LIGHTING APPARATUS

Abstract: A light control lens (2, 2A, 2B) having a special cubic shape is fitted onto the outer surface of a cylindrical or a spherical source of light (1, 1A, 1B) so as to directly cover at least a portion thereof. The light from the source of light is emitted passing through the light control lens. The light control lens (2, 2A, 2B) has a cubic shape so as to control the flux of light from the source of light (1, 1A, 1B) to have a predetermined distribution of flux of light and a range of flux of light. Typically the light control lens has a cross-­ section, when cut by a plane containing the flux of light passing the lens, which has a pair of swollen portions (2a) that protrude toward directions to separate away from the source of light on both sides of the source of light, and a recessed portion (2c) that is recessed therebetween on the side opposite to the source of light, the swollen portions (2a) and the recessed portion (2c) being smoothly contiguous to each other. The light control lens may have a variety of other shapes in cross-section.

Description: Technical Field The present invention relates to a lighting apparatus provided with a light control lens capable of freely controlling as desired the luminous flux being emitted from a light source. Background Art Normally, a lens is inserted in a path of the light from a light source, thereby controlling the luminous flux being emitted from the light source. However, a conventional lens must be installed some distance away from the light source, and a structure for supporting the lens must also be provided. Further, a conventional lens cannot be used where the light source is of elongated shape, and the luminous flux cannot be controlled to provide a desired flux distribution and range of incidence. FR-A-647907 (see Fig. 3) discloses lighting apparatus including a lens which, in cross section, has a pair of swollen portions on two opposed sides of the light source and a recessed portion on the side of the lens remote from the light source and between the swollen portions. The lens disclosed has an opening between the swollen portions and a space is provided between the lens and the light source. With such an arrangement, it is not possible to control all of the light rays emanating forwardly from the light source because of the space between the lens and the light source and because some light rays from the light source will pass through the opening between the swollen portions without being controlled by the lens. An object of the present invention is, therefore, to provide an improved arrangement wherein a support structure is not particularly required for a lens, because the lens is supported directly on the light source, whereby a lighting apparatus can be configured compactly, and further, the luminous flux can be controlled freely as desired by the lens. This object is achieved by a lighting apparatus, according to the claims. Brief Description of the Drawings Figure 1 is a sectional view of one embodiment of the invention; Figure 2 is a view explanatory of the function of the embodiment shown in Figure 1; Figure 3 is a view showing another embodiment of the invention; Figure 4 is an explanatory view showing variations of the shape of the light control lens used in the present invention; Figure 5A is a sectional view of another embodiment of the invention; Figure 5B is a sectional view showing a modification of the embodiment of Figure 5A; Figures 6 and 7 are perspective views showing different modes of application of the embodiment shown in Figure 1; Figures 8 and 9 are views showing different modes of application of the embodiment shown in Figure 3; Figure 10 is a perspective view showing an embodiment of the invention for producing a bright line; Figure 11 is a perspective view showing an example wherein a bright line is produced by means of the embodiment of Figure 1; Figure 12 is a perspective view showing another application of the embodiment of the invention; Figure 13 is a perspective view of a further embodiment of the invention; and Figure 14 is a perspective view of a still further embodiment of the invention. Best Modes for Carrying out the Invention Figure 1 represents the basic structure of an embodiment of the lighting appartus of the invention. In this figure, reference numeral 1 denotes a light source, which is, for example, a fluorescent light emitting tube, a cold cathode discharge tube, or the like, and has a cylindrical outer surface 1a. A light control lens 2 is provided so as to directly cover a semi-cylindrical portion of the outer surface 1a. In cross-section taken along a plane including a luminous flux passing through the light control lens 2, the lens 2 has a shape consisting of swelled portions 2a and 2a on two opposed sides, a recessed portion 2c close to the light source 1 located intermediately between the two swelled portions 2a and 2a, and another recessed portion 2b at the reverse side which is fitted on and in contact with the light source 1. The light control lens 2 is formed to cover the overall length of the light source 1 with the illustrated sectional shape and forms an integral structure with the light source 1 by the fitting thereon, for example. The recessed portion 2b has the same configuration as the light source 1, and the swelled portions 2a and the recessed portion 2c have a shape bounded and defined by a smoothly continuing curve. In the lighting apparatus using the light control lens 2 of the shape shown in Figure 1, light emitted from the light source 1 is irradiated on a surface 4 to be illuminated with such a luminous flux distribution as indicated by arrows 3 through the light control lens 2, as shown in Figure 2. That is, the light flux is widened or diverged through the light control lens 2 before reaching the surface 4 which is to be illuminated. In this case, the luminous flux reaching the surface 4 to be illuminated can be made uniform in distribution throughout the whole surface or can be controlled so as to have some specific portion or portions higher or lower in luminous flux density. This can be varied as desired by varying the sectional shape of the light control lens 2. Design of the sectional shape of the light control lens can be carried out by using a computer if dimensions of the light source, light incidence range of the luminous flux and luminous flux distribution are determined. Figure 3 shows an embodiment wherein the light emitted from the light source 1 is converted into a parallel luminous flux 5 through the light control lens 2. In this case the light control lens 2 is shaped in cross-section to have a projected portion 2d at the centre, the swelled portions 2a and 2a on both sides being smaller than those shown in Figure 2 and relatively thin so that their outer surface is closer to the outer surface of the light source 1. Figure 4 shows changes in the cross-sectional shape of the light control lens 2 depending on the luminous flux required. In the case of the cross-sectional shape indicated by reference character A, where the luminous flux is to be widened or diverged fully, the swelled portions 2a and 2a on both sides are the largest and the recessed portion 2c is present on the front surface, while in the case of the shape indicated by reference character B, where the luminous flux is to be less divergent, both of the swelled portions 2a and 2a are lower and the recessed portion 2c is shallower. When the luminous flux is to be made parallel, both the swelled portions 2a are further lowered, the recessed portion 2c disappears and the projected portion 2d protrudes on the front surface, as indicated by cross-sectional shape C, and when the luminous flux is to converge, the swelled portions 2a on both sides are made lower further, as indicated by cross-sectional shape D, and the projected portion on the front is made much higher. The light control lens 2 may be made of glass. However, it can also be made of a transparent synthetic resin such as acrylic resin, polycarbonate resin or the like. Further, to allow heat from the light source 1 to dissipate, a slight clearance or grooves may be formed between the outer surface 1a of the light source and the recessed portion 2b of the light control lens 2. Still further, as shown in Figure 5A, a Fresnel surface 2e can be formed having a multiplicity of parallel ribs, triangular in cross-section, formed on the recessed portion of the light control lens 2 adjacent to the light source. In this case, further light control is made by the Fresnel surface 2e. A similar Fresnel surface 2f may be provided on the outside of the light control lens 2, as shown in Figure 5B. The Fresnel surfaces 2e and 2f may both be provided, or one of them may be dispensed with. The formation of the Fresnel surface or surfaces will make possible reduction of thickness of the thick portions 2a of the light control lens 2 as in the case of the known Fresnel lenses, thereby obtaining a control lens which is entirely substantially uniform in thickness. Figure 6 represents an example of application of the embodiment shown in Figure 2. In this example, the light control lens 2 controls light from the light source 1 and sends a luminous flux to the surface of a light transmissive, light diffusion plate 7 with a uniform light flux distribution, whereby the diffusion plate 7 is made luminous with an entirely uniform illuminance on the back surface thereof. In this case, the light control lens 2 can be so designed as to control the incidence range of light in a manner to prevent the light from arriving outside of the surface of the diffusion plate 7, thus producing little or no light loss. In contrast, in conventional surface lighting apparatus, only a passive method, such as disposing the light source farther away from the light diffusing surface, or increasing the thickness of the diffusion plate is commonly used for preventing the light diffusion plate from having light and dark areas depending upon the position of the light source, but still, such method entails a loss of light, and the thickness of the lighting apparatus inevitably increases. However, such problems can be solved by the example. In the example of application shown in Figure 7, the arrangement is such that light coming out of the back side (the side where the light control lens 2 is not provided) or the light source 1 is reflected by mirrors 8 and 8 provided on the back, is directed to the surface of the diffusion plate 7 as a luminous flux distributed uniformly, and is then superpose on the luminous flux which has passed through the light control lens 2 as in the example of Figure 6. In this example, loss of light can be further decreased by so shaping the mirrors 8 and 8, through computer design, that they produce a reflected luminous flux which is distributed uniformly. Figures 6 and 7 represent the examples where a luminous flux of uniform distribution is produced. However, the luminous flux could be made to have a non-uniform pattern as desired, as mentioned hereinabove. Figure 8 represents an example where the lighting apparatus for generating parallel luminous flux, as shown in Figure 3, is used for surface illumination having a uniform light flux distribution. Light from the light source 1 is converted into a parallel luminous flux 5 through the light control lens 2, reflected by a Fresnel reflection mirror 9 and is then directed to a light transmissive, light diffusion plate 10 as a uniformly distributed luminous flux increased in width. As a result, the upper surface of the diffusion plate 10 is made luminous with a uniform illumination distribution. According to this example, an extremely thin surface lighting apparatus can be obtained. Similar light source 1 and light control lens 2 could also be provided on the right side of Figure 8, as indicated by chain lines, so as to send parallel luminous flux to the Fresnel reflection mirror 9. In the example of Figure 9, a parallel luminous flux of uniform distribution which has passed through the light control lens 2 is irradiated slantwise onto the surface of a printed substrate 11 having electronic parts thereon. LCDs could be provided on the outside surface of the diffusion plate 10, thereby enabling observation of an image on the outside from the top. When an inspection is to be made by applying a light on the printed substrate 11 as described, the reflected light as viewed in a direction is required to be uniform in brightness, and this may easily be realised from applying the example of Figure 3. In the embodiment of the invention shown in Figure 10, the shape of the light control lens 2 is designed so that light which has passed therethrough will be converged to form a bright line 13. Such bright line 13 can be used for scanning in copying machines, facsimile machines and the like. Figure 11 represents an example wherein the light control lens 2 is similar to that in the example of Figure 2, and wherein the luminous flux which has been widened by the light control lens 2 is directed onto and reflected by mirrors 14 and 14 to produce a bright line 13. In the example of application shown in Figure 12, three lighting apparatus as that shown in Figure 2, wherein the luminous flux is widened to produce a uniform distribution, are provided for the three primary colours, respectively, and luminous fluxes of the three primary colours distributed uniformly are irradiated on a light transmissive, light diffusion plate 15. In a conventional light box of this kind, when three illumination light sources for the three primary colours are provided, the three primary colours, red, green and blue, are displayed unevenly or non-uniformly on the diffusion plate. However, in this example, the three primary colours, or two colours, arbitrarily chosen, are mixed uniformly, covering the overall surface of the diffusion plate 15, and if the light source for any one of the three colours is lighted, the overall surface of the diffusion plate 15 is made luminous uniformly with the one colour. In this example, a mirror 16 similar to the mirror 8 shown in Figure 7 may be provided. The light source need not necessarily be an elongated one, having the above-mentioned length, but may be a point source, such as a spherical one. One example is as shown in Figure 13, where a point source (spherical light source) 1A is covered with a light control lens 2A on the outer surface thereof. The light control lens 2A is so shaped three dimensionally that it will direct the luminous flux for uniform distribution on the overall surface of a square light transmissive, light diffusion plate 17. It is also possible to direct the luminous flux only in a disk-like area with a uniform distribution if the diffusion plate 17 has the shape of a disk, as indicated by the dotted line 17'. In the embodiment shown in Figure 14, a light control lens 2B is placed detachably on an almost spherical light source 1B (incandescent lamp, for example), thereby obtaining a uniformly-distributed luminous flux 18. In the embodiments described above, the outer surface of the light source is in the shape of a bulb, and the light control lens is put on the outside of the bulb. However, the outer surface wall of the light source may be, in itself, be shaped as a light control lens. According to the present invention, a lens for controlling the light emitted from the light source is provided directly on the outer surface of the light source, and therefore, a separate supporting device is not particularly required for the lens. Further, the lens is formed as a member fixed to the light source, so that space can be saved reasonably and the entire lighting apparatus can be simplified to a compact structure. Industrial Applicability In the present invention, a light control lens is so shaped, three dimensionally, as to control the luminous flux freely as desired, whereby the invention is applicable extensively to lighting apparatus, display units and other equipment.

Claims: Lighting apparatus comprising a circular cylindrical light source (1) and a light control lens (2) having a recessed portion (2b) whose surface is complementary to the outer surface (1a) of the light source (1), the lighting apparatus having a plane of symmetry, the lens (2) including swollen portions (2a) one to each side of the recess portion (2b), the lighting apparatus being characterised in that the lens (2) is of solid construction and fits directly onto the light source (1) with its recessed portion (2b) in contact with the outer surface of the light source (1), and in that the surface of the lens (2) remote from the light source defines in cross section a smoothly continuous curve which is convex as it passes around the swollen portions (2a) of the lens and is concave as it passes around a recess (2c) positioned between the swollen portions. Lighting apparatus comprising a circular cylindrical light source (1) and a light control lens (2) having a recessed portion (2b) whose surface is complementary to the outer surface (1a) of the light source (1), the lighting apparatus having a plane of symmetry, the lens (2) including swollen portions (2a) one to each side of the recess portion (2b), the lighting apparatus being characterised in that the lens (2) is of solid construction and fits directly onto the light source (1) with its recessed portion (2b) in contact with the outer surface of the light source (1), and in that the surface of the lens (2) remote from the light source defines in cross section a smoothly continuous curve which is convex as it passes around the swollen portions (2a) and around a forwardly projecting portion (2d) of the lens positioned between the swollen portions. Lighting apparatus as claimed in claim 1 or claim 2 characterised in that the surface of the recessed portion (2b) of the lens defines a Fresnel surface (2a). Lighting apparatus as claimed in claim 1 or claim 2 characterised in that the surface of the lens remote from the light source defines a Fresnel surface (2e, 2f). Lighting apparatus comprising a spherical light source (1) and a light control lens (2) having a recessed portion (2b) whose surface is complementary to the outer surface (1a) of the light source (1), the lighting apparatus having a plane of symmetry, the lens (2) including swollen portions (2a) one to each side of the recess portion (2b), the lighting apparatus being characterised in that the lens (2) is of solid construction and fits directly onto the light source (1) with its recessed portion (2b) in contact with the outer surface of the light source (1), and in that the surface of the lens (2) remote from the light source (1) defines in cross section a smoothly continuous curve which is convex as it passes around the swollen portions of the lens and is concave as it passes around a recess positioned between the swollen portions.

Inventors: NEGISHI, MASATAKA
Applicants: NEGISHI, MASATAKA
Application year: 1985
Main classification: F21V5
IPC codes: G02F1, F21V17, F21V5, H01J61, H01K1