DEVICE FOR IMPROVING THE QUALITY OF AN IMAGE COVERED WITH A SEMITRANSPARENT PHOTOVOLTAIC FILM

Abstract

Problem addressed: how to decrease the loss of visual quality in an image that appears when this image is placed behind a semitransparent photovoltaic sheet or film. Solution: on the one hand, increase the luminosity of the image by depositing a white-coloured or metallic or reflective layer on the side of the photovoltaic cells that is turned towards the image; and on the other hand, by modifying the luminosity, the contrast, and the colour saturation of the image.

Claims

1. A device comprising: an electronic display configured to display an image illuminated by incident light and to reflect at least a part of said light; and a photovoltaic sheet arranged adjacent to a surface of the image that receives the incident light, said photovoltaic sheet being arranged at a non-zero distance above the surface of the image and including (i) luminous transparent areas and (ii) areas covered with photovoltaic cells, one side of the photovoltaic cells being oriented toward the image and configured to receive the part of said light reflected by said image, wherein the entire non-zero distance between the photovoltaic sheet and the surface of the image consists of one of (i) only air and (ii) only a transparent solid material.

2. The device of claim 1, wherein the photovoltaic sheet is flexible.

3. The device of claim 1, wherein the photovoltaic sheet is made from crystalline glass or organic glass.

4. The device of claim 1, wherein the photovoltaic cells are made from crystalline silicon.

5. The device of claim 1, wherein the photovoltaic cells are made from a plurality of photovoltaic layers, wherein at least one of the photovoltaic layers has a thickness that less than its length.

6. The device of claim 1, wherein the photovoltaic sheet has a thickness that is less than its length.

7. The device of claim 1, wherein the photovoltaic cells form a network of strips parallel to one another and separated by transparent strips.

8. The device of claim 1, wherein the transparent solid material has a refractive index greater than 1.

9. The device of claim 1, wherein the electronic display is a liquid crystal display (LCD).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0019] The invention will now be described in more detail through the description of the indexed FIGS. 1 and 2.

[0020] FIG. 1 is a schematic diagram in cross-section of the device according to the invention.

[0021] FIG. 2 is a schematic diagram in cross-section of a variant of the device with a space with a high refractive index between the cells and the image.

[0022] The device forming the subject-matter of the invention (FIG. 1) is made up of an image (7) on which a semitransparent photovoltaic sheet is positioned. The image (7) may be a printed image or an electronic image, for example an LCD image, or an image made up of pixels backlit by mirrors, or the colored surface of any given object, flat or otherwise, such as a wall, tile or table.

[0023] The semitransparent photovoltaic sheet is a transparent sheet (5) made from rigid or flexible, flat or curved crystalline glass or organic glass, on which crystalline or amorphous photovoltaic cells (4) have been arranged, such as, for example, silicon, or a stacking of thin photosensitive and photovoltaic layers, such as, for example CIGS, or organic cells. These cells (4) may be opaque or semitransparent. They are distributed on the surface of the transparent sheet (5) to form opaque areas separated by transparent areas, or they are distributed in the form of networks of geometric figures such as, for example, rectangular and parallel strips separated by transparent strips.

[0024] The photovoltaic cells (4) have two sides, one of which is turned toward the image or toward the object. This side turned toward the image or toward the object is covered with a highly light-reflective layer (3), such as, for example, an ink or white paint or a mirror-effect aluminum or chrome metal deposit. This reflective side (3) is separated from the image (1) or from the surface of the object (1) by a non-zero distance. The space (2) thus created between the reflective side (3) of the photovoltaic cells and the image (1) may comprise air or a transparent material (FIG. 2) such as crystalline glass or organic glass, the refractive index of which is greater than 1.

[0025] The image (1) and the cells (4) which cover it are illuminated by an incident light (6), one part of which is intercepted by the photovoltaic cells (4) and another part of which crosses the transparent areas and illuminates the image (1). Each pixel (7) of the image then diffuses this light in all directions (8, 9, 10). This light diffused by the image either crosses the transparent areas again as far as the observer (9), or is reflected by the reflective sides (3) of the photovoltaic cells (4), or is reflected (10, 11) in the transparent areas (FIG. 2) when two conditions are satisfied: the refractive index of the space (2) between the cells (4) and the image (1) is greater than air, and the angle of incidence of the light ray (10FIG. 2) is greater than the critical angle of the total reflection in the transition from a high-index diopter to a low-index diopter.

[0026] In the case where the light diffused (10FIG. 2) by the image is reflected (11), said light is reflected again toward the image (1) which will reflect it once more. As a result, the light diffused by the image (1, 7) which will pass from the sheet to the observer will be greater in intensity than it would have been if the internal sides of the cells (4) had not been reflective (3). The observer will therefore see a more luminous image (1) than if the internal sides of the cells (4) were absorbent or non-reflective.

[0027] In one particular embodiment of the invention (not shown), and still in order to increase the luminosity emitted by the image (1) and compensate for the loss of light absorbed by the photovoltaic cells (4), the original image (1) is modified notably in its brightness, contrast and color saturation characteristics. In fact, the image (1) receives less light since a part of said light is stopped by the photovoltaic cells (4). The observer will therefore see an image which is darker, less bright than the original image. In order to partially correct this disadvantage, the original digital image undergoes a computer processing which consists in increasing the luminosity of all or some of its pixels. The percentage of this increase in luminosity will be a function of the characteristics of the original image and the percentage of shading of the photovoltaic cells. The same will apply to the contrast and color saturation which will be modified so that the vision of the observer most closely approximates the vision of the original image. The image (1) covered with the photovoltaic sheet (5) will thus produce electricity with a minimum of visual degradation.

[0028] A specific example embodiment will now be described.

[0029] The device according to the invention includes a one-meter-sided, square paper image (1) and a glass sheet (5) having the same dimensions and a thickness of 4 mm, on which a network of parallel strips of thin photovoltaic layers (4) made from amorphous silicon have been deposited, of which the width is 1 mm and the distance separating them is 3 mm.

[0030] The photovoltaic strips (4) are covered on one of the sides (3) with a thin-layer, aluminum deposit which has the property of reflecting more than 60% of the light which it receives. This side (3) which is covered with a reflective layer is turned toward the image (1) and covers it. The distance between the photovoltaic sheet and the image is 1 cm. This space (2) contains air only. The level of cover of the photovoltaic material on the surface of the sheet is 25%. The digital image has been modified before its paper printout (1) by increasing its luminosity by 30% and reducing its contrast by 5%. Thus, the observer looking at the image (1) through the photovoltaic sheet (5) will see an image which has lost very little of its original luminosity. The photovoltaic sheet (5) will produce around 15 watts of electrical power in full sunlight while reproducing an image very similar to the original image.

EXAMPLE ADVANTAGES OF THE INVENTION

[0031] Ultimately, the invention achieves the defined objects. It is particularly suitable for covering an image or an object with a semitransparent photovoltaic sheet or film while reducing the visual degradation of the image.