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

Description

[0001] The invention relates to an exposure table for a hologram exposure machine, comprising a holding device in which a master is accommodated, and a film transport device configured to transport a hologram film relative to the holding device and to position a film section to be exposed relative to the master for exposure. The invention further relates to a method for introducing a volume 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 have at least one feature that makes unauthorized duplication, imitation, and / or falsification of an object into which the security element is integrated difficult. Holograms are used as security elements in passports or identity cards, for example. However, they are also used in banknotes, driver's licenses, visas, other valuables, labels or tickets, credit cards, bank cards, telephone cards, and similar devices.

[0003] Volume holograms represent a special group of holograms. In a volume hologram, a diffractive 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 provided 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] In a contact copying process, the holographic exposure film is placed in front of a master in which diffractive structures are formed, which are to be "transferred" into the holographic exposure film. The diffractive structures of the master are thus copied into the holographic film during the contact copying process. For this purpose, coherent light is irradiated onto the master through the holographic film, which is placed in close proximity to the master or in contact with the master. The diffractive 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 structure is thus formed in the holographic film, which is determined by the light diffracted by the master.If the holographic film is developed and reconstructed, the reconstruction resembles that observed when the master is illuminated. A hologram, also known as a Denisyuk hologram, is stored in the holographic film. 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 structure occurs in the desired manner. A method for producing a master and a contact copying method are described in EP 0 896 260 A2.

[0005] The holographic features on the exposure film cannot be "stored" in the film material, or can only be stored incorrectly, if the hologram film is not completely flat, free of bubbles and creases, and especially if it is not positioned motionless or optically stable relative to the master during exposure. Bubbles or creases can cause unwanted reflections during film exposure.

[0006] ANONYMOUS: "Apparatus and method for replicating holograms in a recording film", RESEARCH DISCLOSURE, KENNETH MASON PUBLICATIONS, HAMPSHIRE, UK, GB, Vol. 404, No. 2, December 1, 1997 (1997-12-01), XP007122187, ISSN: 0374-4353, describes an apparatus and method for reproducing holograms in a recording film. The apparatus removes the cover foil of a recording film before the holographic exposure step.

[0007] KR 102 001 019 B1 describes a hologram transmission device that can selectively generate a transmission hologram and a reflection hologram in a single device and easily adjust the reconstruction angle.

[0008] JP H11 249535 A describes a hologram master holding device for copying a reflection or transmission hologram by tightly attaching a light-sensitive material to the hologram master.

[0009] JP 4 318996 B2 describes a method for manufacturing a light diffraction structure containing a diffraction structure such as a diffraction grating or a hologram. Numerous tiny holes are provided on a surface of the drum, and the air inside the drum is sucked in by a suction pump, creating a negative pressure inside the drum. The hologram foil and hologram plate resting on the drum are sucked onto the outer surface of the drum.

[0010] DE 10 2013 200 980 A1 describes a device for the subsequent holographic marking of a composite body and a corresponding method. This device includes a support plate onto which the composite body, namely the future identification, valuables, or security document, can be placed. The support plate includes suction openings for securing the composite body using negative pressure. Additional suction holes are also provided for securing the hologram master, provided as a film, using negative pressure.

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

[0012] This object is achieved by an exposure table having the features of claim 1 and by a method having the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0013] The exposure table for a hologram exposure machine comprises a compressed air device associated with the holding device, which is designed to at least temporarily fix the film section to the master held in the holding device using a vacuum. Such a vacuum ensures that the film section is fixed flat and, in particular, free of air bubbles relative to the master, thereby significantly reducing the reject rate of exposed holograms. In addition, the film section is positioned completely flat, bubble-free, and wrinkle-free relative to the master, allowing volume reflection holograms to be reliably copied into the hologram film.

[0014] The master of a hologram exposure machine is typically formed from a material that may have sharp edges around its periphery. These edges can cause scratches on the hologram film as it is transported over the master and the holding device. To counteract this problem, the compressed air device is preferably designed to at least temporarily provide an overpressure such that the transport of the hologram film relative to the master is supported by an air cushion. In In other words, the compressed air device is designed to provide blowing air which applies compressed air to the hologram film on its side facing the master, so that damage to the film is effectively avoided.

[0015] For secure fixing of the film section to the master during exposure of the hologram film, it has proven advantageous if the compressed air device comprises at least one gas passage arrangement which is arranged at the edge with respect to the master received in the holding device and / or which is formed in the master itself.

[0016] A reliable attachment of the film section to 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).

[0017] Since a vacuum can often be created more easily with compressed air than with a vacuum pump, it has proven advantageous if the compressed air device includes a pneumatic Venturi suction nozzle to generate the negative pressure. With the vacuum ejector thus formed, compressed air can be easily introduced into the ejector, which is accelerated at a drive nozzle (Venturi nozzle) with a cross-sectional constriction. The dynamic pressure increases and the static pressure of the air decreases. After passing through the drive nozzle, the accelerated air expands and a vacuum is created, with additional air being sucked into the ejector through the vacuum connection, which is fluidically connected to the gas passage arrangement, and which exits the ejector through the silencer together with the sucked-in air. This creates a simple variant of the compressed air device, which can be used optionally - if necessary.Depending on the appropriate position of the valves, a negative pressure or positive pressure can be provided on the circumference of the master.

[0018] In order to ensure that even the last remaining air bubbles between the film section of the hologram film to be exposed and the master are removed, it has proven advantageous to have a spreading device to spread the film section to be exposed onto the master.

[0019] This advantageously allows the application device to comprise a carriage that can be moved between two stops and on which a pressure roller is mounted that is rotatably mounted on a rotational 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. This also advantageously allows the application device to be rolled over the film section alternately, i.e., starting in one direction upstream of the master and starting downstream of the master.

[0020] To ensure the smoothest possible transport of the hologram film, it is advantageous if the carriage is mounted so that it can pivot to a limited extent about a travel axis oriented perpendicular to the rotational axis of the pressure roller, thus allowing the pressure roller to be adjusted between a raised position and a lowered position. In this context, it is possible to provide a control cam, particularly near or at the respective stop, which is designed to adjust the pressure roller between the raised and lowered positions.

[0021] To adjust or vary the force exerted by the pressure roller on the film section, it is useful to have a spring arrangement on the carriage on the side facing away from the master, which adjusts 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 travel axis.

[0022] In order to be able to compensate for tolerance fluctuations, 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 carriage 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 to a limited extent in relation to the carriage.

[0023] To ensure that the hologram film does not touch the holding device or the master held in the holding device during transport, the invention provides that the film transport device comprises a first film lifting device that can be adjusted between a raised position corresponding to a transport configuration and a lowered position corresponding to an exposure configuration. This configuration also opens up the possibility of holding the hologram film relative to the master, before or during its fixing, 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 toward or away from each other. Such a "ramp" orSuch a fictitious "wedge" allows air bubbles to be expelled sufficiently effectively during the subsequent fixation by means of suction air, or any other gas inclusions can be avoided, as these are pushed away by the acute angle, particularly in cases where a stripping device is also used to fix the film section to the master. In order to be able to provide such a "wedge" both in and against the film transport direction, the invention also provides for the transport device to include a second film lifting device that can be adjusted between a raised position corresponding to a transport configuration and a lowered position corresponding to an exposure configuration.

[0024] To ensure the transport of the hologram film is as smooth as possible, it is advantageous if the first film lifting device and / or the second film lifting device comprise a film lifting roller that can rotate about an axis. The film lifting roller can be used to raise or lower the hologram film.

[0025] For improved guidance, in particular for improved holding of the hologram film, it is advantageous if the first film lifting device and / or the second film lifting device comprises a guide roller arranged axially parallel to the film lifting roller, each of which is rotatably mounted on a lever arm which can be pivoted to a limited extent about the axis.

[0026] During exposure of the hologram film, it is necessary and desirable that the hologram film be dust-free. For this reason, 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, especially during transport. This also serves to discharge the film's static.

[0027] This ionized air can also be used to provide an air cushion during transport, for which purpose the cleaning device comprises in particular 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, opposite to the film transport direction.

[0028] For a compact, symmetrical construction of the exposure table, it is advantageous if the first spray nozzle is arranged film-upwards with respect to the holding device, and if the second spray nozzle is arranged film-downwards with respect to the holding device.

[0029] The advantages and advantageous configurations mentioned for the exposure table and the exposure machine apply equally to the method according to the invention. This method comprises, in particular, the following steps: Transporting the film section to be exposed to a master held in a holding device by means of a film transport device, fixing the film section to be exposed by applying a negative pressure to or around the master by means of a compressed air device, and exposing at least part of the film section by means of an exposure device.

[0030] By fixing the film section to or around the master with a negative pressure, it is ensured that the hologram film is positioned bubble-free on the master during exposure, so that volume reflection holograms are produced reliably and, in particular, with little waste.

[0031] In order to protect the hologram film from damage during transport by means of the film transport device, for example from edges of the master or the holding device for the master, it has proven advantageous if the compressed air device provides an overpressure during transport of the hologram film in such a way that the hologram film slides on an air cushion during transport.

[0032] If too much negative pressure is applied to the film section by the printing device, it can lead to movements of its own, for example in the form of Newton's rings, so that it has proven useful to apply a negative pressure to the film section during exposure that is reduced compared to the negative pressure when fixing the film section, or to hold the film section without pressure on the master during exposure.

[0033] According to the invention, the hologram film is held relative to the master to fix the film section 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 toward or away from each other. Starting from the acute angle, the film section is applied to the master using a spreading device. By forming a kind of "wedge" between the hologram film and the master, any air or gas inclusions present between them can be even more easily removed with the spreading device, so that the number of gas inclusions between the master and the film section is reduced to a minimum, preferably zero.

[0034] To reduce the cycle time for producing multiple volume holograms, the invention provides for the acute angle between the film section and the master to be arranged alternately on the downstream side of the master and on the upstream side of the master. In addition, the spreading device is actuated accordingly to spread the film section to be exposed onto the master, also alternately starting from the downstream side of the master and starting from the upstream side of the master. Applying negative pressure on or around the master at the same time as the film section is spread onto the master contributes to the additional elimination of bubbles or the prevention of crackling in the hologram film.

[0035] To provide the "wedges", film lifting devices are advantageously used.

[0036] The present invention is explained in more detail below with reference to figures, wherein the examples shown are merely exemplary and do not represent a limitation with regard to the scope of the described invention. They show in detail: Figure 1 is a schematic representation of an exposure machine for exposing a volume reflection hologram in a hologram film, Figure 2 is a plan view of an exposure table, Figure 3 is a perspective view along the line V - V of Figure 2 sectional view of the exposure table, Figure 4 the section along the line IV - IV from Figure 2 , Figure 5a a side view along the line V - V from Figure 2 with the pressure roller at the first stop before applying the hologram film to the master, Figure 5b, a side view along the line V - V from Figure 2with the pressure roller at the second stop and the film lifting devices in the exposure configuration, and Figure 5c a side view along the line V - V from Figure 2 with the pressure roller at the second stop before the hologram film is again applied to the master.

[0037] In Figure 1 A hologram exposure machine 300 for exposing holograms in a hologram film 200 is shown schematically. Such a hologram exposure machine 300 is also referred to as a holo-exposure unit.

[0038] The hologram exposure machine 300 comprises an exposure device 302 shown at the top of the drawing and an exposure table 100 shown at the bottom of the drawing.

[0039] Holograms are exposed using coherent light. For this purpose, the exposure device 302 has a light source 304, which in this case is embodied as a cw laser. In this case, "cw" stands for "continuous wave" and means "a wave emitted at a constant time." It is possible for the light source 304 to be a pulsed laser. The light 400 of the light source 304, embodied as a laser, has a first polarization state. Beam guiding optics 306 are used to guide the light 400. In the illustrated exposure device 302, the light from the light source 304 is first guided to a deflection and scanning device 310 of the beam guiding optics 306, if necessary with the aid of a beam shaping device 322 for beam expansion oriented in particular in a spatial direction.This deflection and scanning device 310 comprises a galvanometer scanner and a mirror 308 coupled to the galvanometer scanner, at 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 by a dashed line. By moving the mirror 308, an exposure of the hologram corresponding to a "scan," in particular a line scan, can occur. In other words, the hologram film 200 is "scanned" to expose the hologram. Other types of deflection and scanning devices 310 for the light 400 can also be used.

[0040] The deflected light 400 is guided to a polarization-dependent beam splitter cube 312 of the beam guiding optics 306. This cube is formed from a first prism and a second prism, at whose interface a polarization-dependent beam splitting occurs. Instead of prisms, a beam splitter plate can also be used. 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.

[0041] 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, at which incident light 400 is reflected. In the present case, electronic switching elements are formed on this silicon layer 316. These switching elements are used to switch liquid crystal cells 318, which are arranged in front of the surface of the silicon layer 316 used for reflection. The individual liquid crystal cells 318 can be individually set to different switching states. Typically, an array of liquid crystal cells 318 is present, so that further rows of liquid crystal cells 318 are present, offset from or into the plane of the paper.Depending on the respective switching state of the liquid crystal cells 318, a polarization state of the passing light 400 is changed or not changed, whereby the light 400 is spatially modulated. For simplification, it is assumed here that in a first switching state, the light 400 incident on the light modulator 314 in a first polarization state is changed overall in terms of polarization upon passing through a liquid crystal cell 318, which is passed through twice due to reflection at the surface of the silicon layer 316, such that the light 400 is subsequently polarized in the further polarization state orthogonal to the first polarization state. This polarization-modulated light 400 passes through a transparent protective screen 320 of the spatial light modulator 314, wherein in particular an exit surface of the protective screen 320 is oriented parallel to the reflection surface of the silicon layer 316.The surface normal of the light modulator 314 is thus orthogonal to both the exit surface of the protective disk 320 and the reflective surface of the silicon layer 316.

[0042] After exiting the light modulator 314, the modulated light again strikes the polarization-dependent beam splitter 312, whereby the modulated light 400 reflected back by the LCoS can or cannot pass the interface of the beam splitter 312 depending on its polarization state. If the modulated light 400 has been converted into the further polarization state orthogonal to the first polarization state due to the first switching state of the liquid crystal cell, as in the exemplary case, it can pass the interface of the polarization-dependent beam splitter cube 312, whereupon it is guided further toward the exposure table 100, possibly with the aid of a polarization filter 324.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 boundary surface and therefore do not reach 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.

[0043] 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 of these rotations result in the light having a changed amplitude and thus a changed intensity of the other polarization state. These vary depending on the angle of rotation and increase with the amount of rotation between 0 degrees and 90 degrees. This makes it possible to expose "grayscale."

[0044] The exposure table 100 has a holding device 102 in which a master 104 is accommodated. The master 104 comprises a carrier, which is typically made of glass or another material. Other carrier materials are also possible, for example, metals. Preferably, at least one optically active layer, for example a diffraction layer, is applied to the carrier, which comprises a diffraction structure to be copied. In the present case, the diffraction layer of the master 104 comprises a volume reflection hologram to be copied.

[0045] It can be seen that the exposure machine 300, in particular the exposure table 100, comprises a film transport device 106, which is designed to transport the hologram film 200 relative to the holding device 102 and thus relative to the master 104. The film transport device 106 is provided for receiving the holographic film and holding and / or guiding the film during the exposure of the hologram. In the exposure machine 300 shown, the film transport device 106 comprises a film roll 110 on which the hologram film 200 is provided. After exposure, the film is wound onto another film roll 118. If necessary, the exposed hologram film 200 passes through a hologram development section, through which thermal action is exerted on the hologram film 200 in order to develop the hologram in the film before the exposed hologram film 200 is rewound onto the another film roll 118.In any case, the hologram film 200 is typically guided by film guide rollers. It can be seen that the hologram film 200 extends beyond the area of ​​the master 104, meaning that the film transport device 106 is configured to position a film section 202 to be exposed relative to the master 104. The volume reflection hologram is exposed, i.e., copied, into this film section 202. To achieve reliable exposure of the hologram, the hologram film 200 rests against the master 104 during the exposure process. This system allows the inherent movements of the holographic film to be suppressed, which increases the achievable diffraction efficiency of the produced hologram.

[0046] During exposure, the modulated light 400, which has the further polarization state, passes through the film section 202 of the hologram film 200 to be exposed and is redirected by the optically active structure of the at least one optically active layer of the master 104, e.g., diffracted by 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. As a result, the optically active structure, e.g., the diffractive structure, of the master 104 is exposed into the hologram film 200. Depending on the spatial modulation, the optically active structure is either exposed and copied pixel by pixel or, on the other hand, not exposed and therefore not copied. This creates a copy of the optically active structure, e.g., a copy of a volume reflection hologram of a ground glass screen.

[0047] The present invention relates to the design and operation of the exposure table 100 used in Figure 2 can be seen in more detail in a top view. The holding device 102 shown here is designed in the manner of a turntable and has two receptacles for a master 104. A different number of master receptacles is possible, so that three or more masters 104 can be arranged on one and the same holding device 102. In order to protect the very sensitive edges of the master 104, the receptacle of the holding device 102 is designed such that the master 104 is arranged countersunk relative to the holding device 102, but preferably lies in a common plane with the latter.

[0048] The film transport device 106 comprises a first film lifting device 138 located upstream of the master 104 and a second film lifting device 140 located downstream of the master 104, each of which comprises a film lifting roller 142 and a guide roller 144. The film lifting roller 142 is arranged axially parallel to the guide roller 144, with the guide roller 144 itself being rotatably mounted on a lever arm 146 that can be pivoted to a limited extent about the axis of the film lifting roller 142. For this purpose, the respective film lifting devices 138, 140 have corresponding arcuate elongated holes ( Fig. 5a to 5c). The adjustment of the lever arm 146 can be actuated by pressure medium, in particular pneumatically. The raising and lowering of the film lifting devices 138, 140 is also actuated by pressure medium, in particular pneumatically. The film lifting devices 138, 140 of the film transport device 106 ensure a minimal 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, whereby the exposure table 100 and thus the exposure machine 300 formed therewith are designed to be very space-saving and compact.

[0049] Evidentially Figure 3In the present case, the holding device 102 is assigned a compressed air device 108, which is designed to at least temporarily fix the film section 202 to the master 104 received in the holding device 102 by means of a negative pressure for the exposure of the film section 202. For this purpose, a slot is provided circumferentially around the master 104, which thus forms a gas passage arrangement 112. The gas passage arrangement 112 thus frames the master 104 circumferentially and thus ensures that the film section 202 to be exposed rests against the master 104 without any bubbles. In the present case, however, the compressed air device 108 can additionally be used to temporarily provide an overpressure such that the transport of the hologram film 200 relative to the master 104 is supported by an air cushion, which additionally prevents damage to the hologram film 200. InThe figures show that, in order to generate the required negative pressure or vacuum, the compressed air device 108 in the present case comprises a pneumatic Venturi suction nozzle 114 which is fluidically connected to the gas passage arrangement 112 via one or more channels 116 and is suitably connected to valves.

[0050] In order to additionally press out gas inclusions between the hologram film 200 and the master 104, a spreading device 120 is also provided in the present case for spreading the film section 202 to be exposed onto the master 104. This spreading device 120 is formed in the present case by a carriage 124 that can be displaced between two stops 136 and on which a pressure roller 122 is mounted that is rotatably mounted on a rotational axis and interacts with the film section 202 during the spreading process. The carriage 124 itself is mounted in the present case so that it can be pivoted to a limited extent about a travel axis 126 oriented perpendicular to the rotational axis of the pressure roller 122, whereby the pressure roller 122 itself can be adjusted between a raised position and a lowered position.At each of the stops 136 or close to the stop there is a control cam 128 which is designed to adjust the pressure roller 122 between the raised position and the lowered position when the carriage 124 interacts with the control cams 128.

[0051] Evidentially Figure 4It can be seen that the carriage 124, on its side facing away from the master 104, is assigned a spring arrangement 130, which adjusts 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. This spring arrangement 130 exerts a spring force on the carriage 124, which can be pivoted about the travel axis 126, so that the contact pressure of the pressure roller 122 is maximum in the area between the two stops 136. However, the stops 136 and / or the control cams 128 deactivate the spring arrangement 130 at least partially, preferably completely, so that the pressure roller 122 can be lifted off the hologram film 200 when the carriage 124 is in its end positions. In this case, the slide 124 is also actuated by pressure medium, in particular pneumatically, between the two stops 136. Hydraulic or motorized adjustment is also possible.

[0052] It can also be seen that the carriage 124 is assigned a holding arm 132, on which the pressure roller 122 is rotatably mounted. This holding arm 132 has a pivot axis 134 oriented perpendicular to the axis of rotation of the pressure roller 122, so that the holding arm 132 is fixed to the carriage 124 in such a way that the holding arm 132 and thus the pressure roller 122 are mounted to a limited extent pivotable relative to the carriage 124 in order to be able to execute a compensating movement caused by tolerance fluctuations or by any unevenness.

[0053] In order 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. The cleaning device 148 comprises a first spray nozzle 150 for ionized air, oriented in the film transport direction and arranged upstream of the master 104, and a second spray nozzle 152 for ionized air, oriented counter to the film transport direction and arranged downstream of the master 104. In addition to the cleaning function, this ionized air can be used to maintain or support the air cushion between the hologram film 200 and the holding device 102 during transport, so that the cleaning device 148 performs a dual function.

[0054] Based on the Figures 5a to 5c It will be explained below how a plurality of film sections 202 are fixed and exposed on the master 104 of the exposure table 100.

[0055] First, the film section 202 to be exposed is transported to the master 104 held in the holding device 102 by means of the film transport device 106, with the second film lifting device 140 located downstream of the master 104 in a raised position corresponding to the transport configuration. Simultaneously or subsequently, the first film lifting device 138 of the film transport device 106 is adjusted to a lowered position corresponding to an exposure configuration, so that the hologram film 200 is held relative to the master 104 such that the surface of the film section 202 to be exposed and the surface of the master 104 are oriented at an acute angle toward or away from each other.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, wherein additionally a suction air, i.e. a negative pressure on or around the master 104 is present by means of the compressed air device 108.

[0056] In Figure 5a The pressure roller 122 is moved from its left position to the Figure 5bshown right position. At the same time or subsequently, the second film lifting device 140 is also moved into the lowered position, so that exposure of the film section 202 can then take place. Advantageously, and to avoid undesirable effects, for example due to Newton's rings, the suction air is then reduced or the negative pressure is set to a lower level, wherein, in an advantageous embodiment, the film section 202 is mounted pressurelessly on the master 104. Subsequently, the film section 202 is exposed by illuminating it with the modulated light 400, whereby the volume reflection hologram is copied into the film section 202.

[0057] The hologram film 200 is then transported further by means of the film transport device 106 and a new film section is positioned opposite the master 104. In this case, Figure 5cThe first film lifting device 138 is now moved into its raised position, while the second film lifting device 140 remains in the lowered position. The acute angle formed by the surface of the film section 202 to be exposed and the surface of the master 104 is now positioned film-down from the master 104, so that the pressure roller 122 can now strip the new film section 202 onto the master 104 from right to left in the drawing, with a negative pressure advantageously being provided on or around the master 104 by the compressed air device 108.Thus, it has proven useful and advantageous that, for exposing multiple film sections 202 of the hologram film 200, the acute angle is arranged alternately on the downstream side of the master 104 and on the upstream side of the master 104, and that the spreading device 120, with its pressure roller 122, spreads the film section 202 to be exposed correspondingly, also alternately starting from the downstream side of the master 104 and starting from the upstream side of the master 104. This also reduces the cycle time when producing a plurality of film sections 202 to be exposed.

[0058] For controlling the individual components of the exposure machine 300, a control device 326 is also provided ( 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 spreading device 120 and / or the cleaning device 148. LIST OF REFERENCE SYMBOLS

[0059] 100Exposure table 102Holding device 104Master 106Film transport device 108Compressed air device (suction device and / or blowing device) 110Film roll (unexposed holographic film) 112Gas passage arrangement 114Venturi suction nozzle 116Channel (compressed air / suction air) 118Additional film roll (exposed holographic film) 120Swiping device 122Pressure roller 124Slide 126Travel axis (slide) 128Control cam 130Spring arrangement 132Holding arm 134Pivot axis 136Stop 138First film lifting device 140Second film lifting device 142Film lifting roller 144Guide roller 146Lever arm 148Cleaning device 150First spray nozzle 152Second spray nozzle 200Hologram film 202Film section (film section to be exposed) 300Hologram exposure machine 302Exposure device 304Light source (e.g. laser) 306Beam guiding optics 308Mirror 310Deflection and scanning device 312Beam splitter 314Light modulator 316Silicon layer 318Liquid crystal cell 320Protective screen 322Beam shaping device (e.g.Powell or cylindrical lens) 324Polarizing filter 326Control device.

Claims

1. An exposure table (100) for a hologram exposure machine (300), with a holding device (102) in which a master (104) is accommodated, and with a film transport device (106) which is designed to transport a hologram film (200) relative to the holding device (102) and position a film section (202) to be exposed relative to the master (104) for hologram exposure, whereby a compressed air device (108) is assigned to the holding device (102) which is designed to fix the film section (202) at least temporarily to the master (104) accommodated in the holding device (102) by means of a negative pressure, characterized in that in that the film transport device (106) comprises a first film lifting device (138) which is arranged on the upstream side of the master (104) and which is adjustable between a raised position corresponding to a transport configuration and a lowered position corresponding to an exposure configuration, and in that the film transport device (106) comprises a second film lifting device (140) which is arranged on the side of the master (104) downstream of the film and which is adjustable between a raised position corresponding to a transport configuration and a lowered position corresponding to an exposure configuration.

2. The exposure table (100) according to claim 1, characterized in that the compressed air device (108) is designed to provide an overpressure at least temporarily in such a way that the transport of the hologram film (200) relative to the master (104) is supported by an air cushion.

3. The exposure table (100) according to claim 1 or 2, characterized in that the compressed air device (108) comprises at least one gas passage arrangement (112) which is arranged at the edge with respect to the master (104) received in the holding device (102) and / or which is formed in the master (104) itself, in that the gas passage arrangement (112) frames the master (104) on the circumferential side, and in that the gas passage arrangement (112) is formed by a slot or by a bore arrangement comprising a plurality of bores.

4. The exposure table (100) according to any one of claims 1 to 3, characterized in that a roller device (120) is provided in order to roll the film section (202) to be exposed onto the master (104), and in that the roller device (120) comprises a carriage (124) which can be displaced between two stops (136) and on which a pressure roller (122), which is rotatably mounted on an axis of rotation and interacts with the film section (202), is mounted.

5. The exposure table (100) according to claim 4, characterized in that in that the carriage (124) is mounted so as to be pivotable to a limited extent about a traversing axis (126) oriented perpendicularly with respect to the axis of rotation of the pressure roller (122), and the pressure roller (122) can thus be adjusted between a raised position and a lowered position, and in that a control cam (128) is provided in each case, which is designed to adjust the pressure roller (122) between the raised position and the lowered position.

6. The exposure table (100) according to claim 4 or 5, characterized in that a spring arrangement (130) is assigned to the carriage (124) on its side facing away from the master (104), which adjusts or predetermines the contact pressure of the contact pressure roller (122) on the master (104) or on the film section (202) located on the master (104).

7. The exposure table (100) according to any one of claims 4 to 6, characterized in that the pressure roller (122) is rotatably mounted on a holding arm (132) , which is fixed to the carriage (124) by means of a pivot axis (134) oriented perpendicular to the axis of rotation in such a way that the holding arm (132) and thus the pressure roller (122) are mounted so as to be pivotable to a limited extent with respect to the carriage (124).

8. The exposure table (100) according to any one of claims 1 to 7, characterized in that the first film lifting device (138) and / or the second film lifting device (140) comprises a film lifting roller (142) rotatable about an axis.

9. The exposure table (100) according to claim 8, characterized in that the first film lifting device (138) and / or the second film lifting device (140) comprises a guide roller (144) which is arranged axially parallel to the film lifting roller (142) and is mounted rotatably on a lever arm (146) which can pivot about the axis to a limited extent.

10. A method of introducing a volume hologram into a film section (202) of a hologram film (200), comprising the steps of: - transporting the film section (202) to be exposed to a master (104) accommodated in a holding device (102) by means of a film transport device (106), - fixing the film section (202) to be exposed by applying a negative pressure to or around the master (104) by means of a compressed air device (108), and - exposing at least a part of the film section by means of an exposure device (302), wherein the hologram film (200) is held relative to the master (104) for fixing the film section (202) 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, and wherein the film section (202) is rolled onto the master (104) starting from the acute angle by means of a roller device (120), and wherein, for exposing a plurality of film sections (202) of the hologram film (200), the acute angle is arranged alternately on the downstream side of the master (104) and on the upstream side of the master (104), and in that the roller device (120) rolls the film section (202) to be exposed in a corresponding manner, likewise alternately starting from the downstream side of the master (104) and starting from the upstream side of the master (104).

11. The method according to claim 10, characterized in that the compressed air device (108) provides an overpressure during the transport of the hologram film (200) such that the hologram film (200) slides on an air cushion.