted independently of one another by a control means10. In this schematic representation the term orientation refers to a tilt of the micromirrors3,5with respect to a common projection plane11.

The micromirrors3,5are attached to the projection plane11by a thin connection layer12. The micromirrors3,5of the embodiment shown inFIG. 1can only be tilted in a direction away from the projection plane11about the respective connection layer12i.e. micromirror3is tilted towards micromirror5and vice versa. Tilting the micromirrors3,5is, in other words, restricted to one direction. This limits the direction into which each subset7,9of micromirrors3,5may reflect light.

InFIG. 1the orientation of micromirror3of the first subset5has been adjusted by the control means such that light13emitted by an image source14is reflected into a first direction15. The reflected light creates a first image in a viewing distance. Said first image can only be seen by with a first eye17of a viewer in the viewing distance.

The light21emitted by the image source illuminates micromirror5belonging to the second subset9. The orientation of the micromirror5of the second subset9has been adjusted to reflect the light21into a second direction23such that the reflected light creates a second image that can only be seen with a second eye25of a viewer.

The images created by the first and second subset7,9of micromirrors do not overlap at the viewing distance and are spaced apart such that a viewer can view the first image with one eye17and the second image with another eye25. Hence, the projection screen1according to the present invention allows for a front projection of two different images into the eyes of a viewer without requiring any kind of glasses or other headgear. Combined with a modern projector it offers a lightweight solution for the generation of three-dimensional depth perception in images projected on a plane surface.

InFIG. 1it is well conceivable that the orientation of micromirror3of the first subset7can be adjusted differently using the control means10e.g. the light13could be reflected into a direction such that the image can be seen with the second eye25only. However, in that case the control means10would have adjusted the orientation of the second subset9of micromirrors such that the light21is reflected in a direction such that the image created by it can be seen with the first eye17only.

FIG. 2shows part of a row27of micromirrors29,31of a first exemplary embodiment of a projection screen according to the present invention. Only those features of this embodiment will be elaborated in more detail that differ from the features inFIG. 1. The micromirrors29,31are arranged on a regular grid. Hence, every micromirror corresponds to another column. In other words, all micromirrors29,31can be identified by the same row number but by a different column number. The micromirrors29,31are arranged in an alternating manner in two different subsets i.e. adjacent micromirrors29,31on the same row belong to different subsets. The first subset comprises all micromirrors29; the second subset comprises all micromirrors31.

The orientation of the micromirrors29of the first subset has been adjusted by a control means (not shown) such that light33emitted by an image source (not shown) and illuminating the first subset of micromirrors29is reflected into a first direction35. The reflected light creates a first image in a viewing distance from the screen that a viewer can see with one eye only.

The control means has been used to adjust the orientation of the second subset of micromirrors31into a different position. Light37emitted by image source also illuminates the second subset of micromirrors31but is reflected into another direction39. A viewer located in the viewing distance at this direction39can view the image created by the light reflected by the second subset of micromirrors31with one eye only.

The projection screen of the second exemplary embodiment is especially advantageous as it allows for a high spatial resolution in the direction of the row27. It should be noted thatFIG. 2could as well be showing a column of micromirrors.

FIG. 3shows part of a row40of micromirrors41,43of a second embodiment of a projection screen according to the present invention. As inFIG. 2, the micromirrors are arranged on a regular grid. The micromirrors41,43are arranged in two subsets. A first group of micromirrors41belongs to a first subset; a second group of micromirrors43belongs to a second subset of micromirrors. In contrast to the first embodiment, each micromirror41,43has at least one neighbouring micromirror41,43that belongs to the same subset. The subsets of micromirrors are formed by clusters41,43of micromirrors41,43. In the exemplary embodiment inFIG. 3at least five consecutive micromirrors41,43along each row40belong to the same subset. The light45,47of an image source illuminates the first subset of micromirrors41and the second subset of micromirrors43.

The second exemplary embodiment of the present invention is advantageous, as the image quality of the images created by the projection screen is less affected by a misalignment of the image source and the projection screen in a direction parallel to the row40. Even if the image source emitting the light45,47would be shifted e.g. by one micromirror along the row40towards the second set of micromirrors43, four out of five micromirrors would still be illuminated correctly.

Along the columns that are perpendicular to the row40the micromirrors could both be arranged in subsets as in the first embodiment or as in the second embodiment. However, it is also conceivable that all micromirrors in one column belong to the same subset i.e. all micromirrors that can be identified by the same column number as one of the micromirrors41belong to the first subset and all micromirrors that can be identified by the same column number as one of the micromirrors43belong to the second subset.

It should further be noted that the number of micromirrors in each cluster does not have to be constant along the row40. It is, for example, possible to have smaller or no clusters of micromirrors in the centre of a projection screen and larger clusters of multiple micromirrors at the edges of the projection screen.

FIG. 4shows a part of a row49of a third exemplary embodiment of a projection screen according to the present invention. The micromirrors51,53,55,57are grouped in clusters51,53,55,57i.e. each micromirror51,53,55,57has at least one adjacent micromirror51,53,55,57in the same row49that belongs to the same subset. However, in contrast to the previous embodiments the micromirrors51,53,55,57are arranged in at least four subsets. Each subset's orientation has been aligned by a control means (not shown) such that it reflects light emitted by the image source into one of four directions thereby creating at least four different images. Each image can only be seen by one eye of a viewer in the viewing distance. Each of the four images is spaced apart from at least one of the other three images such that a viewer in the viewing distance can see one image with a first eye and a second image with a second eye. Hence, a viewer can only see two of the four projected images simultaneously.

A projection screen according to the third exemplary embodiment is advantageous for various reasons. In an exemplary setting the projection screen can be used to display stereoscopic images for two viewers at the same time i.e. a first viewer sees the images created by a first and a second subset of micromirrors and a second viewer sees the images created by a third and a fourth subset of images. Thereby, a single projection screen and a single projector can be used to show different content to two viewers.

In another exemplary setting a projection screen according to the third exemplary embodiment can be used to project multiple views of the same objects under slightly altered angles such that a viewer can view the objects depicted in the projected images under different angles if the projection screen is viewed from different directions. Alternatively, such a setting can be used to allow multiple users to view the same images and reduce the necessity for a viewer to be located in an exact position to view one image with each eye.

FIG. 5shows an exemplary embodiment of a system59for autostereoscopic projection according to the present invention. The system comprises an autostereoscopic projection screen61according to the first exemplary embodiment and an image source67comprising two groups of pixels63,65.

Only one row69of micromirrors71,73of the autostereoscopic projection screen61is shown inFIG. 5. The micromirrors71,73are arranged in a first subset of micromirrors71and a second subset of micromirrors73. A control means75has been adapted to adjust the orientation of the micromirrors71,73.

Each group of pixels63,65emits light77,79that illuminates one subset of micromirrors71,73only i.e. a first group of pixels63emits light illuminating only the first subset of micromirrors71and a second group of pixels65emits light illuminating only the second subset of micromirrors73. In turn, the first subset of micromirrors71is illuminated by the first group of pixels63only and the second subset of micromirrors73is illuminated by the group of pixels65only.

The exemplary embodiment of the system59for autostereoscopic projection is advantageous for the same reasons as the different embodiments of an autostereoscopic projection screen according to the present invention.

In all of the above exemplary embodiments the orientation of the micromirrors does not need to be fixed. It is, for example, advantageously possible to use a system for tracking the eye position of a viewer and adjust the orientation of the micromirrors using the control means such that a first subset of micromirrors always reflects the light emitted by the image source towards the viewers first eye and a second subset of micromirrors always reflects the light emitted by the image source towards the viewers second eye.

Finally,FIGS. 6aand6bshow a second exemplary embodiment of a system81for autostereoscopic projection according to an aspect of the present invention. The system comprises an exemplary embodiment of an autostereoscopic projection screen83according to another aspect of the present invention. The projection screen83comprises a plurality of micromirrors85. The orientation of the micromirrors85can be controlled via a control means87. The system further comprises an image source89that is also connected to the control means87.

The micromirrors of the exemplary embodiment of the autostereoscopic projection screen83are not arranged in subsets. All micromirrors are used in a correlated manner to generate two images at a viewing distance. The images are not created at the same time. Instead they are created in a rapidly alternating fashion such that a viewer at the viewing distance has the impression of seeing the images simultaneously.

FIG. 6ashows the generation or creation of a first image. The image source89emits light91illuminating the micromirrors85. The control means87is adapted to tilt the micromirrors85such that the light is reflected into a first direction such that an image is created in a first viewing distance. The image can only be seen by a first eye93of viewer at the viewing distance. A second image is created by altering the orientation of the micromirrors85as shown inFIG. 6b. Light91emitted by the image source89is reflected into another or a second direction such that a second images is generated at the first viewing distance. The second image can only be seen by a second eye95of a viewer.

The control means87is adapted to alter the orientation of the micromirrors85in rapid succession such that the viewer has the impression of seeing different images with his eyes93,95simultaneously. With the control means87also the image source89is controlled: the micromirrors85are only illuminated while not switching between two orientations, thereby avoiding any blurring of the images. Furthermore, the image projected onto the projection screen83by the image source89can be selected/controlled depending on the orientation of the micromirrors85.

The micromirrors85comprised in the projection screen83can in an exemplary embodiment also be arranged in subsets and/or clusters to provide multiple viewers simultaneously with images. The images seen by each viewer may be the same at a given time. It is, however, also possible to provide different viewers with different images simultaneously such that the viewers can advantageously be provided with different content.

The embodiments of a projection screen83and a system81provide an advantageous solution for projecting autostereoscopic images in settings that are subject to vibrations or wherever an exact alignment of screen83and the image source89is hindered. Correlating the illumination of the micromirrors85as a function of their current orientation can be easily achieved by a coupling of the image source89with the control means87. The coupling can be performed by electronic means and is therefore advantageously independent of any physical stress acting on either the image source89or the projection screen83.