Abstract:
A lens, suitable for automotive applications, for use with a light source is provided. The lens has a main body defining a cross sectional shape with a curved side and a straight side. The main body is formed by rotating the cross sectional shape about an axis of revolution located outside the main body. The axis of revolution is parallel to the straight side of the cross section and passes through a focal point defined by the curved side.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to lenses for use with light sources. More specifically, the invention relates to a light assembly having a lens and a light source, particularly such assemblies that may be utilized in automotive applications. 
         [0003]    2. Description of Related Art 
         [0004]    Light-emitting diode (LED) lamps are increasingly finding applications in the automotive industry. Initially used as high-mounted stop lamps, LED applications today include virtually all types of signal lamps, such as turn, stop, park, and daytime running lights (DRL), as well as low/high beam headlamps and fog lamps. Commonly used optic elements for these applications include stand-alone reflectors, reflectors with spreading lens optics, projector lamps with horizontally positioned reflective shields together with standard condenser lenses, and directly projected LED dies using standard or free form condenser lenses. Recently, compound parabolic concentrator lenses (CPCs) and near field cone optic lenses (NFLs) have also been developed for use in headlamps and fog lamps. 
         [0005]    For many exterior automotive lighting functions, it is desired that the beam pattern be wider in the horizontal direction than in the vertical direction. For forward lighting applications, governmental and consumer standards dictate tight constraints on the vertical beam pattern. Collimating lenses, such as standard or free form condenser lenses, have been used to control the vertical beam pattern. However, such lenses also have the effect of collimating light rays in the horizontal direction, which is generally undesirable. Horizontal beam spreading has been accomplished in the above-mentioned lenses through the use of a reflector or other optical element placed between the light source and the lens. 
         [0006]    Styling is another consideration in designing a light assembly. Unfortunately, styling is commonly sacrificed to achieve the desired functionality in collimating lenses. One reason for this is that condenser lenses often appear similar, even when the size and shape (circular or rectangular) are varied. 
         [0007]    In view of the above, it is apparent that there exists a need for a lens that collimates light rays in a vertical direction without collimating the light rays in a horizontal direction. Furthermore, there exists a need for a lens having this type of function while still allowing for styling variations. 
       SUMMARY 
       [0008]    In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a lens for use with a light source that is configured to collimate light rays in a single direction, while refraining from collimating rays in other directions. The lens comprises a main body having an axis of revolution located outside the main body. In cross-section, the main body has a curved side and a straight side. The curved side has a focal point through which the axis of revolution of the main body passes. The axis of revolution is also parallel to the straight side of the cross-section. 
         [0009]    Further objects, features, and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  is a perspective view of a known standard condenser lens; 
           [0011]      FIG. 1B  is a cross-sectional view of the standard condenser lens of  FIG. 1A , having an axis of revolution passing therethrough; 
           [0012]      FIG. 1C  is a perspective view of the standard condenser lens of  FIGS. 1A and 1B , having light rays being directed therethrough; 
           [0013]      FIG. 1D  is a schematic side view of the standard condenser lens of  FIGS. 1A-1C , showing light rays directed therethrough; 
           [0014]      FIG. 1E  is a schematic plan view of the standard condenser lens of  FIGS. 1A-1D , showing light rays directed therethrough; 
           [0015]      FIG. 2  is a schematic side view of a known free form condenser lens, illustrating light rays being directed therethrough; 
           [0016]      FIG. 3A  is a cross-sectional view of a lens embodying the principles of the present invention, having an axis of revolution located outside of the lens; 
           [0017]      FIG. 3B  is a perspective view of the lens of  FIG. 3A ; 
           [0018]      FIG. 3C  is a rear view of the lens of  FIGS. 3A and 3B ; 
           [0019]      FIG. 3D  is a schematic plan view of a cross section of the lens of  FIGS. 3A-3C , showing light rays being directed therethrough; 
           [0020]      FIG. 3E  is a schematic side view of a cross section of the lens of  FIGS. 3A-3D , showing light rays being directed therethrough; 
           [0021]      FIG. 4  is a schematic plan view of another lens embodying the principles of the present invention; and 
           [0022]      FIG. 5  is a perspective view of yet another lens embodying the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The present invention provides a lens having a unique shape that collimates light rays in one direction, while maintaining the original spread of the light rays along another direction. This invention will have utility in vehicle headlamp lenses, where it is desirable to vertically collimate light rays while generally allowing the horizontal spreading of the light rays. It is contemplated that the present invention will also have utility in many other applications, without falling beyond the spirit and scope of the present invention. 
         [0024]    Referring now to  FIGS. 1A-1E , a known lens  10  is illustrated therein. The lens  10  is a standard condenser lens as is known in the art. The standard condenser lens  10  has a curved light emitting face or side  12  that is disposed opposite of a flat light receiving face or side  14 . The lens  10  is preferably a solid body  16  in its cross section and is preferably formed of optical-grade plastic or glass. As seen in  FIG. 1B , the lens  10  is symmetrical about the axis of revolution R. 
         [0025]    When a light source  18  is placed at the focal point F of the lens  10 , the lens  10  collimates or nearly collimates all of the light rays  20  emanating from the light source  18 . Because the lens  10  is symmetrical about the axis of revolution R, the lens  10  collimates light rays  20  both vertically and horizontally. In fact, the lens  10  collimates light rays  20  through all 360 degrees of its cross section, such that the light rays  20  are emitted from the lens in a circular pattern, substantially collimated in each plane extending in the X-direction. 
         [0026]    By way of illustration and with reference to  FIG. 1D , a schematic side view of the lens  10  is shown, wherein the lens  10  collimates light rays  20  in a vertical plane. In other words, the light rays  20  are refracted by the curved and flat sides  12 ,  14  of the lens  10 , and the light rays  20  are emitted substantially parallel to the X-axis such that the light rays  20  are not spread in the Z-direction. With reference to  FIG. 1E , a schematic plan view of the lens  10  is shown, wherein the lens  10  is shown collimating the light rays  20  in a horizontal plane. As such, the light rays  20  are refracted by the curved side  12  of the lens  10 , and the light rays  20  are emitted substantially parallel to the X-axis such that the light rays  20  are not spread in the Y-direction. 
         [0027]    Referring now to  FIG. 2 , a schematic side view of a free form condenser lens is illustrated at  30 . The free form condenser lens  30  is similar to the standard condenser lens  10 , but is asymmetric and is constructed by numerical technique. As seen in the figure, the free form condenser lens  30  generally has a cross section similar to that of a standard condenser lens  10 , having a curved side  32  disposed opposite to a flat side  34 . However, the apex  35  of the curved side  32  is vertically lower than it would be in a standard condenser lens  10 . This allows the light rays  40  to be collimated in a vertical plane, but at a lower vertical height than with the standard condenser lens  10 . Although the free form condenser lens  30  may slightly spread the light rays  40  vertically or horizontally, it still substantially collimates the light rays  40  in both of these directions. 
         [0028]    Referring now to  FIGS. 3A-3C , a lens embodying the principles of the present invention is illustrated therein and designated at  50 . The lens  50  has a body  56  whose cross section defines a curved light emitting face or side  52  disposed opposite of a light receiving face or side  54 . In the present embodiment, the vertical cross section of the body  56  of the lens  50  is substantially the same as the vertical cross section of the standard condenser lens  10 , namely it is of a plano-convex-shape. It should be noted, however, that the vertical cross section of the body  56  could have other shapes, such as one similar to that of the free form condenser lens  30  previously discussed, or any other suitable shape, without falling beyond the spirit and scope of the present invention. As further discussed below, the horizontal cross section of the body  56  differs from the noted lenses. In particular, the body  56  exhibits a convex-concave shape when viewed in horizontal section. 
         [0029]    The curved side  52  of the cross section  56  has a focal point F outside of the lens  50 , and an axis of revolution R of the lens  50  extends through the focal point F. The axis of revolution R is also substantially parallel to a straight line  58  defined by the light receiving side  54  of the lens  50  when viewed in vertical section. To form the lens  50 , the vertical cross section of the body  56  is rotated around the axis of revolution R so as to form a partial toroidal shape. Because the straight line  58  is rotated around the axis of revolution R, the light receiving face  54  has a concave shape, as best seen in  FIG. 3D , that is a portion of a cylinder. As noted above, the light-emitting face  52  is convex in shape. 
         [0030]    This partial toroidal shape of the lens  50  is configured to collimate light rays  62  in a vertical plane, while maintaining the original spread of the light rays  62  in a horizontal plane. For example, with reference to  FIG. 3D , a schematic plan view of the lens  50  is illustrated. A light source  64  located at the focal point F emits light rays  62 , which are directed through the lens  50 . In a horizontal plane (the Y-direction), the lens  50  does not collimate the light rays  62 . Rather, the lens  50  directs the light rays  62  through the lens  50  along substantially the same paths as their original paths, maintaining a horizontal spread of the light rays  62 . 
         [0031]    The horizontal beam width from the light source  64  is controlled by the angular extent of the lens  50 , which is the angle of revolution of the lens  50  about the axis of revolution R and is preferably between about 30 and 180 degrees, depending on the desired horizontal spread of light rays  62 . It is contemplated that the lens  50  could have other angles of revolution, from greater than 0 up to 360 degrees, without falling beyond the spirit and scope of the present invention. The angle of revolution actually used will depend on the particular application, and possibly other design criteria. 
         [0032]    With reference to  FIG. 3E , a schematic side view of the lens  50  is illustrated. As seen therein, the light rays  62  emanating from the light source  64  are collimated in a vertical plane by virtue of the curved side  52  of the body  56  of the lens  50 . The light rays  62  are collimated in the vertical plane, the Z-direction, in substantially the same way as light rays  20 ,  40  are collimated by the standard and free form condenser lenses  10 ,  30  previously discussed. 
         [0033]    The unique shape of the toroidal lens  50  allows light rays  62  to be collimated in a plane extending through the axis of rotation R, while substantially remaining in their original direction in a plane perpendicular to that axis. It should be understood that the collimating direction need not be the vertical direction from ground as it will be appreciated that the lens  50  can be oriented in various positions relative to ground and that a particular application may require the spread to be in a plane that is not horizontal, but rather in another plane. 
         [0034]    In some applications, it is desirable to spread the light rays  162  emanating from the light source  164  beyond the direction of their original paths. With reference to the schematic plan view of  FIG. 4 , a lens  150  is provided that achieves such a spreading of the rays  162 . The lens  150  of  FIG. 4  is identical to that seen in  FIGS. 3A-3E  except for the light collecting face  54 . In the embodiment of  FIG. 4 , the light collecting face  154  further comprises a plurality of surface irregularities in the form of adjacent concave features, or flute optics  166 . It is also contemplated that the surface irregularities could have a variety of other shapes without falling beyond the spirit and scope of the present invention. For example, the surface irregularities could take the form of pillows, prisms, or other surface optics. Furthermore,  FIG. 4  shows flute optics  166  being located on the light-collecting face  154  of the lens  150 , but it is also contemplated that surface irregularities or optics could be located on a light-emitting face  152  of the lens  150 . The flute optics  166  of this embodiment spread the light rays  162  in a horizontal direction, or Y-direction; however, the light rays  162  will remain collimated or nearly collimated in the vertical direction, or Z-direction. As such, the flute optics  166  do not merely maintain the horizontal spread of the light rays  162 . Rather, the flute optics  166  are configured to refract the light rays  162  through the lens  150 , resulting in the light rays  162  deviating from their original directions, with some of the light rays  162  deviating farther outwardly in a horizontal plane or direction. 
         [0035]    With reference to  FIG. 5 , a lens  250  having substantially the same construction as the lens  50  of  FIGS. 3A-3E  is illustrated therein. In this embodiment, the lens  250  has a light-collecting face  254  disposed opposite to a light-emitting face  252 . The lens  250  has an integrated collimating lens  270  to increase the beam intensity at the center of the beam. In this embodiment, the integrated collimating lens  270  has a convex curved shape, substantially similar to that of a standard condenser lens  10 . However, it is contemplated that the integrated collimating lens  270  can have other shapes, such as that of a free form condenser lens  30 . Furthermore, the integrated collimating lens  270  could have surface optics on its light receiving and/or emitting surfaces. 
         [0036]    The lenses  50 ,  150 ,  250  of the present invention are preferably formed of polymethyl methacrylate (PMMA), commonly known as acrylic, or of polycarbonate (PC), although any suitable optical-grade plastic or glass could be used. The lenses  50 ,  150 ,  250  are also preferably used with an LED light source, although it is contemplated that any suitable light source could be used, such as a light bulb. 
         [0037]    As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation, and change, without departing from the spirit of this invention, as defined in the following claims.