WO2011060511A1

WO2011060511A1 - Viewing screen

Info

Publication number: WO2011060511A1
Application number: PCT/BE2009/000058
Authority: WO
Inventors: Kristof Soreyn
Original assignee: Xl Holding, Besloten Vennootschap Met Beperkte Aansprakelijkheid
Priority date: 2009-11-19
Filing date: 2009-11-19
Publication date: 2011-05-26

Abstract

Viewing screen (1) for rendering two-dimensional and three- dimensional images, whereby three-dimensional images are discernable by means of spectacles (8) with two different polarizing glasses (7), whereby the viewing screen (1) is built of a matrix of pixels (2) formed of light-emitting elements (3), whereby every pixel (2) contains a polarizer (6) which polarizes the emitted light and whereby the light of one part of the light-emitting elements (3) is polarized in a first direction (A) so as to form an image which is discernable via a first glass (7A) of the spectacles (8), whereas the light of the remaining part of the light- emitting elements (3) is polarized in a second direction (B), different from the first one, so as to form an image which is discernable via the second glass (7B) of the spectacles (8).

Description

Viewing screen.

The present invention concerns a viewing screen.

In particular, the invention concerns a viewing screen which makes it possible to represent two-dimensional and three-dimensional images whereby three-dimensional images are discernible by means of spectacles with two different polarizing glasses.

Plasma screens, LCD screens and LED viewing screens which make it possible to represent a two-dimensional image are already known. Improved viewing screens are also known which are apt to represent a three-dimensional image.

As is known, a three-dimensional or stereoscopic effect is obtained when both eyes discern a different image.

To this end, the user wears for example specific spectacles with different glasses on the left side and on the right side . Thus, spectacles with colour filters are already known, for example spectacles with a red and green filter or spectacles with a red and blue filter. In order to be able to discern a three-dimensional image with such spectacles, two images are projected on the viewing screen, such that, thanks to the colour filters in the spectacles, each eye observes one of the aforesaid images. A disadvantage is that this application is not suitable for representing colour films, since the reproduction of three- dimensional effects is based on filtering colours.

Also, other techniques are known which filter the image on the basis of the polarization direction of the light.

The user hereby wears spectacles with polarizing glasses or polarization filters, and on the screen are synchronously projected two images by two projectors, each having a different direction of polarization, such that one eye only discerns the image of a first projector and the other eye only discerns the image of the other projector.

A disadvantage is that such an arrangement is rather complex and thus expensive.

Alternatives are possible whereby only one projector is being used which alternately projects images with the right polarization for the left and for the right eye.

A disadvantage, however, is that this technique is not suitable to represent quick changes.

Also, techniques are known whereby the image for one eye is represented on one part of the pixels of the viewing screen and whereby the image for the other eye is represented on the other pixels.

Thus, there are viewing screens with LEDs whereby two polarization filters are provided over the viewing screen to polarize the light from the LEDs, and whereby the user wears appropriate spectacles with polarization filters. Both polarization filters have a hole pattern whereby the light of the LEDs is alternately either or not transmitted. The light which passes the polarization film is thereby horizontally or vertically polarized. One polarization filter is thereby shifted 90° in relation to the other one.

A disadvantage of such LED viewing screens is that they are difficult to produce and thus are very expensive, since the polarization film is made of an expensive material and fixing the film on the existing LED screens is not simple either.

Another disadvantage is that the brightness of the viewing screen is considerably reduced, since the polarization film absorbs a major fraction of the light emitted by the LEDs.

Another disadvantage is that the contrast ratio of the viewing screen deteriorates due to the presence of the polarization filter, resulting in a reduced image quality.

Yet another disadvantage is that the polarization film has a high reflection coefficient, as a result of which external reflections .occur which are experienced as disturbing by the user.

The present invention aims to remedy the aforesaid and/or other disadvantages by providing a viewing screen which makes it possible to render two-dimensional and three- dimensional images, whereby three-dimensional images are discernable by means of spectacles with two different polarizing glasses, whereby the viewing screen is built of a matrix of pixels formed of light-emitting elements, characterised in that every pixel contains a polarizer which polarizes the emitted light in a certain direction, and in that the light of one part of the light-emitting elements is polarized in a first direction so as to form an image which is discerned through a first glass of the spectacles, whereas the light of the remaining part of the light-emitting elements is polarized in a second direction, different from the first direction, so as to form an image which is discerned through the second glass of the spectacles .

An advantage is that the viewing screen has a higher contrast ratio and brightness.

Another advantage is that the user will be less bothered or not bothered at all by external reflections.

Another additional advantage is that the viewing screen is not only suitable for rendering stereoscopic or three- dimensional images, but that it can also correctly render two-dimensional images.

For, when the user takes off the spectacles with the polarization filters, both eyes will discern the image of the LEDs as a whole, and the user will observe a normal two-dimensional image on the viewing screen. Yet another advantage is that the screen can render the images for both eyes simultaneously.

According to the most preferred embodiment of the invention, the pixels contain light-emitting diodes or LEDs .

An advantage is that the viewing screen is easy and cheap to produce, and hence the invention is particularly appropriate to be applied in very large viewing screens or television sets.

, According to the most practical embodiment of the invention, there are two groups of pixels in the viewing screen, whereby the pixels of the first group and of the second group are arranged according to a draughtboard pattern and whereby the forward direction of the polarizers of the first group is perpendicular or almost perpendicular to that of the second group.

In order to better explain the characteristics of the invention, the following preferred embodiment of a viewing screen according to the invention is described as an example without any limitative character, with reference to the accompanying drawings, in which: figure 1 schematically represents a viewing screen according to the invention, seen in perspective;

figure 2 represents the part indicated by arrow F2 in figure 1 on a larger scale. Figure 1 schematically represents a viewing screen 1 according to the invention which mainly comprises an either or not rectangular matrix of pixels 2. As is known, every pixel 2 of the screen 1 may contain a light-emitting element 3, for example in the form of one or several light-emitting diodes.

In a practical embodiment of the invention, the screen 1 contains a printed circuit board 4 on which is provided the matrix of pixels 2, and the light-emitting elements 3 can be provided as SMD components on said printed circuit board 4. Naturally, the connections for the components can also be provided in the printed circuit board 4 via feed-through apertures, but use is preferably made of what are called SMD components or surface-mounted devices, whereby the connections are not provided in front of but against the surface of the plate 4.

Another possible embodiment of the invention consists in forming the pixels 2 as separate, detached image elements, whereby the distance between two neighbouring pixels must not be necessarily small. In this embodiment, the pixels 2 can be connected to the control board by means of one or several wires.

The aforesaid light-emitting elements 3 may contain a single LED 5 or several · LEDs 5 emitting light of different wavelengths. As is represented in detail in figure 2, three LEDs 5A, 5B,5C can be provided for example in a pixel 2, preferably emitting red, green and blue light, such that a colour image is obtained.

It is known that the housing round the LED 5 causes scattering, as a result of which the polarization direction of the light emitted by the LED 5 is arbitrary.

According to the invention, every pixel 2 is provided with a polarizer 6 which polarizes the emitted light of the light-emitting element 3 in a specific direction. In the viewing screen 1, two groups of pixels 2A-2B can be discerned, whereby the light of the light-emitting elements 3A of a first group 2A is polarized in a first direction A so as to form an image which is discerned through a first glass 7A of the spectacles 8, whereas the light of the light-emitting elements 3B of the second group of pixels 2B is polarized in a second direction B so as to form an image which is discerned through the second glass 7B of the spectacles 8. The first and second directions A-B are hereby different from one another.

Preferably, the polarizers of the first and second group 6A-6B only transmit linearly polarized light, and in particular the directions of polarization of the first and second group are perpendicular or practically perpendicular to one another. It will be clear to the expert that the angle between the directions A and B should be preferably 90°, or that it should deviate as little as possible therefrom, such that the light intensity decreases as little as possible and the brightness of the screen is not reduced.

The angle between both directions of polarization may also deviate somewhat from said ideal value of 90°, resulting in a certain disturbance of the three-dimensional effect, since one eye will discern a fraction of the data that were meant for the other eye.

Also, it is clear that the aim must be for both directions of polarization A and B to be preferably perfectly perpendicular to one another, such that each eye only discerns the image that was specifically meant for that eye, as a result of which the three-dimensional effect is not disturbed. In this embodiment, the first group of pixels 6A preferably only transmits horizontally polarized light, whereas the second group 6B only transmits vertically polarized light.

In the most practical embodiment of the invention, the direction of polarization of the first group 6A is equal to the forward direction A of one of the polarizing glasses 7A of the spectacles 8, and the direction of polarization of the second group 6B is equal to the forward direction B of the other glass 7B of the spectacles 8.

In other embodiments of the invention, the first group may transmit linearly polarized light at 45°, in which case the second group will transmit light at a direction of polarization of -45°. In the most practical embodiment of the invention, the pixels 2 of the first and second group 2A-2B are alternately arranged in the viewing screen 1.

The pixels 2 are hereby preferably arranged according to the squares of a draughtboard pattern, such that one type of squares or what are called odd pixels are occupied by the polarizers 6A which transmit the light according to the first direction A, and such that the other type of squares or what are called even pixels are occupied by the polarizers 6B which transmit the light according to the second direction B.

In a practical embodiment of the invention, the polarizer 6 may be provided as a polarization film on the housing of the light-emitting element 3 or it may be generated in the housing of the pixel 2.

It is clear that, in a practical embodiment of the invention, the viewing screen 1 is provided with means, not represented in the figures, which simultaneously control all the pixels 2 so as to simultaneously render the images of the first and second group of pixels 2A-2B on the viewing screen 1.

In alternative embodiments of the invention, the pixels 2 of polarized LEDs or of another polarized light source may be provided with a polarization preserving housing, such that the pixels .2 do not contain any separate polarizers.

In other embodiments of the invention, the pixels 2 may contain light sources 3 emitting circularly polarized light, and the polarizers 6 may comprise quarter-wavelength plates to transform the circularly polarized light in linearly polarized light. Discerning three-dimensional images by means of the viewing screen 1 according to the invention is very simple and as follows .

As is known, the user wears what are called 3D glasses or stereoscopic imaging glasses 8, whereby the glasses 8 contain polarizing glasses 7, and the first and second glasses 7A-7B preferably only transmit horizontally and vertically polarized light respectively. Naturally, in order to render a stereoscopic image on the viewing screen 1, the image is recorded by means of a stereoscopic camera.

Such an image can also be created by means of an appropriate computer program, for example in the form of a computer-generated animation or the like.

The image which has been recorded with such a camera is processed by a processor, which eventually results in two output signals, one for the left eye and the other one for the right eye. By means of a video processor, both signals are transformed into one signal which is sent to each of the pixels 2 of the viewing screen 1.

Thanks to the presence of the polarizers 6, the light of a first group of pixels 2A will be horizontally polarized, whereas the light of the other group of pixels 2B will be vertically polarized.

As the user wears spectacles 8 with polarizing glasses 7, one eye will only discern the horizontally polarized light, and the other eye will only discern the vertically polarized light, such that, when the brain reads both images, they will be interpreted as a single image with stereoscopic effect.

The viewing screen 1 according to the invention can also be used to render two-dimensional images.

Indeed, as the human eye is equally sensitive to horizontally as well as to vertically polarized light, the user will discern a normal, two-dimensional image if he is not wearing any specific stereoscopic spectacles 8.

It will be clear to the expert that, according to the invention, viewing screens can be made whereby every pixel 2 contains a single LED or several colour LEDs or a cluster of similar LEDs in order to further improve the brightness or contrast ratio of the screen, for example. The present invention is by no means restricted to the embodiment described by way of example and represented in the accompanying drawings; on the contrary, such a viewing screen according to the invention which makes it possible to render two-dimensional as well as three-dimensional images whereby three-dimensional images can be discerned by means of spectacles with two different polarizing glasses can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention.

Claims

Claims .

1. - Viewing screen (1) which makes it possible to render two-dimensional and three-dimensional images, whereby three-dimensional images are discernable by means of spectacles (8) with two different polarizing glasses (7), whereby the viewing screen (1) is built of a matrix of pixels (2) formed of light-emitting elements (3), characterised in that every pixel (2) contains a polarizer (6) which polarizes the emitted light in a certain direction, and in that the light of one part of the light- emitting elements (3) is polarized in a first direction (A) so as to form an image which is discerned through a first glass (7A) of the spectacles (8), whereas the light of the remaining part of the light-emitting elements (3) is polarized in a second direction (B) , different from the first direction (A) , so as to form an image which is discerned through the second glass (7B) of the spectacles (8) .

2. - Viewing screen (1) according to claim 1, characterised in that the light-emitting elements (3) are light-emitting diodes or LEDs (5) .

3. - Viewing screen (1) according to claim 2, characterised in that the light-emitting elements (3) are formed of several LEDs (5A-5B-5C) so as to render a colour image.

4. - Viewing screen (1) according to any one of the preceding claims, characterised in that the polarizers (6) are . alternately arranged according to a draughtboard pattern with squares forming the pixels (2) of the viewing screen (1), whereby one type of squares is occupied by polarizers (6A) which polarize the light in the first direction (A) , whereas the other type of squares is occupied by polarizers (6B) which polarize the light in the second direction (B) .

5. - Viewing screen (1) according to any one of the preceding claims, characterised in that the polarizers (6) only transmit linearly polarized light.

6. - Viewing screen (1) according to any one of the preceding claims, characterised in that the first and second directions of polarization (A-B) are perpendicular or practically perpendicular to one another, in accordance with the direction of polarization of the glasses (7) of the spectacles (8).

7. - Viewing screen (1) according to any one of the preceding claims, characterised in that the polarizer (6) is integrated inside the housing of the light-emitting element (2) .

8. - Viewing screen (1) according to claim 7, characterised in that the polarizer (6) is formed of a polarization film.

9. - . Viewing screen (1) according to any one of the preceding claims, characterised in that both images are simultaneously rendered on the viewing screen (1) .

10. - Viewing screen (1) according to any one of the preceding claims, characterised in that every pixel (2) contains a light-emitting diode or LED or a cluster of several similar light-emitting diodes or LEDs .