Abstract:
A light beam projector has a light source and a reflector arranged to have light generated by the light source converge into a light beam. The reflector has a hollow curved surface with a focal point where the light source is positioned, and a filter able to change the color of the light beam based on the angle of incidence of the beam on the filter. The filter has a plurality of filter elements arranged by sectors to form a diaphragm between the light source and the light beam outlet from the projector. In order to change the angle of incidence of the light beam on the filter elements, the sectors are able to rotate on their axes from a closed position, in which they fully intercept the light beam, to an open position, in which they do not intercept the light beam, as well as to all intermediate positions. The light beam projector has at least two filtering systems, one including at least one of the diaphragms, placed one after the other along the path of the light beam. Each sector forming the diaphragms can be rotated independently of the other sectors.

Description:
BACKGROUND OF THE INVENTION 
     The present invention refers to a light beam projector comprising a light source and a reflecting means, which are arranged for converging the light generated by the light source into a light beam, such reflecting means having a hollow curved surface and a focal point located where the light source is positioned, means for filtering the light beam, able to change its colour based on the angle of incidence of the beam on them, said filtering means comprising a plurality of filters arranged by sectors to form a diaphragm interposed between the light source and the light beam output from the projector, where said sectors, in order to change the angle of incidence of the light beam on the filters, can rotate on their own axis, to move from a closed position where they fully intercept the light beam, to an open position where such a light beam is not intercepted, as well as to all intermediate positions. 
     In particular, the present invention refers to light beam projectors for medium, high and very high lighting power. 
     According to the state of the art, several methods are known for changing the colour of the light beam emitted by a source of light. Many systems use coloured gel interposed in the light beam for changing its colour and, additionally, they make use of various mechanical techniques for changing different coloured gel associated to a single lighting device. 
     However, these systems have considerable drawbacks, since they do not ensure continuous colour corrections nor obtaining small changes to the above corrections. 
     Other recent systems have improved the system for changing the colour of the light beam, using dichroic filters instead of coloured gel. 
     These filters are formed by a plurality of layers, which may have a low or high refraction index, alternatively. According to the type and number of the layers of a filter, the latter takes a basic coloration, such as magenta, cyan, yellow, etc. 
     In the state of the art, it is also known that such dichroic filters have very peculiar features, since they operate on an interference principle, i.e. substantially separating two colours from a white light source, one of these colours being transferred and the other colour complementary to the first one, being reflected. 
     Moreover, changing the angle of incidence (reference is made to the patent U.S. Pat. No. 3,085,468) of a light beam with respect to a dichroic filter, the colour spectrum (i.e. the wavelength of the coloured light) transmitted through the filter can be changed, i.e. changing the colour of the light beam exiting the filter. 
     A problem frequently arising when using the above means for changing the colour of the light beam, in particular when high power systems are concerned, is caused by overheating of the equipment inside the lighting systems. Quite often, in fact, free air circulation is not allowed inside them; additionally, the light not being transmitted, i.e. reflected by the filters, will directly affect the lamp and other internal components of the equipment, overheating these components. 
     Another problem associated to the known systems is that only one colour shade of the light beam emitted by the system can be obtained each time. These systems, in fact, generally use diaphragms with dichroic filters, which are so arranged to be intercepted by a light beam, where the dichroic filters of each diaphragm have the same features and have all the same angle of rotation to the direction of the light beam. 
     This causes a certain rigidity in selecting the light that can be obtained from said known devices. 
     SUMMARY OF THE INVENTION 
     In this frame, it is the main object of the present invention to provide a light beam projector, which favours a continuous air circulation inside the projector itself, avoiding projector overheating through a correct positioning of the adjustable dichroic filters and obtaining, additionally, a light beam with various continuously variable simultaneous colorations. 
     In order to achieve such aims, it is the object of the present invention to provide a light beam projector incorporating the features of the annexed claims, which are integral part of the present description. 
     Further objects, features and advantages of the present invention will become apparent from the following detailed description and annexed drawings, which are supplied by way of non limiting example, wherein: 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a basic view of a light beam projector incorporating the features of the present invention; 
         FIG. 2  shows a front section of a diaphragm fitted with flat filters; 
         FIG. 3  shows a plan view of a diaphragm with flat filters divided in three sectors, each one of 120 degrees, which are positioned according to the features of the present invention; 
         FIG. 4  shows a schematic section of the light beam projector, highlighting the directions of the air flow; 
         FIG. 4A  shows a schematic section of the light beam projector according to the present invention; 
         FIG. 5  shows a side view of a mechanism for rotating the flat dichroic filters in each sector of the flat filters diaphragm, according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the descriptions of the drawings,  FIG. 1  is representing a light beam projector, which comprises as usual a light source consisting of a lamp  3  (which may have a short arc) with the electrodes  4  and  5 , located substantially on the same axis. 
     The light produced by the lamp  3  is reflected by a parabola  7 , which forms a reflecting surface producing a light beam with either a constant or diverging cross section. 
     According to the present invention, the projector comprises at least a tubular wall  6 , whose axis matches substantially the axis of the parabola  7 ; when the wall is in its operating position, it will embrace and enclose the lamp  3  laterally; the tubular wall  6  may also take a rest position, in which case it is placed below the parabola  7 , so as not to interfere with the light emitted by the light source, or it can be located in an intermediate position between the operating and rest positions, allowing different interference degrees with the light beam. 
     Moreover, the wall  6  may consist of different materials, which are provided for obtaining various scopes according to the specific material being used for its manufacture and/or machining. 
     It is known, for instance, how a sanding treatment of a glass surface may produce a plurality of concavities on the treated surface. 
     When this “frosted” tubular wall is placed in its operating position with respect to the light source, radiations are deviated by the small concavities and the light direction changed before reaching the parabola  7 ; when these diverted radiations are reflected by the parabola  7 , a “frosted” diffused light is obtained. 
     Should a filter have a tubular wall  6  with different “frosting” degrees on various portions of its surface in the vertical direction, variable photometric features of the output light would be obtained according to its position around the lamp  3 . 
     The tubular wall  6  may also be a steel tube (or opaque material) placed not too distant around the lamp  3 ; when the tube is completely enclosing the lamp, it will operate like a shutter and fully hinder the light from going through and be reflected by the parabola. 
     This shutter, which may be formed by fully closed or partially open portions (or totally opaque or partially opaque portions), operates like a damper or “mechanical dimmer”, because it will let either major or minor light portions go through according to its position around the lamp. 
     A tubular wall  6  may also consist of just one filter submitted to a dichroic treatment ensuring one or more corrections for changing the colour temperature, i.e. attenuating determined colour temperature degrees before the light can hit the parabola  7  for back reflection. 
     In the instance of a lamp operating with 6500 Kelvin (K) degrees, should a filter be inserted for reducing its colour temperature by 2000 K in one filter portion and by 800 K in another filter portion, it would be possible for the equipment to reach various colour temperature degrees using only one lamp, depending on the filter portion interlaid between the lamp  3  and the parabola  7  (in the above example, the result would be: inserting a certain portion, the colour temperature would be: 6500 K−2000 K=4500 K. Moving the filter so as to interlay the other portion, which has undergone a dichroic treatment for reducing 800 K, the result would be: 6500 K−800 k=5700 K). Thus, the lights would be obtained with a different colour temperature suitable for various employment conditions, such as exterior lighting, interior lighting, and so on. 
     Moreover, a tubular wall  6  can undergo a dichroic treatment for obtaining several colorations in a vertical direction on the dichroic tube itself; thus, a plurality of different colorations of the resulting light beam may be obtained, depending on the wall portion being interlaid for intercepting the light emitted by the light source before being reflected by the parabola. 
     Obviously, the projector can be manufactured with a plurality of tubular walls  6  made from different materials and differently featured or in the various portions of the tubular wall itself, in order to obtain the results previously described according to the purposes to be reached, interposing the tubular wall made from the most appropriate material and/or machining between the light source and the reflecting means. 
     Anyway, since the tubular wall  6  is positioned at a short distance around the lamp, it will ensure free air flow between the wall and the lamp for the cooling of the lamp and whole equipment. 
     As it can be noticed in  FIG. 1 , a second portion of the light beam projector according to the present invention is also shown, in which a number of diaphragms  8 ,  9  and  10  are positioned, each one of them divided in three sectors  12 ,  13  and  14 ;  15 ,  16  and  17 ;  18 ,  19  and  20 , respectively, and provided with adjustable dichroic filters, according to the present invention. 
     As better detailed in  FIG. 2 , where the front section of one diaphragm is represented, each adjustable dichroic filter is preferably placed in a non perpendicular position to the axis of the light beam  22 . 
     As mentioned above, dichroic filters operate according to an interference principle, i.e. substantially separating two colours from a white light source, one of these colours being transmitted and the other complementary to the first one, being reflected. Through the position of the dichroic filters of the present invention preferably not perpendicular to the light beam, the light ray complementary to the other ray  24  transmitted over the filter, i.e. the reflected ray  23 , it not reflected again on the lamp  3  and other internal components of the lighting equipment, avoiding overheating. 
     With reference to the  FIG. 3  describing any of the diaphragms  8 ;  9 ;  10  containing flat dichroic filters object of the present invention, it will be noticed how the filters are divided in three different sectors  12 ,  13  and  14 ; or  15 ,  16  and  17 ; or  18 ,  19  and  20 , which occupy equal portions with respect to the lamp axis, one on top of the other; in this instance, in fact, the diaphragms equipped with filters are divided in sectors or panels, each one of 120 degrees. 
     As it will be easily noticed, the filters forming each one of the three sectors  12 ,  13  and  14 ; or  15 ,  16  and  17 ; or  18 ,  19  and  20 , can be rotated on their own axis by means of a mechanical transmission mechanism  25 - 26  interconnecting them and a motor  11 . Each sector has its own motor  11  operating independently from the others. 
     The dichroic filters in each sector  12 ,  13  and  14 ; or  15 ,  16  and  17 ; or  18 ,  19  and  20 , can move simultaneously all together from a closed position, where they are able to totally intercept the light beam from the light source, to an open position where the light beam is not intercepted. 
     It may also be appreciated how at least a few degrees of light may pass without being filtered through the various sectors  12 ,  13  and  14 ; or  15 ,  16  and  17 ; or  18 ,  19  and  20  equipped with such filters, when they are in an intermediate position between the fully open position and the fully closed position; in these instances, the unfiltered light will join the filtered coloured light and obtain different saturation degrees of the resulting light, according to the rotation degree of the adjustable filters on their own axis. 
     As it will be noticed from  FIG. 3 , the filters pertaining to each sector of the filters diaphragm  8  are independent with respect to the filters of the other sectors forming the various diaphragms, and they may even have different colorations in the various sectors. In the latter instance, light beams of different colour may even be generated simultaneously. 
     In a most common case, the filters of the sector  12  may have a yellow colour, those of the sector  13  a magenta colour and those of the sector  13  a cyan colour; filter colorations are practically rotated by 120 degrees between a filters diaphragm  8  and the subsequent one  9  overlaying, so that in this diaphragm  9  the filters of the sector  15  may have a cyan colour, those of the sector  16  a yellow colour and those of the sector  17  a magenta colour; the position of the filters diaphragm  10  is rotated by further 120 degrees for the filters of the sector  18  to take the magenta colour, those of the sector  19  the cyan colour and those of the sector  20  the yellow colour. 
     Thus, in order to obtain one of the three basic colours, i.e. yellow, magenta and cyan, and fully intercept the light beam by giving it a colouring and a uniform wavelength, only one sector or panel of each diaphragm should remain in its closed position for intercepting the light beam emitted by the light source, i.e. leaving the other two sectors in their open position for free circulation of the air generated by a fan  2  located at the base of the equipment. 
     As it will be noticed from  FIG. 4 , the air generated by the fan  2  can freely flow in the space between the tubular wall  6  and the lamp  3 , where a first significant cooling is operated, then it will rise and reach the first diaphragm  8  with flat filters, in which at least one of the sectors remains forcedly open all the time (if all the sectors of all flat filters diaphragms remain closed, the light beam would have a black coloration, which is not convenient and should never happen in the practice; moreover, the projector would have no ventilation), overcome it and flow over to the subsequent diaphragms  9  and  10  with flat filters, going through them the same way, finally flowing out of the equipment through a set of openings located in the anti-reverberation disk  21 . 
       FIG. 4   a  is representing a more detailed view of a possible solution of the present invention. In this figure, in fact, only one of the three sectors forming each diaphragm  8 ,  9  and  10  with flat dichroic filters remains in its open position (i.e. sectors  13 ,  17  and  18 ), so as not to intercept the light beam emitted by the light source and ensure free circulation of the air flow  30  generated by the fan  2 . In this instance, coloration of the light beam being generated will be provided by the composition of two of the three basic or primary colours. 
     The air flow  30  will be able to freely circulate inside the equipment, cool down each internal component and then flow out of the equipment, finding no hindrances over its path from the fan  2  to the openings located on the anti-reverberation disk  21 . 
     Obviously, different configurations can be provided in alternative to the one described for the position and number of adjustable dichroic filters in every sector of each diaphragm  8 ,  9  and  10 , without departing from the novelty of the innovative idea of the present invention. 
       FIG. 5  is representing a possible mechanical system, which may be used for rotating the dichroic filters  31  pertaining to one same sector on their own axis; each filter being connected on one end to a rotary mechanism  25  for receiving its own motion, and on the other end to a special support  27  fastening it to the diaphragm outer wall. 
     These rotary mechanisms  25  are interconnected through a connecting rod-crank system  26 ; an articulated joint  28  connects the connecting rod-crank system to the axis  29  of the linear motor  11 . 
     Thus, rotation of the dichroic filters  31  is determined by the linear motion of the motor axis, being the latter controlled by a microprocessor with a special software (not described). 
     Alternative mechanical systems to the one described above for the motion of the dichroic filters  31  may also be manufactured using gear systems, e.g. a worm screw or a belt connected to a pulley, and any other common mechanisms known in the state of the art. 
     Also the number of flat filter sets according to the present invention may change: i.e. using only two sets of filters, each one with a determined number of sectors such to correct a coloured light beam through one or more tubular walls having one or more colour corrections on their surface. 
     From the above description the advantages of the present invention are clear. 
     In particular, free air circulation is provided inside the projector to avoid overheating of the components housed therein. 
     Moreover, since the sectors of the diaphragms with dichroic filters are not perpendicular to the light beam intercepted by them, all the heat reflected by the rays not flowing through the dichroic filters will be prevented from being sent back to the innermost side of the projector, adding to its overheating. 
     According to another advantage of the present invention, light beams of different colour shades can be generated thanks to differentiation of the basic colour and driving independence of the various filters forming the diaphragms interposed on the light beam path. 
     Moreover, a simultaneous use of the tubular wall surrounding the lamp and the diaphragms will ensure a more flexible generation of each desired coloured light beam, on one hand, and a simpler calibration of the desired final colour, on the other. 
     In the latter instance, a minor number of diaphragms with adjustable dichroic filters may also be utilized, while obtaining the same colour change capabilities and using less space in the vertical direction. 
     Finally, interlaying the tubular wall appropriately manufactured for absorbing a certain amount of colour temperature of the light generated by the lamp will produce light beams with a different colour temperature from the lamp generating them, so as to suitably adapt the projector for a different number of uses. 
     A dimmer effect can also be obtained on the light generated by the projector, interlaying the tubular wall made from opaque material or material with slits to a more or less extent on the light generated by the lamp. 
     Therefore, as it can be easily realized, the present invention is not merely restricted to the projector and its various components described above, but it can be subject to changes, improvement, replacement of equivalent parts and elements, without departing from the innovative idea of the present invention, as clearly detailed in the following claims. 
     A possible implementation is to provide the projector with an automatic equipment for setting the colour temperature generated by the projector itself. In this instance, the projector may be equipped with a closed loop control system of the colour temperature, in which a colour temperature sensor will detect the temperature of the light beam from the projector, compare it to a preset value and in case of a diverging result operate a motor-driven system to move the tubular wall  6  until the absorption of Kelvin degrees is such to produce a light beam with the desired colour temperature.