JP6700106B2 - Method for manufacturing optical element and method for manufacturing reflective aerial imaging element - Google Patents

Description

  The present invention relates to a method of manufacturing a reflective aerial imaging element that forms a real image of a projection object in the air, and a method of manufacturing an optical element used in the reflective aerial imaging element.

  A conventional reflection type aerial image forming element is disclosed in Japanese Patent Application Laid-Open No. 2004-242242. This reflective aerial imaging element is formed by stacking two flat plate-shaped optical elements on top of each other, and the optical element is formed by bonding a plurality of transparent base materials with an adhesive. The base material has a reflective surface formed by depositing aluminum or the like on the boundary surface with the adhesive. The reflecting surface is formed parallel to the thickness direction of the optical element, and is arranged at a predetermined cycle in a direction perpendicular to the thickness direction. Two optical elements are adhered so that their reflection surfaces are orthogonal to each other to form a reflective aerial imaging element.

  The projection target is arranged below the reflection type aerial image forming element having the above-mentioned configuration, and light is emitted toward the projection target. Part of the light reflected by the projection target enters the lower optical element from the lower surface, is reflected by the reflecting surface, and then enters the upper optical element. The light reflected by the reflecting surface of the upper optical element is emitted from the upper surface of the reflective aerial image forming element, and the real image of the object is projected in the air at the position of the object and the surface object with respect to the reflective aerial image forming element. It is imaged. As a result, the image of the projection object is displayed in a state of floating in the air. That is, an aerial image of the projection target is displayed.

  The manufacturing process of the optical element having the above structure includes a reflecting surface forming process, a laminating process, a fixing process and a cutting process. In the reflecting surface forming step, a reflecting surface is formed by vapor deposition of aluminum on one surface of a substrate made of a thin transparent glass plate in the plate thickness direction. In the laminating step, an appropriate amount of adhesive is applied on the central portion of the reflecting surface, and a plurality of substrates are laminated in the plate thickness direction to form a laminated body. In the fixing step, for example, pressure is applied from the stacking direction of the laminate to spread the adhesive between the substrates, and the adhesive is cured to form a fixed laminate. In the cutting step, the fixed laminated body is cut at a predetermined cycle in a direction perpendicular to the reflecting surface. Thereby, an optical element is formed.

  Patent Document 2 discloses a method of manufacturing an optical element similar to that of Patent Document 1. In this method of manufacturing an optical element, a substrate made of a glass plate forming a laminated body is formed by plate drawing. For example, the substrate is formed by causing molten glass to overflow from both sides of a gutter-shaped member having a V-shaped cross section, and letting the overflowed molten glass merge downward at the lower end of the gutter-shaped member to draw it downward (drawing direction). Then, the stacked body is formed by stacking the substrates so that the drawing directions of the adjacent substrates are orthogonal to each other. As a result, it is possible to prevent accumulation of uneven thickness in the laminated body and make the reflecting surfaces parallel to each other.

Japanese Unexamined Patent Publication No. 2012-155345 (page 6, page 7, FIGS. 4 and 5) JP-A-2015-90387 (pages 10 to 12, FIGS. 1 to 4)

  In the optical element manufacturing methods of Patent Documents 1 and 2, the substrate is often formed with a concave surface due to warpage. For this reason, generally, the warpage of the substrates in the stack is corrected by applying pressure to the stack from the stacking direction. However, when a large force is applied to the laminate to correct the warp of the substrate, fine high-frequency unevenness is formed on the reflective surface of the substrate. Therefore, when an aerial image is formed using an optical element formed of a laminated body, high-frequency image unevenness occurs and the image quality of the aerial image deteriorates. Therefore, there is a problem that the yield of the optical element decreases.

  It is an object of the present invention to provide a method of manufacturing an optical element and a method of manufacturing a reflective aerial imaging element that can improve the yield.

In order to achieve the above object, the present invention is a method of manufacturing a light-transmissive optical element in which reflective surfaces parallel to the thickness direction are arranged in parallel at a predetermined cycle,
A laminating step of forming a laminated body by laminating a plurality of thin plate-shaped transparent substrates having the reflection surface formed on one surface perpendicular to the thickness direction in the thickness direction,
A fixing step of fixing the laminated body by applying pressure from the plate thickness direction,
A cutting step of forming a plurality of the optical elements by cutting the fixed laminated body at a predetermined cycle in the plate thickness direction,
In the stacking step, a plurality of substrate pairs including a pair of the substrates combined so as to face each other with concave surfaces due to warpage are provided in the stack.

  Further, in the present invention, in the method of manufacturing an optical element having the above-mentioned configuration, it is preferable that the substrate pair is formed by 57% or more of the total number of the substrates forming the laminated body.

  Further, in the present invention, in the method for manufacturing an optical element having the above-mentioned configuration, it is preferable that the substrate pair is formed by 71% or more of the total number of the substrates forming the laminate.

  In the present invention, in the method for manufacturing an optical element having the above-mentioned configuration, the substrate is formed in a rectangular shape, and in the laminating step, the pair of substrates forming the substrate pair are arranged in two directions parallel to two orthogonal sides. It is preferable that the first direction with the larger amount of warp be oriented in the same direction.

  Further, in the present invention, in the method for manufacturing an optical element having the above configuration, it is preferable that all the substrate pairs are arranged with the first direction facing the same direction in the laminating step.

  Further, in the present invention, in the method for manufacturing an optical element having the above-mentioned configuration, it is preferable that, in the cutting step, the fixed laminated body is cut in a direction orthogonal to the first direction.

  Further, the present invention is the method for manufacturing an optical element having the above-mentioned configuration, in the laminating step, one of the two ends of the one of the substrate pairs in the first direction, which has a smaller thickness, and the other one of the substrates, It is preferable that one of the two ends in one direction, which has a large thickness, faces one another.

  Further, the present invention is the method for manufacturing an optical element having the above-mentioned configuration, wherein the substrate is a glass plate formed into a plate shape by drawing molten glass in a predetermined drawing direction, and in the laminating step, the substrate pair is used. It is preferable to rotate one of the substrates forming the above with respect to the other by rotating it by 180° about the drawing direction as an axis.

  Further, according to the present invention, in the method for manufacturing an optical element having the above-mentioned configuration, it is preferable that the fixed laminated body is cut in the drawing direction in the cutting step.

  Further, the present invention is a method of manufacturing a reflective aerial imaging element comprising a pair of the optical elements manufactured by the method of manufacturing an optical element having the above-mentioned configuration, wherein the pair of optical elements have a thickness such that the reflecting surfaces are orthogonal to each other. It is characterized by including an optical element arranging step of arranging the optical elements so as to overlap each other in the direction.

  According to the present invention, in the stacking step, the stacked body is provided with a plurality of substrate pairs each including a pair of substrates which are combined so that the concave surfaces due to the warp are arranged to face each other. Thereby, the warp of the substrate can be corrected with a small pressure in the fixing step. Therefore, it is possible to suppress the deterioration of the image quality of the aerial image due to the unevenness of the high frequency on the reflecting surface, and to improve the yield of the optical element and the reflective aerial imaging element.

1 is a perspective view showing an aerial image display device including a reflective aerial image forming element according to a first embodiment of the present invention. The perspective view which expanded the principal part of FIG. The top view which shows the reflection type aerial imaging element of 1st Embodiment of this invention. 1 is a perspective view showing an optical element used in a reflective aerial image forming element according to a first embodiment of the present invention. The side view which expanded the adhesion part between the base materials of the optical element of the reflection type aerial imaging element of 1st Embodiment of this invention. The figure which shows the manufacturing process of the reflection type aerial imaging element of 1st Embodiment of this invention. FIG. 3 is a perspective view showing a reflective surface forming step of the reflective aerial imaging element according to the first embodiment of the present invention. 1 is a perspective view showing an example of a method of forming a substrate used in a manufacturing process of a reflective aerial imaging element according to a first embodiment of the present invention. The figure which shows an example of the three-dimensional shape of the board|substrate used for formation of the reflection type aerial imaging element of 1st Embodiment of this invention. The figure which shows the curvature amount of the board|substrate of FIG. 9 in the A direction. The figure which shows the amount of curvatures of the board|substrate of FIG. 9 in the B direction. The side view which shows the spacer formation process of the reflection type aerial imaging element of 1st Embodiment of this invention. 1 is a perspective view showing a substrate after a spacer forming step of a reflective aerial imaging element according to a first embodiment of the present invention is completed. The side view which shows the lamination process of the reflection type aerial imaging element of 1st Embodiment of this invention. Front sectional view showing a fixing step of a reflective aerial image-forming element according to a first embodiment of the present invention. 1 is a perspective view showing a fixing block when a fixing process of a reflective aerial imaging element according to a first embodiment of the present invention is completed. FIG. 3 is a perspective view for explaining formation of a pair of substrates in a stacking process of the second embodiment of the present invention. Schematic side view showing the configuration of the laminate of the optical element of Example 1. Schematic side view showing the configuration of the laminated body of the optical element of Example 2. Schematic side view showing the configuration of the laminated body of the optical element of Example 3. Schematic side view showing the structure of the laminated body of the optical element of Example 5. Schematic side view showing the configuration of the laminated body of the optical element of Example 6. Schematic side view showing the configuration of the laminated body of the optical element of Comparative Example 1. The figure which shows the image quality evaluation result by the chart image of the optical element of the comparative example 1. The figure which shows the image quality evaluation result by the chart image of the optical element of the comparative example 2.

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an aerial image display device including a reflective aerial image forming element according to the first embodiment. FIG. 2 shows an enlarged perspective view of the main part of FIG. FIG. 3 shows a plan view of the reflective aerial imaging element. The X direction, the Y direction, and the Z direction indicate the width direction, the thickness direction, and the depth direction of the reflective aerial imaging element 10, respectively. Further, in FIG. 2, an arrow Q indicates an optical path.

  The aerial image display device 100 includes a light source 20 and a reflective aerial image forming element 10. The reflective aerial imaging element 10 is formed by arranging two flat plate-shaped optical elements 1 side by side in the thickness direction (Y direction). The planar shape of the optical element 1 is formed into a substantially square shape having a side length of, for example, about 200 mm. The optical element 1 is formed of a light transmissive material, and the reflecting surfaces 4 parallel to the thickness direction (Y direction) are arranged in parallel at a predetermined cycle T (for example, 0.53 mm).

  The light source 20 is arranged on the lower optical element 1 side (lower than the reinforcing plate 5 in FIG. 1 ). The light source 20 is composed of, for example, an LED and emits white illumination light L. The light source 20 emits the illumination light L to the projection object OB so that the reflected light of the projection object OB enters the incident surface 18 at an incident angle of about 45°. The light source 20 may be formed of a CCFL (Cold Cathode Fluorescent Lamp).

  FIG. 4 shows a perspective view of the optical element 1. The optical element 1 is formed by adhering a plurality of transparent base materials 2 having reflective surfaces 4 formed on both surfaces with an adhesive 3 (see FIG. 5) provided on the reflective surfaces 4. The base material 2 is formed of transparent resin such as acrylic resin or glass. The adhesive 3 is made of a two-component mixed type adhesive in which a main agent made of, for example, an epoxy resin or an acrylic resin is mixed with a hardening agent made of, for example, a polyamide resin.

  The reflecting surface 4 is formed on the base material 2 by sputtering or vapor deposition of aluminum or silver, for example.

  FIG. 5 shows a side view in which an adhesive portion between adjacent base materials 2 is enlarged. A plurality of dot-shaped spacers 15 are arranged in a matrix form in plan view on the reflecting surface 4 between the adjacent base materials 2. The spacer 15 is made of, for example, an ultraviolet curable resin, has a height E (a protrusion amount in a direction perpendicular to the reflecting surface 4) within a range of 20 μm±1 μm, and has a predetermined pitch P in two orthogonal directions (this embodiment). 1 mm). Thereby, the film thickness of the layers of each adhesive 3 can be made uniform, and the plurality of reflecting surfaces 4 can be maintained parallel to each other.

  In the reflective aerial imaging element 10, the two optical elements 1 are arranged in the thickness direction so that the direction in which the reflecting surface 4 of the lower optical element 1 extends and the direction in which the reflecting surface 4 of the upper optical element 1 extend are orthogonal to each other. It is formed by overlapping in the (Y direction). The lower surface of the lower optical element 1 becomes an incident surface 18 (see FIG. 2) on which light is incident, and the upper surface of the upper optical element 1 becomes an emission surface 19 (see FIG. 2) at which light is emitted.

  A transparent reinforcing plate 5 (see FIG. 1) that covers the optical element 1 is provided on one end surface (lower end surface in FIG. 1) of the optical element 1 in the juxtaposed direction (Y direction). The reinforcing plate 5 is made of the same material as the base material 2, such as glass. The strength of the reflective aerial imaging element 10 can be improved by the reinforcing plate 5. The reinforcing plates 5 may be provided on both end surfaces (the upper end surface and the lower end surface in FIG. 1) of the optical element 1 in the juxtaposed direction. Further, the reinforcing plate 5 may be omitted from the reflective aerial imaging element 10.

  In the aerial image display device 100 having the above configuration, the projection object OB (see FIG. 2) of the two-dimensional image is arranged on the lower optical element 1 side (below the reinforcing plate 5 in FIG. 1) and the light source 20 is turned on. To do. The illumination light L emitted from the light source 20 is reflected by the projection object OB. As shown by an arrow Q (see FIG. 2), a part of the reflected light of the projection object OB is incident on the lower optical element 1 through the incident surface 18, and is reflected by the reflective surface 4 of the lower optical element 1 and then upward. Is incident on the optical element 1.

  The light reflected by the reflecting surface 4 of the upper optical element 1 is emitted upward from the exit surface 19 of the upper surface of the reflective aerial imaging element 10, and the object OB and the surface of the object are symmetric with respect to the projection type aerial imaging element 10. A real image (aerial image FI) of the projection object OB is formed in the air at the position. As a result, the aerial image FI of the projection object OB is displayed in a state of floating in the air.

  At this time, as shown in FIG. 3, when the reflecting surface 4 of the optical element 1 is inclined by 45° with respect to the user's line-of-sight direction EL by projecting it on a plane parallel to the incident surface 18, the visibility of the aerial image FI is improved. I can do the best.

  Further, if the projected object OB is, for example, information about a product or the like, it is possible to advertise the product or the like by the aerial image FI. In addition, a touch panel of a device used at a medical site or a construction site may be displayed as the aerial image FI. As a result, it is possible to prevent the device from being contaminated. Further, the reflective aerial imaging element 10 may be mounted on a game machine or the like.

  The projection object OB is not limited to a two-dimensional image, and may be a three-dimensional object. The projected object OB may be an image displayed on a display device such as a liquid crystal panel. At this time, the light source 20 may be omitted and a light source built in the display device may be used.

  FIG. 6 is a diagram showing a manufacturing process of the reflective aerial imaging element 10. The manufacturing process of the reflective aerial image forming device 10 includes a reflecting surface forming process, a spacer forming process, a laminating process, a fixing process, a cutting process, a polishing process, an optical element arranging process, and a reinforcing plate attaching process.

  In the reflective surface forming step, as shown in FIG. 7, the reflective surface 4 is formed on both surfaces of the substrate 21 having a substantially square planar shape by sputtering or vapor deposition of aluminum or silver. The substrate 21 is made of a thin glass plate. The material of the glass plate is not particularly limited, but for example, borosilicate glass can be used. In this embodiment, the reflecting surface 4 is formed of aluminum having a thickness (film thickness) of 200 nm. The reflective surface 4 may be formed on only one surface of the substrate 21.

  The substrate 21 of this embodiment is a rectangle of 200 mm×200 mm, and has a plate thickness of about 0.53 mm. The plate thickness of the substrate 21 is preferably 0.6 mm or less. Thereby, a good aerial image FI can be obtained.

  FIG. 8 is a diagram showing an example of a method of forming the substrate 21. The substrate 21 made of a glass plate is formed by plate drawing, such as an overflow down draw method. In the overflow down draw method, a molten glass MG (glass melt) is injected through a pipe 51 into a substantially wedge-shaped trough member 50 having an upper surface 50a opened and a lower portion having a V-shaped cross section.

  Next, the molten glass MG overflows from both sides of the upper surface 50a of the gutter-shaped member 50. The molten glass MG joins at the lower end of the gutter-shaped member 50, and is drawn downward (drawing direction DF) to form a plate shape. At this time, the surface of the glass is not in contact with other than air and is formed only by the surface tension, so that a smooth surface can be obtained.

  Next, the plate-like glass that flows downward and is gradually cooled and then cut at a predetermined cutting line CT. Thereby, the substrate 21 is obtained. The substrate 21 may be formed by a forming method other than the plate-drawing method (for example, a float method or a roll-out method).

  Since the substrate 21 has a thin plate shape (for example, a thickness of 0.53 mm), warpage occurs. Further, depending on the accuracy of the parallelism between the two surfaces of the substrate 21 that face each other in the plate thickness direction, the thickness on the two opposite sides may differ. In the laminating step described below, the warp and thickness of the substrate 21 are measured by a warp amount measuring device and a plate thickness measuring device (both not shown), and the substrate 21 is paired.

  FIG. 9 is a diagram showing an example of a three-dimensional shape of the substrate 21 made of glass formed by plate drawing. In the figure, two directions parallel to the two orthogonal sides of the substrate 21 are defined as the A direction and the B direction, and are arranged parallel to the orthogonal A axis and B axis. The substrate 21 is a rectangle of 200 mm×200 mm, and the drawing direction DF is the B direction. The unit of the A axis and the B axis is mm, and the unit of the C axis orthogonal to the A axis and the B axis is μm.

  Further, FIG. 10 shows the warp amount (the warp amount in the A direction) of the cross section parallel to the A-C plane of FIG. 9. In the figure, B0 is the center in the B direction (B=0), B1 is 70 mm (B=-70) from the center in the B direction to one side, and B2 is 70 mm (B=70) from the center in the B direction to the other side. is there.

  FIG. 11 shows a warp amount (a warp amount in the B direction) of a cross section parallel to the B-C plane of FIG. In the figure, A0 is the center of the A direction (A=0), A1 is 70 mm (A=-70) from the center of the A direction, and A2 is 70 mm (A=70) from the center of the A direction to the other. is there.

  As shown in FIGS. 9 to 11, the substrate 21 formed by plate drawing is less likely to warp in the drawing direction DF (B direction) and is more likely to warp in the direction (A direction) orthogonal to the drawing direction DF.

  In this embodiment, the warp amount at the center position (B=0) in the B direction of the substrate 21 is the warp amount Wa in the A direction, and the warp amount at the center position in the A direction (A=0) is the warp amount Wb in the B direction. There is. The maximum value of each warp amount at a plurality of positions in the B direction of the substrate 21 may be the warp amount in the A direction, and the maximum value of each warp amount at a plurality of positions in the A direction may be the warp amount in the B direction. Further, an average value of warp amounts at a plurality of positions in the B direction of the substrate 21 may be set as a warp amount in the A direction, and an average value of warp amounts at a plurality of positions in the A direction may be set as a warp amount in the B direction.

  The warp of the substrate 21 in the A direction and the B direction is usually such that one of the same faces in the plate thickness direction is convex. Therefore, as shown in FIG. 7, the substrate 21 is formed with a concave surface 21a and a convex surface 21b due to warpage. When the substrate 21 warps in a saddle shape, one surface of the substrate 21 in the plate thickness direction is convex in the A direction and concave in the B direction. Therefore, the concave surface 21a and the convex surface 21b are determined based on the larger absolute value of the warp amount in the A direction and the warp amount in the B direction.

  FIG. 12 is a side view showing the spacer forming step. The spacer forming step is performed by the spacer forming portion 70 that moves in two directions (one of which is indicated by an arrow F) substantially parallel to the reflecting surface 4 of the substrate 21. The spacer forming portion 70 has an inkjet head 71, an ultraviolet light source 72, and a distance measuring sensor 73.

  The distance measuring sensor 73 measures the distance to the reflecting surface 4. The inkjet head 71 ejects the ink 71 a made of an ultraviolet curable resin toward the substrate 21. Before the ejection of the inkjet head 71, the distance measuring sensor 73 measures the distance to the reflecting surface 4 at the measurement start position (for example, the end of the substrate 21), and this distance is used as the reference distance. Then, the distance between the planned dropping position of the ink 71a on the reflecting surface 4 and the distance measuring sensor 73 is compared with the reference distance, and the ejection amount of the ink 71a of the inkjet head 71 is changed. Thereby, the height of the spacer 15 can be made uniform.

  The ultraviolet light source 72 irradiates the ink 71a dropped on the reflecting surface 4 with ultraviolet UV to cure the ink 71a. As a result, as shown in FIG. 13, the dot-shaped spacers 15 having a predetermined height (20 μm in this embodiment) are arranged on the reflection surface 4 of the substrate 21 in a matrix with a pitch P (1 mm in this embodiment). It is fixedly formed on. Since the spacers 15 are formed in a dot shape by inkjet printing, the spacers 15 can be easily arranged on the reflecting surface 4.

  Next, FIG. 14 is a side view showing a laminating step. In the stacking step, the plurality of substrates 21 on which the spacers 15 are formed are stacked in a direction perpendicular to the reflecting surface 4 (the plate thickness direction of the substrate 21) and sandwiched by a sandwiching member (not shown). As a result, the stacked body 11 having the gap G (see FIG. 15) between the adjacent substrates 21 is formed. The laminated body 11 is provided with a plurality of substrate pairs 29 in which a pair of substrates 21 are paired according to the warp. The board pair 29 is assembled such that the concave surfaces 21 a of the one board 21 and the other board 21 face each other. In this embodiment, the total number Nt of the substrates 21 forming the laminated body 11 is 364, and the substrate pair 29 is formed by the number of the substrates 21 that exceeds 50% of the total number Nt.

  Hereinafter, a case where the warp amount Wa in the A direction of the substrate 21 is larger than the warp amount Wb in the B direction will be described as an example. The substrate pair 29 is assembled so that the concave surfaces 21a face each other, and a pair of substrates 21 are stacked. At this time, the pair of substrates 21 of the substrate pair 29 are oriented so that the direction A, which has a large amount of warp, is in the same direction. Further, all the board pairs 29 are arranged with the direction of the large warpage A being directed in the same direction.

  Further, in each board pair 29, one end 21c having a small plate thickness (thickness) of both ends in the A direction having a large warp amount of one substrate 21 and one plate end having both ends in the A direction having a large warp amount of the other substrate 21. Is arranged so as to face the thick end 21d. As a result, it is possible to prevent accumulation of uneven thickness (uneven thickness) in the laminated body 11.

  Although the substrate pair 29 may be formed by all the substrates 21 forming the laminated body 11, the substrate pair 29 may be formed by a part of the substrates 21. That is, a plurality of substrate pairs 29 may be formed by the substrates 21 having a predetermined ratio exceeding 50% of the total number Nt of the substrates 21 forming the stacked body 11, and the remaining substrates 21 may be randomly arranged.

  FIG. 15 is a side sectional view showing the fixing step. In the fixing step after the stacking step, a predetermined pressing force Fp is applied to the stack 11 from the stacking direction LM to press the stack 11. Thereby, the warp of each substrate 21 of the laminated body 11 is corrected.

  Then, the laminated body 11 is immersed in the liquid adhesive 3 in the storage tank 40 while the pressure applied to the laminated body 11 is continued. As a result, the adhesive 3 enters and fills the gap G. After the laminated body 11 is immersed in the adhesive 3 for a predetermined time (for example, 1 hour), the laminated body 11 is pulled out from the storage tank 40 to cure the adhesive 3. As a result, the laminated body 11 is fixed and the fixed block 12 shown in FIG. 16 is formed. The length of the fixed block 12 in the direction perpendicular to the reflection surface 4 (the length in the stacking direction LM) is about 200 mm.

  Since the concave surface 21a of the substrate 21 is arranged to face the substrate pair 29, the contact area between the substrates 21 can be reduced as compared with the case where the convex surface 21b and the concave surface 21a are arranged to face each other. Therefore, the pressing force Fp for correcting the warp of the substrate 21 can be reduced. Accordingly, it is possible to reduce fine high-frequency irregularities on the reflecting surface 4 and suppress deterioration of the image quality of the aerial image FI.

  It is more desirable to form the substrate pair 29 with 57% or more of the total number Nt of substrates 21 of the stacked body 11 because the pressing force Fp can be further reduced. Further, it is more desirable to form the substrate pair 29 by 71% or more of the total number Nt of the substrates 21 of the stacked body 11.

  In addition, since the spacer 15 that secures the gap G between the adjacent substrates 21 is arranged, the film thickness of the adhesive 3 between the substrates 21 can be made uniform and the respective reflection surfaces 4 can be maintained in parallel. When the gap G becomes large, the film thickness of the adhesive 3 of the optical element 1 becomes large, so that the image of the aerial image FI becomes rough. Therefore, it is desirable to set the gap G to 50 μm or less. On the other hand, if the gap G is made small, the aerial image FI can be formed favorably, but filling of the liquid adhesive 3 becomes difficult. Therefore, it is desirable to set the gap G to 10 μm or more.

  Next, in a cutting step, as shown by a cutting line KT in FIG. 16, the fixed block 12 is cut in a direction parallel to the reflecting surface 4 in a direction perpendicular to the reflecting surface 4 at a predetermined cycle (for example, 1.8 mm). As a result, a plurality of materials 1'of the optical element 1 (see FIG. 4) are formed. A wire saw is preferably used for cutting the fixing block 12, but a slicer may be used.

  At this time, the fixing block 12 is cut in a direction orthogonal to the direction A in which the warp amount of the substrate 21 forming the substrate pair 29 is large. As a result, a large curvature of the reflecting surface 4 orthogonal to the thickness direction of the material 1'of the optical element 1 can be prevented.

  In the polishing step, both sides of the raw material 1'of the optical element 1 are polished by a lapping device to a predetermined thickness (for example, 1.2 mm). Then, both surfaces of the material 1'of the optical element 1 are mirror-finished by a polishing device. As a result, the optical element 1 shown in FIG. 4 is obtained.

  In the optical element arranging step, the two optical elements 1 are arranged so that the extending directions of the reflecting surfaces 4 are orthogonal to each other, and the two optical elements 1 are bonded to each other via an adhesive (not shown). Accordingly, the two optical elements 1 are arranged side by side in the thickness direction (Y direction). The adhesive for adhering the optical element 1 may be the same as or different from the adhesive 3 used in the fixing step.

  In the optical element arranging step, the two stacked optical elements 1 may be housed in a bag-shaped member (not shown) made of a transparent resin film, and then the bag-shaped member may be evacuated. Alternatively, the two optical elements 1 may be fitted in one frame member and arranged so as to overlap each other. This makes it possible to fix the two optical elements in a stacked state without using an adhesive.

  In the step of attaching the reinforcing plate, the reinforcing plate 5 is attached to one end surface of the optical element 1 in the juxtaposed direction with an adhesive. The adhesive for adhering the reinforcing plate 5 may be the same as or different from the adhesive 3 used in the fixing step. As described above, the reflective aerial image forming element 10 shown in FIG. 1 is formed.

  In the step of attaching the reinforcing plate, the reinforcing plate 5 may be joined to both end faces of the two optical elements 1 in the juxtaposed direction. Thereby, the strength of the reflective aerial imaging element 10 can be further improved. Also, the step of attaching the reinforcing plate may be omitted.

  The illumination light L of the light source 20, which is incident on the adhesive 3 between the base materials 2 of the optical element 1 at an incident angle of 45°, for example, is reflected by the reflecting surface 4 several tens of times and then emitted from the adhesive 3. As a result, the light that has entered the adhesive 3 is greatly attenuated and then emitted, so that it hardly contributes to the image formation of the aerial image FI. Therefore, even if the spacer 15 is arranged on the adhesive 3 between the base materials 2 of the optical element 1, there is no great problem.

  According to the present embodiment, in the stacking step, the stacked body 11 is provided with a plurality of board pairs 29 each including a pair of boards 21 in which concave surfaces 21 a due to warpage are arranged to face each other. As a result, the frictional force between the adjacent substrates 21 can be reduced in the fixing step, and the warp of the substrates 21 can be corrected with a small pressing force Fp. Therefore, it is possible to suppress the deterioration of the image quality of the aerial image FI due to the high frequency unevenness on the reflecting surface 4, and to improve the yield of the optical element 1 and the reflective aerial imaging element 10.

  Further, if the substrate pair 29 is formed by 57% or more of the total number Nt of the substrates 21 forming the laminated body 11, the substrate pair 29 can be surely suppressed from being deteriorated in image quality of the aerial image FI.

  In addition, when the substrate pair 29 is formed by the number of the substrates 21 that is 71% or more of the total number Nt of the substrates 21 forming the laminated body 11, the deterioration of the image quality of the aerial image FI can be more reliably suppressed.

  Further, the substrate 21 is formed in a rectangular shape, and in the laminating step, the direction in which the amount of warpage in the two directions (A direction and B direction) in which the pair of substrates 21 forming the substrate pair 29 are parallel to the two sides orthogonal to each other is large ( The first direction) is directed in the same direction, and the layers are stacked. The pair of substrates 21 may be stacked so that the direction in which the amount of warp is large is orthogonal to each other, but it is more preferable to stack them in the same direction as in the present embodiment. As a result, the pair of substrates 21 extends in the same direction and is corrected in the fixing step, so that the frictional force between the substrates 21 is further reduced. Therefore, the pressing force Fp can be made smaller.

  Further, in the stacking process, all the substrate pairs 29 are arranged so that the direction A in which the warp amount is large faces the same direction. Although the direction in which the warp amount of each substrate pair 29 is large may be stacked in different directions, it is more preferable to stack in the same direction as in the present embodiment. As a result, the substrates 21 of each substrate pair 29 extend in the same direction and are corrected in the fixing step, so that the frictional force between the adjacent substrate pairs 29 is further reduced. Therefore, the pressing force Fp can be made smaller.

  In the cutting step, the fixed fixing block 12 (laminate) is cut in the direction (B direction) orthogonal to the direction in which the warp amount is large (A direction). This makes it possible to easily prevent a large curvature of the reflecting surface 4 of the optical element 1. Therefore, the deterioration of the image quality of the aerial image FI can be further suppressed.

  Further, in the stacking step, one end 21c of one of the substrates 21 of the substrate pair 29 having a large warp amount in the A direction and one end 21c having a small thickness, and the other end of the other substrate 21 in the A direction having one end 21d having a large thickness are provided. They are facing each other. Thereby, it is possible to prevent the uneven thickness from being accumulated in the laminated body 11 and to secure the parallelism of the reflecting surface 4 in a good condition.

  Further, the optical element arranging step of arranging the two optical elements 1 so as to overlap each other in the thickness direction so that the reflecting surfaces 4 of the pair of adjacent optical elements 1 are orthogonal to each other is provided. As a result, it is possible to easily obtain the reflective aerial imaging element 10 in which the deterioration of the image quality of the aerial image FI is reduced.

  In this embodiment, the adhesive 3 is applied on each substrate 21 in the laminating step to form the laminated body 11, and the laminated body 11 is pressed to cure the adhesive 3 in the fixing step to form the fixing block 12. You may.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 17 is a perspective view for explaining the formation of the substrate pair 29 of this embodiment. For convenience of explanation, the same parts as those in the first embodiment shown in FIGS. 1 to 16 are designated by the same reference numerals. In this embodiment, the method of pairing the substrate pair 29 is different from that in the first embodiment. Other parts are the same as those in the first embodiment.

  As described above, when the substrate 21 is formed by plate drawing such as the overflow downdraw method (see FIG. 8), the warp amount of the substrate 21 in the direction orthogonal to the drawing direction DF is larger than the warp amount in the drawing direction DF. Easy to grow.

  Further, the state of uneven thickness in the direction orthogonal to the drawing direction DF of the substrate 21 becomes substantially constant. That is, in the substrate 21 that is continuously formed by drawing, the same end portion is likely to be thin out of both end portions in the direction orthogonal to the drawing direction DF.

  Therefore, in the laminating step, one substrate 21s forming the substrate pair 29 is laminated with respect to the other substrate 21t while being rotated 180° about the drawing direction DF as shown by an arrow RT (21s′). . As a result, the concave surfaces 21a of the substrate 21s and the substrate 21t face each other, and there is a high possibility that the direction in which the warp amount is large (the direction orthogonal to the drawing direction DF) is arranged in the same direction. Further, there is a high possibility that the thin end portion of the substrate 21s and the thick end portion of the substrate 21t face each other.

  Thereby, the substrate pair 29 can be formed by the substrate 21 having a predetermined ratio exceeding 50% with respect to the total number Nt of the substrates 21 of the stacked body 11.

  In the cutting step, the fixing block 12 (laminated body 11) fixed in the fixing step is cut in the drawing direction DF. Thereby, as in the first embodiment, it is possible to easily prevent a large curvature of the reflecting surface 4 of the optical element 1.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, the substrate 21 is formed of a glass plate formed into a plate shape by drawing the molten glass in the drawing direction DF. Further, in the stacking step, one of the substrates 21s forming the substrate pair 29 is stacked on the other substrate 21t by 180° about the drawing direction DF as an axis. Accordingly, the substrate pair 29 can be formed without measuring the warp amount and the plate thickness of the substrate 21. Therefore, the number of manufacturing steps of the optical element 1 can be reduced.

  Further, in the cutting step, the fixed laminated body 11 is cut in the drawing direction DF. This makes it possible to easily prevent a large curvature of the reflecting surface 4 of the optical element 1.

  Next, examples of the present invention will be described.

  FIG. 18 is a schematic side view showing the laminated body 11 at the time of manufacturing the optical element 1 of Example 1. Each substrate 21 was made of a glass plate made of borosilicate glass, and was formed in a rectangular shape of 200 mm×200 mm with a plate thickness of 0.53 mm. The refractive index of the substrate 21 is 1.52. Further, the reflective surfaces 4 were formed on both surfaces of the substrate 21 with aluminum having a thickness of 200 nm.

  The total number Nt of the substrates 21 of the laminated body 11 is 364, and an epoxy-based adhesive having a refractive index of 1.51 is used as the adhesive 3 between the substrates 21 in the fixing process so that the film thickness of the adhesive 3 is 20 μm. did. Further, in the fixing step, pressure was applied so as to correct the warp amounts of the substrate 21 in the A direction and the B direction to 30 μm or less, and the pressing force Fp at this time was 588 N.

  In the figure, a layer portion H indicates a portion in which a plurality of substrates 21 are stacked with the concave surface 21a facing upward. The layer portion K indicates a portion in which a plurality of substrate pairs 29 are laminated. In the first embodiment, the layer portion H, the layer portion K, and the layer portion H are arranged in order from the bottom. The upper layer portion H has 52 substrates 21, the lower layer portion H has 104 substrates 21, and the layer portion K has 208 substrates 21. As a result, the substrate pair 29 is formed by 57% of the total number Nt of the substrates 21 that form the stacked body 11.

  FIG. 19 is a schematic side view showing the laminated body 11 at the time of manufacturing the optical element 1 of Example 2. In the second embodiment, the layer portion K, the layer portion H, the layer portion K, the layer portion H, the layer portion K, the layer portion H, and the layer portion K are arranged in this order from the bottom. Each layer portion H and each layer portion K are formed by 52 substrates 21. As a result, the substrate pair 29 is formed by 57% of the total number Nt of the substrates 21 that form the stacked body 11. The pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 588N. Other configurations are similar to those of the first embodiment.

  20: is a schematic side view which shows the laminated body 11 at the time of manufacture of the optical element 1 of Example 3. FIG. In the third embodiment, 52 layers of the layer portion M including the seven substrates 21 are laminated. In the layer portion M, two substrate pairs 29 and three substrates 21 with the concave surface 21a facing upward are stacked in order from the bottom. As a result, the substrate pair 29 is formed by 57% of the total number Nt of the substrates 21 that form the stacked body 11. The pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 588N. Other configurations are similar to those of the first embodiment.

  In the fourth embodiment, as in the first embodiment shown in FIG. 18, the layer portion H, the layer portion K, and the layer portion H are arranged in order from the bottom. The upper and lower layer portions H have 52 substrates 21, and the layer portion K has 260 substrates 21. As a result, the substrate pair 29 is formed of 71% of the total number Nt of the substrates 21 that form the stacked body 11. Further, the pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 392N. Other configurations are similar to those of the first embodiment.

  21: is a schematic side view which shows the laminated body 11 at the time of manufacture of the optical element 1 of Example 5. FIG. In Example 5, the layer portion K and the layer portion H are arranged in order from the bottom. The number of substrates 21 forming the layer portion K is 312, and the number of substrates 21 forming the layer portion H is 52. As a result, the substrate pair 29 is formed by 86% of the total number Nt of the substrates 21 that form the stacked body 11. The pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 245N. Other configurations are similar to those of the first embodiment.

  22: is a schematic side view which shows the laminated body 11 at the time of manufacture of the optical element 1 of Example 6. FIG. In Example 6, only the layer portion K was arranged by 364 substrates 21. As a result, the substrate pair 29 is formed by 100% of the total number Nt of the substrates 21 that form the stacked body 11. The pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 147N. Other configurations are similar to those of the first embodiment.

[Comparative Example 1]
FIG. 23 is a schematic side view showing the laminated body 11 at the time of manufacturing the optical element 1 of Comparative Example 1. In Comparative Example 1, only the layer portion H was arranged by 364 substrates 21. As a result, the substrate 21 forming the substrate pair 29 is 0% with respect to the total number Nt of the substrates 21 forming the stacked body 11. The pressing force Fp for correcting the warp of the substrate 21 in the fixing step was 4904N. Other configurations are similar to those of the first embodiment.

[Comparative example 2]
The laminated body of Comparative Example 2 was configured in the same manner as Comparative Example 1 shown in FIG. Further, the pressing force Fp in the fixing step was set to 245N as in the fifth embodiment. At this time, the warp of the substrate 21 was not corrected. Other configurations are similar to those of the first embodiment.

  Table 1 shows the results of image evaluation of the optical elements 1 of Examples and Comparative Examples. A chart image of a square lattice was obliquely emitted from the projector with respect to the incident surface 18 of the optical element 1, and an image reflected by the reflecting surface 4 and projected on the screen was visually observed to perform image evaluation.

  In Table 1, the image distortion is indicated by x when the lattice distortion is confirmed, and by o when the lattice distortion is not confirmed. Further, the image unevenness is evaluated on a scale of 5 with 5 being a case where almost no high-frequency image unevenness occurs and 1 being a large case.

  According to Table 1, in Examples 1 to 6, the pressurizing force Fp becomes smaller as the ratio of the substrate pair 29 increases (57%, 71%, 86%, 100%), and therefore, the effect of suppressing high-frequency image unevenness is obtained. Has improved. In Comparative Example 2, high-frequency image unevenness was suppressed to the same extent as in Example 5. On the other hand, in Comparative Example 1, as shown in the screen image of FIG. 24, when the pressing force Fp required for correction is applied, a large amount of high-frequency image unevenness occurs.

  Further, in each of Examples 1 to 6 and Comparative Example 1, no image distortion was confirmed. On the other hand, in Comparative Example 2, as shown in the screen image of FIG. 25, a square lattice image was not formed and image distortion was confirmed.

  Therefore, when the substrate pair 29 is formed of 57% or more of the total number Nt of the substrates 21 forming the laminated body 11, the image distortion and the image unevenness can be suppressed. As a result, the image quality of the aerial image FI can be reliably improved. Further, when the substrate pair 29 is formed by 71% or more of the total number Nt of the substrates 21 forming the laminated body 11, the substrate pair 29 can be further suppressed in image unevenness. Further, when the substrate pair 29 is formed by 86% or more of the total number Nt of the substrates 21 forming the laminated body 11, the substrate pair 29 can be further suppressed in image unevenness.

  In addition, by forming the substrate pair 29 with the number of the substrates 21 that exceeds 50% of the total number Nt of the substrates 21 that form the laminated body 11, the image distortion and the image unevenness can be suppressed more than the case of 50% or less. ..

  INDUSTRIAL APPLICABILITY The present invention can be applied to a reflective aerial imaging element for forming a real image of a projection object in the air and an optical element used for the reflective aerial imaging element.

DESCRIPTION OF SYMBOLS 1 Optical element 2 Base material 3 Adhesive 4 Reflective surface 5 Reinforcing plate 10 Reflective aerial imaging element 11 Laminated body 12 Fixed block 15 Spacer 18 Incident surface 19 Exit surface 20 Light source 21 Substrate 21a Concave 21b Convex 29 Substrate 40 Storage tank 50 Gutter-shaped member 100 Aerial image display device DF Draw-out direction G Gap OB Projected object FI Aerial image L Illumination light LM Stacking direction K, H, M Hierarchical part

Claims (9)

In the method of manufacturing a light-transmissive optical element in which reflective surfaces parallel to the thickness direction are arranged in parallel at a predetermined cycle,
A laminating step of forming a laminated body by laminating a plurality of thin plate-shaped transparent substrates having the reflection surface formed on one surface perpendicular to the thickness direction in the thickness direction,
A fixing step of fixing the laminated body by applying pressure from the plate thickness direction,
A cutting step of forming a plurality of the optical elements by cutting the fixed laminated body at a predetermined cycle in the plate thickness direction,
In the stacking step, a plurality of substrate pairs consisting of a pair of the substrates combined so that the concave surfaces due to the warp are opposed to each other are provided in the stack ,
The substrate is formed by a rectangle,
In the laminating step, a pair of the substrates forming the substrate pair are laminated with the first direction having the larger warp amount in the two directions parallel to the two orthogonal sides facing the same direction,
In the stacking step, all the substrate pairs are arranged with the first direction facing the same direction,
In the cutting step, the fixed laminated body is cut in a direction orthogonal to the first direction . In the method for manufacturing a light-transmissive optical element in which reflective surfaces parallel to the thickness direction are arranged in parallel at a predetermined cycle,
A laminating step of forming a laminated body by laminating a plurality of thin plate-shaped transparent substrates having the reflection surface formed on one surface perpendicular to the thickness direction in the thickness direction,
A fixing step of fixing the laminated body by applying pressure from the plate thickness direction,
A cutting step of forming a plurality of the optical elements by cutting the fixed laminated body at a predetermined cycle in the plate thickness direction,
In the stacking step, a plurality of substrate pairs consisting of a pair of the substrates combined so that the concave surfaces due to the warp are opposed to each other are provided in the stack,
The substrate is formed by a rectangle,
In the laminating step, a pair of the substrates forming the substrate pair are laminated with the first direction having the larger warp amount in two directions parallel to two orthogonal sides facing the same direction,
In the stacking step, one of the two ends of the one of the substrate pair in the first direction, which has a small thickness, and the other end of the other substrate in the first direction, which has a large thickness, face each other. And a method for manufacturing an optical element. The method for manufacturing an optical element according to claim 2, wherein in the stacking step, all the substrate pairs are arranged with the first direction facing the same direction. The method for manufacturing an optical element according to claim 3, wherein, in the cutting step, the fixed laminated body is cut in a direction orthogonal to the first direction. In the method for manufacturing a light-transmissive optical element in which reflective surfaces parallel to the thickness direction are arranged in parallel at a predetermined cycle,
A laminating step of forming a laminated body by laminating a plurality of thin plate-shaped transparent substrates having the reflection surface formed on one surface perpendicular to the thickness direction in the thickness direction,
A fixing step of fixing the laminated body by applying pressure from the plate thickness direction,
A cutting step of forming a plurality of the optical elements by cutting the fixed laminated body at a predetermined cycle in the plate thickness direction,
In the stacking step, a plurality of substrate pairs consisting of a pair of the substrates combined so that the concave surfaces due to the warp are opposed to each other are provided in the stack,
The substrate is a glass plate formed into a plate shape by pulling out molten glass in a predetermined pulling direction,
A method for manufacturing an optical element, characterized in that, in the laminating step, one of the substrates forming the substrate pair is rotated with respect to the other by 180° about the drawing direction as an axis. The method for manufacturing an optical element according to claim 5, wherein, in the cutting step, the fixed laminated body is cut in the drawing direction. 7. The method of manufacturing an optical element according to claim 1, wherein the substrate pair is formed of 57% or more of the total number of the substrates forming the laminated body. 7. The method of manufacturing an optical element according to claim 1, wherein the substrate pair is formed by 71% or more of the total number of the substrates forming the laminated body. A method of manufacturing a reflective aerial imaging element comprising a pair of the optical elements manufactured by the method of manufacturing an optical element according to claim 1.
A method for manufacturing a reflective aerial imaging element, comprising an optical element arranging step of arranging a pair of the optical elements so as to overlap each other in the thickness direction so that the reflecting surfaces are orthogonal to each other.