Stereoscopic display system

Abstract: Stereoscopic effects can be created by binocular parallax. Known stereoscopic display systems show pseudoscopic effects in outer areas of the image viewing position and the viewing position is fixed. To avoid such pseudoscopic effects and/or to change the viewing position stereoscopic displays using parallax barriers with variable pitch length, moving barriers parallel to the display plane, and a polarizing device forming polarized light together with polarizing prisms are provided.

Description: The invention relates to a stereoscopic display system, which generates the impression of a stereoscopic image by binocular parallax. Such a system uses a display comprising a pixel plane, wherein right and left images are depicted either alternating for the whole screen or alternating between adjacent pixels. Known stereoscopic display systems use special glasses, for example red and blue filter glasses, LCD shutter goggles or polarizing filter glasses. Other known prior stereoscopic displays use a parallax barrier with a fixed slit pitch or use a lenticular lens sheet. All these known stereoscopic display systems have the disadvantages that they show pseudoscopic images in the outer areas of the viewing area and/or that the viewing position is fixed due to the fixed geometry of the system. It has also been proposed in EP-A-0540137, a stereoscopic display system having a display comprising a pixel plane for alternating displaying right and left images and a parallax barrier made of barrier strips, which are arranged in front of the display. In this application it is mentioned that the distance or pitch between adjacent barrier strips is variable. It is therefore an object of the invention to provide a stereoscopic display system which overcomes the drawbacks of the prior art mentioned above. This object is solved by the subject matter according to claim 1. So, in an embodiment of a stereoscopic display system with a display comprising a pixel plane for displaying right and left images, a polarizing device, which can switch between two states of polarization, is arranged in front of the display followed by a polarizing prism sheet comprising a plurality of prisms, which are arranged one prism next to the other, so that a column type prism sheet is formed, wherein one polarization is deflected by the prisms in a first direction, and the other polarization is deflected in a second direction. Preferably in such stereoscopic display system each pixel column of the display corresponds to one polarizing prism of the polarizing prism sheet. In other words, each polarizing prisms covers one pixel column. Further the stereoscopic display system comprises a polarizing device controller and a switching means to switch between left and right images, both of which are controlled by a common timing signal. To further lower the crosstalk of left and right image rays, the shape of each polarizing prism of the polarizing prism of the polarizing prism sheet differs from one another. To use a more wide display, it is further possible that each outer prism of the polarizing prism sheet overlaps the adjacent inner prism. With the above described embodiments of the invention it is possible to adjust the viewing distance and/or to suppress pseudoscopic images in the outer areas of the viewing area. Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a stereoscopic display system, wherein a polarizing device and polarizing prism sheet is used for the stereoscopic display system, Figure 2 is a cross section through the system according to Figure 1, Figure 3 is a cross section through a stereoscopic display system according to Figure 1, wherein the shapes of the prisms differ from each other, Figure 4 is an embodiment of the polarizing stereoscopic display system, wherein the prisms overlap each other, and Figure 5 is a schematic showing the principles of a stereoscopic display system using a parallax barrier system. Figure 5 shows the basic principles of a parallax barrier system, comprising a display 1, which forms an image plane or pixel plane comprising alternating left image pixels 2 and right image pixels 3. In this example the image is a so-called mixed strip image, wherein pixels for the left and right image form vertical rows, respectively. As it is clear from the depicted rays of the respective pixels, right image pixels 3 are blocked by the parallax barrier 4 for their way to the left eye, wherein left image pixels 2 are blocked for the right eye. Further it is clear from Fig. 5, that using a parallax barrier 4 with a fixed pitch between the barrier strips results in a fixed viewing distance for the left and right eye LE, RE. Figure 1 shows a stereoscopic display system using polarized light for creating the stereoscopic effect. On top of a flat panel display 1 consisting of pixels 21 a polarizing defice 42 is provided, which polarizes the light emanating from the pixels 21. On top of this polarizing device 42 rows of polarizing prisms 43 are provided, so that the bottom of each prism 43 covers one row of pixels 21. These polarizing prisms 43 form a polarizing prism sheet 44. The polarizing device 44 is controlled by a controller 45, whereas the display 1 is controlled by a display controller 46. Both controllers 45, 46 are timed by a common timing signal 47. Figure 2 shows the stereoscopic display system according to Figure I in cross section. The flat panel display 1 is overlaid by the polarizing device 42, on top of which a polarizing prism sheet 44 consisting of rows of prisms 43 rests. In Figure 2 the left eye LE sees only the right side surface 48 of the polarizing prisms 43, whereas the right eye RE only sees the left side surface 49 of the polarizing prism. When the polarization direction of the polarizing device 42 is parallel to the polarization direction of the right side surface 48 of the polarizing prism 43, the flat panel display displays left eye image. During this time the rays of the flat panel display 1 are not able to project from the left side surface 49 of the polarizing prism 43, because the polarization direction of the polarizing device 42 is perpendicular to the polarization direction of the left side surface of the polarizing prism 43. After a moment the polarization direction of the polarizing device 42 is changed to the other direction and it is parallel to polarizing direction of the left side surface 49 of the polarizing prism 43. At this time the flat panel display displays right eye image. During this time, rays of the flat panel display are not able to project from right side surface 48 of the polarizing prism. After a moment the polarizing direction of the polarizing device 42 is changed again to the first polarization direction. This operation is continuously repeated. Therefore the display I displays right eye image and left eye image alternately, so that the right eye sees only right image and the left sees only left image in a time sharing manner. Therefore, if the above operation is fast enough, a stereoscopic image by the effect of after image and binocular parallax is created. Figure 3 shows a cross section through a stereoscopic display using polarized light, wherein the shapes of the polarizing prisms 43 of the polarizing prism sheet 44 differ from each other. The height of the prisms 42 decrease from the outer areas to the middle of the display 1, i.e., an "outer prism is higher than its adjacent "inner" prism. With such an arrangement the cross talk of left image ray and right image ray is decreased in comparison to the prism shape according to Figure 2. Figure 4 shows another embodiment of the stereoscopic display system using polarized light, wherein the shapes of the polarizing prisms is different as in the embodiment of Figure 3, but further the prisms overhang each other, seen from the outside to the middle of the display 1, i.e. an "outer" prism overlaps an adjacent inner prism. With such an arrangement and shape it is possible to use a wider display than the interpupil length. Reference number list LE - Left Eye RE - Right Eye 1 - Display 2 - left image pixel 3 - right image pixel 4 - parallax barrier 42 - polarizing device 43 - polarizing prism 44 - polarizing prism sheet 45 - controller 46 - display controller 47 - timing signal

Claims: Stereoscopic display system with a display (1) comprising a pixel plane for displaying right and left images, characterized in that a polarizing device (42), which can switch between two states of polarization is arranged in front of the display (1) followed by a polarizing prism sheet (44) comprising a plurality of prisms (43), which are arranged one prism (43) next to the other, so that a column type prism sheet (44) is formed, so that one polarization is deflected by the prisms (43) in a first direction, and the other polarization is deflected in a second direction. Stereoscopic display system according to claim 1 in which each pixel column of the display (1) corresponds to one polarizing prism (43) of the polarizing prism sheet (44). Stereoscopic display system according to claim 1 or 2, wherein the system comprises a polarizing device controller (45) and a display controller (46) to switch between left and right images, both of which are controlled by a common timing signal. Stereoscopic display system according to one of the claims 1 to 3, wherein each of said polarizing prisms (43) of the polarizing prism sheet (44) has a shape which differs from one to another. Stereoscopic display system according to one of the claims 1 to 4, wherein each outer prism (43) of the polarizing prism sheet (44) overhangs the adjacent inner prism (43).

Inventors: CHIKAZAWA YOSHIHARU, CHIKAZAWA, YOSHIHARU
Applicants: THOMSON MULTIMEDIA SA, THOMSON MULTIMEDIA
Application year: 1996
Main classification: G02B27
IPC codes: H04N13, G02B27, G02F1