Hologram manufacturing apparatus and hologram manufacturing method

Abstract

The hologram manufacturing apparatus includes: a main hologram in which a diffraction grating is formed; a copy hologram disposed close to the main hologram; a first light source that emits a first laser beam satisfying Bragg diffraction conditions in the diffraction grating with respect to the main hologram and the copy hologram; a second light source that emits a second laser beam that does not satisfy the Bragg diffraction condition in the diffraction grating with respect to the main hologram and the copy hologram; and a sensor that measures the second laser light. The hologram manufacturing apparatus terminates the exposure of the copy hologram by the first laser beam on the basis of the measurement result of the sensor.

Description

Technical Field

[0001] The present disclosure relates to a hologram manufacturing device and a hologram manufacturing method. Background Art

[0002] Conventionally, there is a known device for manufacturing a replica hologram using a master hologram. In Patent Document 1, a laser beam is incident on a master hologram to generate diffracted light, and the diffracted light is used to expose a hologram photosensitive material (photopolymer) of the replica hologram. In this way, a replica hologram can be manufactured.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-321962 Summary of the invention

[0006] In general, the manufacture of a replica hologram is performed by managing the exposure time of the photopolymer, that is, the manufacture of a replica hologram is performed by managing the amount of change in the refractive index of the photopolymer based on the light irradiation time to the photopolymer. The amount of change in the refractive index of the photopolymer is mainly determined by the cumulative exposure amount, which is the product of the light intensity of the light source and the irradiation time, but is also affected by temperature, batch variation of the sensitivity of the refractive index change of the photopolymer itself, and the like.

[0007] Furthermore, in order to manufacture a replica hologram, the first-order diffracted light for the replica hologram is required, but even if the refractive index change of the photopolymer is as designed, if the thickness of the photopolymer is different from the designed value, an error will occur in the first-order diffracted light. In particular, since the photopolymer is a transparent material, it is very difficult to measure the thickness of the photopolymer if it is sandwiched between transparent substrates.

[0008] For the above reasons, if the exposure time of the photopolymer is managed only by the light irradiation time for the photopolymer, there is a concern that the photopolymer itself of the copied hologram and the first-order diffracted light for the copied hologram may differ from the designed values. Therefore, the accuracy of the copied hologram may decrease.

[0009] Therefore, an object of the present disclosure is to provide a hologram manufacturing apparatus and a hologram manufacturing method that improve the accuracy of replicating a hologram.

[0010] In order to achieve the above-mentioned purpose, an embodiment of the present disclosure relates to a hologram manufacturing device comprising: a master hologram formed with a diffraction grating; a replica hologram arranged close to the master hologram; a first light source emitting a first laser light satisfying the Bragg diffraction condition in the diffraction grating for the master hologram and the replica hologram; a second light source emitting a second laser light not satisfying the Bragg diffraction condition in the diffraction grating for the master hologram and the replica hologram; and a sensor measuring the second laser light after passing through the master hologram and the replica hologram. The hologram manufacturing device ends the exposure of the replica hologram using the first laser light based on the measurement result of the sensor.

[0011] In order to achieve the above-mentioned purpose, another embodiment of the present disclosure relates to a hologram manufacturing device comprising: a master hologram formed with a diffraction grating; a replica hologram arranged close to the master hologram; a first light source emitting a first laser light for exposing the replica hologram at a first incident angle to the replica hologram; a second light source emitting a second laser light at a second incident angle different from the first incident angle to the replica hologram; and a sensor for measuring the second laser light reflected by the replica hologram. The hologram manufacturing device ends the exposure of the replica hologram using the first laser light based on the measurement result of the sensor.

[0012] According to the present disclosure, it is possible to improve the accuracy of replicating a hologram. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the hologram producing apparatus according to the first embodiment.

[0014] Figure 2 It is a diagram for explaining the structure of the hologram recorder according to the first embodiment.

[0015] Figure 3 It is a cross-sectional view showing a state in which the hologram recording material according to the first embodiment is being exposed.

[0016] Figure 4 It is a diagram for explaining spot light formed on the light receiving surface of the light receiving sensor according to the first embodiment.

[0017] Figure 5 It is a schematic diagram of a hologram producing apparatus according to the second embodiment.

[0018] Figure 6 It is a schematic diagram of a hologram manufacturing apparatus according to the third embodiment.

[0019] Figure 7This is a graph showing the relationship between the diffraction efficiency when creating a replica hologram and the amount of change Δn in the refractive index of the replica hologram according to the third embodiment.

[0020] Figure 8 It is a schematic diagram of a hologram manufacturing apparatus according to a fourth embodiment.

[0021] Fig. 9 It is a cross-sectional view of a replica hologram when producing a replica hologram according to the fourth embodiment.

[0022] Fig.10 This is a graph showing the relationship between the diffraction efficiency when creating a replica hologram and the amount of change Δn in the refractive index of the replica hologram according to the fourth embodiment.

[0023] Fig.11 It is a side view of the hologram producing apparatus involved in the fifth embodiment.

[0024] Fig.12 It is a top view of the hologram producing apparatus involved in the fifth embodiment.

[0025] Fig.13 It is a diagram showing a state during exposure of a hologram recorder according to the fifth embodiment.

[0026] Fig.14 It is a perspective view showing the incident angle of the laser light L2 on the replica hologram according to the fifth embodiment.

[0027] Fig.15 It is a cross-sectional view showing a state during exposure of a replica hologram according to the fifth embodiment.

[0028] Fig.16 It is a plan view showing a state in which a replica hologram according to the fifth embodiment is being exposed.

[0029] Fig.17 It is a side view of the hologram producing apparatus involved in the 6th embodiment.

[0030] Fig.18 It is a top view of the hologram producing apparatus involved in the 6th embodiment.

[0031] Fig.19 It is a perspective view of a hologram producing apparatus according to the sixth embodiment. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. The following description of the preferred embodiments is essentially illustrative and is not intended to limit the present invention, its applications or its uses. In addition, in the following description, the same reference numerals are used for the same parts, and detailed description is appropriately omitted.

[0033] (First embodiment)

[0034] (Overall structure of hologram manufacturing device)

[0035] Figure 1 Schematic diagram of a hologram manufacturing device according to the first embodiment. Figure 1 In the diagram, the width directions of the hologram recording medium 4 are defined as the X direction and the Z direction, and the thickness direction of the hologram recording medium 4 is defined as the Y direction.

[0036] like Figure 1 As shown, the hologram manufacturing apparatus according to the first embodiment includes light sources 1 and 2 , a half mirror 3 , a hologram recording medium 4 , a condenser lens 5 , and a light receiving sensor 6 .

[0037] Light source 1 (first light source) is a light source for irradiating laser light, and irradiates laser light L1 (exposure light). Laser light L1 is a laser light having a long coherence distance (coherence length), and is parallel light with uniform intensity distribution having very high spatial coherence and small wavefront aberration. Laser light L1 irradiates an area including at least the effective area of ​​photopolymers 412 and 422 described later. In addition, the coherence distance of laser light L1 is preferably greater than the length obtained by adding the master hologram 41 and the replica hologram 42 described later. In addition, light source 1 may also be composed of an LED (Light Emitting Diode) or the like.

[0038] Light source 2 (second light source) is a light source for irradiating laser light, and irradiates laser light L2 (reference light). Laser light L2, like laser light L1, is a laser light with a long interference distance (coherence length), and is a parallel light with uniform intensity distribution having very high spatial coherence and small wavefront aberration. Laser light L2 irradiates the approximate center of the effective area of ​​the master hologram 41 and the replica hologram 42. In addition, light source 2 can also be composed of LED (Light Emitting Diode) or the like. In addition, light sources 1 and 2 can also be the same light source, or laser light L2 can be light separated from laser light L1.

[0039] The half mirror 3 reflects the laser light L1 emitted from the light source 1 and causes it to enter the hologram recording body 4. In addition, the half mirror 3 transmits the laser light L2 emitted from the light source 2 and causes it to enter the hologram recording body 4. The reflectivity of the half mirror 3 is very high, for example, a reflectivity of 95% or more. Figure 1 As shown, the laser beam L1 is incident on the hologram recording medium 4 by passing through the half mirror 3 so as to form an angle ε with respect to the laser beam L2. That is, the laser beams L1 and L2 are combined by passing through the half mirror 3.

[0040] The condenser lens 5 is a lens for condensing the laser light L3 to L6 transmitted through the hologram recording body 4. An aperture 7 for measurement is formed below the hologram recording body 4, and the condenser lens 5 condenses the laser light L3 to L6 emitted through the aperture 7. The focal length of the condenser lens 5 is f.

[0041] The light receiving sensor 6 (first sensor) is a light receiving sensor having a two-dimensional pixel structure. For example, the light receiving sensor 6 is a CCD camera, a CMOS camera, etc. The light receiving sensor 6 is arranged at a distance f from the condenser lens 5. That is, the light receiving sensor 6 is arranged on the emission side focal plane of the condenser lens 5.

[0042] (Structure of hologram recording body)

[0043] Figure 2 (a) is a cross-sectional view showing the structure of the hologram recording medium according to the first embodiment.

[0044] like Figure 1 as well as Figure 2 As shown in (a) of FIG. 8 , the hologram recording medium 4 is composed of a master hologram 41 and a replica hologram 42 . In the present embodiment, the master hologram 41 is irradiated with the laser light L1 , so that the same diffraction grating as the diffraction grating g1 formed on the master hologram 41 is formed on the replica hologram 42 .

[0045] like Figure 1 as well as Figure 2 As shown in (a) of FIG. 1 , the master hologram 41 includes a transparent substrate 411 , a photopolymer 412 , and a protective film 413 . The transparent substrate 411 , the photopolymer 412 , and the protective film 413 are stacked.

[0046] The transparent substrate 411 is a flat plate with high transmittance, and for example, quartz, optical glass, etc. can be used. In addition, an anti-reflection film is formed on the upper surface of the transparent substrate 411 in the figure.

[0047] The photopolymer 412 is formed, for example, of an optical material whose refractive index changes when it is exposed to visible light. The amount of change in the refractive index of the photopolymer 412 is determined by the amount of energy of the light received by the photopolymer 412, that is, the product of the light intensity and time. In addition, the photopolymer 412 can stop the change in the refractive index by irradiating ultraviolet rays. In the photopolymer 412, a refractive index distribution (diffraction grating g1) is formed in advance using visible light with different light intensities, and then it is processed so that the refractive index distribution does not change due to ultraviolet irradiation. Thus, given interference fringes are formed in the photopolymer 412. In addition, the refractive index of the photopolymer 412 is approximately 1.5 to 1.6, and the amount of change in the refractive index based on visible light is approximately 0.01 to 0.1. In addition, the thickness t of the photopolymer 412 is formed to be between 1μm and 100μm. In addition, the thicker the thickness t of the photopolymer 412, the higher the diffraction efficiency at the photopolymer 412. In this case, the characteristics of the first-order diffracted light with respect to the incident angle to the photopolymer 412 also become sensitive, and the first-order diffracted light is greatly attenuated by a small change in the incident angle.

[0048] The protective film 413 is a thin transparent protective layer for protecting the photopolymer 412, and is formed of a material that is not easily damaged, such as thin glass with high transmittance. In addition, a reflection prevention film is formed on the upper side of the protective film 413. The thickness of the protective film 413 is at least thinner than the transparent substrate 411. In addition, it is preferred that the average refractive index of the transparent substrate 411 and the photopolymer 412 is close to the refractive index of the protective film 413.

[0049] The replica hologram 42 includes a transparent substrate 421, a photopolymer 422, and a protective film 423. The transparent substrate 421, the photopolymer 422, and the protective film 423 are stacked.

[0050] Transparent substrate 421, photopolymer 422 and protective film 423 are respectively the same as transparent substrate 411, photopolymer 412 and protective film 413. However, photopolymer 422 has the same thickness t as photopolymer 412, has no refractive index distribution in the initial state, and is not irradiated with ultraviolet rays.

[0051] like Figure 1 As shown, the replica holograms 42 are arranged closely and parallel to each other in a state rotated 180 degrees with respect to the master hologram 41 .

[0052] As described above, a refractive index distribution (diffraction grating g1) is pre-formed in the photopolymer 412. The refractive index distribution of the photopolymer 412 has a distribution in the XY cross section and is the same in the Z-axis direction. That is, the refractive index distribution of the photopolymer 412 is the same in the XY cross section at any position of the Z-axis. The refractive index distribution in the photopolymer 412 is periodically formed with a high refractive index portion and a low refractive index portion. In the photopolymer 412, a so-called diffraction grating based on a refractive index distribution with thickness, namely a Bragg diffraction grating, is formed. The diffraction grating is formed with a spacing of d and an angle φ relative to the Y-axis in the XY plane. Therefore, in the X-axis direction, the spacing of the diffraction grating is d / cos (φ).

[0053] Figure 2 (b) shows Figure 2 (a) is a graph showing the refractive index of the cross section AA and the cross section BB of the photopolymer 412. Figure 2 As shown in (b), the refractive index of section AA and section BB changes in a sinusoidal wave shape. The average refractive index is n, and the refractive index change is Δn. The only difference in the refractive index change between section AA and section BB is that the waveforms are laterally offset. If a highly interfering laser is incident on the main hologram 41 having such a periodic refractive index distribution, light diffraction called Bragg diffraction is generated. As a characteristic of Bragg diffraction, strong diffracted light in a specific direction, namely, first-order diffracted light, is generated. In addition, with respect to the emitted light based on Bragg diffraction, 0th-order diffraction and first-order light constitute the majority, and almost no higher-order diffraction light is generated.

[0054] When the average refractive index in the photopolymer 412 is n, the pitch of the diffraction grating is d, the incident angle to the diffraction grating is θ, and the wavelength of the incident light is λ, the Bragg diffraction condition in the photopolymer 412 becomes 2×n×d×sin(θ)=λ. In addition, regarding the direction of the light, the angle changes based on Snell's law occur due to refraction in the photopolymer 412. That is, if the direction relative to the Y axis in the air is α, then since the refractive index of the photopolymer 412 is n, for the direction β in the photopolymer 412, sin(α)=n×sin(β).

[0055] If the Bragg diffraction condition is satisfied in the photopolymer 412, the phases of the light incident on the diffraction grating when reflected at each diffraction grating are consistent, so strong diffracted light is generated in the direction of -θ relative to the diffraction grating. That is, if the light ray L11 at an angle of φ+θ relative to the Y axis is incident on the photopolymer 412, the light ray L12 at an angle of φ-θ relative to the Y axis is emitted as the first-order diffracted light, and the light ray L13 at an angle of φ+θ relative to the Y axis is emitted (transmitted) as the 0th-order diffracted light (light that is not diffracted). In addition, the angle between the light ray L12 and the light ray L13 is 2θ.

[0056] Regarding the incident light that deviates from the Bragg diffraction condition in the light beam L11, the reflection phase of the light from each layer of the diffraction grating deviates, the light intensity of the 1st-order diffracted light (light beam L12) decreases, and the light intensity (transmitted light) of the 0th-order diffracted light (light beam L13) increases.

[0057] Figure 2 (c) shows the light intensity of the first-order diffracted light (light L12) in the incident light (light L11) relative to the photopolymer 412. At the incident angle θ that satisfies the Bragg diffraction condition, the light intensity of the first-order diffracted light becomes maximum, and the light intensity of the first-order diffracted light decreases as it deviates from θ. If the light intensity of the first-order diffracted light decreases, the light intensity of the 0th-order diffracted light increases. The intensity characteristics of the first-order diffracted light vary depending on the wavelength of the incident light (light L12), the refractive index of the photopolymer 412, and the thickness of the photopolymer 412.

[0058] exist Figure 2 In (c), the dotted line shows the light intensity of the first-order diffracted light when the thickness of the photopolymer 412 is t, and the solid line shows the light intensity of the first-order diffracted light when the thickness of the photopolymer 412 is 2×t. Figure 2 As shown in (c), as the thickness of the photopolymer 412 increases, the angular characteristics of the first-order diffracted light with respect to the incident angle to the Bragg diffraction grating become more sensitive, and the drop in the first-order diffracted light due to the deviation from the incident angle that causes Bragg diffraction increases.

[0059] (Operation of the hologram manufacturing device)

[0060] Next, the operation of the hologram manufacturing apparatus when manufacturing the replica hologram 42 will be described.

[0061] like Figure 1 As shown, the laser light L1 as a parallel light is reflected by the half mirror 3 and enters the master hologram 41. The laser light L1 incident on the master hologram 41 passes through the transparent substrate 411 and is refracted based on Snell's law, thereby changing the direction of the light. At this time, the refractive indexes of the transparent substrate 411, the photopolymer 412, and the protective film 413 are substantially the same, so the directions of the light in the transparent substrate 411, the photopolymer 412, and the protective film 413 become substantially the same.

[0062] like Figure 2As shown in (a), the diffraction grating based on the refractive index distribution formed in the photopolymer 412 is formed at an angle of φ relative to the Y-axis. Therefore, the laser light L1 is incident on the photopolymer 412 at an angle of φ+θ relative to the Y-axis. That is, the laser light L1 is incident at an angle of θ relative to the diffraction grating. If the laser light L1 is incident at an angle of θ relative to the diffraction grating, the Bragg diffraction condition in the photopolymer 412 is satisfied, so the first-order diffraction light (light L11) is generated in the direction of -θ relative to the diffraction grating, and the zero-order diffraction light (light L12) is generated in the direction of θ relative to the diffraction grating. That is, two light rays, light rays L11 and L12, are emitted from the master hologram 41.

[0063] When the light emitted from the master hologram 41 is incident on the replica hologram 42, refraction based on Snell's law occurs again. The refractive index of the replica hologram 42 is the same as that of the master hologram 41, so the light direction in the replica hologram 42 becomes the same as that in the master hologram 41. That is, the light ray L11 is incident on the replica hologram 42 at an angle of φ+θ relative to the Y-axis, and the light ray L12 is incident on the replica hologram 42 at an angle of φ-θ relative to the Y-axis. The angle formed by the light ray L11 and the light ray L12 is 2θ, and the intermediate direction between the light ray L11 and the light ray L12 is an angle of φ relative to the Y-axis. The light ray L11 and the light ray L12 have high coherence and are parallel light rays with an angle of 2θ between them, so the intensity of light, i.e., interference fringes, is generated. The condition for the mutual reinforcement of the intensity of the interference fringes is 2×n×d×sinθ=λ, so in the XY plane, at the azimuth of φ+90 degrees relative to the Y axis, the fringe spacing is spacing d. At the azimuth of φ relative to the Y axis, the optical path lengths of the light beams L11 and L12 are the same, so the light intensity distribution is the same. Similarly, the light intensity distribution does not change in the Z-axis direction. Therefore, the interference fringes (diffraction gratings), that is, the distribution of the intensity of the light, in the photopolymer 422 of the replica hologram 42 has the same shape as the diffraction grating g1 based on the refractive index distribution of the photopolymer 412 of the master hologram 41. In the photopolymer 422, the refractive index changes according to the light intensity. Therefore, when the ratio of the 0th order diffracted light and the 1st order diffracted light emitted from the replica hologram 42 becomes the same as the ratio of the 0th order diffracted light and the 1st order diffracted light in the master hologram 41, the light irradiation to the replica hologram 42 is stopped, thereby forming the diffraction grating g1 having the same refractive index distribution as the master hologram 41 in the replica hologram 42. At this time, in the replica hologram 42 produced when there is an error in the exposure time, the direction of the 1st order diffracted light relative to the 0th order diffracted light does not change, but an error occurs in the ratio of the 0th order diffracted light and the 1st order diffracted light. Here, in the replication of the replica hologram 42, the orientation of the 0th order diffracted light and the 1st order diffracted light based on the master hologram 41 does not change, that is, the pitch of the diffraction grating formed in the replica hologram 42 does not change. Therefore, in the replica hologram 42, even if there is an error in the exposure time, the orientation of the 1st order diffracted light does not change. The error in exposure time affects the magnitude of the refractive index difference of the diffraction grating formed in the photopolymer 422 of the replica hologram 42. If the refractive index difference increases, the first-order diffracted light relative to the 0th-order diffracted light increases, and conversely, if the refractive index difference decreases, the first-order diffracted light decreases.

[0064] Figure 3 It is a cross-sectional view showing a state in which the hologram recording material according to the first embodiment is being exposed.

[0065] like Figure 3As shown, when the laser light L1 is incident on the master hologram 41, the master hologram 41 emits the 0th order diffracted light (light L11) and the 1st order diffracted light (light L12). The light L11 and L12 generate a refractive index distribution in the photopolymer 422 of the replica hologram 42. When the light L11 is incident on the photopolymer 422, the 0th order diffracted light (light L111) and the 1st order diffracted light (light L112) are emitted from the replica hologram 42 by the Bragg diffraction of the replica hologram 42. In addition, when the light L12 is incident on the photopolymer 422, the 0th order diffracted light (light L121) and the 1st order diffracted light (light L122) are emitted from the replica hologram 42 by the Bragg diffraction of the replica hologram 42. As the exposure of the replica hologram 42 proceeds, the light intensity of the light L111, which is the transmitted light of the light L11, decreases, and the light intensity of the light L112, which is the 1st order diffracted light, increases. Similarly, the light intensity of the light L122 as the transmitted light of the light L12 decreases, and the light intensity of the light L121 as the first-order diffracted light increases. At this time, the light directions of the light L111 and L122 are the same, and the light directions of the light L112 and L121 are the same.

[0066] like Figure 3 As shown, the laser light L2 is Bragg diffracted in the master hologram 41 and the replica hologram 42, and four diffracted lights are generated similarly to the exposure light. The light beams L211 and L222 have the same light beam direction, and the light beams L212 and L221 have the same light beam direction.

[0067] For the laser light L2, if the amount of diffracted light is calculated in the same manner as for the laser light L1, when the light intensity of the 0th order diffracted light (light L21) of the master hologram 41 is set to 0.5+c, and the light intensity of the 1st order diffracted light (light L22) is set to 0.5-c, the light amount ratio of the 0th order diffracted light to the 1st order diffracted light in the exposure of the replica hologram 42 is (1-b): b. c is the amount of light amount reduction caused by the deviation from the Bragg diffraction condition of the Bragg diffraction grating formed in the master hologram 41 and the replica hologram 42 in the laser light L2. In the case of the Bragg diffraction condition, c is 0, and the greater the deviation of the incident angle from the Bragg diffraction condition, the greater c. That is, the greater the deviation of the incident angle from the Bragg diffraction condition, the less the 1st order diffracted light and the more the 0th order diffracted light. b is the 1st order diffracted light generated in the replica hologram 42 due to the formation of the Bragg diffraction grating in the photopolymer 422 by exposure. b is 0 at the start of exposure and increases as exposure progresses.

[0068] The light intensity of the light beam L211 emitted from the replica hologram 42 is (0.5+c)×(1-b), and the light intensity of the light beam L222 is (0.5-c)×b. If the light beams L211 and L222 are added together, the light intensity becomes Q=0.5+c-2×c×b. Thus, since the laser light L2 is incident at an angle that deviates from the incident angle that satisfies the Bragg diffraction conditions of the master hologram 41 and the replica hologram 42, c≠0. Therefore, as the exposure of the replica hologram 42 progresses, b increases, and thus the light intensity Q changes. That is, the degree of progress of the exposure of the replica hologram 42 can be measured. Therefore, the light quantity ratio of the first-order diffracted light and the zero-order diffracted light generated during the exposure of the replica hologram 42 due to the refractive index difference of the photopolymer 422 of the replica hologram 42 can be accurately measured. The same is true for the light beams L212 and L221 , and therefore the degree of progress of replicating the hologram 42 can also be measured using the light beams L212 and L221 .

[0069] like Figure 1 As shown, the emitted light from the replica hologram 42 passes through the opening 7 and is focused by the focusing lens 5. In addition, the laser light L3 is a light beam equivalent to the light beams L211 and L222, the laser light L4 is a light beam equivalent to the light beams L111 and L122, the laser light L5 is a light beam equivalent to the light beams L112 and L121, and the laser light L6 is a light beam equivalent to the light beams L212 and L221.

[0070] The light receiving sensor 6 is arranged on the focal plane of the condenser lens 5. Since the emitted light of the replica hologram 42 is parallel light, four light spots are formed on the light receiving surface of the light receiving sensor 6 (see Figure 4 (a)). The point lights S1 to S4 are point lights generated by the laser lights L3 to L6.

[0071] Figure 4 (b) is a graph showing the light intensity of the point light S1. Figure 4 As shown in (b), the light intensity of the point light S1 decreases as the exposure progresses. When the light amount of the point light S1 reaches a given light amount, the irradiation of the laser L1 is terminated, thereby obtaining a replica hologram 42 as the designed value. The light amount of the point light S1 at the end of the exposure can be obtained in advance through experiments. In addition, the exposure can be terminated by using the point light S4 instead of the point light S1.

[0072] After the exposure of the replica hologram 42 by the laser light L1 is completed, the master hologram 41 is removed from the hologram recording medium 4 and the replica hologram 42 is irradiated with ultraviolet light, thereby performing processing so that the photopolymer 422 is not further exposed to visible light.

[0073] According to the above structure, the hologram manufacturing device involved in the first embodiment includes: a master hologram 41, which is formed with a diffraction grating g1; a replica hologram 42, which is arranged close to the master hologram 41; a light source 1 (first light source), which emits a laser L1 (first laser) that satisfies the Bragg diffraction condition in the diffraction grating g1 for the master hologram 41 and the replica hologram 42; a light source 2 (second light source), which emits a laser L2 (second laser) that does not satisfy the Bragg diffraction condition in the diffraction grating g1 for the master hologram 41 and the replica hologram 42; and a light receiving sensor 6, which measures the lasers L3 and L6 (the laser L2 after passing through the master hologram 41 and the replica hologram 42), and ends the exposure of the replica hologram 42 based on the measurement results of the light receiving sensor 6.

[0074] According to this configuration, the laser light L2 is incident on the master hologram 41 and the replica hologram 42 so as not to satisfy the Bragg condition of the diffraction grating formed on the master hologram 41, and therefore the light intensities of the laser light L3 and L6, which are equivalent to the laser light L2 after passing through the master hologram 41 and the replica hologram 42, change according to the exposure time of the replica hologram 42. Thus, the degree of progress of the exposure of the replica hologram 42 can be measured, and thus the accuracy of the replica hologram can be improved.

[0075] In the first embodiment, the light source 2 irradiates the laser light L2 so that the laser light L2 is irradiated near the center of the laser light L1 (near the center of the master hologram 41 ).

[0076] Furthermore, by reducing the irradiation area of ​​the laser light L2, it is possible to measure the thickness t of the local photopolymer, thereby enabling the production of a replica hologram with higher accuracy.

[0077] Furthermore, by irradiating the laser light L2 to an unused area of ​​the replicated hologram 42 , the degree of progress of the exposure of the replicated hologram 42 can be managed.

[0078] Furthermore, in order to manage the progress of the exposure of the replica hologram 42, the Bragg diffraction condition in the photopolymer 412 of the master hologram 41 is used, but it is also possible to use the condition in the transmission diffraction based on the surface shape of the photopolymer 412. However, in the transmission diffraction based on the surface shape, high-order diffraction light is likely to appear, and thus errors in the replica hologram are likely to occur.

[0079] Furthermore, the refractive index distribution of the master hologram 41 is set to be uniform in the Z-axis direction, but refractive index distributions obtained by partially rotating the distribution around the Y-axis may be spliced.

[0080] (Second embodiment)

[0081] Figure 5Schematic diagram of a hologram manufacturing apparatus according to the second embodiment. In the first embodiment, the progress of exposure of the replica hologram 42 is measured by shifting the incident angle (angle ε) of the lasers L1 and L2 with respect to the master hologram 41. In contrast, in the second embodiment, the progress of exposure of the replica hologram 42 is measured by shifting the wavelengths of the lasers L1 and L2.

[0082] Specifically, the laser lights L1 and L2 have wavelengths different from each other.

[0083] The wavelength filter 8 (first wavelength filter) is a wavelength filter that reflects the laser light L1 and transmits the laser light L2. The wavelength filter 8 is formed of a dielectric multilayer film or the like, and has the following functions: through interference of light in the multilayer film, the light is reflected at a reflectivity of approximately 100% in a specific wavelength band, and the light is transmitted at a transmittance of approximately 100% in another wavelength band. The wavelength of the laser light L2 is different from the wavelength of the laser light L1, so the wavelength filter 8 reflects the laser light L1 at a high reflectivity and transmits the laser light L2 at a high transmittance.

[0084] The wavelength filter 9 (second wavelength filter) is disposed between the condenser lens 5 and the light receiving sensor 6 , and is a wavelength filter that transmits the laser light L2 of the light that has passed through the replica hologram 205 , and absorbs or reflects the laser light L1 .

[0085] (Operation of the hologram manufacturing device)

[0086] Next, the operation of the hologram manufacturing apparatus will be described. Incidentally, the exposure of the master hologram 41 and the replica hologram 42 is the same as that of the first embodiment. Specifically, the laser light L1 is reflected by the wavelength filter 8 and irradiated onto the master hologram 41. The exposure is performed by generating interference fringes in the replica hologram based on the 0th order diffracted light and the 1st order diffracted light generated by the Bragg diffraction in the master hologram 41, thereby forming a refractive index distribution.

[0087] In the second embodiment, the light beams of lasers L1 and L2 have the same azimuth, but the wavelengths of lasers L1 and L2 are different. Therefore, laser L2 does not satisfy the Bragg diffraction condition. Specifically, since the Bragg diffraction condition is expressed as 2×n×d×sin(θ)=λ, changing the incident angle θ is equivalent to changing the wavelength λ.

[0088] Here, the laser beams L3 and L4 emitted from the replica hologram 42 are parallel. Therefore, the laser beams L3 and L4 overlap. The wavelength filter 9 transmits the laser beam L3 (corresponding to the laser beam L2) and reflects the laser beam L4 (corresponding to the laser beam L1), so only the laser beam L3 is emitted from the wavelength filter 9. Thus, the progress of the exposure of the replica hologram 42 can be measured.

[0089] (Third embodiment)

[0090] Figure 6 Schematic diagram of a hologram manufacturing apparatus according to the third embodiment. In the first embodiment, the progress of the exposure of the replica hologram 42 is measured using the lasers L1 and L2. In contrast, in the third embodiment, the progress of the exposure of the replica hologram 42 is measured using only the laser L1 (exposure light) without using the laser L2 (reference light). Specifically, Figure 6 In, omitted Figure 1 Therefore, the light receiving sensor 6 (here, corresponding to the second sensor) measures the laser lights L4 and L5.

[0091] Figure 7 : is a graph showing the relationship between the diffraction efficiency when producing a replica hologram according to the third embodiment and the refractive index change Δn of the replica hologram. Specifically, Figure 7 4 is a graph showing the case where the ratio of the laser light L4 and L5 emitted from the master hologram 41 and the replica hologram 42 at the start of exposure is 4:1. Figure 7 In the figure, the variation of laser light L4 is depicted with white squares, and the variation of laser light L5 is depicted with black squares.

[0092] like Figure 7 As shown, as the exposure of the replica hologram 42 progresses (the refractive index change amount Δn increases), the diffraction efficiency of the lasers L4 and L5 changes. That is, by measuring only the laser L4 as the 0th-order diffracted light and the laser L5 as the 1st-order diffracted light (i.e., only the laser L1) when the laser L1 passes through the master hologram 41 and the replica hologram 42, the progress of the exposure of the replica hologram 42 can be measured.

[0093] (Fourth embodiment)

[0094] Figure 8 Schematic diagram of a hologram manufacturing apparatus according to the fourth embodiment. In the first embodiment, the progress of exposure of the replica hologram 42 is measured by staggering the incident angles (angle ε) of the lasers L1 and L2 with respect to the master hologram 41. In contrast, in the second embodiment, the progress of exposure of the replica hologram 42 is measured by making the lasers L1 and L2 incident on the master hologram 41 and the replica hologram 42 at different angles in the XZ plane.

[0095] like Figure 8 As shown, the light source 1 includes a laser light source 11 , an optical isolator 12 , a λ / 2 wavelength plate 13 , a condenser lens 14 , a pinhole 15 , and a collimator lens 16 .

[0096] The laser light source 11 is a light source for irradiating the laser light L1. The laser light source 11 emits the laser light L1 which is highly coherent and parallel light and is monochromatic linearly polarized light.

[0097] The optical isolator 12 suppresses return light from the λ / 2 wavelength plate 13 side toward the laser light source 11 .

[0098] The λ / 2 wavelength plate 13 controls the polarization direction of the incident laser light L1 , thereby controlling the laser light L1 to have a polarization direction optimal for exposure.

[0099] The condenser lens 14 condenses the laser light L1 incident via the λ / 2 wavelength plate 13 to the diffraction limit.

[0100] The pinhole 15 is disposed at the focal position of the condenser lens 14 to reduce the optical noise contained in the laser light L1. For example, the optical noise contained in the laser light L1 can be removed by setting the diameter of the pinhole 15 to be slightly larger than the diameter at which the spot light obtained by the condenser lens 14 has a light intensity of 1 / e2.

[0101] The collimator lens 16 is disposed so that the focal position becomes the pinhole 15 , and converts the transmitted light (laser light L1 ) into parallel light.

[0102] The light source 2 includes a laser light source 21 and a lens 22 .

[0103] The laser light source 21 is a light source for irradiating the laser light L2 . The laser light source 21 emits the laser light L2 , which is near-infrared light to which the photopolymer 422 is not sensitive.

[0104] The lens 22 converts the incident laser light L2 into parallel light.

[0105] Although not shown in the figure, the lasers L1 and L2 are incident on the master hologram 41 and the replica hologram 42 at different angles when viewed from above (when the master hologram 41 and the replica hologram are viewed from above). For example, when the laser L1 is incident on the master hologram 41 and the replica hologram 42 along the Z direction, the laser L2 is incident at an angle slightly deviated from the Z direction. In this case, the laser L2 is incident on the master hologram 41 and the replica hologram 42 so that the Bragg diffraction condition is satisfied. Therefore, when passing through the master hologram 41 and the replica hologram 42, the lasers L1 and L2 are transmitted in different directions. As a result, the light receiving sensor 6 can measure only the laser L7 which is the transmitted light of the laser L2.

[0106] Fig. 9This is a cross-sectional view of a replica hologram when a replica hologram is produced according to the fourth embodiment. For example, if the interference fringes of the replica hologram 42 for the laser light L2 are set to θ'', when λ=2×n×d×sinθ'' holds, the light (laser light L7) reflected by the laser light L2 at the interference fringes of the replica hologram 42 interferes with each other and reinforces each other. By making the laser light L2 incident on the master hologram 41 and the replica hologram 42 under this condition, the laser light L2 (L7) can be measured by the light receiving sensor 6.

[0107] Fig.10 : is a graph showing the relationship between the diffraction efficiency when producing a replica hologram according to the fourth embodiment and the refractive index change Δn of the replica hologram. Specifically, Fig.10 (a) is a graph showing the case where the ratio of the 0th order diffracted light to the 1st order diffracted light of the laser light L7 emitted from the master hologram 41 and the replica hologram 42 at the start of exposure is 1:1. Fig.10 (b) is a graph showing the case where the ratio of the 0th order diffracted light to the 1st order diffracted light of the laser light L7 at the start of exposure is 1:2. Fig.10 (c) is a graph showing the case where the ratio of the 0th order diffracted light to the 1st order diffracted light of the laser L7 at the start of exposure is 1:9. Fig.10 In each figure, the change of the 0th order diffraction light of the laser L7 is depicted by white squares, and the change of the 1st order diffraction light of the laser L7 is depicted by black squares.

[0108] like Fig.10 (a)~ Fig.10 As shown in (c), as the exposure of the replica hologram 42 progresses (the refractive index change Δn increases), the diffraction efficiency of the 0th order diffracted light and the 1st order diffracted light of the laser L7 changes. That is, the progress of the exposure of the replica hologram 42 can be measured by measuring the 0th order diffracted light and the 1st order diffracted light of the laser L7.

[0109] (Fifth embodiment)

[0110] (Overall structure of hologram manufacturing device)

[0111] Fig.11 as well as Fig.12 Schematic diagram of a hologram manufacturing device according to the fifth embodiment. Fig.11 is a side view of a hologram manufacturing apparatus according to a fifth embodiment, Fig.12 5 is a top view of a hologram manufacturing device according to the fifth embodiment. Fig.11 In the diagram, the width directions of the hologram recording body 4 are defined as the X direction and the Z direction, and the thickness direction (vertical direction) of the hologram recording body 4 is defined as the Y direction.

[0112] like Fig.11 as well as Fig.12 As shown, the hologram producing apparatus according to the fifth embodiment includes light sources 1 and 2 , a hologram recording medium 4 , and a light receiving sensor 6 .

[0113] The light source 1 (first light source) is a light source for irradiating laser light, and irradiates the laser light L1 for exposing the replica hologram 42 described later. The laser light L1 is a laser light having a long coherence distance (coherence length), and is a parallel light of uniform intensity distribution with a very high spatial coherence and a small wavefront aberration. The laser light L1 irradiates an area including at least the effective area of ​​the photopolymers 412 and 422 described later. In addition, it is preferred that the coherence distance of the laser light L1 is greater than or equal to the length obtained by adding the master hologram 41 and the replica hologram 42 described later.

[0114] Specifically, the light source 1 includes a laser light source 11 , an optical isolator 12 , a λ / 2 wavelength plate 13 , a condenser lens 14 , a pinhole 15 , and a collimator lens 16 .

[0115] The laser light source 11 is a light source for emitting laser light L1. The laser light source 11 emits the laser light L1 as monochromatic linearly polarized light which is highly coherent and parallel. The laser light source 11 may be formed of an LED (Light Emitting Diode) or the like.

[0116] The optical isolator 12 suppresses return light from the λ / 2 wavelength plate 13 side toward the laser light source 11 .

[0117] The λ / 2 wavelength plate 13 controls the polarization direction of the incident laser light L1 , thereby controlling the laser light L1 to have a polarization direction optimal for exposure.

[0118] The condenser lens 14 condenses the laser light L1 incident via the λ / 2 wavelength plate 13 to the diffraction limit.

[0119] The pinhole 15 is disposed at the focal position of the condenser lens 14 to reduce the optical noise contained in the laser light L1. For example, the diameter of the pinhole 15 can be set to be 1 / e smaller than the point light obtained by the condenser lens 14. 2 The diameter of the light intensity is slightly larger to remove the optical noise contained in the laser light L1.

[0120] The collimator lens 16 is disposed so that the focal position becomes the pinhole 15 , and converts the transmitted light (laser light L1 ) into parallel light.

[0121] The light source 2 (second light source) is a light source for irradiating laser light, and irradiates the laser light L2 for managing the exposure of the replica hologram 42. The laser light L2 is a laser light with a long coherence distance (coherence length) similar to the laser light L1, and is a parallel light with a uniform intensity distribution having a very high spatial coherence and a small wavefront aberration. The laser light L2 irradiates the approximate center of the effective area of ​​the master hologram 41 and the replica hologram 42.

[0122] Specifically, the light source 2 includes a laser light source 21 and a lens 22 .

[0123] The laser light source 21 is a light source for irradiating the laser light L2. The laser light source 21 emits the laser light L2, which is near-infrared light that is not sensitive to the photopolymer 422. The laser light source 21 may be composed of an LED or the like.

[0124] The lens 22 converts the incident laser light L2 into parallel light.

[0125] The light receiving sensor 6 is a light receiving sensor having a two-dimensional pixel structure. For example, the light receiving sensor 6 is a CCD camera, a CMOS camera, etc. Fig.12 In the figure, laser light L2 is irradiated from the lower side toward the upper side of the figure, and the details will be described later. Then, laser light L2 is reflected by the hologram recording body 4 (master hologram 41). The reflected laser light L2 is focused by the lens 61 and detected by the light receiving sensor 6.

[0126] (Structure of hologram recording body)

[0127] Fig.13 (a) is a cross-sectional view showing the structure of a hologram recording medium according to the fifth embodiment.

[0128] like Fig.11 as well as Fig.13 As shown in (a) of FIG. 8 , the hologram recording medium 4 is composed of a master hologram 41 and a replica hologram 42 . In the present embodiment, the master hologram 41 is irradiated with the laser light L1 , so that the same diffraction grating as that formed on the master hologram 41 is formed on the replica hologram 42 .

[0129] like Fig.11 as well as Fig.13 As shown in (a) of FIG. 1 , the master hologram 41 includes a transparent substrate 411 , a photopolymer 412 , and a protective film 413 . The transparent substrate 411 , the photopolymer 412 , and the protective film 413 are stacked.

[0130] The transparent substrate 411 is a flat plate with high transmittance, and for example, quartz, optical glass, etc. can be used. In addition, an anti-reflection film is formed on the upper surface of the transparent substrate 411 in the figure.

[0131] The photopolymer 412 is formed, for example, of an optical material whose refractive index changes when it is exposed to visible light. The amount of change in the refractive index of the photopolymer 412 is determined by the amount of energy of the light received by the photopolymer 412, that is, the product of the light intensity and time. In addition, the photopolymer 412 can stop the change in the refractive index by irradiating ultraviolet rays. In the photopolymer 412, a refractive index distribution (diffraction grating) is formed in advance using visible light with different light intensities, and then it is processed so that the refractive index distribution does not change due to ultraviolet irradiation. Thus, given interference fringes are formed in the photopolymer 412. In addition, the refractive index of the photopolymer 412 is approximately 1.5 to 1.6, and the amount of change in the refractive index based on visible light is approximately 0.01 to 0.1. In addition, the thickness t of the photopolymer 412 is formed to be between 1μm and 100μm. In addition, the thicker the thickness t of the photopolymer 412, the more the diffraction efficiency at the photopolymer 412 can be improved. In this case, the characteristics of the first-order diffracted light with respect to the incident angle to the photopolymer 412 also become sensitive, and the first-order diffracted light is greatly attenuated by a small change in the incident angle.

[0132] The protective film 413 is a thin transparent protective layer for protecting the photopolymer 412, and is formed of a material that is not easily damaged, such as thin glass with high transmittance. In addition, a reflection prevention film is formed on the upper side of the protective film 413. The thickness of the protective film 413 is at least thinner than the transparent substrate 411. In addition, it is preferred that the average refractive index of the transparent substrate 411 and the photopolymer 412 is close to the refractive index of the protective film 413.

[0133] The replica hologram 42 includes a transparent substrate 421, a photopolymer 422, and a protective film 423. The transparent substrate 421, the photopolymer 422, and the protective film 423 are stacked.

[0134] Transparent substrate 421, photopolymer 422 and protective film 423 are respectively the same as transparent substrate 411, photopolymer 412 and protective film 413. However, photopolymer 422 has the same thickness t as photopolymer 412, has no refractive index distribution in the initial state, and is not irradiated with ultraviolet rays.

[0135] like Fig.11 As shown, the replica hologram 42 is arranged closely in a state rotated 180° with respect to the master hologram 41 so as to be parallel to each other.

[0136] As described above, a refractive index distribution (diffraction grating) is pre-formed in the photopolymer 412. The refractive index distribution of the photopolymer 412 has a distribution in the XY cross section and is the same in the Z-axis direction. That is, the refractive index distribution of the photopolymer 412 is the same in the XY cross section at any position of the Z-axis. The refractive index distribution in the photopolymer 412 is periodically formed with a high refractive index portion and a low refractive index portion. In the photopolymer 412, a so-called diffraction grating based on a refractive index distribution with thickness, namely a Bragg diffraction grating, is formed. The diffraction grating is formed with a spacing of d and an angle φ relative to the Y-axis in the XY plane. Therefore, in the X-axis direction, the spacing of the diffraction grating is d / cos (φ).

[0137] Fig.13 (b) shows Fig.13 (a) is a graph showing the refractive index of the cross section AA and the cross section BB of the photopolymer 412. Fig.13 As shown in (b), the refractive index of section AA and section BB changes in a sinusoidal wave shape. The average refractive index is n, and the refractive index change is Δn. The only difference in the refractive index change between section AA and section BB is that the waveforms are laterally offset. If a highly interfering laser is incident on the main hologram 41 having such a periodic refractive index distribution, light diffraction called Bragg diffraction is generated. As a characteristic of Bragg diffraction, strong diffracted light in a specific direction, namely, first-order diffracted light, is generated. In addition, with respect to the emitted light based on Bragg diffraction, 0th-order diffraction and first-order light constitute the majority, and almost no higher-order diffraction light is generated.

[0138] When the average refractive index in the photopolymer 412 is n, the pitch of the diffraction grating is d, the incident angle to the diffraction grating is θ, and the wavelength of the incident light is λ, the Bragg diffraction condition in the photopolymer 412 becomes 2×n×d×sin(θ)=λ. In addition, regarding the direction of the light, the angle changes based on Snell's law occur due to refraction in the photopolymer 412. That is, if the direction relative to the Y axis in the air is α, then since the refractive index of the photopolymer 412 is n, for the direction β in the photopolymer 412, sin(α)=n×sin(β).

[0139] If the Bragg diffraction condition is satisfied in the photopolymer 412, the phases of the light incident on the diffraction grating when reflected at each diffraction grating are consistent, so strong diffracted light is generated in the direction of -θ relative to the diffraction grating. That is, if the laser light L1 at an angle of φ+θ relative to the Y axis is incident on the photopolymer 412, the light L11 at an angle of φ-θ relative to the Y axis is emitted as the first-order diffracted light, and the light L12 at an angle of φ+θ relative to the Y axis is emitted (transmitted) as the 0th-order diffracted light (light that is not diffracted). In addition, the angle between the light L11 and the light L12 is 2θ.

[0140] (Operation of the hologram manufacturing device)

[0141] Next, the operation of the hologram manufacturing apparatus when manufacturing the replica hologram 42 will be described.

[0142] like Fig.11 As shown, the laser light L1 as a parallel light is reflected by the half mirror 3 and enters the master hologram 41. The laser light L1 incident on the master hologram 41 passes through the transparent substrate 411 and is refracted based on Snell's law, thereby changing the direction of the light. At this time, the refractive indexes of the transparent substrate 411, the photopolymer 412, and the protective film 413 are substantially the same, so the directions of the light in the transparent substrate 411, the photopolymer 412, and the protective film 413 become substantially the same.

[0143] like Fig.13 As shown in (a), the diffraction grating based on the refractive index distribution formed in the photopolymer 412 is formed at an angle of φ relative to the Y-axis. Therefore, the laser light L1 is incident on the photopolymer 412 at an angle of φ+θ relative to the Y-axis. That is, the laser light L1 is incident at an angle of θ relative to the diffraction grating. If the laser light L1 is incident at an angle of θ relative to the diffraction grating, the Bragg diffraction condition in the photopolymer 412 is satisfied, so the first-order diffraction light (light L11) is generated in the direction of -θ relative to the diffraction grating, and the zero-order diffraction light (light L12) is generated in the direction of θ relative to the diffraction grating. That is, two light rays, light rays L11 and L12, are emitted from the master hologram 41.

[0144] When the light emitted from the master hologram 41 is incident on the replica hologram 42, refraction based on Snell's law occurs again. The refractive index of the replica hologram 42 is the same as that of the master hologram 41, so the light direction in the replica hologram 42 is the same as that in the master hologram 41. That is, the light ray L11 is incident on the replica hologram 42 at an angle of φ+θ relative to the Y-axis, and the light ray L12 is incident on the replica hologram 42 at an angle of φ-θ relative to the Y-axis. The angle formed by the light ray L11 and the light ray L12 is 2θ, and the intermediate direction between the light ray L11 and the light ray L12 is an angle of φ relative to the Y-axis. The light ray L11 and the light ray L12 have high coherence and are parallel light rays with an angle of 2θ between them, so the intensity of light, i.e., interference fringes, is generated. The condition for the mutual reinforcement of the intensity of the interference fringes is 2×n×d×sinθ=λ, so in the XY plane, at the position of φ+90 degrees relative to the Y axis, the fringe spacing is the spacing d. At the position of φ relative to the Y axis, the optical path lengths of the light beams L11 and L12 are the same, so the light intensity distribution is the same. Similarly, the light intensity distribution does not change in the Z axis direction. Therefore, the interference fringes (diffraction gratings), that is, the distribution of the intensity of the light, in the photopolymer 422 of the replica hologram 42 has the same shape as the diffraction grating g1 formed by the refractive index distribution of the photopolymer 412 of the master hologram 41. In the photopolymer 422, the refractive index changes according to the light intensity. Therefore, when the ratio of the 0th order diffracted light and the 1st order diffracted light emitted from the replica hologram 42 becomes the same as the ratio of the 0th order diffracted light and the 1st order diffracted light in the master hologram 41, the light irradiation to the replica hologram 42 is stopped, thereby forming the diffraction grating g1 having the same refractive index distribution as the master hologram 41 in the replica hologram 42. At this time, for the replica hologram 42 produced when there is an error in the exposure time, the direction of the 1st order diffracted light relative to the 0th order diffracted light does not change, but an error occurs in the ratio of the 0th order diffracted light and the 1st order diffracted light. Here, in the replication of the replica hologram 42, the orientation of the 0th order diffracted light and the 1st order diffracted light based on the master hologram 41 does not change, that is, the pitch of the diffraction grating formed in the replica hologram 42 does not change, so in the replica hologram 42, even if there is an error in the exposure time, the orientation of the 1st order diffracted light does not change. The error in exposure time affects the magnitude of the refractive index difference of the diffraction grating formed in the photopolymer 422 of the replica hologram 42. If the refractive index difference increases, the first-order diffracted light relative to the 0th-order diffracted light increases, and conversely, if the refractive index difference decreases, the first-order diffracted light decreases.

[0145] However, the amount of change in the refractive index of the photopolymer 422 caused by the exposure time is determined by the temperature and the photosensitivity of each manufacturing batch. In addition, the 1st-order diffraction light relative to the 0th-order diffraction light changes according to the thickness of the photopolymer 422. That is, the thicker the thickness, the more the amount of light passing through the grating of the refractive index distribution increases, so the 1st-order diffraction light becomes more. Therefore, if the exposure amount is simply determined by time, the ratio of the 0th-order diffraction light to the 1st-order diffraction light based on the photopolymer 422 becomes different from the design value. Therefore, it is conceivable to measure the 1st-order diffraction light of the replica hologram 42, but since the master hologram 41 and the replica hologram 42 are arranged to overlap, it is difficult to measure the 1st-order diffraction light of the replica hologram 42 during exposure.

[0146] Fig.14 1 is a perspective view showing the incident angle of the laser light L2 to the replica hologram according to the fifth embodiment. Although not shown in the figure, the laser light L1 and L2 are incident on the master hologram 41 and the replica hologram 42 at different angles when viewed from above (when the master hologram 41 and the replica hologram are viewed from above). That is, when viewed from above, the incident angle (second incident angle) of the laser light L2 is different from the incident angle (first incident angle) of the laser light L1.

[0147] Fig.15 2 is a cross-sectional view showing the state of the exposure of the replica hologram according to the fifth embodiment. Fig.15 As shown, when the laser light L2 is irradiated to the refractive index distribution (diffraction grating) of the replica hologram 42 so as to satisfy the Bragg diffraction condition, the laser light L3 (the laser light L2 reflected by the replica hologram 42) which is a part of the laser light L2 is generated toward the upper left side of the figure. The laser light L3 is generated symmetrically with respect to the normal direction (Y' direction) of the refractive index distribution of the replica hologram 42.

[0148] Fig.16 FIG. 1 is a top view showing the state of the exposure of the replica hologram according to the fifth embodiment. Fig.16 As shown, when the incident angle of the laser L2 relative to the refractive index distribution is set to θ', the laser L2 has high coherence, so if 2×n×d×sinθ'=λ holds, the reflected light at the refractive index distribution interferes with each other and strengthens each other. When this formula holds, the laser L2 is incident on the replica hologram 42 to generate the laser L3. The light receiving sensor 6 is configured to detect the laser L3.

[0149] Regarding the laser light L2, a part of it is reflected by the master hologram 41 and the replica hologram 42. Specifically, the laser light L2 includes the laser light L4 (not shown) reflected by the refractive index distribution of the master hologram 41 and the laser light L3 reflected by the refractive index distribution of the replica hologram 42. Among them, the refractive index distribution of the master hologram 41 does not change, so the laser light L4 is constant. Moreover, as the exposure of the replica hologram 42 proceeds, the light amount of the laser light L3 increases. Therefore, by ending the irradiation of the laser light L2 when the laser light L3 reaches a given light amount, the replica hologram 42 as designed can be obtained. The light amount of the laser light L3 at the end of exposure can be obtained in advance by experiments.

[0150] After the exposure of the replica hologram 42 is completed, the master hologram 41 is removed from the hologram recording medium 4 and the replica hologram 42 is irradiated with ultraviolet light, thereby performing processing so that the photopolymer 422 is not further exposed to visible light.

[0151] According to the above structure, the hologram manufacturing device involved in the fifth embodiment comprises: a main hologram 41, which is formed with a diffraction grating; a replica hologram 42, which is arranged close to the main hologram 41; a light source 1 (a first light source), which emits a laser L1 (a first laser) for exposing the replica hologram 42; a light source 2 (a second light source), which emits a laser L2 (a second laser) at an incident angle different from that of the laser L1 with respect to the replica hologram 42; and a light receiving sensor 6, which measures the laser L3 (a third laser) after the laser L2 is reflected by the replica hologram 42, and ends the exposure of the replica hologram 42 according to the measurement result of the light receiving sensor 6.

[0152] According to this structure, the laser beams L1 and L2 are emitted at different incident angles with respect to the replica hologram 42, so that only the laser beam L2 can be reflected by the diffraction grating (refractive index distribution) of the replica hologram 42, and only the laser beam L2 (laser beam L3) can be measured by the light receiving sensor 6. Thus, the progress of the exposure of the replica hologram 42 can be measured by measuring the laser beam L3, so that the accuracy of the replica hologram can be improved.

[0153] In addition, the wavelengths of the laser beams L1 and L2 may be the same as or different from each other.

[0154] The light source 2 is a laser light source that emits the laser light L2 as parallel light. However, the laser light L2 may be emitted by collimating the light emitted from the laser light source 21 composed of an LED using the lens 22 .

[0155] Furthermore, the light source 2 irradiates the laser light L2 so that the laser light L2 is irradiated to the vicinity of the center of the laser light L1 (the vicinity of the center of the master hologram 41 ), but the irradiation position of the laser light L2 is not limited thereto.

[0156] In the present embodiment, the case where the measuring optical system including the light source 2 and the light receiving sensor 6 is one set is described as an example, but a plurality of measuring optical systems may be arranged to measure the replica hologram 42 at a plurality of locations.

[0157] (Sixth embodiment)

[0158] Figure 17 to Figure 19 Schematic diagram of a hologram manufacturing device according to the sixth embodiment. Fig.17 is a side view of a hologram manufacturing apparatus according to a sixth embodiment, Fig.18 is a top view of a hologram manufacturing apparatus according to a sixth embodiment. Fig.19 It is a perspective view of the hologram manufacturing apparatus according to the sixth embodiment. In the fifth embodiment, the replica hologram 42 is placed in the air and exposed, but in the sixth embodiment, the replica hologram 42 is immersed in liquid and exposed.

[0159] like Figure 17 to Figure 19 As shown, the hologram recording medium 4 (master hologram 41 and replica hologram 42) is placed in a water tank 7 filled with water. The inner wall of the water tank 7 is formed of a material with low light reflectivity, so that light reflection caused by the inner wall is reduced.

[0160] Furthermore, a coupling prism 8 is disposed on the upper part of the hologram recording body 4. The coupling prism 8 is made of a material having a refractive index substantially the same as that of water. The bottom surface of the coupling prism 8 is disposed in water, and the side surfaces 81 to 83 are disposed in air. The side surfaces 82 and 83 of the coupling prism 8 are disposed to face each other.

[0161] Here, the laser light L1 is transmitted through the side surface 81 of the coupling prism 8 and irradiated onto the hologram recording medium 4. Therefore, even when the laser light L1 is transmitted from the coupling prism 8 into the water, the refraction of light based on Snell's law does not occur. Therefore, the laser light L1 can be irradiated onto the hologram recording medium 4 without being refracted.

[0162] Furthermore, the laser light L2 is transmitted through the side surface 82 of the coupling prism 8 and irradiated onto the hologram recorder 4, and is emitted via the side surface 83. The laser light L2 can also be irradiated onto the hologram recorder 4 without being refracted, similarly to the laser light L1. Furthermore, the laser light L3 which is the reflected light of the laser light L2 can also be detected by the light receiving sensor 6 without being affected by refraction or total reflection.

[0163] like Fig.19As shown in FIG. 1 , the coupling prism 8 has a prism 8a having a side surface 81 at the center, and a prism 8b having a side surface 82 and a prism 8c having a side surface 83 at both ends in the X direction. By setting the coupling prism 8 in such a shape, a prism corresponding to both the exposure light and the measurement light can be integrally manufactured. Thus, the light utilization efficiency of the exposure light / measurement light can be improved by improving the operability in the device and improving the accuracy of the components.

[0164] In the sixth embodiment, similarly to the fifth embodiment, the laser light L2 is emitted to the replica hologram 42 so as to satisfy the Bragg diffraction condition. The light amount of the reflected light (laser light L3) of the laser light L2 at this time is measured by the light receiving sensor 6. By ending the irradiation of the laser light L2 when the laser light L3 reaches a given light amount, a replica hologram 42 as designed can be obtained. The light amount of the laser light L3 at the end of exposure is obtained in advance by experiments. In this way, the accuracy of the replica hologram can be improved.

[0165] Furthermore, the master hologram 41 and the replica hologram 42 are immersed in the liquid by being arranged in the water tank 7 filled with water. Therefore, it is possible to suppress the refraction of the laser light L1 based on Snell's law when it is incident on the transparent substrates 411 and 421. Thus, the incident angle of the laser light L1 with respect to the master hologram 41 and the replica hologram 42 can be increased.

[0166] Furthermore, since the light receiving sensor 6 is disposed outside the water tank 7, the equipment can be simplified.

[0167] Although water is filled in the water tank 7, liquid such as oil having the same refractive index as the transparent substrates 411 and 421 of the master hologram 41 and the replica hologram 42 may be filled in. Thus, the refractive index difference between the liquid filled in the water tank 7 and the transparent substrates 411 and 421 disappears, thereby eliminating interface reflection.

[0168] Industrial Applicability

[0169] The hologram manufacturing device disclosed in the present invention can be applied to hologram optical element systems such as projectors, head-mounted displays, and head-up displays.

[0170] Description of Reference Numerals

[0171] (First to Fourth Embodiments)

[0172] 1, 2 light sources (1st light source, 2nd light source)

[0173] 3 Half mirror

[0174] 4 Hologram Recording

[0175] 41 Main Hologram

[0176] 42 Copy hologram

[0177] 412, 422 Photopolymer

[0178] 5. Condenser lens

[0179] 6 Light receiving sensors (1st sensor, 2nd sensor)

[0180] 8, 9 wavelength filters (1st wavelength filter, 2nd wavelength filter)

[0181] L1, L2 laser (1st laser, 2nd laser)

[0182] (Fifth to Sixth Embodiments)

[0183] 1, 2 light sources (1st light source, 2nd light source)

[0184] 4 Hologram Recording

[0185] 41 Main Hologram

[0186] 42 Copy hologram

[0187] 412, 422 Photopolymer

[0188] 6 Light sensor

[0189] 7 sink

[0190] 8 Coupling prism

[0191] L1~L3 laser (1st to 3rd laser).

Claims

1. A hologram manufacturing device, comprising: a master hologram formed with a diffraction grating; a replica hologram disposed proximate to the master hologram; a first light source for emitting a first laser light satisfying a Bragg diffraction condition in the diffraction grating for the master hologram and the replica hologram; a second light source that emits a second laser beam that does not satisfy a Bragg diffraction condition in the diffraction grating with respect to the master hologram and the replica hologram; and The first sensor measures the second laser light after passing through the master hologram and the replica hologram. Based on the measurement result of the first sensor, exposure of the replica hologram using the first laser light is terminated.

2. The hologram manufacturing device according to claim 1, wherein: The first laser beam and the second laser beam have different incident angles with respect to the master hologram.

3. The hologram manufacturing device according to claim 2, wherein: The first laser beam and the second laser beam are different from each other in the incident angle in a side view.

4. The hologram manufacturing device according to claim 2, wherein: The first laser beam and the second laser beam are different from each other in the incident angle in a plan view.

5. The hologram manufacturing device according to claim 3, wherein: The hologram producing apparatus further includes a half mirror for combining the first laser beam and the second laser beam.

6. The hologram manufacturing device according to claim 1, wherein: The first laser beam and the second laser beam are different from each other in wavelength.

7. The hologram manufacturing device according to claim 6, wherein: The hologram producing apparatus further includes a first wavelength filter for combining the first laser beam and the second laser beam.

8. The hologram manufacturing device according to claim 7, wherein: The hologram producing apparatus further includes a second wavelength filter disposed between the master hologram and the replica hologram and the first sensor, and preventing the first laser beam from passing therethrough.

9. A hologram manufacturing device, comprising: a master hologram formed with a diffraction grating; a replica hologram disposed proximate to the master hologram; a first light source for emitting a first laser beam satisfying a Bragg diffraction condition in the diffraction grating with respect to the master hologram and the replica hologram; and a second sensor for measuring the first laser beam after passing through the master hologram and the replica hologram; Based on the measurement result of the second sensor, the exposure of the replica hologram using the first laser beam is terminated.

10. A method for producing a hologram, comprising: A step of placing a master hologram having a diffraction grating formed thereon and a replica hologram in close proximity; A step of emitting a first laser beam satisfying a Bragg diffraction condition in the diffraction grating and emitting a second laser beam not satisfying a Bragg diffraction condition in the diffraction grating for the master hologram and the replica hologram; and The step of measuring the second laser light after passing through the master hologram and the replica hologram, and ending the exposure of the replica hologram with the first laser light based on the result of the measurement.

11. A hologram manufacturing device, comprising: a master hologram formed with a diffraction grating; a replica hologram disposed proximate to the master hologram; a first light source for emitting a first laser beam for exposing the replica hologram at a first incident angle to the replica hologram; a second light source that emits a second laser beam at a second incident angle different from the first incident angle to the replica hologram; and A sensor measures the second laser light reflected by the replica hologram, Based on the measurement result of the sensor, the exposure of the replica hologram using the first laser beam is terminated.

12. The hologram manufacturing device according to claim 11, wherein: The first laser beam and the second laser beam are different from each other in wavelength.

13. The hologram manufacturing apparatus according to claim 11, wherein: The second laser beam is irradiated onto the replica hologram so as to satisfy the Bragg diffraction condition of the diffraction grating formed on the master hologram.

14. The hologram manufacturing apparatus according to claim 11, wherein: The hologram manufacturing apparatus further includes a water tank for immersing the master hologram and the replica hologram in liquid.

15. The hologram manufacturing apparatus according to claim 14, wherein: The hologram manufacturing apparatus further includes a coupling prism disposed above the master hologram and the replica hologram.

16. The hologram manufacturing apparatus according to claim 14, wherein: The sensor is disposed outside the water tank.

17. A method for producing a hologram, comprising: A step of placing a master hologram having a diffraction grating formed thereon and a replica hologram in close proximity; a step of emitting a first laser beam for exposing the replica hologram at a first incident angle to the replica hologram, and emitting a second laser beam at a second incident angle different from the first incident angle to the replica hologram; and The second laser beam reflected by the replica hologram is measured, and based on the result of the measurement, the step of exposing the replica hologram using the first laser beam is terminated.

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