Optical: systems and elements – Stereoscopic – With right and left channel discriminator
Reexamination Certificate
2000-02-10
2002-08-20
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Stereoscopic
With right and left channel discriminator
C359S463000, C359S462000, C359S483010, C359S494010, C359S490020, C359S464000, C349S015000, C349S046000, C349S096000, C349S098000, C348S051000, C348S057000, C348S058000, C348S059000
Reexamination Certificate
active
06437915
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a passive polarisation modulating optical element and to an optical device including such an element. The present invention also relates to a method of making a passive polarisation modulating optical element. Such an element may be used in three dimensional (3D) displays, for instance of the autostereoscopic type. Such displays may be used in games apparatuses, computer monitors, laptop displays, work stations and professional imaging, for instance for medical, design or architectural use.
The present invention relates to a parallax barrier and to a display. Such displays may be used as switchable two dimensional (2D)/three dimensional (3D) displays and may be used in games apparatuses, computer monitor, lap top displays, work stations and professional imaging, for instance for medical, design or architectural use.
DISCUSSION OF THE RELATED ART
In normal vision, the two human eyes perceive views of the world from two different perspectives due to their spatial separation within the head. These two perspectives are then used by the brain to assess the distance to various objects in a scene. In order to provide a display which effectively displays a 3D image, it is necessary to recreate this situation and supply a so-called “stereoscopic pair” of images, one to each eye of an observer.
Most 3D displays may be classified into two types depending on the technique used to supply the different views to the eyes. Stereoscopic displays typically display both of the images over a wide viewing area. However, each of the views is eIicuded, fur instance by colour, polarisation state or time of display, so that a filter system of glasse worn by the observer attempts to separate the views to let each eye see only the view that is intended for it.
Autostereoscopic displays require no viewing aids to be worn by the observer. Instead, the two views are only visible from defined regions of space. The region of space in which an image is visible across the whole of the display active area is termed a “viewing region”. If the observer is situated such that one eye is in one viewing region and the other eye is in the other viewing region, then a correct set of views is seen and a 3D image is perceived.
For autostereoscopic displays of the “flat panel” type, the viewing regions are formed by a combination of the picture element (pixel) structure of the display and an optical element, generically termed a parallax optic. An example of such an optic is a parallax barrier. This element is a screen with vertical transmissive slits separated by opaque regions. A display of this type is illustrated in
FIG. 1
of the accompanying drawings. A spatial light modulator (SLM)
1
of the liquid crystal type comprises glass substates
2
between which are disposed a liquid crystal layer together with associated electrodes and alignment layers. A backlight
3
illuminates the SLM
1
from behind and a parallax barrier
4
is disposed on the front surface of the SLM
1
.
The SLM
1
comprises a 2D array of pixel apertures with the pixels arranged as columns as shown at
5
separated by gaps
6
. The parallax barrier
4
has vertically extending slits
7
with a horizontal pitch close to an integer multiple of the horizontal pitch of the pixel columns
5
so that groups of columns of pixels are associated with each slit. As illustrated in
FIG. 1
, three pixel columns labelled columns
1
,
2
and
3
are associated with each slit
7
of the parallax barrier
4
.
The function of the parallax optic such as the parallax barrier
4
is to restrict the light transmitted through the pixels to certain output angles. This restriction defines the angle of view of each of the pixel columns behind the associated slit. The angular range of view of each pixel is determined by the pixel width and the separation between planes containing the pixels and the parallax optic. As shown in
FIG. 1
, the three columns
5
associated with each slit
7
are visible in respective viewing windows.
FIG. 2
of the accompanying drawings illustrates the angular zones of light created from an SLM
1
and a parallax barrier
4
where the parallax barrier slits have a horizontal pitch equal to an exact integer multiple of the pixel column pitch. In this case, the angular zones coming from different locations across the display surface intermix and a pure zone of view for image
1
or image
2
does not exist. Thus, each eye of an observer will not see a single image across the whole of the display but instead will see slices of different images at different regions on the display surface. In order to overcome this problem, the pitch of the parallax optic is reduced slightly so that the angular zones converge at a predetermined plane, generally known as the “window plane”, in front of the display. This change in the parallax optic pitch is termed “viewpoint correction” and is illustrated in
FIG. 3
of the accompanying drawings. The window plane is shown at
8
and the resulting substantially kite shaped viewing regions are shown at
9
and
10
. Provided the left and right eyes of the observer remain in the viewing regions
9
and
10
, respectively, each eye will see the single image intended for it across the whole of the display so that the observer will perceive the 3D effect,
The window plane
8
defines the optimum viewing distance of the display. An observer whose eyes are located in this plane receives the best performance of the display. As the eyes move laterally in this plane, the image on the display remains until the eyes reach the edge of the viewing regions
9
and
10
, whereupon the whole display swiftly changes to the next image as one eye moves into the adjacent viewing region. The line of the window plane within each viewing region Is generally termed a “viewing window”.
FIG. 4
of the accompanying drawings illustrates an autostereoscopic display which differs from that shown in
FIG. 1
in that the parallax barrier
4
is disposed on the rear surface of the SLM
1
. This arrangement has the advantage that the barrier
4
is disposed behind the SLM
1
away from possible damage. Also, the light efficiency of the display may be improved by making the opaque parts of the rear surface of the parallax barrier
4
reflective so as to recycle light which is not incident on the slits
7
.
A switchable diffuser
11
is shown between the parallax barrier
4
and the SLM
1
. Such a diffuser may comprise a polymerispersed liquid crystal which is switchable between a low scattering or substantially clear state and a highly scattering state. In the low scattering state, the display operates as described hereinbefore as an autostereoscopic 3D display. When the diffuser is switched to the highly scattering state, light rays are deflected on passing through the diffuser and form an even or “Lambertian” distribution which “washes out” the effect of the parallax barrier
4
and so destroys the creation of viewing regions. In this mode, the display therefore acts as a conventional 2D display with the full spatial resolution of the SLM
1
being available for displaying 2D images.
In the displays described hereinbefore, the basic principle is that a subset of the total number of pixels of the SLM
1
is visible to each eye at any one time. Thus, each of the views represented in the viewing regions uses a fraction of the total resolution of the SLM
1
. In a typical two view spatially multiplexed autostereoscopic display, each eye perceives an image of only half the total resolution. For a three view system, the resolution in each eye is only one third. The representation of complex small characters, such as text and details within images, may therefore be adversely affected. It is desirable to include in the display some means for disabling or overcoming the parallax imaging system so that the full resolution of the SLM
1
is visible to each eye for the display of detailed 2D information. Although the switchable diffuser
11
shown in
FIG. 4
provides such switching, this add
Ezra David
Harrold Jonathan
Jacobs Adrian Marc Simon
Moseley Richard Robert
Woodgate Graham John
Curtis Craig
Renner Otto Boisselle & Sklar
Sharp Kabushiki Kaisha
Spyrou Cassandra
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