Abstract:
Disclosed is a luminaire designed for differential cooling of lamp light sources to create increase the cooling of temperature sensitive sections of a lamp using a shaped heat mirror  154  with aperture(s)  159  to direct airflow toward the temperature sensitive section(s)  33  of the lamp  30.

Description:
RELATED APPLICATION 
       [0001]    This application is a utility filing claiming priority of provisional application 61/316,327 filed on 22 Mar. 2010. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to an automated luminaire, specifically to a luminaire utilizing a high intensity discharge light source. More specifically to a system and method for cooling the light source. 
       BACKGROUND OF THE INVENTION 
       [0003]    Luminaires with automated and remotely controllable functionality are well known in the entertainment and architectural lighting markets. Such products are commonly used in theatres, television studios, concerts, theme parks, night clubs and other venues. A typical product will provide control over the pan and tilt functions of the luminaire allowing the operator to control the direction the luminaire is pointing and thus the position of the light beam on the stage or in the studio. This position control is often done via control of the luminaire&#39;s position in two orthogonal rotational axes usually referred to as pan and tilt. Many products provide control over other parameters such as the intensity, color, focus, beam size, beam shape and beam pattern. The beam pattern is often provided by a stencil or slide called a gobo which may be a steel, aluminum or etched glass pattern. The products manufactured by Robe Show Lighting such as the ColorSpot 700E are typical of the art. 
         [0004]      FIG. 1  illustrates a typical multiparameter automated luminaire system  10 . These systems commonly include a plurality of multiparameter automated luminaires  12  which typically each contain on-board a light source (not shown), light modulation devices, electric motors coupled to mechanical drives systems and control electronics (not shown). In addition to being connected to mains power either directly or through a power distribution system (not shown), each luminaire is connected in series or in parallel via data link  14  to one or more control desks  15 . The automated luminaire system  10  is typically controlled by an operator through the control desk  15 . Consequently, to affect this control both the control desk  15  and the individual luminaires typically include electronic circuitry as part of the electromechanical control system for controlling the automated lighting parameters. 
         [0005]      FIG. 2  illustrates a prior art automated luminaire  12  utilizing a high intensity discharge (HID) lamp. An HID lamp  21  contains an arc or plasma light source  22  which emits light. The emitted light is reflected and controlled by reflector  20  through an aperture or imaging gate  24 . The resultant light beam may be further constrained, shaped, colored and filtered by optical devices  26  which may include dichroic color filters, dimming shutters, and other optical devices well known in the art. The final output beam may be transmitted through output lenses  28  and  31  which may form a zoom lens system. Typically luminaires employing a HID type lamp employ a hot mirror  46  which is a window which transmits visible light and reflects non-visible energy radiating energy. 
         [0006]    Such prior art automated luminaires use a variety of technologies as the light sources for the optical system. For example it is well known to use incandescent lamps, high intensity discharge (HID) lamps, plasma lamps and LEDs as light sources in such a luminaire. Many of these light sources, particularly the HID and plasma lamps, need cooling to maintain them within correct operating temperature limits.  FIG. 3  illustrates one example of an HID lamp light source  30  and its major components. HID lamp  30  may comprise a sealed quartz envelope  37  with two contained electrodes  34  and  35  which are typically manufactured of tungsten. In operation an electrical arc is struck between electrodes  34  and  35  thus creating high temperature plasma and producing light. The specific mechanism and chemistry for the light production is beyond the scope of this patent and does not relate to the novelty of the invention. A critical area in the design of such lamps is the electrical connection from external power supplies to electrodes  34  and  35  which necessitates conveying the electrical power into the sealed quartz envelope  37  without compromising that seal. A common method utilized in the construction of such lamps is through thin foils  38  and  39 , typically manufactured of molybdenum, attached to the electrodes  34  and  35 . These thin foils  38  and  39  are squeezed between two opposing surfaces of the quartz envelope to provide a surrounding seal. These seal areas  32  and  33  are often referred to as the lamp ‘pinches’ as the quartz is pinched down onto the molybdenum foils to seal the lamp. The integrity of these seals or pinches is critical to the operation and longevity of the HID lamp as any leaks or breaks of the seal around the pinch may lead to premature failure of the lamp. An important factor in maintaining the integrity of the pinch areas  32  and  33  is controlling their temperature within closely defined parameters. The defined temperature ranges for the pinch areas  32  and  33  is often lower than that allowable for the remainder of the quartz envelope  37 . For this reason, the pinch areas  32  and  33  can be considered heat sensitive sections of the lamp  30 . In fact to ensure optimum performance of the chemical reactions taking place within the quartz envelope it may be desirable to maintain a temperature gradient along the lamp where the quartz envelope is at a first temperature while the pinches  32  and  33  are at a second, lower, temperature. Thus the luminaire designer must develop a cooling system which maintains this desired temperature gradient. A further constraint is the need for any cooling systems to avoid interfering with the reflector  31  or with any of the light beams emitted from the lamp or bounced from reflector  31 . 
         [0007]      FIG. 4  illustrates a prior art cooling system which seeks to maintain correct temperatures of the lamp  30  in particular the lamp envelope  37  and lamp pinches  32  and  33 . In this design one or more fans  41  are directed into the reflector  31  in such a manner as to direct external cool air around the lamp  30 . The cooling air may be directed directly on to the lamp as illustrated or may be directed at an angle so as to form a vortex of air around the lamp. A system like this, although somewhat effective, provides very little control of the desired temperature differentials between the lamp envelope  37  and pinches  32  and  33 . 
         [0008]      FIG. 5  illustrates a further prior art cooling system which seeks to maintain correct temperatures of the lamp  30  in particular the lamp envelope  37  and lamp pinches  32  and  33 . In this design the lamp  30  and associated reflector are contained within a lamp house  45  which gives better control of airflow. In particular the area of the lamp house where the light from the lamp and reflector are emitted is typically manufactured as a transparent window  46  of high temperature glass. Window  46  may be manufactured with an applied thin film coating such that window  46  transmits visible light but reflects back long wavelength radiation such as infrared and heat. Such a coated window is often called a ‘hot mirror’ as it reflects heat. This hot mirror serves to reduce the heat content of the light beam and thus reduces heat in the optical devices within the luminaire. It also produces a lower temperature output beam which is more comfortable for performers illuminated with the luminaire. The use of a hot mirror for this purpose is well known in the art. 
         [0009]    In the prior art design shown in  FIG. 5  one or more fans  43  and  44  force cool air into the lamp house  45 . Lamp house  45  is a sealed box with a single exit area  49  provided by an aperture on the rear of reflector  31  surrounding lamp  30 . Thus air entering through fans  43  and  44  is constrained to flow up and around  47  the front lip of reflector  31 , down past the lamp  30  and exits  48  via the rear aperture  49 . Such a system may provide better cooling for the rear lamp pinch  32 , as a large volume of cooler air must pass this pinch. However, the front pinch  33  is less well cooled. It is outside the main airflow  47  to  48  and only encounters slower moving turbulent airflow. Notwithstanding the issues this design offers significant improvements over that shown in  FIG. 4  and gives some degree of desired temperature differentiation between lamp body  37  and pinches  32  and  33 . 
         [0010]    There is a need for a cooling system for a lamp in an automated luminaire which offers improved cooling of lamp pinches and controlled differential cooling between lamp pinches and lamp envelope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein: 
           [0012]      FIG. 1  illustrates a typical automated lighting system; 
           [0013]      FIG. 2  illustrates a prior art system; 
           [0014]      FIG. 3  illustrates a typical light source in an automated luminaire; 
           [0015]      FIG. 4  illustrates a prior art lamp cooling system; 
           [0016]      FIG. 5  illustrates a prior art lamp cooling system; 
           [0017]      FIG. 6  illustrates an embodiment of the invention; 
           [0018]      FIG. 7  illustrates an alternative embodiment of the invention; 
           [0019]      FIG. 8  illustrates a perspective view of an alternative embodiment of the invention; 
           [0020]      FIG. 9  illustrates a further perspective view of an alternative embodiment of the invention; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Preferred embodiments of the present invention are illustrated in the FIGUREs, like numerals being used to refer to like and corresponding parts of the various drawings. 
         [0022]    The present invention generally relates to an automated luminaire, specifically to a luminaire utilizing a high intensity discharge light source and the lamp cooling systems contained therein. 
         [0023]      FIG. 6  illustrates an embodiment of the invention utilizing an HID light source  30  in an automated luminaire. HID lamp  30  may comprise a sealed quartz envelope  37  with two contained electrodes  34  and  35  which are typically manufactured of tungsten. In operation an electrical arc is struck between electrodes  34  and  35  thus creating high temperature plasma and producing light. The electrical connection from external power supplies to electrodes  34  and  35  is through thin foils  38  and  39 , typically manufactured of molybdenum, attached to the electrodes  34  and  35 . These thin foils  38  and  39  are squeezed between two opposing surfaces of the quartz envelope to provide a surrounding seal. These seal areas  32  and  33  are often referred to as the lamp ‘pinches’ as the quartz is pinched down onto the molybdenum foils to seal the lamp. HID lamp  30  may emit significant quantities of ultra violet (UV) and infrared (IR) energy as well as the desired visible light. 
         [0024]    In  FIG. 6  the lamp  30  and associated reflector  31  are contained within a lamp house  53 . The area of the lamp house  53  where the light from the lamp and reflector is emitted to the optical systems of the luminaire may be manufactured as a transparent window  54  of a high temperature glass or quartz. Window  54  may further be manufactured with an applied thin film coating such that window  54  transmits visible light but reflects back long wavelength radiation such as infrared and heat. Such a coated window is often called a ‘hot mirror’ as it reflects heat. This hot mirror serves to reduce the heat content of the light beam and thus reduces heat in the optical devices within the luminaire. Window  54  contains a central aperture  59  which provides a path for air to enter or leave the lamp house. Although aperture  59  will allow some long wavelength or infra red radiation to exit the lamp house without passing through the optical coatings on window  54 , aperture  59  is small compared to window  54  and thus the amount of long wavelength or infra red radiation exiting is minimal and not sufficient to be of any concern to optical devices in the luminaire. 
         [0025]    In operation one or more fans  51  and  52  extract air from lamp house  53 . Lamp house  53  is a partially sealed box with two air entrance areas provided by aperture  59  in window  54  and by a further aperture  60  on the rear of reflector  31  surrounding lamp  30 . As air is extracted through fans  51  and  52  cool air  56  will be drawn into lamp house  53  primarily through aperture  59  and, to a lesser extent as it may be smaller and more constricted, aperture  60 . Air  56  entering through aperture  59  will tend to impinge on the front pinch  33  of lamp  30 . This air will then circulate around lamp  30  before exiting  55  around the lip of reflector  31  and through fans  51  and  52 . Although two fans  51  and  52  are illustrated here the invention is not so limited and any number of fans may be utilized. By adjusting the relative sizes of apertures  59  and  60  the desired fine control of the cooling of pinches  32  and  33  compared to that of lamp envelope  37  may be achieved such that all lamp temperatures are optimized. 
         [0026]    To further assist the cooling of rear pinch  32  a further fan  57  may impinge cooling air  58  directly onto the rear pinch area. In this case aperture  60  may be reduced in size or closed off entirely such that all air extracted by fans  51  and  52  will enter through aperture  59  to maximize cooling of the front pinch  33 . In this manner independent temperature control of the two pinches may be further refined. For example, the rear pinch  32  fan  57  can provide additional cooling of the rear pinch to correct for temperature imbalance between the two pinches. 
         [0027]    In alternative embodiments of the invention fans  51  and  52  may input air into the lamp house  53  instead of extracting it. In that case air will be reversed and will exit through apertures  59  and  60 . 
         [0028]    Although the figures shown here are of embodiments with imaging optics that are capable of producing projected images from gobo wheels and other pattern producing optical devices, the invention is not so limited and the light output from the optical system may be imaging where a focused or defocused image is projected, or non-imaging where a diffuse soft edged light beam is produced, without detracting from the spirit of the invention. The invention may be used as a lamp cooling system with optical systems commonly known as spot, wash, beam or other optical systems known in the art. 
         [0029]    In yet further embodiments, the cooling system may be actively controlled using feedback from the lamp control system and temperature probes measuring the ambient temperature in and around the lamp and/or lamp house and controlling the speed of fans  51 ,  52  and  57  accordingly. Separate sensors may be used to sense temperatures at each lamp pinch and/or the central envelope and/or other locations inside and outside the luminaire house. Such systems may also use the power provided to lamp  30  to control the speed of cooling fans. For example, if the user commands the lamp to dim down to 20% output through the control console and link as shown in  FIG. 1  then the cooling system may respond to this by reducing fan speeds to a level commensurate with the power level being provided to lamp  30 . The commensurate level of fan speed is determined as a function of the heat power to heat generation curve of the source taken together with the cooling to fan speed curve(s) of for an internal external temperature differential. The fan speed may also be controlled based on the temperature input from the various sensors or the differential of temperatures across sensors. 
         [0030]    In other embodiments the lamp cooling and fan speeds may be controlled through commands received over the communication link  14  shown in  FIG. 1 . Such commands may be transmitted over protocols including but not limited to industry standard protocols DMX512, RDM, ACN, Artnet, MIDI and/or Ethernet. 
         [0031]      FIG. 7  illustrates an alternative embodiment of the invention as it may be used in an automated luminaire. Lamp  30  has pinches  32  and  33 . In this embodiment the output window  154  which may have a hot mirror thin film coating is divided into segments  161  and  162  which are mounted at an angle to each other and to a plane normal to the optical axis of the luminaire. Notches  161  and  163  in the edges of segments  160  and  162  form an aperture  159 . This angle  155  between segments  161  and  162  prevents multiple reflections between the surfaces of the window  154  and downstream optics. It further serves to direct reflected infrared and other long wavelength radiation away from lamp  30 . The output window may be planar or constructed in any shape as well known in the art without detracting from the spirit of the invention. The output window may further be mounted at any angle relative to the output beam and optical axis. Rather than segments the window  154  can also be a single singe piece and my also have different shapes such as a conical shape. The shape and position of the aperture  163  along the optical axis  150  of the luminaire is optimized to regulate the airflow and therefore the cooling of the lamp pinches and the lamp envelope based on the airflow dynamics of the luminaires housing chambers. In the embodiments shown the output window  154  forms part of the boundary of a chamber of the luminaire&#39;s housing that holds the lamp and light source and the chamber of the housing that holds the rest of the optics such that air flow by the fans out of the lamp housing chamber causes air to flow through the window  154  aperture  159  into the lamp housing chamber from the chamber housing the other optics of the luminaire. This specific configuration is not necessarily the only housing or chamber configuration. However for the purposes of this cooling system it is preferable that the components be housed in a manner that airflow is encouraged to flow through the window aperture. 
         [0032]    The system as illustrated in  FIG. 7  is enclosed in a lamp house (not shown) with fans (not shown) to extract air as shown in  FIG. 6 . During operation these fans will pull air from the lamp house such that air  56  will be drawn into the system through aperture  63 . This air  56  will impinge on lamp  30  in particular on the front pinch  33 . Additionally air from a further fan (not shown) is directed through duct  64  to impinge on the rear pinch  32  of lamp  30 . By these means lamp  30  and pinches  32  and  33  are optimally cooled. 
         [0033]      FIG. 8  illustrates a wider perspective view of the embodiment shown in  FIG. 7 . Fans  51  and  52  extract air  71  and  72  from a lamp house causing air  73  to be drawn into the lamp house through aperture  63  in an output window formed by two segments  61  and  62 . Segments  61  and  62  may be manufactured with an applied thin film coating such that segments  61  and  62  transmit visible light but reflect back long wavelength radiation such as infrared and heat and act as a hot mirror. Air entering aperture  63  is directed towards the lamp and serves to cool it and its associated pinch as herein described. Additionally air is directed from a further fan (not shown) through exit aperture  65  of duct  64  onto the rear portion of the lamp and associated pinch. 
         [0034]      FIG. 9  illustrates another perspective view of the exemplary embodiment of the invention shown in  FIG. 7 . Fans  51  and  52  extract air  71  and  72  from a lamp house causing air  73  to be drawn into the lamp house through aperture  63  in an output window formed by two segments  61  and  62 . Segments  61  and  62  may be manufactured with an applied thin film coating such that segments  61  and  62  transmit visible light but reflect back long wavelength radiation such as infrared and heat and act as a hot mirror. Air entering aperture  63  is directed towards the lamp and serves to cool it and its associated pinch as herein described. Additionally air is directed from a further fan  57  through exit aperture  65  of duct  64  onto the rear portion of the lamp and associated pinch. 
         [0035]    In further embodiments of the embodiments illustrated in  FIG. 6  and  FIG. 7   FIG. 8  and  FIG. 9 , employ a reflector that primarily reflects visible light and primarily passes or absorbs non-visible energy radiating both from the light source  30  and/or as reflected back by the hot mirror  54  and  154  respectively. 
         [0036]    While the disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as disclosed herein. The disclosure has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the disclosure.