Exposure device, manufacturing method of first holographic optical element, manufacturing method of exposure device, and second holographic optical element

Abstract

To provide an exposure device capable of preventing a decrease in the diffraction efficiency of the first holographic optical element being manufactured.SOLUTION: An exposure device in an embodiment includes: a laser light source 1 that emits laser light L2, L5; and a detector that detects the exposure condition on a first volume hologram 9 to be exposed by the laser light L2 and L5. The laser light L2, L5 is diffracted towards the detector by a second volume hologram 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an exposure device, a method for manufacturing a first holographic optical element, a method for manufacturing an exposure device, and a second holographic optical element. [Background technology]

[0002] Conventionally, exposure devices for manufacturing hologram optical elements (first hologram optical elements) have been known. For example, in Patent Document 1, a predetermined pre-exposure process is performed on an area in a recording layer of a hologram recording medium (first hologram optical element) where an interference pattern is to be recorded. Next, a reference beam and an information beam (object beam) are caused to intersect in the pre-exposed recording area to form interference fringes, and the interference pattern (interference fringes) is recorded on the hologram recording medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-147012 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the first hologram optical element is exposed with the object light and the reference light, the interference fringes recorded on the hologram optical element change due to factors such as vibrations of the optical system of the exposure device, air turbulence, and instability of the object light and reference light irradiated from the light source, etc. As a result, the diffraction efficiency of the manufactured first hologram optical element decreases.

[0005] Therefore, an object of the present disclosure is to provide an exposure device, a method for manufacturing a first hologram optical element, a method for manufacturing an exposure device, and a second hologram optical element that suppress a decrease in the diffraction efficiency of the first hologram optical element to be manufactured. [Means for solving the problem]

[0006] In order to achieve the above object, an apparatus for manufacturing a hologram optical element according to one embodiment of the present disclosure includes a light source that irradiates first light and second light, and a detector that detects the exposure state of a first hologram optical element exposed by the first light and the second light, and the first light and the second light are diffracted by the second hologram optical element toward the detector. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to prevent a decrease in the diffraction efficiency of the manufactured first hologram optical element. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a side view of the exposure device when exposing the first volume hologram according to the embodiment. [Figure 2] Enlarged view of part A in Figure 1. [Figure 3] 5A and 5B are diagrams for explaining control of the phase of laser light L5 by the control device according to the embodiment. [Figure 4] 6A and 6B are diagrams for explaining control of the incident angle of laser light L5 by the control device according to the embodiment. [Figure 5] FIG. 4 is a side view of the exposure device when exposing the second volume hologram according to the embodiment. [Figure 6] Enlarged view of part B of Figure 1. [Figure 7] FIG. 10 is a side view of an exposure device when exposing a second volume hologram according to a modified example. [Figure 8] FIG. 10 is a side view of an exposure device when exposing a second volume hologram according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses. In the following description, the same parts will be designated by the same reference numerals, and detailed description will be omitted as appropriate.

[0010] The volume holograms (first volume hologram 9 and second volume hologram 10) used in this disclosure differ from two-dimensional diffraction gratings with fine periodic irregularities arranged on the surface, in that they record a three-dimensional sinusoidal refractive index distribution within a volume. By controlling the direction and period of this sinusoidal wave and the amplitude of the refractive index difference, it is possible to control the light distribution of the volume hologram. For the sake of convenience, this disclosure describes the refractive index distribution recorded in the volume hologram as being sinusoidal, but the refractive index distribution recorded in the volume hologram is not limited to being sinusoidal and may have other shapes or be complex.

[0011] (Embodiment) (Overall configuration of exposure device) Fig. 1 is a side view of an exposure device when exposing a first volume hologram according to an embodiment. Fig. 2 is an enlarged view of part A in Fig. 1. In Fig. 1, the irradiation direction of laser light L3 is the X direction, the direction of laser light L2 (object light) is the Y direction, and the direction perpendicular to the X and Y directions (the depth direction of the paper) is the Z direction.

[0012] As shown in Fig. 1, the exposure apparatus according to the embodiment includes a laser light source 1, a condenser lens 2, a collimator lens 3, a branching mirror 4, a mirror 5, a half mirror 6, a light-shielding plate 7, a spatial light modulator 8 (correction unit), a first volume hologram 9 (first holographic optical element), a second volume hologram 10 (second holographic optical element), a camera 11 (detector), and a control device 12. As will be described in detail later, the first volume hologram 9 is a volume hologram exposed (manufactured) by this exposure apparatus. The second volume hologram 10 is a volume hologram used to measure interference fringes recorded in the first volume hologram 9 when the first volume hologram 9 is exposed.

[0013] The laser light source 1 is a light source that irradiates the condenser lens 2 with laser light L1. The laser light source 1 is a highly coherent laser light source. Therefore, after the laser light L1 is split into laser light L2 and laser light L3 by the splitting mirror 4 (described later), even if the laser light L2 and laser light L3 are separated by the same optical path length, they can still cause optical interference with each other. Furthermore, the laser light L1 has linear polarization characteristics, and if the polarization ratio is insufficient, the polarization direction may be controlled by inserting a wave plate or polarizing plate.

[0014] The condenser lens 2 is a lens that condenses the laser light L1 emitted by the laser light source 1. After being condensed by the condenser lens 2, the laser light L1 becomes expanded light (see Figure 1). The laser light L1 has a distribution that is generally called a Gaussian distribution, where the amount of light is high in the center and decreases toward the periphery. Since it is desirable for the light required for interference to have a nearly constant intensity distribution within the surface, the expanded central light is used, and other light is blocked and not used. Unnecessary light is omitted in Figure 1, and only the light beam that is used is shown.

[0015] The collimating lens 3 is a lens that converts the laser light L1 diffused by the collecting lens 2 into parallel light. Specifically, the collimating lens 3 is disposed so that its focal length f matches the distance to the focal point of the laser light L1 collected by the collecting lens 2.

[0016] The branching mirror 4 branches the laser light L1, which has been converted into parallel light by the collimating lens 3, into two light beams (laser light L2 (object light, corresponding to the first light) and laser light L3 (reference light, corresponding to the second light)). For example, the branching mirror 4 is composed of a polarizing prism splitter or the like, and reflects the linearly polarized light of the laser light L1 in a first polarization direction (laser light L2, for example, S-polarized light) and transmits the linearly polarized light of the second polarization direction (laser light L3, for example, P-polarized light).

[0017] The mirror 5 reflects the laser light L2 reflected by the branching mirror 4. Specifically, the mirror 5 is formed in the shape of the product in which the first volume hologram 9 is used. If the product is planar, the mirror 5 is formed in a planar shape, as shown in FIG. 1. The laser light L2 is reflected by the mirror 5 and irradiated onto the first volume hologram 9. The mirror 5 may also have a curved surface. For example, if the first volume hologram 9 is used as a light guide plate that projects an image onto the windshield of a vehicle, the mirror 5 is formed in a curved shape to match the shape of the windshield of the vehicle.

[0018] The half mirror 6 splits the laser light L3 that has passed through the splitting mirror 4 into two beams (laser light L4 and laser light L5). The half mirror 6 reflects a part of the laser light L3 as laser light L4 and transmits the remaining part of the laser light L3 as laser light L5.

[0019] The light blocking plate 7 is made of a material that blocks incident light, and blocks the laser light L4 reflected by the half mirror 6.

[0020] The spatial light modulator 8 reflects the laser light L5 that has passed through the half mirror 6. The spatial light modulator (SLM) 8 is a device that changes (modulates) light by electrically controlling the spatial distribution (amplitude, phase, angle, etc.) of the light. The spatial light modulator 8 controls the phase of the reflected laser light L5 and the angle of incidence with respect to the first volume hologram 9, based on a control signal received from the control device 12.

[0021] The first volume hologram 9 is a volume hologram exposed (manufactured) by this exposure apparatus.

[0022] 2, the first volume hologram 9 includes a photopolymer 9a and a substrate 9b. The photopolymer 9a is made of, for example, an optical material whose refractive index changes when it receives visible light. The substrate 9b is a flat plate with high transmittance, and is made of, for example, quartz or optical glass.

[0023] In this embodiment, when exposing the first volume hologram 9, the first volume hologram 9 is irradiated with laser light L2 (object light) and laser light L5 (reference light), thereby forming interference fringes (refractive index distribution) in the photopolymer 9a. That is, the first volume hologram 9 is exposed by being irradiated with laser light L2 (object light) and laser light L5 (reference light). Thereafter, the first volume hologram 9 is irradiated with ultraviolet light, thereby preventing the formed interference fringes from changing. In this way, the first volume hologram 9 is manufactured.

[0024] The second volume hologram 10 is disposed between the first volume hologram 9 and the camera 11. During exposure of the first volume hologram 9, the second volume hologram 10 diffracts the incident laser beams L2 and L5 toward the camera 11 as laser beams L6 and L7. The angle between the laser beams L5 and L6 is preferably 1 degree or less. Note that in FIG. 2, the second volume hologram 10 is disposed between the first volume hologram 9 and the camera 11, but this is not a limitation and it may be disposed in a region where the laser beams L6 and L7 overlap. Specifically, it may be disposed in the dashed-line region S shown in FIG. 2.

[0025] 2, the second volume hologram 10 is positioned so that the laser beams L2 and L5 incident on an area that does not affect the performance of the first volume hologram 9 (for example, an end of the first volume hologram 9) are incident on the second volume hologram 10. In this case, the laser beams L2 and L4 diffracted by the second volume hologram 10 may be only a few percent. Furthermore, the position (positions in the X, Y, and Z directions) and angle (angles formed with the X, Y, and Z directions) of the second volume hologram 10 are adjusted by a drive mechanism (not shown) so that the number of interference fringes in the image captured by the camera 11 is minimized.

[0026] The camera 11 receives the laser beams L6 and L7 reflected by the second volume hologram 10. The camera 11 outputs the imaging results of the laser beams L6 and L7 to the control device 12 while the first volume hologram 9 is being exposed.

[0027] The control device 12 is, for example, a computer equipped with a CPU, ROM, RAM, etc. The control device 12 outputs a control signal to the spatial light modulator 8 based on the image capture result of the camera 11. The control device 12 controls the spatial light modulator 8 to perform a correction process for correcting the phase and incident angle of the laser light L5 (reference light) incident on the first volume hologram 9.

[0028] (Regarding control device correction processing) During exposure of the first volume hologram 9, the control device 12 controls the spatial light modulator 8 based on the imaging result of the camera 11 to correct the phase and incident angle of the laser light L5 (reference light).

[0029] Specifically, the second volume hologram 10 reflects the incident laser beams L2 and L5 as laser beams L6 and L7 toward the camera 11. The camera 11 captures the incident laser beams L6 and L7. Since the angle between the laser beams L6 and L7 is less than 1 degree, the angles of incidence of the laser beams L6 and L7 with respect to the camera 11 are approximately the same, and the image captured by the camera 11 is less likely to have stripes or the like due to the brightness and darkness of the laser beams. As a result, the image captured by the camera 11 is a simple bright and dark image. The control device 12 uses the image captured by the camera 11 at the start of exposure of the first volume hologram 9 as a reference image and controls the spatial light modulator 8 so that the image captured by the camera 11 during exposure of the first volume hologram 9 does not change from the reference image.

[0030] Fig. 3 is a diagram for explaining the control of the phase of laser light L5 by the control device according to the embodiment. Specifically, Fig. 3(a) is a reference image, Fig. 3(b) is a graph showing the light intensity of X1-X1' in Fig. 3(a), Fig. 3(c) is an image taken by camera 11 during exposure of the first volume hologram, and Fig. 3(d) is a graph showing the light intensity of X2-X2' in Fig. 3(c).

[0031] As shown in FIGS. 3(a) and 3(b), at the start of exposure of the first volume hologram, the light intensity of the image (reference image) captured by the camera 11 is generally low. In contrast, as shown in FIGS. 3(c) and 3(d), during exposure of the first volume hologram, the light intensity of the image captured by the camera 11 is generally high. In this case, the control device 12 determines that the phase of the laser light L5 has changed and controls the spatial light modulator 8 to control the phase of the laser light L5. That is, the control device 12 controls the phase of the laser light L5 so that the light intensity at the start of exposure of the first volume hologram is maintained. Because light has wave properties, when the phase of the laser light L5 (L7) changes, the laser light L5 (L7) and the laser light L2 (L6) reinforce or cancel each other out, resulting in an overall change in the light intensity of the image captured by the camera 11. Therefore, when the light intensity of the image captured by the camera 11 changes, the control device 12 determines that the phase of the laser light L5 has changed. Note that a specific method for controlling the spatial light modulator 8 when the phase of the laser light L5 changes (how to change the phase of the laser light L5) may be set in advance.

[0032] Fig. 4 is a diagram for explaining the control of the incident angle of laser light L5 by the control device according to the embodiment. Specifically, Fig. 4(a) is a reference image, Fig. 4(b) is a graph showing the light intensity of X3-X3' in Fig. 4(a), Fig. 4(c) is an image taken by camera 11 during exposure of the first volume hologram, and Fig. 4(d) is a graph showing the light intensity of X4-X4' in Fig. 4(c).

[0033] As shown in FIGS. 4(a) and 4(b), at the start of exposure of the first volume hologram, the light intensity of the image (reference image) captured by the camera 11 is high in the center and low at the edges. That is, in FIGS. 4(a) and 4(b), there is one interference fringe in the reference image. In contrast, as shown in FIGS. 4(c) and 4(d), during exposure of the first volume hologram, there are four high-intensity regions and five low-intensity regions in the image captured by the camera 11. That is, in FIGS. 4(a) and 4(b), there are four interference fringes in the image captured by the camera 11. In this case, the control device 12 determines that the incident angle of the laser beam L5 with respect to the first volume hologram 9 has changed, and controls the spatial light modulator 8 to control the incident angle of the laser beam L5. As the incident angle between the object beam and the reference beam increases, the number of interference fringes formed in the first volume hologram 9 increases. As the incident angle between the object beam and the reference beam decreases, the number of interference fringes formed in the first volume hologram 9 decreases. Therefore, when the number of interference fringes in the image captured by the camera 11 changes, the control device 12 determines that there has been a change in the incident angle of the laser light L5 with respect to the first volume hologram 9. Note that a specific method for controlling the spatial light modulator 8 when the incident angle of the laser light L5 has changed (how to change the incident angle of the laser light L5) may be set in advance.

[0034] (Method for manufacturing the second volume hologram) FIG. 5 is a side view of an exposure device when exposing a second volume hologram according to an embodiment. FIG. 6 is an enlarged view of portion B of FIG. 5. Compared to FIG. 1, mirrors 13 and 14 are arranged in place of the light-shielding plate 7 in FIG. 5. The second volume hologram 10 is exposed (manufactured, created) using this exposure device. The second volume hologram 10 is exposed (manufactured, created) using the same exposure device as the exposure device that exposes (manufactures) the first volume hologram 9.

[0035] 5, the mirrors 13 and 14 are mirrors that reflect the laser light L4 reflected by the half mirror 6. After being reflected by the mirrors 13 and 14, the laser light L4 enters the second volume hologram 10.

[0036] 6, the second volume hologram 10 includes a photopolymer 10a and a substrate 10b, similar to the first volume hologram 9. The photopolymer 10a is made of, for example, an optical material whose refractive index changes when it receives visible light.

[0037] In this embodiment, when exposing the second volume hologram 10, the second volume hologram 10 is irradiated with laser light L2 (object light) and laser light L4 and L5 (reference light), thereby forming interference fringes (refractive index distribution) in the photopolymer 9a. That is, the second volume hologram 10 is exposed by being irradiated with three laser beams, laser light L2, L4, and L5. Thereafter, the second volume hologram 10 is irradiated with ultraviolet light, thereby preventing the formed interference fringes from changing. In this way, the second volume hologram 10 is manufactured (created).

[0038] The incidence angle and diffraction angle of the laser light during use of a volume hologram are determined by the irradiation angle of the laser light during exposure. For this reason, if a different exposure device is used to expose (manufacture) the second volume hologram, the usage conditions (such as the incidence angle and diffraction angle of the laser light) will not match. For this reason, by exposing (manufacturing) the second volume hologram 10 using the exposure device used to expose (manufacture) the first volume hologram 9, the second volume hologram 10 for irradiating the laser light L2 (L6) and L5 (L7) on the camera 11 can be manufactured.

[0039] When the second volume hologram 10 is exposed (manufactured, created), the spatial light modulator 8, the camera 11, and the control device 12 do not need to be driven.

[0040] (Variation 1) Fig. 7 is a side view of an exposure device when exposing a second volume hologram according to a modified example. In Fig. 7, compared to Fig. 5, mirror 15 is arranged instead of mirrors 13 and 14.

[0041] Specifically, the mirror 15, like the mirrors 13 and 14, is a mirror that reflects the laser light L4 reflected by the half mirror 6. After being reflected by the mirror 15, the laser light L4 enters the second volume hologram 10.

[0042] In Figure 7, when the second volume hologram 10 is exposed, the laser light L4 is incident on the second volume hologram 10 at an angle different from that in Figure 5. Even with this configuration, it is possible to expose (manufacture) the second volume hologram 10. That is, as long as the diffracted light of the laser light L2 and L5 (corresponding to the laser light L6 and L7 in Figure 2) can be captured by the camera 11 when the first volume hologram 9 is exposed, the incident angle of the laser light L4 with respect to the second volume hologram 10 may be set at any angle.

[0043] (Variation 2) 8 is a side view of an exposure device when exposing a second volume hologram according to a modified example. In FIG. 8, the positions of the mirror 5 and the spatial light modulator 8 are reversed compared to FIG. 1.

[0044] Specifically, the laser light L3 (reference light) reflected by the branching mirror 4 is reflected by the spatial light modulator 8 and is irradiated onto the second volume hologram .

[0045] Furthermore, the laser light L2 (object light) transmitted by the splitting mirror 4 is split by the half mirror 6. A portion (laser light L8) of the laser light L2 split by the half mirror 6 is reflected by the mirror 5 and is irradiated onto the second volume hologram 10. The remaining portion (laser light L9) of the laser light L2 split by the half mirror 6 is reflected by the mirrors 13 and 14 and is irradiated onto the second volume hologram 10. That is, in FIG. 8, the second volume hologram 10 is exposed (manufactured) by one reference light (laser light L3) and two object light (laser light L8, L9).

[0046] An exposure device for exposing the second volume hologram may be configured as shown in Fig. 8. When an exposure device for exposing the second volume hologram is configured, the positions of the mirror 5 and the spatial light modulator 8 are also interchanged in the exposure device for exposing the first volume hologram.

[0047] (Other embodiments) In the above embodiment, the correction unit is configured using the spatial light modulator 8, but this is not limiting. For example, the correction unit may be configured using at least one of a piezo stage and a deformable mirror.

[0048] In the above embodiment, the first volume hologram 9 is exposed to two beams of light, the laser beam L2 (object beam) and the laser beam (reference beam), but it may be exposed to three or more beams of light, or to any number of beams of light. In this case, the second volume hologram 10 may be exposed to one beam of light equal to the number of beams exposing the first volume hologram 9 plus one.

[0049] In the above embodiment, the detector is the camera 11, but the present invention is not limited to this. For example, the detector may be any detector that can detect the laser light L2 (object light) and the laser light L5 (reference light) diffracted by the second volume hologram 10.

[0050] Furthermore, in the above embodiment, the first volume hologram 9 and the second volume hologram 10 do not have to be provided in the exposure device from the beginning. The first volume hologram 9 only needs to be provided at the time of exposure (manufacturing) of the first volume hologram 9, and the second volume hologram 10 only needs to be provided at the time of exposure (manufacturing) of the first volume hologram 9 and the second volume hologram 10. [Industrial Applicability]

[0051] The exposure apparatus of the present disclosure can be used to expose (manufacture) a volume hologram. [Explanation of symbols]

[0052] 1. Laser light source 2. Condenser lens 3 Collimating Lens 3 4-way mirror 5. Mirror 6 Half mirror 7. Shade 8 Spatial light modulator (correction unit) 9. First volume hologram (first holographic optical element) 10 Second volume hologram (second hologram optical element) 11 Camera (detector) 12 Control device L2, L6 laser light (first light) L5, L7 laser light (second light) L4 laser light (third light)

Claims

1. a light source that emits the first light and the second light; a detector that detects an exposure state of a first hologram optical element exposed by the first light and the second light, The first light and the second light are diffracted by a second holographic optical element toward the detector.

2. the first hologram optical element; The exposure apparatus according to claim 1 , further comprising the second holographic optical element.

3. 2. The exposure apparatus according to claim 1, wherein the angle formed by the first light and the second light diffracted by the second holographic optical element is 1 degree or less.

4. The exposure apparatus according to claim 1 , further comprising a correction unit that corrects the first light and the second light based on a detection result of the detector.

5. 2. The exposure apparatus according to claim 1, further comprising a half mirror that splits either the first light or the second light.

6. A light source irradiating a first light and a second light; a step of exposing a first holographic optical element to the first light and the second light; a second holographic optical element diffracting the first light and the second light; a detector detecting the first light and the second light diffracted by the second hologram.

7. The method for manufacturing a first holographic optical element according to claim 6 , wherein the first light and the second light are corrected based on a detection result of the detector.

8. 2. A method for manufacturing an exposure apparatus according to claim 1, comprising: A method for manufacturing an exposure device, wherein the second holographic optical element is manufactured using the exposure device.

9. 9. A method for manufacturing an exposure apparatus according to claim 8, comprising: the light source emits a third light in addition to the first light and the second light, The second hologram optical element is formed by exposure to the first light, the second light, and the third light.

10. In an exposure apparatus including a light source that irradiates first light and second light, and a detector that detects an exposure state of a first hologram optical element that is exposed by the first light and the second light, a second hologram optical element that diffracts the first light and the second light toward the detector, The second holographic optical element diffracts the first light and the second light toward the detector.

11. 11. The second hologram optical element according to claim 10, wherein the angle formed by the first light and the second light diffracted by the second hologram optical element is 1 degree or less.

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