Abstract:
A lighting unit with a reflecting mirror to prevent irradiation nonuniformity on an irradiated surface, produced by arranging a bulb as a light source in a funnel-shaped reflecting mirror having a reflecting surface and by arranging a plurality of fine reflecting surfaces on the reflecting surface non-radially and non-concentrically without clearance. Preferably the fine reflecting surfaces appear to be a honeycomb, and are formed substantially the same size of 0.01-5 mm long, 0.01-5 mm wide.

Description:
FIELD OF THE INVENTION 
     This invention relates to a lighting unit with a reflecting mirror used for lighting up goods at stores or the like, i.e., a lighting unit having a bulb with a reflecting mirror. 
     BACKGROUND OF THE INVENTION 
     A conventional lighting unit with a dichroic reflecting mirror is disclosed in U.S. Pat. No. 5,272,408. The lighting unit is produced by combining a funnel-shaped reflecting mirror which has a reflecting mirror surface provided with a dichroic film, as a light interference film and a bulb, such as a tungsten halogen lamp. Such lighting units with dichroic reflecting mirrors are used for lighting goods at stores or the like. As shown in FIG. 4, such a lighting unit with a reflecting mirror includes a funnel-shaped reflecting mirror  23  having a reflecting part  25  and a neck portion  26 , and, as a light source, a bulb, such as a straight tungsten halogen lamp  21 , provided inside the reflecting mirror  23 . A tungsten filament  30  is provided within the tungsten halogen lamp  23 . The reflecting part  25  has a reflecting surface provided with a dichroic film  24 , while the neck portion  26  is connected with the reflecting part  23 . The tungsten halogen lamp  21  is inserted and sealed into a base  28  at the upper position. 
     The tungsten halogen lamp  21  is substantially coaxially located inside the reflecting mirror  23 . The neck portion  26  of the reflecting mirror  23  and the sealing portion  22  of the tungsten halogen lamp  21  are inserted into the base  28  and combined into one component by injecting an inorganic adhesive  29  into the base  28 . 
     In the conventional lighting unit with a reflecting mirror, it is desired that as much of the light and dark image of the coiled tungsten filament  30  contained in the tungsten halogen lamp  21  as possible is prevented from being seen on the irradiated surface during lighting, so that the illuminance of the irradiated surface will be uniform and any irradiation nonuniformity on the irradiated surface can be avoided. For this purpose, fine reflecting surfaces  25   a  (FIG. 5) are formed on the reflecting surface of the reflecting part  25  in order to scatter the reflected light appropriately. More specifically, hexagonal fine reflecting surfaces  25   a  are radially arrayed in good order without leaving clearance, and the fine reflecting surfaces become smaller gradually from the opening part  27  of the reflecting mirror  23  toward the neck portion  26 . 
     In the conventional tungsten halogen lamp with a reflecting mirror, hexagonal fine reflecting surfaces  25   a  are formed without clearance. As a result, concave or convex boundary lines  25   b  are formed at the borders of adjacent fine reflecting surfaces  25   a  in radial lines from the opening part  27  of the reflecting mirror  23  to the neck portion  26 . Light that falls on the boundary will not be scattered, and thus, irradiation nonuniformity, such as radial lines, occurs on the irradiated surface. 
     As shown in FIG. 6, the luminous intensity distribution of the conventional tungsten halogen lamp with a reflecting mirror has irregularities in the curve before the light intensity comes to the peak. The irregularities indicate the radial linear difference between the bright parts and dark parts, which causes nonuniformity in irradiation. 
     SUMMARY OF THE INVENTION 
     In order to solve the problems of the conventional units, this invention aims to provide a lighting unit with a reflecting mirror that can prevent irradiation nonuniformity on the irradiated surface. 
     To achieve the aims, a lighting unit with a reflecting mirror of this invention includes a bulb as a light source, arranged inside a funnel-shaped reflecting mirror having a reflecting surface, and a plurality of fine reflecting planes that are arranged on the reflecting surface non-centrally originating and non-radially without clearance. 
     It is preferable in the lighting unit with a reflecting mirror that the shapes of the fine reflecting surfaces are at least one shape selected from the group consisting of a circle, an ellipse, and a polygon. 
     It is preferable in the lighting unit with a reflecting mirror that the fine reflecting surfaces are concave or convex. 
     It is also preferable in the lighting unit with a reflecting mirror that the surface of each fine reflecting surface is dented or protruded in the range of 0.01 to 1.0 mm. 
     It is also preferable in the lighting unit with a reflecting mirror that a dichroic film is provided on at least one wall surface of the reflecting mirror. Here, a dichroic film refers to a light interference film formed by alternately laminating a high-refractive layer including zinc sulphide (ZnS) and a low-refractive layer including magnesium fluoride. The film radiates a visible light emitted from the light source on the front surface of the mirror, and selectively lets an infrared ray go to the back of the mirror. 
     It is also preferable in the lighting unit with a reflecting mirror that the size of the fine reflecting surfaces on the entire reflecting surface is not varied substantially. The term ‘not varied substantially’ means that slight differences due to manufacturing processes is permissible. 
     It is also preferable in the lighting unit with a reflecting mirror that the luminous intensity curve is smooth when the beam angle just beneath the light source is 0° and the beam angle at the neck portion of the same light source is 90°. When the curve of the luminous intensity distribution is smooth before it comes to a peak and has no irregularities, the brightness is not varied in radial lines and there is no irradiation nonuniformity. 
     It is also preferable in the lighting unit with a reflecting mirror that the appearance of the fine reflecting surfaces is a honeycomb, so that the fine reflecting surfaces can be formed without clearance. 
     It is also preferable in the lighting unit with a reflecting mirror that the size of the fine reflecting surfaces ranges from 0.01 to 5 mm long, and from 0.01 to 5 mm wide. 
     It is also preferable in the lighting unit with a reflecting mirror that the bulb as a light source is at least one selected from the group consisting of a tungsten halogen lamp and a discharge lamp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially broken front view showing a bulb with a reflecting mirror in one embodiment of this invention. 
     FIG. 2 is an explanatory view of a reflecting part of the reflecting mirror. 
     FIG. 3 is a graph showing a luminous intensity distribution according to this invention. 
     FIG. 4 is a partially broken front view showing a conventional bulb with a reflecting mirror. 
     FIG. 5 is an explanatory view of a reflecting part of the reflecting mirror shown in FIG.  4 . 
     FIG. 6 is a graph showing a luminous intensity distribution according to the conventional technique. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a lighting unit with a reflecting mirror in accordance with one embodiment of this invention. The lighting unit includes a funnel-shaped reflecting mirror  1  made from borosilicate glass, a tungsten halogen lamp  12  containing a predetermined volume of halogenated compound and an inert gas, and a base  13  including zircon cordierite. The reflecting mirror  1  is provided with an opening part  5  including a reflecting part  3  and a neck portion  4  connected to the reflecting part  3 . The reflecting part  3  has a reflecting surface on which a light interference film, e.g., dichroic film  2 , is coated. In the tungsten halogen lamp  12 , a closed part  6 , a spheroid swelling part  7 , a narrowed-down portion  8 , a cylindrical part  9 , a sealing portion  10  are provided sequentially. A coiled tungsten filament  11  is provided inside the swelling part  7 . 
     The sealing portion  10  of the tungsten halogen lamp  12  is inserted substantially coaxially in the neck portion  4  of the reflecting mirror  1 . Furthermore, the sealing portion  10  of the tungsten halogen lamp  12  and the neck portion  4  of the reflecting mirror  1  are inserted in the base  13  and combined with the base  13  by a heat-resistant inorganic adhesive  18 , such as an inorganic adhesive including silica and alumina as main components. 
     At the sealing portion  10  of the tungsten halogen lamp  12 , a connector including metal foils ( 15   a ,  15   b ), inner lead wires ( 14   a ,  14   b ) and outer lead wires ( 16   a ,  16   b ) is sealed. Each inner lead wire is connected to one end of each metal foil, and each outer lead wire is connected to the other end of the same metal foil. 
     The ends of the inner lead wires ( 14   a ,  14   b ) that are not connected to the metal foils ( 16   a ,  15   b ) are introduced respectively into the tungsten halogen lamp  12  in order to hold both ends of the tungsten filament  11 . The ends of the outer lead wire ( 16   a ,  16   b ) that are not connected to the metal foils ( 15   a ,  15   b ) are introduced respectively from the sealed portion  10  to the outside of the tungsten halogen lamp  12 . The outer lead wires ( 16   a ,  16   b ) are connected to power supply parts ( 17   a ,  17   b ) of the base  13  respectively. The power supply part  17   a  and the outer lead wire  16   b  are connected by a lead wire  20 . A front glass  19  is provided to the opening part  5  of the reflecting mirror  1 . 
     As shown in FIG. 2, the reflecting mirror  1  is formed by arranging a plurality of overlapping fine reflecting planes  3   a  non-centrally originating and non-radially without clearance on the reflecting surface of the reflecting part  3 . The honeycombed fine reflecting planes are convex with a height of 0.3 mm (length of one side: 1.5 mm, length: 3 mm, and width: 2.6 mm) and the size does not vary substantially. 
     The fine reflecting surfaces  3   a  are formed by preparing a mold of the fine reflecting surfaces suitable for use with molding a borosilicate glass reflecting mirror  1 , and by pouring borosilicate glass into the mold. After annealing and cooling, a high-refractive layer including zinc sulphide (ZnS) and a low-refractive layer including magnesium fluoride are laminated alternately to form a light interference film (a dichroic reflecting film). 
     In the tungsten halogen lamp with a dichroic reflecting mirror according to the embodiment of this invention (hereinafter, referred to as “invented item”), the outer diameter of the reflecting mirror opening part is 70 mm, and the rated voltage is 110V. The electricity is 65 W, the central luminous intensity is 4500 cd, and the beam angle is  22  degrees. 
     An irradiation test was carried out for the invented item. The result showed that irradiation nonuniformity was not found on the irradiated surface and a uniform luminous intensity distribution was obtained. The reason for this result is that light radiated from the tungsten halogen lamp  12  was properly scattered since a plurality of convex fine reflecting plane  3   a  were formed and arranged non-centrally-originating and non-radially without clearance. 
     FIG. 3 shows the luminous intensity curve of the invented item, while FIG. 6 shows the luminous intensity distribution of the conventional tungsten halogen lamp with a reflecting mirror (hereinafter, referred to as “conventional item”). 
     As clearly shown in FIG. 3, the luminous intensity curve of the luminous distribution from the opening part  5  to the neck portion  4  of the reflecting mirror  1  of the invented lamp is smooth when the beam angle just beneath the light source is 0° and the beam angle at the neck portion of the light source is 90°. The smooth curve indicates that a beautiful luminous distribution free from irradiation nonuniformity can be obtained. 
     The shape of a fine reflecting surface  3   a  can be a circle, an ellipse, or a polygon, and it can be shaped to be concave or convex. 
     Although a tungsten halogen lamp was used as the light source in this embodiment, similar effects can be obtained by using a discharge lamp. 
     The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limitative, the scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.