Hologram recording device and hologram production method

Abstract

[Problem] To provide a method by which holograms having different characteristics can be multiplex-recorded in one region with high diffraction efficiency. [Solution] Combinations of N sets of reference light and object light which interfere with the same set of reference light and object light but do not interfere with other sets of reference light and object light are simultaneously caused to interfere in one region of a holographic recording material, and N holograms are multiplex-recorded in the one region of the holographic recording material.

Description

Hologram recording device and hologram manufacturing method 【0001】 The present invention relates to a hologram recording apparatus and a hologram manufacturing method for recording interference fringes formed by interfering object light and reference light on a holographic recording medium, and more particularly to a hologram recording apparatus and a hologram manufacturing method for multiplexing holograms with different characteristics in a single area. 【0002】 A hologram is created by interfering coherent object light with a reference light, and recording interference fringes onto a holographic recording medium. The object light can be reconstructed by irradiating the hologram with the same reference light (reconstruction reference light) at the same angle of incidence as during recording. A hologram with a wide spacing between interference fringes relative to the thickness of the holographic recording medium is called a thin hologram or planar hologram, while one with a narrow spacing is called a thick hologram or volumetric hologram. In a thick hologram, the interference fringes are recorded three-dimensionally within the recording medium, and the diffraction becomes stronger when Bragg's condition is met. Bragg's condition is 2dsinθ = nλ (where d is the spacing between interference fringes, θ is the angle between the medium surface and the incident light (90° - angle of incidence), λ is the wavelength of the incident light, and n is a natural number). If the reconstruction reference light is exactly the same as the reference light used during recording, Bragg's condition is met and diffraction occurs. However, for example, reconstruction gradually ceases as the angle of incidence shifts (angle selectivity), and reconstruction gradually ceases as the wavelength shifts (wavelength selectivity). These selectivity limitations become more stringent as the holographic recording medium becomes thicker. 【0003】 Holograms can reproduce light with the same wavefront as object light, making them suitable for a variety of applications. For example, by recording light from a three-dimensional object as object light, a three-dimensional image can be reproduced. Furthermore, by changing the propagation directions of the reference light and object light, a hologram can be used as a deflection element to change the direction of light propagation. Additionally, a transmissive hologram can be formed by interfering object light and reference light by irradiating them from the same side of the hologram, while a reflective hologram can be formed by interfering them by irradiating them from the opposite side. Moreover, by recording object light focused or diffused by a lens, it is possible to imbue the hologram with the function of a lens. 【0004】Patent Document 1 discloses a light-gathering mechanism usable for solar power generation and the like, comprising an angle-selective reflective means and an angle-increasing reflective hologram arranged with a gap between them, in which light from a light source is received on the surface (light-receiving surface) of the angle-selective reflective means, at least a portion of the light transmitted through the light-receiving surface of the angle-selective reflective means is confined in the gap, and the light is propagated through the gap toward a specific edge, thereby concentrating the light at the edge. In such a light-gathering mechanism, at least a portion of the light incident into the gap via the angle-selective reflective means is deflected toward a specific edge by the angle-increasing reflective hologram, and the emission angle is amplified and reflected at an angle that confines the light within the gap, thereby concentrating the light through total internal reflection within the gap. 【0005】 International Publication No. 2014 / 112620 【0006】As shown in Figures 12(a) and (b), the sun 120 moves in an orbit that rises in the east (E), passes through the south (S), and sets in the west (W) every day. Therefore, the direction in which sunlight enters the centrally located light-gathering mechanism 110 changes sequentially from west (W), south (S), and east (E) throughout the day. Furthermore, throughout the year, the sun's height (elevation angle) also changes from the orbit 122 at the summer solstice to the orbit 123 at the winter solstice, centered on the orbit 121 at the vernal and autumnal equinoxes. Therefore, when focusing incident light by propagating it toward a specific edge, as in the light-gathering mechanism of Patent Document 1, it is necessary to diffract all light incident from various directions toward a specific edge with high diffraction efficiency at all times. In this regard, Patent Document 1 discloses that it is also possible to multiplex record holograms with different properties at the same position, for example, multiplex recording of multiple holograms with different angular ranges of angular selectivity at the same position. In principle, by changing the direction of the reference light while keeping the direction of the object light constant, and performing multiplex recording at the same position, it is possible to diffract light from various reference light directions and at the same incident angle, thereby regenerating the regenerated light in the same constant direction as the object light. However, there is a problem in that the diffraction efficiency of each individual decreases as the number of multiplex recordings is repeated, due to the limited dynamic range (M / #: M number) of the recording material. M / # is one of the multiplex recording performance indicators, and is an index for estimating the maximum number of multiplexes m possible with a given recording medium. If the diffraction efficiency η is fixed and the maximum number of planar diffraction gratings that can perform multiplex recording is m, then it can be calculated using the following formula. 【0007】 【0008】 The present invention has been made in view of the aforementioned problems, and aims to provide a hologram recording apparatus and a hologram manufacturing method that can multiple-record holograms with different characteristics in a single area with high diffraction efficiency. 【0009】To solve the above problems, the hologram recording apparatus of the present invention includes a Q-switched laser, a beam splitter that splits the laser light emitted from the Q-switched laser into N divided laser beams, an optical system that irradiates the N divided laser beams toward one region of a holographic recording material, and an object light regeneration hologram that is positioned close to at least the front or back side of the one region of the holographic recording material and regenerates N object beams toward the holographic recording material by interfering with the N divided laser beams, wherein the optical distances of the N divided laser beams from the Q-switched laser to the one region of the holographic recording material differ by at least the coherence length of the Q-switched laser, and N holograms are multiplexed and recorded in the one region of the holographic recording material by the N divided laser beams and the N object beams. 【0010】 Furthermore, in the hologram recording apparatus described above, it is preferable that the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the Q-switched laser. 【0011】 Furthermore, in the hologram recording device described above, the directions of propagation of the N object light beams may all be the same. 【0012】 Furthermore, in the hologram recording apparatus described above, the optical system may irradiate the one region of the holographic recording material with the N divided laser beams as parallel light. 【0013】 Furthermore, in the hologram recording apparatus described above, the beam splitter may split the laser light emitted from the Q-switched laser in a plane perpendicular to the optical axis such that the optical axes of N split laser beams are arranged in two dimensions. 【0014】 Furthermore, in the hologram recording apparatus described above, the beam splitter may be divided such that, in a plane perpendicular to the optical axis, the optical axes of the N divided laser beams are arranged in an m x k ​​matrix, at the vertices of concentric polygons of different sizes, or at least on the circumferences of concentric circles of different diameters. 【0015】Furthermore, the hologram recording device preferably includes N optical fibers corresponding to each of the N divided laser beams, and the lengths of the N optical fibers are preferably different by at least the coherence length of the Q-switched laser. 【0016】 Furthermore, the present invention provides a method for manufacturing a hologram, comprising: emitting laser light from a Q-switched laser; dividing the laser light emitted from the Q-switched laser into N divided laser beams; irradiating one region of a holographic recording material with the N divided laser beams; reproducing N object beams toward the holographic recording material from an object beam reproduction hologram positioned close to at least the front or back surface of the one region of the holographic recording material; and multiplexing N holograms in the one region of the holographic recording material using the N divided laser beams and the N object beams, wherein the optical distances of the N divided laser beams from the Q-switched laser to the one region of the holographic recording material differ by at least the coherence length of the Q-switched laser. 【0017】 Furthermore, in the above-described method for manufacturing a hologram, the optical axes of the N divided laser beams may be divided such that the laser beams emitted from the Q-switched laser are arranged in two dimensions on a plane perpendicular to the optical axis. 【0018】 Furthermore, in the above-described method for manufacturing a hologram, the optical axes of the N divided laser beams may be divided in a plane perpendicular to the optical axes in an m x k ​​matrix, such that they are arranged at least on the vertices of concentric polygons of different sizes, or at least on the circumferences of concentric circles of different diameters. 【0019】Furthermore, another hologram recording apparatus of the present invention includes N lasers that generate laser light that is non-coherent to each other, a beam splitter that splits the N laser beams emitted from the N lasers into object light and reference light, an optical system for reference light that directs the N reference light beams toward a region of the holographic recording material so that they each have different incident angles toward the holographic recording material, an optical system for object light that directs the N object light beams toward the region of the holographic recording material, and a controller that controls the N reference light beams and the N object light beams to simultaneously direct the region of the holographic recording material, thereby multiplexing N holograms in the region of the holographic recording material. 【0020】 Furthermore, in the hologram recording apparatus described above, the optical system for object light may irradiate the N object light beams toward the one region of the holographic recording material at the same angle of incidence. 【0021】 Furthermore, in the hologram recording apparatus described above, the optical system for object light includes tapered optical fibers into which at least a portion of the N object light beams are incident, and the tapered optical fibers may have a shape in which the input diameter is physically larger than the output diameter, and the diameter gradually decreases from the input to the output. 【0022】 Furthermore, in the hologram recording apparatus described above, the optical system for the reference light may include N optical fibers that transmit each of the N reference light beams. 【0023】 Another method for manufacturing a hologram according to the present invention is a method for manufacturing a hologram on a holographic recording material, wherein N laser beams are emitted from N lasers that generate non-coherent laser beams from each other, the N laser beams are each divided into object beams and reference beams, the N reference beams are directed towards a region of the holographic recording material so that they have different angles of incidence to the holographic recording material, and the N object beams are directed towards the same region of the holographic recording material, thereby multiplexing N holograms on the same region of the holographic recording material. 【0024】 Furthermore, another hologram recording apparatus of the present invention includes N lasers that generate laser light that is non-coherent to each other, an object light reproduction hologram positioned in close proximity to the front or back surface of at least one region of a holographic recording material, and a controller that controls the N lasers, wherein the N lasers are arranged so that N laser beams emitted from the N lasers are directed toward the one region of the holographic recording material, the object light reproduction hologram interferes with the N laser beams to reproduce N object beams directed toward the holographic recording material, and the controller controls the N lasers so that the N laser beams are directed toward the one region of the holographic recording material simultaneously. 【0025】 Furthermore, in the hologram recording apparatus described above, it is preferable that the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the N lasers. 【0026】 Furthermore, in the hologram recording device described above, the directions of propagation of the N object light beams may all be the same. 【0027】 Another method for manufacturing a hologram according to the present invention involves emitting N laser beams from N lasers that generate non-coherent laser beams from each other, irradiating the N laser beams toward a region of a holographic recording material, reproducing N object beams toward the holographic recording material from an object light reproduction hologram positioned close to at least the surface or back surface of the region of the holographic recording material, and multiplexing N holograms in the region of the holographic recording material using the N laser beams and the N object beams, wherein the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the N lasers. 【0028】 Furthermore, in the above method for manufacturing a hologram, the propagation directions of the N object light beams may all be the same. 【0029】Another method for manufacturing holograms according to the present invention involves N sets of reference light and object light combinations, where the same set of reference light and object light interferes with each other, but other sets of reference light and object light do not interfere with each other. These N sets of reference light and object light combinations are simultaneously interfered with in a region of a holographic recording material to multiplex N holograms in that region of the holographic recording material. 【0030】 In the hologram recording apparatus and hologram manufacturing method of the present invention, when N holograms are simultaneously multiplexed using N sets of reference light and object light, the same set of reference light and object light interferes with each other, but other sets of reference light and object light do not interfere with each other. As a result, only the interference fringes of the same set of reference light and object light can be used as the hologram, and N holograms with high diffraction efficiency can be multiplexed at once. Other effects will be explained in the embodiments. 【0031】 (a) is a top view diagram illustrating the operating principle in the multiplexed recording area of ​​the present invention, perspective view. Schematic diagram of the hologram recording device of Example 1 of the present invention. (a) and (b) are photographs showing the regenerated light (diffraction) when the regenerated reference light in the comparative example and Example 1 is irradiated. (a) to (c) are diagrams illustrating the interference fringes formed by the first to third reference lights and the first to third object lights of the example. Schematic diagram of the hologram recording device of another embodiment of the present invention. Schematic diagram of the hologram recording device of another embodiment of the present invention. Example of a diffractive beam splitter. Diagram illustrating the formation of interference fringes by the split laser light of Example 3. Schematic diagram of the hologram recording device of another embodiment of the present invention. Schematic diagram of the hologram recording device of the comparative example. (a) to (f) are diagrams illustrating the interference fringes formed by the first to third reference lights and the first to third object lights of the comparative example. (a) and (b) are diagrams illustrating the orbit of the sun. 【0032】[Method for Manufacturing Holograms] The method for manufacturing holograms (multiplex recording method) of the present invention involves N sets of reference light and object light combinations, where the same set of reference light and object light interferes with each other, but other sets of reference light and object light do not interfere with each other. These N sets of reference light and object light combinations are simultaneously interfered with in a region of a holographic recording material to multiplex N holograms. In the present invention, N sets of reference light and object light combinations, that is, the first to Nth reference light and object light combination, the second to Nth reference light and object light combination, ..., the Nth reference light and object light combination, and N first to Nth object light combinations are irradiated onto a region of a holographic recording material at the same time. The first reference light is coherent with the first object light and therefore forms interference fringes, but is incoherent with the second to Nth reference light and object light and therefore does not form interference fringes. Therefore, a first hologram is recorded based on the interference fringes between the first reference light and the first object light, depending on the combination of the first reference light and the first object light. The second reference light also forms interference fringes because it is coherent with the second object light, but does not form interference fringes with the first and third to Nth reference lights and object lights, so a second hologram is recorded based on the interference fringes between the second reference light and the second object light. Similarly, a hologram of the Nth is recorded based on the interference fringes between the Nth reference light and the Nth object light, depending on the combination of the Nth reference light and the Nth object light. In this way, N holograms based on the interference fringes of the same set of light are multiplexed and recorded in one area of ​​the holographic recording material for N sets of reference light and object light combinations. 【0033】FIG. 1 is a diagram for explaining the operating principle in the multiplexed recording area of the present invention, (a) is a top view, and (b) is a perspective view. In the area 20a of the central holographic recording medium 20, N holograms are multiplexed by the first to N object lights having the same traveling direction and the first to N reference lights incident from various preset directions (for example, directions L1r to L3r). When light L1r (in the direction of θ = 0 in the figure) having the same incident angle as the first reference light is incident on the area 20a, it is diffracted by the first hologram to generate reproduced light Ld having the same emission angle as the first object light. When light L2r (in the direction of θ = 90° in the figure) having the same incident angle as the second reference light is incident from another angle θ, it is diffracted by the second hologram to generate reproduced light Ld having the same emission angle as the second object light. Also, even when light L3r having the same incident angle as the third reference light at a different elevation angle φ is incident, it is diffracted by the third hologram to generate reproduced light Ld having the same emission angle as the third object light. Thus, by multiplexing using the reference light in the direction where reproduction is required, holograms that interfere with light in various directions can be obtained. Further, if a second holographic recording medium in which N holograms are similarly multiplexed is prepared and bonded to the back surface, reproduced light Ld can also be generated in the same direction by the hologram of the second holographic recording medium for the light L4r incident from below. 【0034】Coherent reference light and object light are, for example, reference light and object light split from a laser beam emitted from a single laser device, where the difference between the optical path length of the reference light and the optical path length of the object light from the time of splitting until the two beams overlap is within the coherence length of the laser light. The coherence length is the maximum optical path difference at which the two split light waves can interfere, and is determined by the coherence length Lc = cT = c / Δf (c: speed of light, T: coherence time, Δf: spectral bandwidth). Furthermore, as a combination of coherent reference light and object light, a certain reference light and the regenerated light regenerated from a hologram by the incidence of that reference light can be used as object light. In this specification, a hologram used to regenerate object light is called an "object light regeneration hologram". The regenerated light generated from an object light regeneration hologram is coherent with the irradiated reference light, but incoherent with other sets of reference light and regenerated light regenerated by other sets of reference light. Therefore, by placing an object light reproduction hologram in close proximity to one region of the holographic recording material (which may also include other regions), the reference light illuminating the hologram (or the reference light that has passed through the hologram) and the reproduced light interfere, allowing the hologram to be recorded. The distance between one region of the holographic recording material and the object light reproduction hologram should be shorter than the coherence length. The coherent reference light and object light may be parallel light, diffuse light, or converged light when illuminating the holographic recording medium. 【0035】Non-coherent reference and object beams are, for example, (1) reference and object beams obtained by splitting a laser beam emitted from one laser device, where the difference in their optical path lengths is outside the range of the coherence length of the laser beam, and (2) laser beams emitted from different laser devices. Even if the laser beam is emitted from one laser device, if, after splitting it into a reference beam and object beam, the difference in their optical path lengths becomes longer than the coherence length of the laser beam, the reference beam and object beam will not interfere when superimposed, resulting in non-coherent reference and object beams. Furthermore, even with laser devices of the same model number, the laser beams emitted from two laser devices are usually non-coherent because their device-specific characteristics and oscillation conditions differ. Therefore, the first reference beam and first object beam obtained by splitting a laser beam emitted from a first laser device are non-coherent with the second reference beam and second object beam obtained by splitting a laser beam emitted from a second laser device. However, the first reference light and the first object light are coherent if the difference in optical path length is less than or equal to the coherence length, and interference fringes can be formed to record the first hologram. Similarly, the second reference light and the second object light are coherent if the difference in optical path length is less than or equal to the coherence length, and interference fringes can be formed to record the second hologram. It should be noted that even if laser light emitted from different laser devices happens to be coherent, this is merely a random occurrence and does not negate the fact that laser light emitted from different laser devices is non-coherent. 【0036】A CW laser (continuous wave laser) is a laser output by a CW oscillator. It can continuously irradiate laser light with a constant output and is not affected by changes in wavelength like a pulsed laser. Therefore, the output of the laser light does not fluctuate according to the irradiation time, and stable laser processing and irradiation effects can be obtained. A CW laser can also be controlled to repeatedly perform intermittent laser irradiation at high speed by utilizing a multimode-excited laser diode, etc. However, in such a configuration, it becomes a multimode oscillation with an extremely short coherence length. There is also a CW laser that is single-mode using a YAG laser. The coherence length of a CW laser varies individually depending on the spectral bandwidth of the single mode, etc., but is relatively long, ranging from several meters to several kilometers, and it is easy to obtain coherent reference light and object light. Conversely, with a CW laser, it is difficult to prepare reference light and object light with an optical path length difference outside the coherence length range as non-coherent reference light and object light, and it is preferable to use light emitted from different CW laser devices as non-coherent reference light and object light. 【0037】 A Q-switch laser is a laser that uses a Q-switch. First, the medium is excited in a state where the loss of the resonator is increased so that the laser does not oscillate initially, and energy is accumulated as an inverted distribution. Then, by rapidly reducing the loss of the resonator, stimulated emission is promoted and the accumulated energy is released as laser output in a short time at once. With a Q-switch laser, it is possible to generate high-energy pulses with a pulse width on the order of picoseconds to nanoseconds. The coherence length of a Q-switch laser varies individually depending on the spectral bandwidth, etc., but is relatively short, ranging from several millimeters to several centimeters. To obtain coherent reference light and object light, it is necessary to design such that the optical path length of the reference light and the optical path length of the object light are approximately the same. However, if the laser light emitted from a Q-switch laser is split and the optical path lengths of each split laser light are changed, it is possible to generate a large number of non-coherent laser lights from one laser device. 【0038】Semiconductor lasers are also used in the optical heads of recordable DVD-R and BD-R (Blu-ray discs), and those that oscillate in single mode for high output can be used as the lasers in this invention. The coherence length of semiconductor lasers is approximately several tens of centimeters to several meters. Semiconductor lasers are small, and by using N semiconductor lasers, N non-coherent laser beams can be obtained. 【0039】 [Comparative Example] Figure 10 is a schematic diagram of the hologram recording apparatus 101 of the comparative example. In the comparative example, a laser beam emitted from a single CW laser 12 is split into three, and each split laser beam is further split into an object beam and a reference beam, and these are simultaneously interfered with in one region of the holographic recording material 20 to perform multiplex recording. As shown in Figure 10, the hologram recording apparatus 101 has a CW laser device 12 (COMPASS 315-M 100 manufactured by Coherent, with a wavelength of 532 nm). The laser beam L emitted from the CW laser device 12 is split by first and second beam splitters 103a and 103b, and its direction of propagation is aligned by mirrors 104a and 104b to become three split laser beams L1, L2, and L3. The split laser beams L1, L2, and L3 have their light intensity adjusted by half-wave plates 31a-c and polarizers 32a-c, respectively, and their optical paths are changed by mirrors 33a-c. They are then incident on third beam splitters 34a-c, where they are split into reference light and object light, respectively. In Figure 10, the light that has passed through beam splitters 34a-c is designated as reference light L1r-L3r, and the light reflected by beam splitters 34a-c is designated as object light L1o-L3o. The reference light beams L1r-L3r are directed via shutters 35a-c and mirrors 36a-c at a predetermined incident angle θ. r1 ~θ r3 The light enters the holographic recording medium 20 from one surface. Meanwhile, object light L1o to L3o are directed by mirrors 38a to c via shutters 37a to c, respectively, at predetermined incident angles θ. o1 ~θ o3It is incident on the opposite surface of the holographic recording medium 20. Further, the hologram recording apparatus 101 is provided with photodetectors 41a to 41c for reference light and photodetectors 42a to 42c for object light, and is configured to detect the light intensities (powers) of the reference lights L1r to L3r, the object lights L1o to L3o, and the reproduced light. In addition, the hologram recording apparatus 101 includes a controller (computer) not shown, and the CW laser device and / or each shutter are controlled by the controller. The holographic recording material 20 is coated on a transparent substrate 21. 【0040】 In FIG. 10, with respect to the holographic recording medium 20, the first reference light L1r is incident at the first incident angle θ r1 and the first object light L1o is incident at the first incident angle θ o1 are both 56°, the second reference light L2r is incident at the second incident angle θ r2 and the second object light L2o is incident at the second incident angle θ o2 are both 45°, and the third reference light L3r is incident at the third incident angle θ r3 and the third object light L3o is incident at the third incident angle θ o3 are both arranged to be 36.4°. Table 1 shows the conditions during exposure when multiplexing holograms. The photodetector shows the result measured at φ8 mm in the central part. Based on this measurement result, the difference in the irradiation area on the recording surface due to the difference in the incident angle is used as a correction factor, and the power (μW / cm 2 ) on the recording surface is calculated. 【0041】 【0042】After adjusting the power to meet the conditions in Table 1, the holographic recording medium 20 was installed, and shutters 35a to c and shutters 37a to c were all opened for 10 seconds using a controller (not shown) to irradiate a region of the holographic recording medium 20 with the first to third reference lights L1r to L3r and the first to third object lights L1o to L3o, thereby recording a hologram. It was expected that three holograms would be recorded as multiplexed holograms: a first reflective hologram resulting from the interference of the first reference light L1r and the first object light L1o, a second reflective hologram resulting from the interference of the second reference light L2r and the second object light L2o, and a third reflective hologram resulting from the interference of the third reference light L3r and the third object light L3o. 【0043】 Figure 3(a) is a photograph showing the reconstructed light (diffraction) when a reconstructed reference light is irradiated onto a recorded hologram from the same direction as the third reference light L3r. The substrate 21 of the holographic recording medium 20 is placed in the center, and the reconstructed reference light is irradiated onto the holographic recording medium 20 from the lower right of the photograph at an incident angle of 36.4°. The transmitted light (0th order light) that the reconstructed reference light has passed through the holographic recording medium 20 is a bright spot C1, and a photodetector 41c for the third reference light is positioned there. A bright spot C2 is generated adjacent to the bright spot C1 of the transmitted light (0th order light) at the transmission position of the second reference light (photodetector 41b for the second reference light), and a bright spot C3 is also generated at the transmission position of the first reference light (photodetector 41a for the first reference light). Furthermore, a bright spot C4 is generated at the transmission position of the first object light (photodetector 42a for the first object light), a bright spot C5 is generated at the transmission position of the second object light (photodetector 42b for the second object light), and a bright spot C6 is generated at the transmission position of the third object light (photodetector 42c for the third object light). This is because the difference in optical path lengths of the three divided laser beams L1, L2, and L3, obtained by splitting the laser light emitted from the comparative example CW laser 12, was shorter than the coherence length. As a result, the first reference beam L1r formed interference fringes not only with the first object light L1o, but also with the second object light L2o and the third object light L3o, and furthermore, with the second reference beam L2r and the third reference beam L3r, and these interference fringes were also recorded as holograms. 【0044】Figures 11(a) to (f) summarize the interference fringes formed by the first to third reference light beams L1r to L3r and the first to third object light beams L1o to L3o of the comparative example. As shown in Figure 11(a), the first reference light beam L1r forms reflective interference fringes D1 to D3 between it and the first to third object light beams L1o to L3o incident from the opposite side, and as shown in Figure 11(b), it forms transmissive interference fringes D4 and D5 between it and the second reference light beam L2r and the third reference light beam L3r incident from the same side. Excluding the interference fringes already mentioned, the second reference light beam L2r forms reflective interference fringes D6 to D8 between it and the first to third object light beams L1o to L3o, and a transmissive interference fringe D9 between it and the third reference light beam L3r, as shown in Figure 11(c). Aside from the interference fringes already mentioned, the third reference light L3r forms reflective interference fringes D10 to D12 between itself and the first to third object lights L1o to L3o, respectively, as shown in Figure 11(d). Aside from the interference fringes already mentioned, the first object light L1o forms transmitted interference fringes D13 and D14 between itself and the second object light L2o and the third object light L3o, respectively, which are incident from the same side, as shown in Figure 11(e). Finally, aside from the interference fringes already mentioned, the second object light L2o forms a transmitted interference fringe D15 between itself and the third object light L3o, as shown in Figure 11(f). Thus, in the comparative example, not only are the same set of reference light and object light coherent, but other sets of reference light and object light are also coherent, resulting in the recording of not just the planned three holograms, but as many as 15 holograms. Therefore, when a regenerating reference light is irradiated from the same direction as the third reference light L3r, it interferes with the interference fringes D5, D9, D10, D11, and D12 involving the third reference light L3r. As shown in Figure 11(a), the interference fringe D5 diffracts the light corresponding to the first reference light (bright spot C3), the interference fringe D9 diffracts the light corresponding to the second reference light (bright spot C2), and the reflective interference fringes D10, D11, and D12 diffract the light corresponding to the first to third object light (bright spots C4 to C6), respectively. 【0045】Table 2 shows the power of the regenerated reference light when regenerated using the first to third reference lights L1r to L3r, the detection results of the light intensity (power) of the regenerated light detected by the reference light photodetectors (PDr1 to PDr3) 41a to c and the object light photodetectors (PDo1 to PDo3) 42a to c, and the absolute diffraction efficiency (η). The power of the transmitted light that passed through the holographic recording medium is also shown. The absolute diffraction efficiency (η) is calculated as power of regenerated light / power of regenerated reference light × 100. The M / # calculated from the sum of the absolute diffraction efficiencies was 1.80 (sum of the square roots of the absolute diffraction efficiencies). 【0046】 【0047】 [Example 1] Figure 2 is a schematic diagram of a hologram recording apparatus 1 according to an embodiment of the present invention. In this embodiment, three laser beams emitted from three CW lasers are split into object light and reference light, respectively, and simultaneously interfered in one region of the holographic recording material 20 to perform multiplex recording. As shown in Figure 2, the hologram recording apparatus 1 includes a first CW laser apparatus 11 (MSL-FN-532-100mW, wavelength 532nm, manufactured by CNI Optoelectronics Technology), a second CW laser apparatus 12 (COMPASS 315-M 100, wavelength 532nm, manufactured by Coherent), and a third CW laser apparatus 13 (Samba® 100, wavelength 532nm, manufactured by Cobolt). Three laser beams L1, L2, and L3 emitted from the first to third CW laser devices have their light intensity adjusted by half-wave plates 31a to c and polarizers 32a to c, respectively. The optical path is then changed by mirrors 33a to c, and the beams are incident on the third beam splitter 34a to c, where they are split into reference light and object light, respectively. In Figure 2, the light that has passed through the beam splitters 34a to c is designated as reference light L1r to L3r, and the light reflected by the beam splitters 34a to c is designated as object light L1o to L3o. The reference light L1r to L3r are each directed via shutters 35a to c and mirrors 36a to c to a predetermined incident angle θ. r1 ~θ r3The light enters the holographic recording medium 20 from one surface. Meanwhile, object light L1o to L3o are directed by mirrors 38a to c via shutters 37a to c, respectively, at predetermined incident angles θ. o1 ~θ o3 The light is incident on the opposite surface of the holographic recording medium 20. Furthermore, the hologram recording device 1 is equipped with photodetectors 41a to 41c for reference light and photodetectors 42a to 42c for object light, and is configured to detect the light intensity (power) of the reference light L1r to L3r, object light L1o to L3o, and regenerated light. In addition, the hologram recording device 1 includes a controller (computer) (not shown), which controls the first to third CW laser devices and / or each shutter. The holographic recording material 20 is coated on a transparent substrate 21. 【0048】 In Figure 2, the first incident angle θ is the angle at which the first reference light L1r is incident on the holographic recording medium 20. r1 and the first incident angle θ into which the first object light L1o is incident. o1 Both are 56°, and the second incident angle θ is the angle to which the second reference light L2r is incident. r2 and the second incident angle θ into which the second object light L2o is incident. o2 Both angles are 45°, and the third incident angle θ is the angle to which the third reference light L3r is incident. r3 and the third incident angle θ into which the third object light L3o is incident. o3 All are positioned so that the angle is 36.4°. Table 3 shows the exposure conditions when multiplexing the first hologram in this embodiment. The photodetector was measured at the center with a diameter of φ8 mm, and based on this measurement result, the difference in the irradiation area on the recording surface due to the difference in the incident angle was used as a correction coefficient to determine the power on the recording surface (μW / cm²). 2 ) is being calculated. 【0049】 【0050】After adjusting the power to meet the conditions in Table 3, the holographic recording medium 20 was installed, and shutters 35a to c and shutters 37a to c were all opened for 4 seconds using a controller (not shown) to irradiate a region of the holographic recording medium 20 with the first to third reference lights L1r to L3r and the first to third object lights L1o to L3o, thereby recording a hologram. It was expected that three holograms would be recorded as multiplexed holograms: a first reflective hologram resulting from the interference of the first reference light L1r and the first object light L1o, a second reflective hologram resulting from the interference of the second reference light L2r and the second object light L2o, and a third reflective hologram resulting from the interference of the third reference light L3r and the third object light L3o. 【0051】 After the first recording described above, the holographic recording medium 20 was rotated 90° and placed, and a second hologram was recorded multiple times in the same area of ​​the holographic recording medium 20. The exposure conditions when recording the second hologram multiple times in this embodiment are shown in Table 4. 【0052】 【0053】 After adjusting the power to meet the conditions in Table 4, the holographic recording medium 20 was rotated 90° and installed (from vertical to horizontal), and shutters 35a-c and 37a-c were all opened for 7 seconds using a controller (not shown) to irradiate a region of the holographic recording medium 20 with the first to third reference lights L1r-L3r and the first to third object lights L1o-L3o, thereby recording a hologram. It was expected that, for the second time as well, three holograms would be multiplexed and recorded: a first reflective hologram resulting from the interference of the first reference light L1r and the first object light L1o, a second reflective hologram resulting from the interference of the second reference light L2r and the second object light L2o, and a third reflective hologram resulting from the interference of the third reference light L3r and the third object light L3o. 【0054】Figure 3(b) is a photograph showing the regenerated light (diffraction) when a regenerated reference light is irradiated onto a recorded hologram from the same direction as the third reference light L3r. The substrate 21 of the holographic recording medium 20 is placed in the center, and the regenerated reference light is irradiated onto the holographic recording medium 20 from the lower right of the photograph at an incident angle of 36.4°. The transmitted light (0th order light) that the regenerated reference light passed through the holographic recording medium 20 is the bright spot C11, and the photodetector 41c for the third reference light is positioned there. Furthermore, a bright spot C12 is also generated at the transmission position of the third object light (photodetector 42c for the third object light), confirming that the regenerated reference light was diffracted by the reflective hologram and light corresponding to the third object light was regenerated. No other bright spots are shown in Figure 3(b), proving that the selectivity of multiplex recording is extremely high. 【0055】 Figures 4(a) to 4(c) summarize the interference fringes formed by the first to third reference rays L1r to L3r and the first to third object rays L1o to L3o of the embodiment. As shown in Figure 4(a), the first reference ray L1r forms a reflective interference fringe E1 only with the first object ray L1o incident from the opposite side, and does not interfere with the other reference rays L2r, L3r and object rays L2o, L3o. Similarly, as shown in Figure 4(b), the second reference ray L2r forms a reflective interference fringe E2 only with the second object ray L2o incident from the opposite side, and does not interfere with the other reference rays L1r, L3r and object rays L1o, L3o. The third reference ray L3r forms a reflective interference fringe E3 only with the third object ray L3o incident from the opposite side, and does not interfere with the other reference rays L1r, L2r and object rays L1o, L2o. Therefore, when a regeneration reference light is irradiated from the same direction as the third reference light L3r, only the light corresponding to the third object light (bright spot C12) is regenerated, diffracted by the interference fringes E3 involving the third reference light L3r. 【0056】Table 5 shows the power of the regenerated reference light, the light intensity (power) of the regenerated light detected by the reference light photodetectors (PDr1 to PDr3) 41a to c and the object light photodetectors (PDo1 to PDo3) 42a to c, and the absolute diffraction efficiency (η) when the holographic recording medium was placed in the orientation used for the first recording and regenerated using the first to third reference light L1r to L3r, respectively. The power of the transmitted light that passed through the holographic recording medium is also shown. The absolute diffraction efficiency (η) is calculated as power of regenerated light / power of regenerated reference light × 100. The M / # calculated from the sum of the absolute diffraction efficiencies was 1.82 (sum of the square roots of the absolute diffraction efficiencies). 【0057】 【0058】 Table 6 shows the power of the regenerated reference light, the light intensity (power) of the regenerated light detected by the reference light photodetectors (PDr1 to PDr3) 41a to c and the object light photodetectors (PDo1 to PDo3) 42a to c, when the holographic recording medium was placed in the orientation used for the second recording (rotated by 90°) and regenerated using the first to third reference light L1r to L3r, as well as the absolute diffraction efficiency (η). The power of the transmitted light that passed through the holographic recording medium is also shown. The absolute diffraction efficiency (η) is calculated as power of regenerated light / power of regenerated reference light × 100. The M / # calculated from the sum of the absolute diffraction efficiencies was 1.75 (sum of the square roots of the absolute diffraction efficiencies). 【0059】 【0060】In this example, three CW laser devices were used to simultaneously multiplex record three holograms (first recording), and then three more holograms were simultaneously multiplex recorded in the same area (second recording), resulting in the multiplex recording of six holograms. Therefore, the M / # due to the diffraction efficiency of these six multiplexed holograms was the sum of the M / # from the first and second recordings, which was 3.57 (1.82 + 1.75). In an experiment evaluating the dynamic range of the recording medium, the same holographic recording medium as in this example was subjected to multiplex recording with a Bragg mismatch between the reference light and the object light 24 times, and the result was M / # = 2.763. This value was higher for the multiplex recording method of the present invention than for the M / # due to the diffraction efficiency based on 24 holograms recorded sequentially. Therefore, it was suggested that the multiplex recording method of the present invention has the potential to efficiently collect light from more directions compared to the conventional method of multiplex recording holograms sequentially. 【0061】 The hologram recording device 1 in Figure 2 can be modified in various ways. For example, although Figure 2 uses three lasers 11, 12, and 13, the number can be increased further. Also, in Figure 2, a reflective hologram is recorded by irradiating the reference light and object light from opposite sides of the holographic recording medium, but a transmissive hologram can also be recorded by irradiating them from the same side, and multiplex recording of transmissive and reflective holograms can be performed by irradiating some pairs of reference light and object light from the same side and other pairs from the opposite side. By placing lenses or the like in the optical path, the object light and / or reference light may be irradiated onto the holographic recording medium as parallel light, diffuse light, or focused light. 【0062】[Example 2] Figure 5 is a schematic diagram of a hologram recording device 51 according to another embodiment of the present invention. In this embodiment, N laser beams emitted from N lasers that generate non-coherent laser beams are each split into object beams and reference beams, and the N object beams are irradiated onto a region 20a of the holographic recording material 20 at the same angle of incidence. The hologram recording device 51 has N lasers (five are shown as examples in Figure 5) 52a to e that generate non-coherent laser beams. The N laser beams L1 to L2 emitted from the N lasers 52a to e are each incident on beam splitters 53a to e and are split into object beams L1o to L5o that pass through the beam splitters and travel in a straight line, and reference beams L1r to L5r that are reflected by the beam splitters. The N object beams L1o to L5o are transmitted to the irradiation position by a single optical fiber 55. To facilitate the incidence of N object light beams L1o to L5o into the optical fiber 55, a tapered optical fiber 54 may be used. The tapered optical fiber 54 is an optical fiber in which the input diameter is physically larger than the output diameter, and the diameter gradually decreases from the input to the output. By injecting N object light beams L1o to L5o into the large-diameter input, the direction of propagation of the N object light beams L1o to L5o is aligned in one direction while they are transmitted through the tapered optical fiber 54. One end of the optical fiber 55 is placed at the output port of the tapered optical fiber 54, and the other end of the optical fiber 55 is positioned toward a region 20a of the holographic recording material 20. The N object light beams L1o to L5o are emitted from the other end of the optical fiber 55 toward the region 20a of the holographic recording material 20 at the same angle of incidence. If the tapered optical fiber 54 is sufficiently long, the output of the tapered optical fiber 54 may be placed at the irradiation position without providing the optical fiber 55. N reference beams L1r to L5r are incident on N optical fibers 56a to e, transmitted through the optical fibers 56a to e to the irradiation position, and emitted toward a region 20a of the holographic recording material 20 at different incident angles. The hologram recording device 51 ensures that the difference between the optical path lengths of the N object beams L1o to L5o and the optical path lengths of the N reference beams L1r to L5r is within the range of the coherence lengths of the N lasers 52a to e (e.g., the length of each optical fiber). 【0063】 The hologram recording device 51 in Figure 5 includes a shutter and a controller (not shown) that control the irradiation timing of N object beams L1o to L5o and N reference beams L1r to L5r onto the holographic recording material 20. By emitting N laser beams from N lasers that generate mutually non-coherent laser beams, splitting the N laser beams into object beams and reference beams, irradiating a region of the holographic recording material with the N reference beams at different incident angles, and irradiating a region of the holographic recording material with the N object beams, N holograms can be multiplexed and recorded on a single region of the holographic recording material. 【0064】 The hologram recording device 51 in Figure 5 is subject to various modifications. For example, although beam splitters 53a to 53e are individually provided in Figure 5, a single common beam splitter may be used. Furthermore, an optical system for adjusting the light intensity may be included in the optical path. Additionally, by using lenses at the end faces of the optical fibers or by arranging separate lenses, object light and / or reference light may be irradiated onto the holographic recording medium as parallel light, diffuse light, or focused light. Also, in Figure 5, the N object beams can be irradiated onto a region of the holographic recording material at different incident angles by providing N optical fibers. Furthermore, although the N object beams are incident on the tapered optical fiber 54 in Figure 5, a configuration where only some object beams that need to travel in the same direction are incident on the tapered optical fiber 54 is also possible (the other object beams can be individually irradiated on optical fibers). 【0065】[Example 3] Figure 6 is a schematic diagram of a hologram recording apparatus 61 according to another embodiment of the present invention. In this embodiment, laser light emitted from one Q-switched laser 62 is split into N split laser beams, and the optical distances of the N split lasers are made to differ by more than the coherence length of the Q-switched laser to make them non-coherent. The non-coherent N split lasers are used to regenerate N object beams toward the holographic recording material from an object beam regeneration hologram 66 positioned close to the front or back side of at least one region 20a of the holographic recording material 20, and this is an example of an apparatus that performs multiplex recording using the N split lasers and the regenerated N object beams. The hologram recording apparatus 61 includes a Q-switched laser 62, a beam splitter 63, a collimator lens 64, and N (five are illustrated in Figure 6) optical fibers 65a to e. The laser beam L emitted from the Q-switched laser 62 is split into N divided laser beams L1 to L5 by the beam splitter 63 and incident on the end faces of optical fibers 65a to e by the collimator lens 64. 【0066】The beam splitter 63 preferably splits the laser light in a plane perpendicular to the optical axis so that the optical axes of the N divided laser beams are arranged in two dimensions. For example, a diffractive optical element (DOE) as shown in Figure 7 can be used, but it is not limited to this. A diffractive beam splitter can split one laser beam into multiple beams that retain the original beam characteristics (excluding power and propagation angle), and depending on the diffraction pattern, it can generate a one-dimensional beam array of 1 row × N columns or a two-dimensional beam matrix of m rows × k columns (m × k = N). The N divided laser beams L1 to L5 split by the diffractive beam splitter remain parallel light as before splitting, and as a whole they spread out from the optical axis. However, the collimator lens 64 causes each of them to become focused light, and as a whole they become light parallel to the optical axis. The N divided laser beams L1 to L5 are each incident on the N optical fibers 65a to e, transmitted through the optical fibers 65a to e to the irradiation position, and emitted toward a region 20a of the holographic recording material 20 at different incident angles. The hologram recording device 61 ensures that the lengths of the N optical fibers 65a to e differ by at least the coherence length of the Q-switched laser 62, thereby making the N divided laser beams L1 to L5 non-interfering with each other. The beam splitter 63 may be configured such that, in a plane perpendicular to the optical axis, the optical axes of the N divided laser beams are positioned at the vertices of concentric polygons of different sizes, or at least on the circumferences of concentric circles of different diameters. 【0067】The object light reproduction hologram 66 is positioned close to the front or back side of at least one region of the holographic recording material 20 and interferes with N divided laser beams L1 to L5 to reproduce N object light beams toward the holographic recording material. If the object light reproduction hologram 66 is reflective, it is positioned close to the back side of at least one region of the holographic recording material 20, and object light is reproduced from the object light reproduction hologram 66 to the front side by the divided laser beams that have passed through the holographic recording material 20, and reflective interference fringes are formed between the divided laser beams irradiated from the front side and the reproduced object light. If the object light reproduction hologram 66 is transmissive, it is positioned close to the front side of at least one region of the holographic recording material 20, and object light is reproduced from the object light reproduction hologram 66 to the back side by the divided laser beams before they are irradiated onto the holographic recording material 20, and transmissive interference fringes are formed between the divided laser beams that have passed through the object light reproduction hologram 66 and the reproduced object light. The object light reproduction hologram 66 can be manufactured, for example, by the hologram recording device 51 shown in Figure 5. That is, by multiplex recording N holograms using N reference beams L1r to L5r set to the same incident angle as the N divided laser beams L1 to L5, and N object beams, light corresponding to the N object beams can be reproduced when the N divided laser beams L1 to L5 are incident. The object light reproduction hologram 66 may be located not only in one area of ​​the holographic recording material 20, but multiple object light reproduction holograms 66 may be arranged in close proximity over a wider area (for example, in a row). 【0068】Figure 8 is a diagram illustrating the formation of interference fringes by the segmented laser beams L1 to L5 of Example 3. As shown in Figure 8(a), the segmented laser beams L1 to L5 are incident on and transmitted through a region of the holographic recording material 20 and an object light reproduction hologram 66 placed in close proximity, at various incident angles, and diffracted light Ld in the same direction is reproduced from the object light reproduction hologram 66. First, focusing on the first segmented laser beam L1, the first segmented laser beam L1 is non-coherent with the second to fifth segmented laser beams L2 to L5, and does not form interference fringes with these beams. However, as shown in Figure 8(b), when it is transmitted through the holographic recording material 20 and incident on the object light reproduction hologram 66, the first segmented laser beam L1 is diffracted by the first hologram, and a first diffracted light L1d that is coherent with the first segmented laser beam L1 is reproduced. Because the first split laser beam L1 and the first diffracted light L1d are coherent, interference fringes are formed, and a reflective hologram is recorded on the holographic recording material 20. However, the distance between the holographic recording material 20 and the object light reproduction hologram 66 must be shorter than the coherence length of the Q-switched laser 62. Here, the first diffracted light L1d is incoherent with the second to fifth split laser beams L2 to L5 (and the diffracted light L2d to L5d reproduced by them), and no interference fringes are formed with these beams. Next, as shown in Figure 8(c), when the second split laser beam L2 passes through the holographic recording material 20 and enters the object light reproduction hologram 66, the second split laser beam L2 is diffracted by the second hologram, and a second diffracted light L2d (in this embodiment, traveling in the same direction as the first diffracted light L1d, but it does not need to be in the same direction) is reproduced, and a reflective hologram is recorded in the same way. Furthermore, with the third split laser beam L3, as shown in Figure 8(d), the third hologram of the object light reproduction hologram 66 reproduces a third split laser beam L3 and a third diffracted light L3d (in this embodiment, traveling in the same direction as the first diffracted light L1d, but it does not need to be in the same direction), and a reflective hologram is recorded in the same way. Although Figures 8(b) to 8(d) have been explained in order, in reality, the first to Nth divided laser beams are irradiated simultaneously, so the diffracted light is regenerated simultaneously and multiplexed onto the holographic recording medium at the same time.Thus, the regenerated diffracted light is coherent only with the regenerated reference light and incoherent with other reference light and diffracted light, so that a hologram with high diffraction efficiency is multiplexed and recorded in one area of ​​the holographic recording medium 20. 【0069】 The hologram recording device 61 in Figure 6 can be modified in various ways. For example, it may have an optical system for adjusting the light intensity. Alternatively, the end face of the optical fiber may be used as a lens, or a separate lens may be placed to irradiate the holographic recording medium with the split laser beam as parallel light, diffused light, or focused light. In Figure 6, N split lasers are split from one Q-switched laser, but N laser beams emitted from N different lasers may also be used (for example, in Example 4). 【0070】 Because the hologram recording apparatus 61 of this embodiment 3 uses a Q-switched laser, it can expose materials in a short time using high-energy pulses with a pulse width of picoseconds to nanoseconds. For example, by sequentially recording while moving the holographic recording material or while moving the irradiation optical system, multiplex recording over a large area is possible, enabling mass production. 【0071】[Example 4] Figure 9 is a schematic diagram of a hologram recording apparatus 91 of another embodiment of the present invention. In this embodiment, N laser beams L1 to L5 emitted from N lasers (e.g., semiconductor lasers, CW lasers, etc.) 92a to e reproduce N object light beams directed toward the holographic recording material from an object light reproduction hologram 96 positioned close to the surface or back side of at least one region 20a of the holographic recording material 20, and this is an example of an apparatus that performs multiplex recording using N divided lasers and the reproduced N object light beams. The N laser beams emitted from the N lasers 92a to e are basically non-coherent, so even if the N laser beams overlap, no interference fringes are formed. However, each is coherent with the object light reproduced from the object light reproduction hologram 96, and interference fringes can be formed between the irradiated laser beams and the reproduced object light. The hologram recording device 91 includes N lasers 92a to e, an object light reproduction hologram 96, and a controller (not shown) for controlling the N lasers. The N lasers 92a to e generate N non-coherent laser beams L1 to L5 and are arranged around the holographic recording material 20 such that the laser beams are incident at different angles of incidence toward a region 20a of the holographic recording material 20. For example, N semiconductor lasers or CW lasers of the same or different types can be used as the N lasers 92a to e. Optical systems such as mirrors and lenses may be placed between the N lasers 92a to e and the holographic recording material 20. The object light reproduction hologram 96 is the same as the hologram 66 in Figure 6 and interferes with the N laser beams L1 to L5 to reproduce N object beams toward the holographic recording material. The distance between the holographic recording material 20 and the object light reproduction hologram 96 is shorter than the coherence length of the N lasers 92a to e. A controller (not shown) is, for example, a computer, which controls the irradiation timing of N lasers 92a to e so that N laser beams L1 to L5 simultaneously irradiate a region 20a of the holographic recording material 20. 【0072】In the hologram recording device 91 shown in Figure 9, a controller (not shown) emits N laser beams L1 to L5 from N lasers 92a to e towards a region 20a of the holographic recording material 20. These beams enter and pass through the region of the holographic recording material 20 and the adjacent object light reproduction hologram 96 at different angles of incidence. The emitted N laser beams L1 to L5 and the N object light beams reproduced from the object light reproduction hologram 96 interfere in a one-to-one manner, resulting in the multiplex recording of N holograms in the region of the holographic recording material 20. 【0073】 20 Holographic recording medium 21 Substrate L1r to L3r Reference light L1o to L3o Object light E1 to E3 Interference fringes

Claims

1. A hologram recording device comprising: a Q-switched laser; a beam splitter that splits laser light emitted from the Q-switched laser into N divided laser beams; an optical system that irradiates the N divided laser beams toward a region of a holographic recording material; and an object light regeneration hologram positioned close to at least the front or back surface of the region of the holographic recording material, which interferes with the N divided laser beams to regenerate N object beams toward the holographic recording material, wherein the optical distances of the N divided laser beams from the Q-switched laser to the region of the holographic recording material differ by at least the coherence length of the Q-switched laser, and the N divided laser beams and the N object beams multiplex recording N holograms in the region of the holographic recording material.

2. The hologram recording apparatus according to claim 1, wherein the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the Q-switched laser.

3. The hologram recording apparatus according to claim 1, wherein the directions of propagation of the N object light beams are all the same.

4. The hologram recording apparatus according to claim 1, wherein the optical system irradiates the one region of the holographic recording material with the N divided laser beams as parallel light.

5. The hologram recording apparatus according to claim 1, wherein the beam splitter divides the laser light emitted from the Q-switched laser in a plane perpendicular to the optical axis such that the optical axes of N divided laser beams are arranged in two dimensions.

6. The hologram recording apparatus according to claim 5, wherein the beam splitter divides the optical axes of N divided laser beams in a plane perpendicular to the optical axis such that they are arranged in an m x k ​​matrix, at the vertices of concentric polygons of different sizes, or on at least a portion of the circumference of concentric circles of different diameters.

7. The hologram recording apparatus according to claim 1, comprising N optical fibers corresponding to each of the N divided laser beams, wherein the lengths of the N optical fibers differ by at least the coherence length of the Q-switched laser.

8. A method for manufacturing a hologram, comprising: emitting laser light from a Q-switched laser; splitting the laser light emitted from the Q-switched laser into N divided laser beams; irradiating one region of a holographic recording material with the N divided laser beams; regenerating N object beams toward the holographic recording material from an object beam reproduction hologram positioned close to at least the front or back surface of the one region of the holographic recording material; and multiplexing N holograms in the one region of the holographic recording material using the N divided laser beams and the N object beams, wherein the optical distances of the N divided laser beams from the Q-switched laser to the one region of the holographic recording material differ by at least the coherence length of the Q-switched laser.

9. The method for manufacturing a hologram according to claim 8, wherein the optical axes of the N divided laser beams divide the laser beam emitted from the Q-switched laser so that it is arranged in two dimensions in a plane perpendicular to the optical axis.

10. The method for manufacturing a hologram according to claim 9, wherein the optical axes of the N divided laser beams are divided in a plane perpendicular to the optical axes such that they are arranged in an m x k ​​matrix on at least a portion of the vertices of concentric polygons of different sizes, or on at least a portion of the circumferences of concentric circles of different diameters.

11. A hologram recording apparatus comprising: N lasers that generate mutually non-coherent laser light; a beam splitter that splits the N laser beams emitted from the N lasers into object light and reference light; a reference light optical system that directs the N reference light beams toward a region of the holographic recording material so that each beam has a different incident angle toward the holographic recording material; an object light optical system that directs the N object light beams toward the region of the holographic recording material; and a controller that controls the N reference light beams and the N object light beams to simultaneously direct them toward the region of the holographic recording material, wherein the apparatus multiplexes N holograms toward the region of the holographic recording material.

12. The hologram recording apparatus according to claim 11, wherein the optical system for object light irradiates the N object light beams toward the one region of the holographic recording material at the same angle of incidence.

13. The hologram recording apparatus according to claim 11, wherein the optical system for object light includes tapered optical fibers into which at least a portion of the N object light is incident, and the tapered optical fibers have a shape in which the input diameter is physically larger than the output diameter, and the diameter gradually decreases from the input to the output.

14. The hologram recording apparatus according to claim 11, wherein the optical system for the reference light includes N optical fibers that transmit each of the N reference light beams.

15. A method for manufacturing a hologram for recording a hologram on a holographic recording material, comprising: emitting N laser beams from N lasers that generate mutually non-coherent laser beams; splitting each of the N laser beams into object beam and reference beam; irradiating a region of the holographic recording material with the N reference beams so that they have different angles of incidence to the holographic recording material; and irradiating the region of the holographic recording material with the N object beams; and multiplexing N holograms on the region of the holographic recording material.

16. A hologram recording apparatus comprising: N lasers that generate non-coherent laser light from each other; an object light reproduction hologram positioned in close proximity to the front or back surface of at least one region of a holographic recording material; and a controller that controls the N lasers, wherein the N lasers are arranged so that N laser beams emitted from the N lasers irradiate the one region of the holographic recording material; the object light reproduction hologram interferes with the N laser beams to reproduce N object beams directed toward the holographic recording material; and the controller controls the N lasers so that the N laser beams irradiate the one region of the holographic recording material simultaneously.

17. The hologram recording apparatus according to claim 16, wherein the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the N lasers.

18. The hologram recording apparatus according to claim 16, wherein the propagation directions of the N object light beams are all in the same direction.

19. A method for manufacturing a hologram, comprising: emitting N laser beams from N lasers that generate non-coherent laser beams from each other; irradiating the N laser beams toward a region of a holographic recording material; reproducing N object beams toward the holographic recording material from an object light reproduction hologram positioned close to at least the surface or back surface of the region of the holographic recording material; and multiplex recording N holograms in the region of the holographic recording material using the N laser beams and the N object beams, wherein the distance between the holographic recording material and the object light reproduction hologram is shorter than the coherence length of the N lasers.

20. The method for manufacturing a hologram according to claim 8, 15, or 19, characterized in that the directions of propagation of the N object light rays are all the same.

21. A method for manufacturing a hologram, comprising simultaneously interfering N sets of reference light and object light combinations in a region of a holographic recording material, wherein the same set of reference light and object light interferes with each other, but other sets of reference light and object light do not interfere with each other, thereby multiplexing N holograms in that region of the holographic recording material.

Images