LIGHT DEFLECTOR

Abstract: When rays of light (L1, L2) coming from arbitrary dir­ ections strike the incidence surface (3) at one of the ends of a transparent glass or plastic deflector (2), they repeat total re­ flection on opposing reflection surfaces (5a, 5b) inside the deflector (2) and the angles which they make with the per­ pendicular to the reflection surfaces gradually approach a critical angle δ₀. Then the rays of light leave the deflector (2) from the outgoing surfaces (5a, 5b, 4) thereof and they come to possess directions of projection having an incremental component in the longitudinal direction of the deflector (2). Therefore, all the rays of light that strike the incidence surface (3) from all directions are provided with nearly the same dir­ ection of projection by passing them through the deflector (2). Typically, the deflector (2) has a wedge like plate form or a gimlet like form. Practically, a large number of deflectors (2) are juxtaposed with one another to form a board like assembly, and the rays of light are guided to strike one of the surfaces of the assembly.

Description: Technical Field The present invention relates to a device for changing the directions of light rays and, more particularly, to a device for receiving light rays from all directions and converting them into light rays within a predetermined range of direction. Background Art In the case of utilisation of light, such as sunlight, whose angle of incidence gradually changes, in order to attain an effective utilisation, a light source tracking device which is so controlled as to point to the direction of incident light is needed. When a light input or reception means is always maintained to point to the direction of incidence of light by the light source tracking device, the incident light can be received in a most effective manner. However, as the angle of incidence of, for example, sunlight gradually changes according to the season of the year and from the sunrise to the sunset, an effective light source tracking device must necessarily be complicated in construction and expensive and cannot be used practically. The present invention has been made to overcome the above and other problems encountered in the prior art and has for its object to provide a device for changing the directions of light rays, which is maintained stationary in the case of receiving light rays whose angles of incidence varies from time to time or light rays from any directions without the use of a light source tracking device and which can convert them into light rays within a predetermined direction range so as to facilitate the utilisation of the received light rays. FR-A-1184963 and JP-U-53127925 are hereby referred to. JP-U-53127925 discloses a wedge-shaped optical member through which light rays from a lamp are passed. Some light rays are internally reflected in the optical member and delivered to wheels for illumination. FR-A-1184963 discloses a device of a very similar nature to that of JP-U-53127925. In both cases the light rays from the lamp have substantially unified directions, so that no concept of unifying the direction of light rays having various directions is taught in these references. Disclosure of the Invention According to the invention there is provided an assembly for changing the directions of light rays, comprising a plurality of main bodies made of an optically transparent material and arranged side by side, each of the main bodies being of a wedge-shaped cross section gradually decreasing in transverse dimension from an end face at one end to another opposite end of the main body, said main body having said end face formed as a light incident surface and also having, between the end face and said opposite end, light reflecting surfaces for causing successive internal reflection, in the main body, of light rays which have entered into the main body through said light incident surfaces, said light reflecting surfaces being so oppositely inclined that when the light rays undergo the successive internal reflections by said reflecting surfaces, the directions of said successively internally reflected light rays are caused to have incident angles which at least reach a critical angle with respect to said reflecting surfaces, so that portions of said reflecting surfaces at which said successively internally reflected light rays reach angles equal to or smaller than said critical angle and surface portions adjacent to said portions constitute a light emerging surface through which said light rays are emitted, the light incidence surfaces of said plurality of main bodies being arranged in a parallel array and in coplanar relationship with each other; characterised by an auxiliary optical element which is made of an optically transparent material disposed closely adjacent to said reflecting surface of each of said main bodies, said optical element having a wedge-shaped cross section for changing the directions of light rays emerging from said light emerging surface, said optical element being oriented in such a manner that the transverse cross-sectional dimension of the element is gradually decreased in a direction from said opposite side toward said light incidence surfaces. The light rays which have entered through the incidence surface of the main body into the same are repeatedly internally reflected and, because of the profiles of the reflecting surfaces, the angle of each reflected light ray relative to a perpendicular is gradually increased and becomes equal to the critical angle or an angle slightly smaller that the critical angle When reaching such condition, the light rays are not reflected internally by the reflecting surface any longer, but refracted at the reflecting surfaces, thus being emitted out of the main body. Since the light rays are incident to the reflecting surfaces at angles close to the critical angle, they are refracted at the reflecting surfaces, being emitted from the main body substantially at a predetermined angle relative to the reflecting surfaces or the outer surface of the main body or being emitted within a predetermined angular range. As a result, the light rays emitted or emerging from the main body are almost in the same direction. Brief Description of the Drawings FIG 1 is a sectional view for explanation of a main body according to prior knowledge; FIG 2 is a perspective view thereof; FIG 3 is a view explanatory of the mode of operation of the arangement shown in FIG 1; FIG 4 is a perspective view of an assembly for changing the directions of light rays in which a plurality of main bodies as shown in FIG 2 are arranged in a parallel array; FIG 5 is an enlarged view illustrating a portion indicated by V in FIG 4; FIG 6 is a view explanatory of the behaviour of light rays incident on a light incidence surface; FIG 7 is a sectional view of a device for assisting the incidence of light rays; FIG 8 is a perspective view of a further explanatory arrangement not incorporating the invention; FIG 9 is a perspective view of a yet further explanatory arrangement; FIG 10 is a view explanatory of diverging angles of light rays emitted from a main body; FIG 11 illustrates auxiliary elements attached to a main body in accordance with the invention; FIG 12 illustrates modified auxiliary elements; FIG 13 is a partial view, on an enlarged scale, of FIG 12; FIG 14 illustrates yet further auxiliary elements; FIG 15 is a partial view, on an enlarged scale, of FIG 14; FIG 16 is a view explanatory of a phenomenon observed when a plurality of main bodies are assembled into a parallel array as shown in FIGS 4 and 5; FIG 17 is a sectional view, on an enlarged scale, of a further embodiment of a device for changing the directions of light rays in accordance with the present invention; and FIG 18 is a sectional view, on an enlarged scale, of a yet further embodiment of the present invention. Best modes for Carrying Out the Invention By way of explanation of known technology the device for changing the directions of light rays shown in FIG 1 has a main body 2 made of an optically transparent material such as a transparent glass, a transparent plastics or the like. The main body 2 is, for instance, in the form of a plate of wedge-shaped cross section as shown in FIG 2 and is gradually decreased in thickness from one side to the opposite side. An end surface 3 on one side of the main body 2 defines a light incidence surface, and a pair of opposing planes 5a and 5b which are extended from the light incidence surface 3 to an end surface 4 on the other side of the main body 2 define reflecting surfaces on which light rays which have entered the main body 2 through its light incidence surface 3 are reflected. The end surface 4 may be made very small in area or eliminated. When light ray L₁ is sent to the light incidence surface 3 of the main body 2 in the above described construction shown in FIG 1, it repeats internal reflections at points a , b , c , d and e on the reflecting surfaces 5a and 5b while propagating toward the end surface 4 and is finally emitted out of the main body 2 at a point f . In like manner, a light ray L₂ incident from a direction different from the direction of incidence of the light ray L₁ is repeatedly reflected internally at a 1, b 1, c 1, d 1 and e 1 and is finally emitted out off the main body 2 at a point f 1. These internal reflections of the light rays L₁ and L₂ are total reflection. Next the above-described phenomenon will be considered with reference to FIG 3. It is assumed that the angle between each of the reflecting surfaces 5a and 5b and the centre surface (optical axis) 0-0 of the main body be a and that an internally reflected light ray be incident at a point P on the reflecting surface 5b. When the angle between the internally reflected incident light ray and a perpendicular to the reflecting surface 5b at the point P is greater than the critical angle , the internally reflected light ray undergoes total reflection at the point P and is directed again to the opposing reflecting surface 5a. On the other hand, when the angle of incidence of the internally reflected light ray incident at the point P is equal to the critical angle , it is refracted and emerges parallel to and along the outer surface of the reflecting surface 5b at the point P. Furthermore, when the angle of incidence of the internally reflected light ray is smaller than the critical angle , it is emitted out of the main body 2 into the surrounding medium at an angle X in relation to the perpendicular as incidenced by the broken lines. As described above, the angle of incidence of a light ray striking the reflecting surface is small, the light ray is totally reflected at the reflecting surface and when the angle of incidence is gradually decreased and becomes equal to the critical angle, at least part of the light ray is refracted at the reflecting surface and emitted out of the main body 2 into the surrounding medium in parallel with the outer surface of the reflecting surface. Furthermore, when the angle of incidence is increased, it is refracted at the reflecting surface and emitted out of the main body 2 into the surrounding medium. When the material of the main body 2 has an index of refraction n1 and the atmosphere or medium surrounding the main body 2 has an index of refraction n2, the following relation is established. n1.sin( δ ₀-Δ δ ) = n2.sinX Meanwhile, whenever a light ray undergoes total reflection at the reflecting surface 5a or 5b, the angle of incidence of the totally reflected light ray arriving at the opposite reflecting surface 5b or 5a is decreased by 2 a so that the light ray incident at the reflecting surface becomes more and more upright relative to the reflecting surface, and when the angle of the light ray becomes smaller than the critical angle δ ₀ , at least part of the light ray is refracted at the reflecting surface and emitted out of the main body to the surrounding medium. It follows therefore that if an internal light ray is incident at the point P at an angle smaller than the critical angle δ ₀ by 2 a and is refracted totally at the reflecting surface and emitted into the surrounding medium as indicated by the broken lines in FIG 3, the following relation is established: n1.sin ( δ ₀ - 2 a ) = n2.sinX When the surrounding medium is air, n2 = 1 and when X = 90° - K, the following relation is obtained: n1.sin( δ ₀ - 2 a ) = sinX = sin (n/2 - X ) - cos X Hence, X = cos ⁻¹{ (n1.sin( δ ₀ - 2 a )} Therefore, when δ ₀ - 2 a < n/2 , the greater the value a , the greater the value X becomes. If the light ray is refracted not totally and emitted out of the main body and the light ray is partly reflected again even when the angle of incidence is smaller than the critical angle, the following relation is obtained: X = cos⁻¹{n1.sin( δ ₀ - 4 a )} As a result, the value X is increased more and more. As is apparent from the above explanation with reference to FIG 3, the light rays undergo total reflection at the points a b , c , d and e and the points a 1, b 1 c 1, d 1 and e 1 as shown in FIG 1 and when the angles of incidence of the light rays become equal to or smaller than the critical angle δ ₀ for the first time at the points f and f 1, respectively, the light rays are refracted and emitted out of the main body 2 to the surrounding medium. The light rays are emitted out of the main body 2 also through its end surface 4 to the surrounding medium. When light rays from all directions are incident on the incidence surface 3 and enter the main body 2 and when it is desired that the light rays emitted from within the main body through the reflecting surfaces 5a and 5b and the end surface 4 are in parallel or almost in parallel with the optical axis 0-0, it is preferable that the angle a is made as small as practicable, but when a is made small, the whole length L will be increased (FIG 2). In order to overcome this problem, the thickness d of the light incidence surface 3 (FIG 2) must be reduced as much as possible. When main bodies 2 having a thickness d made as small as possible are utilised, they are arranged in a parallel array as shown in FIGS 4 and 5 so that the light incidence surfaces of all the main bodies 2 define a large surface 3A. Then light rays which are incident on the large surface 3A from all directions are changed in directions of propagation within the main body and emitted out of the main body in directions almost perpendicular to the surface 3A. Next the input of light rays through the light incidence surface 3 into the main body 2 will be considered. It is assumed that the atmosphere or medium surrounding the main body 2 be the air with n2 = 1 and the main body 2 is made of an acrylic resin with n = 1.491. Then, since n1.sin δ ₀ = n2.sin 90° 1.491.sin δ ₀ =1.sin 90° Therefore, δ ₀ = sin⁻¹(sin 90°/1.491) = 42.12° Therefore, when viewed at a sectional plane, various light rays in air within an angular range of δ ₀ X 2 = 84.24° can enter the main body 2 and are transmitted therethrough by reflections at the reflecting surfaces 5a and 5b. FIG 7 shows a device not incorporating the invention for assisting the input of light rays into the main body 2 of the device for changing the directions of light rays. This device serves to reduce the quantity of said material of the main body 2 as much as possible so that the device for changing the directions of light rays can be made light in weight and fabricated economically. The device comprises mirrors 7 extended from the opposite sides of the light incidence surface 3, in such a way that they converge towards the incidence surface 3. Incident light rays from various directions are reflected by the inner surfaces of the mirrors 7 and directed to the incidence surface 3. As described above, the reflecting surfaces 5a and 5b are converged gradually in the direction away from the light incidence surface 3, but it is to be understood that the reflecting surfaces need not be opposing flat reflecting surfaces. In the non-inventive arrangement shown in FIG 8, a circular light incidence surface 3M is merged with a conical reflecting surface 5M so that a main body 2M is in the form of a frustum of cone. In the arrangement shown in FIG 9, a main body 2N is in the form of a hexagonal prism and the reflecting surfaces 5N are defined by the inclined surfaces of the hexagonal prism. In addition, any prism having any cross sectional configuration may be used. In both of the arrangements shown in FIG 8 and 9, a light ray enters through the light incidence surfaces 3M and 3N and undergoes repeated total internal reflections in a manner substantially similar to that described hereinbefore with reference to FIG 1 and is emitted out of the main bodies 2M and 2N. In this case, it should be noted that a light ray propagates along a three-dimensional path. In the above-described embodiments, the light rays which undergo successive total reflections inside the main body 2, 2M or 2N are emitted out of the main body with a diverging angle β as shown in FIG 10 so that the quantity of light rays in parallel with the optical axis is not so great. In order to overcome this problem, in accordance with an embodiment of the invention as shown in FIG 11, optically transparent auxiliary elements 9 each having a triangular cross sectional configuration are attached to the outside surface of a light emitting portion of the main body 2. The light rays which are emitted from the main body 2 with a wide diverging angle pass through thin air layers between the main body 2 and the auxiliary elements 9 and then are reflected or refracted at least once by the reflecting surfaces 10 or the auxiliary elements 9 after the light rays enter the latter whereby the directions of propagation of light rays are changed to those substantially in parallel with the optical axis when emitted from the main body 2. To this end, the reflecting surfaces 10 diverged rearwardly in the direction opposite to that of the light incidence surface 3. The reflecting surfaces 10 may be formed of reflecting films which, for instance, are fabricated by a vacuum deposition process using aluminium. The auxiliary elements 9 are made of solid material. Instead, only mirrors may be provided at the positions of the reflecting surfaces 10. In the case of providing the auxiliary elements 9 for the main body 2 of FIG 2, the elements are in the form of a plate of triangular cross section, while for the main bodies 2M, 2N of FIGS 8 and 9, they take the form of an annulus encircling the main body. Auxiliary elements 9M shown in FIG 12 are different from those shown in FIG 11 in that the surfaces of the auxiliary elements 9M which are made into contact with the main body 2 are formed with sawtooth portions 11. An air layer is formed between the sawtooth portion 11 and the main body 2, whereby, as shown on an enlarged scale in FIG 13, the light rays which are emitted out of the main body 2 into the air layer include increased components in parallel with the optical axis. Therefore, in order to fully utilise such components, the sawtooth surfaces of the auxiliary element 9 receive the light rays emitted from the main body 2 substantially at right angles therewith or in the directions almost parallel with the optical axis. When the light rays are emitted out of the auxiliary element 9M, its components parallel with the optical axis are increased. In an embodiment of the invention shown in FIG 14, an auxiliary element 9N consists of a lamination of a plurality of relatively thin layers. Each layer of the auxiliary element is gradually increased in thickness in the direction away from the incidence surface 3 whereby, as shown in FIG 15, components of the light rays which are in parallel with the optical axis are gradually increased as the light is transmitted through the layer by reflections and emitted out of the layer to the surrounding medium. FIG 16 is a diagrammatic view illustrating on a further enlarged scale a portion of the non-inventive assembly in which a plurality of main bodies 2 are arranged in a parallel array as shown in FIGS 4 and 5. As described above, when a light ray enters through the surface 3 of incidence into any one of the main bodies 2, it undergoes repeated total reflections within the main body 2 and then is emitted out of the main body 2 into the surrounding medium. As described above, the incident light ray L is converted into a light ray which is emitted out of the main body and has an increased components parallel to the longitudinal direction of the main body relative to the incident light ray L. When the light rays emitted out of the one main body 2 enters the adjacent main body 2 successively, the components parallel to the longitudinal direction of the main body 2 are gradually decreased as shown in FIG 16 as it passes through one main body to another. It is therefore quite apparent that such phenomenon is not desirable. In order to prevent such undesired phenomenon, the assembly according to another embodiment of the invnetion as shown in FIG 17 can be used. According to this assembly, a plurality of main bodies 2d which are arranged in a parallel array and directed in one direction are inserted into the spaces defined between the adjacent main bodies 2c which are arranged in a parallel array and directed in the other or opposite direction in complementary relationship. In this assembly, a light ray L which is incidence on the surface 3 of the incidence of one main body 2c and enters the same, undergoes repeated total reflections within the main body 2c, is emitted out from the main body 2c and immediately enters an adjacent main body 2d which is oriented in the one direction. After undergoing repeated total reflections within the main body 2d, the light is emitted out of the main body 3d into the surrounding medium through the bottom surface of the main body 2d. Thus, the phenomenon described before with reference to FIG 16 can be avoided. In the case of the assembly of the main bodies 2c and 2d as shown in FIG 17, a suitable light control element can be attached to at least one surface of the assembly. In the case of an embodiment illustrating such attachment of optical control elements, as shown in FIG 18, a lenticular lens 20 is attached to the surfaces 3 of incidence of main bodies 2c. Further, a Fresnel lens 21 is attached to the bottom surfaces of the main bodies 2d. It is possible to exchange the positions of such lenticular lens and Fresnel lens or to eliminate a lenticular lens or Fresnel lens. Furthermore, it is possible to superimpose a plurality of such light control elements one upon another. Moreover, other light control elements can be used. When such light control elements are provided, further controls of light rays in response to optical characteristics of these light control elements can be made. As described above, when the device for changing the directions of the light rays in accordance with the present invention is utilised, light rays from different directions and within a certain angular range, incident on a stationary surface of incidence, can be caught and can subject them to repeated internal reflections therewithin, to convert the light rays into light rays which are substantially in parallel with a desired direction. Furthermore, even when the direction of incident light varies, it is not needed to trail the incident light. Moreover, the three-dimensional main body used in this invention can be fabricated from a simple optically transparent material. Therefore, the device, in accordance with the present invention is inexpensive and is free from breakdowns. In addition, in the device in accordance with the present invention, a plurality of main bodies can be assembled into various shapes to obtain further useful effects. When the devices in accordance with the present invention are superimposed one upon another or bundled, further complex and useful effects can be obtained. Industrial Applicability : According to the present invention, it becomes possible to receive scattered light, diffused light, light emitted from various portions of a light source having some size, light whose direction varies and so on to redirect it in a predetermined direction or project it with a desired shape. Therefore, the present invention can be used for utilisation of the solar energy, illumination control, transmission of images and patterns and so on.

Claims: An assembly for changing the directions of light rays, comprising a plurality of main bodies (2, 2c) made of an optically transparent material and arranged side by side, each of the main bodies being of a wedge-shaped cross section gradually decreasing in transverse dimension from an end face (3) at one end to another opposite end (4) of the main body, said main body having said end face (3) formed as a light incident surface and also having, between the end face (3) and said opposite end (4), light reflecting surfaces (5a, 5b) for causing successive internal reflection, in the main body, of light rays (L₁, L₂) which have entered into the main body through said light incident surfaces (3), said light reflecting surfaces being so oppositely inclined that when the light rays (L₁, L₂ ) undergo the successive internal reflections by said reflecting surfaces, the directions of said successively internally reflected light rays are caused to have incident angles which at least reach a critical angle ( δ ₀) with respect to said reflecting surfaces (5a, 5b), so that portions of said reflecting surfaces at which said successively internally reflected light rays reach angles equal to or smaller than said critical angle ( δ ₀) and surface portions adjacent to said portions constitute a light emerging surface through which said light rays are emitted, the light incidence surfaces (3) of said plurality of main bodies being arranged in a parallel array and in coplanar relationship with each other: characterised by an auxiliary optical element (9, 9M, 9N, 2d) which is made of an optically transparent material disposed closely adjacent to said reflecting surface (5a or 5b) of each of said main bodies (2, 2c), said optical element having a wedge-shaped cross section for changing the directions of light rays emerging from said light emerging surface, said optical element being oriented in such a manner that the transverse cross-sectional dimension of the element is gradually decreased in a direction from said opposite side toward said light incidence surfaces (3). An assembly according to claim 1, characterised in that said auxiliary optical element (9,9M, 9N) is of a triangular cross sectional shape when taken along a plane including the path of a light ray emerging from said light emerging surface. An assembly according to claim 2, characterised in that said optical element (9M) has a surface (11) which faces said light emerging surface and which has a sawtooth-shaped sectional configuration. An assembly according to claim 2, characterised in that said optical element (9, 9M, 9N) is disposed adjacent to a part of each main body, located toward said opposite end (4) thereof. An assembly according to claim 1, characterised in that said optical element (2d) has a sectional shape complementary to and filling a space defined between adjacent main bodies. An assembly according to claim 5, characterised in that an optical control element (20) is provided on said light incident surfaces (3) of the main bodies. An assembly according to claim 5 or 6, characterised in that a Fresnel lens (21) is provided across said opposite ends (4) of the main bodies.

Inventors: NEGISHI MASATAKA, NEGISHI, MASATAKA
Applicants: NEGISHI MASATAKA, NEGISHI, MASATAKA
Application year: 1986
Main classification: G02B5
IPC codes: G02B6, G02B5