Optical element with a microprism structure for deviating light rays

The present invention particularly relates to an optical element provided with a microprism structure for use as a cover for a light emitting device according to claim 1, and also relates to a method for manufacturing the optical element according to claim 8.

As a result of using such an optical element, i.e., a light emitting device cover, for example, emission of light beams from the light emitting device in order to avoid or at least reduce any dazzling to the viewer. The angle should be limited. Further, of course, such elements provide mechanical protection for the light emitting device, in particular for the light source inside the light emitting device.

The above types of optical elements are known, for example, from Austrian Patent No. AT-B-404,403 (Patent Document 1). This known optical element used as a light emitting device cover has pyramidal portions, so-called microprisms, arranged in vertical and horizontal rows on the side facing the lamp, which are formed as truncated pyramids. It has an upper boundary surface (light incident surface) located parallel to the base (light emitting surface). All light emitting device covers are made of transparent or transparent material as a whole.

A truncated pyramid, or microprism, according to Japanese Patent No. AT-B-404,403 is shown in FIG. 1 to illustrate the problem to be solved by the present invention. As described in detail in this patent specification, the known microprism 1 has a top surface 2 that serves as a light incident surface and a bottom that is arranged parallel to the top surface and serves as a light emitting surface. It has 3 and a side wall 4 that extends diagonally so that the microprism takes the shape of a truncated pyramid. The emission angle γ of the emitted light beam with respect to the perpendicular line with respect to the light emitting surface 3 is preferably about γmax = 60 to 70 ° at the maximum in order to avoid any glare of the viewer when the light emitting device is viewed from the side. Makes γmax = 60 °. At the same time, in order to achieve the highest possible optical efficiency, the optimum ratio d: h of the dimensions of the truncated pyramid, which depends on the refractive index n of the truncated pyramid material, is compared to the microprism 1 made of transparent material. Appears. Furthermore, the optimum angle δ of the groove between the adjacent microprisms 1 of about 8 to 9 ° appears in the lattice size of the microprisms of about 700 μm.

Given the above parameters, even in the case of a light beam that directly hits the edge of the truncated pyramid 1 or hits the edge immediately adjacent to it and just passes through the edge 6 between the truncated pyramids 1. The light beam is emitted from the plane of the light emitting surface 3 at an emission angle of less than 60 ° (γ <60 °).

However, from the point of view of manufacturing technology, it has actually been found that it is extremely difficult or almost impossible to observe the groove angle δ of about 8 to 9 °. Currently, a groove angle δ of about 15 ° can be achieved at a sufficiently high level of accuracy and reproducibility. Even if the actual groove angle δ 15 °, assuming that the height h of the truncated pyramid 1 is constant, an emission angle of γmax 60 ° can be achieved, but as a result, the light incident surface 2 Since the area is thus reduced, the optical efficiency of the light emitting device cover is correspondingly reduced from approximately 75-80% to approximately 65%. As a modification, the height h of the truncated pyramid 1 can be reduced in order to maintain the spread of the light incident surface 2. However, in this case, the maximum light emission angle γmax = 60 ° is no longer observed. This is because light rays that are directly incident at the edge 5 of the light incident surface 2 and that have just passed through the edge 6 between the adjacent truncated pyramids 1 leave the light emitting device cover at a flatter angle. is there.

Yet another light emitting device cover of the type mentioned in the introduction, i.e., yet another optical element, is known, for example, from WO 97/36131 (Patent Document 2). The microprism structure disclosed in this patent specification, on the one hand, is on the side wall of a truncated prism to prevent light from exiting the side wall of the microprism and reducing the efficiency of the light emitting device configuration. It has a reflective cover and, on the other hand, has a lens system on the side of the light emitting surface of the microprism to focus the light rays in a direction substantially perpendicular to the plane of the light emitting surface. There is. However, the structure of this light emitting device cover is relatively complex and is therefore more expensive in terms of manufacturing technology compared to the light emitting device cover known from Japanese Patent No. AT-B-403,403.

<p><patcit num="1"><text>Austrian Patent No. AT-B-404,403</text></patcit><patcit num="2"><text>International Publication No. 97/36131</text></patcit></p>

<p> Based on the above-mentioned problems of consideration of the prior art, an object of the present invention avoids the above-mentioned drawbacks in the case of the prior art, and particularly at a high degree of efficiency, the dazzling of the viewer is avoided from the viewpoint of the lighting technique. It is an object of the present invention to provide an optical element of the above type that secures an emission angle of such a light beam.</p>

<figref num="1">It is sectional drawing of the microprism structure of a light emitting device cover known from the prior art.</figref><figref num="2">It is the schematic perspective view of the Example of the 1st good example of the optical element by this invention.</figref><figref num="3">It is the schematic perspective view of the Example of the 2nd good example of the optical element by this invention.</figref><figref num="4">It is the schematic perspective view of the Example of the 3rd good example of the optical element by this invention.</figref><figref num="5">2 is a cross-sectional view of a first preferred embodiment of the microprism structure according to the invention along line AA of FIG. 2 or FIG.</figref><figref num="6">It is sectional drawing of the example of the 2nd good example of the microprism structure by this invention.</figref><figref num="7">It is sectional drawing of the example of the 3rd good example of the microprism structure by this invention.</figref><figref num="8">It is sectional drawing of the example of the 4th good example of the microprism structure by this invention.</figref><figref num="9">It is sectional drawing of the 5th preferable example of the microprism structure by this invention.</figref><figref num="10">FIG. 5 is a cross-sectional view of a sixth preferred embodiment of the microprism structure according to the present invention.</figref><figref num="11">A It is a figure which shows the path of a light ray passing through a conventional optical element. B It is a figure which shows the course of a plurality of good examples light rays passing through an optical element by this invention.</figref>

This object is achieved by an optical element having the characteristics of claim 1. The light incident surface of the optical element composed of the top surface of the microprism is formed in a convex or concave shape continuously or discontinuously, so that the light beam coming from the lamp is separated from the light emitting surface. It hits the light incident surface of the element at an incident angle different from that in the case of the light emitting surfaces aligned so as to be parallel. Depending on the material of the element core, especially as a result of the appropriate selection of curvature or degree of curvature, which is determined by its index of refraction, the light beam will be directed against the perpendicular of the light emitting surface without reducing the degree of efficiency of the optical element in terms of lighting technology. It is only possible to emit light from the light emitting surface at an emission angle of about 60 ° at the maximum. Due to the concave shape of the top surface of the microprism, the light rays that hit the top surface are refracted into the microprism structure at a steeper angle, but do not leave the optics at an angle that is too flat. On the other hand, due to the convex formation of the top surface of the microprism, the rays that collide with the top surface at a flat angle are refracted into the microprism structure at a flatter angle and therefore reflected at the slopes of the opposing structures. And leave the optics at a sufficiently small emission angle.

The formation of the top surface of the microprism is preferably achieved by convex or concave curvature, or step formation, and the curvature or step formation does not necessarily have to extend over the entire top surface.

The plate-like core of an optical element according to the invention is either machined from a transparent block or manufactured by injecting or injecting a transparent material into a suitable mold and then applying pressure to it.

Yet another advantageous configuration and yet other developments of the present invention constitute the gist of the dependent claims.

<p> Various preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.</p><p> 2 to 4 show, for example, three different optical elements 10, 10', 10'' used as a light emitting device cover in a perspective view from the side of the light emitting device facing the lamp (not shown). .. The optical elements 10, 10', 10'' consist of a transparent plastic material, such as a light-transmitting or transparent material such as acrylic glass. Each of the optical elements 10, 10', 10'' consists of a plate-shaped core 11, 11', 11'' made of a transparent material, one side of which is occupied by a plurality of microprisms 12, 13. In this regard, the microprisms 12 and 13 are formed so as to start at their bottom 15 and taper to form a groove 22. In this case, all of the top surfaces 14 of the microprisms 12 and 13 form the light incident surface of the optical element, and the other side 21 of the core constitutes the light emitting surface of the optical element.</p><p> The element cores 11, 11', 11'' of the optical elements 10, 10', 10'' are manufactured by various methods from a transparent material, preferably a transparent plastic material such as acrylic glass, according to the present invention. be able to. First, the production by the so-called injection molding embossing method will be described here. This method is generally known, but is similar to the plastic injection molding method performed at a relatively low injection pressure. After injecting the transparent material into the mold, mechanical pressure is applied to the liquid material so that it can still penetrate the structure of the mold. It is also possible to manufacture the element core 1 by a hot embossing method in which the transparent material in liquid form is poured into an appropriate mold and then pressure is applied to the transparent material in the same manner to achieve embossing.</p><p> Furthermore, it is also possible to mechanically provide a groove in the transparent plastic block. This can be done, for example, by cutting with a diamond cutter or by a laser beam.</p><p> Further, it is possible to manufacture transparent cores 11, 11', 11'' by pressing a liquid plastic material through an extrusion head. In this case, it is only possible to manufacture the linear structure of the microprism 13.</p><p> In the first preferred embodiment of FIG. 2, the optical elements 10 are arranged in vertical and horizontal rows on the side of the light emitting device facing the lamp in the form of microprisms 12 having the same dimensions and having a square base. It has a contoured part. These microprisms 12 correspond to one of the preferred embodiments further described below, as shown in FIGS. 5-10, as their shape corresponds to FIG. 2, as well as FIGS. 3 and 4. It is only outlined. As a result of arranging the microprisms 12 of the first preferred example of the optical element in a matrix, crossed dazzling suppression is achieved in both directions.</p><p> In the first good example of the optical element 10, the microprisms 12 are directly connected to each other in vertical and horizontal rows one after another, but the micro in the second good example of the optical element 10'shown in FIG. The prisms 12 are arranged like a checker board, i.e., in each case, one microprism structure is omitted between the two successive microprisms 12 in the column and row directions, leaving them free. The regions correspond to the base region of one microprism 12 in terms of its length and width. The microprisms in this second preferred example also preferably have a square base. However, in both the first and second preferred embodiments, it is possible to provide a different polygon, preferably a regular polygon, as the base.</p><p> In a third preferred embodiment of the optical element according to FIG. 4, the microprism 13 of the optical element 10 extends in one direction, eg, in the column direction, over the entire length of the optical element 10 , but in the other direction. For example, in the row direction, as in the case of the optical elements 10 and 10'in FIGS. 2 and 3, the microprisms 13 are arranged so as to be continuous with each other, which is the same as the embodiment of the above two good examples. Is different. Similar to the second preferred embodiment, it is possible to omit each row between the two microprism structures 13.</p><p> As a result of the microprisms 13 extending linearly, only dazzling suppression intersecting at right angles to the extension direction of the microprisms 13 is achieved. Therefore, the optical element 10 according to the third preferred embodiment is particularly suitable for a light emitting device using an elongated lamp such as a fluorescent tube. In this case, the length direction of the lamp is parallel to the extension direction of the linear microprism 13.</p><p> Moreover, as shown in FIG. 4, the gap between the adjacent microprisms 13 is preferably covered with a reflective material 20, for example, a metal foil having a high reflective force. As a result, only the light from the lamp that hits the top surface 14 of the microprism 13 that constitutes the light incident surface is radiated through the optical element 10''. Light rays that collide with the cover 20 are reflected back into the light emitting device, and are normally reflected by a reflector placed behind the lamp and back in the direction of the optics.</p><p> As a result of using such a reflective cover 20, it is possible to further improve the efficiency of the optical element. Instead of the cover 20 partially shown in FIG. 4, it is also possible to completely fill the gap or groove 22 between the microprisms 13 with a reflective material. As described above, the side wall portions 16 of the microprisms 13 are formed so as to be totally reflective so that the light rays that collide with the side wall portions 16 from the inside cannot leave the microprisms 13. As an example of this modification, the side wall portion 16 of the microprism 13 may be coated with a reflective material, or may be formed to be reflective in a different manner.</p><p> With reference to the example of the optical element 10'' in FIG. 4, the means described here can of course be applied in the same manner as in the case of the first two good examples of FIGS. 2 and 3. 5 to 10 show examples of different good examples of microprisms 12 and 13 in cross section along line AA of FIG. 2 or FIG. The microprisms 12 and 13 described below can be selectively used for the optical elements 10, 10'and 10'' of FIGS. 2 to 4.</p><p> The microprism structures 12 and 13 shown in cross section in FIG. 5 are arranged so as to be substantially parallel to the bottom 15 which substantially constitutes the light incident surface 21 of the optical element. Moreover, it has a top surface 14 that constitutes a light emitting surface. The side surfaces 16 of the microprisms 12 and 13 extend slightly inward in an inclined manner that slopes from the bottom 15 to the top 14 so as to form an outwardly tapered structure. This tilt angle δ / 2 of the side surface 16 determines the groove angle δ between the adjacent microprisms 12 and 13 of the optical elements 10, 10'and 10''. The microprisms 12 and 13 preferably have a square or rectangular shape, but may be any other polygon, preferably a regular polygon.</p><p> The light incident surface 14 of the microprisms 12 and 13 in the first preferred example of FIG. 5 is concave, that is, curved inward. The required degree of curvature is determined by the dimensions of the microprisms 12 and 13, more precisely the ratio d: h and the index of refraction n of the transparent material of the microprisms 12 and 13. However, those skilled in the art of optics will be able to easily determine the degree of curvature of the light incident surface 14 required in each case to obtain a maximum light incident angle γmax of about 60-70 °. The effect of the curved light incident surface 14 will be described in more detail with reference to FIGS. 11A and 11B.</p><p> The second good example of the microprisms 12 and 13 shown in FIG. 6 is different from the first good example in that the light incident surface 14 is convex, that is, curved outward. different.</p><p> Instead of the concave or convex curved light-incident surface 14, it is also possible to provide a stepped or edged light-incident surface 14 as shown in the preferred examples of FIGS. 7-10.</p><p> In the case of the two good examples of FIGS. 7 and 8, the light incident surface 14 is composed of a partial surface that tapers in the center below or above its (virtual) plane and thus has a subsidence structure. Or it constitutes a raised structure. For example, if the base of the microprism 12 is square, these partial planes of the light incident surface 14 are triangular.</p><p> In the fifth and sixth preferred embodiments of FIGS. 9 and 10, the light incident surface 14 is similarly composed of a plurality of partial surfaces. One partial surface should be substantially parallel to the (virtual) plane of the light emitting surface 15 and the light incident surface 14 at the center of the light incident surface 14 and below or above the (virtual) plane of the light incident surface 14. Have been placed. The other partial surface connects the central partial surface to the side wall portion 16 of the microprisms 12 and 13.</p><p> Of course, within the scope of the present invention, it is possible to select a combination of examples of microprisms described with reference to FIGS. 5 to 10, and even more similar configurations. In this regard, the top surface 14 is continuously or discontinuously formed in a concave or convex shape, i.e., always concave or convex in at least one subregion thereof.</p><p> 11A and 11B show the effect of the configuration of microprism structures 12, 13 according to the invention on the mode of operation of the optical elements 10, 10', 10'' as compared to conventional microprism structures 12, 13. Will be described below with reference to.</p><p> First of all, the conventional optical elements are shown in cross section in FIG. 11A. The groove angle δ between the adjacent microprisms 1 is about 15 °, the lattice size d of the microprisms 1 is 700 μm, and the width of the light incident surface 2 of the microprisms is about 540 μm, resulting in a ratio d: h. Is about 7:12. As an example, the incident ray 17 is shown in FIG. 11A, which directly hits the light incident surface 2 of the microprism structure 1 at the edge 5 at a flat incident angle. Due to the relatively high index of refraction n of the transparent material of the optical element, the light beam 17 is refracted toward the perpendicular to the light incident surface 2. The refracted light beam 17'passes through the edge 6 between the adjacent microprisms 1 and inside the core of the optical element, and hits the light emitting surface 3 or the extension of the light emitting surface at the base. On the light emitting surface, the light beam 17'is refracted on the light emitting surface in a direction away from the perpendicular to the light emitting surface 3 due to the relatively low refractive index in the surrounding region. The light beam 17 emitted from the optical element has an emission angle γ that is greater than the desired maximum emission angle γmax of approximately 60 °. Therefore, in the case of conventional optical elements, dazzling to the viewer cannot be completely eliminated.</p><p> In contrast to the conventional optical element of FIG. 11A, the optical element according to the invention of FIG. 11B has a microprism 12 having a concave light incident surface 14 and a convex light incident surface 14. , 13 are shown in the drawing. As an example, in each case, two light rays 18 hitting the edge of the light incident surface 14 formed in a concave shape and two light rays 19 hitting the edge of the light incident surface 14 formed in a convex shape are shown. .. Moreover, a reflective cover 20 is provided in the groove 22 between the microprisms 12 and 13.</p><p> A ray 18 that collides with a concave or submerged light incident surface 14 in the edge region, taking into account the different incident angles to the light incident surface compared to the beam path shown in FIG. 11A. Is refracted to a large extent toward the perpendicular to the (virtual) plane of the light incident surface, so that the light rays 18'extending in the cores 11, 11', 11'' of the optical elements 10, 10', 10'' It hits the light emitting surface 21 or the core 11, 11', 11'' of the micro prisms 12 and 13 at a steep angle. These light rays 18'are also refracted in a direction away from the perpendicular to the light emitting surface 15, but the emission angle γ in this case does not exceed the maximum emission angle γmax of 60 °.</p><p> On the other hand, due to the convex or raised formation of the light incident surface 14, the light beam 19 that collides with the light incident surface 14 at the edge region at a flat angle compared to the path of the beam shown in FIG. 11A is light. Since it is not so refracted toward the perpendicular to the (virtual) plane of the incident surface, the light ray 19'hits the side surface 17 of the microprisms 12 and 13 and is all reflected there. As a result, even the ray 19'hits the light emitting surfaces 21 or cores 11, 11', 11'' of the microprisms 12 and 13 at a steeper angle compared to the path of the beam shown in FIG. 11A, thus the ray 19'. 'Can leave the optical element at a sufficiently small emission angle γ.</p>

10, 10', 10'' optical elements 11, 11', 11'' Plate core 12,13 Micro prism 14 Top surface of microprism 22 groove