JPWO2018139141A1 - Optical element and image display device using the same - Google Patents

Abstract

The optical element suppresses stray light that does not contribute to the imaging of a real mirror image to improve the contrast of the image, and suppresses irregular reflection of light between the dihedral corner reflectors to reduce white blur. The optical element 1 includes a base 2 formed of a transparent material and forming a plane, and a plurality of protrusions 3 integrally formed so as to protrude from the base 2. Adjacent vertical surfaces 31 and 32 of the side surfaces forming the protruding portion 3 form a dihedral corner reflector 30 that is substantially orthogonal to each other. A low-refractive-index portion 4 made of a medium having a refractive index lower than the refractive index of the transparent material forming the projecting portions 3 and a light guided between the projecting portions 3 are provided between the projecting portions 3. And a light absorbing portion 5 for absorbing light. The low refractive index portion 4 is in contact with the dihedral corner reflector 30.

Description

  The present invention relates to 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 a video display device using the same.

  An optical element has been proposed 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 one surface side. . As this type, there is known an optical element having a structure in which a plurality of dihedral corner reflectors each composed of two minute mirror surfaces (reflection surfaces) orthogonal to each other are collectively planarized (for example, Patent Document 1). 1).

  Patent Document 1 discloses an optical element having a dihedral corner reflector array in which a plurality of dihedral corner reflectors are arranged in a grid on one 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, light emitted from the object to be observed arranged on one side of the element surface is reflected twice by the dihedral corner reflector when passing through the optical element, and is bent, and the other surface without the object to be observed is bent. An image is formed in the space on the side as a real image. Thus, the real image is formed such that the object to be observed exists at a symmetric 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 cubic protrusions protruding from the surface of the base are arranged, and the inner wall of the protrusion is a mirror surface, and the total reflection of light on the inner wall is used. To form a real mirror image. Here, a protrusion is formed by providing a lattice-like groove between adjacent protrusions (two-sided corner reflectors). In such a configuration, part of the light incident on the substrate is guided to the groove side without entering the protruding portion. Further, 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 which does not contribute to the imaging of the real mirror image, and lowers the contrast of the stereoscopic image. Further, since the groove between the dihedral corner reflectors is minute, on the order of μm, when ambient light such as external illumination light enters the groove, the light is irregularly reflected by the groove and causes white blur.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and suppresses stray light that does not contribute to imaging of a real mirror image, improves contrast of a stereoscopic image, and suppresses irregular reflection of light between a plurality of dihedral corner reflectors. It is another object of the present invention to provide an optical element capable of reducing white blur and a video display device using the same.

  In order to solve the above problems, the present invention is directed to an optical element for forming a real image of an object to be observed on one surface side in a space on the other surface side, wherein the substrate is formed of a transparent material and forms a plane. And a plurality of protrusions formed integrally with the base so as to protrude from the base, wherein the protrusions have three or more side surfaces that are angled with respect to the base. The two adjacent surfaces of the side surfaces are perpendicular to the base and substantially orthogonal to each other, and form a dihedral corner reflector that reflects light emitted from the object to be observed. A low-refractive-index portion made of a medium having a refractive index lower than that of the transparent material forming the protruding portion; and a light-absorbing portion for absorbing light guided between the plurality of protruding portions. And the low refractive index portion is in contact with the dihedral corner reflector. The features.

  In the above optical element, the low refractive index portion preferably has a thickness of 1 μm or more from the surface of the dihedral corner reflector.

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

  In the above-mentioned 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 protrusions, and the light absorbing unit is formed in a region of the transparent panel that faces the plurality of protrusions. Is preferred.

  Preferably, the optical element is used in a video notation device.

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

FIG. 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 imaging mode by the said optical element. FIG. 2 is an enlarged perspective view of a part of the optical element. (A) is a side view of the optical element, and (b) is a top view. FIG. 4 is a side view for explaining the operation of the optical element. (A) and (b) are side views for explaining a configuration and a method of forming the optical element according to a first modification. (A) is a side view for explaining a configuration and a method of forming the optical element according to a second modification, and (b) is an enlarged view of a dashed-dotted line area of (a). FIG. 9 is a side view for explaining a configuration according to a third modification of the optical element and a method for forming the same. FIG. 14 is a side view for describing a configuration according to a fourth modification of the optical element and a method for forming the same. FIG. 2 is a perspective view conceptually showing a configuration example of a video display device including the 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 has a dihedral corner reflector 30 composed of mirror surfaces (vertical surfaces 31 and 32) that are perpendicular to the substrate 2 and substantially perpendicular to each other. The plurality of dihedral corner reflectors 30 are arranged in a grid on one plane of the base 2 to form a dihedral corner reflector array 30S.

  When the object O is arranged on one surface of the optical element 1, the optical element 1 forms a real image (real mirror image P) of the object O in the space on the other surface of the element surface 1 S of the optical element 1. Image. That is, the optical element 1 forms a real mirror image P of the observation object O at a plane symmetric position having the element surface 1S as a plane of symmetry. Here, the element surface 1S refers to a virtual plane orthogonal to the two vertical surfaces 31 and 32 constituting the dihedral corner reflector 30. Incidentally, the dihedral corner reflector 30 is minute, on the order of μm, compared to the entire size of the optical element 1 on the order of cm or m. In FIG. It is conceptually shown in a letter shape.

  An image forming mode by the dihedral corner reflector array 30S will be described with reference to FIGS. In FIG. 2A, light emitted from a point light source o as an object to be projected is assumed to travel three-dimensionally from the back side of the paper to the front side of the paper. Light (solid arrow) emitted from the point light source o is reflected by one mirror surface (vertical surface 31) of the dihedral corner reflector 30 when passing through the optical element 1 (omitted in FIG. 2A). Then, after being reflected by the other mirror surface (vertical surface 32), the light passes through the element surface 1S (see FIG. 2B). The light (dashed-dotted arrow) emitted from the optical element 1 in this way passes while spreading at the plane symmetric position p of the point light source o with respect to the element surface 1S. That is, the transmitted light of the optical element 1 is focused on the plane symmetric position p of the point light source o with respect to the element surface 1S, and forms an image as a real mirror image P (see FIG. 1).

  As shown in FIGS. 3 and 4A and 4B, the base 2 is formed of a transparent material and forms one plane. The optical element 1 has a plurality of protrusions 3 formed to protrude from the base 2. The plurality of projections 3 are formed integrally with the base 2 using the same transparent material as the base 2.

  The protrusion 3 has three or more side surfaces that are angled with respect to the base 2. The projecting portion 3 of the present embodiment has a truncated pyramid shape, and includes two surfaces perpendicular to the substrate 2 (vertical surfaces 31 and 32) and two surfaces inclined with respect to the substrate 2 (inclined surfaces 33 and 34). And a top surface 35 parallel to the base 2. Among the side surfaces, two surfaces of the vertical surfaces 31 and 32 are adjacent to each other, and two surfaces of the inclined surfaces 33 and 34 are adjacent to each other. The vertical surfaces 31 and 32 are arranged so as to be substantially orthogonal to each other. The light (solid arrows in FIG. 4A) incident on the protrusion 3 from the base 2 is totally reflected twice on the inner wall surfaces of the vertical surfaces 31 and 32, and exits from the upper surface 35 of the protrusion 3.

  The upper surface 35 is defined by the ridge lines of the vertical surfaces 31 and 32 and the inclined surfaces 33 and 34, and their lengths are substantially equal, and are substantially square when viewed from above (see FIG. 4B). In a side view (see FIG. 4B), the vertical surface 31 (32) has a boundary line (dotted line in FIG. 4A) with the base 2 as a lower base, an ridge line with the upper surface 35 as an upper base, and an inclined surface. The trapezoid has a ridge line with 33 and 34 as a hypotenuse, and a 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, in the plurality of projecting portions 3, the lattice-shaped grooves 21 are formed between the opposing vertical surfaces 31, 32 and the inclined surfaces 34, 33, respectively. In addition, a plane parallel to the base 2 is formed between the opposing side of the vertical surface 32 (31) on the base 2 side and the side of the inclined surface 33 (34) on the base 2 side. Is formed.

  In addition, the optical element 1 is connected to the groove 21 between the plurality of protrusions 3 and to the low refractive index portion 4 made of a medium having a refractive index lower than the refractive index of the transparent material forming the protrusion 3 and the groove 21. And a light absorbing portion 5 that absorbs the waved light. The low-refractive-index portion 4 is in contact with at least vertical surfaces 31 and 32 forming a dihedral corner reflector.

  A transparent material having a light transmittance of 80% or more, a refractive index of 1.3 or more, and having little deterioration due to heat or humidity is used for the medium of the base 2 and the protrusions 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 absorptivity and being amorphous and having an alicyclic structure. Examples of the cycloolefin polymer include ZEONOR (registered trademark) (grade: 1020R, light transmittance 92%, refractive index 1.53) manufactured by Zeon Corporation. In addition, in order to reduce the critical angle in the vertical surfaces 31 and 32 to facilitate the total reflection, the low refractive index portion 4 preferably has a medium having a refractive index of 1.4 or less. The medium of the low refractive index section 4 is air.

  In manufacturing the optical element 1 of the present embodiment, first, a part excluding the low refractive index part 4 and the light absorbing part 5, that is, a dihedral corner reflector array 30S including the base 2 and the plurality of protrusions 3 is manufactured. You. Examples of a method for producing the two-sided corner reflector array 30S include a method of injection molding a translucent resin using a mold such as a stamper, or a hot press molding method. The mold is manufactured by, for example, a method of forming a shape corresponding to the shapes of the protrusions 3 and the grooves 21 (see FIG. 3) on a metal master plate by nano-machining, and then inverting the beads. Further, for example, by using the X-ray lithography method, the protrusion 3 and the groove 21 having four side surfaces can be directly formed 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 projection 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 protrusions 3. According to such a shape, a so-called “draped taper” can be added to the protruding portion 3 which is a fine structure on the order of μm, and when the dihedral corner reflector array 30S is formed by die 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 of the protrusion 3 including the groove 21 at one pitch in a top view is, for example, 100 to 700 μm (see FIG. 4B). Note that the pitch width W is set according to the projection distance of the real mirror image P (see FIG. 1). For example, when the projection distance is 10 cm, the pitch width W is set to about 280 μm. The plate thickness of the optical element 1 including the base 2 and the protrusion 3 is generally 1 to 3 mm. The height H (depth of the groove 21) from the base 2 (the bottom surface 22 of the groove 21) to the protrusion 3 is set to be equal to or larger than the pitch width W.

  The inclination angle θ of the inclined surfaces 33, 34 with respect to the normal line of the base 2 is preferably 5 to 25 ° (see FIG. 4A). By setting the inclination angle θ to 5 ° or more, a necessary taper can be secured, and detachment from the mold at the time of manufacturing the two-sided corner reflector array 30S can be facilitated. 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 dihedral corner reflector 30 depends on the height H of the projection 3. And it is possible to suppress the real mirror image P from becoming dark. It is assumed that the height H of the projection 3 is 300 μm, the width W of one side of the projection 3 at one pitch in a top view 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. Note that the numerical values shown here are representative values shown as an example of the present embodiment, and the present invention is not limited to these numerical values.

  The optical element 1 of the present embodiment is obtained by further forming a low refractive index part 4 and a light absorbing part 5 on the dihedral corner reflector 30 manufactured as described above. For the light absorbing section 5, for example, black ink or particulate pigment is used. 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 such that a 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 accounts for 50% or more of the entire area of the vertical surfaces 31 and 32. It should just be done. When light is totally reflected by the vertical surfaces 31 and 32 forming the dihedral corner reflector 30, if a medium having a high refractive index is provided outside the vertical surfaces 31 and 32 at an interval of about the wavelength of light, an evanescent wave Light may be transmitted through the inner surface of the vertical surfaces 31 and 32 to suppress total reflection. Therefore, the low-refractive-index portion 4 having a thickness of 1 μm or more is arranged at least 50% of the total area of the vertical surfaces 31 and 32 in a region where the evanescent wave can seep outside the vertical surfaces 31 and 32. Thus, a decrease in the total reflection efficiency can be suppressed, and a decrease in the luminance of the real mirror image P can be prevented.

  As a method of 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 to the inclined surface 33 (34) and the bottom surface 22 of the groove 21 by micro inkjet printing. Is mentioned. In this manner, 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 side of the vertical surface 31 (32) where no ink is applied. The space where this air exists becomes the low refractive index portion 4. In addition, as long as there is no problem in practical use, uneven coating may be applied to the inclined surface 34 (33) or the groove 21, and some ink may be attached to the vertical surface 31 (32).

  In the optical element 1 produced in this manner, as shown in FIG. 5, the low refractive index portion 4 is in contact with the vertical surface 32 (also the vertical surface 31) forming the dihedral corner reflector 30. The difference in the refractive index from the medium that constitutes No. 1 increases. Therefore, the critical angle in the vertical plane 32 is reduced, and light having a small incident angle α (solid arrow in the figure) that is not totally reflected without the low refractive index portion 4 can be totally reflected, and the total reflection is achieved. Efficiency is improved. As a result, the real mirror image P can be brightened.

  Further, since the light absorbing portion 5 is provided between the projecting portions 3, of the light incident on the base 2, the light is guided from the bottom surface 22 to the groove 21 side without entering the projecting portion 3. Light (dashed arrow in the figure) is cut by the light absorbing portion 5. In addition, the light incident on the vertical surface 32 at an angle smaller than the critical angle and transmitted through the groove 21 (dashed line in the figure) is also cut. As described above, since the light guided to the groove 21 is cut by the light absorbing portion 5, it is possible to suppress the generation of stray light that does not contribute to the imaging of the real mirror image P, and to reduce the contrast of the real mirror image P. Can be improved.

  The groove 21 between the dihedral corner reflectors 30 is minute, on the order of μm, and even if ambient light (two-dot chain arrow in the figure) such as external illumination light enters the groove 21, Since the absorbing portion 5 cuts the light, the light is not irregularly reflected by the fine grooves 21 and the occurrence of white blur can be suppressed.

  It is preferable that the light absorbing portion 5 is in contact with the side surface of the projecting portion 3 which does not form the dihedral corner reflector 30, that is, in the present embodiment, the inclined surfaces 33 and 34. Part of the light that enters the projection 3 from the base 2 may enter the inclined surfaces 33 and 34 instead of the vertical surfaces 31 and 32. This light also does not contribute to the imaging of the real mirror image P, and when guided to the groove 21 side, becomes stray light that lowers the contrast of the real mirror image P. Therefore, by arranging the light absorbing portion 5 so as to be in contact with the inclined surfaces 33 and 34, the light guided to the groove 21 can be cut.

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

  As a first modified example, as shown in FIG. 6A, a removable sealing material Rm having a thickness of 1 μm is previously formed on the vertical surface 32 (31), and the groove 21 is formed of the light absorbing material Am. After the filling and curing of the filled light absorbing material Am, a forming method of removing the sealing material Rm is given. 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 has been formed. The light-absorbing material Am, which becomes the refractive index portion 4 and is filled except for the gap, becomes the light-absorbing portion 5. As a forming method, for example, a method in which the light absorbing material Am is not dissolved, and the sealing material Rm is removed by immersing the light absorbing material Am in a predetermined solvent in which the sealing material Rm is dissolved is used.

  Also in the first modification, 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. Further, since the light absorbing portions 5 are provided between the protruding portions 3, stray light can be suppressed and the contrast of the real mirror image P can be improved. Furthermore, in the first modified example, since the ratio of the light absorbing portion 5 occupying the groove 21 is larger than that in the configuration example shown in FIG. 5, it is possible to prevent environmental light such as illumination light from being incident on the groove 21 itself. And the occurrence of white blur can be effectively suppressed.

  As a second modified example, as shown in FIG. 7A, a method of filling a substantially spherical light-absorbing particle 5s into a groove 21 between a plurality of projecting portions 3 can be mentioned. As the light absorbing particles 5s, for example, a 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 size of the light absorbing particles 5s is 1 μm or more, preferably 2 μm or more. The upper limit of the particle size of the light absorbing particles 5s may 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 of the groove 21.

  In the 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 only a few places where the light absorbing particles 5s and the vertical surface 32 (31) are in contact with each other. There are many gaps (air) between them. Therefore, this gap functions as the low refractive index portion 4. 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 forming the dihedral corner reflector 30 is 50% or more of the entire area of the vertical surfaces 31 and 32. The thickness of the low refractive index portion 4 may be partially less than 1 μm. According to the second modification, the low refractive index portions 4 and the light absorbing portions 5 are formed by a simple method of filling the grooves 21 between the plurality of projecting portions 3 with the substantially spherical light absorbing particles 5s. can do. Further, similarly to the above configuration example, stray light not contributing to the imaging of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and irregular reflection of light between the plurality of dihedral corner reflectors 30 is suppressed. White blur can be reduced.

  As a third modified example, as shown in FIG. 8, the transparent panel 6 further includes a transparent panel 6 that covers the plurality of protrusions 3 collectively. For example, there is a method of forming in a region facing the groove 21 between the three. For the transparent panel 6, glass, acrylic resin, glass, and a transparent material are used.

  In this forming method, for example, the pattern of the groove 21 between the plurality of protrusions 3 is scanned, and the same pattern is printed on the transparent panel 6 with a light absorbing material (ink), and the plurality of protrusions 3 are printed. After precise positioning with the groove 21 between them, they are bonded together. Note that the print pattern may be slightly different from the actual groove pattern as long as there is no problem in practical use, and there may be some misalignment during bonding. For example, the width of the printed groove pattern may have an error of about ± 20 μm as compared with the actual width of the groove 21, and the positional deviation at the time of bonding may be about ± 20 μm.

  In the third modification, a space surrounded by the grooves 21 between the plurality of protrusions 3 and the light absorbing portions 5 formed on the transparent panel 6 becomes the low refractive index portions 4. In the third modified example as well, as in the above configuration example, and similarly to the above configuration example, stray light not contributing to the imaging of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and a plurality of images are obtained. Diffuse reflection of light between the dihedral corner reflectors 30 can be suppressed, and white blur can be reduced.

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

  In the fourth modification, as shown in FIG. 9, 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 4 of the protruding portion 3 is formed. 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 object O (see FIG. 1) in the direction facing the inner angles of the vertical surfaces 31 and 32 is reflected twice by the vertical surfaces 31 and 32. Then, the real mirror image P is formed. On the other hand, in the fourth modified example, light from the opposite direction to the inner angle of the vertical surfaces 31 and 32 is reflected by the dihedral corner reflector of the vertical surface 36 and a vertical surface (not shown) perpendicular to the vertical surface 36. Thus, a real mirror image can be formed.

  Next, an image display device according to an embodiment of the present invention will be described with reference to FIG. The image display device 10 specifically applies the optical element 1 described above, and includes a box 12 having an opening 11 on an upper surface, and an image 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 image display unit 13 uses, for example, a liquid crystal display device. In the illustrated example, the character “A” is displayed in an inverted posture in which the character “A” is 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 character “A”. The observer can visually recognize the real mirror image of the character “A” as an aerial image when looking into the optical element 1 with the viewpoint Ep placed diagonally above the image display device 10.

  The present invention is not limited to the above embodiment and various modifications, and various modifications are possible. In the above embodiments and modifications, 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 for emitting light. For example, the shape may be a truncated triangular pyramid or a truncated pyramid having five or more angles. The light absorbing portion 5 is not necessarily limited to the above-described configuration example as long as the light absorbing portion 5 exists between the plurality of protrusions 3 so that the low refractive index portion 4 is formed between the light absorbing portion 5 and the vertical surfaces 31 and 32. I can't. The low refractive index portion 4 is most preferably made of air having a low refractive index as a main medium. However, a light-transmitting resin, hollow silica particles, or mesoporous resin having a refractive index lower than that of the projection 3 itself is used. Silica particles and the like may be appropriately applied.

DESCRIPTION OF SYMBOLS 1 Optical element 10 Video display apparatus 2 Base 3 Projecting part 30 2-sided 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 particles (particles)
6 Transparent panel

Claims (6)

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,
A base formed of a transparent material and forming a plane, 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 that are angled with respect to the base,
Two adjacent surfaces of the side surfaces are perpendicular to the base and substantially orthogonal to each other, and form a dihedral corner reflector that reflects light emitted from the object to be observed.
A low-refractive-index portion made of a medium having a refractive index lower than the refractive index of the transparent material forming the protruding portion, and absorbing light guided between the plurality of protruding portions, between the plurality of protruding portions. And a light absorbing part to be
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 a 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 projecting portion that does not form the dihedral corner reflector.   4. The optical element according to claim 1, wherein the light absorbing portion is formed of particles having a diameter of 1 μm or more. 5. Further comprising a transparent panel that covers the plurality of protrusions at once,
The optical element according to claim 1, wherein the light absorbing portion is formed in a region of the transparent panel that faces between the plurality of protruding portions. .   An image display device using the optical element according to claim 1.

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