EP0723671A1

EP0723671A1 - Light generator with reflective enclosure for lighting or illuminating unit having a light guide

Info

Publication number: EP0723671A1
Application number: EP95912945A
Authority: EP
Inventors: Tibor Virag; Jean-Luc Perceveaux
Original assignee: VIRAG SA
Current assignee: VIRAG S.A.
Priority date: 1993-10-12
Filing date: 1994-10-11
Publication date: 1996-07-31
Also published as: AU7941594A; AU7941694A; CA2173224A1; ZA947974B; FR2711218A1; FR2711218B1; ZA947975B; HU9600927D0; WO1995010732A1; WO1995010792A1; JPH09504136A; TW317409U; HUT73895A

Abstract

The generator comprises an enclosure (110) housing a light source and incorporating an ellipsoid portion (111) with a reflective surface, the light source being placed at the focal point located in this portion. Advantageously this portion is a semi-ellipsoid portion and the enclosure (110) also has an annular, semi-spherical portion (112) with a reflective surface sitting over the semi-ellipsoid portion, centered on said focal point (F'1), aligned with the major axis (116) of the ellipsoid defined by this portion of the semi-ellipsoid, and having an opening (114) at its top similarly aligned with said major axis (116). A tubular cylindrical section (113) with a reflective surface can also sit at one of its ends on the opening (114). Means are provided for making the generator waterproof. In another aspect of the invention, the enclosure constitutes the walls of a sealed lamp, the opening at the top of the lamp being hermetically closed by a transparent cover.

Description

Light generator with reflective enclosure for raw lighting system of ilIτrmination - using a light guide

The present invention relates to the generation of a light beam with small angular aperture, its transmission and / or its distribution in lighting or illumination systems. It applies in particular, but not exclusively, to lighting over traffic or intervention zones, most often outside, by luminaires, but not exclusively, by luminaires with specific supports such as candelabras for public roads or industrial zones; they can also be luminaires integrated into supports having a different function, such as in traffic tunnels or facade luminaires ...

It aims in particular: - the renewal of already existing equipment,

- the installation of new equipment, for example in the case of new surfaces to be lit,

- artistic lighting, for example in an aquatic environment, - lighting of public roads, industrial sites,

- but also lighting in dangerous environments such as in an explosives storage area.

According to one of its applications, the present invention relates to equipment for lighting from above an intervention circulation area, the light source is located near this area (at most at breast height) and whose head located at a distance in height relative to this same area is optically connected to the light source. Such equipment is known in particular from French patent application FR-91.08594 in an application to a street lighting candelabra. It will be recalled briefly that the head of the device described in this document includes a diffusion objective acting as a diffuser, connected to the candelabrum barrel by means of an orientation elbow.

An optical fiber whose role is to transmit the light power from the light source to the diffuser is sheathed and encased in a metal support providing the rigidity necessary for the optical fiber which is flexible, given its small diameter.

As for the light generator, this, placed in the base of the candelabrum, comprises a light source constituted by a discharge type lamp (of Xenon type or similar) placed at the focus of a parabolic reflector provided at its rear a cooling system.

The latter, in one of the variants proposed, consists of cooling fins extending down the generator.

Finally, an objective is maintained by a mount in the base of the candelabrum, above and coaxially with the reflector, and an adapter positions the end of the optical fiber in the axis of the parabolic reflector so as to collect the concentrated light beam by the objective. As can be seen here, it was necessary to use a parabolic reflector because the electric lamps currently available on the market are generally omnidirectional, or at least aim to be so, that is to say that they emit light in almost all directions. They cannot therefore be used alone when it is sought to generate a light beam of small angular aperture, that is to say a light beam which can converge on a limited surface, in this case the entry surface in the light guide (here the optical fiber), each ray of the beam forming with a preferred direction an angle less than a given angle, corresponding to the digital half-opening of the light guide when it comes to injecting light into it.

Even if such equipment is generally satisfactory, it nevertheless poses a certain number of problems, both at the level of the light generator and at the level of the fiber optic connection between the light generator and the diffuser.

As regards the generator, it can first of all be noted that the device of the prior art is designed to laterally dissipate the heat generated by the reflector. Indeed, on the one hand, the foot made of a material which is a good thermal conductor is in direct contact with the cooling fins. On the other hand, according to an alternative embodiment, the foot of the candelabrum is brought into direct contact with the parabolic reflector and the fins are arranged externally, extending vertically over the entire height of the foot around the reflector, with transverse holes. air circulation.

The risk of burns by simple contact with the foot of the candelabrum is therefore not negligible, in particular when the candelabrum is intended for lighting a public road and knowing that the internal temperature of a reflector easily exceeds 200 ° C., which suggests the temperature on the outer surface of the foot.

This problem cannot, for practical reasons, be resolved by the use of a device generating forced ventilation, since the latter is inevitably a source of additional costs in terms of energy consumption and maintenance.

In addition, it is possible that, through the air circulation holes, water can infiltrate the reflector from above, causing deterioration. ration of its internal surface and even the explosion of the lamp whose temperature is around 300 ° C.

In addition, the use of objectives to concen¬ trate the light flux on the entry surface of the light guide leads to optical losses and obliges to produce a relatively complex candelabra base in which, for example, the replacement of the lamp is awkward.

The lamp, for its part, has the disadvantage that, being a Xenon type discharge, it requires an expensive and bulky low voltage power supply.

In addition, these discharge type lamps generally comprise two glass bulbs:

- an interior bulb containing for example a rare gas to produce the arc which gives rise to light radiation;

- an outer bulb generally containing an inert gas (nitrogen, etc.) which, on the one hand, has the role of thermally, mechanically and possibly chemically protecting the inner bulb and which, on the other hand, filters UV rays.

This second bulb reduces the light output of the lamp, the light being forced to pass through two gas-quartz diopters.

In addition, the base of the lamp corresponds in all cases of known generators to an area where light cannot be reflected, an area which is found in the form of dark spots in the beam emerging from the generator.

Now being the optical connection between the light source and the diffuser, it was made by means of an optical fiber with a homogeneous core, and in particular with a liquid core. However, this type of fiber is relatively expensive to produce. In addition, they are not very rigid. Finally, with regard to the projection or distribution of the light on the surface to be lit, we have seen that in practice an elbow bent downwards is required, which requires the provision of several elbows (hence a great complexity and one very sensitive extra cost) when trying to light all around a candelabrum.

In trying to overcome this drawback, the inventor has, as explained below, been confronted with a certain number of underlying problems, in particular as regards the shape and characteristics of the diffuser.

The present invention therefore proposes in particular to overcome these drawbacks.

According to a first aspect which is interesting in itself, the present invention provides a generator of a light beam comprising a reflector inside which is placed a lamp connected to a power supply module, a network of thermally conductive cooling fins arranged around of the reflector, characterized in that these fins extend radially from this reflector to a heat shield comprising an internal wall in contact with the fins and made of a thermally conductive material, an external wall and an intermediate layer disposed between the internal walls and external, made of a thermally insulating material, the fins delimiting spaces in communication with an air passage along the light beam.

It will be appreciated that the use of a heat shield stops the radial diffusion of heat, thus avoiding heating a candelabra foot when the generator is placed vertically in the latter.

According to preferred arrangements which may be combined:

- the light beam enters a light guide, located in the air passage;

- the air passage is at least approximately vertical;

- the reflector is at least approximately vertical; the internal wall and the fins are for example made of aluminum, the external wall is made of light alloy, for example aluminum or stainless steel, while the intermediate layer is based on refractory fibers, for example made of Kevlar fabrics.

According to a second original aspect in itself, the invention proposes a light generator comprising an enclosure with a reflecting internal surface inside which a light source is placed, characterized in that the enclosure comprises at least:

a concave portion of ellipsoid with a reflecting surface, the light source being placed at the focal point of the ellipsoid situated in this portion of ellipsoid.

It is thus possible to dispense with a light concentration objective, this being reflected towards the other second focal point of the ellipsoid defined by the concave portion of ellipsoid, where one can advantageously place the entrance of a light guide.

Advantageously, the concave portion of ellipsoid is a half-ellipsoid or a concave portion of half-ellipsoid. Preferably, the portion of ellipsoid is a concave portion of semi-ellipsoid and the enclosure further comprises: an annular portion of hemisphere with reflecting surface covering from its base the portion of semi-ellipsoid, centered at said focal point, axis coincident with the major axis of the ellipsoid defined by this portion of semi-ellipsoid, and having an opening at its top of axis also coincident with said major axis.

It will be appreciated that the addition, in this way, of a second annular portion of hemisphere with reflecting surface makes it possible to bring the major part of the rays emanating from the light source to join the useful beam, that is to say say the light beam converging towards the second focal point of the ellipsoid defined by the concave portion of half-ellipsoid with the desired small angular opening. As a result, the efficiency, that is to say the ratio of the light intensity available at the second focus under a small angular aperture, to the light intensity generated by the light source, is advantageously increased compared to a generator comprising only a semi-ellipsoidal reflector.

Indeed, only a part of the semi-ellipsoidal reflector gives by reflection rays entering the useful beam as defined above. These rays correspond to only part of the rays emanating from the light source. All the other rays, except those arriving directly at said second focal point of the ellipsoid without prior reflection with the desired angle, are lost since either they do not converge towards this other focal point, or the angle which they form with the large axis of the ellipsoid with which the axis of a light guide is aligned, is too large, that is to say greater than the upper half-opening of the guide.

Thus, depending on the application envisaged, it will be possible to be satisfied with a generator comprising a simple semi-ellipsoidal reflector or else use a generator further comprising an annular portion of the hemisphere, as defined above.

The efficiency of this latter generator can be further improved by adding, very advantageously, to the enclosure, a tubular section of cylinder with a reflective surface, covering from a first of its ends the opening of the portion annular hemisphere and having an axis coincident with said major axis. According to preferred arrangements which may be combined, some of which are intended to improve said efficiency of the generator and others to ensure that the latter is watertight:

said tubular cylinder section has a circular section, said portion of semi-ellipsoid is dimensioned so that the light rays which it reflects converge towards the second focal point of said ellipsoid and form with said major axis an angle less than a given angle,

- a light guide extending along the major axis of the ellipsoid defined by the portion of ellipsoid is placed using positioning means, near the second focal point of said ellipsoid, - the angle given is equal to the digital half-opening of the guide, said annular portion of the hemisphere is dimensioned so as not to impede the propagation of the light rays reflected by said portion of semi-ellipsoid,

said enclosure is closed at the level of said opening of the annular hemisphere portion, if necessary at the level of the second end of the tubular cylinder section, by a porthole of a transparent material, constituting, where appropriate, said positioning means,

- the porthole is glued in a Teflon ring having an annular rim allowing the fixing of said porthole on said tubular section of cylinder, said rim is glued on said tubular section of cylinder, said rim is screwed on said tubular section of cylinder, a seal sealing being arranged between the flange and the section,

said annular hemisphere portion, if applicable capped by said tubular cylinder section, is movably mounted on said half-ellipsoid portion and in leaktight manner by means of a seal,

said window is a block of silica, said window consists of a lens bonded in said ring, the porthole is constituted by one end of an optical bar glued in said ring and constituting a light guide,

the porthole is constituted by a tip of a bundle of fibers bonded in said ring,

- said ring is made of Teflon,

- said window consists of a block of polished silica on its two faces for entering and leaving the light beam generated by the lamp, the exit face being intended to receive the entry surface of an optical bar constituting a light guide,

- the entry and exit faces are anti-reflective,

the silica block is capable of allowing only radiation having one or more selected wavelengths to pass,

- the light source is a lamp connected to means for supplying the lamp with electrical power and sealingly attached to the reflecting enclosure, - the light source is a lamp of the short-arc discharge type of the metal iodide type, l the arc of the lamp being placed at the focal point located in the ellipsoid portion of,

the electrical supply means comprise a socket connected to a ballast, the assembly being tightly fixed to the enclosure,

- The bottom of said portion of ellipsoid is pierced with a hole for the passage of a lamp constituting said light source, said lamp being mounted on a socket connected to a sealed power cable taken in a cable gland mounted on a watertight housing incorporating said socket and mounted at the level of the lamp through hole on said enclosure, in a leaktight manner by means of a seal, - a non-reflective hood extends from the concave portion of ellipsoid to at the entrance of the means of positioning,

- the hood is a truncated cone,

- the portion of ellipsoid is mounted movable relative to the hood, - the concave portion of ellipsoid and the hood are connected by a sealed joint surface,

the positioning means consist of a tightening and sealing ring,

- said enclosure is made of aluminum or bronze and is formed by machining or embossing,

- said enclosure is obtained by molding ceramic covered internally with a metallic coating,

- the said. reflective surfaces are made up of polished surfaces,

- the polished surfaces are covered with a surface coating in gold, rhodium, nickel, silver or aluminum.

According to a third aspect which is interesting in itself, the present invention also provides a light generator or lamp comprising an enclosure inside which a light source is placed, characterized in that the enclosure forms the walls of a sealed bulb and comprises at least: - a portion of concave ellipsoid with a reflecting surface, the light source being placed at the focal point of the ellipsoid situated in this portion of ellipsoid and the opening at the top of the bulb being hermetically sealed by a porthole in a transparent material. Thanks to these provisions, the light generator is perfectly waterproof.

But above all, the enclosure constituting the walls of a sealed bulb, it is possible to have at the focus of the portion of ellipsoid a light source which comprises, if necessary for the production of light, only single bulb. It is thus possible to do without the protective bulb of conventional discharge lamps, which is harmful to the propagation of light.

In this way, the size of the light source is much smaller, allowing the dimensions of the light generator to be reduced to a size comparable to that of a conventional electric lamp.

Such a light generator of reduced dimensions can of course be used to inject light directly into a light guide, but also in any application requiring directive lighting.

According to preferred arrangements which may be combined and which relate to this aspect of the invention:

the portion of ellipsoid is a half-ellipsoid or a portion of half-ellipsoid, said walls consist of glass covered with a metallic deposit,

the reflecting surfaces are dichroic, reflecting in the visible range and letting the infrared radiation pass, the portion of ellipsoid comprises a reflecting bottom crossed by electrodes for supplying power to said light source, embedded in the glass,

said light source comprises a substantially spherical sealed bulb enveloping one end of said electrodes and containing means capable of producing a light arc by producing an electric discharge at said electrodes,

- said enclosure is under vacuum or contains a gas under low pressure,

- the transparent porthole is formed by a portion of a cylinder or a silica or quartz pellet, a lens or an objective,

- The cylinder portion or the pellet has a planar surface for receiving the entry surface of a light guide. According to a fourth aspect which is original in itself, the present invention provides a light guide intended to optically connect a hot light source and a zone forming a cold source, characterized in that the light guide consists of a rigid homogeneous translucent bar, a holding structure extending along this bar while leaving an air layer along almost the entire lateral surface of this bar.

Here, as the case may be, the cold zone is most often close to the free end of the light guide, or even be constituted by a lateral portion of this guide. It follows from these provisions, a light guide inexpensive to produce because it does not require material sheathing. Furthermore, it is rigid and may have a larger diameter than the optical fibers hitherto used, making it possible to transmit light fluxes of very high intensity, of the order of 5,000 to 100,000 lumens.

According to preferred arrangements: - the bar is a silica bar;

- The bar is a polymethylmethacrylate (PMMA) bar;

- the bar is a bar made of pure glass;

- The bar is equipped with a mechanical protection extending at a distance from and around the bar over almost its entire length, spacers in contact with the protection and the bar centering and tightening the latter;

- the spacers are made of Teflon; - The light guide is intended to be integrated into a candelabrum barrel, the protection being able to be fixed to the candelabrum barrel using openwork brackets by one of its ends, while its other end is adapted to rest on a light generator constituting the hot source. According to yet another aspect interesting in itself of the present invention, the invention provides a light diffuser, intended to be optically connected to a light source by a light guide admitting an axis, characterized in that the diffuser present in all axial plane a V-shaped section whose apex is placed near the outlet of the guide.

In this way, it is possible to reflect towards an area to be lit at the base of the light guide in practice oriented upwards, a flux emerging from a rigid light guide such as that presented above.

According to preferred arrangements which may be combined:

- the diffuser is located at a height above the area to be lit;

- The diffuser has the shape of a cone;

- the director of the cone is a circle;

- the top of the diffuser is rounded;

- the axis of revolution of the cone is coaxial with that of the light guide;

- The diffuser has a rough, frosted or mat reflective surface, so as to homogenize the reflected light flux;

- the reflecting surface is a painted metal surface or is made of porcelain;

the angle of inclination of the reflective surface relative to the axis of revolution of the cone corresponds at least approximately to the digital half-opening of the light guide; - The diffuser is able to be integrated into a candelabra, the diffuser being fixed to the barrel of the candelabrum using rods of small section.

Of course, it is advantageous to combine the characteristics of the various aspects of the invention which have just been mentioned, in particular within a lighting equipment over a traffic zone. or intervention such as a candelabra.

Thus, in particular, the reflector in the shape of an ellipsoid portion and the non-reflecting hood may comprise a network of thermally conductive cooling fins disposed around the reflector and the hood, in contact with the latter, up to a heat shield, such as this presented with reference to the first aspect of the invention.

Any other combination within the reach of those skilled in the art between the different characteristics of the aspects mentioned above can of course be envisaged.

The objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which:

- Figure 1 is a schematic view in vertical section of a street lighting candelabra incorporating lighting elements according to the invention;

- Figure 2 is an enlarged schematic view in vertical section, in more detail, of a light generator according to a first embodiment of the invention, placed in the base of the candelabrum of Figure 1;

- Figure 3 is an enlarged schematic view from above of the generator of Figure 2; - Figure 4 is an enlarged schematic view of the upper part of the candelabra of Figure 1;

- Figure 5 is a vertical sectional view of a light generator, according to a second embodiment of the invention; - Figures 6A to 6D are schematic representations of Figure 5 and show the different possible paths for the light rays emerging from the light source; and

- Figure 7 is a schematic view in vertical section of a generator, according to a third embodiment of the invention. The lighting elements according to the invention and shown in Figures 1 to 4, are integrated into a street lighting candelabra.

The candelabra principle considered here by way of example and non-limiting application of the lighting elements of the present invention is based on the Snell-Descartes law which governs the propagation of a light wave in the heart of an optical fiber reflecting on an optical sheath with a lower refractive index. This candelabrum, marked 1 as a whole, mainly comprises three sub-assemblies: a lower part or foot 10, fixed to the ground, an elongated part or bole 20, extending from the foot upwards, and an upper part or head 30 mounted at the free end of the barrel. The base 10, as shown diagrammatically in FIG. 1, comprises at its lower part a light generator 11 fixed on a support 12, itself fixed to the base of the candelabrum in a manner not shown. This foot is in practice also equipped with an inspection hatch, not shown here. Referring now to Figure 2, there is shown the light generator 11 having a body 13 and an optic 14 movable by sliding inside this body.

The body has two fixed walls, external 13A and internal 13C, in the form of two concentric cylindrical tubular sections between which a layer of thermal insulator 13B is enclosed. This body thus forms a heat shield.

The external and internal walls are respectively made of aluminum or stainless steel and aluminum. Kevlar fabrics are suitable for thermal insulation. Other materials may be suitable provided that the internal wall is made of a material which is a good thermal conductor and the insulator made of a material which is very good thermal insulator. The body 13 receives through its lower part the sliding optic 14 held removably in this body by a bayonet fixing system (not referenced).

The optic comprises a light source 14A constituted by a short arc discharge lamp, of the metal iodide type, at least approximately placed at the first focal point FI of a semi-ellipsoidal reflector.

The top of the half-ellipsoid forming the reflector is extended by a sleeve intended to receive the base of the lamp 14A.

To accommodate this reflector, the optics also includes a network of fins 14C, preferably radial and regularly spaced, integral by the lower and upper ends of their outer edges with two rings 14E.

The inner edges of these cooling fins are shaped so as to be able to receive, with close contact, the semi-ellipsoidal reflector and its sleeve. A housing 14D enclosing the lamp socket is fixed in a sealed manner, at the base of these cooling fins, to the reflector. The diameter of the rings 14E is chosen so as to allow the mobile optics to slide within the body with contact between the rings and the fixed internal wall 13C of the body.

To complete the contact of the cooling fins with the fixed internal wall, protrusions 14F protrude from the cooling fins along their outer edges.

The housing 14 D is itself tightly connected to a ballast, not shown, connected to an electrical energy supply network (for example the E.D.F network).

In this way, the lamps can be supplied with a voltage of 220 V and an intensity of approximately 2 amps. The semi-ellipsoidal reflector 14B has at its upper part a horizontal flange 14G which, in the state assembled from the movable optics with the body, forms a sealed joint surface with a complementary horizontal flange 15A of a conical hood 15 with a truncated top.

This hood 15 is integral with the fixed internal wall 13C by means of fins 15B extending radially at regular spacing around the periphery of the hood, just like the fins 14C of the semi-ellipsoidal reflector 14 around the latter .

The truncated top of the hood is extended by a sheath 16 with jaws engaged in a clamping ring 17.

This clamping ring makes it possible to enclose a silica bar 21, the characteristics of which will be described below, with its edge 21A disposed substantially at the second focus F2 of the semi-ellipsoidal reflector. It also makes it possible to ensure complete sealing of the half-ellipsoidal reflector.

With regard to the dimensions of the constituent elements of this light generator, it will be observed that: - the reflector is chosen semi-ellipsoidal;

- The dimensions of the half-ellipsoid result from the dimensions of the lamp, from the numerical aperture inherent in the optical bar, here made of silica, received at the second focus of the reflector and from the size, in particular radial, maximum authorized for the generator;

- the hood has at its base the diameter of the semi-ellipsoidal reflector and at its top a diameter chosen so as to allow the passage of the light bar, keeping in mind that the oblique walls of this hood must never interfere with the digital aperture of the optical bar, to avoid any loss of light.

It will be noted that in practice, the position of the optical bar is adjusted relative to the second focus of the semi-ellipsoidal reflector in order to concentrate on the edge of this bar a maximum of luminous flux: if the optical bar section increases, we shift the latter slightly relative to the second focal point in the direction of the semi-ellipsoid apex corresponding to the second focal point (apex of the hood).

The spaces available between the fins 14C and 15B associated with the mobile optics and the hood, are in communication with an air passage along the light guide, here constituted by the optical bar. This results, especially when the guide is vertical, a powerful chimney effect ensuring the evacuation of the heat given off by the light source.

The post 20 of the candelabrum integrates an entirely original structure for transmitting light from a light generator, such as that described above, to a light diffuser, the characteristics of which will be detailed below.

This structure for transmitting light to the light guide consists of an optical bar 21 made of silica a few centimeters in diameter (generally between 3 and 6 cm) surrounded by an air duct 22 of which the thickness is here a few millimeters over most of its circumference, and protected by a mechanical protection 23. This mechanical protection is here in the form of a metallic cylindrical tube. Spacers 24 are arranged between the mechanical protection and the optical bar to center and tighten the latter. A material capable of following the differential expansion between the silica bar and the mechanical protection, for example Teflon, will preferably be chosen for these spacers. The mechanical protection is fixed to the barrel 26 of the candelabrum at its upper end, using perforated brackets 25 and has at its lower end a narrowed portion 27, converging inwards and downwards and resting on the ring. Tightening. Similarly, the upper end of the mechanical protec¬ tion also has a narrowed portion 32. At this end, the light bar protrudes from the mechanical protection downward, so as to be able to pass through the ring of tightening to reach the second focal point of the semi-ellipsoidal reflector. It will be noted here that the mechanical protection does not come into contact with the silica bar and that the spacers have a relatively small section, in order to provide over the major part of the circumference of the silica bar an air duct. Indeed, air is the medium allowing an optimal reflection on the wall of the silica bar. In addition, thanks to these two media of different refractive index (silica-air), the Snell-Descartes law is satisfied. Such an optical bar has the advantage of not requiring cladding, unlike optical fibers. It is also rigid, therefore requiring no metallic support in contact, such as those intended to provide rigidity to optical fibers, although preferably there is mechanical protection around this silica bar, by nature. brittle. An optical bar of course has the advantage of being able to transmit a greater luminous flux because of its larger section than that of an optical fiber. The barrel 26 of the candelabrum delimits around the optical bar a tubular space 28 constituting the air passage indicated above in connection with the chimney effect. This tubular space is here delimited directly by the mechanical protec¬ tion 23. It will be noted that the air returning through the existing natural openings, such as sheath leading the electric cables, may suffice. Of course, the constituent elements of the barrel, or even the optical bar itself, can contribute to the evacuation of the heat. It should be noted that the luminous flux emerges towards the top of the candelabra barrel through the upper edge of the silica bar. In addition, the emerging flux is inhomogeneous, because the silica bar is in practice multimode. It was therefore necessary to find a diffuser which was able, on the one hand, to reflect light towards the area to be lit and, on the other hand, to homogenize the reflected flux. According to a particularly original aspect of the present invention, this has been achieved by means of a diffuser 30 with a V section, the point (or edge) of which is directed towards the end of the optical bar, in the axis of the latter. this. This diffuser 30 is here conical in shape and its tip is rounded to reflect a greater amount of light. Its reflection surface is covered with a rough, matt or frosted material, which makes it possible to homogenize the flow. A material which satisfies the required requirements is a metallic support covered with a paint having a good coefficient of reflection in the visible or possibly porcelain. This material has a good reflection coefficient, despite the micro-irregularities created on the surface of the diffuser. It will be noted that any other form of diffuser may be suitable, provided that its section is in any plane of axial section approximately in V: prism, pyramid, etc. It is thus possible to produce illuminated surfaces of quite diverse shapes. The angle of inclination of the diffuser α is chosen as a function of the surface to be illuminated.

The diffuser is fixed by rods 31 of small section on the pole of the candelabrum, so as not to generate too large shadows on the area to be lit.

The tip of the diffuser 30 is located a few centimeters from the upper end of the silica bar.

It will be observed that in theory, the section of the diffuser at its upper end must be significantly larger than that of the silica bar, in order to avoid losses of light by dispersion upwards. In practice, this section will be a compromise between the yield in reflected light and the design sought.

By way of example, with regard to dimensions, a 5 mm arc lamp requires a distance between focal point (FI, F2) of 164 mm, a major axis of 200 mm and a minor axis of 114, 7 mm, to obtain a light spot 30 mm in diameter, when the digital half-aperture is 26 ° (silica bar). A silica bar 30 mm in diameter can therefore be used.

As a variant, with regard to the light generator, it can also be used with conventional sheathed optical fibers, such as those presented in French patent application FR-91.08594, in which case, the optical head presented in this document can also be used. This generator can also be used without a diffuser, for lighting purposes. For example, the bar can be pointed, without a diffuser, towards an area to be highlighted, or else be connected to a network of fibers, or even be frosted over all or part of its lateral surface in order, for example, to lateral illumination.

The support structure of such a bar can be a bracket.

We can also plan to cut the free end of the optical bar, for example with sawtooth indentations on its circumference, like a "fir tree" (in this case the transverse parts of these indentations can be frosted ).

The semi-ellipsoidal reflector can also be mounted adjustable relative to the lamp, in the direction defined by the two focal points, in order to optimize the amount of light reflected at the second focal point, when different sections of light guide are used.

A plastic light guide such as polymethylmethacrylate (PMMA) or pure glass can also be used instead of silica. It may be appropriate in this case to provide forced ventilation, or to provide a low power of the lamp, or even discontinuous operation. Mechanical protection, even if it is desirable because the silica bar is inherently fragile, can be replaced by a simple support, provided that the silica bar is surrounded over most of its circumference by an air duct . This support could for example be constituted by a bearing provided on the sheath or the ring described above, while retaining the tightness of the assembly.

Note also that the generator can be provided with a color change system (filters, ...) known to those skilled in the art.

We will now describe with the support of FIGS. 5 to 7 a second and a third embodiment of the invention. A second embodiment of the light generator of the invention is illustrated in FIGS. 5 and 6A to 6D.

This light generator, marked 100 as a whole, has a. enclosure 110. This enclosure or reflector 100 comprises:

- A first concave portion of semi-ellipsoid 111 with reflecting surface;

- A second annular portion of hemisphere 112 also with a reflecting surface; a tubular section of cylinder 113 with a reflecting surface covering, from a first of its ends, an opening 114 of the annular portion of hemisphere 112.

The second annular hemisphere portion 112 covers, from its base and in a removable manner, the first half-ellipsoid portion 111. It is, moreover, centered at the focal point F ′ _x (see FIGS. 6A to 6D) located in this first portion of semi-ellipsoid 111 and its axis coincides with the major axis 116 of the ellipsoid defined by this first portion of semi-ellipsoid 111.

The opening 114 at the top of the second annular portion of hemisphere 112 has an axis also coincident with the major axis 116.

As for the tubular section of cylinder 113, it has a circular section and is made in one piece with the second annular portion of hemisphere 112. Its axis is also confused with the major axis 116.

A short arc discharge lamp (about 5 mm), of the metal iodide type, is partly received inside the enclosure 110, through a hole 118 drilled in the bottom of the first portion of semi-ellipsoid 111, the arc of this lamp being placed, at least approximately, at the first focal point F 'situated in this first portion of semi-ellipsoid 111.

The lamp 117 is mounted on a socket 119 supplied by a waterproof power cable 120. The socket 119 is mounted in a waterproof case 121 comprising a through hole 122 for the power cable 120.

The tightness, at the level of the passage hole 122, is ensured by a cable gland 123 in which the cable 120 is taken, while the housing 121 is mounted by screwing, at the level of the passage hole 118, on the enclosure 110 , also in a leaktight manner, by means of a seal 124.

In this regard, the second annular portion of hemisphere 112 is also screwed tightly by means of a seal 125, by its base on an annular flange 126 extending the first portion of semi-ellip¬ soïde 111.

The screwing means of the housing 121 and of the second annular hemisphere portion 112 on the first half-ellipsoid portion 111 have not been shown in FIG. 5, and it will be noted that these screwing means can be replaced by d 'Other means, provided that the étan¬ cheite is ensured at the location of the joint surfaces where the various elements are connected.

Furthermore, the other end of the enclosure 110 is also sealed, at the second end of the tubular section of cylinder 113 by a window 127 of a transparent material. In this case, this window 127 consists of a block of silica 128 bonded in a Teflon ring 129 having an annular rim 130 allowing the fixing of the porthole 127 on the tubular section of cylinder 113.

The flange 130 is, here, screwed onto the tubular section of cylinder 113 (screwing means not shown in FIG. 5), a seal 131 being arranged between the flange 130 and the section 113.

Teflon has the double advantage of being able to withstand the high temperatures prevailing inside the enclosure 110 of the light generator 100 and possible differences in thermal expansion between the generator 100 and the silica block 128. It is understood that Teflon can be replaced by any material having the same characteristics.

It will also be noted that the light generator 100 thus produced is entirely waterproof and, in this way, neither the electrical connections of the lamp 117, nor the reflective interior surfaces of the enclosure 110 can be damaged.

The various constituent parts of the enclosure 110 are made of aluminum or bronze and are formed by machining or embossing.

The internal surfaces of the enclosure, as elsewhere the reflector 14B of the first embodiment, constituting reflecting surfaces are polished and advantageously covered with a surface coating of gold, rhodium, nickel, silver or aluminum in order to be as reflective as possible in the visible spectrum and let the infrared rays pass as much as possible.

Other coating materials may be suitable, provided that they have sufficient longevity and are capable of withstanding temperatures up to 300 ° C. inside the generator 100.

As a last precaution, the surface coating, especially when it is silver or aluminum, can be treated against corrosion. The upper 132 and lower 133 faces of the silica block, respectively of the input of the light beam coming from the lamp 117 and of the output of the generator of this light beam, are polished, the upper face 132 being intended to receive the input of an optical bar constituting a light guide (not shown in FIGS. 5 and 6A to 6D). To this end, the Teflon ring 129 and the silica block 128 are dimensioned and positioned so that the lower face 133 is, here, placed in the vicinity of the second focal point F ′ ₂ of the ellipsoid defined by the first portion of semi-ellipsoid 111.

The window 127 therefore constitutes, here, the means for positioning the light guide near the second focus

F ' ₂ - As will be described in more detail below, the light beam generated by the lamp 117 converges towards the second focal point F' ₂ , at least towards a limited surface surrounding it, where it enters the guide light at one end and is transmitted by reflection to the exit of the light guide at its other end. From there, this beam can be diffused by means of an appropriate diffuser, also not shown in FIGS. 5 and 6A to 6D.

Such light guides and diffusers have in particular been described with reference to the first embodiment of the invention and can be implemented within the framework of the present embodiment, the minor adaptations required being within the reach of ordinary skill in the art. job.

In this regard, similarly to the generator described above, the present generator may also comprise a network of thermally conductive cooling fins arranged around the enclosure 110, these fins extending radially from the enclosure to to a heat shield comprising an internal wall in contact with the fins and made of thermally conductive material, an external wall and an intermediate layer disposed between the internal and external walls, made of a material thermally insulating, the fins delimiting spaces in communication with an air passage along the light beam coming from the generator 100. These structural elements have not been shown in FIGS. 5 and 6A to 6D, and reference will be made to first embodiment for their illustration.

The internal wall and the fins will be made of aluminum, the external wall being of aluminum or stainless steel, while the intermediate layer will consist of Kevlar fabrics or an asbestos fabric.

In addition, the internal and external walls will be cylindrical tubular sections, the cooling fins arranged around the enclosure being solid with two centering rings concentric with the internal wall and coming into contact with the latter in the assembled state. of the generator, that is to say when the second annular portion of hemisphere 112 is mounted on the first portion of semi-ellipsoid 111.

As already indicated, the use of such a network of fins in combination with such a heat shield makes it possible to dissipate by a convection flow in the axis of the generator the heat produced by the latter, by stopping the radial diffusion of the heat. This avoids heating a candelabra foot in which the generator can be placed vertically, in the case of the production of a lighting assembly. Any risk of burns by simple contact with the base of the candelabra or the outer casing of the generator is thus eliminated.

We will now describe, with the support of FIGS. 6A to 6D which are schematic views of FIG. 5, the different possible trajectories of the light rays coming from the lamp 117.

As can be seen in FIG. 6A, all the rays reflected by the half-ellipsoid portion 111 with a reflecting surface converge towards the second focal point F ' ₂ at least towards a reduced surface around F' ₂ , of the ellip- soid defined by this portion and forms with the major axis 116 of this ellipsoid an angle less than or equal to an angle θ ₀ -

By dimensioning the half-ellipsoid portion 111 in such a way that the angle θ ₀ is equal to the digital half-opening of a light guide that one would come to place in the vicinity of the second focal point F ' ₂ , with its axis aligned with the major axis 116, all the rays reflected by this portion 111 enter the light guide. In other words, we thus only used the useful part of a half-ellipsoid, that is to say that which reflects only light rays forming a useful beam which converges towards the second focal point F ′ ₂ with rays. forming an angle less than the digital half-aperture. To bring some of the other rays from the focal point F \ also into this useful beam, the half-ellipsoid portion 111 is capped by an annular portion of hemisphere with reflecting surface 112, the position of which has been detailed above. As shown in Figure 6B, this other part of the rays from the focus F ' _! is thus reflected by this second annular portion of hemisphere 112 in the direction of this focal point F ′ _lf to return to the useful portion of the first portion of semi-ellipsoid 111, which it will reflect them a second time in the manner described with reference to the Figure 6A.

It will also be observed that the second annular portion of the hemisphere is dimensioned so as not to hinder the propagation of the light rays reflected by the first portion of semi-ellipsoid 111.

It is in fact located outside the light cone defined by the limiting rays reflected by the first portion of semi-ellipsoid 111 and the second focus.

Fr ' ₂ . This cone moreover has a half-angle at the vertex F ' ₂ less than the angle θ ₀ . The tubular section of cylinder 113 is itself dimensioned so as not to hinder the trajectory of all the aforementioned spokes.

As shown in FIG. 6C, yet another part of the rays emanating from the lamp 117, that is to say substantially from the first focal point F '_1; they are reflected by the tubular section of cylinder 113 with a reflecting surface.

They thus join the entry surface of the light guide by forming with the axis 116 the same angle as the emission, which for some, and even all if the second portion 112 is dimensioned accordingly, is less than or equal to the angle θ ₀ .

The other rays reaching the level of the entry surface of the light guide without reflection are shown in FIG. 6D. They also form with the axis 116 an angle less than θ ₀ .

Thus, as is understood from the view of FIGS. 6A to 6D, almost all of the rays emanating from the lamp 117 converge towards the second focal point F ' ₂ at an angle with the major axis 116 less than or equal to the angle 0 _O , either directly or after one or two reflections. Almost all of these rays will enter a light guide with an entry surface having an area close to that of face 132, the digital half-opening being equal to the angle θ ₀ , which would be placed at the level of the second focal point F ' ₂ or slightly set back towards the vertex of the ellipsoid adjacent to this last focal point, ellipsoid defined by the first portion of semi-ellipsoid 111.

Therefore, the efficiency, as defined above, of the light generator 100 thus produced is significantly improved compared to a generator comprising only a semi-ellipsoidal reflector, only a very small quantity of rays not returning in the light guide. Depending on the required output, it is thus possible to use a generator comprising a simple semi-ellipsoidal reflector, or a generator such as that which has just been described. as a second embodiment.

In other words also, almost all of the light rays emerge from the light generator thus formed under a small opening angle, of the order of 40 to 50 °.

A light generator was used for this purpose, mainly using a commercially available electric lamp and a reflective enclosure. An interesting development of the light generator described in support of FIGS. 5 and 6A to 6D, forming the subject of the present invention, will now be described, in support of FIG. 7 and constitutes the third embodiment.

This generator 100 ′ comprises an enclosure 110 ′ which comprises:

a first concave portion of semi-ellipsoid 111 ′ with a reflecting surface, and

- A second annular hemisphere portion with a reflecting surface 112 ', connected by an annular rim 126' to the first half-ellipsoid portion 111 'and having at its aperture 114' hermetically closed by a porthole made of a material transparent; the enclosure constituting the walls of a sealed ampoule.

This second hemisphere portion 112 ′ covering from its base the half-ellipsoid portion 111 ′ is centered at the focus F ′ ¹ _! of the latter and has an axis coincident with the major axis 116 'of the ellipsoid defined by this same portion of semi-ellipsoid 111'.

The opening 114 'at the top of the second hemisphere portion 112' has an axis also coincident with the major axis 116 'and is hermetically sealed by means of a transparent pellet 127' constituting a porthole, of quartz or silica.

The enclosure 110 ′, except the pellet 127 ′, is made of glass with a metallic deposit at 1 / interior so as to constitute reflective interior surfaces. An advantageously spherical bulb 140 and of reduced size, centered at the focal point F "of the first portion of semi-ellipsoid lll ', envelops the ends of two electrodes 141, 142 for producing an electric discharge and contains the means necessary for the production an arc, roughly comparable to a point at F 'and giving rise to light radiation.

The two electrodes 141, 142, embedded in the glass constituting the enclosure 110 ′, pass through the reflective bottom thereof and are received in a base 143 fixed to the enclosure 110 ′ and allowing the supply of the electrodes either alternating current, either direct current, 12 V or other. The rest of the enclosure is under vacuum or filled with an inert gas (nitrogen, etc.) under low pressure. Depending on the case, it will be possible to use means for producing an arc giving rise to a luminous ray, known to those skilled in the art, or even to replace the spherical bulb with its content and the electrodes with a simple filament. for producing a light radiation, connected at its ends to the base 143 and placed in the enclosure 110 ′ under vacuum or containing a gas under low pressure.

Thanks to these provisions, a light generator generating a light beam with a small angular opening can be made perfectly sealed but above all the dimensions of a conventional electric lamp which is placed directly opposite the light guide.

In addition, this generator 100 'does not have the drawbacks mentioned above and generated by the use of a conventional electric lamp. In this regard, it will be observed in particular that the bottom of the enclosure 110 ′ is reflective.

It will also be noted that the enclosure 110 ′ acts as external protection and that the patch 127 ′ filters the UV rays. We can, on the one hand, use this generator

100 'to inject light into a light guide placed near the second focal point F " ₂ of the ellipsoid, defined for half by the half-ellipsoid portion 111 ', by means of an appropriate mount, or even on the flat face of the patch 127' if a surface of entry of a disc-shaped guide has a diameter close to the minor axis of the half-ellipsoid portion III 'or the diameter of the pellet 127'.

Thus, depending on the section of the light guide, it is possible to use a generator such as those forming the object of the first and second embodiments or else a generator such as that forming the object of the third embodiment.

On the other hand, this generator 100 'can also be used as an electric lamp generating a narrow, directive light beam. The reflection of the light rays is here of course similar to that described with reference to FIGS. 6A to 6D.

It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention.

In other embodiments relating to this generator of reduced dimensions, the reflecting surfaces may be chosen to be dichroic reflecting in the visible range and letting the infrared radiation pass. The heat produced is thus dissipated towards the rear of the generator or lamp.

It will also be possible to cover the second annular hemisphere portion 112 ′ with a tubular section of cylinder in a similar manner to that which has been described with reference to FIG. 5.

The half-ellipsoid portion 111 ′ can be truncated at its bottom which will be replaced by a concave hemisphere with reflecting surface, centered in F ¹ ^ and of axis coincident with the axis 116 ′, if the size of the bulb 140 requires it. Depending on the application envisaged, provision may even be made to use an enclosure forming the walls of a sealed ampoule and comprising only a concave half-ellipsoid or a portion of concave half-ellipsoid, with a reflective surface, possibly provided with a hemisphere with a reflecting surface such as that just mentioned.

The patch 127 ′ can be replaced by a portion of a cylinder of transparent material, a lens or even an objective.

It will also be possible to provide this latter generator with cooling fins as has been described for the first and second embodiments.

As regards the light generator described with reference to FIG. 5, the window may consist of a lens glued in the Teflon ring.

This Teflon ring may have a rim glued directly to the tubular section of cylinder.

The enclosure can also be closed by one end of an optical bar or an end piece holding the ends of a bundle of optical fibers, glued into the Teflon ring and constituting a light guide, this ring thus advantageously constituting a frame allowing the positioning of the entry of this light guide near the second focal point of the ellipsoid as defined above.

This enclosure can also be obtained by molding ceramic, making it possible to achieve an ideal surface condition, the ceramic being covered with a metallic coating. Depending on the constitution of the generator, it is also possible to provide an additional mount, constituting positioning means, for positioning the light guide at the level of the second focal point of the ellipsoid defined by the half-ellipsoid portion. Filters can be applied to one or both sides 132, 133 of the silica block in order for example to produce a beam of colored light at the output of the generator or to return infrared radiation towards the interior of the generator.

These faces can also be treated with anti-glare.

Claims

1. Light generator comprising an enclosure (14B; 110; 110 ') with internal reflecting surface inside which a light source is placed, characterized in that the enclosure (14B; 110; 110 ') includes at least:

- a concave portion of ellipsoid (143; 111 111 ') with a reflecting surface, the light source (14 A 117; 140') being placed at the focal point of the ellipsoid (F _x ; F '- ^ F "^ located in that portion of ellipsoid.

2. Light generator according to claim 1, characterized in that the concave portion of ellipsoid is a half-ellipsoid.

3. Light generator according to claim 1, characterized in that the portion of ellipsoid is a concave portion of semi-ellipsoid.

4. Light generator according to claim 3, characterized in that the enclosure (110; 110 ') further comprises: an annular hemisphere portion (112; 112') with reflective surface covering from its base the portion of semi-ellipsoid, centered on said focal point (F '_x; F "1), of axis coincident with the major axis (116; 116') of the ellipsoid defined by this portion of semi-ellipsoid, and having an opening ( 114; 114 ') at its top of the axis also coincident with said major axis (116; 116').

5. Generator according to claim 4, caracté¬ ized in that said enclosure (110) also comprises a tubular section of cylinder (113) with reflective surface covering from a first of its ends the opening (114) of the annular hemisphere portion (112) and having an axis coincident with said major axis (116).

6. Generator according to claim 5, caracté¬ ized in that said tubular section of cylinder (113) has a circular section.

7. Generator according to any one of the claims. cations 4 to 6, characterized in that said half-ellipsoid portion (111) is dimensioned so that the light rays which it reflects converge towards the second focal point (F ' ₂ ) of said ellipsoid and form with said major axis ( 116) an angle less than a given angle (0 _O ).

8. Generator according to any one of claims 1 to 6, characterized in that a light guide extending along the major axis (116) of the ellipsoid defined by the portion of ellipsoid is placed at the using positioning means, near the second focus (F ' ₂ ) of said ellipsoid.

9. Generator according to claims 7 and 8, characterized in that the given angle (0 _O ) is equal to the digital half-opening of the guide.

10. Generator according to any one of claims 4 to 9, characterized in that said annular hemisphere portion (112; 112 ') is dimensioned so as not to impede the propagation of the light rays reflected by said half portion -ellipsoid (111; 111 ').

11. Generator according to any one of claims 4 to 11, characterized in that said enclosure

(110) is closed at said opening (114) of the annular portion of the hemisphere, if necessary at the level of the second end of the tubular section of cylinder (113), by a porthole (127) of a transparent material , constituting, where appropriate, said positioning means.

12. Generator according to claim 11, characterized in that the window (127) is glued in a ring (129) of Teflon having an annular flange (130) allowing the fixing of said window (127) on said tubular section of cylinder.

13. Generator according to claim 12, characterized in that said flange (130) is glued to said tubular section of cylinder.

14. Generator according to claim 12, characterized in that said flange (130) is screwed onto said tubular section of cylinder, a seal (131) being disposed between the flange and the section.

15. Generator according to any one of claims 4 to 14, characterized in that said annular hemisphere portion (112), if necessary capped by said tubular section of cylinder, is movably mounted on said half-ellipsoid portion ( 111) and tightly by means of a seal (125).

16. Generator according to any one of claims 12 to 15, characterized in that said window

(127) is a block of silica (128).

17. Generator according to any one of claims 12 to 15, characterized in that said window

(127) consists of a lens glued in said ring (129).

18. Generator according to any one of claims 12 to 15, characterized in that the window consists of one end of an optical bar glued in said ring (129) and constituting a light guide.

19. Generator according to any one of claims 12 to 15 characterized in that the window (127) consists of a tip of a bundle of fibers bonded in said ring (129).

20. Generator according to any one of claims 12 to 19, characterized in that said ring is Teflon.

21. Generator according to claim 16, characterized in that said window (127) consists of a block of polished silica on its two inlet (133) and outlet (132) faces of the light beam generated by the lamp ( 117), the outlet face (132) being intended to receive the inlet surface of an optical bar constituting a light guide.

22. Generator according to claim 21, characterized in that the inlet (133) and outlet (132) faces are treated with anti-reflection.

23. Generator according to any one of Claims 16, 21 and 22, characterized in that the silica block is capable of letting pass only radiation having one or more selected wavelengths.

24. Generator according to one of claims 1 to 23, characterized in that the light source is a lamp connected to electrical supply means of the lamp fixed in sealed manner to the reflective enclosure.

25. Generator according to any one of claims 1 to 24, characterized in that the light source is a lamp of the short-arc discharge type of the metal iodide type, the arc of the lamp being placed at the focus (F _x ; F'i) located in the portion of ellipsoid.

26. Generator according to one of claims 24 and 25, characterized in that the electrical supply means comprise a socket connected to a ballast, the assembly being fixed in sealed manner to the enclosure.

27. Generator according to any one of claims 1 to 26, characterized in that the bottom of said portion of ellipsoid is pierced with a hole (118) for the passage of a lamp (117) constituting said light source, said lamp being mounted on a socket (119) connected to a sealed power cable (120) taken in a cable gland mounted on a sealed housing (121) incorporating said socket (119) and mounted at the through hole of the lamp on said enclosure, sealingly by means of a seal (124).

28. Generator according to one of claims 8 and 24 to 26, characterized in that a non-reflective hood

(115) extends from the concave portion of the ellipsoid to the entry of the positioning means.

29. Generator according to claim 28, characterized in that the hood (15) is a truncated cone.

30. Generator according to one of claims 28 and 29, characterized in that the portion of ellipsoid is mounted movable relative to the hood.

31. Generator according to claim 30, characterized in that the concave portion of the ellipsoid and the hood are connected by a seal surface (14G, 15A).

32. Generator according to claim 31, characterized in that the positioning means consist of a clamping and sealing ring.

33. Generator according to any one of claims 1 to 32, characterized in that said enclosure

(110) is made of aluminum or bronze and is formed by machining or embossing.

34. Generator according to any one of claims 1 to 32, characterized in that said enclosure is obtained by molding ceramic covered with an inner metal coating.

35. Generator according to claim 33, characterized in that said reflective surfaces consist of polished surfaces.

36. Generator according to claim 35, characterized in that the polished surfaces are covered with a surface coating of gold, rhodium, nickel, silver or aluminum.

37. Generator according to any one of claims 1 to 10, characterized in that said enclosure

(110 ') forms the walls of a sealed bulb (100'), the opening at the top of the bulb being hermetically sealed by a porthole made of a transparent material.

38. Generator according to claim 37, characterized in that said walls consist of glass covered with a metallic deposit.

39. Generator according to claim 37 or 38, characterized in that the reflecting surfaces are dichroic, reflecting in the visible range and allowing infrared radiation to pass.

40. Generator according to claim 38 or 39, characterized in that the portion of ellipsoid (111 ') has a reflective bottom crossed by electrodes for supplying tion (141, 142) electric of said light source, embedded in the glass.

41. Generator according to claim 40, characterized in that said light source comprises a substantially spherical sealed bulb (140) enveloping one end of said electrodes and containing means capable of producing a light arc by producing an electric discharge at said level electrodes.

42. Generator according to any one of claims 37 to 41 characterized in that said enclosure

(110 ') is under vacuum or contains a gas under low pressure.

43. Generator according to any one of claims 37 to 42, characterized in that the transparent window is formed by a portion of a cylinder or a pellet (127 ') of silica or quartz, a lens or an objective.

44. Generator according to claim 43, characterized in that the cylinder portion or the pellet has a planar surface for receiving the entry surface of a light guide.

45. Generator according to any one of claims 1 to 44, characterized in that it further comprises a network of thermally conductive cooling fins disposed around said enclosure (14B; 110, - 110 '), where appropriate also around said hood, these fins extending radially from the enclosure, if necessary also extending radially from said hood, to a heat shield comprising an internal wall in contact with the fins and made of thermally conductive material, an outer wall and an intermediate layer disposed between the inner and outer walls, made of a thermally insulating material, the fins delimiting spaces in communication with an air passage along the light beam.

46. Generator according to claim 45, characterized in that the internal wall and the fins are made of aluminum, the outer wall is made of aluminum or stainless steel, while the intermediate layer is made of Kevlar fabric or an asbestos fabric.

47. Generator according to claims 15 or 30 and 45 or 46, characterized in that the internal and external walls are cylindrical tubular sections, the cooling fins arranged around the enclosure being integral with two centering rings concentric with the wall internal and coming into contact with this .last in the assembled state of the generator.

48. Lighting assembly, characterized in that it comprises a light generator according to any one of claims 1 to 47, a light guide, and a diffuser, said light guide extending along the major axis of said portion of ellipsoid, substantially from said second focal point (F ₂ ; F ' ₂ ) of the ellipsoid defined by said portion of ellipsoid, and the light flux emerging from said light guide being diffused by the surface light diffuser reflective placed near the exit of the guide.

49. Lighting assembly according to claim

48, characterized in that it comprises a light guide (21) consisting of a rigid homogeneous bar of silica, PMMA or pure glass, a holding structure (23, 24) extending along this bar leaving remain a layer of air (22) along almost the entire lateral surface of this bar.

50. Lighting assembly according to any one of claims 48 and 49, characterized in that it comprises a light guide and in that the light flux emerging from the light guide is diffused by a light diffuser having throughout axial plane a V-shaped section with a reflecting surface, the top of which is placed near the outlet of the guide.

51. Lighting assembly according to any one of claims 48 to 50 and any one of claims 45 to 47, characterized in that the light guide is located in the air passage into which the beam enters.

52. Lighting assembly according to claim 51, characterized in that the air passage is at least approximately vertical.

53. Lighting assembly according to any one of claims 51 and 52, characterized in that the ellipsoid portion has an axis at least approximately vertical.