Stereoscopic display

Details Stereoscopic display Stereoscopic display

2000-07-05

2004-03-09

Awad, Amr (Department: 2675)

Computer graphics processing and selective visual display system

Plural physical display element control system

Optical means interposed in viewing path

C345S006000, C348S054000, C348S058000, C359S493010, C349S117000

Reexamination Certificate

active

06703989

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stereoscopic display. Such a display may be used, for example, as a reflective display and in hand-held devices such as small dedicated game computers.
2. Description of the Related Art
A known type of stereoscopic display is disclosed in U.S. Pat. No. 5,537,144. The display is of the spatially multiplexed micropolariser type. Two complementary checkerboard masks are used to select complementary checkerboard patterns of picture elements (pixels) of the two two dimensional (2D) images to be displayed. The selected pixels from the two images are interlaced to form a composite spatially multiplexed image. A micropolariser is then disposed over the composite image so that light from the left view pixels is polarised with a first polarisation and light from the right view pixels is polarised with a second polarisation orthogonal to the first polarisation. An observer wears viewing spectacles comprising orthogonally oriented polarisers so that the left eye can see only the left view pixels whereas the right eye can see only the right view pixels.
Although U.S. Pat. No. 6,5537,144 discloses in detail the checkerboard patterns with right and left view pixels alternating with each other horizontally and vertically in the composite image, there is a suggestion that other patterns are possible. In particular, there is brief reference to a one dimensional array of polariser stripes but no other information is given concerning such an arrangement. Also, the use of a patterned retarder with a uniform polariser to form the micropolariser ie described. In such an arrangement, light from the composite image is first polarised by the uniform polariser. A suitable pattern of retarders is then formed so as to rotate the polarisation of light from either the left or the right pixels so as to maintain the orthogonal polarization.
U.S. Pat. No. 5,537,144 is not concerned with the effects of parallax resulting from the spacing between the micropolariser and the composite image. Similarly, there is no mention or consideration of viewing angle performance.
A known type of stereoscopic display based on the teachings of U.S. Pat. No. 5,537,144 is known as “CyberBook” and is available from VREX Inc., a division of Reveco Inc.
FIG. 1
of the accompanying drawings illustrates this type of display, which comprises a spatial light modulator (SLM)
1
in the form of a liquid crystal device (LCD). The SLM
1
comprises front and rear transparent substrates
2
and
3
defining a cell containing a liquid crystal layer
4
. The display also comprises a back light (not shown) for directing light through the SLM
1
towards a viewing region
5
.
The SLM
1
comprises a rectangular array of pixels, one of which is indicated diagrammatically at
6
. The front substrate carries on its external surface a linear polariser
7
and an array of horizontal retarder stripes such as
8
. The polariser
7
and the array of retarder stripes
8
form a micropolariser. In particular, light from the SLM
1
passing through the polariser
7
emerges with a first linear polarisation. The vertical width of the stripes
8
may be slightly less than the vertical pitch of the pixels
6
so as to ensure that an observer located in the viewing region
5
can see every row of pixels
6
of the SLM
1
through the correct retarder stripe
8
or a gap between adjacent retarder stripes. This is generally referred to as “viewpoint correction”.
Light passing from rows of pixels
6
aligned with gaps between the stripes
8
of the retarder propagated to the viewing region
5
with the linear polarization determined by the polariser
7
. Light from the rows of pixel
6
passing through the aligned stripes
8
of the retarder have their linear polarisation rotated through 90°. An observer indicated diagrammatically at
9
wears viewing spectacles with polarisers
10
and
11
which are oriented so that, for example, the polariser
10
passes light whose polarisation has been rotated by the retarder stripes
8
and attenuates light received directly from the polariser
7
whereas the polariser
11
passes light received directly from the polariser
7
but attenuates light received from the retarder stripes
8
. If the polarisers
10
and
11
are worn over the left and right eyes respectively, of the observer
9
, and if the rows of pixels aligned with the retarder stripes
8
display left view image data whereas the rows of pixels aligned with the gaps between the retarder stripes
8
display right view image data, the observer
9
perceives a stereoscopic three dimensional (3D) image.
Because the retarder stripes
8
extend horizontally, the observer
9
has considerable freedom of movement in a horizontal direction relative to the display and no undesirable visual artefacts will occur because of parallax between the stripes and the pixel apertures which are separated by the thickness of the substrate
2
and the polariser
7
. However, the vertical freedom of movement is far more limited. In a typical example of a display of this type, the front substrate
2
is approximately 1.1 millimeters thick whereas the vertical pitch of the pixels
6
is typically about 300 micrometers. Correct performance of the display relies on the observer seeing the rows of pixels
6
through the respectively aligned retarder stripes
8
or gaps therebetween. Vertical movement of the observer
9
relative to the display out of the intended viewing region
5
immediately results in undesirable visual artefacts. In particular, as the line-of-sight alignment of the pixel rows and the retarder stripes
8
or gaps therebetween becomes lost, dimming artefacts and then crosstalk between the left and right images become visible. Further vertical movement results in the pixel rows displaying the left and right view image data being seen by the right and left eyes, respectively, of the observer
9
i.e. pseudoscopic viewing. Such visual artefacts are most undesirable so that the vertical freedom of movement of the observer
9
for correctly viewing the display is severely limited.
Thus, displays of the type shown in
FIG. 1
are of practical use only in applications where the limited vertical viewing freedom is not a problem, for example in desktop displays. Displays of this type are not suitable for reflective displays, where the display is generally tilted according to the prevailing lighting conditions so as to give the best display brightness, and for hand-held displays, such as dedicated games computers which are tilted during the playing process. This is illustrated in
FIG. 2
of the accompanying drawings, where an observer
9
tilts a display
1
in a direction indicated by a double-headed arrow
13
so as to obtain a best view of the display. A reflective display is typically illuminated by an overhead source
14
such as the sun, a lamp or a fluorescent tube. Such a bright small source tends to result in specular reflection an shown at
15
and the observer tilts the display so as to maximise display brightness while avoiding the specular reflection as shown at
15
. The observer
9
may also obtain a best view on the other side of the specular reflection.
FIG. 3
of the accompanying drawings illustrates another known type of stereoscopic display, for example as disclosed in Japanese patent publication no. 9-304740. The display is of the transmissive type and is similar to that shown in
FIG. 1
except that a lenticular screen
12
whose cylindrically converging lenticules are oriented horizontally is disposed in front of the retarder array
8
. In
FIG. 3
, the difference between the vertical pitch of the pixels
6
and the vertical pitch of the retarder stripe
8
is exaggerated to illustrate the viewpoint correction. The vertical pitch of the lenticules of the screen
12
is substantially equal to that of the retarder array
8
but, depending on the spacing between the lenticules
12
and the retarder stripes
8
, is slightly less so as to match the viewpoint correction.
The

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