Exposure table for a hologram exposure machine and method for introducing a volume reflection hologram into a film section

Abstract

Exposure table (100) for a hologram exposure machine (300), with a holding device (102) in which a master receptacle (154) is formed or provided, which is designed to receive a master (104), and with a film guide designed to guide a hologram film (200) relative to the holding device (102) and to position a film section (202) to be exposed in an exposure area (204) relative to the master (104) for hologram exposure, characterized by the fact that the holding device (102) is formed as a revolver (114) with a plurality of radially oriented master mounts (154) which is rotatably mounted perpendicular to the optical axis of the hologram exposure.

Description

[0001] The invention relates to an exposure table for a hologram exposure machine, comprising a holding device in which a master frame is formed or provided, configured to receive a master, and a film guide configured to guide a hologram film relative to the holding device and to position a film section to be exposed in an exposure area relative to the master for hologram exposure. The invention further relates to a method for introducing a volume reflection hologram into a film section of a hologram film.

[0002] It is known from the prior art to integrate holograms as security elements into security documents or valuable documents. Security elements are entities that possess at least one feature that makes it difficult to unauthorizedly duplicate, imitate, and / or falsify an object in which the security element is integrated. Holograms are used as security elements, for example, in passports or identity cards. However, they are also used in banknotes, driver's licenses, visas, other tokens, labels or tickets, credit cards, bank cards, telephone cards, and similar items.

[0003] Volume holograms represent a special group of holograms. In a volume hologram, a diffractional structure of the hologram is stored within the volume of the holographic recording material, as can be seen, for example, in the publications DE 10 2012 215 540 A1, DE 10 2007 042 385 A1, and DE 10 2007 042 386 A1. Holographic exposure films, usually supplied on rolls, are typically used as recording materials for volume holograms in valuable and / or security documents. These exposure films are suitable for storing interference structures whose characteristic dimensions lie in the range of the wavelength of the light used to record or reconstruct the hologram.

[0004] DE 103 43 323 A1 describes a device for carrying out a stamp lithography process, i.e. a device for creating a structure on a substrate, in particular on a wafer.

[0005] In DE 10 2018 206 404 A1, a projection exposure system for semiconductor lithography, i.e. also for the structuring of wafers, is described, which provides a heating device for the uniform heating of the optics.

[0006] DE 10 2005 034 991 A1 describes a beam forming system for a lighting system for a microlithographic projection exposure system, and thus also for a system for structuring a wafer.

[0007] German patent DE 10 2013 200 980 A1 describes a device for the subsequent holographic marking of a composite object and a corresponding method. The device shown in this publication has a support plate onto which the composite object, namely the future identification, security, or other document, can be placed. The composite object includes a transparent section that allows modulated light to pass through to a photosensitive area of ​​a hologram layer within the composite object. To expose a volume reflection hologram in this photosensitive area, a master film, supplied on a roll, is rolled over the composite object and smoothed with a roller.

[0008] German patent DE 10 2010 014305 A1 describes a method and a device for producing contact copies of reflection volume holograms. In this method, a holographic film is guided by a drum, where it is brought into contact with and exposed to at least one hologram master. In a contact copying process, the holographic exposure film is positioned in front of a master containing diffraction structures that are to be "transferred" to the holographic exposure film. Thus, in the contact copying process, the diffraction structures of the master are copied into the holographic film. For this purpose, coherent light is shone through the holographic film, which is positioned in close proximity to or in contact with the master, and onto the master. The diffraction structures in the master diffract the light in such a way that the diffracted light is reflected back into the holographic film.There, it interferes with the coherent light used to illuminate the master. An interference pattern thus forms in the holographic film, determined by the light diffracted by the master. When the holographic film is developed and reconstructed, the reconstruction is identical to that observed when the master is illuminated. A hologram, also known as a Denisyuk hologram, is stored in the holographic film; this is a volume reflection hologram. It is understood that the incident light must have a suitable wavelength (or wavelengths) and a suitable direction (or directions) of incidence so that diffraction at the diffraction pattern occurs as desired. A method for producing a master and a contact copying method are described in EP 0 896 260 A2.

[0009] The holographic features on the exposure film cannot be captured, or can only be captured incorrectly, if the holographic film is not positioned perfectly flat, bubble-free, and creased relative to the master during exposure. Bubbles or creases can cause unwanted reflections during exposure.

[0010] Furthermore, exposing different holograms requires having different masters available, often resulting in very long setup times for converting an exposure machine to expose a second hologram onto the hologram film. This is even more problematic if the exposure machine is to be used to create holograms for different card formats, such as ID-1, ID-2, or ID-3 formats.

[0011] It is therefore the object of the present invention to provide an exposure table and a method for introducing a volume reflection hologram into a film section which take into account at least one of the aforementioned disadvantages.

[0012] This problem is solved by an exposure table having the features of claim 1 and by a method having the features of claim 9. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0013] The exposure table features, in particular, a holding device formed as a turret with multiple radially oriented master frames, mounted to rotate perpendicular to the optical axis of the hologram exposure. This allows the master required for hologram exposure to be selectively positioned within the exposure area. Furthermore, this configuration offers the advantage that multiple masters can be provided by the holding device on a single exposure table. The turret-shaped holding device provides a simple way to insert different volume reflection holograms—even those of different formats—into a section of hologram film located within the exposure area.

[0014] A simplified master change for hologram exposure is advantageous. Therefore, the revolver can be configured with a plate from which the master images extend perpendicularly. This plate is mounted on a rotating bearing, allowing it to rotate around an axis perpendicular to its surface. Typically, this axis is aligned perpendicular to the optical axis of the hologram exposure.

[0015] Since the turret's masters can have different dimensions, the turret's weight distribution must be appropriately adjusted. In this context, it is advantageous if the master receptacles are distributed along a master section of the plate's circumference, and if a counterweight is present on a section of the turret's plate's circumference that is complementary to the master section.

[0016] It is essential to ensure that material and costs can be saved. In this context, it is therefore advantageous if the exposure table, particularly the turret plate, has a mechanism for fixing the turret's rotational position. This mechanism is formed by a number of detents corresponding to the number of master exposures, as well as by at least one detent element. The detent element should be adjustable between a position disengaged from the detents, allowing rotation of the turret, and a position engaged in one of the detents, preventing rotation. This mechanism for fixing the turret's rotational position allows the desired masters to be selectively positioned within the exposure area in order to copy the structures associated with each master onto the hologram film.Adjusting the locking mechanism enables the turret to rotate, allowing for quick and precise master changes. The locking mechanism can be adjusted manually, pneumatically, or electrically. The turret's rotation can also be controlled manually, pneumatically, or electrically.

[0017] The exposure table for a hologram exposure machine preferably comprises a compressed air device associated with the holding device, which is designed as a turret. This compressed air device is configured to fix the film section, at least temporarily, to the master located in the exposure area and held in the holding device by means of a vacuum. Such a vacuum ensures that the film section is fixed flat and, in particular, free of gas inclusions relative to the master, thereby significantly reducing the reject rate of exposed holograms. Additionally, the film section is positioned completely flat, free of bubbles and creases, and in particular, motionless or optically stable relative to the master located in the exposure area, thus enabling the reliable embedding of volume reflection holograms into the hologram film.

[0018] The master of a hologram exposure machine is typically made of a material that may have sharp edges around its circumference. These edges can scratch the hologram film as it is transported over the master and the holding device. To counteract this problem, the compressed air system is preferably designed to provide, at least temporarily, an overpressure such that the transport of the hologram film relative to the master is supported by a cushion of air. In other words, the compressed air system is designed to provide a supply of compressed air that pressurizes the hologram film on the side facing the master, thus effectively preventing damage to the film.

[0019] To securely fix the film section to the master located within the exposure area during exposure, it has proven advantageous for the compressed air system to consist of a plurality of gas passage arrangements, for each master frame or the corresponding master frame captured therein to be assigned at least one of the gas passage arrangements, and for the compressed air system to include at least one channel that is fluidically connected exclusively to the at least one gas passage arrangement located within the exposure area. In other words, the channel is sealed off from the master frames not located within the exposure area and / or the respective master frames captured therein.The plate with its gas passage arrangements and the channel of the compressed air devices thus form a kind of multi-way valve, which is designed to be fluidically connected only to the master or master receiver that is located in the exposure area.

[0020] A reliable installation of the film section on the master is achieved by the gas passage arrangement framing the master circumferentially, and by the gas passage arrangement being formed by a slot or by a bore arrangement comprising several bores (bore array).

[0021] Since a vacuum can often be provided more easily with compressed air than with a vacuum pump, it has proven advantageous for the compressed air system to include a pneumatic Venturi nozzle for generating the negative pressure. Thus, compressed air can be easily introduced into the ejector via the vacuum ejector formed in this way, where it is accelerated by a drive nozzle (Venturi nozzle) with a cross-sectional constriction. This increases the dynamic pressure and decreases the static pressure of the air. After passing through the drive nozzle, the accelerated air expands, creating a vacuum. Additionally, air is drawn into the ejector through the vacuum port, which is fluidically connected to the gas passage assembly. This air, along with the drawn-in air, exits the ejector through the silencer. This provides a simple variant of the compressed air system for optionally—if necessary—Depending on a suitable position of valves - to provide a negative pressure or a positive pressure on the circumference of the master.

[0022] To ensure that any remaining gas inclusions between the section of the hologram film to be exposed and the master located in the exposure area are eliminated before the hologram is exposed, it has proven advantageous to have a stripping device to strip the section of the film to be exposed onto the master.

[0023] This design offers the advantageous possibility that the application device comprises a carriage that is movable between two stops, on which a pressure roller is mounted rotatably on a pivot axis and interacts with the film section. This pressure roller can thus be rolled over the film section, thereby removing any gas inclusions between the master and the hologram film. Furthermore, this design offers the advantageous possibility that the application device can be rolled over the film section alternately, i.e., starting both upwards and downwards from the master.

[0024] To ensure the smoothest possible transport of the hologram film, it is advantageous if the carriage is mounted with limited pivoting capability around a travel axis oriented perpendicular to the axis of rotation of the pressure roller, thus allowing the pressure roller to be adjusted between a raised and a lowered position. In this context, it is possible to have a control cam, particularly near or at each stop, designed to adjust the pressure roller between the raised and lowered positions.

[0025] To adjust or vary the force exerted by the pressure roller on the film section, it is useful to have a spring assembly on the side of the carriage facing away from the master. This spring assembly sets or specifies the pressure of the pressure roller on the master or on the film section located on the master. The pressure force of the pressure roller is determined by the moment of the spring force around the axis of travel.

[0026] In order to compensate for tolerance variations, in other words to provide compensating movements for the pressure roller, it is possible for the pressure roller itself to be rotatably mounted on a holding arm, which is fixed to the slide by means of a pivot axis oriented perpendicular to the axis of rotation of the pressure roller in such a way that the holding arm and thus the pressure roller are mounted with limited pivoting relative to the slide.

[0027] To ensure that the hologram film does not rub against either the holding device or the master held in the holding device during transport, it has proven advantageous for the film transport device to include a film lifting mechanism that is adjustable between a raised position, corresponding to a transport configuration, and a lowered position, corresponding to an exposure configuration. This design also allows the hologram film to be held relative to the master before or during its fixation in such a way that the surface of the film section to be exposed and the surface of the master are oriented at an acute angle to each other or away from each other. Such a "ramp" or...Such a fictitious "wedge" allows air bubbles to be expelled or any other gas inclusions to be avoided sufficiently well during subsequent fixing with suction air, as these are pushed away from the acute angle, especially in those cases where an additional stripping device is used to fix the film section to the master. To be able to provide such a "wedge" both in and against the film transport direction, the transport mechanism can also include a second film lifting mechanism that is adjustable between a raised position, corresponding to a transport configuration, and a lowered position, corresponding to an exposure configuration.

[0028] To ensure the smoothest possible transport of the hologram film, it is advantageous if the first and / or second film lifting device includes a film lifting roller that rotates around an axis. The film lifting roller can be used to raise or lower the hologram film.

[0029] For improved guidance, especially for improved holding of the hologram film, it is advantageous if the first film lifting device and / or the second film lifting device includes a guide roller arranged parallel to the axis of the film lifting roller, each of which is rotatably mounted on a lever arm that can pivot to a limited extent about the axis.

[0030] When exposing the hologram film, it is necessary and desirable that the film be dust-free. Therefore, it is advantageous to have a cleaning device designed to spray the section of the hologram film to be exposed with ionized air on the side facing the master, particularly during transport. This also serves to discharge the film statically.

[0031] This ionized air can also be used to provide an air cushion during transport, for which purpose the cleaning device in particular comprises a first spray nozzle for ionized air oriented at least partially, but preferably predominantly in a film transport direction, and wherein the cleaning device comprises a second spray nozzle for ionized air oriented at least partially, preferably predominantly, against the film transport direction.

[0032] For a compact, symmetrical design of the exposure table, it is advantageous if the first spray nozzle is arranged upwards with respect to the holding device, and if the second spray nozzle is arranged downwards with respect to the holding device.

[0033] The advantages and advantageous embodiments described in connection with the exposure table according to the invention also apply equally to the method according to the invention. This method comprises, in particular, the following steps: - Rotating a holding device with a plurality of master images until a master desired for hologram exposure is located in an exposure area, - Transporting the film section to be exposed into the exposure area using a film transport device, - simultaneous or subsequent lifting of the hologram film by means of a film lifting device and forming an acute angle between the facing surfaces of film section and master, - Applying the film section to the master starting from an acute angle using a pressure roller, and - Exposure of the hologram in the film section.

[0034] This method offers the advantage that the desired master for hologram exposure can be selectively positioned within the exposure area by rotating the holding device, while simultaneously ensuring bubble-free fixation of the hologram film to be exposed. This drastically reduces any potential reject rate.

[0035] It is advantageous to apply a vacuum to or around the master before and / or during the mounting process, thereby drawing the film section against the master, and to roll the pressure roller over the film section a second time before the hologram film is exposed. This ensures secure adhesion of the film section to the master, and the double pass minimizes, in particular reduces to zero, the number of potential gas inclusions between the hologram film and the master.

[0036] To avoid intrinsic movement of the hologram film, particularly the formation of Newton's rings, it is advantageous to reduce the vacuum before or during exposure. Preferably, the hologram film is positioned without pressure relative to the master during exposure.

[0037] The present invention is explained in more detail below with reference to the figures, the examples shown being merely illustrative and not representing any limitation as to the scope of the described invention. Specifically, the figures show: Fig. 1 a schematic representation of an exposure machine for exposing a volume reflection hologram in a hologram film, Fig. 2 a side view of an exposure table with the pressure roller in the right end position, Fig. 3 another one, Fig. 2 corresponding view with the pressure roller in left end position (intermediate position), and Fig. 4 another one, Fig. 2 corresponding view with the pressure roller in its right starting position and lowered film lift mechanism for exposure.

[0038] In Fig. Figure 1 schematically shows a hologram exposure machine 300 for exposing holograms in a hologram film 200. Such a hologram exposure machine 300 is also called a holographic exposure machine.

[0039] The hologram exposure machine 300 comprises an exposure device 302 shown in the drawing above and an exposure table 100 shown in the drawing below.

[0040] Holograms are exposed using coherent light. For this purpose, the exposure device 302 has a light source 304, which in this case is designed as a CW laser. "CW" stands for "continuous wave" and means "wave emitted at a constant rate over time." It is possible that the light source 304 is a pulsed laser. The light 400 from the laser light source 304 has a first polarization state. A beam guiding optic 306 is used to guide the light 400. In the illustrated exposure device 302, the light from the light source 304 is first guided, optionally with the aid of a beam shaping device 322 for beam expansion, particularly in a spatial direction, onto a deflection and scanning device 310 of the beam guiding optic 306.This deflection and scanning device 310 comprises a galvanometer scanner and a mirror 308 coupled to the galvanometer scanner, by which the incident light 400 is deflected. In a first position, the mirror 308 is shown by a solid line, while in a second position it is shown as a dashed line. By moving the mirror 308, an exposure of the hologram corresponding to a "scan," in particular a line scan, can be achieved. In other words, the hologram film 200 is "scanned" to expose the hologram. Different deflection and scanning devices 310 for the light 400 can also be used.

[0041] The deflected light 400 is guided onto a polarization-dependent beam splitter cube 312 of the beam guiding optics 306. This cube consists of a first prism and a second prism, at whose interface a polarization-dependent beam splitting occurs. A beam splitter plate can also be used instead of prisms. Light 400 of the first polarization state is deflected at this interface. Light of a further polarization state, orthogonal to the first polarization state, can, however, pass through the interface.

[0042] The light 400 deflected at the interface of the polarization-dependent beam splitter cube 312 is directed onto a spatial light modulator 314, which is designed as a so-called liquid-crystal-on-silicon (LCoS) light modulator. The light modulator 314 comprises a silicon layer 316, from which incident light 400 is reflected. Electronic switching elements are formed on this silicon layer 316, which are used to switch liquid crystal cells 318 arranged in front of the surface of the silicon layer 316 used for reflection. The individual liquid crystal cells 318 can be individually switched to different states. Typically, an array of liquid crystal cells 318 is present, such that further rows of liquid crystal cells 318 are arranged either extending outwards or inwards from the plane of the paper.Depending on the respective switching state of the liquid crystal cells 318, the polarization state of the transmitted light 400 is either changed or remains unchanged, thereby spatially modulating the light 400. For simplicity, it is assumed here that in a first switching state, the light 400, which strikes the light modulator 314 in a first polarization state, undergoes a complete polarization change as it passes through a liquid crystal cell 318 (which it traverses twice due to reflection at the surface of the silicon layer 316). The resulting change in polarization is such that the light 400 is subsequently polarized in a further polarization state orthogonal to the first polarization state. This polarization-modulated light 400 passes through a transparent protective disk 320 of the spatial light modulator 314, with, in particular, an exit surface of the protective disk 320 being oriented parallel to the reflective surface of the silicon layer 316.The surface normal of the light modulator 314 is therefore orthogonal to both the exit surface of the protective disc 320 and the reflective surface of the silicon layer 316.

[0043] After exiting the light modulator 314, the modulated light again strikes the polarization-dependent beam splitter 312. Depending on its polarization state, the modulated light 400 reflected back from the LCoS may or may not pass through the interface of the beam splitter 312. If, as in the example shown, the modulated light 400 has been converted into a further polarization state orthogonal to the first polarization state due to the first switching state of the liquid crystal cell, it can pass through the interface of the polarization-dependent beam splitter cube 312. This allows it to be directed, possibly with the aid of a polarization filter 324, further towards the exposure table 100, in particular into an exposure area 204.The portions of the light 400 that are still in the first polarization state and arrive at the polarization-dependent beam splitter cube 312 are deflected at its interface and therefore do not proceed further towards the exposure table 100 located below the exposure device 302. The polarization-dependent beam splitter cube 312 thus spatially modulates the intensity of the light 400 depending on the modulated polarization state.

[0044] In the description of the exposure device 302, it has been assumed up to this point that the spatial light modulator 314 rotates the polarization state of the light by 90 degrees or leaves it unchanged. However, changes are also possible that cause a rotation of the polarization direction between 0 degrees and 90 degrees. All these rotations result in the light exhibiting a changed amplitude and thus a changed intensity of the further polarization state. Depending on the angle of rotation, these vary and increase with the amount of rotation between 0 degrees and 90 degrees. This makes it possible to expose "grayscale" images.

[0045] The exposure table 100 has a holding device 102 in which a master 104 is mounted. The master 104 comprises a substrate, which is generally made of glass or another material. Other substrate materials are also possible, for example, metals. Preferably, at least one optically active layer, for example, a diffraction layer, is applied to the substrate, which comprises a diffraction pattern to be copied. In this case, the diffraction layer of the master 104 comprises a volume reflection hologram, which is to be copied.

[0046] It can be seen that the exposure machine 300, in particular the exposure table 100, comprises a film transport device 106, which is configured to transport the hologram film 200 relative to the holding device 102 and thus relative to the master 104 located in the exposure area 204. A film guide forms part of the film transport device 106. The film transport device 106 is therefore designed to pick up the holographic film and to hold and / or guide the film during the exposure of the hologram. In the illustrated exposure machine 300, the film transport device 106 comprises a film reel 110 on which the hologram film 200 is provided. After exposure, this is wound onto a further film reel 118.If necessary, the exposed hologram film 200 passes through a section for hologram development, during which thermal treatment is applied to the hologram film 200 to develop the hologram within the film before the exposed hologram film 200 is rewound onto the next film reel 118. The hologram film 200 is guided in a typical manner by means of film guide rollers. It can be seen that the hologram film 200 extends over the area of ​​the master 104, meaning that the film transport device 106 is designed to position a film section 202 to be exposed relative to the master 104. The volume reflection hologram is exposed, or thus copied, into this film section 202. To ensure reliable exposure of the hologram, the hologram film 200 rests against the master 104 during the exposure process.This system allows for the suppression of intrinsic movements of the holographic film, which increases the achievable diffraction efficiency of the produced hologram.

[0047] During exposure, the modulated light 400, which has a further polarization state, passes through the film section 202 of the hologram film 200 to be exposed and is reflected back by the optically active structure of at least one optically active layer of the master 104, e.g., diffracted in the case of an optically active layer designed as a diffraction layer. The reflected light (not shown) then interferes in the hologram film 200 with the modulated light 400 coming from the light modulator 314. This causes the optically active structure, e.g., the diffracting structure, of the master 104 to be exposed into the hologram film 200. Depending on the spatial modulation, the optically active structure is either exposed and copied pixel by pixel, or not exposed and therefore not copied. This results in a copy of the optically active structure, for example, a copy of a volume reflection hologram of a ground glass screen.

[0048] The present invention relates to the design and operation of the exposure table 100, which is used in the Fig. Figures 2 to 4 show the details in a side view. The holding device 102 shown here is designed in the manner of a revolver 114 and has a total of four receptacles for a master 104. A different number of master receptacles 154 is possible, so that fewer or more than four master 104s can be arranged on one and the same holding device 102. In order to protect the very sensitive edges of the master 104, each receptacle of the holding device 102, which is designed as a revolver 114, is such that the respective master 104 is recessed relative to the holding device 102 or its master receptacle 154, or lies at most in the same plane with the latter.

[0049] The holding device 102, i.e., the turret 114, can be aligned with its multiple master mounts 154 such that each master 104 can be selectively placed in the exposure area 204, so that, in other words, the master 104 required for hologram exposure, with its master mount 154, is selectively positioned in the exposure area 204. The turret 114 has a rotary bearing 156, which allows it to rotate about a perpendicular axis with respect to the optical axis of the hologram exposure.

[0050] It can be seen that the turret 114 comprises a plate 140, from which the master mounts 154 extend perpendicularly and to which the rotary bearing 156 is assigned. For suitable weight distribution, the master mounts 154 are arranged distributed on a master section 164 of the circumference of the plate 140, with a counterweight 166 being located on a section of the circumference of the plate 140 that is complementary to the master section 164.

[0051] The exposure table 100 shown also includes a device (not shown in detail) for determining the turret's rotational position, which is, for example, associated with a plate edge of the plate 140. This device for determining the turret's rotational position is formed by a number of detent positions corresponding to the number of master frames 154 and by at least one detent element, wherein the detent element is adjustable between a position disengaged from the detent positions, allowing rotation of the turret, and a position engaged in one of the detent positions, preventing rotation of the turret. The adjustment of the detent element is, for example, actuated by pressure medium, in particular pneumatically. Motorized, in particular electromechanical, adjustment is also possible.

[0052] The film transport device 106 comprises a first film lifting device 138 located upstream of the master 104. Alternatively or additionally, it is possible to provide a second film lifting device located downstream of the master 104 ( Fig. 1) Each film lifting device 138 comprises a film lifting roller 142 and a guide roller 144. The film lifting roller 142 is arranged parallel to the axis of the guide roller 144. The guide roller 144 is itself rotatably mounted on a lever arm 146, which is pivotable to a limited extent about the axis of the film lifting roller 142. For this purpose, the respective film lifting device 138 has correspondingly arcuate slots. The adjustment of the lever arm 146 can be actuated by pressure medium, in particular pneumatically. The raising and lowering of the film lifting device 138 is also actuated by pressure medium, in particular pneumatically. The film lifting device 138 of the film transport device 106 ensures a minimum distance between the holding device 102 and the hologram film 200 during transport, so that the latter is not damaged.This distance can be, for example, between 0.4 millimeters and 1.1 millimeters, which makes the exposure table 100 and thus the exposure machine 300 formed with it very space-saving and compact.

[0053] To expel gas inclusions between the hologram film 200 and the master 104, a winding device 120 is also provided to wind the film section 202 to be exposed onto the master 104. This winding device 120 is formed by a carriage 124 that is movable between two stops, on which a pressure roller 122 is mounted, rotatably mounted on a pivot axis and interacting with the film section 202 during winding. This carriage 124 is shown in the illustration. Fig. 2 shown in its right end position before the first stripping.

[0054] On the side of the carriage 124 facing away from the master 104, a spring arrangement is assigned which sets or specifies the contact pressure of the pressure roller 122 on the master 104 or on the film section 202 located on the master 104.

[0055] The holding device 102, designed as a revolver 114, is associated with a compressed air device 108, which is configured to fix the film section 202, at least temporarily, to the master 104 held in the holding device 102 and located in the exposure area 204, by means of a vacuum. Each master 104 in the master frames 154 has a circumferential slot around it, thus forming a gas passage arrangement 112. The gas passage arrangement 112 therefore surrounds the respective master 104 and thus ensures that the film section 202 to be exposed adheres to the master 104 without air bubbles.In this case, the compressed air device 108 can additionally be used to temporarily provide overpressure such that the transport of the hologram film 200 relative to the master 104 in the exposure area 204 is supported by an air cushion, thus further preventing damage to the hologram film 200. The compressed air device 108 comprises at least one channel 116, which is fluidically connected exclusively to the at least one gas passage arrangement 112 located in the exposure area 204. The gas passage arrangements 112 of the master frames 154 not located in the exposure area 204 are sealed off from the channel 116 of the compressed air device 108 and can only be fluidically connected to it when the respective master frame 154 is moved into the exposure area 204 by rotating the holding device 102, which is formed as a turret 114.The figures do not show in detail that, in order to generate the required negative pressure or vacuum, the compressed air device 108 comprises a pneumatic Venturi suction nozzle which is fluidically connected to the relevant gas passage arrangement 112 via one or more channels 116 and may be connected to valves in a suitable manner.

[0056] To keep the hologram film 200 as dust-free as possible before exposure and thus protect it from scratches, a cleaning device 148 is provided. This cleaning device 148 also serves to statically discharge the hologram film 200. The cleaning device 148 comprises a first spray nozzle 150 for ionized air, oriented in the film transport direction and arranged upstream of the turret 114. Optionally, a second spray nozzle for ionized air, oriented downstream of the turret 114 and oriented against the film transport direction, is also provided. In addition to its cleaning function, this ionized air can also be used to maintain or support the air cushion between the hologram film 200 and the holding device 102 during transport, thus giving the cleaning device 148 a dual function.On the upper side of the hologram film 200 facing away from the master 104, a third spray nozzle 130 of the cleaning device 148 also acts.

[0057] Based on Fig. Sections 2 to 4 below explain how a film section 202 is fixed to the master 104 of the exposure table 100 and then exposed.

[0058] First, the master 104 to be used for subsequent hologram exposure is selected on the revolver 114. The holding device 102, with its multiple master frames 154, is rotated until a master 104 desired for hologram exposure is located within the exposure area 204.

[0059] The film section 202 to be exposed is then transported to the master 104, which is held in the holding device 102 and located in the exposure area 204, by means of the film transport device 106, whereby the film lifting device 138, located film-upwards of the master 104 or the revolver 114, is in a raised position corresponding to the transport configuration, so that the hologram film 200 is held relative to the master 104 in such a way that the surface of the film section 202 to be exposed and the surface of the master 104 are oriented at an acute angle towards or away from each other.

[0060] Now, by means of the pressure roller 122 of the spreading device 120, the film section 202 is spread onto the master 104 starting from the acute angle onto the master 104, whereby additionally a suction air, i.e. a negative pressure, is present on or around the master 104 by means of the compressed air device 108.

[0061] In this case, the pressure roller 122 is removed from its right-hand position according to Fig. 2 into the in Fig. Proceed to the left position shown in step 3. Simultaneously or subsequently, the film lifting device 138 is also moved into the lowered position.

[0062] The pressure roller 122 is then moved from the left position according to Fig. 3 into the in Fig. The procedure shown in step 4 is carried out in the right position, whereby the film section 202 is applied a second time to the master 104 located in the exposure area 204, so that an exposure of the film section 202 can then take place.

[0063] Advantageously, and to avoid undesirable effects, such as Newton's rings, the suction air is then reduced or the vacuum is set to a lower level, wherein, in an advantageous embodiment, the film section 202 is mounted without pressure on the master 104. Subsequently, the film section 202 is exposed by illumination with the modulated light 400, whereby the volume reflection hologram is copied into the film section 202.

[0064] The hologram film 200 is then transported further by means of the film transport device 106 and a new film section 202 is positioned opposite the master 104, whereby the above procedure is carried out again.

[0065] A control device 326 is also provided for controlling the individual components of the exposure machine 300 ( Fig.1) The control device 326 is advantageously designed to control the light source 304 and / or the deflection and scanning device 310 and / or the light modulator 314 and / or the film transport device 106 and / or the compressed air device 108 and / or the stripping device 120 and / or the cleaning device 148 and / or the device for determining the rotational position of the turret. REFERENCE MARK LIST 100 exposure table 102 Holding device 104 Master 106 Film transport device 108 Compressed air device (suction device and / or blowing device) 110 film reels (unexposed holographic film) 112 Gas passage arrangement 114 revolvers 116 Channel (Compressed air / Suction air) 118 additional film reels (exposed holofilm) 120 scraping device 122 Pressure roller 124 sleds 126 Traverse axis (slide) 130 third spray nozzle 136 attacks 138 Film lift device 140 plate 142 Film roller 144 Guide roller 146 Lever arm 148 Cleaning equipment 150 first spray nozzle 154 Master recording 156 Rotary bearing 164 Master section 166 Counterweight 200 hologram films 202 Film section (film section to be exposed) 204 exposure range 300 hologram exposure machine 302 Exposure equipment 304 Light source (e.g. laser) 306 Beam guidance optics 308 mirrors 310 Deflection and scanning device 312 beam splitters 314 Light modulator 316 Silicon layer 318 Liquid crystal cell 320 protective screen 322 Beam shaping device (e.g. Powell or cylindrical lens) 324 Polarizing filters 326 Control unit 400 lights

Claims

[1] Exposure table (100) for a hologram exposure machine (300), with a holding device (102) in which a master receptacle (154) is formed or provided, which is designed to receive a master (104), and with a film guide designed to guide a hologram film (200) relative to the holding device (102) and to position a film section (202) to be exposed in an exposure area (204) relative to the master (104) for hologram exposure, characterized by , that the holding device (102) is formed as a revolver (114) with a plurality of radially oriented master mounts (154) which is rotatably mounted perpendicular to the optical axis of the hologram exposure. [2] Exposure table (100) according to claim 1, characterized by , that the revolver (114) comprises a plate (140) from which the master recordings (154) extend perpendicularly. [3] Exposure table (100) according to claim 1 or 2, characterized by , that the master recordings (154) are distributed around a master section (164) of the perimeter of the plate (140), and that a counterweight (166) is present on a section of the perimeter of the plate (140) that is complementary to the master section (164). [4] Exposure table (100) according to one of claims 1 to 3, characterized by , that a device for determining the turret rotation position is provided, which is formed by a number of detent seats corresponding to the number of master mounts (154) and by at least one detent element, and that the detent element is adjustable between a position disengaged from the detent seats, enabling the rotation of the turret (114) and a position engaged in one of the detent seats, preventing the rotation of the turret (114). [5] Exposure table (100) according to one of claims 1 to 4, characterized by, that the holding device (102) formed as a revolver is associated with a compressed air device (108) which is designed to fix the film section (202) at least temporarily by means of a negative pressure to the master (104) received in the holding device (102) and located in the exposure area (204). [6] Exposure table (100) according to claim 5, characterized by , that the compressed air device (108) is formed from a plurality of gas passage arrangements (112), that at least one of the gas passage arrangements (112) is assigned to each master receptacle (154) or the corresponding master (104) receptacled therein, and that the compressed air device (108) comprises at least one channel (116) which is fluidically connected exclusively to the at least one gas passage arrangement (112) located in the exposure area (204). [7] Exposure table (100) according to one of claims 1 to 6, characterized by, that a stripping device (120) is provided to strip the film section (202) to be exposed onto the master (104) located in the exposure area (204), and that the stripping device (120) comprises a carriage (124) which is movable between two stops (136) and on which a pressure roller (122) is mounted rotatably on a rotating axis and which interacts with the film section (202). [8] Exposure table (100) according to claim 7, characterized by , that the film guide includes a film lifting device (138) which is adjustable between a raised position corresponding to a transport configuration and a lowered position corresponding to an exposure configuration. [9] Method for introducing a volume reflection hologram into a film section (202) of a hologram film (200), in particular with an exposure table (100) according to any one of claims 1 to 8, comprising the steps: - Rotating a holding device (102) with a plurality of master images (154) until a master (104) desired for hologram exposure is located in an exposure area (204), - Transporting the film section to be exposed (202) into the exposure area (204) by means of a film transport device (106), - simultaneous or subsequent lifting of the hologram film (200) by means of a film lifting device (138) and forming an acute angle between the facing surfaces of film section (202) and master (104), - Applying the film section (202) to the master (104) starting from the acute angle using a pressure roller (122), and - Exposure of a hologram into the film section (202). [10] Method according to claim 9, characterized by, that a vacuum is provided on or around the master (104) before and / or during the application, whereby the film section (202) is sucked onto the master (104), and that the pressure roller (122) is rolled a second time over the film section (202) before the hologram film (200) is exposed.

Images