HEADLAMP

Abstract: The invention relates to a headlamp, particularly for vehicles. The headlamp comprises a body (A), a light transmitting surface (1) and a light source (5) and at least one opaque mirror surface (3, 9) for reflecting light into the body (A). The body (A) is a solid form piece made from a transparent material like optical glass or the like preferably by moulding comprising a first surface portion which functions as the light transmitting surface (1). Light from the light source (5) is arranged to propagate inside the body (A) and to pass through said light transmitting surface (1) for obtaining a desired light distribution in the illuminated area.

Description: HEADLAMP The invention relates to a headlamp according to the ingress part of claim 1. Vehicle headlamps are placed as low as possible so that glare of meeting vehicles is minimized. Light beams from the headlamps can not however be directed too low because light that is reflected especially from a wet road surface causes glare to the eyes of the driver of the meeting car. Also fog, rain or snowfall that is illuminated by the headlamps of the vehicle may reduce visibility. In this case, light is reflected from raindrops or snowflakes to the eyes of the driver and prevents him from seeing far¬ away objects on the road. Nowadays headlamps of vehicles are structurally alike and function according to the same principle. They have a housing with a light bulb, reflector and protective glass. The bulb of the headlamp has two filaments, one of them i.e. the filament for distant lights is disposed at the focus of a parabolic mirror surface and, in a correspon- ding way, the filament for dip lights is disposed a few millimeters in front of the focus. All light beams of the distant light, which come from the focus, are reflected by the mirror surface in a direction parallel with the focal axis and, in a corresponding way, all beams of the dip light, which come from the front of the focus, are reflec¬ ted downwards towards the focal axis. The function of the protective glass is to serve as a diffusor for the thin light cone that comes from the ref¬ lector so that one obtains a desired light distribution. Therefore, the protective glass is provided with different kinds of grooves which cause the light cone to spread. The housing is either spherical or, depending on the motorcar, rectangular or has some other form. The design of present motorcars requires a broad and flat shape of the headlamp. Headlights which have a sealed structure are also used as headlamps. The sealed housing is filled with gas and and the filaments are free. These so-called Sealed-Beam lights are used especially in the United States, UK and Japan. Conventional headlamps have following drawbacks which are due to their structure and their principle of operation. The metal coating of the mirror surface on the inner surface of the housing is continuously exposed to air which leads to gradual darkening of the metal coating and reduction in the luminous efficiency of the headlamp. For instance, humidity and impurities penetrate into the housing through an opening which is used for installing the bulb. The headlamp is easily broken. For instance, one hit of a stone can break the headlamp so that it can not be used anymore. Possibilities to change direction of the light cone are limited and changing of the direction of the light b .means of the protective glass is difficult and impractical because scattering, energy losses and glare takes always place within the glass-air boundary surface. It is the objective of the present invention to obtain a headlamp in which the mirror surface remains untarnished which is impact resistant and which produces a light cone of such a shape that causes no glare and that illuminates the road sufficiently. These objectives are achieved in accordance with the invention by means of a headlamp characterized in what has been said in the characterizing part of claim 1. The most important advantages which are achieved by the headlamp of this invention are the following. Structurally a solid headlamp is impact resistant and does not break so easily as a headlamp with a housing. The headlamp needs no inner mirror surfaces. The mirror surfaces are preferably situated on the outside surface of the headlamp. Surface losses of luminosity are small due to the solid glass or plastic structure. The surface of the headlamp can be hardened to resist impacts and the battered surface can be repolished clear again. The headlamp can be manufactured by a simple moulding technique. The headlamp needs a small space and it can be placed e.g. into the bumper of the motorcar. In a headlamp according to the invention, two mirror surfaces are used which are both shaped to produce a desired light distribution or a desired distribution of reflected light. In his context, the term light distribu¬ tion is defined as the light intensity in different points of the 3-dimensional space and the term illuminated area as the area or space outside i.e. generally in front of the headlamp. Furthermore, the bulb is placed in a recess or the like which is provided with a hole reflector for directing the light from the bulb onto the mirror surface. This brings along following additional advantages. Through shaping of the mirror surfaces of the headlamp, the light cone can be very easily formed in a desired way for ins¬ tance to obtain an unsymmetric light cone for dip lights. Desired special targets, like the road side, can be illu¬ minated by the headlamp. Several bulbs can be disposed in the same headlamp and the headlamp can have areas e.g. for direction indicator and for extreme lights. Changing of the bulb is also easy. Furthermore, by using two mirror surfaces the body can be shaped flat or thin as seen from the side and broad as seen from above and then the ra- diating surface is possible to bring downwards close to the road surface. In a conventional headlamp, the light distribution on the illuminated area is obtained by patterning of the protec¬ tive glass which functions as the diffusor of the light. In the headlamp according to the invention the same is obtained by the shaping of the mirror surface. Due to the shaping of the mirror surface, the whole light transmit¬ ting surface of the headlamp does not look bright because different areas of the mirror surface are shaped to direct light in different directions and therefore there is less glare. The invention will now be described in the following referring to the enclosed drawings in which figure 1 shows a vertical cross-section of the head¬ lamp, figure 2 shows the headlamp seen from above. The headlamp of the example comprises a body A of the headlamp, which body A is made of a transparent material like optical glass or a corresponding plastic and which is suitably shaped and which is preferably manufactured by moulding. The body A is shaped so that its first surface portion forms, in the examplary case, an oblique light transmitting surface 1. On the second side of the body A, in the upper part of the device, there is a cylindrical recess 7 in which the light source 5 and, in the examplary case, a tubular metallic hole reflector- 6 for directing the light are placed. At least the wall of the recess 7 that is nearest to the mirror surface 3 is polished for preventing light losses. The bulb is installed in the recess 7 from above without any obstacles. The body A has a groove 2 shaped thereon above the light transmitting surface 1 against which groove the edge of the bonnet of the motorcar is fitted when the device is installed in the motorcar. Since the body A is totally a piece of solid material, light from the light source, when proceeding through the body, must pass through only one air-glass boundary surfa¬ ce and only one glass-air boundary surface. In the exam¬ plary case, light from the light source 5 propagating through the body meets the first boundary surface at the back of the body A in front of the light source and the and the second boundary surface at the level of said light transmitting surface 1. Between these boundary surfaces light is reflected by two mirror surfaces i.e. the first mirror surface 3 and the second mirror surface 9. Accor- ding to figures 1 and 2 the mirror surfaces 3, 9 are formed on or fixed to the second surface portion of the body A bordering the light transmitting surface 1. In the example, the first mirror surface 3 is formed on the upper side of the body A above the light transmitting surface 1 and the groove 2 and the second mirror surface 9 is formed on the lower side of the body A. It is advantageous to protect the outside of the exposed light transmitting surface 1 of the headlamp by some transparent material, e.g. hard plastic, to protect it from hitting stones. Other parts of the body can be e.g. painted using some hard paint or coated with some other suitable material like for instance plastic. Mirror surfaces 3, 9 which are opaque, can be made by evaporating on specific parts of the moulded body. They can be e.g. thin layers of aluminium or silver which are covered with a layer of hard plastic to prevent the mirror surface from breaking. Mirror surfaces 3, 9 can also be formed of strips or pieces in which case the depth of the headlamp can be very small. The light source 5, which is placed in the hole 7, comp¬ rises a bulb installed in a protected lampholder. The bulb is installed, in the example, inside a tubular hole ref¬ lector 6. The hole reflector 6 has a light opening 8 which directs the light from the light source 5 in a desired direction and therefore defines the true size of the light source. The inner surface of the hole reflector 6 is polished or foliated to prevent light losses within the hole reflector 6. Mirror surfaces 3 and 9 are shaped so that light which comes through the light opening 8 is reflected by the first mirror surface 3 to the second mirror surface 9 from which light is directed to the illuminated target through the light transmitting surface 1. Mirror surfaces 3, 9 are shaped so that essentially all light from the light source 5 to the first mirror surface 3 is reflected to the second mirror surface 9 from which essentially all light is reflected to the illuminated area. Shaping of the mirror surface is known in itself and is based on the utilization of the physical laws known from optics concerning reflec¬ tion and refraction of light. Therefore, it is possible to calculate numerically such a suitable shape for the mirror surface that produces a desired light distribution when the light distribution that comes to the mirror surfaces is known. Figures 1 and 2 show one example of the direc¬ tions of the light beams which propagate via the first and the second mirror surface. The light opening 8 of the hole reflector 6 and the first and the second mirror surface 3, 9 are placed and shaped so that the headlamp produces a desired light distribution on the illuminated area i.e. giving desired direction and shape of the light cone and the spacial intensity of light. Therefore, by shaping the mirror surfaces 3, 9 in a suitable way the light cone can be directed in a desired way and the light intensity can be arranged so that light intensity has a suitable magni¬ tude at any specific point. The bulb of the headlamp contains two separate filaments, one for dip lights and one for distant lights. When dip lights are used, light produced by the filament is direc¬ ted through the opening 8 of the hole reflector 6 to the first mirror surface 3 e.g. to the upper part thereof. Therefrom light is reflected e.g. to the upper part of the second mirror surface 9, which is shaped so that it ref¬ lects light downwards. Thus, glare to the eyes of the oncomers is reduced or totally prevented. In a corres¬ ponding way, when distant lights are used, light from the filament for distant lights is conveyed via mirror surfa- ces 3 and 9 so that the light leaving the headlamp is directed farther away. In the examplary case, a parabolic reflector of the bulb is not needed at all because the hole reflector takes care of the directing of light in an appropriate way. If a bulb that produces directed light is used as the light source there is no need to use a hole reflector 6. The device can be provided with several light sources 5 which function e.g. as direction indicators or other attentional lights. The invention is not limited to the above embodiment but it can be varied within the limits of the enclosed claims. Light from the light source can be reflected e.g. by one or e.g. by three mirror surfaces and the mirror surfaces can also be disposed inside the body. It is also possible to install several light sources in the headlamp which have their own mirror surfaces. The headlamp according to the invention can also be used in other applications than in motorcars. In this case, the applications in question are for instance control and location systems used in industrial plants, aircraft lights and so on.

Claims: Claims 1. Headlamp, particularly for vehicles, comprising a body (A) , a light transmitting surface (1) and a light source (5) , the area outside the headlamp forming the illuminated area, characterized in that the body (A) is a solid form piece made from a transparent material like optical glass or the like preferably by moulding comprising a first surface portion which functions as the light transmitting surface (1) , and that the headlamp additionally comprises at least one opaque mirror surface (3, 9) for reflecting light into the body (A) and that the light from the source is arranged to propagate inside the body (A) and to pass through said light transmitting surface (1) for obtaining a desired light distribution in the illuminated area. 2. Headlamp according to claim 1 characterized in that said at least one mirror surface (3, 9) is shaped to produce a desired light distribution in the illuminated area and/or a desired distribution of reflected light. 3. Headlamp according to claim 2 characterized in that it comprises two mirror surfaces (3, 9) disposed on a second surface portion of the body (A) , on the opposite sides of the body (A) , wherein the light from the source (5) is arranged to be reflected from the first mirror surface (3) to the second mirror surface (9) and then to pass through said light transmitting surface (1) , and that the first mirror surface (3) is shaped to produce a desired distri¬ bution of reflected light on the second mirror surface (9) , which is shaped to produce a desired light distribu¬ tion in the illuminated area. 4. Headlamp according to claim 3 characterized in that the mirror surface (3, 9) is made from a layer of silver or the like which reflects light. 5. Headlamp according to claim 3 characterized in that the mirror surface (3, 9) is made from strips or pieces, which reflect light, e.g. from strips of aluminium foil. 6. Headlamp according to claim 4 or 5 characterized in that the layer of the mirror surface (3, 9), which ref¬ lects light, is protected by a plastic or the like impact resistant material. 7. Headlamp according to claim 1 characterized in that the bulb of the light source (5) is arranged to be placed essentially inside the body (A) , in a recess (7) formed in the body (A) . 8. Headlamp according to claim 1 characterized in that it comprises a hole reflector (6) placed in association with the light source (5) , the hole reflector having at least one opening (8) which is arranged to direct the light from the source (5) in a desired way. 9. Headlamp according to claims 3, 7 and 8 characterized in that the bulb of the light source (5) is provided with separate filaments for distant and dip lights, the opening (8) being arranged to direct light essentially to diffe¬ rent parts of the mirror surfaces (3, 9) so that a light cone is obtained that is directed essentially downwards, when dip lights are used, and a light cone that is direc¬ ted essentially horizontal, when distant lights are used. 10. Headlamp according to claims 1 or 7 characterized in that it contains several light sources (5) at least one of which is arranged to function as an attention light like e.g. direction indicator or extreme light.

Inventors: NOPONEN SEPPO, NOPONEN, SEPPO
Applicants: TRANSDUCER VALLEY INC, TRANSDUCER VALLEY, INC.
Application year: 1992
Main classification: B60Q1
IPC codes: B60Q1, F21S8, F21V5, F21V7, F21V8, F21V14, F21W101, F21Y101