Holographic optical module, holographic display device comprising such a holographic optical module, and method for producing such a holographic optical module

Abstract

The invention relates to a holographic optical module comprising a base body (4), which has a first surface (5), and a plurality of surface elements (10, 10'), each of which has a holographic structure, wherein the plurality of surface elements (10, 10') are arranged on the first surface (5) of the base body (4) such that the surface elements form a continuous surface (6) that provides a specified optical function.

Description

[0001] patent attorneys

[0002] GEYER, FEH N ERS & PARTNERS

[0003] Munich - Jena

[0004] Carl Zeiss Jena GmbH June 2, 2023

[0005] Attorney file: PAT 1250 / 348- PCT

[0006] Holographic optical module, holographic display device with such a holographic optical module and method for producing such a holographic optical module

[0007] The present invention relates to a holographic optical module, a holographic display device comprising such a holographic optical module and a method for producing such a holographic optical module.

[0008] There is a constantly growing demand for large-area display devices that are used, for example, in transparent surfaces such as large window areas, corresponding panes in vehicles or, for example, in glass-door refrigerators in retail stores.

[0009] Classic display devices in retail are based on LCD or OLED, but are usually integrated TVs in the corresponding items, such as

[0010] Furniture. On the one hand, these are not transparent. On the other hand, they are very expensive and require a lot of space, as the electronics for the display must also be included.

[0011] Transparent OLED displays already exist. However, these are very expensive and therefore not economically viable in many areas.

[0012] It is also known that holographic structures on transparent surfaces can be used to provide desired optical properties. For example, this can be used to create diffuser surfaces that can be used for image display. However, the production of such holographic structures is costly and time-consuming, with the costs and time required increasing disproportionately with the size of the desired holographic structures.

[0013] Based on this, it is therefore an object of the invention to provide an optical module that can be used in display devices and with which the discussed difficulties can be avoided as completely as possible. Furthermore, a display device with such an optical module and a method for producing such an optical module are to be provided. The invention is defined in independent claims 1, 15, and 16. Advantageous embodiments are specified in the dependent claims.

[0014] Since the holographic optical module according to the invention forms a coherent surface from the multiple surface elements, the size of the coherent surface thus formed is, in principle, unlimited. Furthermore, the production of such a holographic optical module is more cost-effective and faster, since the surface elements can be produced by replicating a master hologram. This has the advantage that replicating a master hologram can be carried out significantly faster than producing the necessary master hologram. Replicating the master hologram is also significantly more cost-effective than producing the master hologram itself. This results in time and cost savings, allowing even larger coherent surfaces to be produced quickly and cost-effectively.

[0015] A continuous surface is understood here in particular to mean that the multiple surface elements are arranged abutting, partially overlapping, or at a distance from one another that is less than 50%, 40%, 30%, 20%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1% of the maximum dimension of one of the surface elements. For example, in the case of a rectangular surface element, the maximum dimension is a diagonal connecting two corners.

[0016] Furthermore, it is possible that the connected surface is not continuous in all areas. For example, it may contain gaps. However, at least two, three, four, five, six, seven, eight, nine, ten, or more surface elements are always arranged in such a way that they form a continuous surface.

[0017] The arrangement of the plurality of surface elements on the first surface of the base body is understood here in particular to mean that individual surface elements, that at least one individual surface element and at least one already connected partial surface with two or more surface elements or that several already connected partial surfaces with two or more surface elements are arranged on the first surface.

[0018] The first surface of the base body is in particular a surface of a one-piece base body or of a one-piece part of the base body. The first surface can in particular be continuous and smooth. The first surface can preferably be formed without cracks, edges and / or depressions. The first surface of the base body (and in particular of the one-piece base body or of the one-piece part of the base body) is preferably larger in area than each of the multiple surface elements. The first surface is in particular a surface that is not composed of multiple partial surfaces. The first surface is preferably formed as a one-piece surface and / or as a single surface.

[0019] The base body can, for example, be designed as a flat body. In particular, the base body can be designed as a plate. Thus, the base body can be designed as a plane-parallel plate or as a curved plate.

[0020] A plate-shaped design of the base body is characterized in particular by the fact that the base body has at least one flat front side, a flat back side, and an edge (or end face) connecting the front and back sides, which edge has a (particularly significantly) smaller area than the front and back sides due to the plate-shaped design of the base body. One can also say that the distance between the front and back sides and thus the height of the base body is smaller (e.g., less than 10%) than the area (e.g., length and width with a rectangular front and back side or, e.g., diameter with a circular front and back side) of the front and back. The front or back side can be the first surface of the base body.

[0021] The base body is preferably transparent. The base body can be made of glass or plastic, for example. The base body can be designed as a glass pane or a plastic pane. In particular, the base body can be designed as a window surface or pane, as a pane for vehicles or for electric stoves, refrigerators, freezers, washing machines, dryers, dishwashers, etc. (e.g., in retail or household applications).

[0022] The base body can comprise one, two, three, or more plate bodies that are arranged in a stack and connected to one another. The base body can, for example, be designed as a multi-pane insulating glass unit consisting of two or more plate bodies (or panes).

[0023] If the base body has a plurality of plate bodies, each plate body comprises a flat front side and a flat back side and an edge (or end face) connecting the front and back sides, which edge has a (in particular significantly) smaller areal extent than the front and back sides due to the plate-shaped design of the plate body. Each of these front and back sides can be the first surface of the base body. Each surface element can be designed, for example, as a film or as a foil. Plastic (e.g. polycarbonate or polyethylene terephthalate) can be used as the material for such a film or for such a foil. The surface elements can be designed as a single-layer or multi-layer film or as a single-layer or multi-layer foil. The holographic structure of each surface element can be designed, for example, as a holographic film. This alone can form the surface element.The holographic film can also be bonded to another foil or embedded between two foils, resulting in a two- or three-layer surface element. It is, of course, possible for the surface element to have more than three layers, such as four or five layers. The total thickness of each surface element can range from 50 μm to 2 mm.

[0024] In the holographic optics module, at least two of the surface elements can be arranged on the first surface without overlapping. The at least two surface elements can be arranged abutting on the first surface or with a gap between the two surface elements on the first surface. The gap can be filled with an optical cement to form a smooth surface element surface. The cement preferably has a refractive index adapted to the two surface elements.

[0025] It is also possible for a first surface element to be arranged on the first surface with an overlap of a second surface element. In this case, the optical functions provided by the holographic structure of the first and second surface elements can be reduced in the overlap region such that the predetermined optical function in the overlap region is provided by the two reduced optical functions.

[0026] Furthermore, a gap may exist between the first surface element and the first surface in the region of the second surface element due to the overlap. The gap is preferably filled with an optical cement, which in particular has a refractive index adapted to the first surface element.

[0027] Furthermore, an optical putty can be arranged at the edge of the first surface element in the area in which the first surface element lies on the second surface element, so that a step-like edge is avoided and a continuous transition is provided.

[0028] In the holographic optics module, the surface elements can be fixed to the first surface by adhesion or by an adhesive (e.g., an optical cement). The optical cement can, in particular, have a refractive index adapted to the surface elements.

[0029] The surface elements can all have the same shape and size. This creates a tiling (forming connected surfaces) with surface elements that all have the same shape and size.

[0030] Of course, it is also possible to create a tiling pattern using surface elements of two or more different shapes and sizes. The surface elements can be polygons. In particular, the surface elements can have straight edges. However, it is also possible for the surface elements to have curved edges.

[0031] The base body can be transparent. It can also be non-transparent. The first surface can be flat. Furthermore, it is possible for the first surface to be curved.

[0032] The holographic optics module can be transmissive or reflective.

[0033] In the holographic optics module, the holographic structures of two, three, four, five, six, seven, eight, nine, ten, or more surface elements (or of a majority of the surface elements) can each provide the same optical function (or the same optical functionality). It is also possible for the holographic structures of all surface elements of the holographic optics module to provide the same optical function (or the same optical functionality). Together, the surface elements then form the contiguous surface that has the predetermined optical function.

[0034] The optical function (or optical functionality) can, for example, be a diffuser function, so that the multiple surface elements form a coherent diffuser surface.

[0035] Furthermore, the holographic structures of two, three, four, five, six, seven, eight, nine, ten, or more surface elements can have different optical functionalities (in particular, coordinated optical functionalities) to then together form the coherent surface having the predetermined optical function. Of course, the holographic structures of two or more surface elements can have different optical functionalities, and two or more surface elements can have the same optical functionalities (in particular, coordinated optical functionalities) to then together form the coherent surface having the predetermined optical function.

[0036] The predetermined optical function of the connected surface can be, for example, the optical function of a lens (e.g. a spherical and / or aspherical lens, a converging lens or a diverging lens).

[0037] The holographic display device according to the invention can comprise a holographic optical module according to the invention, an image module that generates an image, and an imaging optic that projects the image generated by the image module onto the holographic optical module. The holographic optical module acts as a diffuser surface in which the imaged image is perceivable as a real image (a so-called in-plane image). Thus, the real image is perceivable as an image in the plane of the diffuser surface.

[0038] The image module can in particular be a digital projector which, for example, has an LCD or LCoS module or a tilting mirror matrix as the image generator.

[0039] The imaging optics can have spherical and / or aspherical imaging elements (especially lenses).

[0040] In the method for producing a holographic optical module, at least one master hologram having an optical functionality is produced in a first step. In a second step, the master hologram(s) are replicated (preferably multiple times) to produce a plurality of surface elements, each of which has a holographic structure that has the same optical functionality as the (respective) master hologram. In a third step, a plurality of surface elements are arranged on a first surface of a base body such that the plurality of surface elements form a contiguous surface that provides a predetermined optical function.

[0041] The (respective) master hologram and the surface elements produced by replication can be formed in any suitable material, for example, a plastic material. For example, a PC film (polycarbonate film) or a PET film (polyethylene terephthalate film) can be used with a holographic film in which the master hologram and / or the surface elements produced by replication are created. The holographic film can, in particular, be embedded between two such films (e.g., plastic films), whereby the total thickness can range from 50 μm to 2 mm.

[0042] The arrangement of the plurality of surface elements on the first surface of the base body is understood here in particular to mean that individual surface elements, that at least one individual surface element and at least one already connected partial surface with two or more surface elements or that several already connected partial surfaces with two or more surface elements are arranged on the first surface.

[0043] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

[0044] The invention is explained in more detail below using exemplary embodiments with reference to the attached drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the embodiments may also be applicable to other embodiments.To avoid repetition, identical or corresponding elements in different figures are designated by the same reference numerals and are not explained more than once. The figures show:

[0045] Fig. 1 is a schematic sectional view of a holographic display device integrated in a glass door refrigerator;

[0046] Fig. 2 is a schematic front view of the holographic display device of Fig. 1 integrated in the glass door refrigerator;

[0047] Fig. 3 is a diagram to explain the structure of the diffuser hologram 6 from the multiple surface elements 10; Fig. 4 is a schematic view to explain the manufacturing process of the

[0048] Surface elements 10;

[0049] Fig. 5 to 8 representations to explain possible tilings for providing the diffuser hologram 6;

[0050] Fig. 9 to 12 sectional views to explain various embodiments of the arrangement of the surface elements 10 on the first surface 5;

[0051] Fig. 13 is a schematic diagram to explain the efficiency curve of the optical diffuser functions provided by the surface elements 10 in the overlap area, and

[0052] Fig. 14 is a diagram explaining the possible implementation of a lens function in a diffuser hologram 6.

[0053] A holographic optics module 1 according to the invention can be designed, for example, as a glass door 2 of a glass-door refrigerator 3, as shown schematically in Figs. 1 and 2.

[0054] The glass door 2 comprises a glass pane 4, on the inner side 5 of which a diffuser hologram 6 is arranged. The glass pane 4 can also be referred to as a base body 4, wherein the inner side 5 is a first surface 5 of the base body 4.

[0055] Furthermore, an image module 7, which generates an image, and an imaging optic 8, which images the generated image onto the diffuser hologram 6 (schematically indicated by two light beams L1 and L2 in Fig. 1), are arranged in the glass-door refrigerator 3. As indicated by the arrows P1 and P2 in Fig. 1, the diffuser hologram 6 deflects the light beams L1, L2 such that they pass essentially perpendicularly through the glass pane 4, wherein a predetermined solid angle range is covered by the light beams L1, L2, so that the image generated by the image module 7 on the diffuser hologram 6 is visible to an observer standing in front of the glass-door refrigerator 3. The diffuser hologram 6 thus acts as a ground glass for an image generated by the image module 7 and is preferably transparent when no image of the image module 7 is projected onto the diffuser hologram 6. The diffuser hologram 6 can, as shown in Fig.1 and 2, have a substantially rectangular shape with dimensions of, for example, 700 x 580 mm.

[0056] The optical module 1, together with the image module 7 and the imaging optics 8, which can be designed, for example, as a digital projector, forms a holographic display device 9.

[0057] The glass pane 4 can also be designed as double glazing (in this case, the glass pane 4 comprises two plate bodies, which are made of glass here) and then also comprises the inner pane 4' shown in dashed lines. In this case, the diffuser hologram 6 can be arranged in the space between the two panes, as shown schematically in Fig. 1.

[0058] According to the invention, the diffuser hologram 6 is formed from a plurality of surface elements 10, which all have the same holographic diffuser structure and are arranged on the inner side 5 of the glass pane 4 in such a way that they form a continuous surface which then provides the desired diffuser function.

[0059] As shown in Fig. 3, the surface element 10 can be formed as a hexagon (for example, a regular hexagon). Such hexagons can form a continuous surface if the hexagons 10 are arranged in the manner shown in Fig. 3.

[0060] To produce the surface elements 10, a master hologram M with the desired optical function or functionality (diffuser function) is written in a first step S1 (Fig. 4). The master hologram M can be written in a surface area that completely encompasses the shape of the desired surface element 10, as indicated by the dashed hexagon M'. Alternatively, it is possible for the master hologram M to already have the desired shape of the surface elements 10 to be produced (here, the hexagon shape M').

[0061] In a subsequent replication step S2, the master hologram M or M' is then replicated as often as necessary (three replications R are indicated in Fig. 3) until the desired number of required surface elements 10 is obtained (step S2). If necessary, the replication step S2 includes trimming the replications R to obtain the desired surface elements 10.

[0062] The master hologram M or M' and the replications R can be formed in any suitable material, for example, plastic. For example, a PC (polycarbonate) film or a PET (polyethylene terephthalate) film with a holographic film can be used, in which the master hologram M or M' or the corresponding replication R is created. The holographic film can, in particular, be embedded between two such films, whereby the total thickness can range from 50 pm to 2 mm.

[0063] The surface elements 10 can then be arranged in a stitching step S3 on the inner side 5 of the glass pane 4 such that the entire area of ​​the desired hologram 6 is filled by the surface elements 10 (Fig. 3). The major advantage of this procedure is that the replication step S2 for copying a master hologram (M or M') is significantly shorter than the step S1 for writing a master hologram M or M'. This makes it possible, for example, to significantly reduce the production time for the written hologram 6. A conventional digital exposure for such a size currently takes at least two weeks for the aforementioned hologram size. With an edge length of the regular hexagons in the range of 3 to 6 cm, the time required to produce the hologram 6 can be reduced to approximately four days down to approximately one day using steps S1-S3.

[0064] The shape of the surface element 10 is preferably selected so that a coherent surface can be formed with a single shape and size, as shown by way of example for the regular hexagon in Fig. 3. However, pentagons (Fig. 5) and other shapes with straight edges or curved edges (Figs. 6 and 7) are also possible.

[0065] Furthermore, it is possible to compose the hologram 6 from two or more different surface elements. This is illustrated in Fig. 8 as an example for two different surface elements (hexagon 10 and triangle 10').

[0066] The surface elements 10 can be arranged on the inner side 5 of the glass pane 4, as shown schematically for two surface elements 10 in Fig. 9, in such a way that they abut one another with their end faces.

[0067] Alternatively, as shown in Fig. 10, it is possible to have a gap 11 between the end faces of two directly adjacent surface elements 10. The gap 11 is preferably filled with an optical cement 12 having a refractive index adapted to the surface elements 10.

[0068] Furthermore, as schematically illustrated in Fig. 11, it is possible for two directly adjacent surface elements 10i, 2 to partially overlap. This creates a gap 13 beneath the first surface element 10i, which partially overlaps the second surface element 102. This gap 13 is in turn preferably filled with an optical cement 14 having a refractive index that is matched to the refractive index of the surface elements 10i, 2.

[0069] Fig. 12 shows a further development of the arrangement according to Fig. 11. In this further development, an optical cement 15 is also provided in the region of the end face 15 of the first surface element 10i of the area positioned on the second surface element 2, such that the transition to the top side of the second surface element 102 is as continuous as possible, so that no edge is present through the end face 15 on the top side of the surface elements. This is advantageous for avoiding unwanted scattering at such an edge.

[0070] The first and second surface elements 10i and 102 (and in particular all surface elements 10), when arranged in an overlapping manner, as indicated in Figs. 11 and 12, on the inner side 5 of the glass pane 4, can be designed such that the efficiency E1 and E2 of the holographic diffusion function of the surface elements 10i and 2 decreases in the overlap region, as shown schematically in Fig. 13. In the overlap region, the sum of the efficiencies E1 and E2 is then present, so that the same efficiency is provided there as outside the overlap region by the surface elements 101, 2. This is shown purely schematically in Fig. 13, wherein the efficiency E is plotted in arbitrary units between 0 and 1 and the y-coordinate was assumed as the spatial coordinate.

[0071] By manufacturing the diffuser hologram 6 from smaller surface elements 10, the size of the diffuser hologram 6 is, in principle, not limited. If a larger diffuser hologram 6 is desired, simply arrange more surface elements 10 on the inner side 5 of the glass pane 4.

[0072] Of course, the embodiment of the diffuser hologram 6 on the inner side 5 of the glass pane 4 of a glass refrigerator 3 is merely exemplary. Such a diffuser hologram 6 can be formed on any other surfaces, such as large window surfaces or on corresponding glass surfaces of vehicles, such as cars or trucks.

[0073] The described diffuser hologram 6 is transmissive. Of course, a reflective design of the diffuser hologram 6 is also possible.

[0074] Furthermore, the hologram 6 does not have to be designed as a diffuser hologram, but can implement any other optical function, such as a lens function. Advantageously, such optical functions are implemented in which the individual surface elements 10 each have the same optical function and are thus identical in their optical function.

[0075] A diffuser hologram 6 with a lens function in a predetermined region 20 is shown schematically in Fig. 14, for example, where the predetermined region 20 is indicated by a dashed circle. As a rule, the optical properties of the surface elements 1-107 that implement the lens function are different, so that different master holograms M are required. In the example shown here, the lens function of a converging lens with spherical boundary surfaces is to be implemented, so that a first master hologram can be used for each of the surface elements 10i-10e and a different second master hologram can be used for the surface element 7.

[0076] Of course, it is also possible to produce more than two different surface elements I O1- 7. All surface elements I O1- 7 can also be different, so that the same number of master holograms is required (e.g., as separate master holograms).

[0077] In the previously described embodiments according to Figures 3 to 7, only one type of surface element 10 (same size and same shape) was used to form a large-area hologram 6. However, it is also possible for the surface elements 10, 10' to have two or more different shapes and / or sizes, as described, for example, in connection with Figure 8.

[0078] Furthermore, it's possible that the contiguous area isn't continuous in all areas. For example, it may contain gaps.

[0079] The surface elements 10, 10' can be fixed to the inner side 5 of the glass pane 4 by adhesion. However, it is also possible for them to be fixed to the inner side 5 by means of an optical cement. In this case, the refractive index of the optical cement is again preferably adapted to the refractive index of the surface elements 10, 10'.

[0080] The glass pane 4 is thus a base body with a first surface, with the surface elements 10, 10' arranged on the first surface. The base body is preferably transparent. However, it can also be non-transparent. The first surface 5 can be flat. However, it is also possible for the first surface 5 to be curved.

[0081] The first surface 5 can be an outer surface of the holographic optics module 1 thus formed. However, it is also possible for a further layer (preferably a transparent layer) to be formed on the surface elements 10, 10'.

Claims

Claims: A holographic optical module comprising a base body (4) having a first surface (5) and several surface elements (10, 10') each having a holographic structure, wherein the several surface elements (10, 10') are arranged on the first surface (5) of the base body (4) such that they form a continuous surface (6) which provides a predetermined optical function. A holographic optical module according to claim 1, wherein at least two of the surface elements (10, 10') are arranged without overlap on the first surface (5). A holographic optical module according to claim 1 or 2, wherein a gap (1 1 ) is formed between the at least two surface elements (10, 10') which is filled with optical cement (12) to form a smooth surface element, wherein the cement (12) has a refractive index adapted to the two surface elements (10, 10').A holographic optical module according to any one of the preceding claims, wherein at least two of the surface elements (10, 10') are arranged abutting on the first surface (5). A holographic optical module according to any one of the preceding claims, wherein a first surface element (10i) is arranged on the first surface (5) overlapping a second surface element (2). A holographic optical module according to claim 5, wherein the optical functions provided by the holographic structure of the first and second surface elements (10i, 2) are reduced in the overlap region such that the predetermined optical function in the overlap region is provided by the two reduced optical functions.

7. Holographic optical module according to claim 5 or 6, wherein a gap (13) exists between the first surface element (10i) and the first surface (5) due to the overlap in the area of ​​the second surface element (1 O2), wherein the gap (13) is filled with an optical cement having a refractive index adapted to the first surface element (10i).

8. Holographic optical module according to one of the above claims, wherein at least two of the surface elements (10, 10') are fixed with optical cement on the first surface (5) of the transparent base body (4), the optical cement having a refractive index adapted to the two surface elements (10).

9. Holographic optical module according to one of the above claims, wherein the surface elements (10, 10') have the same shape and size.

10. Holographic optical module according to one of the above claims, wherein the holographic structures of several of the surface elements (10, 10') each provide the same optical function.

11. Holographic optical module according to one of the above claims, wherein the holographic structures of several of the surface elements (10i , 7) provide different optical functions.

12. Holographic optical module according to one of the above claims, wherein the predetermined optical function comprises a planar diffuser function.

13. Holographic optical module according to one of the above claims, wherein the predetermined optical function of the contiguous area comprises a lens function.

14. Holographic optical module according to one of the above claims, wherein the base body (4) comprises at least one plate body comprising a planar front and a planar back (5) and an edge connecting the front and back (5), which, due to the plate-shaped design of the plate body, has a smaller planar extent than the front and back (5), wherein the front or back surfaces are the first surface of the base body (4). Holographic display device, comprising a holographic optical module (1) according to one of the preceding claims, an image module (7) generating an image, and an imaging optic (8) that maps the image generated by the image module (7) onto the holographic optical module (1), which acts as a diffuser surface, wherein the mapped image is perceptible as a real image in the plane of the surface elements (10). Method for manufacturing a holographic optical module comprising the steps of: manufacturing at least one master hologram (M) having optical functionality, Replicating the master hologram(s) (M) to produce several surface elements (10, 10') each having a holographic structure, arranging the several surface elements (10, 10') on a first surface (5) of a base body (4) such that the several surface elements (10) form a connected surface which provides a predetermined optical function.

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