Method for producing a double hologram, method for duplicating a double hologram, security document with a double hologram and device for producing a double hologram

Abstract

Method for producing a double hologram (100) comprising the steps: Providing a recording material (20); Generating coherent light (40) which is split into a reference portion (60) and an object portion (50); guiding the object portion (50) onto an object (80) such that object light (55) emanating from the object (80) strikes a side (21) of the recording material (20) facing the object (80) and radiates through it; Guiding the reference portion (60) so that this reference portion (60) impinges on a side (22) of the recording material (20) facing away from the object (80) at a reference angle (β) and illuminates this; so that an interference pattern created with the object light (55) is recorded in the recording material (20), characterized in that the reference portion (66) emerging from the facing side (21) of the recording material (20) is reflected back into itself so that the reflected reference portion (67) acts on the interference pattern.

Description

The invention relates generally to security elements and methods for producing them and, in particular, to a method for producing a double hologram, to a security document having such a double hologram and to a device for producing a double hologram.Security elements are physically formed units which comprise at least one security feature. A security feature is a feature that is used to detect authenticity and non-tamper evidence of an article associated with the security element and its security feature. Security elements can be semi-finished products which are incorporated into an object or are finished security articles, for example. Security documents and value documents represent examples of security elements. Security documents can likewise also comprise security elements, for example patches applied in the form of incorporated substrate layers, etc.A group of security elements and security features can be verified optically. Verifying is understood to mean checking a security feature for its presence and / or the integrity of the security feature and of the security element in which the security feature is formed. The group of optical security features and security elements comprises security features designed in a diffraction-optical manner. These diffract light used for verification. A large group of diffraction elements used in value and / or security documents and security elements are holograms.A hologram is understood to mean a structure which is generated or can be generated by interference from coherent light and is stored in a recording material. Holograms are distinguished into so-called thin and thick holograms. The distinction is made as to which material thickness the layer in which the interference structure is stored has. If the layer thickness is in the order of magnitude of the wavelength of the light with which the interference structures are produced or can be produced, this is referred to as a thin hologram. If, on the other hand, the material thickness of the recording material in which the interference structures are stored is in the order of magnitude of the multiple, for example ten times, of the wavelength of the light with which the interference structures are produced or can be produced, this is referred to as a so-called thick hologram or volume hologram. The properties of thin holograms and thick holograms differ substantially in part. Volume holograms or thick holograms are distinguished, for example, by the fact that they have a high angle and wavelength selectivity. This means that a volume hologram recorded with one wavelength is also reproducible only with one wavelength. Reproducing a hologram is understood to mean generating a light radiation on the hologram when the hologram is illuminated with reference light. This generated light radiation is also referred to as reconstruction light radiation. In the reproduction or reconstruction of a hologram, a light radiation is generated which comprises the information of an object light radiation, the interaction of which with the reference light radiation during the production of the hologram has generated the interference structures which are stored in the hologram.The prior art describes a wide variety of different holograms which are used, for example, in security documents.DE 10 2012 216 219 A1 describes a master for producing a volume reflection hologram individualized in an individualized region, comprising a carrier, at least one diffraction structure which is arranged on the carrier or is formed therein and covers an individualized region, the at least one diffraction structure reflecting coherent light of a wavelength which impinges on the diffraction structure from a predetermined direction of incidence in a predetermined direction of emission, the master comprising a reflection element which specularly reflects directed light in accordance with the geometric optics. Furthermore, a method for producing individualized volume holograms and a method for producing a master are described.DE 10 2014 217 099 A1 proposes a method for producing a security hologram having a volume transmission hologram, which method comprises the steps of: providing a recording material, irradiating the recording material with coherent object light and reference light from a first exposure side of the recording material, wherein the information to be stored in the volume transmission hologram is transported in the object light, wherein the recording material is brought with the first exposure side into contact with a contact side of the hologram master and coherent irradiation light is produced and the hologram master is irradiated with the coherent irradiation light from an irradiation side opposite the contact side and the object light is produced at the at least one diffraction structure of the hologram master via a diffraction of the coherent irradiation light, which enters from the hologram master and the recording material from the first exposure side, wherein a part of the irradiation light is not diffracted and exits from the hologram master as the reference light and enters the recording material from the first exposure side, so that the object light and the reference light interfere in the recording material and expose the volume transmission hologram into the recording material. Furthermore, a device for producing such a security hologram and a security document are described.EP 0 896 260 A2, for example, describes an apparatus for the production of individual holograms for securing documents. Described is a device for producing holograms from a master hologram of a ground glass disk recorded at one or more wavelengths and one or more reference angles. Stereoscopic and colored individualized holograms can be produced using this master hologram by the contact copying method. The apparatus has a radiation source for laser radiation for irradiating the master and a film. In order to make the holograms with various stored information simple to fabricate, a modulation means, particularly a liquid crystal display (LCD), is provided to modulate the coherent laser radiation.With the apparatus described in the prior art holograms are produced which are volume reflection holograms. In a volume reflection hologram, the reconstruction light is irradiated from one side onto the hologram, i.e. the recording material in which the interference information is stored, and the reconstructed light radiation is generated in a reflecting manner on the same side on which the reconstruction light is irradiated, i.e. in a reflecting manner. Such security features are used, for example, on German personal documents such as passports or personal identification numbers and show, inter alia, the light image of the identification number holder and personal information such as, for example, its name. In this case, the ground glass screen contained in the master is copied with different brightness in a spatially resolved manner in a contact copying method in order to generate the light image.In order to achieve good protection and a great workability of security elements and security features, it is sought by security element manufacturers to design security features that are as complex as possible. The object of the invention is thus to specify an improved optical holographic security element and security feature and a method for producing the same and a device with which security elements and security features are created which have novel additional optical features to the previously known features for a security option for security documents and articles.The object is provided according to the invention by a method for producing a dual hologram having the features of claim 1, a method for duplexing a dual hologram having the features of claim 7, a security document having a dual hologram having the features of claim 8 and a device for producing a dual hologram having the feature of claim 9. Advantageous embodiments of the invention are evident from the dependent claims.The invention is based on the idea of reflecting the reference light passing through the recording material back into itself during the exposure of a volume reflection hologram, so that the reflected reference light acts on the interference pattern. From a double hologram produced in this way it is possible to produce further double holograms in a so-called contact copying process.Furthermore, it is provided that a security document having such a dual hologram, which is produced according to one of the described methods, is produced by assembling the recording material in which the dual hologram is stored with other substrate layers to form a document body, wherein the other substrate layers are each transparent to the wavelength of reconstruction light with which the dual hologram is reconstructed in a region which is superimposed or superimposed on a recording region of the dual hologram in the recording material.An apparatus for producing a double hologram in an exposure step comprises a holder for receiving recording material in a material plane. The apparatus further comprises a light source for generating coherent light and a beam splitter for splitting the coherent light into an object portion and a reference portion. Furthermore, the device comprises optical guide elements which are arranged such that the object portion can be guided onto an object for illuminating or illuminating the object and light emanating from the illuminated object impinges on an object side of the holder and can pass through the latter. The optical guide elements are furthermore arranged such that the reference portion impinges on a side of the holder facing away from the object side and at a reference angle with respect to the material plane and passes through the holder. Furthermore, it is provided that a reflection device is formed at a distance from the object side of the holder, which reflection device reflects the reference light, which has transmitted through the holder, back into itself.The advantage of the invention is that a new complex security feature is easily produced, in which the hologram can be reconstructed both in reflection and in transmission.It has been found to be particularly advantageous that at least the light of the reference portion is parallelized via a beam shaping optical unit. This collimated light then impinges on the recording material and can also be reflected back into itself very effectively after transmission of the recording material by a planar reflection means, optimally by a reflection means matched to the wavelength used for exposure. A light radiation consisting of parallelized light beams can be reflected back into itself particularly easily and efficiently with a planar reflection device.In order to enable individualization and storage of any desired information in such a dual hologram, it is provided in one embodiment that the object comprises a surface pattern generating device which modulates an intensity of the object light emanating from the object in a spatially resolved manner over a surface of the object.In a very simple embodiment, the object can comprise a transmission mask which comprises transparent regions and completely opaque regions.In further specialized methods, it can be provided that the spatially resolved intensity modulation of the object can be carried out with a local light modulator (SLM). Different spatially resolved light modulators, such as LCD screens, but also so-called LCOS (liquid crystal on silicon) etc., are used for this purpose.In order to increase perceptibility of the stored information and "to loosen" the angular selectivity of the volume hologram generated with respect to the reconstruction of the hologram, it is provided in one embodiment that the object comprises a diffuser. For example, a diffuser can be arranged adjacent to a mask that modulates the object light radiation of the object. At each location at which it is illuminated, this preferably expands the incident light into a certain light cone, for example in such a way that each point on the surface of the diffuser acts as a Lambert radiator.In order to conceal the information as much as possible in the hologram, it is provided in one embodiment that the light emanating from the object is guided via a converging lens arrangement, in one focus of which the recording material is arranged. In one possible variant, the object, for example a diffuser illuminated via a spatial light modulator, is arranged in the other focus of the converging lens arrangement. The diffuser can be, for example, a scattering disk.In order to obtain sufficient flexibility in the exposure of the object into the recording material, it is provided in one embodiment that the reflection of the reference portion radiating through the recording material takes place at a distance from the recording material on the side of the recording material facing the object.On the one hand, it is possible to expose double holograms directly in the manner described. In mass production, however, it is also possible to use a double hologram produced in this way as a hologram master or a proportion of a hologram master, optionally with further diffractive structures which are formed as a hologram or in some other way on the hologram master. The dual hologram of the hologram master can then be duplicated in a contact copying method in such a way that a recording material is applied to a contact side of the master, which is the side which was remote from the object during the creation of the dual hologram, coherent reconstruction light which is suitable for reconstructing the dual hologram is generated, leading reconstruction light is applied to the hologram master through the recording material at a reconstruction angle which corresponds to a reference angle during the production of the dual hologram, such that a copy of the hologram master is produced in the recording material. By means of such a contact copy, which corresponds to the duplication of a reflection volume hologram, the dual hologram according to the invention can thus be duplicated in a simple and cost-effective manner.In order to achieve individualization during duplication, it is possible to modulate the reconstruction light via a local light modulator. Preferably, the reconstruction light is likewise a reference light radiation consisting of parallelized light beams.According to the invention, there is thus provided a security document having a dual hologram, wherein the dual hologram is produced according to the method described above and is integrated into a document body in which the recording material in which the dual hologram is stored is joined together with other substrate layers to form a document body, wherein the other substrate layers are each transparent to the wavelength of reconstruction light with which the dual hologram is reconstructed in a region which is superimposed or superimposed on the recording region of the dual hologram in the recording material. In the transparent region of the security document, which is also referred to as window region, since this is transparent to light which is not diffracted by the double hologram, the double hologram can be reconstructed on the one hand in a reflection geometry and on the other hand, when radiating from the opposite side of the security document through the document, the transmission hologram which is likewise stored can be reconstructed.Such a double hologram is produced with an apparatus in an exposure step. The apparatus comprises a holder for receiving recording material in a material plane. The apparatus further comprises a light source for generating coherent light and a beam splitter for splitting the coherent light into an object portion and a reference portion. The device also comprises optical guide elements which are arranged such that the object portion can be guided onto an object for illuminating or illuminating the object and object light emanating from the illuminated or illuminated object impinges on an object side of the holder and can pass through the latter. The optical guide elements are furthermore arranged such that the reference portion impinges on a side of the holder applied from the object side at a reference angle with respect to the material plane and passes through the holder. Furthermore, a reflection device is formed at a distance from the object side of the holder, which reflects back into itself the reference portion which has transmitted through the holder. A mirror can be used here, for example. If the reference light is parallelized before the recording material is irradiated, this mirror can be a planar mirror.In a development of the apparatus, it is provided that the object comprises a surface pattern generating device which, during the illumination or illumination with the object portion of the coherent, spatially resolved, modulates an intensity of the object light emanating from the object over a surface of the object, and furthermore preferably comprises a diffuser which diffusely expands the spatially resolved modulated object light and is arranged between the surface pattern generating device and the holder, wherein a converging lens arrangement is additionally arranged between the diffuser and the holder, in one focus of which converging lens arrangement the diffuser lies and in the other focus of which converging lens arrangement the material plane of the holder lies.The invention is explained in more detail below with reference to a drawing. The following are shown here: FIG. 1 shows a schematic representation of an apparatus for producing a dual hologram; FIG. 2 shows a further embodiment for producing a dual hologram; FIG. 3 is a schematic view of a hologram master; FIG. 4 is a schematic illustration of an apparatus for duplexing a dual hologram; FIG. 5 is a view of a document with a dual hologram in which the dual hologram is reconstructed in reflection; and FIG. 6 is a view of a document with a dual hologram, in which the dual hologram is reconstructed in transmission.FIG. 1 schematically illustrates an apparatus 1 for producing a dual hologram 100. The apparatus 1 comprises a holder 10 on which a recording material 20 is held in a material plane 12 of the holder 10. The recording material 20 may be any suitable material in which interference patterns of coherent light may be stored as a hologram. Particular preference is given to layers of photopolymers. The holder 10 is transparent to light at least in a region 11 which is used for exposing the double hologram 100 into the recording material 20. For example, the holder 10 can have a transparent plate 13 in the region 11, against which the recording material 20 bears. The recording material 20 can be provided in the form of a continuous film, optionally provided with a carrier and protective layer, or also in the form of sheet-like foils, also optionally provided with a carrier and / or protective layer.The apparatus 1 further comprises a light source 30 that generates coherent light. The light source 30 is preferably designed as a laser 31. The light source 30 generates coherent light 40, which in the embodiment shown is converted, for example, via beam shaping elements 35 into a widened, parallelized light beam 41 from individual parallel light beams. The light 40 or the widened parallelized light beam 41 is divided at a beam splitter 71 into an object portion 50 and a reference portion 60. The reference portion 50 is used to illuminate or illuminate an object 80. The object light 55 emanating from the object 80 impinges on the recording material 20 and irradiates it and likewise the holder 10. It passes through the volume 23 of the recording material 20 and exits the recording material 20 on the opposite side 22.The reference portion 60 of the light 40 is guided via optical guide elements 70, for example mirrors, prisms, etc., in such a way that it passes through the holder 10 as reference light 65 and impinges on the opposite side 22 of the recording material 20 at a reference angle β, passes through the volume 23 and exits the recording material 20 on the side of the recording material 20 facing the object 80. In the illustrated embodiment, the reference angle β measured against the surface normal 26 of the applied side 22 of the recording material 20 is 0 degrees. In the volume 23 of the recording material 20, the object light 55 and the reference light 65 interfere to store a volume reflection hologram of the object 80 in the recording material 20 in the form of an interference pattern.The object 80 can in principle be any desired object. However, objects in which the object light 55 emanating from the object 80 is significantly modulated with respect to intensity over a surface of the object 80 are particularly suitable. The object 80 can therefore comprise, for example, a spatial light modulator 85, for example in the form of a transmission mask. In order to be able to provide successively produced dual holograms 100 with individual information, that is to say to be able to easily change the object which is exposed or the information thereof, the object 80 preferably comprises a controllable spatial light modulator 85, which can be designed, for example, as an LCD screen, or else as an LCOS (liquid crystal on silicon) or the like. However, the transmission mask of the light modulator 85 can also be only a static mask in simple embodiments.In addition to the volume reflection hologram of the object 80, however, in the embodiment shown a transmission hologram is also stored in that the reference light 66 emerging from the side 21 of the recording material 20 facing the object is reflected back into itself via a reflection device 90 and penetrates as reflected reference light 67 into the volume 23 via the side 21 of the recording material 20 facing the object 80 and influences the formation of the interference pattern with the object light 55 there. A distance 91 of the reflection means 90 from the recording material 20 is preferably larger than a beam diameter 69 of the reference light 66 / 67.In an exposure step, a volume reflection hologram and a volume transmission hologram are thus exposed into the recording material 20. This yields the dual hologram 100 which can be used as a security element in security products. The reference angle β shown can also be chosen differently from the embodiment shown.Since volume holograms exhibit high wavelength and angle selectivity, reconstruction is possible only with suitable light of one wavelength and at defined angles. In order to mitigate the angular selectivity, it is provided in some embodiments that the object additionally comprises a diffuser 87, for example in the form of a diffuser plate. This has the result that the light is emitted from individual locations from the surface of the object in each case into a cone region. The angular selectivity of the generated hologram due to the holography process is not immediately changed thereby, but a hologram of an object which emits light in different directions is recorded. During the reconstruction, this leads to the observation being possible in a larger angular range.In FIG. 2 a further embodiment is shown which differs from the embodiment according to FIG. 1 in that for the exposure of the dual hologram between the object and the recording material a converging lens or converging lens arrangement 110 is arranged, in one focus 111 of which the recording material 20 is located. In the embodiment shown, the diffuser 87 of the object 80 is located at the other focus 112 of the converging lens or converging lens arrangement 110. With this Fourier geometry, a hidden hologram is obtained.FIG. 3 shows a schematic illustration for a hologram master 200 which comprises a dual hologram 100 as a constituent. The dual hologram 100 produced by the above-described method in an exposure step is integrated into the hologram master 200 such that a side 21 of the recording material facing the object during production faces a top side 210 of the hologram master. In addition to the developed recording material 20', the hologram master comprises, for example, an additional support layer 220. This is preferably formed from transparent material.FIG. 4 schematically illustrates an embodiment of a device 300 with which the dual hologram 100 can be duplicated in a hologram master 200 which is formed, for example, similarly to the hologram master 200 according to FIG. 3. The hologram master 200 is arranged on a holder 310 in a material plane 312 in such a way that an upper side 210 of the hologram master 200 is facing away from the holder 310. In contact with the upper surface 210 of the hologram master 200, a recording material 20 is placed.A light source 330 generates reconstruction light 340, the wavelength of which is adapted such that it can reconstruct the dual hologram 100 stored in the hologram master 200. The wavelength of the reconstruction light 340 can deviate slightly from the wavelength of the light 40 with which the dual hologram 100 of the hologram master 200 is produced according to one of the devices according to FIG. 1 or FIG. 2, since shrinkage or swelling processes can occur during the development and / or fixing of the hologram, which shrinkage or swelling processes lead to the wavelength required for the reconstruction deviating slightly from the wavelength with which the hologram is originally exposed. Alternatively or additionally, in such a case, the angle at which the reconstruction light irradiated for the reconstruction is irradiated onto the dual hologram during the reconstruction can also be adapted a little.A beam shaping device 335 is used to expand and parallelized reconstruction light 365 from the reconstruction light 300 which corresponds in its properties, apart from the abovementioned possibly necessary deviation in the wavelength, to the reference light during the exposure of the dual hologram 100 of the hologram master 200. This is radiated onto the recording material 20 via an upper side 21 of the recording material 20 at the reconstruction angle γ, which corresponds to the reference angle β during the production of the dual hologram 100 of the hologram master 200. The reconstruction light 365 penetrates the volume 23 of the recording material and exits from the recording material on the opposite side 22 and enters the hologram master 200 via its upper side 210 into the volume 23' by storing the dual hologram 100 of the hologram master 200. The reconstruction light reconstructs the dual hologram 100 so that the light radiation 375 representing the information stored in the dual hologram 100 is reconstructed into the recording material 20 and interferes there with the reconstruction light 365 in order to generate the duplicated dual hologram 100.FIGS. 5 and 6 each schematically show a security document 400 into which a dual hologram 100 is integrated as a security element. The dual hologram 100 is formed in a window region 410 in each case. In FIG. 5, a reference light beam 365 is guided onto the upper side 405 of the document body 402 of the security document 400. The result in reflection is the information 420, for example a writing BDR, which is exposed as writing into the dual hologram 100 via the spatial light modulator 85 (spatial light modulator) during production. The information (more precisely a center of the information representing the stored object) is to be observed at an object reconstruction angle α' with respect to a surface normal 425 of that side of the dual hologram 100 which faces the top side 405 of the security document 400. The object reconstruction angle α' corresponds to the object angle α in the manufacture of the hologram master 200 (see below. FIG. 1 or FIG. 2 ). In the window region 410, the security document 400 is transparent over the entire volume.FIG. 6 shows the situation in which reconstruction light 365 is radiated via the bottom 406. This results in a projection of the information 420 on a screen 430. The novel security element can thus be checked in that both in reflection and in transmission the same information 420 stored in the dual hologram can be reconstructed on a screen 430. Here too, the information is to be observed at the object reconstruction angle α' with respect to the surface normal of that side of the dual hologram 100 which faces the top side 405 of the security document 400.List of reference characters1 Device 10 Holder 11 Region 12 Material plane 13 Transparent plate 20 Recording material 20' Side 22 Facing side 22 Facing side 21 Facing developed recording material 21 Volume 25 Surface normal of the facing side 26 Surface normal of the facing side 30 Light source 31 Laser 35 Beam shaping elements 40 Light 41 Widened parallelized light beam 50 Object portion 55 Object light 60 Reference portion 65 Reference light 66 Emerging reference light 67 Reflected reference light 69 Beam diameter 70 Optical guide elements 71 Beam splitter 80 Object 85 Spatial light modulator (SLM-spatial light modulator) 87 Diffuser (scattering disk) 90 Reflection device 91 Distance 100, 100' Dual hologram 110 Converging lens arrangement 111 Focus 112 Other focus 200 Hologram master 210 Upper side 220 Carrier layer 300 Device 310 Holder 312 Material plane 330 Light source 340 Reconstruction light 335 Beam shaping device 365 Expanded and parallelized reconstruction light 375 Light radiation 400 Security document 402 Document body 405 Upper side 406 Lower side 410 Window region 420 Information 425 Surface normal 430 Screen α Object angle α' Object reconstruction angle β Reference angle γ Reconstruction angle

Claims

Method for producing a dual hologram (100) comprising the steps of: providing a recording material (20); generating coherent light (40) which is divided into a reference portion (60) and an object portion (50); guiding the object portion (50) onto an object (80), such that object light (55) emanating from the object (80) impinges on a side (21) of the recording material (20) facing the object (80) and transmits it; guiding the reference portion (60), such that this reference portion (60) impinges on a side (22) of the recording material (20) facing away from the object (80) at a reference angle (β) and transmits it; so that an interference pattern arising with the object light light (55) is recorded in the recording material (20), characterized in that the reference portion (66) emerging from the facing side (21) of the recording material (20) is reflected back into itself, so that the reflected reference portion (67) acts on the interference pattern.Method according to Claim 1, in which the reference light is parallelized via a reference light optical unit.Method according to either of Claims 1 and 2, characterized in that the object (80) comprises a surface pattern generating device which modulates, in a spatially resolved manner, an intensity of the object light (55) emanating from the object (80) over a surface of the object (80).The method of any preceding claim, wherein the object (80) comprises a diffuser (87).Method according to one of the preceding claims, characterized in that the object light (55) is guided through a converging lens arrangement (110), in one focus (111) of which the recording material (20) is located and in the other focus (112) of which the object (80) is located.Method according to one of the preceding claims, characterized in that the reference portion (66) is reflected back at a distance, in particular at a distance which corresponds to at least one order of magnitude of a beam diameter of the reference portion (60), from the facing side (21) of the recording material (20).Method for duplexing a dual hologram (100') comprising the steps of: providing a hologram master (200) which comprises or is a dual hologram (100') to be duplexed produced by the method according to one of Claims 1 to 6, wherein a contact side (210) of the hologram master (200) is that side which was facing an object (80) during the production of the dual hologram (100), arranging a recording material (20) in contact with the hologram master (200) on the contact side (210) of the hologram master (200), generating coherent reconstruction light (365) which is suitable for reconstructing the dual hologram (100'), guiding the reconstruction light (365) through the recording material (20) at a reconstruction angle (γ), which corresponds to a reference angle (β) during the production of the dual hologram (100') on the hologram master (200), so that a copy of the hologram master (200) is produced in the recording material (20).Security document (400) having a dual hologram (100), characterized in that a dual hologram (100) produced by a method according to one of Claims 1 to 6 or 7 is integrated into a document body (402) by joining a recording material (20), in which the dual hologram (100) is stored, to form the document body (402) with other substrate layers, the other substrate layers each being transparent in a region which is superimposed on or superimposed by the recording region of the dual hologram (100) in the recording material (20), to the wavelength of reconstruction light (365) with which the dual hologram (100) can be reconstructed.Apparatus for producing a dual hologram (100) in an exposure step comprising a holder (10) for receiving recording material (20) in a material plane (12); a light source (30) for generating coherent light (40); a beam splitter (71) for splitting the coherent light (40) into an object portion (50) and a reference portion (60) and optical guide elements (70) which are arranged such that the object portion (50) can be guided onto an object (80) for illuminating or illuminating the object (80), and object light (55) emanating from the illuminated or illuminated object (80) impinges on an object side of the holder (10) and can emit light therethrough, and the reference portion (60) impinges on a side of the holder (10) facing away from the object side at a reference angle (β) with respect to the material plane (12) and emits light through the holder (10), characterized in that a reflection device (110) is formed at a distance from the object side of the holder (10), which reflection device reflects a reference light (66) which has emitted through the holder (10) back into itself.Device (1) according to Claim 9, characterized in that the object (80) comprises a surface pattern generating device which, during the illumination or illumination with the object component (50), modulates an intensity of the object light (55) emanating from the object (80) in a spatially resolved manner over a surface of the object (80), and a diffuser (87) which diffusely expands the spatially resolved modulated object light (55) and is arranged between the surface pattern generating device and the holder (10), wherein a converging lens arrangement (110) is additionally arranged between the diffuser (87) and the holder (10), in one focus (111) of which the material plane (12) of the holder (10) and the other focus (112) of which the diffuser (87) lies.

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