Abstract:
A light is provided having a base unit, an arm extending from the base unit, and a lamp head coupled to the arm. The lamp head includes an LED configured to provide light based on an input drive current, an optical mixing element configured to collect the light produced by the LED and a zoom lens configured to adjust an output size of a spot generated by the light collected in the mixing element. A controller receives DC power from the base unit through the arm. The controller is configured to set the input drive current for the LED to control an output light density of the spot in response to an operator selected input and configured to adjust the output light density of the spot in response to a change in the size of the spot.

Description:
CROSS REFERENCE 
       [0001]    This application is a submission under 35 U.S.C. §371 of International Patent Application No. PCT/US2011/024850 filed Feb. 15, 2011 (pending), which claims priority to U.S. Provisional Patent Application Ser. No. 61/304,848, filed Feb. 16, 2010 (expired), the disclosures of which are incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application relates generally to the field of illumination, and more particularly to an LED illumination device for use by a physician or health care provider. 
       BACKGROUND OF THE INVENTION 
       [0003]    Health care providers, during examinations and procedures, need additional lighting to better diagnose and treat different health conditions. It is important for lighting to have proper intensity, color temperature, and uniformity so that the provider is not mislead when making a diagnosis during the examination or procedure. The examination light may be used in multiple types of examinations and procedures; therefore, it is important for the design of the light to allow for the proper reach and positioning in order to illuminate any part of the body by the health care professional. It is equally important that once positioned, the light does not drift from this location, which can cause inconvenience especially when working in a sterile field. Examination lights with smaller product profiles are desirable as they assist in giving the provider better access to the patient. 
         [0004]    Contemporary examination lights are generally not designed specifically for interaction with examination and procedure chairs and tables, limiting their effectiveness when used as a system. The contemporary exam lights are typically caster based, wall mounted, or ceiling mounted making them cumbersome for users and in some cases preventing accessibility to a patient. In other cases, these lights may assist in increasing room clutter. 
         [0005]    Contemporary examination lights generally use halogen bulbs and fiber optic bundles that produce intense amounts of heat. Because of the halogen bulb, some lights require larger product envelopes. Furthermore, the halogen bulbs utilized in the contemporary lights generally offer only hundreds to a few thousand hours of life. Blown bulbs may be costly and inconvenient especially if the failure of the bulb occurs in the middle of an examination or procedure. Moreover, as these light sources are manipulated to adjust a spot size of the light, the spots generally lose intensity as the spot size is increased, having health care professionals choose between more intense light or a larger spot of light. Therefore there is a need in the art to improve the life of the light source without degrading light intensity would be a noticeable improvement. 
         [0006]    Some examinations and procedures may be hours in duration. Heat generated from contemporary lamps can become uncomfortable for both the provider and patient. Some contemporary lamps attempt to place the light source in the base of the light, away from the provider and the patient, but these configurations then require transmitting the light from the base of the light to the lamp head as well as fans or other heat dissipation components which are a source of noise and add cost to the overall system. Therefore there is also a need in the art for a light that does not produce an abundance of heat over long periods of time. 
         [0007]    Additionally, since it is likely the examination light could come into contact with different substances during the examination or procedure, the design of the light should provide some protection against the ingress of fluids. This also helps to ensure satisfactory operation of the light when cleaned with different disinfectants. 
       SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the invention not only focus on designing an examination light, but are also focused on the interaction between a user and the light. Embodiments of the examination light provide mounting locations that allow proper reach of the light source, provide a home storage position, and assist in reducing floor clutter by attaching the light to an examination chair or examination table. Mounting directly to the examination chair or table allows for maximum accessibility to the patient and may aesthetically blend in with the chair or table, which also may assist in making the exam and procedure rooms more inviting to a patient. 
         [0009]    In some embodiments, the location of the power switch is on the light head. This location may assist in eliminating the need for the user to reach away from the light head, which may be uncomfortable for the provider and patient. A recessed location of the power switch, in some embodiments, may make it easy to locate and may assist in preventing accidental activation of the switch. 
         [0010]    The optical system, in some embodiments, allows light intensity and uniformity to be met in a very short distance while using a LED as the light source, thus avoiding some of the issues related to contemporary halogen bulb lights. This short distance allows for a smaller light head, which adds to the ergonomics of the design and assists in positioning the light without obstructing the view of the healthcare provider. The LED light source produces a light beam that generally does not generate heat at the illumination site. Additionally, a predicted life for the LED is approximately a 50,000 hour life versus a few thousands of hours of their counterpart halogen bulbs. 
         [0011]    Embodiments may also include a controller which is configured to drive more current through the LED effectively generating more foot-candles or lux as the spot size diameter is increased. This may assist in offsetting any loss in light intensity allowing for a system that can maintain intensity throughout the spot size range. A healthcare provider may now be able to increase the spot size without suffering a loss of light intensity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention. 
           [0013]      FIG. 1  is a perspective view of an embodiment of the exam light. 
           [0014]      FIG. 2  is a detailed view of the base of the exam light in  FIG. 1 . 
           [0015]      FIG. 3  is a detailed view of the head of the exam light in  FIG. 1 . 
           [0016]      FIG. 4  is an exploded view of components of the head of the exam light in  FIG. 3 . 
           [0017]      FIG. 4A  is a detailed view of components in  FIG. 4 . 
           [0018]      FIG. 5  is a cross section view of the head of the exam light in  FIG. 3  with the optical lenses in a first position. 
           [0019]      FIG. 6  is a detailed view of the optical elements in the position in  FIG. 5   
           [0020]      FIG. 7  is a detailed view of the optical mixing element in  FIG. 6 . 
           [0021]      FIG. 8  is a cross section view of the head of the exam light in  FIG. 2  with the optical lenses in a second position. 
           [0022]      FIG. 9  is a detailed view of the optical elements in the position in  FIG. 8 . 
           [0023]      FIG. 10  is a block diagram of the components controlling the intensity of the light emitted from the exam light of  FIG. 1 . 
       
    
    
       [0024]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity or illustration. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Embodiments of the invention provide an examination light that delivers lighting with proper intensity, color temperature and uniformity to assist in enabling a medical provider in providing proper diagnoses. Embodiments allow the light to be used in multiple types of examinations and procedures by providing an adequate reach and positioning to assist in illuminating any part of the body without drifting from its location. Embodiments of the invention also allow for the ability to adjust the spot size from a minimum range to a maximum range assisting the provider in being able to direct light only where needed. Additionally, embodiments of the invention also provide an auto-intensity functionality, driving more light to an increased spot size, assisting in minimizing intensity roll-off. 
         [0026]    Turning now the embodiment of the examination light  20  in  FIG. 1 , the light  20  includes a base component  22 , an arm  24  with both rigid  24   a  and flexible  24   b  sections, and a lamp head  26 . The combination of rigid  24   a  and flexible  24   b  sections of the arm  24  assist in moving the lamp head  26  to various positions by the health care provider and assists the provider in directing the light toward the examination and/or treatment area on a patient. The base component  22  of the examination light  20  provides a mounting structure (not shown) which allows the light  20  to be mounted to an examination table, chair, or other fixture, such that the examination light  20  is available for use by the health care provider. 
         [0027]    The examination light  20  is electrically powered through an electrical connection to an AC source in a wall socket or the like. As seen in  FIG. 2 , the source of electrical AC power enters the base component  22  at connection  28  which is in turn electrically connected to a circuit board  30 . Components on the circuit board  30  convert the AC power to DC which is used to power the components in the lamp head  26 . The DC power is delivered to the lamp head  26  through wires extending from the circuit board  30  through the arm  24 . By placing the electrical conversion circuitry in the base component  22 , any heat generated by that circuitry is located away from the health care provider and the patient. 
         [0028]      FIG. 3  provides additional detail for the lamp head  26 . The examination lamp  20  is controlled by a control area  32  on the lamp head  26 . In some embodiments, this control area  32  may include a single button  34  which may be used to turn the light  20  on, cycle through preset brightness levels, and turn the light  20  off. In other embodiments, multiple buttons  34  may be employed with one button being dedicated to turning the light  20  on and off and other buttons being used to adjust the brightness of the light  20 . The control area  32  is located on a proximal portion  36  of the lamp head  26 , which is coupled to the arm  24  and remains in a fixed position with respect to the arm  24 . A distal portion  38  of the lamp head  26  rotates with respect to the proximal portion  36  in both a clockwise and a counter-clockwise direction. The rotation of the distal portion  38  may be limited in each of the clockwise and counter-clockwise directions by stops within the distal portion  38 . Rotation of the distal portion  38  causes relative motion of components within the lamp head  26  to adjust the spot size of the light emitted from an exit aperture  40  of the lamp head  26 . 
         [0029]    As seen in more detail in  FIG. 4 , a cylinder  42  with slots  44   a,    44   b,    44   c  is fixed to a housing  46  within the proximal portion  36  of the lamp head  26 . A lens  48  is located within the cylinder  42  near the housing  46 . Protrusions  50   a,    50   b,    50   c  extending from an edge of the lens  48  are aligned with the slots  44   a,    44   b,    44   c  within the cylinder  42  allowing the lens to move along an axis normal to the lens  48 . A second lens  52  is also located within the cylinder  42  and distally from the lens  48 . Protrusions  54   a,    54   b,    54   c  extending from an edge of the lens  54  are also aligned with the slots  44   a,    44   b,    44   c  within the cylinder  42  allowing the lens to move along an axis normal to the lens  52 . Components  56   a,    56   b,    56   c,  illustrated in an exploded view in  FIG. 4 , contain slots  58   a,    58   b,    58   c  in which the protrusions  50   a,    50   b,    50   c  of lens  48  are also located. Components  56   a,    56   b,    56   c  are coupled with the distal portion  38  of the lamp head  26 . As the distal portion  38  of the lamp head  26  are rotated, components  56   a,    56   b,    56   c  and their associated slots  58   a,    58   b,    58   c  and  60   a,    60   b,    60   c  are also rotated. 
         [0030]    When assembled, slots  58   a,    58   b,    58   c  intersect slots  44   a,    44   b,    44   c  respectively. Similarly, slots  60   a,    60   b,    60   c  also intersect slots  44   a,    44   b,    44   c.  An example of theses intersections may be seen in the detailed view in  FIG. 4A . Intersection  62  occurs where slot  58   a  of component  56   a  crosses slot  44   a  of cylinder  42 . Protrusion  50   a  of lens  48  is positioned at intersection  62 . The other protrusions  50   b,    50   c  of lens  48  are positioned similarly in similar intersections (not shown). Additionally, intersection  64  occurs where slot  60   a  of component  56   a  crosses slot  44   a  of cylinder  42 . Protrusion  54   a  of lens  52  is positioned at intersection  64 . The other protrusions  54   b,    54   c  of lens  52  are positioned similarly in similar intersections (not shown). As the components  56   a,    56   b,    56   c  are rotated, the intersection point moves along the slots  44   a,    44   b,    44   c  thus moving the lenses  48 ,  52  relative to one another. 
         [0031]      FIG. 5  shows a cross section of the lamp head  26  with the lenses  48 ,  52  in a first position at one of the extremes of the light. As can be seen in the cross section, DC power is delivered through arm  24  connected to the proximal portion  36  of the lamp head  26 . Circuit board  66  receives the DC power (not shown) as well as control signals from the control area  32 . Circuit board  66  also contains the drive controls for LED  70 , the source of the light for the examination light  20 . Circuit board  66  is connected to circuit board  68 , which contains the LED  70  and a current sense resistor providing feedback to circuit board  66 . Other embodiments may contain alternate configurations of the circuit boards with single or multiple boards being used. In multiple board embodiments, components may be distributed in many configurations. The drive controls on circuit board  68  drive LED  70  according to a desired output level. Light emitted from LED  70  is collected in mixing element  72 . Light exits mixing element  72  at an exit face  74  and is directed toward both lenses  48 ,  52 . Light is then magnified by lenses  48 ,  52  to generate the desired spot size. 
         [0032]      FIG. 6  illustrates the magnification of the light with the lenses  48 ,  52  in the position shown in  FIG. 5 . For clarity, only the optical elements are shown in  FIG. 6 . As can be seen in the figure, light rays  76  emitted from LED  70  are collected in mixing element  72  and directed from the exit face  74  first to lens  48 . Light rays  76  are first magnified by lens  48  and while being directed to lens  52 . Lens  52  further magnifies the light rays  76  resulting in a spot  78 . In this configuration, spot  78  is at its maximum size (42 times magnification). 
         [0033]    Specifically, and with reference to both  FIGS. 6 and 7 , light from the LED  70  (a Luxeon K2 in some embodiments, though other LEDs may also be used), which is encapsulated in a nearly hemispherical epoxy lens, is sent to an output face via refraction at a positive optical surface, followed by Total Internal Reflection (“TIR”) at a parabolic initial phase  80  of the mixing element  72  and thereby via additional TIR along the cylindrical final stage  82  of the mixing element. Some of the emission from the LED  70  also proceeds directly without TIR to the output face  74 , being affected only by the initial refractive surface. 
         [0034]    The exit face  74  is then re-imaged via a 3:1 zoom lens (lenses  48 ,  52 ) to a constant final position. The zoom lens operates over a magnification range of approximately 14× to 42×. The zoom lens comprises the two positive acrylic optical elements, lens  48  and lens  52 . A typical prescription of the zoom lens is attached in the appendix at the end of this disclosure. 
         [0035]      FIG. 8  illustrates a cross section of the lamp head  26  with lenses  48 ,  52  at the opposite extremes. In this configuration, an as additionally seen in the simplified view in  FIG. 9 , light rays  76  from LED  70  are sent to the parabolic initial phase  80  of the mixing element  72  and thereby via additional TIR along the cylindrical final stage  82  of the mixing element. Light rays  76  then first magnified by lens  48  and while being directed to lens  52 . Lens  52  further magnifies the light rays  76  resulting in a spot  78 . In this configuration, spot  78  is at its minimum size (14 times magnification). 
         [0036]    As the health care provider rotates the distal portion  38  of the lamp head  26  between the extremes illustrated in  FIGS. 5 ,  6 ,  8  and  9 , the lenses  48 ,  52  making up the zoom lens move towards or away from one another, thus adjusting the spot size  78  of the examination light  20 . In some embodiments, masking elements may also be used with the optics to assist in controlling the spot size. 
         [0037]    At a given distance from the exit aperture  40 , and with a fixed light (i.e. LED  70 ) output, as the target spot size  78  is increased, the light density will generally decrease. Similarly, if the spot size  78  is decreased, the light density will generally increase. Therefore, embodiments of the invention include a controller that adjusts the brightness of the light  20  to maintain a constant light density as the spot size  78  of the light  20  is changed. 
         [0038]    If the spot size  78  is known, the output from LED  70  could be increased or decreased appropriately to maintain a constant light density in the spot  78 . The spot size is proportional to lens travel. Therefore, if the position of the lens is known, the spot size is known. This position can be used by a controller  84  to adjust the drive current of the LED, which in turn adjusts the light density. 
         [0039]    The size of the spot is πr 2 . Therefore, as the spot radius (i.e. r) is increased, the light density decreases as a squared function, since the same amount of light is spread over a larger area dictated by r 2 . If the desired light intensity is achieved with an LED drive current I min , at the smallest spot size, r min , then a constant intensity may be achieved over any spot size (r) by setting the LED drive current (I) to: 
         [0000]    
       
         
           
             
               
                 
                   I 
                   = 
                   
                     
                       I 
                       min 
                     
                      
                     
                       ( 
                       
                         
                           r 
                           2 
                         
                         
                           r 
                           min 
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0040]    Referring now to the block diagram in  FIG. 10 , the position of the lens is determined using a magnetic position sensor  86  mounted in a fixed position on circuit board  66  in the proximal portion  36  of the lamp head  26 . A neodymium magnet  88  (or other permanent magnet) is mounted on the rotatable distal portion  38  of the lamp head  26 . As the distal portion  38  is rotated, an angle  90  between the magnet  88  and the centerline of the sensor  86  is changed. The change may be reflected in dual outputs  92 ,  94  of the sensor  86 . The outputs  92 ,  94  of the sensor  86  may be conditioned with instrumentation amplifiers  96 ,  98  and fed into two channels of the controller&#39;s  84  ND converters  100 ,  102 . 
         [0041]    Samples from the ND converters  100 ,  102  may be filtered with a single-pole, low-pass filter  104 ,  106 . In some embodiments the A/D converters  100 ,  102  and low pass filters  104 ,  106  may be integral with the controller  84 . In other embodiments, one or more of the ND converters  100 ,  102  or low pass filters  104 ,  106  may be separate from but in electrical communication with the controller  84 . The filtered measurements may then be fed into a linear interpolation routine  108  that uses lookup tables to approximate non-linear functions. One A/D channel  100  may be used to select the appropriate lookup table  110 , while the other channel  102  may be fed as the input (x-axis)  112  of the interpolation routine. In other embodiments, other methods of determining solutions to the non-linear functions may be used. An output of the interpolation routine  108  is a “boost” factor. The boost factor multiplies the nominal drive current (the current I min  at the smallest spot size, r min ). 
         [0042]    In some embodiments, the magnetic sensor may be temperature sensitive. This temperature sensitivity may also be dependent on the angle of the magnetic field. Therefore, one of the position A/D channels  100 ,  102  may be fed into another interpolation routine  114  that may also use a lookup table, with an output of this routine being the temperature sensitivity. A temperature of the circuit board  66  may be measured with a third A/D channel (not shown) and an internal temperature sensor  116 , either inside the controller  84  or in other embodiments the temperature sensor may be located on the circuit board  66 . The table sensitivity may be multiplied by the measured temperature and may be used to compensate the boost factor. 
         [0043]    The raw boost factor from the position routine  108  may then be multiplied by the temperature error factor  118 , and the nominal current I min  may then multiplied by the corrected boost factor resulting in a final drive current, I. This final current is controlled via a duty cycle, 0-100%. The duty cycle is used to set a timer counter register  120  in the controller  84  to output a PWM driver to an LED controller  122 . The LED controller  122  may be a constant current device, which is configured to set the maximum current with 100% duty cycle. Therefore, any duty cycle less than 100% proportionally reduces the drive current to the LED  70 , and thus adjusts the intensity of the light  76  emitted from the LED  70 , and thus may be used to keep the light density of the spot approximately constant. 
         [0044]    While the present invention has been illustrated by a description of one or more embodiments thereof and while these embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features shown and discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept. 
         [0000]    
       
         
               
             
               
               
             
               
             
               
               
               
               
               
               
             
               
             
               
               
             
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                 APPENDIX 
               
               
                   
               
               
                 Typical Prescription of the Zoom Lens 
               
               
                   
               
             
             
               
                 Zoom 
               
               
                   
               
             
          
           
               
                   
                 Cycle Number = 0, Phi Value = 0.00E+00 
               
               
                   
                   
               
             
          
           
               
                 Lens Data 
               
             
          
           
               
                   
                   
                   
                   
                   
                 Clear Aperture 
               
               
                 Surf No. 
                 Type 
                 Radius 
                 Thickness 
                 Glass 
                 Diameter 
               
               
                   
               
               
                 1 
                   
                 ∞ 
                 −1000.00000 
                   
                 8.00 
               
               
                 2 
                   
                 Aperture stop 
                 1000.00000 
                   
                 700.00 
               
               
                 3 
                   
                 ∞ 
                 Space 1 
                   
                 8.00 
               
               
                 4 
                 ac 
                 24.0000 
                 3.96000 
                 ACRYLIC 
                 10.50 
               
               
                 5 
                   
                 −10.0000 
                 Space 2 
                   
                 10.50 
               
               
                 6 
                 ac 
                 135.0000 
                 5.60000 
                 ACRYLIC 
                 19.70 
               
               
                 7 
                 ac 
                 −15.4000 
                 413.00000 
                   
                 19.70 
               
               
                 8 
                   
                 ∞ 
                 Image distance 
                   
                 400.00 
               
               
                   
               
             
          
           
               
                 Symbol Description 
               
               
                   
               
             
          
           
               
                   
                 a—Polynomial asphere 
               
               
                   
                 c—Conic section 
               
               
                   
                   
               
             
          
           
               
                 Even Polynomial Aspheres and Conic Constants 
               
             
          
           
               
                 Surf. No. 
                 k 
                 D 
                 E 
                 F 
                 G 
                 H 
               
               
                   
               
               
                 4 
                 −5.0000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
               
               
                 6 
                  1.2000E+02 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
               
               
                 7 
                 −1.3000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
                 0.000000E+00 
               
               
                   
               
             
          
           
               
                 Variable Spaces 
               
             
          
           
               
                 Zoom Pos. 
                 Space 1 T(3) 
                 Space 2 T(5) 
                 Image Distance 
                 Focal Shift 
               
               
                   
               
               
                 1 
                 0.500 
                 24.500 
                 0.231 
                 142.000 
               
               
                 2 
                 6.200 
                 0.500 
                 18.676 
                 547.000