DE102018119007A1 - Manufacture of holographic notch filters - Google Patents

Abstract

An object of the invention is to simplify the production of holographic notch filters and thus open up further possible uses thereof. To produce a holographic notch filter with a predetermined stop band, exposure light is generated by means of a light source whose spectrum corresponds to the predetermined stop band. A holographic recording medium is arranged in such a way that an optical path of the exposure light runs from the light source through the holographic recording medium to a mirror, the exposure light is reflected at the mirror and the beam path again runs through the recording medium in accordance with the reflection. The recording medium is exposed by means of the exposure light, a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium being less than a coherence length of the exposure light and the coherence length being less than a second optical path length along the beam path from the Light source to the mirror is.

Description

The invention is in the field of optical filters and relates in particular to a method and an apparatus for producing a holographic notch filter and the use of such a holographic notch filter.

The use of holographic systems can reduce the space requirement compared to catadioptric systems. Objects that appear in three-dimensional space, that is to say holographic objects, can also be represented with holographic systems. For example, holographic systems for generating lighting are increasingly being used in lighting technology. In addition to, for example, electromechanical displays or screens, holographic display systems are also increasingly being used for the optical signaling of variable information.

In optics and especially in holographic systems, it may be necessary to filter out certain parts of a light spectrum, so that a filtered light either no longer has this part or only has it. Dyes, phosphate glasses, dielectric coatings or prisms can be used for this. Holographic notch filters can also be used for this purpose, which have a small space requirement, a low weight, good optical properties - such as a large filter effect in the area to be filtered and a high light transmittance in the rest of the spectral range -, a high mechanical stability and / or an exact adaptation to one can have the desired barrier tape. Such holographic notch filters are usually produced by mechanically embossing an optical grating into a holographic image carrier or by holographically recording a reflecting surface in a holographic recording medium with a photosensitive material. Typically, a laser system with a particularly stable and powerful laser, especially a gas laser such as a helium-neon laser or an argon-ion laser, is used for the holographic recording, a laser light generated by the laser source using a semi-transparent plate in a reference beam and an illuminating beam is split, the illuminating beam illuminates the reflecting surface and then the reference beam enters the recording medium as a reference source on one side of the recording medium and the light reflected by the reflecting surface enters the holographic recording medium as an object wave on an opposite side of the recording medium and the reference wave and interfere with the object wave in such a way that - if necessary after development of the photosensitive material - an optical grating is formed in the recording medium, which light with wavelengths that correspond to the wavelengths during the recording calculate how the holographically recorded reflective surface diffracts, i.e. reflects and thus filters out.

There is a need to simplify the production of holographic notch filters and, in particular, to make them more efficient, faster or less complex in terms of the systems required for production, and to open up or improve further possible uses of holographic notch filters.

The invention fulfills this need in each case by a method for producing a holographic notch filter, by a device for producing a holographic notch filter, by a correspondingly produced holographic notch filter and by a system for the reconstruction of a hologram with such a holographic notch filter, according to the teaching of one of the main claims , Advantageous embodiments, further developments and variants of the present invention are the subject of the subclaims in particular.

A first aspect of the invention relates to a method for producing a holographic notch filter with a predetermined stop band. In the method, exposure light is generated by means of a light source, the spectrum of which corresponds to the predetermined stop band. Furthermore, the exposure light illuminates a mirror, the light source and the mirror being arranged in such a way that a beam path of the exposure light runs from the light source to the mirror and the beam path continues according to a reflection of the exposure light on the mirror and from there. A holographic recording medium is also arranged such that the beam path runs through the holographic recording medium before and after reflection. Finally, the holographic recording medium is exposed using the exposure light. A first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium is smaller than a coherence length of the exposure light. In addition, the coherence length of the exposure light is smaller than a second optical path length along the beam path from the light source to the mirror. In some variants, the exposure light can be generated in such a way that the first optical path length is smaller than the coherence length of the exposure light, or the holographic recording medium can be arranged accordingly. Accordingly, in some variants, the light source and the mirror can be arranged such that the coherence length of the exposure light is less than the second optical path length, or one Exposure light are generated with a correspondingly small enough coherence length.

In the sense of the invention, a “holographic notch filter” is to be understood as meaning at least one optical element in which a hologram is recorded, the light of a specific spectral range - the so-called stop band - depending on the design, not reflected or not transmitted and in this way from the rest of the light filtered out, so that the filtered light at least essentially no longer has any spectral components that are in the stop band. Such a holographic notch filter can usually be produced by recording a hologram of a reflecting surface with a specific light wavelength in a holographic recording medium, which in particular has a layer of a photosensitive material, so that the holographic recording medium is a holographic image carrier of the holographically recorded reflecting surface , In this way, the hologram recorded in the holographic image carrier reflects a wavelength that corresponds to a wavelength with which the hologram was recorded, and thus acts as a blocking filter for this wavelength in a transmission arrangement, while light with other wavelengths has almost no reflection got through. Depending on the spectral width of the light during the recording, the depth, the filter effect and / or the blocking band are formed, so that surrounding wavelengths are also reflected by the recorded hologram.

For the purposes of the invention, the fact that a light essentially does not have certain spectral components means, in particular, that the ratio of light energy or power in these spectral components and the other spectral components of light, in particular in the range of the visible spectrum of Light less than 1/10, preferably less than 1/100 and more preferably less than 1/1000.

For the purposes of the invention, the fact that a light has a plurality of spectral lines in a spectral range should also be understood to mean that the light consists at least in this spectral range or also entirely only from these spectral lines and / or other spectral components - i.e. spectral components that are not in each case at or within one of the spectral lines - essentially does not have.

An advantage of arranging the holographic recording medium, so that the beam path runs before and after reflection through the holographic recording medium, can in particular be due to the fact that this arrangement has a particularly high optical stability - in particular compared to arrangements in which light is divided into a reference beam and an illuminating beam is enabled, which simplifies the implementation of the method or a corresponding device for the method and thus holographic notch filters can be produced more easily and efficiently. The first optical path length, which is smaller than the coherence length of the exposure light, eliminates interference in the holographic recording medium between the exposure light which passes through the holographic recording medium from the light source and the exposure light which has already been reflected by the mirror and then again enters the recording medium, achieve, whereby the mirror is recorded as a holographic object.

In addition, an advantage of the coherence length of the exposure light, which is smaller than the second optical path length, can in particular lie in the fact that parts of the exposure light which reach the holographic recording medium via another - in particular longer - beam path have no or at least weaker interference in the holographic recording medium generate, whereby such interference patterns generated via other beam paths can be avoided.

In the sense of the invention, such interference patterns generated due to an additional / different beam path are also referred to as parasitic interference structures. These could arise, for example, if part of the exposure light strikes an object in a room in which a holographic notch filter is produced and the light emitted by this object then acts as an additional - in particular parasitic - reference wave or object wave and the coherence length is correspondingly greater is so that interference occurs between the different object waves and / or reference waves. Such parasitic interference structures can also be macroscopically visible in a holographic notch filter, as a result of which it no longer appears homogeneous, but in particular has wave-like patterns or light and dark dots.

By choosing a shorter coherence length of the exposure light, the occurrence of such parasitic interference structures can advantageously be avoided and / or a homogeneous appearance can be achieved, which opens up application possibilities in which such a holographic notch filter is visible - for example in an illumination system such as a headlight or a rear light a vehicle - and / or there are special requirements for the appearance of the holographic notch filter or an object with such a holographic notch filter.

In some embodiments, the holographic recording medium has a layer thickness. The first optical path length is related to a side of the holographic recording medium facing the mirror. In addition, in such embodiments, the coherence length of the exposure light can be less than the sum of the first optical path length and twice the layer thickness. In this advantageous manner, parasitic interference structures can be avoided particularly effectively. In addition, it can be achieved that the smaller the coherence length of the exposure light, the fewer interference patterns are formed in the direction of a side of the holographic recording medium facing away from the mirror, which enables a particularly homogeneous appearance of the holographic notch filter produced in this way. Here, the interference patterns can therefore only be formed in one area on the side of the holographic recording medium facing the mirror, while in the rest of the holographic recording medium, in particular in the direction of the side facing away from the mirror, at least essentially no more interference patterns are formed, but an uncorrelated exposure and thus gives a macroscopically homogeneous appearance.

In some embodiments, in the holographic recording medium, a photosensitive layer for receiving the hologram of the holographic notch filter is embedded in or applied to a carrier material. In an advantageous variant, in which the photosensitive layer is applied, the applied photosensitive layer faces the mirror. In addition, in such embodiments, the coherence length of the exposure light can be less than the sum of the first optical path length and twice the distance of the photosensitive layer from a side of the holographic recording medium facing the mirror and twice the layer thickness of the photosensitive layer. In this advantageous manner, parasitic interference can be avoided, which could otherwise occur due to exposure light reflected on a side of the holographic recording medium facing away from the mirror.

A second aspect of the invention relates to a further method for producing a holographic notch filter with a predetermined stop band. The further method can have the features of the method according to the first aspect of the invention in some variants or conversely, the method according to the first aspect of the invention can have the features of the method according to the second aspect of the invention in some variants.

The method according to the second aspect of the invention comprises providing a film or a tape with a photosensitive layer. Part of the tape or film is attached to a mirror as a holographic recording medium or is already attached to a mirror. Furthermore, exposure light is generated by means of a light source, the spectrum of which corresponds to the predetermined stop band, the mirror being arranged in such a way that a beam path of the exposure light runs from the light source to the mirror and the beam path continues from there in accordance with a reflection of the exposure light at the mirror runs. In the method, the holographic recording medium is exposed by means of the exposure light after attachment, the beam path before and after reflection through the holographic recording medium and a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium being less than one Exposure light coherence length. Finally, after the exposure, the holographic recording medium is detached from the mirror.

The possible advantages, embodiments or variants of the first aspect of the invention already mentioned above also apply correspondingly to the further method according to the invention for producing a holographic notch filter. An advantage of the tape or film with a photosensitive layer and the attachment of a part thereof as a holographic recording medium can in particular lie in the fact that a tape or film with one or more holographic notch filters can be produced along the tape, as a result of which manufacturing can be simplified, made cheaper and / or more efficient. By attaching the holographic recording medium to the mirror, a particularly stable optical system can be achieved, whereby the manufacture can be simplified and / or the quality of a holographic notch filter produced in this way can be improved. Furthermore, an efficient production and / or production of holographic notch filters with a high quality can open up further application possibilities.

In the following, embodiments, exemplary embodiments, variants or aspects are described, in particular with regard to the tape with the photosensitive layer. There are corresponding variants for the film with the photosensitive layer instead of the tape.

In some embodiments, where a portion of a tape with a photosensitive layer on the mirror is already prior to performing of the method, the tape has a reflective surface as a mirror. In some variants, the tape can be coated or laminated with a reflective material. In this advantageous manner, a particularly high stability during exposure can be achieved, as a result of which particularly precisely defined interference patterns can be generated and thus a holographic notch filter with a particularly good filter effect can be achieved. In addition, a high throughput in the production of holographic notch filters can be achieved because the mirror is already attached to the belt.

In some embodiments, in which the tape as a mirror is coated or laminated with a reflective material or has a surface with a reflective material, the holographic recording medium is moved together with the mirror continuously or stepwise, in particular by means of a rotatable cylinder or a conveyor belt.

In some embodiments, in which a portion of a tape with a photosensitive layer is attached to the mirror when performing the method, the tape or a portion thereof is coated on one of its surfaces facing away from the light source with a reflective material or a reflective material Foil laminated to the tape. A particularly high stability during exposure can also be achieved in this advantageous manner.

In some variants, the tape is moved continuously or step by step and a reflective film is laminated onto a respective part of the tape or the respective part is coated with the reflective material. In some advantageous variants, the belt can be moved by means of a rotatable cylinder or by means of a conveyor belt.

In some embodiments, where part of a belt with a photosensitive layer is attached to the mirror when performing the method, the mirror is part of a reflective surface of a rotatable cylinder or conveyor belt.

In some embodiments, in which the holographic recording medium is attached to a rotatable cylinder or a conveyor belt, the rotatable cylinder or the conveyor belt is moved continuously, and thereby further parts of the belt with a photosensitive layer as a holographic recording medium are applied to other parts of the mirror acting reflective surface attached or laminated with the reflective film or coated with the reflective material. The holographic recording medium is moved together with the mirror and exposed during movement. Furthermore, already exposed parts of the tape or the holographic recording medium are detached from the mirror. The movement takes place in such a way that the first optical path length remains at least substantially constant. In this advantageous manner, a tape with such a holographic notch filter can be produced particularly efficiently — that is, particularly quickly.

In some embodiments, in which a part of a belt with a photosensitive layer as a holographic recording medium is mounted on a mirror, a rotatable cylinder or a conveyor belt, which has the mirror, is moved stepwise and thereby further parts of the belt attached with the photosensitive layer as a holographic recording medium to other parts of a reflecting surface of the cylinder or the conveyor belt acting as a mirror. The holographic recording medium, in particular that part of the holographic recording medium or the belt which is attached to the cylinder or the conveyor belt, is moved together with the mirror. The holographic recording medium is exposed before or after moving, but in some advantageous variants not while moving. Finally, already exposed parts of the tape or the holographic recording medium are detached from the mirror. In this advantageous manner, interference with the exposure by moving the holographic recording medium during exposure can be avoided, as a result of which holographic notch filters with a particularly good optical quality can be produced. Alternatively, the rotatable cylinder or the conveyor belt may not have the mirror and instead the belt may have a reflective surface, be coated with a reflective material or a reflective film may be laminated to the other parts of the belt, so that the reflective surface, the reflective material or the reflective film each act as the mirror.

In some embodiments, in which the mirror and the holographic recording medium are moved together - in particular relative to the light source - a second optical path length along the beam path from the light source to the mirror on which the holographic recording medium is mounted remains when moving or at least before and after moving at least essentially constant. By keeping the second optical path length constant, it is possible for the exposure light, which acts as a reference wave before it is reflected, to remain at least essentially constant, thus reducing the quality of the holographic image of the mirror and thus the notch filter produced can be increased.

In some embodiments, the holographic recording medium is placed or attached to the mirror so that it contacts the mirror. In some advantageous variants, it can adhere to the mirror - in particular electrostatically, chemically or mechanically. In this advantageous manner, a particularly stable optical system and thus a holographic notch filter of high quality can be achieved and / or the effects of disturbances that could occur when exposing the holographic recording medium can be reduced. The holographic recording medium, if it sticks to the mirror, can also be moved together particularly easily, particularly robustly and / or with little or no change in the first optical path length.

In some embodiments, the holographic recording medium is arranged or attached to the mirror in such a way that the first optical path length or its variation - in particular over an areal average value of the first optical path length - is smaller by a factor of two than one of the wavelengths in the spectrum of the exposure light. For this purpose, the holographic recording medium can contact the mirror in some advantageous variants or adhere to the mirror. In this advantageous manner, it can be ensured that the exposure light acting as a reference wave before reflection and the exposure light acting as object wave after reflection interfere in the holographic recording medium and these interferences remain stable, for example when the holographic recording medium and the mirror are moved together, as a result of which the optical quality of the holographic notch filter produced in this way can be increased.

In some embodiments, the first optical path length is between 0 µm and 500 µm. In this advantageous manner, an exposure light for exposing the holographic recording medium and for generating interferences suitable for the holographic notch filter can also be used in the holographic recording medium, the coherence length of which is correspondingly short.

In some embodiments, the coherence length of the exposure light is greater than the first optical path length and greater than 10 μm. In this advantageous manner, the method can be made more robust with respect to a change in the first optical path length when the method is carried out several times and between individual exposure steps. There can also be an advantage in that the holographic recording medium can be correspondingly spaced from the mirror, as a result of which in particular the holographic recording medium can be moved independently of the mirror.

In some embodiments, the coherence length of the exposure light is less than 5000 microns. In this advantageous manner, parasitic interference structures can be avoided, usually objects which emit part of the exposure light due to additional beam paths and thus cause parasitic interference structures, a change in the path length relative to the second optical path length - that is, the path from the light source along the beam path to the mirror - by more than 5000 µm.

In some embodiments, an angle of incidence of the exposure light on the mirror is greater than 0 °. In this advantageous way it can be avoided that the reflected exposure light is reflected back to the light source.

In some embodiments, an angle of incidence of the exposure light on a side of the holographic medium facing the light source or on a side of the holographic recording medium facing the mirror is greater than 0 °, this angle of incidence being chosen in particular such that the interference generated by the exposure light in the holographic recording medium and their peaks and valleys are compressed relative to a light path in the event of a vertical incidence, with which the stop band of the notch filter thus produced can be shifted to shorter wavelengths and / or compressed for a given spectrum of the exposure light.

In some embodiments, the holographic recording medium is arranged or attached parallel to the mirror at a predetermined distance. In this advantageous manner, the first optical path length is at least substantially constant over the area of the holographic recording medium. In some variants, the first optical path length corresponds to twice the predetermined distance for a vertical incidence of the exposure light on the holographic recording medium and thus also for the parallel mirror, and for an angle of incidence that is greater than 0 °, twice the predetermined distance divided by the cosine of angle of incidence.

In the sense of the invention, “correspondence between a predetermined stop band and a spectrum of an exposure light” is at least to be understood to mean that the wavelengths in the spectrum of the exposure light and the wavelengths in the stop band are at least substantially the same or - if the holographic recording medium, for example during development after exposing his spatial extent changes or if the exposure light or a light to be filtered by means of the notch filter produced occurs with a different angle of incidence on the holographic recording medium - shifted, compressed or stretched.

In some embodiments, the mirror is designed as a surface mirror, so that the exposure light is reflected on the surface of the mirror — that is, in particular on an interface of the mirror with its surroundings, such as air or the holographic recording medium. In this advantageous manner, the first optical path length can be reduced and / or, in particular if the holographic recording medium reflects the surface of the mirror, precisely defined, as a result of which the quality of the holographic notch filter produced in this way can be increased. Another advantage of the reflection of the exposure light on the surface of the mirror can be that parasitic reflections, which could arise at an additional interface, for example, can be avoided.

In some embodiments, the mirror has a reflective surface and a protective layer for the reflective surface. The protective layer has a layer thickness which is less than half the coherence length. It is understood here that the first optical path length relates in particular to the reflecting surface and a side of the holographic recording medium facing the reflecting surface.

In some advantageous variants, the layer thickness of the protective layer has values in the range of a few micrometers, in particular between 1 μm and 20 μm.

An advantage of this layer thickness of the protective layer can be, in particular, that the reflecting surface can be protected and / or the interference between the reference wave and the object wave can be ensured.

In some embodiments, the exposure light is generated by means of the light source in that the light source first generates a light with a first spectral range and this light is filtered using an additional notch filter. The additional notch filter - that is to say a notch filter that is not produced with the method in this passage of the method at least - has a stop band which overlaps the first spectral range in such a way that the light after filtering by the additional notch filter at least essentially only has spectral components on one side of the stop band. In this advantageous manner, the spectral range of the exposure light used for the exposure can be reduced compared to the light initially generated by the light source and / or adapted to the predetermined stop band, a holographic notch filter produced with the method having a stop band which corresponds to the spectrum during exposure.

In some embodiments - in particular in embodiments with an exposure light filtered by an additional notch filter - the light source has or consists of one or more light-emitting diodes. An advantage of the light-emitting diode can be, in particular, that it can be operated easily and inexpensively and / or robustly, without special safety precautions, as a result of which the production of a holographic notch filter can be simplified and made more efficient with such a method. An advantage of several light-emitting diodes compared to one light-emitting diode can lie in particular in that the light intensity can be increased, which in particular shortens the time required for the exposure and thus the production can be accelerated.

In some embodiments, the light source can have one or more units for generating exposure light - for example light-emitting diodes or solid-state lasers - and a movement device, the movement device being set up, the units for generating exposure light at least along an axis of movement, which in particular is at least substantially perpendicular to the beam path is to move. In this advantageous manner, a larger area of the holographic recording medium can be exposed - for example along a line or line that corresponds to the axis of movement.

In some embodiments, the light source can have one or more light-emitting diodes for generating exposure light, the coherence length of which is approximately or exactly 50 μm or the coherence length of which corresponds approximately or exactly to a layer thickness of the recording medium.

In some embodiments, which have light-emitting diodes, their coherence length can be adjusted, which in particular makes it possible to adapt the properties of the notch filter produced - for example the width of its stop band or the effectiveness of the notch filter.

A third aspect of the invention relates to a device for producing a holographic notch filter with a predetermined stop band. The device has a light source for generating an exposure light, the spectrum of which corresponds to the predetermined stop band. In addition, the device has a mirror which is arranged in such a way that a beam path of the exposure light when the light source is operated by the light source runs to the mirror and the beam path continues according to a reflection of the exposure light on the mirror and continues from there. In addition, the device has an arrangement device which is set up to arrange a holographic recording medium in such a way that the beam path runs through the holographic recording medium before or after reflection in order to expose the holographic recording medium. A first optical path length along the beam path from the optical recording medium to the mirror and from there to the holographic recording medium is smaller than a coherence length of the exposure light. In addition, the coherence length of the exposure light is smaller than a second optical path length along the beam path from the light source to the mirror.

The possible advantages, embodiments or variants of the preceding aspects of the invention already mentioned above also apply correspondingly to the device according to the invention for producing a holographic notch filter.

A fourth aspect of the invention relates to a further device for producing a holographic notch filter with a predetermined stop band. The further device has a light source for generating an exposure light, the spectrum of which corresponds to the predetermined stop band, and in some variants can also have further features of the device according to the third aspect of the invention. In addition, the device has a rotatable cylinder or a conveyor belt, each with a reflecting surface, which is arranged such that part of the reflecting surface acts as a mirror for the exposure light and a beam path of the exposure light runs from the light source to the mirror and the like Beam path continues from there according to a reflection of the exposure light on the mirror. Finally, the device has a material feed device which is set up to return part of a belt with a photosensitive layer to the rotatable cylinder or the conveyor belt and to attach it to the mirror as a holographic recording medium. The material feed device and the mirror are also set up to attach the holographic recording medium to the mirror in such a way that the beam path runs before and after reflection through the holographic recording medium in order to expose the holographic recording medium. In addition, a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium is less than a coherence length of the exposure light.

The possible advantages, embodiments or variants of the preceding aspects of the invention already mentioned above also apply correspondingly to the further device according to the invention for producing a holographic notch filter.

A fifth aspect of the invention relates to yet another device for manufacturing a holographic notch filter with a predetermined stop band. The still further device has a light source for generating an exposure light, the spectrum of which corresponds to the predetermined stop band. In addition, the device has a material feed device and an arrangement device. The material feed device is set up to feed a part of a tape with a photosensitive layer to the arrangement device, which feeds such a tape that already has a reflecting surface, or this is set up to supply the respective part of the tape to be fed on one side, in particular the one side facing away from the light source, to be laminated with a reflective film or to be coated with a reflective material. In addition, the arrangement device is set up to arrange the respectively supplied parts of the tape as a holographic recording medium such that a beam path of the exposure light from the light source runs through the holographic recording medium, and then the exposure light is reflected by means of the reflecting surface, the reflecting film or the reflecting material , so that this or this acts as a mirror, and the beam path again runs through the holographic recording medium in accordance with the reflection, in order to expose the holographic recording medium when the light source is operated. In addition, a first optical path length along the beam path from the photosensitive layer of the holographic recording medium to the mirror and from there to the photosensitive layer is less than a coherence length of the exposure light.

The possible advantages, embodiments or variants of the preceding aspects of the invention already mentioned above also apply accordingly to the still further device according to the invention for producing a holographic notch filter.

A sixth aspect of the invention relates to yet another device for producing a holographic notch filter with a predetermined stop band, the device being set up to carry out a method according to the first or second aspect of the invention. In addition, this still further device can be designed in some variants according to the third or fourth or fifth aspect of the invention.

The possible advantages, embodiments or variants of the preceding aspects of the invention already mentioned above also apply correspondingly to the still further device for producing a holographic notch filter.

In some embodiments, the light source is configured to generate the exposure light such that the spectrum of the exposure light has those wavelengths which lie in the predetermined stop band of the holographic notch filter.

A seventh aspect of the invention relates to a holographic notch filter which has been produced using a device or a method according to one of the preceding aspects of the invention.

The possible advantages, embodiments or variants of the preceding aspects of the invention already mentioned above apply correspondingly to the holographic notch filter according to the invention via the features achieved thereby during manufacture.

An advantage of the holographic notch filter can be, in particular, that with it, particularly efficiently and / or with a small space requirement, certain undesired spectral lines - in particular a first or a second spectral line in a spectrum - or certain spectral components in a laser light generated by a laser device or in general can be filtered out in a light generated by a light source, while other components are at least essentially not filtered, as a result of which a high light yield or a high intensity of the light can be achieved. An advantage of the holographic notch filter can also be that, particularly compared to other optical filters, it enables particularly precise filtering with respect to a full half-value width of the notch band of the notch filter, the position of the notch band in the light spectrum and / or particularly steep flanks and / or this application-specific with the desired properties can be produced efficiently.

In some embodiments, the holographic notch filter has at least substantially no parasitic interference structures. In this advantageous manner, possible uses for such a holographic notch filter are possible, in which parasitic interference structures would interfere with a function or an appearance in the respective application.

In some embodiments, the holographic notch filter appears homogeneous. This also enables other possible uses.

An eighth aspect of the invention relates to a system for the reconstruction of a hologram. In this case, a holographic notch filter, which is designed in accordance with the seventh aspect of the invention, is used as a component of a light source, the light source generating or being set up to reconstruct the hologram. Such a system for the reconstruction of a hologram can in particular be a method for the reconstruction of a hologram or a device for the reconstruction of a hologram.

The possible advantages, embodiments or variants of the preceding aspects of the invention which have already been mentioned above also apply correspondingly to the system according to the invention, which in particular comprises possible uses for a holographic notch filter according to the invention.

One possible application of a holographic notch filter according to the invention - in particular a holographic notch filter which has been produced using a method or a device according to one of the preceding aspects of the invention - relates to a light source for the reconstruction of a hologram, a holographic display system, a method for the reconstruction of a hologram and the use of such a light source for the holographic display of information.

Holographic display systems make it possible to display information to be displayed as objects appearing in three-dimensional space, that is to say as holographic objects. In the case of a head-up display with a holographic display system, for example, the information can be inserted as three-dimensional objects in the field of view of a user of the holographic display system, so that information inserted in this way can also appear correctly in perspective. A holographic display system can also be used to use the perspective view of the user and the integration or apparent interaction of information displayed by means of the holographic display system - ie in particular of objects holographically displayed - to convey information. In order to generate or display a hologram which reproduces information with its objects, this hologram is usually recorded in a holographic image carrier and this is illuminated by means of a light source. For this purpose, the hologram and the light source must be coordinated with one another in such a way that the hologram is reconstructed when illuminated by the light source, that is, a light generated by the light source is changed - in particular diffracted - by the holographic image carrier so that it then generates a light wave field which the corresponds to the recorded or holographically reproduced object.

Laser systems are typically used in holography for the reconstruction of holograms. These enable a high light intensity and a particularly sharp reconstruction of holograms due to their narrow spectral width. Conversely, a large spectral width of a light source - i.e. H. a large full width at half maximum of the spectrum of the light generated by the light source - so that due to spectral dispersion, a hologram can only be reconstructed if at all, if at all. However, some types of holograms also allow reconstruction with a light that has a broad spectrum, or even with white light. However, such holograms are less efficient in terms of their light output or show a rainbow effect in which the reconstructed hologram has different colors depending on the viewing angle. The holographic image carrier required for such white light holograms can also be more complex and thus make it more difficult to reproduce, in particular dynamic, information by means of holographically represented objects.

The use of conventional laser systems for holographic display systems, for example in a head-up display, can be made more difficult by the fact that these usually have larger spatial dimensions compared to other light sources or other display systems, are mechanically particularly sensitive, require greater energy and / or generate high waste heat and therefore need cooling. The manufacture of such laser systems can also be technically complex and their integration into a holographic head-up display or corresponding integration of a holographic head-up display with such a laser system into a vehicle can be error-prone and / or time-consuming.

The preceding aspects of the invention and / or its application make it possible to simplify the illumination of holographic image carriers for holographic display systems, and in particular an energy-efficient, fail-safe and / or efficiently producible light source for the reconstruction of a hologram, in particular with a large depth of focus, for a holographic To provide information reproduction.

A first application relates to a light source for the reconstruction of a hologram. The light source has a laser device for generating laser light for at least one spectral range and at least one holographic notch filter. The laser light has a first spectral line and a second spectral line in at least one spectral range. In addition, the laser device and the at least one notch filter are arranged such that the laser light hits the notch filter and is filtered by it. Finally, the at least one holographic notch filter has a stop band that filters the second spectral line, so that after filtering through the notch filter, the laser light no longer has at least essentially the second spectral line.

In the sense of the invention, a “laser device” is understood to mean at least one device with one or more lasers, which is set up to generate a laser light. Typical lasers can be gas lasers, dye lasers or solid-state lasers.

An advantage of the laser device can be, in particular, that a high light intensity and narrow spectral components - typically with a full half-value width of less than 5 nm - can be achieved due to the individual spectral lines of the laser device, which enables a particularly sharp reconstruction of holograms , A program reconstructed in this way can have a particularly high depth of field and / or a particularly high light or luminous intensity. Due to the high depth of field and / or the high luminous intensity, the spatial depth and / or perspective views can advantageously be used for reproducing information.

A hologram reconstructed in this way can also be particularly useful. H. compared to other types for the reconstruction and / or illumination of holograms - enable stable color renditions, so that the hologram shows the same color even when the viewing angle is changed - in particular the color that is perceived when the spectral line used for the reconstruction is perceived. Conversely, a large spectral width of a light used for the reconstruction of holograms or several spectral lines in the laser light could result in a hologram being reconstructed only vaguely, if at all, due to spectral dispersion. In this way, double images can appear in the respective colors of the spectral lines, that is to say in each case the colors which are perceived for the respective spectral line, in particular in the case of a plurality of spectral lines. By filtering the laser light and especially filtering out the second spectral line, the reproduction quality of a hologram reconstructed with a laser light filtered in this way can be increased and / or the requirements on the laser device can be reduced, since in particular the laser light generated by the laser device only does one after filtering Reconstruction of the hologram must be of sufficient quality.

In some application forms, the laser device is designed as a laser projector which has an optical beam system. In this advantageous manner, the laser light, in particular if it has been generated by several lasers of the laser projector, can be directed to a target, in particular to the holographic notch filter.

In some application forms, the laser device is a commercially available and / or mass-produced laser device, in particular a laser projector. In this way, the manufacture of the light source can be simplified and made more efficient, since no individually manufactured laser device, which may be individually tuned for the respective application, is required. Failure safety can also be increased in this way, since statistical data can be collected for such laser devices from a mass production and thus in particular manufacturing tolerances, reasons for failure and failure probabilities can be recorded, so that failure safety can be optimized in a targeted manner.

In some application forms, the laser device is designed as a “pico projector”, which are usually mass-produced. Such pico projectors can also require little space, be light in weight and / or be inexpensive or efficient to manufacture.

In the sense of the invention it is understood that - if not technically excluded - instead of divergent light or divergent light beams or divergent laser light, convergent light or convergent light beams can also be used.

In some application forms, the spectral distance between the stop band of the at least one notch filter and the spectral maximum of the first spectral line is less than 15 nm, preferably less than 5 nm and more preferably less than 3 nm. An advantage of this - in particular small - spectral distance can be found therein lie that the laser light generated by the light source - i.e. the laser light of the laser device after its filtering - can be spectrally stabilized with respect to its first spectral line, whereby a deviation of the spectral band in the direction of the stop band of the notch filter can be avoided, i.e. the laser light after its filtering always is adjacent to the notch filter stop band. Typically, spectral lines from laser devices can migrate to other wavelengths by heating. The stop band of the holographic notch filter adjacent to the first spectral line prevents migration of the spectral line in the direction of the stop band, or the filtered laser light only has those portions of the first spectral line which, even when the first spectral line migrates, do not yet fall into the stop band of the holographic notch filter have hiked. This can also make it easier and / or more efficient to manufacture such a light source.

Some forms of application also have a sensor device for detecting the light intensity with respect to the at least one spectral range and a control device. The control device is set up to determine a value for the light intensity by means of the sensor device and to control the laser device based thereon in such a way that its laser light power is set to achieve a predetermined target value for the light intensity. In this advantageous manner, a specific target value for the laser light intensity can be achieved, deviations due to manufacturing fluctuations in the laser device or due to aging of the laser device or due to a change in the spectrum of the laser light generated by the laser device - at least within the operating parameters of the laser device. can be compensated. This enables a uniform and / or constant reconstruction of the hologram, in particular with regard to its luminosity. There can also be an advantage in that manufacturing can be simplified and / or manufacturing errors can be avoided, since manufacturing-related fluctuations in the components of the laser device can be compensated for by the control device.

In some advantageous variants of the sensor device, this is set up and in particular arranged to detect the light intensity of the laser light with respect to the at least one spectral range after the filtering by the holographic notch filter. In this advantageous manner, fluctuations in the filtering and / or in the spectrum of the laser light generated can also be taken into account when regulating the light intensity.

The regulation of the light intensity and a small spectral distance - in particular less than 15 nm - between the stop band of the notch filter and the spectral maximum of the first spectral line can also be advantageously combined, so that in particular spectral stabilization and at the same time a stabilization of the light intensity of the spectral line stabilized in this way or the at least one spectral range stabilized in this way can be achieved.

According to some application forms, the spectral distance between the spectral maximum of the first spectral line and the spectral maximum of the second spectral line is less than 30 nm. This spectral distance can also be preferred be less than 15 nm and more preferably less than 6 nm. As a result, pico projectors in particular can advantageously be used as the laser device.

According to some application forms, the light source can have a further holographic notch filter, the laser device being set up for generating laser light for a further spectral range and the laser light generated in this way having a third and a fourth spectral line in the further spectral range. In addition, the laser device, the at least one notch filter and the further notch filter are arranged such that the laser light after or during filtering through the at least one notch filter also strikes the further notch filter and is filtered by the further notch filter. Finally, the further holographic notch filter has a stop band which filters the fourth spectral line, so that the laser light after filtering through the further notch filter at least essentially no longer has the fourth spectral line. In this advantageous manner, two spectral lines - namely the first spectral line and the third spectral line - can be generated with the light source for the reconstruction of the hologram. As a result, the hologram can be reconstructed with a plurality of spectral ranges, that is to say in particular the at least one spectral range and the further spectral range, so that in particular a holographic object can be reproduced with light from these two spectral ranges. With a suitable choice of the spectral ranges, a multicolored reproduction of the holographic object can thus be achieved, whereby in particular more information can be reproduced, that is to say displayed, and / or the perception of the displayed information can be improved.

According to some application forms, the light source is designed for the reconstruction of a hologram with several colors. For this purpose, the laser device is set up to generate laser light with a plurality of spectral ranges, each spectral range having one or more spectral lines. In addition, the light source is set up to use one or more holographic notch filters to filter the laser light generated by the laser device such that after filtering by means of the holographic notch filter, the laser light has at most one spectral line and a total of at least two spectral lines in each of the spectral regions. In some variants, the spectral ranges can be selected for a three-color display with the colors red, green and blue, so that one each lies in the following ranges: 610-680 nm; 500-560 nm; and 410-490 nm. In some advantageous variants, the light source can also be set up to direct the generated and filtered laser light to a hologram which is designed as a multicolor hologram, so that it bends the laser light for the respective color in such a way that it colors the colored ones Portions of the respective color of the holographic object. In some advantageous and alternative variants, the light source can also be set up to direct portions of the laser light for a first color after or during filtering to a first hologram for this color and a second portion of the laser light for a second color after or during filtering to conduct a second hologram for the second color, whereby the first and / or the second hologram can be monochromatic holograms and / or not necessarily as multicolored holograms - which are therefore suitable for diffracting a multicolored light in each case for the color rendering of a holographic object - must be trained.

In some application forms, a plurality of spectral ranges of the laser light can also be overlaid or mixed for the colored display of information represented by a holographic object, whereby mixed colors with regard to the colors which are perceived in the spectral ranges can be achieved in particular. For example, a first spectral line which lies in a red-perceived spectral range - for example with a wavelength of 650 nm - and a third spectral line which is in a green-perceived spectral range - for example with a wavelength of 530 nm - can be combined as Light colors are mixed and render a holographic object that appears yellow.

According to some application forms, the coherence length of the laser device for the first spectral line is in the range of 350 μm, in particular approximately or exactly 350 μm.

According to some application forms, the coherence length of the laser device for one of the spectral lines, in particular for the first spectral line, is less than 1000 μm or less than 600 μm or less than 400 μm.

According to some application forms, the coherence length of the laser device for one of the spectral lines, in particular for the first spectral line, is greater than 100 μm or greater than 300 μm or greater than 340 μm.

In some application forms, the at least one holographic notch filter and / or a further notch filter is designed as a transmission hologram or as a reflection hologram.

In some application forms, the at least one holographic notch filter and / or another holographic notch filter is designed as a volume hologram. One advantage of designing a notch filter as a volume hologram can be that it is special can be produced precisely and / or enables particularly precise filtering, in which the position and / or the full half-value width of the stop band can be set particularly precisely, ie in particular can be recorded in a holographic image carrier. Particularly steep flanks on the sides of the barrier tape can also be achieved with a notch filter designed as a volume hologram. In order to adapt in particular the filter effect in the stop band, the transmittance outside the stop band and / or the full half-value width of the stop band of a holographic notch filter designed as a volume hologram, the thickness of the layer of holographic material in which the volume hologram is recorded can be adjusted in some advantageous variants , For this purpose, the thickness can in particular be increased in order to achieve a stronger filtering - ie a lower transmittance in the stop band - and / or a smaller full half-value width and / or steeper flanks in the stop band. Conversely, the thickness can be reduced, in particular to increase the transmittance outside the stop band, to increase an acceptance angle of the notch filter - for example by rotating the notch filter with respect to the laser device or using a laser device with divergent light beams, in the case of a holographic notch filter which is planar or collimated light has been recorded - and / or to broaden the full half-width of the stop band.

In some application forms which have the at least one notch filter and a further holographic notch filter, the at least one notch filter and the further notch filter are formed as a volume hologram in a layer made of holographic material. In some variants, the layer of holographic material can be part of a holographic image carrier. In this advantageous way, the two optical functions, i. H. integrate the filtering of the stop band of the at least one holographic notch filter and the filtering of the stop band of the further holographic notch filter in a holographic object, as a result of which a high energy efficiency or light yield and / or a small space requirement can be achieved.

In some applications, the light source has a holographic diffuser. In this advantageous manner, homogeneous illumination of the reconstructing hologram can be achieved. In some advantageous variants, the holographic diffuser can be combined with the at least one notch filter in an optical element, in particular a holographic image carrier and there in particular a layer with holographic material.

For the dynamic reproduction of information, several holograms can be reconstructed and, for this purpose, different holographic image carriers or different parts of a holographic image carrier can be illuminated with the light source or further light sources. The holographic image carrier can also be changeable in terms of its optical properties in such a way that it produces different light wave fields and thus differently reproduced holographic objects. A holographically reproduced object can be assigned to certain information and / or represent this information.

A second application relates to a holographic display system, in particular a holographic head-up display, which has a holographic image carrier for the holographic reproduction of an object and a light source according to the first application. The holographic display system is set up to illuminate the holographic image carrier by means of the light source. By illuminating the holographic image carrier by means of the light source, it is possible to make the object appear as a holographic object, that is to say in particular a holographic projection and / or reproduction of the object. In some variants, the object can be permanently recorded in the holographic image carrier. In some advantageous variants, the holographic image carrier can also have changeable optical properties and can be set up to change its optical properties based on a control in such a way that the object can be reproduced holographically and / or different holographic objects can be holographically reproduced by means of changing optical properties of the holographic image carrier The optical properties can be changed so that, depending on the control of the holographic image carrier, a light generated by the light source, which illuminates the holographic image carrier, is diffracted and causes a light wave field in which the respective holographic object appears.

The possible advantages, application forms or variants of the first application mentioned above also apply accordingly to the holographic display system.

In some application forms, the holographic display system has a control device and is set up to receive information to be displayed by means of the control device, to process this information and to reproduce the information to be displayed on the basis of a holographic object which represents the information to be displayed. For this purpose, in some variants, the control device is set up to control the light source so that it Depending on the information to be displayed, the holographic image carrier or a part thereof is illuminated, so that the holographic object or the holographic object recorded in this part of the hologram or the image carrier is reproduced holographically when illuminated, ie appears. In some variants, the control device can also be set up to control the holographic image carrier such that it changes its optical properties in such a way that a light generated by the light source, in particular laser light, is diffracted by the holographic image carrier and generates a lightwave field which corresponds to the holographic image Object corresponds. In this advantageous manner, changeable information can be reproduced. An advantage of the changeable holographic image carrier can be, in particular, that the possible reproducible or displayable information is not limited by a predetermined amount of objects permanently recorded in the holographic image carrier, but can in particular be dynamically adapted to the respective information.

In some application forms for the reproduction of several holographic objects, some or all of the holographic objects can each represent one or more pixels in three-dimensional space. In this advantageous manner, further objects can be reproduced holographically by assembling them from the pixels.

In some application forms, the or the holographic objects are recorded in the image carrier by means of a point light source or with divergent light or with diffuse light and the light source or at least the holographic display system has a diffuser. As a result, in particular holographic objects which reproduce one or more pixels in three-dimensional space can be particularly sharp and / or with otherwise comparable components of the display system compared to a display system with planar or collimated light for the reconstruction of the holograms with particularly low distortions and / or a high level reproduce spatial resolution.

A third application relates to a method for generating laser light for the reconstruction of a hologram. In the method, laser light with at least one spectral range is generated. In the process, the laser light generated is also directed to at least one holographic notch filter. In addition, the laser light generated is filtered by means of the at least one holographic notch filter. The laser light has a first spectral line and a second spectral line in at least one spectral range. In addition, the at least one holographic notch filter has a stop band which filters the second spectral line in such a way that the laser light after filtering through the notch filter at least essentially no longer has the second spectral line.

The possible advantages, application forms or variants of the previous applications already mentioned above also apply correspondingly to the method for generating laser light for the reconstruction of a hologram.

A fourth application relates to the use of a light source according to the first application or the use of a method according to the third application for the holographic display of information by means of a holographic reproduction of a holographic object which represents the information to be displayed. In some variants, the holographic reproduction can be a holographic projection.

The possible advantages, application forms or variants of the previous applications mentioned above also apply accordingly to the use for the holographic display of information.

In some applications, the holographic display of information can be in a vehicle and / or for a vehicle. According to some variants, this vehicle can be designed as a motor vehicle, in particular as a passenger car.

For this purpose, such a vehicle in some application forms can have a light source according to the first application or a holographic display system according to the second application, or can be designed to carry out a method according to the third application, or use such a light source, such a holographic display system or such a method, to holographically display information in this vehicle or for this vehicle, in particular for a user of this vehicle. In some variants, the holographic display system can also be designed as a vehicle which is set up for the holographic display of information.

Another possible application of a holographic notch filter according to the invention relates to a further light source for the reconstruction of a hologram, a holographic lighting device for a vehicle, a method for the reconstruction of a hologram and the use of such a light source for generating a holographic projection.

In lighting technology, in particular for vehicles, headlights of a vehicle, for example, can illuminate an area around the vehicle or rear lights of a vehicle can make such a vehicle visible to other road users, in particular in the dark, which can increase driving safety. Direction indicators or brake lights of a vehicle can also indicate a possible change in speed or change in direction of the vehicle.

The use of holographic systems can reduce the space requirement of such lighting devices compared to catadioptric systems. This enables a designer further freedom of design in the arrangement of such lighting devices. In addition, holograms that have been recorded on a holographic image carrier can be reconstructed using a holographic system, in particular a holographic lighting device. In this way it is possible, for example, to achieve predetermined and, in particular, more complex lighting than catadioptric systems - for example a specific and / or detailed light signature when illuminated by a headlight - or a luminous object that is not tied to the physical dimensions of the lighting device itself, - Such as brake lights or taillights or direction indicators that appear to appear outside the light device and / or the vehicle, which can also represent characteristic light signatures such as rectangles, triangles, stop signs or arrows in three-dimensional space.

Laser systems are usually used in holography for the reconstruction of holograms. These enable a high light intensity and a particularly sharp reconstruction of holograms due to their narrow spectral width. Conversely, a large spectral width of a light source - i.e. a large full half-value range of the spectrum of the light generated by the light source - to the effect that a hologram can only be reconstructed, if at all, due to spectral dispersion. However, some types of holograms also allow reconstruction with a light that has a broad spectrum, or even with white light. However, such holograms are less efficient in terms of their light output or show a rainbow effect in which the reconstructed hologram has different colors depending on the viewing angle.

The preceding aspects of the invention and / or its further application make it possible to simplify the reconstruction of holograms and, in particular, to enable simple, inexpensive and / or energy-efficient illumination of a holographic image carrier for the reconstruction of a hologram.

A first further application relates to a light source for the reconstruction of a hologram. The light source has a light emitting diode and at least one holographic notch filter. The light-emitting diode and the at least one notch filter are arranged such that a light emitted by the light-emitting diode strikes the notch filter at an angle of incidence. In addition, the at least one holographic notch filter for the angle of incidence has a stop band which overlaps with the spectrum of the light from the light-emitting diode in such a way that the light after filtering by the at least one notch filter has at least essentially only spectral components on one side of the stop band. In addition, the ratio of the full half-value width of the spectrum of the light emitted by the light-emitting diode to the full half-value width of the stop band is less than eight, preferably less than three and more preferably less than one.

An advantage of the light-emitting diode can in particular be that a light-emitting diode has lower safety requirements than a laser, which makes it easier to manufacture and use a light source with a light-emitting diode. In this advantageous manner, the occurrence of so-called “speckle patterns” - light spots due to interference phenomena when illuminating a surface with a laser - can be avoided. An advantage of the holographic notch filter can be, in particular, that certain unwanted spectral components in the light emitted by the light-emitting diode can be filtered out particularly efficiently and / or with a small space requirement, as a result of which a high luminous efficiency can be achieved. Thanks to the advantageous filtering of the light emitted by the light-emitting diode, the spectrum of the light can be adjusted after filtering, i.e. the position of the spectrum and its full half-value width can be adjusted so that a sharpness - in particular depth of field - sufficient for the respective application of a light filtered with it reconstructed hologram is made possible. For example, holograms for direction indicators, rear lights or brake lights require a depth of field between 1 cm and 100 cm, preferably between 2 cm and 50 cm and more preferably between 5 cm and 10 cm, while for headlights a depth of field of at least 5 m, preferably at least 10 m and more preferably 30 m may be required. The full half-width of the spectrum of the light after its filtering can be reduced, in particular for increasing the depth of field. The light efficiency or luminous efficacy of the light source can also be increased in particular by choosing a light-emitting diode which emits a light whose full half-value width is less than eight times the full half-value width of the stop band, a smaller full half-value width of the stop band can enable particularly efficient holographic notch filters and / or a smaller full half-value width of the spectrum of the light emitted by the light-emitting diode requires less filtering , so that only a small part of the emitted light has to be filtered and the efficiency increases. By filtering the light so that its remaining spectral components are at least essentially only on one side of the stop band, double images can be created in the reconstructed hologram, which are otherwise due to spectral dispersion due to spectral components of the light on one side and on the other side of the stop band could occur.

In some application forms, the light-emitting diode is set up and / or the light source has such a light-emitting diode that its emitted light has a spectrum with a full half-width that is less than 50 nm, preferably less than 25 nm and more preferably less than 15 nm. One advantage of these half-widths can be that only a limited portion of the spectrum - in particular less than half of the total light emitted with regard to its light energy - has to be filtered out in order to enable the hologram to be reconstructed with this filtered light.

• - FWHM: 50 nm, CL: 2,6 µm;
• - FWHM: 25 nm, CL: 5 µm;
• - FWHM: 10 nm, CL: 13 µm; und
• - FWHM: 5 nm, CL: 26 µm;

In some application forms, the coherence length of the light-emitting diode is less than 26 μm, preferably less than 13 μm, preferably less than 5 μm and more preferably less than 2.6 μm. According to some variants, the coherence length (CL) and the full half-value width (FWHM) can essentially have the following pairs of values:

• - FWHM: 50 nm, CL: 2.6 µm;
• - FWHM: 25 nm, CL: 5 µm;
• - FWHM: 10 nm, CL: 13 µm; and
• - FWHM: 5 nm, CL: 26 µm;

In some application forms, the at least one holographic notch filter is designed as a transmission hologram or as a reflection hologram.

In some applications, the light source has another holographic notch filter. The light-emitting diode and the additional notch filter are arranged in such a way that the light emitted by the light-emitting diode strikes the additional notch filter with a further angle of incidence. In one variant, the light can first strike the at least one holographic notch filter and, after filtering by the at least one holographic notch filter, strike the further holographic notch filter with the further angle of incidence. In another variant, conversely, the light can first strike the further holographic notch filter and then the at least one holographic notch filter. Also, in some variants, the angle of incidence with respect to the at least one notch filter and the further angle of incidence with respect to the further notch filter can be the same and / or the light can strike both notch filters at least substantially simultaneously. For the further angle of incidence, the further holographic notch filter has a stop band, part of the spectrum of the light emitted by the light-emitting diode lying between the stop band of the at least one notch filter and the stop band of the further notch filter. One advantage of filtering the emitted light by both notch filters - that is, the at least one holographic notch filter and the further holographic notch filter - can be in particular that the spectrum of the light can be filtered from both sides of the spectrum, as a result of which a particularly small full half-value width of the filtered Light can be achieved and a particularly sharp reconstruction of the hologram is made possible.

In some applications in which the light source has a further holographic notch filter, part of the spectrum of the light emitted by the light-emitting diode, which has the maximum of the spectrum, lies between the stop band of the at least one notch filter and the stop band of the further notch filter. In this advantageous manner, the portion of the spectrum of the light with the maximum is not filtered out, so that there is a high light yield and / or high energy efficiency.

In some application forms, in which the light source has a further holographic notch filter, the at least one notch filter and the further notch filter are formed in a layer made of holographic material. In some variants, the layer of holographic material can be part of a holographic image carrier. In this advantageous way, the two optical functions, i.e. integrate the filtering of the stop band of the at least one holographic notch filter and the filtering of the stop band of the further holographic notch filter in a holographic element, as a result of which a high energy efficiency or luminous efficiency and / or a small space requirement can be achieved.

In some application forms, the at least one holographic notch filter and / or another notch filter is designed as a volume hologram. One advantage of designing a notch filter as a volume hologram can be, in particular, that such a can be produced particularly precisely and / or enables particularly precise filtering, in which the position and / or the full half-value width of the stop band can be set particularly precisely, ie in particular can be recorded in a holographic image carrier. Particularly steep flanks on the sides of the barrier tape can also be achieved with a notch filter designed as a volume hologram. In order to adapt in particular the filter effect in the stop band, the transmittance outside the stop band and / or the full half-value width of the stop band of a holographic notch filter designed as a volume hologram, the thickness of a layer of holographic material in which the volume hologram is recorded can be adjusted in some advantageous variants , For this purpose, the thickness can in particular be increased in order to achieve a stronger filter effect - that is to say a lower transmittance in the stop band - and / or a smaller full half-value width and / or steeper flanks in the stop band. Conversely, in particular the thickness can be reduced in order to increase the transmittance outside the stop band, an acceptance angle of the notch filter - for example by rotating the notch filter with respect to the light source or using a light source with divergent light beams, in the case of a holographic notch filter which records with planar light has been made possible - to enlarge and / or to widen the full half-value width of the stop band.

In some applications, a full half-width of the spectrum of the filtered light of 5 nm or less is required to reconstruct the hologram, while 10 nm, 15 nm or more than 20 nm may be sufficient for other applications. This can depend in particular on the complexity and / or the sharpness required for the reconstruction of the hologram and on the selected wavelength. For example, a headlight may require greater sharpness and thus a smaller full half-width than a rear headlight, brake light or direction indicator.

In some application forms, in which the at least one holographic notch filter is designed as a volume hologram, the at least one holographic notch filter is rotatably mounted relative to the light-emitting diode. The angle of incidence with which light emitted by the light-emitting diode strikes the notch filter can be changed by relative rotation, so that the stop band of the notch filter is shifted. In this advantageous manner, the blocking band of a holographic notch filter designed as a volume hologram can be displaced and its filtering action can thus be adjusted. An advantage of this adaptation can be, in particular, that the filtered part of the spectrum of the emitted light can be adapted for the respective application and / or within the application for certain cases. For example, when changing the LED of the light source, the filtering can be adapted to the respective spectrum of the LED. The light intensity of the reconstructed hologram can also be increased by less filtering and thus more light components over a larger spectral range, whereby the sharpness of the reconstructed hologram is reduced - or vice versa, the (depth) sharpness can be increased by a smaller spectral width and thus light intensity.

In some application forms, in which the at least one holographic notch filter is mounted rotatably relative to the light-emitting diode, the light source has a further holographic notch filter, which is recorded in a further holographic image carrier. In this advantageous manner, the filter effect of the at least one holographic notch filter can be changed by a relative rotation independently of the filter effect of the further holographic notch filter. In some advantageous variants, the additional notch filter can also be rotatably mounted, so that its filter effect can also be changed. In this advantageous manner, one or both sides of the spectrum of the filtered light can be set in an application-specific manner.

An advantage of an adjustability of the filter effect of the notch filter or of another notch filter can in particular also lie in the fact that such a light source with an adjustable filter effect can be produced at least essentially uniformly for different wavelengths and / or for different light-emitting diodes, as a result of which the production is more efficient and / or less expensive can be carried out.

In some application forms, the light source furthermore has a sensor device for detecting the light intensity of the emitted light after filtering. In addition, the light source has a control device which is set up to determine a value for the light intensity by means of the sensor device and to control the light-emitting diode based thereon in such a way that its (light) power is set to achieve a predetermined target value for the light intensity. In this advantageous manner, a specific target value for the light intensity can be achieved, with deviations, for example, due to production fluctuations in the light-emitting diode or due to aging of the light-emitting diode or due to a changed filtering of the emitted light by the control device - at least within the operating parameters of the light-emitting diode. can be compensated. As a result, an even and / or constant illumination - for example by means of a headlight with such a light source - or uniform illumination - for example of a vehicle with a rear light, a brake light or a direction indicator with such a light source. There can also be an advantage in that manufacturing can be simplified and / or manufacturing errors can be avoided, since manufacturing-related fluctuations in the components of the light source can be compensated for by the control device. An advantage of the detection in the light intensity after the filtering can also be that fluctuations in the filtering and / or in the spectrum of the emitted light can also be taken into account when regulating the light intensity.

A second further application relates to a holographic lighting device for a vehicle, in particular for a motor vehicle, the lighting device having a holographic image carrier for generating a lighting function of the lighting device and a light source for illuminating the holographic image carrier. The light source is designed according to the first further application.

The possible advantages, application forms or variants of the first further application mentioned above also apply accordingly to the holographic lighting device.

In some application forms, one or more holograms are recorded in the holographic image carrier to generate a lighting function.

In some forms of application, the holographic image carrier can be exchanged for generating a lighting function, as a result of which in particular different lighting signatures can be reconstructed.

In some forms of application, the holographic image carrier for generating a lighting function is integrally connected to the light-emitting diode, the notch filter or a housing of the lighting device, which in particular achieves particularly precise optics and / or increases the robustness - in particular weather resistance - of the lighting device.

In some application forms, the holographic image carrier has one or more holograms with one or more characteristic lighting signatures for generating a lighting function. In this advantageous manner, the surroundings of the lighting device can be illuminated with the characteristic lighting signatures, used to display certain driving conditions in a vehicle and / or to increase the recognition value.

A third further application relates to a method for generating light for the reconstruction of a hologram. In the method, light is emitted and the emitted light is directed onto at least one holographic notch filter, so that the emitted light strikes the notch filter at an angle of incidence. In addition, the emitted light is filtered by means of the at least one holographic notch filter. The at least one holographic notch filter for the angle of incidence has a stop band which overlaps the spectrum of the emitted light in such a way that the light after filtering by the notch filter at least essentially only has spectral components on one side of the stop band. Finally, the ratio of the full half-value width of the spectrum of the emitted light to the full half-value width of the stop band is less than eight, preferably less than three and more preferably less than one.

The possible advantages, application forms or variants of the previous further applications already mentioned above also apply correspondingly to the method for generating light for the reconstruction of a hologram.

A fourth further application relates to the use of a light source according to the first further application or the use of a method according to the third further application for generating a holographic projection with a holographic lighting device for a vehicle. The vehicle can in particular be a motor vehicle such as a passenger car, a train, an airplane or a motorcycle. In some variants, the holographic projection can also have a characteristic illuminated signature and in particular can project this illuminated signature onto a surface in the surroundings of the vehicle or into the three-dimensional space in the surroundings of the vehicle.

The possible advantages, application forms or variants of the previous further applications mentioned above also apply accordingly to their use.

In some application forms, the holographic lighting device can be designed according to the third further application.

Further advantages, features and possible applications result from the following detailed description of exemplary embodiments and / or from the figures.

The invention is explained in more detail below with reference to the figures using advantageous exemplary embodiments. The same elements or components of the embodiments are in Essentially identified by the same reference numerals, unless this is described differently or does not arise from the context.

• 1 eine Vorrichtung zum Herstellen eines holographischen Kerbfilters nach einer Ausführungsform;
• 2 ein Flussdiagramm eines Verfahrens zum Herstellen eines holographischen Kerbfilters nach einer Ausführungsform;
• 3 einen holographischen Kerbfilter nach einer Ausführungsform als Teil eines Bands mit einer photosensitiven Schicht;
• 4 eine Lichtquelle zur Rekonstruktion eines Hologramms nach einer Anwendungsform;
• 5 ein Flussdiagramm eines Verfahrens zum Herstellen von Laserlicht zur Rekonstruktion eines Hologramms nach einer Anwendungsform;
• 6A bis 6C Graphen zur Veranschaulichung von Eigenschaften und Funktionsweise von einer Lichtquelle nach einer Anwendungsform;
• 7 ein holographisches Anzeigesystem nach einer Anwendungsform;
• 8 eine weitere Lichtquelle zur Rekonstruktion eines Hologramms nach einer Anwendungsform;
• 9 ein Flussdiagramm eines weiteren Verfahrens zum Erzeugen von Licht zur Rekonstruktion eines Hologramms nach einer Anwendungsform;
• 10 A bis 10 D Graphen zur Veranschaulichung von Eigenschaften und Funktionsweisen einer weiteren Lichtquelle nach einer Ausführungsform; und
• 11 eine holographische Leuchteneinrichtung nach einer Anwendungsform.

Show, partly schematically:

• 1 an apparatus for making a holographic notch filter according to an embodiment;
• 2 a flowchart of a method of manufacturing a holographic notch filter according to an embodiment;
• 3 a holographic notch filter according to an embodiment as part of a tape with a photosensitive layer;
• 4 a light source for reconstructing a hologram according to an application form;
• 5 a flowchart of a method for producing laser light for the reconstruction of a hologram according to an embodiment;
• 6A to 6C Graphs illustrating the properties and functions of a light source according to an application;
• 7 a holographic display system according to an application form;
• 8th a further light source for the reconstruction of a hologram according to an application form;
• 9 a flowchart of a further method for generating light for the reconstruction of a hologram according to an embodiment;
• 10 A to 10 D Graphs for illustrating properties and functions of another light source according to an embodiment; and
• 11 a holographic lighting device according to an application.

The figures are schematic representations of various embodiments and / or exemplary embodiments of the present invention. Elements and / or components shown in the figures are not necessarily shown to scale. Rather, the various elements and / or components shown in the figures are reproduced in such a way that their function and / or their purpose can be understood by the person skilled in the art.

Connections and couplings between the functional units and elements shown in the figures can also be implemented as indirect connections or couplings. In particular, data connections can be wired or wireless, in particular as radio connections. Certain connections, for example electrical connections, for example for energy supply, may also not be shown for the sake of clarity. Furthermore, optical connections - for example between optical elements - which can be represented in particular as a straight light beam, can also be implemented in some variants by means of a light guide and / or by optical elements, such as mirrors, for deflecting light beams, such connections being used for the sake of clarity are not necessarily shown.

In 1 is a device 1 for producing a holographic notch filter with a predetermined stop band according to an embodiment of the present invention, shown schematically, in particular as a cross section.

In one embodiment, the device 1 a light source 2 , a rotatable cylinder 3 , a material feeder 6 and a detachment device 9 on. The rotatable cylinder 3 has a reflective surface all around 4 on, the rotatable cylinder 3 and the light source 2 are arranged so that one from the light source 2 generated exposure light a part of the reflective surface 4 illuminated and this part as a mirror 5 for the exposure light.

Illustrative are in 1 light rays of the exposure light as well as a band with a photosensitive layer are indicated, which, however, are not necessarily a component of the device 1 are.

The material feeder 6 is set up to provide the tape with the photosensitive layer and can have a container for holding the tape or a supply of tapes. In addition, the material feed device 6 set up part of the belt the rotatable cylinder 3 feed and as a holographic recording medium on the part of the reflective surface 4 , each as a mirror 5 acts to attach. In some variants, as in 1 shown, the respective part of the tape - which is to be used as a holographic recording medium - the mirror 5 to contact.

The rotatable cylinder 3 and the light source 2 are arranged so that from the light source 2 generated exposure light first passes through the holographic recording medium and thus acts as a reference wave, then from the mirror 5 is reflected and finally as an object wave - with the mirror 5 as a holographic object - again - this time from the other side - passes through the holographic recording medium, whereby in particular the reference wave and the object wave can interfere with each other.

The light source is in some advantageous variants 2 set up only that part of the reflective surface 4 and or only that part of the tape that has the reflective surface 4 contacted - or even only a part, in particular a longitudinal section thereof - to illuminate, as a result of which no interference occurs in particular in other parts of the band and the photosensitive layer there is not influenced or changed - that is to say in particular exposed. Accordingly, a beam path of the exposure light thus runs from the light source 2 for as a mirror 5 acting respective part of the reflective surface 4 , which passes through the holographic recording medium from a side of the holographic recording medium facing the light source, and runs after being reflected on the mirror 5 from there on and again through the holographic recording medium, the beam path this time from the other side - that is, the mirror 5 facing side of the holographic recording medium - passes through the holographic recording medium.

The light source 2 is also set up to generate an exposure light, the spectrum of which has those portions or wavelengths that are to be filtered with the holographic notch filter to be produced, so that the spectrum of the exposure light corresponds to the predetermined stop band of the holographic notch filter. Furthermore, the light source is set up to generate the exposure light with a coherence length which is at least as large as a first optical path length along the beam path from the holographic recording medium to the mirror 5 and from there to the holographic recording medium, which enables interference between the reference wave and the object wave.

In some advantageous variants, the light source 2 be further set up to also generate the exposure light with a coherence length which is less than 100 microns, whereby parasitic interference structures can be avoided. Furthermore, the light source 2 be set up to generate the exposure light with such a coherence length that it is only in one of the mirrors 5 facing region of the holographic recording medium interferes with each other, while the reference wave and the object wave in a more distant area at least essentially no longer interfere in the holographic recording medium due to lack of coherence, as a result of which a particularly homogeneous appearance of the holographic notch filter can be achieved. For this purpose, the coherence length of the exposure light can in some variants be smaller than the first optical path length and a single or a double layer thickness of the tape with the photosensitive layer or twice the distance of the photosensitive layer in the area which the mirror 5 contacted by the mirror 5 his.

In some advantageous variants, the light source 2 have a plurality of light-emitting diodes for generating the exposure light. The light-emitting diodes can also be arranged in one or more lines in order to illuminate the holographic recording medium with a higher intensity or over a larger area. Alternatively or additionally, the light-emitting diodes or possibly other units for generating exposure light - such as solid-state lasers - can be moved along a line in order to illuminate the holographic recording medium line by line or section by line.

In particular, a particularly smooth rotation of the rotatable cylinder 3 the rotatable cylinder 3 in some advantageous variants with a magnetic bearing 8th be stored.

As the rotatable cylinder rotates, another part of the tape becomes on the reflective surface 4 attached, that part of the reflective surface to which the further part of the tape is attached, then as a mirror 5 acts while the previously attached holographic recording medium, which is already exposed, from the rotating cylinder, ie its reflecting surface 4 is replaced.

In some advantageous variants, the device 1 also a detachment device 9 exhibit. This can also be a motor for driving the belt and, via the belt, the rotatable cylinder 3 exhibit. In this advantageous manner, the belt can be used to detach the device 9 pull, this along the rotatable cylinder 3 runs and contacts it and also moves due to the movement of the belt, whereby the rotatable cylinder - specifically that part that acts as a mirror 5 works - and that part of the band that is the mirror 5 contacted and each is the holographic recording medium, move together, whereby in particular the optical properties - especially the first optical path length - remain the same even when moving.

In some variants, the rotatable cylinder can have a circular base, which enables a particularly uniform rotation.

Alternatively, the rotatable cylinder can have a non-circular base surface in other variants - for example an ellipse or a polyhedron -, whereby the holographic notch filter or several holographic notch filters can be manufactured in sections and / or an easier detachment from the cylinder can be achieved.

The material feed device can be used to attach the respective part of the tape - especially to arrange the holographic recording medium so that the beam path runs before and after reflection through the holographic recording medium 6 in some variants an arrangement device 7 exhibit.

The material feed device can also be provided in some advantageous variants 6 or the arrangement device 7 be set up the belt opposite the rotatable cylinder 3 electrostatically charging, which in particular causes the tape or a part thereof - in particular the holographic recording medium - to adhere to the rotatable cylinder 3 is made possible and with which a particularly high mechanical stability - in particular with respect to the optical properties such as a stable first optical path length - can be achieved.

In 2 is a flowchart of a method 10 for producing a holographic notch filter, which has a predetermined stop band, according to an embodiment of the present invention.

In one embodiment, the method has 10 the procedural steps 13 . 14 . 15 . 16 . 17 . 18 and 19 on. The procedure 40 starts at the start of the process 11 and ends at the end of the procedure 12 ,

In some variations, you can perform the procedure 10 advantageously a device for producing a holographic notch filter according to an embodiment of the present invention, and in particular the device 1 according to 1 , be used.

In the procedural step 13 a tape with a photosensitive layer is provided.

In the procedural step 14 exposure light is generated by means of a light source, the spectrum of which corresponds to the predetermined stop band.

In the procedural step 15 part of the tape is attached as a holographic recording medium to a mirror which is part of a reflecting surface of a rotatable cylinder or a conveyor belt. The rotatable cylinder or the conveyor belt and thus the mirror are arranged in such a way that a beam path of the exposure light runs from the light source to the mirror and the beam path continues from there in accordance with a reflection of the exposure light on the mirror.

In the process step 17 when attaching the part of the tape as a holographic recording medium, the holographic recording medium is arranged such that the beam path runs through the holographic recording medium before and after reflection.

In the procedural step 16 the mirror is exposed with exposure light, the exposure light running from the light source through the holographic recording medium as a reference wave and striking the mirror, being reflected there and then again passing through the holographic recording medium as an object wave - namely with respect to the mirror.

This will in the process step 18 exposes the holographic recording medium by means of the exposure light as a reference wave and as an object wave which interfere with one another in the holographic recording medium.

Finally, in the process step 19 the holographic recording medium is then moved together with the mirror, so that when the process is repeated, a further part of the tape can be attached to a further part of the reflecting surface as a holographic recording medium. Alternatively or additionally and advantageously, the movement in the method step can 19 continuously, so that further parts of the tape are continuously attached as holographic recording medium to a further part of the reflecting surface, are exposed there and then, if appropriate, are detached from the reflecting film after exposure.

3 shows a holographic notch filter 66 with a predetermined barrier tape according to an embodiment of the present invention. The predetermined stop band is holographically recorded in the holographic notch filter in this way.

In 3 is the holographic notch filter 66 also as a possible variant as part of a band 60 with a photosensitive layer 62 , a part of which is produced as a holographic recording medium 64 has been used.

In one embodiment, the holographic notch filter 66 an optical grating in one area 67 which, in particular, is caused by interference from Reference wave and object wave has been recorded there, and another area 68 , which has no optical grating or at least no corresponding, regular interference pattern. In some variants, the area that forms the optical grating can be used in the manufacture 67 has closer to a mirror that has been holographically recorded as an object for producing the holographic notch filter than the other area 68 ordered.

Such a holographic notch filter can advantageously be used for various applications and forms of application, with such a holographic notch filter allowing efficient production and / or compliance with certain requirements, such as an appearance.

In 4 is a light source 110 for the reconstruction of a hologram according to an application form shown schematically, in particular as a cross section.

In one application example, the light source points 110 a laser device 112 and at least one holographic notch filter 116 on. The light source also points 110 in some variants another holographic notch filter 118 on. In some variants, the at least one holographic notch filter can be used 116 and / or the further holographic notch filter 118 be designed as a volume hologram. Even the light source 110 , as in 4 shown, a layer of holographic material 114 in which the at least one holographic notch filter 116 and / or the further holographic notch filter 118 are recorded. In this advantageous manner, several filter functions, ie the filter function of the at least one notch filter, can be implemented 116 and the other notch filter 118 integrate in an optical element.

According to some variants, the laser device 112 be designed and configured as a laser projector, in particular as a pico projector, to generate a laser light for at least one spectral range, a further spectral range and an additional spectral range. In particular for a colored reconstruction of the hologram, the at least one spectral range can lie in the wavelength range between 610 nm and 680 nm, so that light components from this spectral range are usually perceived in red; the further spectral range lies in the wavelength range between 500 nm and 560 nm, so that a light component in this spectral range is usually perceived as green; and the additional spectral range lies in the wavelength range between 410 nm and 490 nm, so that a light component in this spectral range is usually perceived as blue. In addition, the laser device is set up to generate the laser light in such a way that it has a first spectral line and a second spectral line in at least one spectral range and a third spectral line and a fourth spectral line in the further spectral range, while the laser light has a fifth spectral line in the additional spectral range.

In some variants, the laser projector has one laser per spectral range for generating the laser light with the at least one spectral range, the further spectral range and the additional spectral range. In addition, in some variants, the laser projector can have a plurality of optical elements, in particular lenses and / or mirrors, and can be designed to use the optical elements to guide laser light from the lasers to a common output for the laser light and to generate a laser light in which the individual ones Spectra of the respective laser are combined. The laser light can in particular be divergent, convergent or collimated or planar.

Illustrative are in 4 light rays of the laser light are also shown, the laser light being represented by 4 is divergent. In other variants, the laser light can also be convergent or collimated. The light source can also be used in some variants 110 have a collimator that is set up by the laser device 112 , in particular the laser projector, to bend divergent laser light so that it is a collimated laser light after diffraction by the collimator.

The laser device 112 and the two notch filters 116 and 118 are arranged so that the laser light hits the two notch filters and is filtered by them. Here, the at least one holographic notch filter 116 a stop band, which filters the second spectral line, and the further holographic notch filter 118 has a stop band that filters the fourth spectral line, so that the laser light after filtering through the two notch filters 116 . 118 at least essentially no longer has the second spectral line and the fourth spectral line. Accordingly, after filtering, the laser light can be used in variants with a laser projector, which initially generates five spectral lines - namely the first, second, third, fourth and fifth spectral line - after filtering at least essentially from three spectral lines - namely the first Spectral line, the third spectral line and the fifth spectral line - exist. In this advantageous way, it points from the light source 110 generated laser light for each spectral range, which is perceived as a color from red, green and blue, each on exactly one spectral line. This leaves construct a hologram in three colors and with mixed colors from these three colors - in particular by mixing light colors. In addition, double images per color can be avoided.

In 5 is a flowchart of a method 140 for generating laser light for the reconstruction of a hologram according to an application.

In an application example, the method shows 140 the procedural steps 146 . 147 and 148 on. The procedure 140 starts at the start of the process 142 and ends at the end of the procedure 144 ,

In some variations, you can perform the procedure 140 advantageously a light source for the reconstruction of a hologram according to an application form, and in particular the light source 110 according to 5 , be used.

In the procedural step 146 laser light is generated with at least one spectral range. The laser light has a first and a second spectral line in at least one spectral range and essentially consists of these two spectral lines in at least one spectral range.

In the procedural step 147 the generated laser light is directed onto at least one holographic notch filter. The at least one holographic notch filter has a stop band that filters the second spectral line.

In the procedural step 148 the laser light generated is filtered by means of the at least one holographic notch filter, the laser light after filtering by the notch filter at least essentially no longer having the second spectral line.

The method can be used in this advantageous manner 140 generate a laser light for the reconstruction of a hologram which does not have the second spectral line in the at least one spectral range and in particular in the at least one spectral range consists at least essentially only of the first spectral line, as a result of which a hologram can be reconstructed in this spectral range without the formation of double images and / or together with the usually narrow spectral width of the spectral lines of a laser - in this case in particular the first spectral line - a reconstruction of the hologram with a high depth of focus is made possible.

By generating the laser light so that the first spectral line lies in a certain area of the visible light spectrum - i.e. between 370 nm and 750 nm - the hologram can be constructed in such a way that it can be perceived in a certain (light) color.

In 6A is for illustration a spectrum of a three-color laser projector of a light source according to an application form, in particular according to the application form 4 , outlined. The wavelength of the emitted light is plotted along the abscissa in nanometers and along the ordinate the intensity at the respective wavelength in arbitrary units. In addition, the term “FWHM” denotes the full half-width of the spectrum of the light generated by the laser device, in particular the three-color laser projector, or the full half-width of the respective spectral line.

In some advantageous variants, the full half-width of one or more spectral lines can be less than 7 nm, preferably less than 5 nm and preferably about or exactly 3 nm.

The laser light can, as in 6A shown, have at least one spectral range, a further spectral range and an additional spectral range, the laser light in at least one spectral range having a first spectral line - identified by 131 - and a second spectral line - identified by 132 -, in the further spectral range a third spectral line - characterized by 133 - and has a fourth spectral line - identified by 134 - and in the additional spectral range has a fifth spectral line - identified by 135.

In some advantageous variants, the spectral distance between the first and the second spectral line and or the spectral distance between the third and the fourth spectral line can be greater than 2 nm, preferably greater than 4 nm and / or less than 20 nm, preferably less than 7 nm and / or about or exactly 5 nm.

In some advantageous variants, the spectral ranges can be selected in such a way that a colored - in particular a tri-color - reproduction or reconstruction of the hologram is made possible, that is, the spectral ranges are each in a wavelength range which is defined as a specific color - such as red, green or blue - is perceived. In particular, the at least one spectral range can be in a red-perceived spectral range, the further spectral range can be in a green-perceived spectral range and the additional spectral range can be in a blue-perceived spectral range.

In 6B is the filter effect of a holographic notch filter according to one application form, in particular according to 4 , illustrated. Again along the abscissa is the Wavelength plotted in nanometers, while the transmittance of the holographic notch filter is now plotted in percent along the ordinate and a 100% transmittance is identified. As illustrated here, the stop band of the holographic notch filter has a full half-width of 15 nm, the transmittance in the stop band being at least essentially 0%, rapidly increasing on the edges of the stop band and close to the rest of the wavelength range - that is, outside the stop band 100% transmittance lies. It goes without saying that the highest possible transmittance outside the stop band is required for a high luminous efficiency.

6C illustrates the filter effect of at least one notch filter and a further notch filter according to one application form, in particular according to one application form 4 , as well as one from a light source according to an application form, in particular according to 4 , generated laser light. The wavelength is plotted along the abscissa and the intensity in arbitrary units along the ordinate with respect to the laser light and the transmittance in percent with respect to the filter effect.

The transmittance of the at least one notch filter is plotted as a dotted line and identified by 136. The transmittance of the additional notch filter is plotted as a dashed line and marked 138.

To illustrate this, the 6A filtered laser light shown. The at least one holographic notch filter filters the spectrum of the laser light generated by the laser device, so that after filtering by the at least one holographic notch filter, the spectral line 132 no longer has, and the further holographic notch filter filters the laser light generated by the laser device so that it is the fourth spectral line 134 out 6A , no longer has. As a result, the laser light generated by the light source only has the first spectral line 131 , the third spectral line 133 and the fifth spectral line 135 on.

7 shows schematically, in particular as a cross section, a holographic display system 100 according to an application form.

In one application example, the holographic display system 100 a light source 110 as well as a holographic image carrier 120 on.

In some variants, the holographic display system 100 , as in 7 shown, set up to display a plurality of objects, in particular two objects, for displaying information, each of which can represent specific information.

This is in the holographic image carrier 120 a hologram in one area 123 for a first holographic object 103 recorded and in another area 125 another hologram 125 for another holographic object 105 recorded. By illuminating the respective area of the holographic image carrier 120 the respective hologram can be reconstructed and thus the respective object 103 . 105 are reproduced holographically.

Also shows the light source in some variants 110 several, in particular two, laser devices 112 , which are each controllable in order to generate a laser light with at least one spectral range.

The light source 110 also has a holographic image carrier 119 with a carrier plate 115 - about glass - and a layer 114 made of holographic material by the carrier plate 115 is worn on. In the shift 114 at least one holographic notch filter is made of holographic material 116 educated. That from the laser device 112 or the laser devices 112 Laser light generated in each case has a first spectral line and a second spectral line in at least one spectral range. In addition, the laser devices 112 and the holographic image carrier 119 so arranged that the laser light each on one of the laser devices on a region of the holographic notch filter 116 hits and is filtered by this. The at least one holographic notch filter 116 a stop band, which filters the second spectral line, so that the laser light after filtering through the notch filter 116 at least essentially no longer has the second spectral line.

In some variants, in which the holographic objects 103 . 105 The holographic display system can display pixels in three-dimensional space 100 be set up to display a variety of information - in particular at least 50, preferably at least 200 - Holographically reproducing objects and thus pixels, whereby in particular further holographic objects or information can be reproduced or represented by a combination of these pixels - in particular, so to speak, by a combination of 3D pixels. In some such variants, the image points can advantageously be recorded in the image carrier for reconstruction with diffuse light. The light source can be advantageous 110 or at least the holographic display system 100 have a diffuser. This can be between the holographic image carrier 119 and the holographic image carrier 120 be arranged.

Alternatively, this can also be part of one of the image carriers. In particular, the carrier plate 115 be designed as a diffuser.

With such a diffuser, in some variants, the light is first passed through the laser device 112 generated, then passes through the notch filter 116 and then hits the diffuser, especially the diffuser, as the primary image 115 , The diffuser then acts as a secondary light source, with a corresponding divergent light being emitted from each point of the diffuser, which light of the primary image strikes - these points therefore act in particular as point light sources - and onto the holographic image carrier 120 to meet. In variants in which the holographic objects each represent pixels and these pixels are arranged on a surface, in particular in a plane, in space or are reproduced holographically, the primary image can be holographically projected onto the surface in three-dimensional space in this advantageous manner ,

The holographic display system 100 also has a control device 106 and is set up to receive information to be displayed by means of the control device, to process this information and to use the one or more holographic objects to display the information to be displayed 103 . 105 play.

For this purpose, the control device can, in some variants, the laser devices 112 the light source 110 head straight for it.

In other variants, the control, as in 7 shown, also indirectly via a control device 108 respectively. Here is the control device 108 each set up the respective laser device 112 to be controlled in such a way that their power - ie their laser power - in accordance with the control by the control device 106 is set.

In some advantageous variants, the holographic display system 100 , especially the light source 110 , per laser device 112 one sensor device each 109 for detecting the light intensity of the respective laser device 112 have laser light generated for the at least one spectral range. This sensor device can be advantageous 109 in some variants after filtering through the holographic notch filter 116 be arranged. In addition, the respective control device 108 set up a value for the light intensity by means of the sensor device 109 to determine and based on this the respective laser device 112 to be controlled so that its laser light power is adjusted to reach a predetermined target value for the light intensity.

In such variants, the control device 106 the respective laser device 112 control by setting the predetermined target value for the light intensity. For example, this can be according to the operating parameters of the respective laser device 112 Set the maximum light intensity value and thus a holographic reproduction of the respective holographic object 103 respectively. 105 with maximum light intensity, or vice versa, set the predetermined target value to a very low value - for example to zero -, as a result of which the respective holographic object 103 . 105 is not reproduced - i.e. its information is not represented.

An advantage of the control device in variants with a plurality of laser devices, in particular for illuminating a part of the holographic image carrier and / or for reproducing one holographic object in each case, can in particular lie in the fact that the regulation of the light intensity enables relative regulation between the laser devices, whereby homogeneous illumination of the holographic image carrier and / or coordinated or defined brightnesses of the holographic objects can be achieved. The same applies to several spectral ranges, in particular for the reproduction of several colors.

In 8th is another light source 210 for the reconstruction of a hologram according to an application form schematically, in particular shown as a cross section.

In one application example, the light source points 210 a light emitting diode 212 , a collimator 214 and at least one holographic notch filter 222 on. The light source also points 210 in some variants another holographic notch filter 224 on. In some variants, the at least one holographic notch filter can be used 222 and / or the further holographic notch filter 224 be formed as a volume hologram and each or together, as in 8th shown in a layer of holographic material 220 be recorded.

Illustrative are in 8th also shown light rays, which the light emitting diode 212 upon activation - i.e. supply with suitable electrical energy - as well as the at least substantially parallel light rays after passage through the collimator 214 and the light after filtering through the two notch filters 222 and 224 , In the representation of 8th are the two notch filter 222 . 224 formed as reflection holograms, so that they reflect the spectral components of the light which are in the stop band, while they allow other spectral components to pass through. The light hits after the collimator 214 on the holographic notch filters 222 . 224 in as in 8th shown, a common angle of incidence α, which is also shown for illustration. An angle of incidence deviating from 90 ° α can be advantageous in order to prevent light reflected back from the notch filters, that is to say those parts in the spectral range which are in the stop band of the respective notch filter, from being returned to the rest of the optics, in particular the light-emitting diode 212 and / or the collimator 214 , to steer.

In some variants, the collimator 214 be designed as a converging lens, ie as a dioptric element. In order to enable a small installation space in particular and / or to achieve a high luminous efficiency, the collimator can be used in other variants 214 also be designed as a concave mirror, ie as a catoptric element. Furthermore, some variants cannot use a collimator 214 have, the holographic notch filter 222 and / or the further holographic notch filter 224 are designed to filter the light over a range of angles of incidence, which is limited by the so-called acceptance angle of the respective holographic filter. The holographic notch filter can also be used 222 or 224 have already been recorded for a divergent light. For this purpose, in particular, such a holographic notch filter can be recorded in a layer with holographic material, which is photosensitive before its development, by means of a light source whose emitted light beams diverge in such a way that their divergence follows the later divergence of the light beams of the light-emitting diode 212 , in particular at a predetermined distance between the light emitting diode 212 and the respective holographic notch filter 222 respectively. 224 equivalent.

In some advantageous variants, the light emitting diode 212 a high-performance light-emitting diode, which emits light with a high intensity. The LED can also 212 In some variants, it can advantageously be designed in such a way that it is suitable for use in a vehicle, in particular a motor vehicle, so that it is in particular a light-emitting diode that is suitable or approved for automobile construction. The following properties can be particularly suitable and advantageous, in particular for use in a vehicle: central wavelength 642 nm, spectral bandwidth, in particular full half width 20 nm, area of the chip of the light-emitting diode smaller than 0.25 mm ² ; and / or luminosity greater than 20 cd.

Also, in some variants, instead of a single light emitting diode 212 a plurality of light-emitting diodes are used, a corresponding collimator being used and / or the holographic notch filter 222 and optionally the holographic notch filter 224 are designed so that they are suitable for divergent light beams from several light emitting diodes.

The light source can also be used in some variants 210 be designed for a plurality of spectral ranges or a plurality of wavelength ranges, in particular in order to enable a hologram to be reconstructed using a plurality of colors. For this purpose, in some variants, at least one light-emitting diode can be used for the respective spectral ranges and the light source correspondingly for filtering light emitted by the respective light-emitting diode 210 have a respective holographic notch filter, which in some variants can advantageously be recorded in a common holographic layer. For a three-color display with the colors red, green and blue, the respective wavelengths of the respective light-emitting diodes can typically be in one of the following ranges: 610 to 680 nm; 500 to 560 nm; and 410 to 490 nm.

In 9 is a flowchart of another method 240 shown for generating light for the reconstruction of a hologram according to an application form.

In an application example, the method shows 240 the procedural steps 246 . 247 . 248 and 249 on. The procedure 240 starts at the start of the process 242 and ends at the end of the procedure 244 ,

In some variations, you can perform the procedure 240 advantageously a light source for the reconstruction of a hologram according to an application form and in particular a light source 210 according to 8th be used.

In the procedural step 246 light is emitted.

In the procedural step 247 the emitted light is directed onto at least one holographic notch filter, so that the emitted light strikes the notch filter at an angle of incidence.

In the procedural step 248 the emitted light is filtered by means of the at least one holographic notch filter, the at least one holographic notch filter for the angle of incidence having a stop band which overlaps with the spectrum of the emitted light in such a way that the light after filtering by the notch filter at least in the Has essentially only spectral components on one side of the stop band.

In some variants, the optional process step can be advantageous 249 the light already filtered by the at least one holographic notch filter can be filtered by another holographic notch filter. The further holographic notch filter is advantageously designed such that it has a stop band which lies on the other side of the spectrum of the emitted light, so that part of the spectrum of the emitted light lies between the stop bands of the at least one notch filter and the stop band of the further notch filter ,

In 10A is for illustration a spectrum of a light emitting diode of a light source according to an application form, in particular according to the application form 8th outlined. The wavelength of the emitted light is plotted along the abscissa in nanometers and along the ordinate the intensity at the respective wavelength in arbitrary units. In addition, the term “FWHM” denotes the full half-width of the spectrum of the light emitted by the light source. In some advantageous variants, the full half-width is less than or equal to 20 nm, the less the filter has to be filtered through the holographic notch filter, the smaller the full half-width of the emitted light, so that the light yield increases.

In 10B is the filter effect of a holographic notch filter according to one application form, in particular according to 8th , illustrated. The wavelength is again plotted in nm along the abscissa, while the transmittance of the holographic notch filter is now plotted in percent along the ordinate and a 100 percent transmittance is identified. As illustrated here, the stop band of the holographic notch filter has a full half-value width of 15 nm, the transmittance in the stop band being at least essentially 0%, rapidly increasing on the edges of the stop band and close to 100 in the remaining wavelength range - ie outside the stop band % Transmittance lies. It goes without saying that the highest possible transmittance outside the stop band is required for a high luminous efficiency.

In some variants, the full half-width of the notch filter can also be more than 15 nm, approximately 20 nm or 25 nm, or less than 15 nm, approximately 10 nm or 5 nm, the position of the stop band with respect to the wavelength and its full half-width being application-specific are to be selected such that a light emitted by the light source can be at least substantially completely filtered on at least one side of its spectrum and on the other hand the remaining light spectrum has a remaining full half-value width which is suitable for the reconstruction of the respective hologram and in particular for achieving the required depth of field is.

In 10C is the filter effect of at least one holographic notch filter and the filter effect of another holographic notch filter according to one application form, in particular according to 8th shown, the above description too 10B applies accordingly. In particular, in 10C the transmittance of the at least one holographic notch filter is shown as a dotted line and the transmittance of a further holographic notch filter is shown as a dashed line. As in 10C illustrated, the stop band of the at least one notch filter and the stop band of the further notch filter are spaced apart from one another, so that the transmittance is close to 100% in a region between the two stop bands.

Finally in 100 the filter effect of the two notch filters 10C on the spectrum of the light emitting diode 10A illustrated. Here, the at least one holographic notch filter filters the spectrum of the emitted light on the side with a lower wavelength and the further holographic notch filter filters the spectrum of light on the side with a longer wavelength. In this way, at least essentially only light from a spectral range passes through the two holographic filters combined with one another, which lies between the two stop bands. As a result, the full half-value width of the emitted light can be reduced from less than 15 nm, preferably between 5 nm to 10 nm, from the original 20 nm, as illustrated by way of example, to a full half-value width, depending on the position of the stop bands, so that the allows filtered light to reconstruct a hologram.

11 schematically shows a holographic lighting device 200 according to an application form. This can be designed for a vehicle, in particular for a motor vehicle.

In one application example, the holographic lighting device 200 a holographic image carrier 202 with a hologram recorded there for generating a lighting function of the lighting device and a light source 210 to illuminate the holographic image carrier 202 and thus for the reconstruction of the holographic image carrier 202 recorded hologram. Here is the light source 210 formed according to an application form and can in particular the light source 210 according to 8th correspond.

As in 11 shown, has the light source 210 a holographic layer 220 in which at least one holographic notch filter 222 is recorded. In addition, the light source points 210 a rotating device 228 on which is set up the holographic layer 220 and thus also the at least one holographic notch filter 222 relative to the light emitting diode 212 the light source 210 to twist. In this advantageous way, the angle of incidence α and thus the filter effect of the notch filter can be 222 change while moving his stop band.

That in the holographic image carrier 202 Recorded hologram is set up when illuminated by the light source 210 to create a characteristic illuminated signature. As a result, in particular a holographic projection of a previously recorded object can be generated, so that a characteristic shape and a characteristic illumination of a light cone can be generated for a headlight, for example. Accordingly, holographic objects, ie in particular characteristic symbols, can be represented in the case of brake lights, direction indicators or rear lights.

Illustrative are in 11 the light rays coming from the light emitting diode 212 are emitted, the light rays after filtering through the holographic notch filter 222 and the light rays after passing through the holographic image carrier 202 shown.

In some variants, the light hits the light emitting diode 212 without collimator on the holographic notch filter 222 so that the light rays are divergent. It should be noted that as long as the respective angles of incidence of the light rays are in the range of angles of incidence, which is due to the acceptance angle of the holographic notch filter 222 is limited, these can still be filtered accordingly with the respective stop band.

Also shows in some advantageous variants and as in 8th represented the light source 210 a control device 230 and a sensor device 232 on. The sensor device 232 is set up, the light intensity of the emitted light after filtering by the notch filter 222 capture. The control device 230 is set up a value for the light intensity by means of the sensor device 232 to determine and based on this the LED 212 to be controlled so that its power is adjusted to reach a predetermined target value for light intensity. This can be particularly advantageous in combination with the twisting of the holographic notch filter 222 be, as a result, depending on the correspondingly changed position of the stop band relative to the spectrum of the light emitting diode 212 emitted light the light intensity after filtering through the filter 222 can vary and by the control device 232 this variation can be compensated for.

In some variants, the predetermined target value can also be changeable according to predetermined criteria by means of a further device or based on a further method, so that the resulting light intensity can be changed according to the predetermined criteria. Such predetermined criteria can in particular be the distance of a further vehicle following the vehicle with the lamp device, the brightness of an environment of the lamp device or the vehicle and / or a deceleration or acceleration of the vehicle.

While exemplary embodiments, possible applications and exemplary applications have been described in detail, in particular with reference to the figures, it should be pointed out that a large number of modifications are possible. It should also be pointed out that the exemplary designs and applications are only examples that are not intended to restrict the scope of protection, the application and the structure in any way. Rather, the person skilled in the art is given a guideline for the implementation and / or application of at least one exemplary embodiment by the preceding description, various modifications, in particular alternative or additional features and / or modifications of the function and / or arrangements of the described components, as desired by the person skilled in the art can be made without deviating from the subject-matter as defined in the appended claims and its legal equivalents and / or leaving the scope thereof.

Claims (17)

A method (10) for producing a holographic notch filter (66, 116, 222) with a predetermined stop band, the method (10) comprising: - (14) generating exposure light by means of a light source whose spectrum corresponds to the predetermined stop band; - (16) illuminating a mirror with the exposure light, the light source and the mirror being arranged such that a beam path of the exposure light runs from the light source to the mirror and the beam path continues from there in accordance with a reflection of the exposure light at the mirror; - (17) Arrange a holographic recording medium so that the beam path before and after the Reflection runs through the holographic recording medium; and - (18) exposing the holographic recording medium by means of the exposure light; and wherein: a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium is less than a coherence length of the exposure light; and the coherence length of the exposure light is less than a second optical path length along the beam path from the light source to the mirror. Method (10) according to Claim 1 , wherein: the holographic recording medium has a layer thickness; the first optical path length is related to a side of the holographic recording medium facing the mirror; and the coherence length of the exposure light is smaller than the sum of the first optical path length and twice the layer thickness. Method (10) for producing a holographic notch filter with a predetermined stop band, in particular according to Claim 1 or 2 , the method comprising: - (13) providing a film or tape with a photosensitive layer, wherein part of the film or tape is attached (15) or attached to a mirror as a holographic recording medium; - (14) Generating exposure light by means of a light source, the spectrum of which corresponds to the predetermined stop band, the mirror being arranged in such a way that a beam path of the exposure light runs from the light source to the mirror and the beam path continues in accordance with a reflection of the exposure light at the mirror of continues from there; - (18) Exposing the holographic recording medium by means of the exposure light after attachment, the beam path running before and after reflection through the holographic recording medium and a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium being less than is a coherence length of the exposure light; and - detaching the holographic recording medium from the mirror after exposure. Method (10) according to Claim 3 wherein the mirror is part of a reflective surface of a rotatable cylinder or conveyor belt. Method (10) according to Claim 4 , wherein: the rotatable cylinder or the conveyor belt are moved continuously, and further parts of the belt with the photosensitive layer as a holographic recording medium are attached to further parts of the reflecting surface acting as a mirror; the holographic recording medium is moved (19) together with the mirror and exposed during movement; already exposed parts of the tape or the holographic recording medium are detached from the mirror; and the movement takes place in such a way that the first optical path length remains at least substantially constant. Method (10) according to Claim 4 , wherein: the rotatable cylinder or the conveyor belt is moved step by step and further parts of the belt with the photosensitive layer as a holographic recording medium are attached to further parts of the reflecting surface acting as a mirror; the holographic recording medium is moved (19) together with the mirror; the holographic recording medium is exposed before or after moving; and already exposed parts of the tape or the holographic recording medium are detached from the mirror. Method (10) according to one of the Claims 5 or 6 , wherein when moving or at least before and after moving a second optical path length along the beam path from the light source to the mirror on which the holographic recording medium is attached remains at least substantially constant. Method (10) according to one of the preceding claims, wherein the holographic recording medium is arranged or attached to the mirror in such a way that it contacts the mirror and the first optical path length and or its variation is at least a factor of two smaller than one of the wavelengths in the spectrum of the exposure light. The method (10) according to any one of the preceding claims, wherein: the first optical path length is between 0 µm and 500 µm; and the coherence length of the exposure light is greater than the first optical path length and greater than 10 μm and / or less than 5000 μm. Method (10) according to one of the preceding claims, wherein: the exposure light is generated by means of the light source, in that the light source first generates a light with a first spectral range and this light is filtered by means of an additional notch filter; and the additional notch filter has a stop band which overlaps the first spectral range in such a way that the light after filtering by the additional notch filter at least essentially only has spectral components on one side of the stop band. Device (1) for producing a holographic notch filter with a predetermined stop band, comprising: a light source (2) for generating an exposure light whose spectrum corresponds to the predetermined stop band; a mirror (5) which is arranged such that a beam path of the exposure light runs from the light source to the mirror when the light source is being operated and the beam path continues from there in accordance with a reflection of the exposure light at the mirror; and an arrangement device (7) which is set up to arrange a holographic recording medium such that the beam path runs before and after reflection through the holographic recording medium in order to expose the holographic recording medium; wherein a first optical path length along the beam path from the optical recording medium to the mirror and from there to the holographic recording medium is less than a coherence length of the exposure light; and wherein the coherence length of the exposure light is less than a second optical path length along the beam path from the light source to the mirror. Device (1) for producing a holographic notch filter with a predetermined stop band, comprising: a light source (2) for generating an exposure light whose spectrum corresponds to the predetermined stop band; a rotatable cylinder (3) or a conveyor belt each with a reflecting surface (4), which is arranged such that part of the reflecting surface acts as a mirror (5) for the exposure light and a beam path of the exposure light from the light source to Mirror runs and the beam path continues from there according to a reflection of the exposure light on the mirror; Material feed device (6) which is set up to feed a part of a belt with a photosensitive layer to the rotatable cylinder (3) or the conveyor belt and to attach it to the mirror as a holographic recording medium; wherein the material feed device (6) and the mirror (5) are further configured to attach the holographic recording medium to the mirror such that the beam path runs before and after reflection through the holographic recording medium to expose the holographic recording medium; and wherein a first optical path length along the beam path from the holographic recording medium to the mirror and from there to the holographic recording medium is less than a coherence length of the exposure light. Device (1) for producing a holographic notch filter with a predetermined stop band, comprising: a light source (2) for generating an exposure light whose spectrum corresponds to the predetermined stop band; a material feed device (6) which is set up to feed a part of a tape with a photosensitive layer to an arrangement device of the device and to laminate the respective part of the tape to be fed on one side with a reflective film or to coat with a reflective material or such a tape to supply, which already has a reflective surface; wherein the arrangement device is set up to arrange the respectively fed part of the tape as a holographic recording medium such that a beam path of the exposure light when the light source is operated runs from the light source through the holographic recording medium, then the exposure light by means of the reflecting surface, the reflecting film or the reflective material is reflected, so that this or this acts as a mirror, and the beam path again runs through the holographic recording medium in accordance with the reflection in order to expose the holographic recording medium; and wherein a first optical path length along the beam path from the photosensitive layer of the holographic recording medium to the mirror and from there to the photosensitive layer is less than a coherence length of the exposure light. Device (1) for producing a holographic notch filter with a predetermined stop band, in particular according to Claim 11 to 13 , wherein the device (1) is set up, a method (10) according to one of the Claims 1 to 10 perform. Holographic notch filter (66, 116, 222), which by means of a device (1) according to one of the Claims 10 to 14 or by a method (10) according to one of the Claims 1 to 10 has been manufactured. Holographic notch filter (66, 116, 222) according to Claim 15 , which has no parasitic interference structures and appears macroscopically homogeneous. System (100, 110, 140, 200, 210, 240) for the reconstruction of a hologram, in which a holographic notch filter according to Claim 15 or 16 is used as a component of a light source, the light source generating or being set up to reconstruct the hologram.

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