An autostereoscopic screen and method for reproducing a 3D image
The invention relates to an autostereoscopic screen for the simultaneous reproduction of
several different images, according to the preamble of the main claim, as well as to a method for
the reproduction of a 3D image according to preamble of the auxiliary claim which can be
carried out with such a screen.
A screen of the known type comprises a pixel matrix, on which a multitude of at least six
or at least eight disjoint subsets of pixels are defined such that each of the subsets forms a family
of parallel strips of pixels with a vertical course or one which is inclined to a vertical, wherein the
strips of the different subsets cyclically alternate in the horizontal direction. Moreover, such a
screen comprises an optical element which is arranged in front of or behind the pixel matrix and
which has a grating-like structure orientated parallel to the strips and in each case sets a defined
propagation direction of the light emitted or transmitted from the pixels, so that at a nominal
distance in front of the screen and set by a geometry of the screen, a number of viewing zones
laterally offset relative to one another, said number corresponding to the mentioned multitude,
are defined such that each of the viewing zones is assigned to exactly one of the subsets and the
light departing or transmitted from each of the subsets of pixels is deflected into the viewing
zone assigned to this subset.
Screens of this type are known per se as so-called multi-view displays. With a correct use
of these screens which is known from the state of the art, in each case one of a number of
stereoscopic half-images which corresponds to the mentioned plurality, is reproduced on the
mentioned subsets of pixels, of which half-images in each case in a paired manner two which are
reproduced on subsets with directly adjacent strips, complement one another into a stereo-image.
In this manner, not only can an individual viewer, but also several viewers placed next to one
another in front of the screen can in each case autostereoscopically perceive a threedimensionally
appearing image of the same scene. Moreover, a viewer in front of the screen can
move in the lateral direction without losing the three-dimensional impression. Rather, he will see
the same scene from a perspective changing according to his movement.
However, it is thereby disadvantageous that the viewer or each of the viewers can only
see a 3D-image of adequate quality when, with his eyes, he maintains the nominal distance in
front of the screen and which is set by the geometry of the screen. Otherwise, each eye of the
viewers sees contributions specifically in different regions of the screen and to some extent
overlapping of different half-images.
It is the object of the invention, to develop an autostereoscopic screen, on which one can
in each case see a three-dimensionally acting image of a reproduced scene, from different, where
possible freely selectable distances, wherein as in the described state of the art, it is to be possible
for several viewers to simultaneously look at the screen and there each see a three-dimensionally
acting image of the scene, and for a viewer to move laterally, without the three-dimensional
impression becoming lost by him. It is further the object of the invention, to suggest a
corresponding method for reproducing 3D-images on an autostereoscopic screen, which meets
these demands.
According to the invention, this object is achieved by an autostereoscopic screen with the
characterising features of the main clam in combination with the features of the dependent
claims, as well as by a method with the features of the auxiliary claim. Advantageous designs are
to be deduced from the features of the dependent claims.
With the suggested screen, a lateral offset between the directly adjacent strips in each
case is so small, that the mentioned viewing zones in the nominal distance in front of the screen
are laterally offset with respect to the directly adjacent viewing zones in each case by less than an
average eye distance. Moreover, this screen comprises a control unit for activating the pixel
matrix in dependence on image data which define a 3D-image. This, for activating the pixel
matrix for an autostereoscopic viewing of the 3D-image from a viewing distance in front of the
screen, said distance being different to the nominal distance, is configured to carry out the
following steps:
- defining a plurality, smaller compared to the mentioned multitude, of at least three or at
least four disjoint part-sets of the pixels of the pixel matrix, which are different to the
mentioned subsets, in a manner such that each of the part-sets forms a family of parallel
bands, wherein each of these bands or each of the majority of the bands or each of at least
some of the bands is formed by way of grouping together at least two of the mentioned
strips of pixels which lie directly next to one another, and wherein the bands of the
different part-sets cyclically alternate in the horizontal direction, and
- reproducing a number of stereoscopic half-images, corresponding to the mentioned
plurality, and which are defined by the image data and complement one another in pairs
into a stereo-image perceivable as a 3D-image, by way of the pixels of the pixel matrix,
in a manner such that in each case one of the stereoscopic half-images is reproduced on
each of the thus defined part-sets.
Thereby, the control unit is configured to define the mentioned part-sets and bands such
that at the mentioned viewing distance in front of the screen, a number of regions, corresponding
to the mentioned plurality, which are laterally offset to one another, are defined such that each of
these regions is assigned to exactly one of the part-sets and that the light departing or transmitted
from each of the part-sets of pixels is deflected by the optical element into the region assigned to
this part-set, wherein a line which runs through the respective band in the longitudinal direction
and which is defined in that the light departing from this line falls exactly centrally into one of
the regions, lies in each of these bands next to the middle of this band by no more than half the
mentioned lateral offset.
On account of the suggested measures, one succeeds in an observer who views the
correspondingly activated screen from the mentioned viewing distance, seeing a threedimensionally
acting image of a good image quality even if the viewing distance differs from the
nominal distance. In particular, by way of the described activation of the pixel matrix, one
succeeds in the viewer, at least to a very good approximation, seeing two stereoscopic halfimages
which are complementary to one another and complement one another into a stereoimage,
despite the viewing distance not actually matching the geometry of the screen, wherein
one simultaneously avoids evident and annoying irregularities or jumps resulting with a lateral
movement. The screen can thus be used for very different viewing distances. An adaptation of
the screen itself to the viewing distance which under certain circumstances is determined by a
certain application - e.g. placing in a room of a given size and shape - is thereby not necessary.
The initially mentioned subsets of pixels of the screen can be seen as different channels
of the screen for the case, in which the screen is operated as a normal multi-view display for
viewing at the nominal distance. These channels and the associated viewing zones here are so
narrow, that it is thereby possible to group together two or also more channels for the
reproduction of a single one of different stereoscopic half-images. This is particularly the case if
the mentioned viewing zones at the nominal distance in front of the screen are laterally offset
with respect to the directly adjacent viewing zones in each case at the most by half the average
eye distance. By way of this results the possibility of adapting the screen to other viewing
distances in the described manner, since the bands of pixels which are grouped together from
several strips and on which in each case image strips of one of the half-images are reproduced,
can be laterally shifted in each case by the width of a strip, thus by less than a width of the
complete band of pixels, by way of redistribution of the pixels between the mentioned part- sets.
An adaptation to other viewing distances is thus possible by way of a simple redefinition of the
mentioned part-sets by way of redistributing the mentioned strips of pixels between the different
part-sets or between the bands of pixels which form these part-sets.
With a given geometry of the screen, the above mentioned condition as to how the partsets
and bands are to be defined with a given viewing distance can be fulfilled by way of the
application of simple geometric relations which result from beam optics and trigonometry.
The term "stereoscopic half-images" in the present document in each case indicates views
of a scene, of which two complement one another into a stereo-image of this scene, by way of
them corresponding to views from - actual or virtual - camera positions or eye positions which
are laterally offset relative to one another by an amount defining a disparity of these images -
typically by roughly the average eye distance. The individual views are indicated as stereoscopic
half-images even in the case of a family of more than two views which have these characteristic
in pairs. Here, when talks of a large number of stereoscopic half-images which complement one
another in pairs into a stereo-image, then the disparities between the different possible pairs of
half-images will of course differ from one another. Usefully, the disparities thereby are selected
such that of the family of half-images, in each case the half-images which are represented on two
part-sets of pixels with directly adjacent bands of pixels, in each case correspond to views from
two camera positions or eye positions which are laterally offset relative to one another by
roughly an average eye distance - inasmuch as with regard to these two half-images it is not
indeed the case of the first and last half-image, which differ from one another by a corresponding
larger disparity.
With regard to the described screen, it can be the case of a simple multi-view display
which is merely equipped with a special control unit or one which is programmed in a special
manner, so that additionally to the nominal distance, freely selectable other viewing distances are
possible, at least to within certain limits. The viewing zones with typical embodiments are
usefully dimensioned such that their lateral distance in each case corresponds to an average eye
distance - for example 65 mm - and the mentioned multitude can e.g. be sixteen or even larger.
The pixel matrix can e.g. be given by a LCD or an OLED screen. With regard to the optical
element it can in particular be the case of a parallax barrier or a lenticular lens. A combination of
these grid types is also possible. In the case of a lenticular lens, the grating-like structure is
typically formed by a family of parallel cylindrical lenses. Barrier grids, in particular slot grids
can be used as parallax barriers. Finally, the optical element can also be a Fresnel structure or an
LC-structure, which reproduces a slot grid or another grid type. The pixels can be multicolour
pixels or subpixels of different basic colours - e.g. red, green and blue. In the latter mentioned
case, typically three pixels or subpixels from three consecutive lines complement one another
into a colour-neutral or colour-authentic image point.
An advantageous method for reproducing a 3D-image on an autostereoscopic screen of
the described manner which achieves the set object is also suggested. With regard to this method,
it is the case of a particular application of a screen with a pixel matrix and with an optical
element arranged in front of or behind the pixel matrix, wherein a multitude of at least six or at
least eight disjoint subsets of pixels are defined on the pixel matrix such that each of the subsets
forms a family of parallel strips of pixels with a course which is vertical or inclined to the
vertical, wherein the strips of the different subsets cyclically alternate in the horizontal direction,
and wherein the optical element has a grating-like structure orientated parallel to the strips and in
each case sets a defined propagation direction for light departing or transmitted from the pixels,
so that at a nominal distance in front of the screen and set by a geometry of the screen and which
is set by a geometry of the screen, a number corresponding to the mentioned multitude, of
viewing zones laterally offset to one another are defined such that each of the viewing zones is
assigned to exactly one of the subsets and that the light departing or transmitted from each of the
subsets of pixels is deflected into the viewing zone assigned to this subset. A lateral offset
between the directly adjacent strips, with this screen, in each case is so small, that the mentioned
viewing zones at the nominal distance in front of the screen are laterally offset with respect to the
directly adjacent viewing zones, in each case by less than an average eye distance.
With the method, the pixel matrix of this screen is activated in dependence on image data
which define a 3D-image, for an autostereoscopic viewing of the 3D image at a viewing distance
in front of the screen which differs from the nominal distance. For this, the method comprises the
following steps:
- defining a plurality smaller compared to the mentioned multitude, of at least three or at
least four disjoint part-sets of pixels of the pixel matrix which are different to the
mentioned subsets, in a manner such that each of the part-sets forms a family of parallel
bands wherein each of these bands or each of the majority of the bands or each of at least
some of the bands is formed by grouping together at least two of the mentioned strips of
pixels which lie directly adjacent one another, and wherein the bands of the different
part-sets cyclically alternate in the horizontal direction, and
- reproducing a number corresponding to the mentioned plurality, of stereoscopic halfimages
which are defined by the image data and complement one another in pairs into a
stereo-image perceivable as a 3D image, by way of the pixels of the pixel matrix, in a
manner such that in each case one of the stereoscopic half-images is reproduced on each
of the thus defined part-sets.
Thereby, the mentioned part-sets and bands are defined such that at the mentioned
viewing distance in front of the screen, a number corresponding to the mentioned plurality, of
regions laterally offset to one another are defined such that each of these regions is assigned to
exactly one of the part-sets and that the light departing or transmitted from each of the part-sets
of pixels is deflected by the optical element into the region assigned to this part-set, wherein a
line which runs in the longitudinal direction through the respective band and which is defined in
that the light departing from this line falls exactly centrally into one of the regions, lies in each of
the bands next to the middle of this band by not more than half the mentioned lateral offset. This
method can be carried out in its different designs and further developments in particular with a
screen of the type described here.
Due to the fact that the part-sets of the pixels, on which the stereoscopic half-images are
reproduced, and the bands of pixels which form these part-sets and for their part are formed in
each case from at least two strips of pixels, are defined in the manner described here, a viewer
can see the 3D-image in a good quality on the screen, although he is located at a viewing
distance in front of this screen, which differs from the nominal distance for which the screen is
actually designed.
The images, in particular the 3D-images and stereoscopic half-images which are
discussed here can in each case also be moved images, thus sequences of temporally successive
images or frames.
In typical cases, the mentioned regions at the viewing distance in front of the screen,
which differs from the nominal distance, are laterally offset with respect to the directly adjacent
regions in each case by more than half the average eye distance. If the channels mentioned
further above are not unusually narrow, as a rule this results in that in each case at least two of
the mentioned strips of pixels are grouped together, in order to form the bands of pixels which
are played in with the image strips of the different half-images. It is particularly useful if the
regions are laterally offset with respect to the directly adjacent regions, as precisely as possible
by an average eye distance of typically about 65 mm.
One obtains particularly satisfactory results with the described measures if the viewing
distance which differs from the nominal distance is smaller than the nominal viewing distance.
This together with the relatively narrow strips of pixels on the pixel matrix leads to sufficient
strips of pixels being available, in order to form the mentioned bands of pixels and to these strips
being able to be laterally shifted in adequately small steps of pixels, in order to realise a
satisfactory image quality for a viewing at the mentioned viewing distance.
The control unit of the screen can be configured for the manual input or for the entry of a
parameter which defines a distance value, wherein the control unit then is further configured to
activate the pixel matrix such that the mentioned viewing distance corresponds to this distance
value. The screen can then be adapted for different viewing distances depending on the input of a
user or another setting for different viewing distances. Accordingly, with regard to the method,
one can envisage a parameter which defines a distance value being inputted into a control unit of
the screen or transferred to the control unit, wherein the pixel matrix is activated by the control
unit such that the mentioned viewing distance corresponds to this distance value.
One can also envisage the screen additionally comprising a tracking device for
determining a distance between an eye pair of at least one viewer and the screen, wherein the
control unit is configured to activate the pixel matrix such that the mentioned viewing distance
corresponds to the distance determined by the tracking device. An adaptation of the screen to a
viewing distance which differs from the nominal distance and which changes under certain
circumstances can then also be effected in an automatic manner. Accordingly, with a further
development of the described method, a distance between and eye pair of at least one viewer and
the screen is detected, wherein the pixel matrix is activated such that the viewing distance
corresponds to the thus detected distance.
Additionally, under certain circumstances a lateral position of the at least one eye pair
can also be detected, wherein the pixel matrix is then activated in dependence on the detected
lateral position such that the at least one eye pair is located in a field which is spanned by the
mentioned regions and from which the stereo-image is autostereoscopically viewable. With a
lateral movement of the viewer or of one of the viewers, the activation of the screen by way of
this can be adapted such that one prevents the viewer leaving the region, from which the 3Dimage
is visible and can be recognised as such. The tracking device for this purpose can be
configured to also determine a lateral position of the at least one eye pair, wherein the control
unit then is further configured to activate the pixel matrix in dependence on the lateral position
determined by the tracking device, so that the at least one eye pair is located within a field which
is spanned by the mentioned regions and from which the stereo-image is autostereoscopically
visible.
In a further formation of the screen, the optical element can be designed in a controllable
manner and forms lens elements with refraction characteristics which can be changed depending
on an activation of the optical element, wherein the control unit is configured to activate the
optical element depending on the viewing distance, in order to adapt refraction characteristics of
the lens elements to this viewing distance. Thus e.g. a focal width of the lens element can be
reduced in size, in order to adapt the optical element to a shorter viewing distance. By way of
this, crosstalk between different image channels, thus between the different reproduced halfimages
and which increases with a changing viewing distance, can be avoided.
Embodiment examples are hereinafter described by way of the Figures 1 to 5. There are
shown in:
Fig. 1 in a schematic representation, a plan view of an autostereoscopic screen and a
viewing space in front of this screen,
Fig. 2 a detail of a pixel matrix of the screen of Fig. 1, in a front view,
Fig. 3 a detail from Fig. 1, in an enlarged representation,
Fig. 4 in a representation corresponding to Fig. 1, the same screen, wherein here some
components of the screen are omitted and only a few beam paths are drawn by
way of example, in order to explain an alternative activation of the screen, and
Fig. 5 a detail of Fig. 4 in an enlarged representation.
An autostereoscopic screen which is particularly suitable, as a multi-view display, to
simultaneously reproduce a multitude of in the present example up to sixteen different images, is
represented in Figure 1. This screen comprises a pixel matrix 1 and an optical element 22 which
is arranged in front of the pixel matrix 21. Moreover, the screen comprises a control unit 23 for
activating the pixel matrix 2 1 in dependence on image data 24 which define the 3D-image.
Typically, this 3D image can change temporally, so that to be more specific it is the case of an
image sequence. The image data 24 can thereby be stored on a data carrier e.g. can be read out
from there or be defined by a computer game, in dependence on its course.
With regard to the pixel matrix 21, it is the case of a LCD or an OLED screen with a
multitude of pixels 25 which are arranged in lines and columns. A detail of this pixel matrix 2 1 is
shown in Figure 2. There, the individual pixels 25 are represented in each case by rectangles. In
the present case, with regard to the pixels 25 it is the case of subpixels of the basic colours red,
green and blue - in Figure 2 in each case characterised by the letters R, G and B.
In the present case, a multitude of sixteen - the multitude can of course under certain
circumstances be even significantly greater or somewhat smaller - disjoint subsets of pixels 25
are defined on the pixel matrix 2 1 such that each of these subsets forms a family of parallel
strips. The subsets are numbered from 1 to 16 and in Figure 2 the pixels 25 in each case in the
upper region of the respective pixel are provided with the number of the subset, to which the
pixel 25 belongs. As is to be recognised in Figure 2, the mentioned strips are inclined with
respect to the vertical such that three pixels 25 lying directly over one another within each of the
strips each have three different basic colours and thus can complement one another into a colourneutral
image pint. Thereby, the strips of the different subsets cyclically alternate in the line
direction, thus in the horizontal direction. Of course, it would also be conceivable to arrange the
subpixels of different colours differently, so that the strips with the same characteristics would be
vertical or inclined with respect to the vertical by another angle. The pixel matrix 2 1 instead of
the subpixels of different basic colours could also comprise colour-neutral or multicolour pixels.
The optical element 22 can e.g. be designed as a slot grid or lenticular lens and has a
grating-like structure which is orientated parallel to the strips and indicated by dashed lines in
Figure 2. Thereby in the present case
d = 16b D n/(Dn+a),
for a period d of this structure in the lateral direction - corresponding to the line direction,
wherein b is a lateral distance centroids of areas of adjacent pixels 25, a a distance between the
pixel matrix 2 1 and the optical element 22 and Dn a so-called nominal distance. The lateral
distance b corresponds also to a lateral offset of the directly adjacent strips of pixels 25. The
optical element 22 by way of this in each case sets a defined propagation direction of the light
which departs or is transmitted by the pixels 25. This is effected such that at the nominal distance
D in front of the screen, a number corresponding to the previously mentioned multitude, of
sixteen viewing zones 26 laterally offset to one another are defined such that each of the viewing
zones 26 is assigned to exactly one of the subsets and that the light departing or transmitted from
each of the subsets of pixels 25 is deflected into the viewing zone 26 assigned to this subset.
Modifications, with which the optical element 22 is arranged behind the pixel matrix 21, are
likewise possible. The viewing zones 26 in Figure 1 are each represented as a rhombus and
numbered from 1 to 16 according to the subset quantities. The viewing zones adjacent 26 to one
another are laterally offset to one another by about 32 mm which corresponds roughly to half the
average eye distance.
The sixteen part-sets of pixels 25 of the pixel matrix, as sixteen different channels of the
screen can be played in with sixteen different images, which are then each visible from one of
the viewing zones 26. Since the mentioned strips on the pixel matrix 2 1 and accordingly also the
viewing zones 26 are however relatively narrow, the subsets of pixels 25 or the channels are
however grouped together in pairs, with an operating mode of the screen, in which this
corresponds to a conventional multi-view display. Then eight different stereoscopic half-images
are reproduced on the pixel matrix 2 1 and specifically each on in each case two consecutive
subsets of the mentioned subsets of pixels 25. Thus the subsets 1 and 2 reproduce a first, the
subsets 3 and 4 a second, the subsets 5 and 6 a third, the subsets 7 and 8 a fourth, the subsets 9
and 10 a fifth, the subsets 11 and 12 a sixth, the subsets 13 and 14 a seventh and the subsets 16
and 16 an eighth stereoscopic half-image. Each of these stereoscopic half-images is then visible
from one of in total eight enlarged viewing zones 26' which are numbered in Figure 1 from to
8'. The stereoscopic half-images are thereby selected such that the two stereoscopic half-image
which are visible from enlarged viewing zones 26' directly adjacent one another, complement
one another in each case into a stereo-image which corresponds to a view of the thus reproduced
3D-image. Then, one or more viewers can in each case see one of the three-dimensionally acting
views with a depth effect, from a viewing plane 27 which lies at a nominal distance D in front of
the screen.
Here, a different operating manner of the screen is now to be described, with which the
pixel matrix 2 1 for an autostereoscopic viewing of the 3D-image is activated from a viewing
distance D which differs from the nominal distance Dn.
In order to measure the viewing distance D, the screen in the present embodiment
example comprises a tracking device which here is given by a stereo-camera 28 directed onto the
viewing space in front of the screen, and an evaluation device 29 for carrying out a image
evaluation method. With this tracking device, a head position of at least one viewer is detected
and the viewing distance D as the distance between an eye pair of this viewer and the screen is
measured. The evaluation device 29 transmits the value of the viewing distance D to the control
unit 23. Alternatively, the desired viewing distance D can also be inputted into the control unit 23
by way of a manual input of the user. In the present case, the viewing distance D is smaller than
the nominal distance Dn.
The control unit 23 now by way of a suitable programming-technological device, in
dependence on the image data 24 and the viewing distance D determined by the tracking device,
carries out some steps which are explained in more detail hereinafter, in order to activate the
pixel matrix 1 for an autostereoscopic viewing of the 3D-image from the distance D in front of
the screen which differs from the nominal distance Dn.
Firstly, a plurality smaller compared to the mentioned multitude, of in the present case
eight disjoint part-sets of pixels 25 which are different to the previously mentioned subsets, are
defined on the pixel matrix and specifically in a manner such that each of these part-sets forms a
family of parallel bands, wherein each of these bands is formed by way of grouping together at
least two of the previously mentioned strips of pixels 25 which lie directly next to one another,
and wherein the bands of the different part-sets cyclically alternate in the horizontal direction.
Thereby, the mentioned part-sets and bands are defined such that a number corresponding to the
mentioned plurality, of regions 30 offset relative to one another, thus eight regions 30 in the
present case, are defined at the mentioned viewing distance D in front of the screen such that
exactly one of the part-sets is assigned to each of these regions 30 and that the light departing or
transmitted from each of the part-sets of pixels 25 is deflected by the optical element 22 into the
region 30 assigned to this part-set.
The part-sets here are numbered from 1 to 8, and in Figure 2 the pixels are each provided
with the number of the part-set to which the pixel 25 belongs, in the lower region of the
respective pixel. The course of the mentioned bands in Figure 2 thus as with the course of the
strips which form it, is to be recognised by way of the two numberings represented in the pixels
25. In Figure 1 in turn, the regions 30 are represented as a rhombus in each case according to
their horizontal cross-sectional shape and are numbered according to the part-sets 1 to 8, thus are
provided in each case with the number of the part-set, to which the respective region 30 is
assigned in the context explained above. Beam paths which depart from the pixels 25 of these
part-sets and lead into the respective regions 30, are drawn by way of example for the part-sets 4
and 5. Thereby, the beams which depart from lateral edges of these pixels 25 are represented as
dashed lines, and beams which fall centrally into the respective region 30 are drawn in as
unbroken lines. The relations are represented in Figure 3 enlarged once again, for a detail which
is drawn in Figure 1 as a dashed rectangle. As also in the other figures, recurring features here
are provided with the same reference numerals.
An important factual detail is to be recognised in Figure 3. The mentioned part-sets and
the bands of pixels which are formed in each case of at least two strips of pixels 25 and form
these part-sets, are specifically defined such that a line running in the longitudinal direction
through the respective band and being defined in that the light departing from this line falls
exactly centrally into one of the regions 30, lies in each of the bands next to the middle of this
band by not more than half the mentioned lateral offset b. In Figure 3 too, the pixels 25 are
additionally provided with the number of the part-set, to which they belong. The dashed lines
there lead to the edges of the bands belonging to the part-sets with the numbers 4 and 5, and the
beams shown as unbroken lines end on the previously mentioned lines within these bands, which
are defined such that light departing from these lines falls exactly centrally into one of the
regions 30. The mentioned factual detail, according to which these lines lie next to the middle of
the respective band by no more than half the lateral offset b of adjacent strips, thus in Figure 3 is
to be recognised at the lines which represent the beam paths for the part-sets 4 and 5. Some
pixels 25 which in Figure 3 are held black and in Figure 2 are provided with the reference 1/8 in
each case in the lower region, can selectively either be assigned to none of the part-sets or to the
part-set 1 or the part-set 8. The bands thus in each case have a width of at least 2b, wherein b
again indicates the lateral distance of centroids of area of adjacent pixels 25 and corresponds to
the lateral offset of the directly adjacent strips of pixels 25. It is possible that, depending on the
value of the viewing distance D and of the geometry of the screen, some of the bands have a
width of 3b. Thus, it is not necessary that the width of the respective band is the same for all
bands. As is to be recognised in the Figures 2 and 3, the average lateral distance between the
directly adjacent bands which form the mentioned part-sets, is somewhat larger than 2b which
results from the simple geometric relations and the fact that the viewing distance D is, in the
present case, smaller than the nominal distance D . Thereby, the relation given by the geometric
characteristics of the screen is given by
8b'/(D+a) = d/D
where b' is the average lateral distance between the directly adjacent bands which form the
mentioned part-sets.
The control unit 23 now activates the pixel matrix 1 such that a number corresponding
to the mentioned plurality, in the present case eight stereoscopic half-images which are defined
by the image data 24 and complement one another in pairs into a stereo-image perceivable as a
3D image, are reproduced by the pixels 25 of the pixel matrix 2 1 in a manner such that in each
case one of these stereoscopic half-images is reproduced on each of the part-sets which have
been defined in the previously described manner. Thereby, one of many image strips of the
respective half-image is reproduced on each of the mentioned bands of pixels 25. By way of this,
a viewer who with his eyes is located within a field spanned by the regions 30 at a viewing
distance D in front of the screen can see a stereo-image which represents the mentioned 3D
image. The same can also apply for several viewers who are simultaneously there at a distance
from one another which is not too great.
Additionally to the distance between the eye pair of the viewer and the screen, a lateral
position of the eye pair can also be determined with the tracking device. Then the pixel matrix 2 1
can be activated by the control unit 23 additionally in dependence on the lateral position
determined by the tracking device, and specifically such that the thus detected eye pair also
remains within the field which is spanned by the regions 30 and from which the stereo-image is
autostereoscopically visible, when the viewer laterally moves with relatively wide limits. The
regions 30 for this can be laterally displaced with respect to their position shown in Figure 1, by
way of the bands of pixels 25 which form the mentioned part-sets being shifted in the same
direction on the pixel matrix 2 1 and the part-sets being redefined by way of this.
In a particular embodiment, the optical element 22 can be controllable and form lens
elements with refraction characteristic changeable depending on an activation of the optical
element 22. The control unit 23 for this can be configured to moreover also activate the optical
element 22 depending on the viewing distance D and to adapt refraction characteristics of the
lens elements to this viewing distance D.
An alternative activation of the pixel matrix 2 1 is illustrated in the Figures 4 and 5,
wherein recurring features are again provided with the same reference numerals and wherein
Figure 5 in an enlarged manner shows a detail of Figure 4 which is drawn in Figure 4 by way of
a dashed rectangle. Here, only four part-sets of pixels 25 are defined on the pixel matrix 2 1 and
now in each case are formed from four on in a few individual cases five of the mentioned strips
of pixels 25. Accordingly, here only four paired complementary stereoscopic half-images are
reproduced on the pixel matrix 2 1, and specifically again on each of the part-sets of one of the
half-images. Otherwise, that which has been said above accordingly applies for the definition of
the part-sets and the reproduction of the stereoscopic half-images on these part-sets. By way of
this, one achieves a greater lateral offset of the regions 30 which accordingly also turn out larger.
This can be advantageous with a decreasing viewing distance D, in order to ensure that two eyes
of a viewer looking onto the screen from this viewing distance are located in two regions 30
which are adjacent one another. In order to illustrate this, an eye pair with the average eye
distance indicated there as IPD, is also drawn in Figure 4 - but at the nominal distance Dn in front
of the screen. As can be recognised there, the regions 30 at the viewing distance D in front of the
screen are laterally offset with respect to the directly adjacent regions 30, quite accurately by the
average eye distance corresponding to about 65 mm.
In the cases described here, the viewing distance D is always smaller than the nominal
distance Dn. The image information of the reproduced stereoscopic half-images is written into
the pixel matrix 2 in a spread manner for the adaption to this reduced viewing distance D. The
viewing distance D can also just as well be larger than the nominal distance D„. Basically thereby
one proceeds in the same manner as that previously described. Image information of the
reproduced stereoscopic half-images is then written into the pixel matrix 21 in a correspondingly
compressed manner for the adaptation to such an enlarged viewing distance D. This is
particularly possible of, as in the case of Figures 4 and 5, the individual channels of the screen or
the strips of pixels 25 on the pixel matrix 2 1 or the viewing zones 26 are so narrow, that an
adequately high number of in each case at least two strips can be grouped together for forming
the mentioned bands. In this case however, it can occur that one or more of the mentioned partsets
or one or more additional part-sets of pixels 25 which are otherwise defined in the same
manner and are used for reproducing individual stereoscopic half-images, also contain narrower
bands which are formed from only one of the mentioned strips of pixels 25.
In the examples explained here before in detail, the viewing distance D is constant for all
regions 30. This means that the distance between the centre of the respective region 30 and the
screen is the same for all regions 30. It should be noted that this is not necessarily the case.
Instead, the viewing distance D could be defined as a function assuming different values for
different lateral positions in front of the screen. Thus, if x is a variable or parameter defining the
lateral position in front of the screen as indicated by the coordinate system shown in Figure , the
viewing distance D(x) could be a non-constant function of x. The bands of the different part-sets
of pixels 25 are shifted with respect to their positions shown in Figure 1 such that, for each of the
regions 30, the distance between the respective region 30 and the screen corresponds to the value
D(xj) with X being the lateral position of the centre of this region 30.
Patent claims
1. An autostereoscopic screen for the simultaneous reproduction of several different images,
comprising:
a pixel matrix (21), on which a multitude of at least six or at least eight disjoint subsets of pixels
(25) are defined such that each of the subsets forms a family of parallel strips of pixels (25) with
a vertical course or one which is inclined to a vertical, wherein the strips of the different subsets
cyclically alternate in the horizontal direction,
an optical element (22) which is arranged in front of or behind the pixel matrix ( 1) and which
has a grating-like structure orientated parallel to the strips and in each case sets a defined
propagation direction of the light emitted or transmitted from the pixels (25), so that at a nominal
distance (Dn) in front of the screen and which is set by a geometry of the screen, a number
corresponding to the mentioned multitude, of viewing zones (26) laterally offset relative to one
another, are defined such that each of the viewing zones (26) is assigned to exactly one of the
subsets and that the light departing or transmitted from each of the subsets of pixels (25) is
deflected into the viewing zone (26) assigned to this subset, and
a control unit (23) for activating the pixel matrix (21) in dependence on image data (24) which
define a 3D-image,
characterised in that
a lateral offset (b) between the directly adjacent strips in each case is so small that the mentioned
viewing zones (26) at the nominal distance (Dn) in front of the screen are laterally offset with
respect to the directly adjacent viewing zones (26) in each case by less than an average eye
distance,
wherein the control unit (23), for activating the pixel matrix (21) for an autostereoscopic viewing
of the 3D-image from a viewing distance (D) in front of the screen, said distance being different
to the nominal distance ( ), is configured to carry out the following steps:
- defining a plurality smaller compared to the mentioned multitude, of at least three or at
least four disjoint part-sets of the pixels (25) of the pixel matrix (21) which are different
to the mentioned subsets, in a manner such that each of the part-sets forms a family of
parallel bands, wherein each of these bands or each of the majority of the bands or each
of at least some of the bands is formed by way of grouping together at least two of the
mentioned strips of pixels (25) which lie directly next to one another, and wherein the
bands of the different part-sets cyclically alternate in the horizontal direction, and
- reproducing a number corresponding to the mentioned plurality, of stereoscopic halfimages
which are defined by the image data (24) and complement one another in pairs
into a stereo-image perceivable as a 3D-image, by way of the pixels (25) of the pixel
matrix (21), in a manner such that in each case one of the stereoscopic half-images is
reproduced on each of the thus defined part-sets,
wherein the mentioned part-sets and bands are defined such that at the mentioned viewing
distance (D) in front of the screen, a number corresponding to the mentioned plurality, of regions
(30) which are laterally offset to one another, is defined such that each of these regions (30) is
assigned to exactly one of the part-sets and that the light departing or transmitted from each of
the part-sets of pixels is deflected by the optical element (22) into the region (30) assigned to this
part-set, wherein a line which runs through the respective band in the longitudinal direction and
which is defined in that the light departing from this line falls exactly centrally into one of the
regions (30), lies in each of the bands next to the middle of this band by no more than half the
mentioned lateral offset (b).
2. A screen according to claim 1, characterised in that the mentioned viewing zones (26) at
the nominal distance (Dn) in front of the screen are laterally offset with respect to the directly
adjacent viewing zones (26) in each case at the most by half an average eye distance.
3. A screen according to one of the claims 1 or 2, characterised in that the mentioned
regions (30) at the mentioned viewing distance (D) in front of the screen, are laterally offset with
respect to the directly adjacent regions (30) in each case by more than half the average eye
distance.
4. A screen according to one of the claims 1 to 3, characterised in that the viewing distance
(D) differing from the nominal distance (Dn) is smaller than the nominal viewing distance (D ) .
5. A screen according to one of the claims 1 to 4, characterised in that the control unit (23)
is configured for the manual input or for the entry of a parameter which defines a distance value,
wherein the control unit (23) is configured to activate the pixel matrix (21) such that the
mentioned viewing distance (D) corresponds to this distance value.
6. A screen according to one of the claims 1 to 5, characterised in that it comprises a
tracking device for determining a distance between an eye pair of at least one viewer and the
screen, wherein the control unit (23) is configured to activate the pixel matrix (21) such that the
mentioned viewing distance (D) corresponds to the distance determined by the tracking device.
7. A screen according to claim 6, characterised in that the tracking device is configured to
also determine a lateral position of the at least one eye pair, wherein the control unit (23) is
configured to activate the pixel matrix (21) in dependence on the lateral position determined by
the tracking device, so that the at least one eye pair is located in a field which is spanned by the
mentioned regions (30) and from which the stereo-image is autostereoscopically visible.
8. A screen according to one of the claims 1 to 7, characterised in that the optical element
(22) is controllable and forms lens elements with refraction characteristics which can be changed
depending on an activation of the optical element (22), wherein the control unit (23) is
configured to activate the optical element (22) depending on the viewing distance (D), in order to
adapt refraction characteristics of the lens elements to this viewing distance (D).
9. A method for reproducing a 3D-image on an autostereoscopic screen with a pixel matrix
(2 1) and with an optical element (22) arranged in front of or behind the pixel matrix,
wherein a multitude of at least six or at least eight disjoint subsets of pixels (25) are defined on
the pixel matrix (21) such that each of the subsets forms a family of parallel strips of pixels (25)
with a course which is vertical or inclined with respect to the vertical, wherein the strips of the
different subsets cyclically alternate in the horizontal direction,
and wherein the optical element (22) has a grating-like structure orientated parallel to the strips
and in each case sets a defined propagation direction for light departing or transmitted from the
pixels (25), so that at a nominal distance (Dn) in front of the screen and set by a geometry of the
screen, a number corresponding to the mentioned multitude, of viewing zones (26) laterally
offset to one another are defined such that each of the viewing zones (26) is assigned to exactly
one of the subsets and that the light departing or transmitted from each of the subsets of pixels
(25) is deflected into the viewing zone (26) assigned to this subset,
wherein the pixel matrix (21) is activated in dependence on image data (24) which define a 3Dimage,
characterised in that
a lateral offset (b) between the directly adjacent strips in each case is so small, that the mentioned
viewing zones (26) at the nominal distance(D ) in front of the screen are laterally offset with
respect to the directly adjacent viewing zones (26), in each case by less than an average eye
distance,
and that the pixel matrix (21) is activated for an autostereoscopic viewing of the 3D-image from
a viewing distance (D) in front of the screen, said distance being different to the nominal distance
(Dn), wherein the method comprises the following steps:
- defining a plurality smaller compared to the mentioned multitude, of at least three or at
least four disjoint part-sets of the pixels (25) of the pixel matrix (21), which are different
to the mentioned subsets, in a manner such that each of the part-sets forms a family of
parallel bands, wherein each of these bands or each of the majority of the bands or each
of at least some of the bands is formed by way of grouping together at least two of the
mentioned strips of pixels (25) which lie directly next to one another, and wherein the
bands of the different part-sets cyclically alternate in the horizontal direction, and
reproducing a number corresponding to the mentioned plurality, of stereoscopic halfimages
which are defined by the image data and complement one another in pairs into a
stereo-image perceivable as a 3D image, by way of the pixels (25) of the pixel matrix
(21), in a manner such that in each case one of the stereoscopic half-images is reproduced
on each of the thus defined part-sets,
wherein the mentioned part-sets and bands are defined such that at the mentioned viewing
distance (D) in front of the screen, a number corresponding to the mentioned plurality, of regions
(30) laterally offset to one another are defined such that each of these regions (30) is assigned to
exactly one of the part-sets and that the light departing or transmitted from each of the part-sets
of pixels (25) is deflected by the optical element (22) into the region (30) assigned to this partset,
wherein a line which runs in the longitudinal direction through the respective band and
which is defined in that the light departing from this line falls exactly centrally into one of the
regions (30), lies in each of the bands next to the middle of this band by not more than half the
mentioned lateral offset (b).
10. A method according to claim 9, characterised in that a parameter which defines a distance
value is inputted into a control unit (23) of the screen or transferred to the control unit (23),
wherein the pixel matrix (21) is activated by the control unit (23) such that the mentioned
viewing distance (D) corresponds to this distance value.
11. A method according to one of the claims 9 or 10, characterised in that a distance between
an eye pair of at least one viewer and the screen is detected, wherein the pixel matrix (21) is
activated such that the viewing distance (D) corresponds to the thus detected distance.
12. A method according to claim 11, characterised in that a lateral position of the at least one
eye pair is also be detected, wherein the pixel matrix (21) is then activated in dependence on the
detected lateral position such that the at least one eye pair is located in a field which is spanned
by the mentioned regions (30) and from which the stereo-image is autostereoscopically viewable.
13. The use of a screen according to one of the claims 1 to 8 for carrying out a method
according to one of the claims 9 to 12.