WO2018139141A1

WO2018139141A1 - Optical element and image display device using same

Info

Publication number: WO2018139141A1
Application number: PCT/JP2017/046392
Authority: WO
Inventors: 有希前田; 前川　聡
Original assignee: 株式会社パリティ・イノベーションズ
Priority date: 2017-01-30
Filing date: 2017-12-25
Publication date: 2018-08-02
Also published as: JP7152019B2; JPWO2018139141A1

Abstract

Provided is an optical element that improves the contrast of an image by suppressing stray light not contributing to forming of a real mirror image and that reduces white blur by suppressing scattering of light between two-surface corner reflectors. An optical element 1 includes a base 2 that is formed of a transparent material and forms one flat surface, and a plurality of protruding parts 3 that are integrally formed so as to protrude from the base 2. Adjacent vertical surfaces 31, 32 among side surfaces constituting each protruding part 3 form a two-surface corner reflector 30 having two substantially perpendicular surfaces. Disposed between the plurality of protruding parts 3 are: low refractive index parts 4 composed of a medium having a refractive index that is lower than that of the transparent material constituting the protruding parts 3; and light absorbing parts 5 that absorb light guided between the plurality of the protruding parts 3. In addition, the low refractive index parts 4 contact the two-surface corner reflectors 30.

Description

Optical element and image display device using the same

The present invention relates to an optical element that forms a real image of an observation object on one surface side in a space on the other surface side, and an image display device using the optical element.

An optical element has been devised in which a projection object is arranged on one surface side of a plane body that partitions a certain space, and a mirror image of the projection object is formed at a position that is plane-symmetric in the space on the other surface side. . As this type of optical element, there is known an optical element having a structure in which a plurality of two-surface corner reflectors each composed of two minute mirror surfaces (reflection surfaces) perpendicular to each other are assembled in a plane (for example, Patent Documents). 1).

Patent Document 1 discloses an optical element having a two-sided corner reflector array in which a plurality of two-sided corner reflectors are arranged in a grid on a single plane. In this optical element, each mirror surface forming a dihedral corner reflector is arranged perpendicular to the element surface of the optical element. Therefore, the light emitted from the observation object arranged on one surface side of the element surface is reflected and bent twice by the two-surface corner reflector when passing through the optical element, and the other surface without the observation object. A real image is formed in the side space. Thereby, the real image is formed so that the object to be observed exists at a symmetrical position with respect to the element surface of the optical element.

JP 2011-191404 A

In the optical element described in Patent Document 1, a plurality of cube-shaped projecting portions protruding from the surface of the base are arranged, and the inner wall of the projecting portion is used as a mirror surface, and the total reflection of light on the inner wall is used. Then, a real mirror image is formed. Here, the projecting portion is formed by providing a lattice-like groove between adjacent projecting portions (two-surface corner reflectors). In such a configuration, a part of the light incident on the substrate is guided to the groove side without entering the projecting portion. Of the light emitted from the object to be observed, the light incident on the mirror surface at an angle smaller than the critical angle is guided to the groove side without being reflected by the mirror surface. The light guided to the groove side becomes stray light that does not contribute to the image formation of the real mirror image and reduces the contrast of the stereoscopic image. Further, since the groove between the two-surface corner reflectors is as fine as μm, when ambient light such as external illumination light enters the groove, the light is irregularly reflected by the groove, causing white blurring.

The present invention solves the above-described problem, suppresses stray light that does not contribute to the image formation of a real mirror image, improves the contrast of a stereoscopic image, and suppresses irregular reflection of light between a plurality of two-surface corner reflectors. An object of the present invention is to provide an optical element capable of reducing white blur and an image display apparatus using the optical element.

In order to solve the above-described problems, the present invention provides an optical element that forms a real image of an object to be observed on one surface side in a space on the other surface side and is formed of a transparent material and forms a single plane. And a plurality of protrusions formed integrally with the base so as to protrude from the base, the protrusion having three or more side surfaces having an angle with respect to the base. Two adjacent surfaces of the side surfaces are perpendicular to the base and are substantially orthogonal to each other, forming a two-surface corner reflector that reflects light emitted from the object to be observed, and a plurality of the protrusions. Between the projecting portions, a low refractive index portion made of a medium having a refractive index lower than the refractive index of the transparent material forming the projecting portions, and a light absorbing portion that absorbs light guided between the plurality of projecting portions. And the low refractive index portion is in contact with the two-surface corner reflector And wherein the door.

In the optical element, it is preferable that the low refractive index portion has a thickness of 1 μm or more from the surface of the dihedral corner reflector.

In the optical element, it is preferable that the light absorbing portion is in contact with a side surface of the protruding portion that does not form the two-surface corner reflector.

In the above optical element, it is preferable that the light absorbing portion is composed of particles having a diameter of 1 μm or more.

The optical element further includes a transparent panel that collectively covers the plurality of protruding portions, and the light absorbing portion is formed in a region of the transparent panel that faces the plurality of protruding portions. Preferably it is.

The optical element is preferably used in a video notation device.

According to the present invention, since the low refractive index portion is in contact with the side surface forming the dihedral corner reflector, the optical element has a large refractive index difference from the medium constituting the optical element, and the total reflection efficiency is improved. Real mirror image can be brightened. In addition, since a light absorbing portion is provided between the projecting portions, the light guided between the projecting portions is cut, and the occurrence of stray light that does not contribute to the image formation of the real mirror image is suppressed. The contrast of the real mirror image can be improved. Furthermore, since the light absorbing section cuts off ambient light such as external illumination light, the light is not irregularly reflected between the fine protrusions, and the occurrence of white blur can be suppressed.

1 is a schematic perspective view conceptually showing a configuration example of an optical element according to a first embodiment of the present invention. (A) (b) is a figure which shows typically the image formation mode by the said optical element. The perspective view which expanded a part of said optical element. (A) is a side view of the optical element, and (b) is a top view. The side view for demonstrating the effect | action of the said optical element. (A) and (b) are the side views for demonstrating the structure which concerns on the 1st modification of the said optical element, and its formation method. (A) is a side view for demonstrating the structure and its formation method which concern on the 2nd modification of the said optical element, (b) is an enlarged view of the dashed-dotted line area | region of (a). The side view for demonstrating the structure and its formation method which concern on the 3rd modification of the said optical element. The side view for demonstrating the structure and its formation method which concern on the 4th modification of the said optical element. The perspective view which shows notionally the structural example of the video display apparatus provided with the said optical element.

An optical element according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical element 1 of the present embodiment includes a two-surface corner reflector 30 composed of mirror surfaces (vertical surfaces 31 and 32) that are perpendicular to the substrate 2 and substantially orthogonal to each other. The plurality of two-surface corner reflectors 30 are arranged in a grid on one plane of the base 2 to form a two-surface corner reflector array 30S.

When the object to be observed O is arranged on one surface side of the optical element 1, the real image (real mirror image P) of the object to be observed O is connected to the space on the other surface side of the element surface 1S of the optical element 1. Let me image. In other words, the optical element 1 forms an image of the real mirror image P of the observation object O at a plane-symmetrical position with the element surface 1S as a symmetry plane. Here, the element surface 1 </ b> S refers to a virtual plane orthogonal to the two

vertical surfaces

31 and 32 constituting the two-surface corner reflector 30. Note that the dihedral corner reflector 30 is as fine as μm in comparison with the total size of the optical element 1 being in the order of cm or m, and in FIG. It is shown conceptually in a letter shape.

The imaging mode by the two-surface corner reflector array 30S will be described with reference to FIGS. In FIG. 2A, light emitted from a point light source o as a projection object is assumed to travel three-dimensionally from the back side to the front side of the page. Light (solid arrow) emitted from the point light source o is reflected by one mirror surface (vertical surface 31) constituting the two-surface corner reflector 30 when passing through the optical element 1 (not shown in FIG. 2A). Then, after being reflected by the other mirror surface (vertical surface 32), it passes through the element surface 1S (see FIG. 2B). In this way, the light emitted from the optical element 1 (dashed line arrow) passes through the element surface 1S while spreading in a plane symmetrical position p of the point light source o. That is, the transmitted light of the optical element 1 is focused at a plane symmetry position p with respect to the element surface 1S of the point light source o, and forms an image as a real mirror image P (see FIG. 1).

As shown in FIGS. 3 and 4 (a) and 4 (b), the base 2 is formed of a transparent material and forms a plane. The optical element 1 has a plurality of protruding portions 3 formed so as to protrude from the base 2. The plurality of protrusions 3 are integrally formed with the base 2 by the same transparent material as the base 2.

The protruding portion 3 has three or more side surfaces having an angle with respect to the base 2. The protruding portion 3 of the present embodiment has a truncated pyramid shape, and includes two surfaces perpendicular to the base 2 (vertical surfaces 31 and 32) and two surfaces inclined with respect to the base 2 (inclined surfaces 33 and 34). 4 side surfaces and an upper surface 35 forming a surface parallel to the base 2. Of the side surfaces, two surfaces, the

vertical surfaces

31, 32, are adjacent to each other, and two surfaces, the

inclined surfaces

33, 34, are adjacent to each other. The

vertical surfaces

31 and 32 are disposed so as to be substantially orthogonal to each other. The light (solid line arrow in FIG. 4A) incident on the protruding portion 3 from the base 2 is totally reflected twice by the inner wall surfaces of the

vertical surfaces

31 and 32 and is emitted from the upper surface 35 of the protruding portion 3.

The upper surface 35 is defined by ridge lines with the

vertical surfaces

31 and 32 and the

inclined surfaces

33 and 34, and the lengths thereof are substantially equal, and are substantially square in a top view (see FIG. 4B). The vertical surface 31 (32) is an inclined surface in a side view (see FIG. 4B), where the boundary line with the base 2 (dotted line in FIG. 4A) is the lower base, the ridge line with the upper surface 35 is the upper base, This is a trapezoid having the ridge line with 33 and 34 as a hypotenuse and the ridge line with adjacent

vertical surfaces

32 and 31 as a vertical side.

On the surface of the optical element 1, a plurality of protrusions 3 having the above-mentioned shape are arranged in a grid. In the adjacent protrusions 3, one vertical surface 31 and the other inclined surface 34 face each other, and one vertical surface 32 and the other inclined surface 33 face each other. In other words, the plurality of protrusions 3 are formed with lattice-like grooves 21 between the

vertical surfaces

31 and 32 and the

inclined surfaces

34 and 33 facing each other. Further, a plane parallel to the base 2 is formed between the side of the vertical surface 32 (31) facing the base 2 and the side of the inclined surface 33 (34) on the base 2 side, and the bottom of the groove 21 is formed. A bottom surface 22 is formed.

Further, the optical element 1 is guided to the groove 21 between the plurality of protrusions 3, the low refractive index part 4 made of a medium having a refractive index lower than the refractive index of the transparent material forming the protrusions 3, and the groove 21. A light absorbing portion 5 that absorbs the waved light is disposed. The low refractive index portion 4 is in contact with the

vertical surfaces

31 and 32 forming at least a two-surface corner reflector.

A transparent material that has a light transmittance of 80% or more and a refractive index of 1.3 or more and hardly deteriorated due to heat or humidity is used for the medium of the base 2 and the protruding portion 3 constituting the optical element 1. Examples of such a transparent material include acrylic resin and glass. In the optical element 1 of the present embodiment, it is particularly preferable to use a cycloolefin polymer (COP) which is a hydrocarbon polymer having a low water absorption property, an amorphous structure and an alicyclic structure. Examples of the cycloolefin polymer include trade name: ZEONOR (registered trademark) (grade: 1020R, light transmittance: 92%, refractive index: 1.53) manufactured by ZEON Corporation. Further, the low refractive index portion 4 desirably has a refractive index of 1.4 or less in order to reduce the critical angle on the

vertical surfaces

31 and 32 and easily cause total reflection. The medium of the low refractive index portion 4 is air.

In producing the optical element 1 of the present embodiment, first, a portion excluding the low refractive index portion 4 and the light absorbing portion 5, that is, a dihedral corner reflector array 30S composed of the base 2 and the plurality of protruding portions 3 is produced. The As a method for producing the two-sided corner reflector array 30S, for example, a method of injection-molding a translucent resin or a hot press molding method using a mold such as a stamper can be cited. The mold is manufactured by, for example, a method in which a shape corresponding to the shape of the protrusion 3 and the groove 21 (see FIG. 3) described above is formed on a metal master plate by nano-processing, and then reversal is performed. Further, for example, by using an X-ray lithography method, it is possible to produce the protruding portion 3 and the groove 21 having four side surfaces directly on the base 2 made of a transparent material.

In the optical element 1 of the present embodiment, two of the four surfaces forming the protruding portion 3 are the

inclined surfaces

33 and 34. That is, the protruding portion 3 has a truncated pyramid shape. In addition, a bottom surface 22 is provided in the groove 21 between the plurality of adjacent protruding portions 3. According to such a shape, it is possible to attach a so-called “drawer taper” to the protruding portion 3 which is a fine structure on the order of μm, and when the two-sided corner reflector array 30S is formed by molding, The two-sided corner reflector array 30S can be easily removed from a mold such as a stamper.

The width W of one side in the top view of the pitch 3 of the protruding portion 3 including the groove 21 is, for example, 100 to 700 μm (see FIG. 4B). Note that the pitch width W is set according to the pop-out distance of the real mirror image P (see FIG. 1). For example, when the pop-out distance is 10 cm, the pitch width W is about 280 μm. The plate thickness of the optical element 1 including the base 2 and the protrusions 3 is generally 1 to 3 mm. The height H (depth of the groove 21) of the protrusion 3 from the base 2 (the bottom surface 22 of the groove 21) is set to be equal to or larger than the pitch width W.

The inclination angle θ of the

inclined surfaces

33 and 34 with respect to the normal of the base 2 is preferably 5 to 25 ° (see FIG. 4A). By setting the inclination angle θ to 5 ° or more, a necessary draft taper can be ensured, and the removal from the mold can be facilitated when the two-surface corner reflector array 30S is manufactured. In addition, by setting the inclination angle θ to 25 ° or less, the size (width L) of the upper surface 35 serving as an emission surface of the light reflected by the two-surface corner reflector 30 depends on the height H of the protrusion 3. And the darkness of the real mirror image P can be suppressed. Temporarily, the height H of the protruding portion 3 is 300 μm, the width W of one side in the top view of the pitch 3 of the protruding portion 3 is 300 μm, the width L of one side of the upper surface 35 is 200 μm, and the inclination angle θ is 18 °. In this case, the width D of the bottom surface 22 of the groove 21 is about 2.5 μm. In addition, the numerical value shown here is a representative value shown as an example of this embodiment, and this invention is not limited to these numerical values.

The optical element 1 of the present embodiment is obtained by further forming the low refractive index portion 4 and the light absorbing portion 5 on the two-surface corner reflector 30 manufactured as described above. For the light absorbing portion 5, for example, black ink or particulate pigment is used. Moreover, it is preferable that the low refractive index portion 4 has a thickness of 1 μm or more from the surfaces of the

vertical surfaces

31 and 32 forming the dihedral corner reflector 30. The low refractive index portion 4 is formed so that the portion having a thickness of 1 μm or more from the surfaces of the

vertical surfaces

31 and 32 forming the dihedral corner reflector 30 is 50% or more of the total area of the

vertical surfaces

31 and 32. It only has to be done. When light is totally reflected by the

vertical surfaces

31 and 32 forming the dihedral corner reflector 30, if there is a medium having a high refractive index outside the

vertical surfaces

31 and 32 with an interval of about the wavelength of the light, an evanescent wave is generated. In some cases, light is transmitted through the inner surface of the

vertical surfaces

31 and 32, and total reflection on the inner wall surfaces of the

vertical surfaces

31 and 32 is suppressed. Therefore, the low refractive index portion 4 having a thickness of 1 μm or more is disposed on at least 50% of the total area of the

vertical surfaces

31 and 32 at least outside the

vertical surfaces

31 and 32 in a region where evanescent waves can ooze out. Thus, it is possible to suppress a decrease in total reflection efficiency and prevent a decrease in luminance of the real mirror image P.

As a method for forming the low refractive index portion 4 and the light absorbing portion 5, for example, a method of applying an ink containing a light absorbing material toward the inclined surface 33 (34) and the bottom surface 22 of the groove 21 by micro ink jet printing. Is mentioned. In this way, the ink applied to the inclined surface 34 (33) and the bottom surface 22 of the groove 21 becomes the light absorbing portion 5, and air exists on the vertical surface 31 (32) side where the ink is not applied. The space in which this air exists becomes the low refractive index portion 4. As long as there is no problem in practical use, there may be uneven coating on the inclined surface 34 (33) or the groove 21, and some ink may adhere to the vertical surface 31 (32).

In the optical element 1 produced in this way, as shown in FIG. 5, the low refractive index portion 4 is in contact with the vertical surface 32 (the same applies to the vertical surface 31) forming the dihedral corner reflector 30. The refractive index difference from the medium constituting 1 is increased. For this reason, the critical angle at the vertical surface 32 is reduced, and light having a small incident angle α (solid arrow in the figure) that is not totally reflected in the absence of the low refractive index portion 4 can be totally reflected. Efficiency is improved. As a result, the real mirror image P can be brightened.

In addition, since the light absorbing portion 5 is provided between the projecting portions 3, the light incident on the substrate 2 is not incident on the projecting portion 3, but is guided from the bottom surface 22 to the groove 21 side. Light (broken arrow in the figure) is cut by the light absorbing portion 5. In addition, light that is incident on the vertical surface 32 at an angle of incidence smaller than the critical angle and transmitted to the groove 21 side (dotted line arrow in the figure) is also cut. In this way, the light guided to the groove 21 side is cut by the light absorption unit 5, so that stray light that does not contribute to the image formation of the real mirror image P can be suppressed, and the contrast of the real mirror image P can be suppressed. Can be improved.

Further, the groove 21 between the two-surface corner reflectors 30 is as fine as μm, but even if ambient light such as external illumination light (two-dot chain line arrow in the figure) is incident on the groove 21, no light is emitted. Since the absorption part 5 cuts it, light is not diffusely reflected by the fine groove | channel 21, but generation | occurrence | production of white blur can be suppressed.

The light absorbing portion 5 is preferably in contact with the side surface of the protruding portion 3 that does not form the two-surface corner reflector 30, that is, in the present embodiment, the

inclined surfaces

33 and 34. It is possible that a part of the light incident on the projecting portion 3 from the base 2 enters the

inclined surfaces

33 and 34 instead of the

vertical surfaces

31 and 32. This light also does not contribute to the image formation of the real mirror image P, and when guided to the groove 21 side, it becomes stray light that lowers the contrast of the real mirror image P. Therefore, the light guided to the groove 21 side can be cut by arranging the light absorbing portion 5 in contact with the

inclined surfaces

33 and 34.

The configuration of the low refractive index portion 4 and the light absorbing portion 5 and the formation method thereof are not limited to those described above. Hereinafter, a modified example related to the configuration of the low refractive index portion 4 and the light absorbing portion 5 and a method for forming the modified example will be described.

As a first modified example, as shown in FIG. 6A, a removable sealing material Rm is formed in a thickness of 1 μm in advance on the vertical surface 32 (31), and the groove 21 is made of a light absorbing material Am. Examples of the forming method include filling, curing the filled light absorbing material Am, and then removing the sealing material Rm. According to this forming method, as shown in FIG. 5B, a space having a thickness of about 1 μm is provided from the vertical surface 32 (31) in the space where the sealing material Rm is formed, and this gap is low. The light absorbing material Am that becomes the refractive index portion 4 and is filled excluding the gap becomes the light absorbing portion 5. Examples of this forming method include a method in which only the sealing material Rm is removed by immersing them in a predetermined solvent in which the light absorbing material Am is not dissolved but the sealing material Rm is dissolved.

Also in the first modified example, since the low refractive index portion 4 is in contact with the vertical surface 32 (31) forming the dihedral corner reflector 30, the total reflection efficiency is improved and the real mirror image P can be brightened. it can. Moreover, since the light absorption part 5 is provided between the protruding parts 3, a stray light can be suppressed and the contrast of the real mirror image P can be improved. Further, in this first modification, the light absorbing portion 5 occupies a larger proportion in the groove 21 than in the configuration example shown in FIG. 5, so that ambient light such as illumination light itself is prevented from entering the groove 21. The occurrence of white blur can be effectively suppressed.

As a second modification, as shown in FIG. 7A, there is a method of filling the grooves 21 between the plurality of protruding portions 3 with substantially spherical light absorbing particles 5s. For the light absorbing particles 5s, for example, resin, carbon or the like is used, and particles in which carbon black is included in crosslinked polymer fine particles are particularly preferable. The lower limit of the particle diameter of the light absorbing particles 5s is 1 μm or more, preferably 2 μm or more. The upper limit of the particle diameter of the light-absorbing particles 5 s should be at least smaller than the maximum width of the groove 21, and is preferably 10 μm or less in consideration of the filling property into the groove 21.

In this second modification, a part of the light absorbing particles 5s also adheres to the vertical surface 32 (31). However, as shown in FIG. 7B, since the light absorbing particles 5s are substantially spherical, there are few places where the light absorbing particles 5s and the vertical surface 32 (31) are in contact with each other. There are a large number of gaps (air) between them. Therefore, this gap functions as the low refractive index portion 4. Note that, as described above, in the low refractive index portion 4, the portion having a thickness of 1 μm or more from the surfaces of the

vertical surfaces

31 and 32. The thickness of the low refractive index portion 4 may be partially 1 μm or less. According to the second modification, the low refractive index portion 4 and the light absorbing portion 5 are formed by a simple method of filling the grooves 21 between the plurality of protruding portions 3 with the substantially spherical light absorbing particles 5s. can do. Further, as in the above configuration example, the stray light that does not contribute to the image formation of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and the irregular reflection of light between the plurality of two-surface corner reflectors 30 is suppressed, White blur can be reduced.

As a third modified example, as shown in FIG. 8, it further includes a transparent panel 6 that collectively covers the plurality of protruding portions 3, and the light absorbing portion 5 is a plurality of protruding portions of the transparent panel 6. The method of forming in the area | region facing the groove | channel 21 between 3 is mentioned. For the transparent panel 6, glass, acrylic resin, glass and transparent material are used.

In this forming method, for example, a pattern of the groove 21 between the plurality of protrusions 3 is scanned, and the same pattern printed on the transparent panel 6 with a light absorbing material (ink) is used as the plurality of protrusions 3. Laminate after precisely aligning with the groove 21 between them. As long as there is no problem in practical use, the printed pattern may be slightly different from the actual groove pattern, and there may be a slight misalignment in bonding. For example, the width of the printed groove pattern may have an error of about ± 20 μm compared to the actual width of the groove 21, and the positional deviation at the time of bonding may be about ± 20 μm.

In the third modified example, a space surrounded by the grooves 21 between the plurality of protruding portions 3 and the light absorbing portion 5 formed in the transparent panel 6 is the low refractive index portion 4. Also in the third modification example, as in the above configuration example, and in the above configuration example, stray light that does not contribute to the image formation of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and a plurality of White blurring can be reduced by suppressing irregular reflection of light between the two-surface corner reflectors 30.

Further, in each configuration example described above, it is necessary to form the light absorbing portion 5 in the groove 21 three-dimensionally. On the other hand, according to the third modification, the light absorbing portion 5 is flat. Since it prints on the transparent panel 6 of a shape, the light absorption part 5 can be formed substantially two-dimensionally, and the low refractive index part 4 and the light absorption part 5 can be formed easily.

As shown in FIG. 9, the fourth modified example is one in which the protruding portion 3 is a cube, and the

inclined surfaces

33 and 34 in the above configuration example do not exist, and the side surface of the protruding portion 3 is configured 4. Each of the surfaces is a vertical surface (vertical surface 36 in the illustrated example). The low refractive index portion 4 is also provided on the vertical surface 36 side. In the configuration example having the

inclined surfaces

33 and 34 described above, the light emitted from the observation object O (see FIG. 1) in the direction opposite to the inner angle of the

vertical surfaces

31 and 32 is reflected twice by the

vertical surfaces

31 and 32. Thus, the real mirror image P is imaged. On the other hand, in the fourth modified example, light from the direction opposite to the inner angle of the

vertical surfaces

31 and 32 is reflected by the two-surface corner reflector of the vertical surface 36 and a vertical surface (not shown) orthogonal thereto. Thus, a real mirror image can be formed.

Next, a video display apparatus according to an embodiment of the present invention will be described with reference to FIG. The video display device 10 is a specific application of the optical element 1 described above, and includes a box 12 having an opening 11 on an upper surface, and a video display unit 13 provided on an inner surface of the box 12. Prepare. The optical element 1 is attached to the opening 11 of the box 12. In the illustrated example, the video display unit 13 uses, for example, a liquid crystal display device, and in the illustrated example, the image “A” is displayed in an inverted posture in which the character “A” is inverted upside down. The light emitted from the image display unit 13 is bent and reflected by the optical element 1 to form a real mirror image of the letter “A”. The observer can view the real mirror image of the letter “A” as an aerial image when looking into the optical element 1 with the viewpoint Ep placed obliquely above the image display device 10.

The present invention is not limited to the above embodiment and various modifications, and various modifications can be made. In the above-described embodiment and the modification, the protruding portion 3 has a truncated pyramid shape or a cubic shape having four side surfaces, but has two vertical surfaces and an upper surface that emits light. For example, a triangular frustum shape or a pyramid shape having five or more corners may be used. Further, the light absorbing portion 5 is not necessarily limited to the configuration example described above as long as it exists between the plurality of protruding portions 3 so that the low refractive index portion 4 is formed between the

vertical surfaces

31 and 32. I can't. The low refractive index portion 4 is most preferably mainly composed of air having a low refractive index. However, the low refractive index portion 4 is a translucent resin, hollow silica particle, or mesoporous material having a refractive index lower than that of the protrusion 3 itself. Silica particles and the like may be applied as appropriate.

DESCRIPTION OF SYMBOLS 1 Optical element 10 Image | video display apparatus 2 Base | substrate 3 Protruding part 30 Two-

surface corner reflector

31, 32 Vertical surface (side surface)
33, 34 Inclined surface (side surface)
4 Low refractive index part 5 Light absorbing part 5s Light absorbing particle (particle)
6 Transparent panel

Claims

An optical element that forms a real image of an observation object on one surface side in a space on the other surface side,
A base formed of a transparent material to form a flat surface, and a plurality of protrusions formed integrally with the base so as to protrude from the base;
The protrusion has three or more side surfaces having an angle with respect to the base,
Two adjacent surfaces of the side surfaces are perpendicular to the base and are substantially orthogonal to each other to form a two-surface corner reflector that reflects light emitted from the object to be observed,
Between the plurality of protrusions, a low refractive index portion made of a medium having a refractive index lower than the refractive index of the transparent material forming the protrusions and light guided between the plurality of protrusions is absorbed. And a light absorbing part to be arranged,
The optical element, wherein the low refractive index portion is in contact with the dihedral corner reflector.
The optical element according to claim 1, wherein the low refractive index portion has a thickness of 1 μm or more from the surface of the dihedral corner reflector.
The optical element according to claim 1, wherein the light absorbing portion is in contact with a side surface of the protruding portion that does not form the two-surface corner reflector.
The optical element according to any one of claims 1 to 3, wherein the light absorbing portion is composed of particles having a diameter of 1 µm or more.
A transparent panel that collectively covers the plurality of protrusions;
5. The optical element according to claim 1, wherein the light absorbing portion is formed in a region of the transparent panel that faces the plurality of protruding portions. .
An image display device using the optical element according to any one of claims 1 to 5.