Optical device comprising a volume hologram

Abstract

The invention relates to an optical device comprising a volume hologram (2) which diffracts the impinging illuminating light (L1, L2) in such a way that the illuminating light is given off in a predetermined range of angles (6) relative to the volume hologram (2), and comprising a visual protection filter (3), which is located on the volume hologram (2), for suppressing stray light, wherein the illuminating light diffracted by the volume hologram (2) passes through the visual protection filter (3).

Description

[0001] Optical device with a volume hologram

[0002] The present invention relates to an optical device with a volume hologram. Such optical devices are used, for example, for producing displays or screens, since volume holograms allow large deflection angles to be realized in conjunction with a very thin optical element.

[0003] In such volume holograms, the unwanted zeroth diffraction order as well as unwanted stray light often cannot be avoided, resulting in stray light that overall leads to a deterioration of the optical function provided by the volume hologram.

[0004] Based on this, it is therefore the object of the invention to improve an optical device with a volume hologram.

[0005] The invention is defined in claim 1. Advantageous further developments are specified in the dependent claims.

[0006] Surprisingly, the privacy filter arranged on the volume hologram, through which the illumination light diffracted by the volume hologram passes, can suppress the stray light to a large extent.

[0007] A privacy filter (often also called a privacy filter) is known, for example, from the area of ​​laptops to protect the screen from unwanted glances from the side. For this purpose, a corresponding privacy filter is affixed to the screen. The privacy filter thus limits the angular range of the radiation passing through the privacy filter. This fundamentally undesirable restriction in the area of ​​an optical device with a volume hologram is used according to the invention to only allow radiation from the angular range that lies within the predetermined angular range to pass through. This then surprisingly leads to an improved contrast on the one hand. On the other hand, it can also achieve a sharper boundary of the predetermined angular range, which is desirable in many applications. The privacy filter can be designed as a film.In particular, the privacy filter can have transmitting sections and non-transmitting sections (preferably absorbing sections) configured to transmit only radiation from the predetermined angular range (or from, for example, a smaller angular range). For this purpose, non-transmitting slats with a suitable height, a suitable width, and a suitable spacing can be arranged, for example, so that strip-like absorbing and non-absorbing regions are provided alternately.

[0008] The privacy filter therefore only transmits radiation from a specified angle range, which is, for example, less than or equal to 100°, 90°, 80°, 70°, 60°, 50° or 40°.

[0009] However, it is also possible to provide a substantially flat absorbing area in which transmitting sections are formed in a pattern or grid. These can, for example, have a polygonal, round, or oval basic shape. The recesses can thus be formed as cylinders or hollow cylinders in the absorbing material.

[0010] The volume hologram can use a first diffraction order to diffract the incident illumination light into the predetermined angular range and the privacy filter can block light of at least one other diffraction order of the volume hologram (e.g. the zeroth diffraction order).

[0011] In particular, the privacy filter can also block unwanted stray light that is generated, for example, in the volume hologram or in the film of the volume hologram.

[0012] The viewing angle can suppress stray light for certain angle ranges by absorption.

[0013] The volume hologram can be designed as a transmissive volume hologram. However, it is also possible for the volume hologram to have two reflective partial volume holograms. The reflective partial volume holograms can be arranged and designed in such a way that the illumination light is reflected back and forth between them once before passing through the privacy filter.

[0014] The volume hologram can be applied to a transparent carrier. The carrier can have a coupling region through which the illumination light can be coupled into the carrier and then guided to the volume hologram by reflection or total internal reflection. For example, another hologram (e.g., a volume hologram) can be arranged in the coupling region to deflect the beam.

[0015] The volume hologram can be designed as an image hologram. In this case, image information is embodied in the volume hologram in such a way that it is reconstructed by the incident illumination light, making the image perceivable to a viewer. The image thus perceivable can be located within the volume hologram 2 or can be perceivable at a distance from it.

[0016] In particular, the perceivable image can be a virtual image. Furthermore, the perceivable image can include virtual and / or real image content.

[0017] Furthermore, the optical device may comprise an image generation module that generates an image and emits it as illumination light.

[0018] The image generation module can generate a monochrome image or a multi-color image.

[0019] The optical device may further comprise a control unit that controls the image generation module. In particular, the control unit may control the image generation module based on supplied image data.

[0020] The image generation module can, in particular, comprise a planar imager, such as an LCD module, an LCoS module, an OLED module, a pLED, or a tilting mirror array. The planar imager can comprise a plurality of pixels, which can be arranged, for example, in rows and columns. Furthermore, the imager can be self-luminous or non-self-luminous. It is also possible to provide multiple imagers.

[0021] The optical device according to the invention can be used in all technical fields in which images, patterns, and the like are to be displayed and / or in which areas are to be illuminated with light. This can include consumer electronics, home technology, as well as all types of screens, screen surfaces, and displays. In particular, applications in vehicles (on land, at sea, or in the air) are also possible. For example, operating elements, information, images, patterns, and the like can be displayed in this way.

[0022] The volume hologram can, for example, be designed as a technical hologram, which achieves an optical imaging effect and / or an optical deflecting effect. Furthermore, the volume hologram can be designed, for example, as a diffuser. This is particularly advantageous in the case where the image generation module is provided or is part of the optical device.

[0023] 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.

[0024] 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:

[0025] Fig. 1 is a schematic view of a first embodiment of the optical device according to the invention;

[0026] Fig. 2 is a schematic view of the privacy filter 3 of Fig. 1;

[0027] Fig. 3 is a schematic view of a modification of the privacy filter 3 of Fig. 1;

[0028] Fig. 4 is a schematic view of a further modification of the privacy filter 3 of

[0029] Fig. 1 ;

[0030] Fig. 5 is a schematic view of another embodiment of the optical device according to the invention;

[0031] Fig. 6 is a schematic view of another embodiment of the optical device according to the invention; Fig. 7 is a schematic view of another embodiment of the optical device according to the invention;

[0032] Fig. 8 is a schematic view of another embodiment of the optical device according to the invention, and

[0033] Fig. 9 is a schematic view of the design of the light source 5 of Fig. 1 and 5-8 as image generation module 5.

[0034] In the embodiment shown in Fig. 1, the optical device 1 according to the invention comprises a transmissive volume hologram 2 and a privacy filter 3 applied to the volume hologram 2. In the embodiment shown in Fig. 1, the volume hologram 2 and the privacy filter 3 are each designed as a film which is applied to a transparent carrier 4.

[0035] Furthermore, a light source 5 is provided, which emits illumination light. This is schematically represented by beams L1 and L2. The illumination light L1, L2 strikes the transmissive volume hologram 2, which is designed to transmit the first diffraction order as light beams L1' and L2' into a predetermined angular range 7 relative to the volume hologram 2. Thus, a certain deflection of the illumination light L1 and L2 occurs.

[0036] A portion of the illumination light L1 and L2 is not diffracted and would pass through volume hologram 2 as the zeroth diffraction order, as indicated by the dashed lines L1s and L2s. This light L1s and L2s represents unwanted stray light.

[0037] However, due to the privacy filter 3 arranged on the volume hologram 2, the transmission of this stray light L1s and L2s is blocked, as the privacy filter 3 is designed such that only light rays whose propagation direction lies within the privacy filter angular range 6 (hereinafter also referred to as the transmitted angular range 6), which is indicated in Fig. 1 by three arrows, can pass through the privacy filter 3 unhindered. Since the propagation direction of the stray light L1s, L2s does not lie within the transmitted angular range 6, the stray light L1s, L2s is blocked. The transmitted angular range can be symmetrical to a direction perpendicular to the privacy filter 3 (here along the x-direction) and can be + / - 50°, + / - 40°, or + / - 30°. In other words, the transmitted angle range can be less than or equal to 100°, less than or equal to 80° or less than or equal to 60°.This allows for excellent suppression of stray light, resulting in better contrast for the illumination light diffracted in the predetermined angular range.

[0038] The predetermined angular range 7, which is indicated by dashed lines, can also be referred to as eyebox 7, since an observer who positions his eye within this eyebox 7 can perceive the illumination light L1 ', L2' diffracted in the predetermined angular range 7.

[0039] The privacy filter 3 provides the further advantage that stray light SL, which can occur due to unwanted scattering of the light in the film of the volume hologram 2 and which is usually emitted into the entire half-space of the viewer, is limited to the angular range 6 by the privacy filter 3. This is indicated in Fig. 1 by the fact that the part of the stray light SL shown with a dashed line is blocked by the privacy filter 3 and thus does not spread further. This ensures that significantly less light is emitted outside the eyebox 7 compared to the case without the privacy filter 3. This then leads to the volume hologram 2 appearing black or dark when a viewer is outside the eyebox 7.

[0040] The volume hologram 2 may be a so-called technical hologram with which an optical imaging effect and / or an optical deflecting effect is achieved.

[0041] Furthermore, the volume hologram 2 can be a so-called image hologram, in which the image information is encoded into the hologram 2 in such a way that it is reconstructed by the incident illumination light, and the image is perceptible to a viewer. The perceptible image can be perceptible within the volume hologram 2 or at a distance from it.

[0042] The privacy filter 3 can, for example, be designed such that it provides the transmitted angular range 6, for example, in the plane of the drawing in Fig. 1 (i.e., in the xy plane), whereas in a plane perpendicular thereto (e.g., the xz plane) there is no restricted angular range. In this case, the privacy filter 3 can have a plurality of (e.g., absorbing) slats 10, as schematically indicated in Fig. 2. The areas 10 between the slats 10 are transmissive. By suitable selection of the height of the slats 10 (dimensions in the x-direction) as well as the width and spacing of the slats 10 (in the y-direction), the desired transmitted angular range 6 can be set. For example, the slats 10 can have a height of 200 pm, a width of 60 pm, and a spacing of 60 pm. In particular, the height of the slats can be in the range of 100 pm to 300 pm, the width of the slats can be in the range of 30 pm to 90 pm and the pitch can be in the range of 30 pm to 90 pm.

[0043] Of course, the privacy filter 3 can also be designed to restrict the transmitted angular range 6 in several different planes. In this case, the transmitting recesses 11 can be arranged in a grid-like manner, as indicated in Figs. 3 and 4. The basic shape of the recess 11 can be cuboid or cylindrical.

[0044] The slats 10 or the non-transmissive area 10 in the variants according to Figures 3 and 4 can, for example, be colored. In principle, any color is possible. The slats 10 or the non-transmissive area 10 can also have a decorative finish (e.g., a wood look) or pattern. If the volume hologram 2 is not illuminated, only the color or pattern is visible. Even when viewed at an angle (e.g., from outside the eyebox 7), the color or pattern is visible, even if the volume hologram 2 is illuminated.

[0045] In the embodiments described so far, it was assumed that the eyebox 7 runs essentially perpendicular to the volume hologram 2. However, it can also be inclined at a different angle to the volume hologram 2, as schematically indicated in Fig. 5. In this case, only the privacy filter 3 needs to be adjusted so that the transmitted angular range 6 again lies within the predetermined angular range 7. Here, too, stray light suppression occurs, which is not shown to simplify the illustration.

[0046] The optical device 1 can be designed as a display or a screen. In particular, the optical device can be designed as a display device (e.g., a human-machine-driven display) that can be worn on the viewer's head. For this purpose, a holding device can be provided, which, for example, is designed like glasses or a helmet. It is also possible to design the optical device 1 as a display or a screen in a vehicle (on land, on water, and / or in the air).

[0047] Fig. 6 shows a modification of the embodiment of Fig. 1, in which, in contrast to Fig. 1, the illumination light L1, L2 is coupled via the end face 15 of the carrier 4 and guided in the carrier by reflections or total internal reflections to the volume hologram 2. In this case, the zeroth diffraction order L1s, L2s remains in the carrier 4.

[0048] Fig. 7 shows a further modification of the embodiment of Fig. 1. In contrast to Fig. 1, the illumination light L1, L2 is coupled in via the rear side 16 of the carrier 4 (e.g., via a coupling hologram 17 on the rear side 16) and guided in the carrier 4 by reflections or total internal reflections to the volume hologram 2 (which is applied to the front side 18 of the carrier 4). In this case, too, the zeroth diffraction order L1s, L2s remains in the carrier 4.

[0049] In the embodiments according to Figures 6 and 7, the volume hologram 2 is arranged as a transmissive volume hologram 2 on the front side 18. However, it can also be arranged as a reflective volume hologram 2 on the front side 18 or rear side 16.

[0050] Fig. 8 shows a further modification of the embodiment of Fig. 1, in which, in contrast to Fig. 1, the volume hologram has a first reflective volume hologram 2i and a second reflective volume hologram 22. The two reflective volume holograms 2i, 22 are arranged and configured such that the illumination light L1, L2 is reflected back and forth between them once before passing through the privacy filter 3. Such an arrangement of the two reflective volume holograms 21, 22 is also referred to as a z-hologram. Such a hologram type is described in more detail, for example, in DE 10 2021 105 830 A1.

[0051] The light source 5 can, as shown schematically in Fig. 9, be designed, for example, as an image generation module 5 that generates an image that is projected into the predetermined angular range by means of the volume hologram 2, so that a viewer can perceive it when their eye is positioned within the eyebox 7. The perceivable image can then be a real or a virtual image.

[0052] The image generation module 5 may comprise an image generator unit 12 for generating the image.

[0053] For this purpose, the imaging unit 12 comprises a planar imaging element 13, which may, but need not, be followed by an imaging optics system 14. The planar imaging element 13 can, for example, comprise an OLED element, an LCD element, an LCoS element, a pLED, or a tilting mirror matrix, each of which comprises a plurality of pixels arranged, for example, in rows and columns. Light beams L1 and L2 are shown schematically as representative light beams emitted by the planar imaging element 13.

[0054] As can be further seen from Fig. 9, a control unit S with, for example, a processor P and a memory M is provided for controlling the image generation module 5. The control unit S controls the image generation module 5, and in particular the image generation element 13, depending on the supplied image data so that an image is generated according to the image data. If the light source 5 is designed as an image generation module 5, it is advantageous to design the volume hologram 2 as a diffuser or generally as a technical hologram.

Claims

Patent claims 1 . Optical device with a volume hologram (2) which diffracts incident illumination light (L1, L2) such that it is emitted into a predetermined angular range (6) with respect to the volume hologram (2), and a privacy filter (3) arranged on the volume hologram (2) for suppressing stray light, wherein the illumination light diffracted by the volume hologram (2) passes through the privacy filter (3).

2. Optical device according to claim 1, wherein the volume hologram (2) uses a first diffraction order to diffract the incident illumination light (L1, L2) into the predetermined angular range and the privacy filter (3) blocks light of at least one other diffraction order of the volume hologram (2).

3. Optical device according to claim 1 or 2, wherein the privacy filter (3) blocks unwanted stray light.

4. Optical device according to one of the above claims, wherein the privacy filter (3) suppresses the stray light by absorption.

5. Optical device according to one of the above claims, wherein the volume hologram (2) is designed as a transmissive volume hologram (2).

6. Optical device according to one of the above claims, wherein the privacy filter (3) is designed as a transmissive privacy filter (3).

7. Optical device according to one of the above claims, wherein the volume hologram (2) is applied to a transparent carrier (4).

8. Optical device according to claim 7, wherein the carrier (4) has a coupling region via which the illumination light (L1, L2) can be coupled into the carrier and then guided to the volume hologram (2) by means of reflections or total internal reflections.

9. Optical device according to one of the above claims, wherein the volume hologram (2) is designed as an image hologram.

10. Optical device according to one of the above claims, with an image generation module (5) which generates an image and emits it as illumination light (L1, L2).

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