Lighting device, vehicle light and method for producing a lighting device

Abstract

The invention relates to a lighting device (1), wherein the lighting device (1) comprises a light source (2) for generating an illumination light (5), a primary hologram (3) which can be illuminated by the illumination light (5) to generate a first lighting function (8), and a secondary hologram (4). The secondary hologram (4) is spaced apart from the primary hologram (3) such that it can be illuminated by a reflected portion (5.1) of the illumination light (5) which is reflected, during illumination of the primary hologram (3), by a Fresnel reflection at a boundary face (3.1) of the primary hologram (3).

Description

[0001] LIGHTING DEVICE, MOTOR VEHICLE LIGHT AND METHOD FOR PRODUCING A LIGHTING DEVICE

[0002] The present disclosure relates to a lighting device, e.g., for a motor vehicle, a motor vehicle lamp, and / or a method for producing a lighting device.

[0003] Motor vehicles have various types of lighting devices, e.g., interior lighting, displays and / or exterior lighting devices, whereby the exterior lighting devices usually serve to ensure driving safety, e.g., to illuminate a road ahead in the dark, to ensure visibility for other road users in the dark, and / or to warn or inform other road users (e.g., direction indicators and / or brake lights).

[0004] In addition to these functions, lighting devices are also known that are additionally provided with a characteristic luminous signature. These lighting devices are designed in such a way that the light emitted by the respective lighting device creates a characteristic shape, e.g., company- or manufacturer-specific. This shape can, for example, be three-dimensional.

[0005] One possibility for implementing luminous signatures is the use of holograms, which create holographic images from which the light of the lighting device appears to emanate. This makes it possible to create lighting functions for motor vehicles, such as taillights or brake lights, that appear to originate outside the vehicle and / or to implement characteristic luminous signatures.

[0006] Such illumination devices typically comprise the hologram, which generates the desired luminous signature, and a light source to illuminate the hologram. To achieve an appropriate quality of the luminous signature, the reconstruction of the holograms used must exhibit certain parameters, e.g., a narrow angular and spectral distribution, as well as a small deviation from the design parameters. This places high demands on the light-shaping optics that generate such a reconstruction light wave. The combination of at least one light-emitting diode as a light source results in a relatively high light loss, since only a small portion of the original light is used for reconstruction.

[0007] Against the background of this prior art, the object of the present disclosure is to provide a device which is each suitable for enriching the prior art.

[0008] The problem is solved by the features of the independent claims. The subclaims each contain optional developments of the disclosure.

[0009] The task is then solved by a lighting device, e.g. for a motor vehicle.

[0010] The lighting device comprises a light source for generating an illuminating light.

[0011] The lighting device comprises a primary hologram that can be illuminated by the illumination light (or optionally a first portion of the illumination light) to generate a first lighting function. In other words, the primary hologram can be arranged such that it can be illuminated or illuminated by the illumination light (or optionally the first portion) and / or the illumination light falls on the primary hologram. The primary hologram can be configured to generate a first lighting function by means of the illumination light, e.g., by deflecting (at least a portion) of the illumination light (or optionally the first portion). Subsequently, the illuminability or illumination of the primary hologram by the illumination light can include the primary hologram being illuminable or illuminated (only) by a first portion of the illumination light.

[0012] The lighting device comprises a secondary hologram which is arranged (and optionally aligned) at a distance from the primary hologram such that it can be illuminated by a reflected portion of the illumination light (or optionally of the first portion) which, when the primary hologram is illuminated, is reflected by a Fresnel reflection at a boundary surface of the primary hologram.

[0013] The primary hologram can also be referred to as a (primary) holographic grating. Similarly, the secondary hologram can also be referred to as a (secondary) holographic grating.

[0014] Furthermore, a lighting device is provided, wherein the lighting device comprises a light source for generating an illumination light. Furthermore, the lighting device comprises a primary hologram, which can be illuminated by the illumination light to generate a first lighting function, and a secondary hologram. The primary hologram is a reflection hologram. The secondary hologram is arranged at a distance from the primary hologram such that the secondary hologram can be illuminated by a reflected portion of the illumination light, which, when the primary hologram is illuminated, is reflected by a Fresnel reflection at an interface of the primary hologram.

[0015] A hologram or volume hologram can be understood as a (phase) grating, i.e. a light-sensitive volume material in which a refractive index or refractive indices have been specifically changed locally (e.g. by holographic exposure). This structure leads to local phase changes of an incoming light wave and thus causes the incoming light wave to be diffracted or redirected in a specific direction. By illuminating a hologram with light, the image information contained in the hologram can be reproduced. Such illumination can also be referred to as reconstruction. A holographic function of a hologram determines how the hologram modifies incident light, for example to reproduce image information.

[0016] In general, any optical function can be realized using a hologram. The degree of freedom in optical design is significantly higher with a hologram than with conventional solutions, e.g., using lenses, mirrors, and the like.

[0017] A hologram can generally be wavelength- and / or angle-selective. This selectivity can be specifically adjusted through the design of the hologram, e.g., through the thickness of the hologram and the angle at which the exposure occurs to reproduce the image information contained in the hologram during its production. These properties can be used to design the emission characteristics of a light source, e.g., at least one light-emitting diode. Wavelength selectivity and / or angle selectivity allow beam shaping and color filtering to be combined in a hologram.

[0018] For such beam shaping and / or filtering functions, transmission and / or reflection holograms (or transmission and / or reflection gratings) can be used.

[0019] The fact that a hologram can be illuminated by an illuminating light means that the hologram is illuminated by the illuminating light when the illuminating device, optionally installed in a motor vehicle, is used as intended. The fact that the secondary hologram can be illuminated by a reflected portion of the illuminating light, which is reflected by a Fresnel reflection at an interface of the primary hologram when the primary hologram is illuminated, means that when the illuminating device is used as intended, the secondary hologram is illuminated by the light reflected by a Fresnel reflection at an interface of the primary hologram, while the primary hologram is illuminated.In other words, the term "illuminable" is to be interpreted such that the illuminating device is designed such that the primary hologram is illuminated by the illuminating light and that the illuminating device is designed such that the secondary hologram is illuminated by a reflected portion of the illuminating light which, when the primary hologram is illuminated, is reflected by a Fresnel reflection at a boundary surface of the primary hologram.

[0020] A Fresnel reflection at an interface of the primary hologram is a reflection at an interface of the primary hologram where the refractive index of the optical medium changes. The Fresnel reflection is caused by the change in the refractive index of the optical medium. During Fresnel reflection at the interface of the primary hologram, the illumination light is reflected equally across its entire spectral bandwidth, without the transmission or reflection wavelength of the primary hologram having an effect on the reflectivity of the interface of the primary hologram caused by the Fresnel reflection.

[0021] The lighting device described above offers a number of advantages. Among other things, it enables improved and more effective use of the light generated by the light source, whereby at least a portion of the light that is usually lost unused can be captured by the secondary hologram for further purposes.

[0022] For example, holograms, such as freestanding reflection holograms, typically exhibit Fresnel reflections at a respective interface or front surface upon which an incoming light or light wave impinges. Fresnel reflections are a well-known phenomenon. These reflections depend, among other things, on the angle of incidence of the light, the polarization of the light, and the refractive index(es) of the media at the interface, and can be described by the well-known Fresnel formulas. This light reflected by Fresnel reflections does not contribute to the generation of a respective luminous function, e.g., the generation of a holographic image.

[0023] The present disclosure now offers the possibility of capturing such a light component, which is reflected by the primary hologram through Fresnel reflections, by the secondary hologram in order to forward it for further use, for example, or to use it for another lighting function.

[0024] Furthermore, the reflected light of the Fresnel reflection has the same spectral distribution as the light used to generate the first luminous function, so that it is advantageously possible to achieve another luminous function with the same color representation.

[0025] By adjusting the angle of incidence of the illuminating light onto the primary hologram, it is possible to control how much of the illuminating light is coupled into the primary hologram (or the hologram material of the primary hologram) (via the relationship between the Fresnel formulas). This makes it possible to control how much light or radiant power of the illuminating light can (potentially) be diffracted by the primary hologram. This can also determine how much light is available to reconstruct the secondary hologram (i.e. the reflected portion or the Fresnel reflection of the primary hologram). Furthermore, by varying the angle of incidence of the illuminating light onto the primary hologram, the degree and composition of polarization can be influenced accordingly. This can apply analogously to the secondary hologram, since a Fresnel reflection can also occur there. Depending on the exposure orAt different reconstruction angles, the two holograms diffract s-polarized and p-polarized light with different efficiencies (s-polar is generally more efficient than p-polar). By cleverly combining these two relationships, the brightness of the holographic images reconstructed by the two holograms can be controlled or adjusted to each other. The size of the refractive index modulation should, if possible, be chosen so that the light predominantly ends up in the 1st order of diffraction (useful order) and not in the 0th order of diffraction (unless one deliberately wants to use this, for example, for additional illumination). By varying the size of the refractive index modulations of the primary and secondary holograms, the brightness of the holographic images reconstructed by the two holograms can also be adjusted, but with the disadvantage that a lot of light ends up in a potentially unused 0th order of diffraction.

[0026] Possible further developments of the lighting device described above are explained in detail below.

[0027] The secondary hologram can be configured to generate a second luminous function in response to illumination by the reflected portion. In other words, the secondary hologram can be configured to generate a second luminous function by means of the reflected portion, e.g., by deflecting (at least a portion of) the reflected portion.

[0028] The first illumination function can be the generation (or reconstruction) of a first holographic image (or a first light signature). A first image can be recorded in the primary hologram, which defines the first holographic image or the first light signature and at least partially redirects and / or reflects the illumination light in or on the primary hologram to generate the first holographic image. The first holographic image can be generated or generated outside the illumination device, e.g., in a free-floating manner.

[0029] The second illumination function can be the generation (or reconstruction) of a second holographic image (or a second light signature). A second image can be recorded in the secondary hologram, which defines the second holographic image or the second light signature and redirects and / or reflects the reflected portion of the illumination light (at least partially) in or on the secondary hologram to generate the second holographic image. The second holographic image can be generated or can be generated outside the illumination device, e.g., freely suspended.

[0030] Thus, two separate holographic images can be created (or two separate holograms can be reconstructed) using the illuminating light, whereby the light of both images has the same spectral distribution and thus the same color representation.

[0031] The primary hologram and the secondary hologram may be configured to generate the first holographic image and the second holographic image in a same direction.

[0032] The primary hologram and the secondary hologram may be configured to generate the first holographic image and the second holographic image such that the first holographic image and the second holographic image are simultaneously perceivable by a viewer.

[0033] The secondary hologram may be arranged facing the interface of the primary hologram.

[0034] The primary hologram can be arranged between the secondary hologram and the light source.

[0035] The primary hologram can be a reflection hologram. It is also conceivable that the primary hologram can be a transmission hologram. The secondary hologram can be a transmission or reflection hologram.

[0036] The light source and the primary hologram can be arranged relative to one another such that the illumination light falls directly onto the primary hologram, e.g., at an angle or angular range for which the primary hologram is designed to generate the first luminous function. Alternatively, the illuminating device can comprise an optical component. The optical component can be configured to redirect the illumination light toward the primary hologram.

[0037] The optical component can be configured to redirect the illumination light toward the primary hologram at an angle or angular range for which the primary hologram is designed to generate the first luminous function. In other words, the optical component can be configured and / or arranged such that the illumination light falls on the primary hologram at the (predetermined) angle or angular range. The (predetermined) angle or angular range can be selected such that the primary hologram generates the holographic image in response to being illuminated by the illumination light.

[0038] The optical component can be designed in such a way as to redirect only a wavelength-selective portion of the illumination light in a light wavelength range for which the primary hologram is designed to generate the first luminous function, in the direction of the primary hologram.

[0039] The optical component can have a collimation function. The collimation function can be understood as collimating the light rays of the illumination light, or at least emitting or redirecting them with modified divergence angles from the optical component. This can improve the beam quality of the illumination light and allow the illumination light to be used by the primary hologram with the greatest possible efficiency.

[0040] The optical component can comprise a reflection hologram and / or a transmission hologram. Configuring the optical component using at least one hologram advantageously enables a more compact arrangement than a solution using, for example, a mirror. It is conceivable for the optical component to comprise multiple hologram elements and optionally at least one (non-holographic) optical component. The optical component can comprise, for example, a waveguide substrate (e.g., made of glass or a transparent plastic), an input hologram for coupling the illumination light into the waveguide substrate, and an output hologram for coupling the first or second portion (and optionally the first or second additional portion) out of the waveguide substrate.By providing a waveguide substrate in conjunction with the input coupling hologram and the output coupling hologram, it is advantageously possible to achieve essentially any arrangement of the optical component relative to the primary hologram and thus to achieve the most optimized use of available installation space.

[0041] The input hologram and the output hologram can each be designed as a wave-selective reflection hologram and / or transmission hologram.

[0042] The output hologram can be arranged on a side of the waveguide substrate facing the primary hologram or on a side of the waveguide substrate facing away from the primary hologram.

[0043] The coupling hologram can be arranged on a side of the waveguide substrate facing the light source or on a side of the waveguide substrate facing away from the light source.

[0044] The light source can, for example, comprise at least one light-emitting diode, at least one white light source, and / or at least one RGB light source (i.e., a light source that has light sources for red, green, and blue light and generates a total light formed by superposition with the corresponding spectral colors red, green, and blue). The lighting device can comprise at least one further optical component, e.g., a collimator, which can be arranged between the light source and the optical component (or between the light source and the primary hologram).

[0045] The primary hologram and / or the secondary hologram can be interchangeable. This advantageously simplifies the manufacture or assembly of the illumination device for different holographic images.

[0046] The lighting device may comprise a housing in which the light source, the primary hologram, and optionally the optical component are arranged, e.g., mounted. The primary hologram and / or the optical component may be replaceably mounted in the housing.

[0047] The lighting device can be designed as a structural unit. This advantageously allows the lighting device to be pre-assembled and functional, allowing final assembly for the desired purpose, e.g., in a motor vehicle, to be carried out as simply and quickly as possible.

[0048] The lighting device can be designed as a lighting device (e.g. as a rear lighting device) for a motor vehicle or as part of a motor vehicle lamp.

[0049] The lighting device may comprise a hologram array that can be illuminated by the illumination light. In other words, the hologram array may be arranged such that it is illuminated by the illumination light and / or the illumination light falls onto the hologram array.

[0050] The hologram arrangement may be configured to separate the illumination light into a first portion for generating a holographic image (and / or a luminous signature) and a second portion for generating a third (optionally non-holographic) luminous function (and / or to output it in different directions).

[0051] The hologram arrangement offers a number of advantages. Among other things, it enables improved and more effective use of the light generated by the light source. For example, a portion of the light that would normally be lost unused can be used for other purposes, such as additional lighting effects and / or lights. Thus, the illumination light can advantageously be divided into at least two portions, which can, for example, be optimized such that as little light as possible from the first portion is lost unused without contributing to the generation of the holographic image. Instead, this light can be assigned to the second portion during the division, thereby creating the third lighting function.

[0052] The use of the hologram arrangement to split the illumination light also advantageously enables a more compact arrangement than a solution using, for example, mirrors and / or lenses.

[0053] The lighting device may comprise a (e.g., non-holographic) optical element that may be configured to generate the third lighting function, e.g., additional illumination, in response to illumination of the optical element by the second portion. The optical element may be configured to generate the third lighting function by means of the second portion, which illuminates the optical element and / or is incident on the optical element, e.g., by deflecting (at least a portion) of the second portion.

[0054] The hologram arrangement may comprise the primary hologram. The primary hologram may be configured to generate (and / or reconstruct) the first luminous function, e.g., the generation of the first holographic image, using the first portion of the illumination light, e.g., by redirecting and / or reflecting the first portion. The primary hologram may be illuminable by the illumination light. In other words, the primary hologram may be arranged such that it is illuminable or can be illuminated by the illumination light and / or the illumination light falls on the primary hologram. The primary hologram may be configured to separate the illumination light into the first portion and the second portion. The primary hologram may be configured to output the second portion toward the optical element.

[0055] The primary hologram can contain the image that defines the first holographic image or the first light signature and redirects and / or reflects the first portion (at least partially) in or on the primary hologram to generate the first holographic image. The first holographic image can be generated or created outside the lighting device, e.g., freely suspended.

[0056] The primary hologram can be designed such that the second portion passes through the primary hologram without deflection. The primary hologram can be transparent to the second portion. The second portion can comprise the zero-order illumination light (or light rays of the illumination light) or consist of the zero-order illumination light.

[0057] The primary hologram can be arranged between the light source and the optical element.

[0058] The primary hologram can be illuminated with the illumination light on a first side of the primary hologram. The optical element can be arranged on a second side of the primary hologram opposite (or facing away from) the first side.

[0059] The hologram arrangement may comprise a tertiary hologram that can be illuminated, e.g., directly, by the illumination light. In other words, the tertiary hologram may be arranged such that it is or can be illuminated by the illumination light and / or the illumination light falls on the tertiary hologram.

[0060] The tertiary hologram can be arranged instead of or in addition to the optical component.

[0061] The tertiary hologram can be configured to separate the illumination light into the first portion and the second portion (and / or output it in different directions). The tertiary hologram can be configured to output the first portion toward the primary hologram and the second portion toward the optical element. The tertiary hologram can split the illumination light into the multiple portions for more efficient use. The tertiary hologram also advantageously enables a more compact arrangement than a solution using, for example, a mirror.

[0062] The tertiary hologram can be configured and / or the tertiary hologram and the primary hologram can be arranged relative to one another such that the first portion falls on the primary hologram at a (predetermined) angle or angular range. The angle or angular range can be selected such that the primary hologram generates the first holographic image in response to illumination by the first portion. In other words, the angle or angular range can correspond to a (e.g., desired) angle or angular range for which the primary hologram is designed to generate the first holographic image. This arrangement allows the first portion to be advantageously optimized for an angular range so that as little light from the first portion as possible is lost unused, e.g., light that passes through the primary hologram or is reflected by the primary hologram without contributing to the first holographic image.In addition, the contrast or sharpness of the first holographic image can be improved.

[0063] The tertiary hologram can be configured to separate the illumination light wavelength-selectively into the first portion and the second portion. The first portion can comprise light wavelengths from one wavelength range, and the second portion can comprise light wavelengths outside the wavelength range. The wavelength range can correspond to a wavelength range for which the primary hologram is designed to generate the first holographic image. This allows the first portion to be optimized so that as little light from the first portion as possible is lost unused without contributing to the first holographic image. Furthermore, this can improve the contrast or sharpness of the first holographic image.

[0064] The wavelength-selective separation of the first and second components also advantageously implements a spectral filter function through the tertiary hologram. This makes it possible, for example, to use broadband light sources without having to provide separate (spectral) filters.

[0065] The tertiary hologram can be configured to separate the illumination light into the first and second portions, such that the first portion is redirected toward the primary hologram and the second portion passes through the tertiary hologram without redirection. The tertiary hologram can be transparent to the second portion (or, for example, to light wavelengths outside the wavelength range). In other words, the tertiary hologram can be configured to redirect and / or reflect only the first portion or light with wavelengths within the wavelength range.

[0066] The light source, the tertiary hologram and the optical element can be arranged in alignment with each other or along a common axis, wherein the tertiary hologram can be arranged between the light source and the optical element.

[0067] Alternatively, the tertiary hologram can be configured to separate the illumination light into the first and second portions such that the first portion passes through the tertiary hologram without deflection, and the second portion is deflected toward the optical element. The tertiary hologram can be transparent to the first portion (or, for example, to light wavelengths within the wavelength range). In other words, the tertiary hologram can be configured to deflect and / or reflect only the second portion or light with wavelengths outside the wavelength range.

[0068] The light source, the tertiary hologram and the primary hologram can be arranged in alignment with each other or along a common axis, whereby the tertiary hologram can be arranged between the light source and the primary hologram.

[0069] The lighting device may comprise an additional light source for generating additional illumination light.

[0070] The tertiary hologram can be illuminated by the additional illumination light. The tertiary hologram can be configured to separate the additional illumination light into a first additional portion and a second additional portion. The tertiary hologram can be configured to output the first additional portion toward the primary hologram and the second additional portion toward the optical element.

[0071] For example, the tertiary hologram can be designed to separate the additional illumination light into the first additional portion and the second additional portion such that the first additional portion is deflected (or reflected) towards the primary hologram and the second additional portion passes through the tertiary hologram without deflection (or is transmitted by the tertiary hologram without deflection).

[0072] Alternatively, the tertiary hologram can be designed to separate the additional illumination light into the first additional portion and the second additional portion such that the first additional portion passes through the tertiary hologram without deflection (or is transmitted by the tertiary hologram without deflection) and the second additional portion is deflected (or reflected) towards the optical element.

[0073] The tertiary hologram can be arranged to be illuminated simultaneously by the light source and the additional light source. The tertiary hologram can be designed to superimpose the first portion and the first additional portion and / or output them simultaneously in the direction of the primary hologram. Analogously, the tertiary hologram can be designed to superimpose the second portion and the second additional portion and / or output them simultaneously in the direction of the optical element. By simultaneously illuminating the tertiary hologram by the light source and the additional light source and thereby simultaneously outputting the first portion and the first additional portion or the second portion and the second additional portion, e.g. as respectively superimposed light, the respective light intensities for the various functions, i.e. the generation of the first holographic image and the third luminous function, can be advantageously increased.Furthermore, it is conceivable to add further light properties and / or functions by illuminating with the additional light source, e.g., different colors and / or the generation of another holographic image.

[0074] The tertiary hologram can be configured to separate the additional illumination light wavelength-selectively into the first additional portion and the second additional portion. The first additional portion can comprise light wavelengths from the wavelength range, and the second additional portion can comprise light wavelengths outside the wavelength range.

[0075] The lighting device can be configured to generate a first holographic image of different colors and / or a third lighting function of different colors, e.g., a third lighting function with yellow and red light. For this purpose, the illumination light and the additional illumination light can have different light colors and / or different wavelength ranges. Alternatively, or additionally, the tertiary hologram can be configured to form, through the first portion and the first additional portion, an illumination for generating the first holographic image with multiple light colors and / or different wavelength ranges. The first portion and the first additional portion can have different light colors and / or wavelength ranges from one another.Furthermore, alternatively or additionally, the tertiary hologram can be configured to form, through the second portion and the second additional portion, an illumination for generating the third luminous function with multiple light colors and / or different wavelength ranges. The second portion and the second additional portion can have different light colors and / or wavelength ranges from one another.

[0076] The tertiary hologram can be designed to generate illumination with multiple colors and / or different wavelength ranges, e.g., illumination with yellow and red light, by means of the second portion and the second additional portion.

[0077] The tertiary hologram can comprise a (wave-selective) reflection hologram and / or a transmission hologram with a collimation function or can be designed as a reflection hologram and / or a transmission hologram with a collimation function. The transmission hologram can be a transmission hologram with edge illumination (also: edgelit transmission hologram) and / or the reflection hologram can be a reflection hologram with edge illumination (also: edgelit

[0078] reflection hologram). The tertiary hologram may comprise a waveguide substrate.

[0079] The collimation function can be understood as meaning that light rays of the first portion and / or the second portion (and optionally the first additional portion and / or the second additional portion) are collimated or at least output from the tertiary hologram with modified divergence angles. This can improve the beam quality of the respective portion and allow the respective portion to be utilized by the primary hologram or the optical element with the greatest possible efficiency.

[0080] It is conceivable that the tertiary hologram comprises a plurality of hologram elements and optionally at least one (non-holographic) optical element. The tertiary hologram can, for example, comprise a waveguide substrate (e.g., made of glass or a transparent plastic), an input hologram for coupling the illumination light into the waveguide substrate, and an output hologram for coupling the first or second portion (and optionally the first or second additional portion) out of the waveguide substrate. The output hologram can, for example, be configured to output the first portion in the direction of the primary hologram, while the second portion passes through the waveguide substrate without deflection. Alternatively, the output hologram can be configured to output the second portion in the direction of the optical element, while the first portion passes through the waveguide substrate without deflection.

[0081] By providing a waveguide substrate in conjunction with the input hologram and the output hologram, it is advantageously possible to achieve essentially any arrangement of the tertiary hologram relative to the primary hologram and thus the most optimized use of available installation space.

[0082] The input hologram and the output hologram can each be designed as a wave-selective reflection hologram and / or transmission hologram.

[0083] The output hologram can be arranged on a side of the waveguide substrate facing the primary hologram or on a side of the waveguide substrate facing away from the primary hologram. The input hologram can be arranged on a side of the waveguide substrate facing the light source or on a side of the waveguide substrate facing away from the light source.

[0084] The optical element may comprise a light guide and / or a light diffuser. The light diffuser may be designed to (e.g., broadly) illuminate an object.

[0085] The optical element can, for example, comprise a light guide for coupling and transmitting the second portion (and optionally the second additional portion) and a light diffuser for coupling the second portion (and optionally the second additional portion). The light guide and the light diffuser can be formed as a single piece and optionally from the same material.

[0086] The tertiary hologram and / or the optical element can be replaceable and / or arranged, e.g. fixed, in the housing (of the lighting device).

[0087] Furthermore, a motor vehicle lamp, e.g., a motor vehicle tail lamp, is provided, wherein the motor vehicle lamp comprises the lighting device described above. The third lighting function can be used (and / or configured) as a tail light, a brake light, and / or a lighting device for a vehicle license plate.

[0088] What has been described above with reference to the lighting device also applies analogously to the motor vehicle lamp and vice versa.

[0089] Furthermore, a method for producing a lighting device, e.g. the lighting device described above, is provided.

[0090] The method comprises providing a light source, a primary hologram, and a secondary hologram. The light source is configured to generate an illumination light, and the primary hologram is configured to generate a first luminous function.

[0091] The method comprises arranging and aligning the light source and the primary hologram relative to one another such that the primary hologram can be illuminated or is illuminated by the illuminating light to generate the first luminous function.

[0092] The method comprises arranging and aligning the secondary hologram at a distance from the primary hologram such that the secondary hologram is illuminable or is illuminated by a reflected portion of the illumination light which, when the primary hologram is illuminated, is reflected by a Fresnel reflection at an interface of the primary hologram.

[0093] Arranging and aligning the light source and the primary hologram may, for example, include determining a position (and orientation) of the primary hologram (e.g., relative to the light source) in which the first luminous feature (e.g., a first holographic image) has maximum light intensity, maximum contrast, and / or maximum image sharpness while the light source generates the illumination light and illuminates the primary hologram.

[0094] Arranging and aligning the secondary hologram may, for example, comprise determining a position (and orientation) of the secondary hologram relative to the primary hologram in which a second luminous function (e.g., a second holographic image) generated by the secondary hologram has a maximum light intensity, a maximum contrast, and / or a maximum image sharpness while the primary hologram is illuminated by the illuminating light and generates the first luminous function.

[0095] The method may further comprise providing an optical component for redirecting the illumination light toward the primary hologram. Arranging and aligning the light source and the primary hologram may comprise arranging and aligning the optical component, e.g., determining a position (and orientation) of the optical component (e.g., relative to the light source and the primary hologram) in which the illumination light is redirected such that the first luminous function generated by the primary hologram has maximum light intensity, maximum contrast, and / or maximum image sharpness while the light source generates the illumination light and illuminates the optical component.

[0096] The Fresnel formulas determine the proportion of the light incident on the primary hologram when illuminated, which is Fresnel-reflected depending on the angle and polarization and is available for reconstructing the secondary hologram. The proportion of the Fresnel-reflected portion of the illuminating light can depend on the polarization and / or the angle of incidence of the illuminating light on the interface of the primary hologram. The angle of incidence can be the angle between the wave vector of the illuminating light incident on the respective hologram and the surface normal of the interface of the respective hologram.

[0097] For s-polarized illumination light, the proportion of Fresnel-reflected light can be greater than for p-polarized illumination light. If one wishes to increase or maximize the proportion of Fresnel-reflected light in the illumination light, s-polarized illumination light can be advantageous. For p-polarized illumination light, the proportion of Fresnel-reflected light can be lowest. For unpolarized or elliptically polarized light, the proportion of Fresnel-reflected light can lie between the two extremes.

[0098] Optionally, the proportion of Fresnel-reflected light can be further influenced by applying a coating to the primary hologram, e.g., a dielectric coating on the interface. Optionally, the proportion of Fresnel-reflected light can be increased for one or more polarization directions using a coating.

[0099] For the situation of reconstructing the primary hologram at an angle of incidence of the illumination light on the interface of less than 70°, using s-polarized illumination light results in a Fresnel-reflected light fraction of approximately 30%. If the hologram is reconstructed with Fresnel-reflected light at an angle of incidence of less than 30°, the Fresnel-reflected light fraction is approximately 6%. Assuming diffraction efficiencies of more than 90% for both the primary and secondary holograms, an intensity ratio of approximately 2.5:1 between the first orders of the primary and secondary holograms is achievable.

[0100] When using unpolarized or p-polarized illumination light, the intensity ratio is larger, such as 5.5:1 or 22:1.

[0101] The intensity ratio can be adjusted by reducing the diffraction efficiency of the primary hologram. This can allow achieving an intensity ratio of 1:1.

[0102] Optionally, an intensity ratio of 1:1 can be achieved with an angle of incidence of the illumination light of approximately 80° on the primary hologram and an angle of incidence of <20° on the secondary hologram, even at maximum diffraction efficiency, whereby the illumination light preferably has an s-polarization.

[0103] An intensity ratio of 1:1 can offer the advantage that a reconstruction of the primary hologram and a reconstruction of the secondary hologram have approximately the same brightness.

[0104] The above description with reference to the lighting device and motor vehicle lamp applies analogously to the method, and vice versa. Optional embodiments are described below with reference to the figures.

[0105] Fig. 1 shows schematically the lighting device according to an optional embodiment;

[0106] Fig. 2 shows a flow chart of a method for manufacturing the lighting device; and

[0107] Fig. 3 shows schematically the lighting device according to a further optional embodiment; and

[0108] Fig. 4 shows a schematic diagram with transmission and reflection coefficients as a function of the angle of incidence.

[0109] Figure 1 shows, purely schematically, the lighting device 1 according to an optional embodiment. The lighting device 1 comprises a light source 2 for generating an illumination light 5, a primary hologram 3, and a secondary hologram 4. The primary hologram 3 can be, for example, a reflection hologram. The secondary hologram 4 can be, for example, a transmission or reflection hologram.

[0110] The primary hologram 3 is arranged such that it can be illuminated by the illumination light 5 to generate a first luminous function 8, e.g. a first holographic image.

[0111] The secondary hologram 4 is arranged at a distance from the primary hologram 3 such that it can be illuminated by a reflected portion 5.1 of the illumination light 5, which, when the primary hologram 3 is illuminated, is reflected by a Fresnel reflection at an interface 3.1 of the primary hologram 3. The secondary hologram 4 can be configured to generate a second illumination function 9, e.g., a second holographic image, in response to illumination by the reflected portion 5.1.

[0112] If the first lighting function 8 involves generating a first holographic image and the second lighting function 9 involves generating a second holographic image, the primary hologram 3 and the secondary hologram 4 can be designed to generate the first holographic image and the second holographic image in a same direction and / or to generate them in such a way that the first holographic image and the second holographic image are simultaneously perceivable by a viewer.

[0113] The secondary hologram 4 is arranged facing the interface 3.1 of the primary hologram 3, wherein the primary hologram 3 is arranged between the secondary hologram 4 and the light source 2.

[0114] The lighting device 1 further comprises an optical component 6 configured to redirect the illumination light 5 toward the primary hologram 3. Additionally, a collimator 7 can be arranged between the light source 2 and the optical component 6.

[0115] As an alternative to the optical component 6, it is also conceivable that the light source 2 can illuminate the primary hologram 3 directly with the illumination light 5.

[0116] The optical component 6 can be configured to redirect the illumination light 5 toward the primary hologram 3 at an angle or angular range for which the primary hologram 3 is designed to generate the first illumination function 8. A desired angular range can thereby be selected so that the amount of light of the illumination light 5 that does not contribute to the first illumination function 8 and also, for example, passes through the primary hologram 3 without reflection and is thus lost unused, is minimized. To further increase the efficiency of the illumination light 5, the optical component 6 can further have a collimation function so that the light rays of the illumination light 5 are emitted as uniformly as possible and accordingly impinge on the primary hologram 3 as uniformly as possible.

[0117] Furthermore, the optical component 6 can be configured to redirect only a wavelength-selective portion of the illumination light 5 in a light wavelength range for which the primary hologram 3 is designed to generate the first luminous function 8, toward the primary hologram 3. This, in turn, allows the redirected portion of the illumination light 5 to be optimized so that as little light as possible from the redirected portion is lost unused.

[0118] The optical component 6 can also consist of at least one hologram and, for example, have at least one reflection hologram and / or one transmission hologram.

[0119] The lighting device 1 according to the present disclosure, e.g., the previously described embodiment, can be designed as a structural unit. Furthermore, the lighting device 1 can be designed for a motor vehicle, e.g., as a rear light device. Accordingly, the lighting device 1 can also be designed as part of a motor vehicle light, e.g., a motor vehicle rear light.

[0120] Figure 2 shows a method 100 for producing the lighting device 1 merely by way of example.

[0121] In a first method step S1, the light source 2, the primary hologram 3 and the secondary hologram 4 are provided.

[0122] In a second method step S2, the light source 2 and the primary hologram 3 are arranged and aligned with each other in such a way that the primary hologram 3 can be or is illuminated by the illumination light 5 to generate the first luminous function 8.

[0123] For this purpose, a position and orientation of the primary hologram 3 can be determined in which the first luminous function 8, e.g. the first holographic image, has a maximum light intensity, a maximum contrast and / or a maximum image sharpness, while the light source 2 generates the illumination light 5 and illuminates the primary hologram 3.

[0124] If the lighting device 1 is also intended to include the optical component 6, this can be provided, and furthermore, a position and alignment of the optical component 6 relative to the light source 2 and the primary hologram 3 can be determined, in which the illumination light 5 is redirected such that the first lighting function 8 generated by the primary hologram 3 has maximum light intensity, maximum contrast, and / or maximum image sharpness. The respective positioning and alignment of the primary hologram 3 and the optical component 6 can, for example, take place simultaneously until the most optimal representation of the first lighting function 8 has been achieved.

[0125] In a third method step S3, the secondary hologram 4 is arranged and aligned at a distance from the primary hologram 3 in such a way that the secondary hologram 4 can be illuminated or is illuminated by a reflected portion 5.1 of the illumination light 5, which is reflected by a Fresnel reflection at a boundary surface 3.1 of the primary hologram 3 when the primary hologram 3 is illuminated.

[0126] Similar to the arrangement of the primary hologram 3, a position and orientation (relative to the primary hologram 3) can also be determined for the secondary hologram 4, in which the second luminous function 9 generated by the secondary hologram 4, e.g., the second holographic image, has a maximum light intensity, a maximum contrast, and / or a maximum image sharpness. Figure 3 shows, purely schematically, the luminous device 1 according to a further optional embodiment, which has a tertiary hologram 14 instead of the optical component 6. The tertiary hologram 14, which may, for example, have a reflection hologram and / or a transmission hologram, is arranged such that it can be illuminated by the illuminating light 5.

[0127] The lighting device 1 further comprises an optical element 10 configured to generate a third lighting function 13, e.g., additional lighting, in response to illumination of the optical element 10. The optical element 10 may, for example, comprise a light guide and / or a light diffuser.

[0128] The tertiary hologram 14 is arranged between the light source 2 and the optical element 10 and is designed to separate the illumination light 5 into a first portion 5.2 and a second portion 5.3, wherein the first portion 5.2 is output in the direction of the primary hologram 3 and the second portion 5.3 is output in the direction of the optical element 3.

[0129] In this embodiment, the primary hologram 3 can be expediently illuminated by the first portion 5.2, wherein the first portion 5.2 serves to generate the first luminous function 8, e.g. the first holographic image.

[0130] The secondary hologram 4 is arranged at a distance from the primary hologram 3 such that it can be illuminated by the reflected portion 5.1 of the first portion 5.2, which is reflected by a Fresnel reflection at the interface 3.1 of the primary hologram 3 when the primary hologram 3 is illuminated.

[0131] The tertiary hologram 14 can be configured to separate the illumination light 5 into the first portion 5.2 and the second portion 5.3 such that the first portion 5.2 is redirected toward the primary hologram 3, and the second portion 5.3 passes through the tertiary hologram 14 without redirection. For example, the first portion 5.2 can be redirected such that it strikes the primary hologram 3 at a predetermined angle, wherein the predetermined angle can be selected such that the primary hologram 3 generates the first luminous function 8 in response to the illumination by the first portion 5.2. A desired angular range can thus be selected to minimize the amount of light from the first portion 5.2 that does not contribute to the first luminous function 8 and is thus lost unused.

[0132] In order to further increase the efficiency of the first part 5.2, the tertiary hologram 14 can further have a collimation function so that the light rays of the first part 5.2 are output as rectified as possible and accordingly impinge on the primary hologram 3 as rectified as possible.

[0133] The tertiary hologram 14 can further be configured to separate the illumination light 5 into the first portion 5.2 and the second portion 5.3 based on wavelength, wherein the first portion 5.2 comprises light wavelengths from one wavelength range and the second portion 5.3 comprises light wavelengths outside the wavelength range. The wavelength range can correspond to a wavelength range for which the primary hologram 3 is designed to generate the first luminous function 8. As a result, the first portion 5.2 can be optimized so that as little light as possible from the first portion 5.2 is lost unused without contributing to the first luminous function 8.

[0134] The lighting device 1 further comprises an additional light source 11 for generating an additional illumination light 12. The tertiary hologram 14 can be illuminated by the additional illumination light 12 and is designed to separate the additional illumination light 12 into a first additional portion 12.2 and a second additional portion 12.3. The first additional portion 12.2 is output by the tertiary hologram 14 in the direction of the primary hologram 3, and the second additional portion 12.3 is output by the tertiary hologram 14 in the direction of the optical element 10. In principle, it is also conceivable for the lighting device 1 of this further embodiment to have only one light source, i.e., the light source 2 or the additional light source 11.

[0135] In the configuration shown, the tertiary hologram 14 is arranged between the additional light source 11 and the primary hologram 3. Accordingly, the tertiary hologram 14 is configured such that the first portion 5.2 is deflected toward the primary hologram 3 and the second portion 5.3 passes through the tertiary hologram 14 without deflection, and simultaneously, the first additional portion 12.2 passes through the tertiary hologram 14 without deflection and the second additional portion 12.3 is deflected toward the optical element 10.

[0136] Thus, the primary hologram 3 can be additionally illuminated by the first additional portion 12.2, whereby the first additional portion 12.2 also contributes to the generation of the first luminous function 8. This accordingly generates a reflected portion 12.1 of the first additional portion 12.2, which, when the primary hologram 3 is illuminated, is reflected by a Fresnel reflection at the interface 3.1 of the primary hologram 3 and illuminates the secondary hologram 4.

[0137] By simultaneously illuminating the tertiary hologram 14, the light intensities of the first portion 5.2 and the second portion 5.3 can be increased due to the respective superposition by the first additional portion 12.2 and the second additional portion 12.3, whereby the first lighting function 8, the second lighting function 9 and the third lighting function 13 can each be generated with a higher light intensity.

[0138] The tertiary hologram 14 can be configured to, analogously to the illumination light 5 of the light source 2, separate the additional illumination light 12 of the additional light source 11 into the first additional portion 12.2 and the second additional portion 12.3 based on wavelength. The first additional portion 12.2, like the first portion 5.2, can have light wavelengths from the wavelength range. Similarly, the second additional portion 12.3, like the second portion 12.3, can have light wavelengths outside the wavelength range.

[0139] Furthermore, it is conceivable that the lighting device 1 can be configured to generate a different-colored first lighting function 8, e.g., the first holographic image, a different-colored second lighting function 9, e.g., the second holographic image, and / or a different-colored lighting function 13. For example, red and yellow light can be generated for the lighting function 13, e.g., for a brake light and a turn signal of a motor vehicle.

[0140] For this purpose, the illumination light 5 and the additional illumination light 12 can have different light colors and / or different wavelength ranges. Alternatively, or additionally, the tertiary hologram 14 can be configured to form, through the first portion 5.2 and the first additional portion 12.2, an illumination for generating the first holographic image and the second holographic image with multiple light colors and / or different wavelength ranges. Furthermore, alternatively, or additionally, the tertiary hologram 14 can be configured to form, through the second portion 5.3 and the second additional portion 12.3, an illumination for generating the luminous function 13 with multiple light colors and / or different wavelength ranges.

[0141] Fig. 4 shows a schematic diagram in which the angle of incidence 0, in degrees, is plotted on the horizontal axis and the reflection and transmission coefficients are plotted on the vertical axis. The graphs Ts and R correspond to sthe transmission coefficient (reference numeral 400) or reflection coefficient (reference numeral 402) for s-polarized light, and the graphs Tp and Rp the transmission coefficient (reference numeral 404) or reflection coefficient (reference numeral 406) for p-polarized light. The angle of incidence can be the angle between the wave vector of the illumination light incident on the respective hologram and the surface normal of the interface of the respective hologram. For the situation of a reconstruction of the primary hologram with an angle of incidence of the illumination light on the interface of less than 70°, the use of s-polarized illumination light results in a proportion of Fresnel-reflected light of approximately 30% (see marking 408). If the primary hologram is reconstructed with the Fresnel-reflected light at an angle of incidence of less than 30°, the proportion of Fresnel-reflected light is approximately 6% (see marking 410).If we assume diffraction efficiencies of more than 90% for the primary and secondary holograms, an intensity ratio of ~2.5:1 between the 1st orders of the primary hologram and the secondary hologram can be realized.

[0142] When using unpolarized or p-polarized illumination light, the intensity ratio is larger, such as 5.5:1 or 22:1.

[0143] The intensity ratio can be adjusted by reducing the diffraction efficiency of the primary hologram. This can allow achieving an intensity ratio of 1:1.

[0144] Optionally, an intensity ratio of 1:1 can be achieved with an angle of incidence of the illumination light of approximately 80° (see marking 412) on the primary hologram and an angle of incidence <20° on the secondary hologram, even at maximum diffraction efficiency.

[0145] An intensity ratio of 1:1 can offer the advantage that a reconstruction of the primary hologram and a reconstruction of the secondary hologram have approximately the same brightness.

[0146] 1 lighting device

[0147] 2 light source

[0148] 3 primary hologram

[0149] 3.1 Interface of the primary hologram

[0150] 4 secondary hologram

[0151] 5 Illumination light

[0152] 5.1 reflected portion of the illuminating light or the first portion of the illuminating light

[0153] 5.2 first part of the illumination light

[0154] 5.3 second part of the illumination light

[0155] 6 optical component

[0156] 7 Collimator

[0157] 8 first lighting function

[0158] 9 second lighting function

[0159] 10 optical element

[0160] 11 additional light source

[0161] 12 additional lighting light

[0162] 12.1 reflected portion of the first portion of the additional

[0163] Illumination light

[0164] 12.2 first part of the additional illumination light

[0165] 12.3 second part of the additional illumination light

[0166] 13 third lighting function or light to provide the third lighting function

[0167] 14 tertiary hologram

[0168] 100 procedures

[0169] S1-S3 process steps

Claims

Patent claims 1 . Lighting device (1 ), wherein the lighting device (1 ) comprises: - a light source (2) for generating an illuminating light (5); - a primary hologram (3) which can be illuminated by the illuminating light (5) to produce a first luminous function (8); and - a secondary hologram (4); characterized in that the secondary hologram (4) is arranged at a distance from the primary hologram (3) such that it can be illuminated by a reflected portion (5.1) of the illumination light (5), which, when the primary hologram (3) is illuminated, is reflected by a Fresnel reflection at a boundary surface (3.1) of the primary hologram (3).

2. Lighting device (1) according to claim 1, wherein the secondary hologram (4) is designed to generate a second lighting function (9) in response to illumination by the reflected portion (5.1).

3. Lighting device (1) according to claim 2, wherein the first lighting function (8) is a generation of a first holographic image and the second lighting function (9) is a generation of a second holographic image.

4. Lighting device (1) according to claim 3, wherein the primary hologram (3) and the secondary hologram (4) are designed to generate the first holographic image and the second holographic image in a same direction and / or to generate them in such a way that the first holographic image and the second holographic image are simultaneously perceivable by a viewer.

5. Lighting device (1) according to one of the preceding claims, wherein the secondary hologram (4) is arranged facing the interface (3.1) of the primary hologram (3).

6. Lighting device (1) according to one of the preceding claims, wherein the primary hologram (3) is arranged between the secondary hologram (4) and the light source (2).

7. Lighting device (1) according to one of the preceding claims, wherein the primary hologram (3) is a reflection hologram.

8. Lighting device (1) according to one of the preceding claims, wherein the secondary hologram (4) is a transmission or reflection hologram.

9. Lighting device (1) according to one of the preceding claims, wherein the reflected portion (5.1) of the illuminating light (5) has the same spectral distribution as the illuminating light (5) with which the primary hologram (3) can be illuminated by the illuminating light (5) to generate the first illuminating function (8).

10. Lighting device (1) according to one of the preceding claims, wherein the lighting device (1) comprises: - an optical component (6) designed to redirect the illumination light (5) in the direction of the primary hologram (3).

11. Lighting device (1) according to claim 10, wherein the optical component (6) is designed to - the illumination light (5) at an angle or an angular range for which the primary hologram (3) is used to generate the first Illuminating function (8) is designed to redirect in the direction of the primary hologram (3), and / or - to redirect only a wavelength-selective portion of the illumination light (5) in a light wavelength range for which the primary hologram (3) is designed to generate the first luminous function (8) in the direction of the primary hologram (3).

12. Lighting device (1) according to claim 10 or 11, wherein the optical component (6) has a reflection hologram and / or a transmission hologram.

13. Lighting device (1) according to one of the preceding claims, wherein the lighting device (1) is designed as a structural unit.

14. Motor vehicle lamp, wherein the motor vehicle lamp comprises a lighting device (1) according to one of the preceding claims.

15. A method (100) for producing a lighting device (1), the method (100) comprising: - Providing (S1) a light source (2), a primary hologram (3) and a secondary hologram (4), wherein the light source (2) is designed to generate an illumination light (5) and the primary hologram (3) is designed to generate a first lighting function (8); - arranging and aligning (S2) the light source (2) and the primary hologram (3) relative to one another in such a way that the primary hologram (3) can be illuminated or is illuminated by the illuminating light (5) to generate the first luminous function (8); and - Arranging and aligning (S3) the secondary hologram (4) at a distance from the primary hologram (3) such that the secondary hologram (4) is illuminated by a reflected portion (5.1) of the illumination light (5) which, when the primary hologram is illuminated, Hologram (3) is reflected, illuminable or illuminated by a Fresnel reflection at a boundary surface (3.1) of the primary hologram (3).

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