Abstract:
A dual mode visible and infrared lighthead ( 100 ) for use as a landing light or searchlight. The dual mode lighthead incorporates a modular design wherein at least one visible light source ( 200 ) and at least one infrared diode ( 302 ) are mounted into the rear sector ( 128 ) of a housing ( 102 ). Visible or infrared light is emitted out of the front sector ( 122 ) of the housing ( 102 ). Lenses ( 308 ) are installed onto the front sector ( 122 ) of housing ( 102 ) and sealed to protect the interior of the lighthead ( 100 ) from the elements.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/257,184 filed Dec. 20, 2000 entitled DUAL MODE VISIBLE AND INFRARED LIGHTHEAD. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to dual-mode visible and infrared lighting. Specifically, this invention relates to a dual mode visible and infrared lighthead for use with aircraft landing lights and searchlights, and for use with other vehicles.  
           [0004]    2. Description of the Related Art  
           [0005]    Aircraft generally have landing lights mounted thereon to provide illumination during taxi, take-off, and landing when visibility is reduced by darkness or adverse weather conditions. Landing lights may be mounted in a fixed position on the aircraft; alternatively, the landing lights may be pivotable by drive means to extend from the aircraft when needed, and retracted to reduce drag when not in use. Searchlights are pivotable by drive means similar to landing lights, but include an additional capability to rotate up to 360 degrees in a plane perpendicular to the extend-retract plane. Military and law enforcement helicopters commonly use searchlights to aim a beam of light in a desired direction to illuminate targets.  
           [0006]    With the advent of infra-red based Night Vision Imaging Systems (“NVIS”) for covert operations, there arose a need for landing lights and searchlights that were compatible with NVIS by producing infrared light for illuminating the selected landing and search areas while eliminating visible light. Early NVIS-compatible landing and search lights used infrared light filters installed over conventional visible lighting systems. A disadvantage of early NVIS-compatible lighting systems was that the flight crew could not switch from visible to NVIS modes during a mission, since the infrared filters were required to be installed and removed while the aircraft was on the ground. This disadvantage was overcome by prior dual mode lightheads containing both visible and infrared lighting elements, such as Snyder, et al. U.S. Pat. No. 5,695,272. Dual mode lightheads allow the flight crew to switch between visible and infrared lighting modes by simply applying electrical power to either the infrared or visible portions of the dual mode lighthead as desired.  
           [0007]    While prior dual mode lightheads offer significant advantages over early manually-installed filters, they suffer from several disadvantages. First, replacement of failed lamps is a cumbersome and difficult process owing to the segmented lens and filter assembly, which must be removed then re-sealed each time a lamp is replaced. This repair frequently causes damage to the reflectors, reducing the optical efficiency of the lighthead. In addition, dual mode lightheads typically emit lower light intensity than dedicated infrared or visible lighting systems, since the surface area on the lighthead available for the lighting system is divided between the visible and infrared portions. Further, prior dual mode lightheads utilize visible light sources coupled with infrared filters to produce the infrared light, generating high temperatures within the lighthead that can limit the life of the light elements, lenses, and sealing materials. There is a need for a dual mode lighthead that is easier to maintain, provides higher intensity light output, and operates at a lower temperature to extend lighthead component life.  
         SUMMARY OF THE INVENTION  
         [0008]    This invention is directed to a dual mode lighthead that is easier to re-lamp, provides improved light output, and generates less heat as compared to prior dual mode lightheads.  
           [0009]    Specifically, the present invention is a modular design incorporating a housing, preferably a cast aluminum housing. The housing is designed to accommodate installation of the lighting elements from the rear of the lighthead. This prevents contamination of the reflector with dirt, oil, or fingerprints that can reduce the optical efficiency of the reflector. Installing the lighting elements from the rear also reduces maintenance time, since the front lens does not have to be removed and then re-sealed.  
           [0010]    Replacement of prior front-mounted halogen lamps involves grasping the glass envelope of the lamp to install it into a socket. Because the presence of contaminating agents such as dirt, oil and fingerprints on the lamp&#39;s glass envelope can reduce the life of the lamp, maintenance personnel must use cotton gloves or other protective materials when replacing lamps. The present invention utilizes a visible light source that includes a base that allows maintenance personnel to handle and install the lamp from the rear of the lighthead without touching or otherwise contaminating the glass envelope. Further, the lamp base allows the visible light source to be easily installed and removed without the need for tools.  
           [0011]    The invention also utilizes high intensity infrared diodes in contrast to the filtered visible light sources used in prior lightheads. High intensity infrared diodes offer increased infrared light emission along with higher efficiency, reduced power consumption, longer life, and reduced heat generation. The high intensity infrared diodes also facilitate faster and simpler replacement due to their modular design.  
           [0012]    The present invention comprises a dual mode lighthead, comprising: a housing comprising front, rear, top, and bottom sectors; an attachment point connected with one of said sectors of said housing to connect the dual mode lighthead with means for positioning the lighthead; means for reflecting light mounted inside said housing, said means positioned to reflect light from the front sector of said housing; at least one high intensity infrared diode, said diode being installed into said housing from the rear sector of said housing and positioned to emit infrared light out of the front sector of said housing; at least one visible light source, said visible light source being installed into said housing from the rear sector of said housing such that said visible light source projects through said reflectors and emits light from the front sector of said housing; and at least one lens affixed to the front sector of said housing through which one of emitted visible and infrared light passes.  
           [0013]    These and other features will become better understood with reference to the following description, appended claims, and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIGS. 1 a  and  1   b  are views of the back and cover of the dual mode lighthead,  
         [0015]    [0015]FIG. 2 is a view of the visible light source,  
         [0016]    [0016]FIG. 3 is a view of the front of the dual mode lighthead, and  
         [0017]    [0017]FIG. 4 is an electrical schematic of the dual mode lighthead. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    A view of the back side of the dual mode lighthead  100  is shown in FIG. 1. Dual mode lighthead  100  includes a housing  102  having a rear sector  128 , a top sector  124 , and a bottom sector  126 . Housing  102  also includes a front sector  122 , shown in FIG. 3 and discussed below. Housing  102  is comprised of a cast or machined material, preferably aluminum, and may optionally include a plurality of cooling fins  104  to aid in the dispersion of heat generated by the light sources. Housing  102  further includes the parabolic reflector cavities  106  shaped to optimize the optical design for the visible light portion of lighthead  1   00  wherein the visible light is emitted from the front sector  122  of housing  102 . Lamp retainer slots  130  are cast or machined into the reflector cavities  106  to facilitate installation of the visible light sources  200 , discussed in greater detail below. Cavities  106  may also optionally include a plurality of heat-sink ribs  108  to help carry away heat generated by the visible light sources. The openings  110  accommodate the infrared light sources, and the openings  112  accommodate the visible light sources of lighthead  100 . An attachment point  114  is affixed to the bottom sector  126  of housing  102  and facilitates mounting of lighthead  100  directly to the aircraft structure, or optionally to the pivot means of a landing light or searchlight. A rear cover  116  protects the interior of lighthead  100  from the elements, being secured with a plurality of screws  118  to the receptacles  120 .  
         [0019]    The visible light source  200  is shown in FIG. 2. An incandescent lamp  202 , preferably halogen, is affixed to a lamp base  204 . The lamp base  204  provides a convenient surface for handling the visible light source  200  without contaminating the lamp  202 . One or more retaining springs  206  are attached to the lamp base  204  by conventional means such as rivets  208 . The lamp leads  210  facilitate connection of electrical power to the lamp  202 .  
         [0020]    The front of lighthead  100  is shown in FIG. 3. Referring to FIGS. 1, 2 and  3 , the infrared light sources  302 , preferably high intensity infrared diodes, are installed into openings  110  from the rear sector  128  of housing  102  and facing toward the front sector  122 . The visible light sources  200 , preferably halogen lamps, are installed into openings  112  from the rear sector  128  of housing  102  and facing toward the front sector  122  of housing  102 . As each visible light source  200  is pressed through an opening  112  of housing  102 , the retaining springs  206  spread and then snap into the lamp retainer slots  130 , firmly holding the visible light source  200  in place. The cast aluminum reflectors  306  are installed into cavities  106  to optimize light emission from visible light sources  200 . The lenses  308  are installed onto the front sector  122  of housing  102  and sealed to protect the interior of lighthead  100  from the elements. The attachment point  114  is affixed to the bottom sector  126  of housing  102  and facilitates mounting of lighthead  100  directly to the aircraft structure, or optionally to the pivot mechanism of a landing light or searchlight.  
         [0021]    As shown in FIG. 4, electrical power for the dual mode lighthead is supplied by the power input lines  416 ,  418 . Electrical power is controlled by a switch  402 , which provides logical electrical input signals to the logic circuit  410  of the control circuit  400  via the logic lines  420 ,  422 . If logic circuit  410  detects the presence of an electrical voltage on the “visible” logic line  420 , the electronic switch  412 , such as a power metal oxide semiconductor field effect transistor (MOSFET), is activated, causing the visible light sources  200  to emit visible light. If logic circuit  410  detects the presence of an electrical voltage on the “NVIS” logic line  422 , the driver control  414  activates the driver  408 . The driver  408 , such as an electrical current limiter, supplies a controlled amount of electrical current to the infrared light sources  302 , causing the infrared light sources  302  to emit infrared light. The logic circuit  410  turns off both the visible light sources  200  and the infrared light sources  302  when no voltage is detected on either of the logic lines  420 ,  422 . The logic circuit  410  also turns off both the visible light sources  200  and the infrared light sources  302  if an illegal logic condition exists, such as voltage present on both logic lines  420 ,  422 . The high-voltage protection filter  404  isolates electrical noise between the aircraft and the control circuit  400 . The power supply  406 , such as a voltage regulator, conditions the power from the aircraft to a voltage level suitable for the components in control circuit  400 .  
         [0022]    In operation, the dual mode lighthead is mounted to a fixed or retractable landing light mechanism, or a searchlight mechanism. A control switch  402 , located in the cockpit, is typically in the “Off” position causing electrical power to be removed from both the visible lamps  200  and the infrared light sources  302 . When the operator sets control switch  402  to the “visible” position, electronic switch  412  is activated, applying power to the visible light sources  200  and causing them to emit a bright visible light. If the operator places switch  402  in the “NVIS” position, driver  408  is actuated, causing the infrared light sources  302  to emit infrared light to facilitate searching, targeting, and landing during covert operations.  
         [0023]    Although the present invention has been shown and described herein with reference to a particular embodiment for a particular application, the present invention is not limited to aviation uses. Indeed, the present invention is immediately applicable to hand-held and stationary fixtures as well as all types of vehicular traffic, including automotive, marine, and railroad.