Light emitting optical systems and assemblies and systems incorporating the same

Improved light emitting optics systems are provided for obtaining desired illumination patterns. Illumination assemblies and systems are provided that incorporate improved light emitting optics systems.

BACKGROUND

Many new illumination technologies are becoming commercially available, such as, high intensity discharge lighting, white light emitting diode lighting, halogen, bi-zenon and the like. The present invention provides improved light emitting optics systems for obtaining desired illumination patterns. Illumination assemblies and systems are also provided that incorporate improved light emitting optics systems.

DETAIL DESCRIPTION

With the increasing efficiencies of light emitting diodes, it has become desirable to utilize them for headlamp lighting for automotive vehicles. The examples in this specification will focus primarily on the headlamp application. It should, however, be recognized that many of the features of this specification are applicable to other lighting systems and it is not intended that this invention be limited to headlamp applications. Detailed descriptions of automatic vehicle exterior light control systems that may incorporate such headlights are contained in commonly assigned U.S. Pat. Nos. 5,837,994, 5,990,469, 6,008,486, 6,130,448, 6,130,421, 6,049,171, 6,465,963, 6,403,942, 6,587,573, 6,611,610, 6,621,616, 6,631,316 and U.S. patent application Ser. Nos. 10/208,142, 09/799,310, 60/404,879, 60/394,583, 10/235,476, 10/783,431, 10/777,468 and 09/800,460; the disclosures of which are incorporated herein in their entireties by reference. To utilize the LEDs effectively, there are a number of challenges to be met by the optical system which projects light of a desired color in the desired pattern generally forward of the vehicle. Many current proposals appear to be based on utilization of LEDs which emit blue or violet light and which have fluorescent materials which convert this energy into white light. Suitable individual illuminators and illumination assemblies that may be used with the present invention are disclosed in commonly assigned U.S. Pat. Nos. 5,803,579, 6,335,548, 6,441,943, 6,521,916 and 6,523,976, as well as, commonly assigned U.S. patent application Ser. Nos. 09/153,654, 09/835,238, 09/723,675, 10/078,906 and 10/230,804, the disclosures of which are incorporated in their entireties herein by reference. There are two general drawbacks to use of the blue or violet LEDs with a fluorescent coating. First, the cost of the LEDs per lumen emitted is generally higher than that of competing systems which mix light from LEDs of several different colors, for example, red, blue, and green and the overall efficiencies of such systems are typically somewhat lower. Secondly, the color temperature balance of many available LED lighting systems which utilize fluorescent material is high, i.e. very strong at the blue end of the spectrum and relatively weak at the red end of the spectrum. Such light is more annoying to other drivers than that from a more reddish or lower color temperature light source. There is more flexibility to optimize the effective color temperature of the light source when mixing light from LEDs of several colors. With such systems, the challenge is to properly mix the light of various colors from the individual LEDs to produce white light and to project it in the desired pattern of illumination. A particularly difficult requirement for any LED headlamp lighting system is to achieve a satisfactorily controlled and satisfactorily sharp transition between the upper extent of the low beam illumination pattern needed to illuminate the road in front of the vehicle and the much more dimly illuminated area just above this area of bright illumination needed to avoid subjecting drivers of oncoming and leading vehicles to blinding or undue annoyance glare.

The foregoing discussion is not intended to exclude LEDs which use fluorescent materials or systems which use combinations of LEDs having fluorescent materials with LEDs which do not have fluorescent materials; but, rather, to point out that the preferred structure of the present invention provides a method to mix the colors from LEDs of differing colors irrespective of whether they are of a fluorescent or non-fluorescent type.

One way to mix the light is to project substantially similar patterns of illumination of the component colors so that they overlay one another to produce light of the satisfactory color. For such systems, it is desirable to provide sources, including lensing, for LEDs of the various colors that are small enough so that they may be close to one another so that they tend to appear as a single white light source as opposed to appearing as an array of light sources of differing colors to oncoming drivers and others who may view the lights directly. A second reason to keep the sources small is that a relatively large number of LEDs are required to generate the required light intensity. When numerous individual lenses are used for individual or small subgroups of the LEDs, each lens must be accordingly small to limit the total headlamp light emitting area to a reasonable size. Small lenses exacerbate the problem of maintaining the sharp cutoff of the brightly illuminated area of the upper extent of the low beam pattern while, at the same time, maintaining reasonable efficiency in the proportion of the light from the LEDs which is projected into the headlamp lighting pattern.

To meet the diverse requirements of the optical system, it is desirable to share a common lens with a relatively large percentage or even all of the LEDs in a headlamp unit. It is also desirable to partition the optical components which serve to concentrate or establish the lighting pattern in the elevational direction with its critical requirements from optical components of the system which concentrate the light in the horizontal direction so larger lens dimensions may be used to meet the pattern requirements in the vertical or elevational direction and relatively smaller lens dimensions may be used to meet the less demanding requirements to pattern the beam in the side to side or horizontal direction thereby reducing the overall size of the headlamp system. In the preferred system, the vertical concentration component accepts partially overlapping patterns of illumination from multiple horizontal concentrator assemblies, each with their associated LEDs providing a more compact overall structure. Partitioning of the lens system with one component to perform the concentration in the horizontal direction and another component to perform the concentration in the vertical direction may also be used to advantage to separately characterize the patterns of illumination in the horizontal and the vertical directions. With increasing concern for fuel economy, it is further desirable to maintain a low profile for the front of the vehicle, so it is more important to keep the height of the headlamp very small than to necessarily keep a correspondingly small width. It is additionally desirable to share the lens system for all or for major components of the low beam and high beam lighting functions.

As will be described in detail, a preferred embodiment of the present invention utilizes an optical system which uses a first lens system to concentrate the light in the horizontal or side to side direction. This will be referred to as the horizontal concentrator. A second lens or lens system is used to concentrate the light in the vertical or elevational direction. This will be referred to as the vertical concentrator. The preferred system further uses one or more lens elements which are common to all or a large group of LEDs as the vertical concentrator to concentrate or pattern the light in the vertical direction. The preferred system utilizes a larger number of horizontal concentrators each with its lens or lenses and the associated group of one or more LEDs to concentrate light in the horizontal direction. In an exemplary system, several or perhaps all of the lens element surfaces in the horizontal concentrator are joined in a single piece of plastic. In a preferred system, however, in order to minimize thermally induced movement of the lens units of the individual horizontal concentrators relative to their associated groups of LEDs and also to facilitate mold design to provide a combined reflecting and refracting lens structure, each horizontal concentrator uses a separate plastic lens part. It should be understood that materials other than plastic, such as glass or other organic materials such as polycarbonate, polymacrylate and acrylic, may be used for the optic elements and/or lens. In the preferred structure, light from the LEDs first passes through the horizontal concentrator and then through the vertical concentrator. Thus, the lens elements in the horizontal concentrator are further designed to project the light in a pattern which may be effectively focused or utilized by the succeeding lens stage which serves as the vertical concentrator.

Various features of the preferred headlamp structure which operate in concert to enable proper performance of the system are as follows. The common lens which may contain multiple elements which concentrates light in the vertical direction is generally of a cylindrical design and the collection of lenses or lens surfaces which concentrate light in a horizontal direction each utilize lens surfaces which are generally surfaces of revolution where the axis of revolution is generally centered with the line of focus or the optical center of the cylindrical lens system of the vertical concentrator. Further, the LEDs are grouped in subgroups, each of which is associated with an individual horizontal concentrator. There is often an area in the field of illumination which is difficult to pattern such as the upper extent of the brightly illuminated area of the low beam pattern. It is normally preferable to select the area of each LED array which is projected into an area which is difficult to pattern in the field of illumination and to choose it generally as the optical center of the group of LEDs. For a lamp whose use includes the low beam function, this area which is difficult to pattern is preferably chosen as the area which projects as the upper extent of the bright portion of the illumination pattern of the low beam. The lens elements of the horizontal concentrators are designed such that their focal points or optical centers fall generally on their axis of revolution, and the axis of revolution is positioned to fall generally on the line of focus or optical center of the cylindrical lens system used as the vertical concentrator. Thus, the nominal centers of the LED clusters, the focal points or optical centers of the lens elements in the horizontal concentrator, the axes of revolution of the lens elements in the horizontal concentrator, and the line of focus or the optical center of the vertical concentrator are preferably approximately co-linear with one another. As will be described, various techniques including intentional defocus and shifting, stepping, or sweeping of effective focal points may be used to characterize the lenses of the vertical or horizontal concentrators so that the desired pattern of illumination is projected. With such lenses, there is generally a preferred center position for the light source which may be referred to as the optical center. It should also be noted that the optical system of this invention is intended primarily for applications to provide illumination and as such does not need to perform imaging functions. Some of the non-imaging properties such as intentional defocus will be used to improve uniformity of the projected pattern of illumination in addition to characterizing the pattern.

FIG. 1depicts an example of the construction of the lens shape profile for the surface of revolution used for the lens elements in the horizontal concentrator. For a given index of refraction, a refracting lens which collimates light into parallel rays is best designed as an elliptical shape. For an elliptical lens100, the nominal focal point is a focus point101of the ellipse. In the following, the term refractive angle will be used to indicate the number of degrees by which a specified light ray is bent as it passes through a boundary from a first medium having a first refractive index into a second medium which has a different second refractive index. For light rays passing from a medium of higher to a medium of lower refractive index, as the angle of incidence of the light rays to the lens surface increases relative to the normal to the surface, the refractive angle is increased and internal reflections also increase until at a critical angle of incidence the internal reflection becomes total. Thus, the magnitude of the refractive angles expected from the lens must be limited to maintain relatively high overall efficiency of the lens. For lens100, the refractive angle required to bend light rays emanating from focal point101so that they are generally parallel to axis102is, for example, judged to be satisfactorily low for rays passing through lens surface104between bounding lines109and110. Losses are generally lower for smaller refractive angles, so when multiple lens surfaces are used to perform a particular optical function, it is generally preferable to design the system to approximately equalize the maximum refractive angle which is provided by each of the lens surfaces, thereby approximately equally sharing the light ray bending function among the available optical surfaces. Rays emanating from focal point101and passing through areas105and106of the lens would have to be bent by a larger refractive angle to make them parallel to axis102. Thus, to avoid the larger refractive angle and the reduced efficiency, the lens shape in areas105and106is changed from the elliptical shape and is designed to, for example, maintain a nominally constant refractive angle for rays emanating from focal point101and passing through these areas. Rays emanating from lens100through the regions between lines109and111and between lines110and112diverge modestly rather than being directed parallel to axis102but are still directed to an area where they are useful in the illumination pattern. When the focal point101is replaced by an LED or a small array of LEDs, the pattern of the projected light is enlarged generally in proportion to the dimensions of the emitting area relative to the overall lens dimensions. In lens100, for proper collimation of the light rays, the ratio of the major to the minor diameter of the ellipse is established as a function of the ratio of the refractive index of the material on the inside of the lens to the refractive index of the material on the outside of the lens. Methods to determine the ratio of the minor to the major diameter of the elliptical lens100as a function of the refractive indices of the lens and of the surrounding material to focus light from a point source into a collimated beam may be found in textbooks on optical design.

InFIG. 1a, the portion of the curve fromFIG. 1which is used to generate the optical surface of an individual horizontal concentrator is depicted with the letter “a” appended to the corresponding numbers fromFIG. 1. The curve is labeled150a. Axis102ais the major diameter of the elliptical surface on which the lens is based. Axis103ais preferably in the plane of the elliptical curve, may pass through the focal point101aand is preferably perpendicular to axis102a. For purposes of illustration, it will be assumed that axis103adoes pass through focal point101a. It will be used as the axis about which the curve from107ato108ais revolved to generate the lens surface for one of the horizontal concentrators. Ray121apasses through an elliptical portion of the lens surface104aof the curve150aand is refracted so that it becomes nearly parallel with axis102a. Ray120apasses through modified non-elliptical area105aof curve150aand is refracted toward but not fully parallel to axis102a.

InFIG. 1b, the focus101bcorresponds to focal point101inFIG. 1and to point101ainFIG. 1a. Axis103bcorresponds to axis103ainFIG. 1a. The surface150bis generated by revolving curve150aabout axis103a. The angle through which the curve is revolved should be large enough to include the active part of the lens surface which may, for example, be 130° or a little more. It is convenient in many designs to revolve the curve through approximately 180° to generate this surface. This is what is depicted. In the preferred design, the interior of the surface is filled with the material (for example, polycarbonate plastic) having a higher refractive index than the exterior of this surface (air for example).

FIG. 1cis a side view of the lens150b. A ray121cemanating from focal point101cand passing through the portion of the lens surface generated by the elliptical portion of the generating curve is refracted so that it becomes nearly parallel to the center plane of the lens. The center plane of the lens is shown in edge view as line102c. Ray120cemanating from focal point101cand passing through the portion of the lens surface generated by the non-elliptical part of the generating curve is refracted toward but not parallel to central plane102c.

FIG. 1dis a top view of the lens150b. Rays120dand121dare the top views of rays120cand121cofFIG. 1cand point101dis the end view of axis103cand of focus point101cwhich lies approximately on axis103c. Because the lens is a surface of revolution with an axis of revolution which is perpendicular to the plane of this view, the projection of the normal to any point on the lens surface will lie along a line which extends through the axis of revolution. The focal point and the axis of revolution show as a point101din this view. Thus, in this view any ray which emanates from optical center point101dand passes through the surface of lens150dwill have an angle of incidence relative to the normal to the surface which has a 0° component in this view. This indicates that the component of the refractive angle is also close to zero in this view and that in this view all rays including120dand121dappear to pass straight through the lens surface even though they may be refracted through a substantial angle in another view as is the case for the two rays120dand121dwhich are depicted. In the preferred configuration, the property of the horizontal concentrator to generally preserve the direction of propagation of rays as observed in a plane which is generally perpendicular to the line or path along which the light sources are situated is enabled by use of the surface of revolution or toroidal structure of the lens elements. The use of the surface of revolution in the preferred structure allows considerable latitude in the design properties of the generating curve which is revolved to generate the lens surface. For example, the curve may represent imaging or non-imaging optics either focused or defocused and may include reflecting or refracting surfaces either separately or in combination and may further include instances where a portion of the rays encounter zero, with one or more optical surfaces in their path from the light source through the toroidal structure to the vertical concentrator. It is preferable to place features such as the lower extent of the pattern of LEDs for the low beam which, for the preferred design, is projected as the upper extent of the brightly illuminated area of the low beam pattern close to the axis of revolution of the toroidal lens assembly. By doing this, the principles just described will be more strictly adhered to resulting in generally sharper definition of the required sharp cut off between the brightly illuminated region at the upper extent of the low beam pattern and the dimly illuminated portion just above it.

InFIG. 2, curve200is composed of curve sections or lenses201,202,203, and204each having profiles similar to that of lens150aofFIG. 1a. Further, these curve sections have respective optical centers or focal points211,212,213, and214which all lie approximately on axis205. The curve of200is rotated through an angle of, for example, 180° to generate the optical surface of a lens shown in various configurations inFIGS. 3,4,5, and6. Even thoughFIG. 2is shown primarily to represent the lens profile200, this is a convenient place to illustrate several rays221,222,223, and224which could logically apply to the actual lenses in any of theFIGS. 3 through 6. Ray221emanates from focal point211and passes through a portion of lens201. Ray222emanates from focal point212and passes through a portion of lens202. These rays are shown to illustrate that some of the rays from focal point211may pass through the concentrating lens but pass into the region normally thought to be associated with lens202associated with focal point212and likewise ray222emanates from focal point212and passes into the region normally thought to be associated with lens201. Thus, portions of the cylindrical lens to be added inFIG. 4will focus light rays from more than one of the horizontal concentrators with their associated light sources (i.e., the vertical concentrator will focus light from partially overlapping patterns of illumination). Ray223which emanates from focal point213does not pass through lens surface203but instead passes through the surface of lens204. This ray is not effectively concentrated. Some of these rays, after possible additional reflection, may be emitted from the headlamp and contribute to the low-level diffuse lighting pattern which is also needed for the overall headlamp illumination pattern. Nonetheless, attention should be given to generally minimize the percentage of rays which are not projected into useful areas of the pattern of illumination. A later example will include reflecting optics to handle some of these rays and in some configurations, extra space may be needed between sections of the horizontal concentrator to minimize the number of rays which are blocked by the lens structure of a neighboring horizontal concentrator. Ray224emanates from focal point214and passes through the elliptical portion of lens204and should contribute to the most intense portion of the illumination pattern directly forward of the vehicle. Composite curve230which may, for example, be composed of straight line231and circular segments232is provided to illustrate a possible generator for the walls of an inner cavity of the lens which is preferably filled with a transparent fluid or a compliant transparent material to surround the LEDs to serve as a buffer for expansion coefficient differences and to provide convective and/or conductive cooling for the LEDs. It is preferred that the material used to fill this cavity be of a high refractive index to increase the critical angles for light rays emanating from the LEDs and allow more of the light rays to pass out of the LED chips rather than being reflected back into the chips due to total internal reflection. In some cases, the four curve segments of which circular segment232is representative may be arcs of circles centered on their respective focal points so that they will generate spherical cavities with the groups of LEDs nominally at each of their centers. With this configuration, mismatch in the refractive index of the material around the LED with the lens material will cause minimal change in the direction of the emitted light. In other cases, alternate shapes for the curves used to generate the central cavity may be used to intentionally make this interface part of the active lens structure. In the case that the refractive indices of the lens and fill material around the LEDs are relatively well matched, the lens effect due to this interface may be weak enough to be neglected and the shape of the cavities around the LEDs may have fewer restrictions. It may be desirable in some cases to use an inner cavity which is not a surface of revolution, but it should be kept in mind that what has been noted about the advantage of making the surface of the concentrating lens a surface of revolution about the focal center in order to preserve the focusing capability of a cascaded vertical concentrator applies to lensing effects at the internal interface as well as to the external interface of the lens elements of the horizontal concentrators. In the optional straight-line segments of which line231is representative, connecting the curved segments around each of the focal points may be used to generate passages joining the cavities around the LEDs. It is preferable that the area occupied by these passages be kept generally small enough and be positioned such that the passages intersect the cavities surrounding the LEDs in areas which are outside of those for which are part of the normal active optical paths for the concentrating lenses. Passages are optional and are normally omitted at the ends of the lens structure if fluid is contained within the structure.

FIG. 3is the end view (which is perpendicular to the axis of revolution used to generate the lens surface) of a composite set of four lenses designed to be the horizontal concentrators for four relatively concentrated light sources nominally centered at each of the four focal points of the lens array. Rays305,306, and307are representative of rays emanating from one of the focal points and this illustrates the point explained in connection withFIG. 1dthat in this view (which is generally perpendicular to the axis of revolution of the lens) all of the ray traces of rays emanating from the line of focus or optical center at the center of revolution of the lens structure appear as nearly straight lines as they pass through and exit the lens array of the horizontal concentrator. Semicircle301is the outer extent of the surface of revolution of the lens structure and semicircle303is traced by the beginning and end points of each of the lens segments which make up the composite lens profile. Curves304and308depict outlines of the cavities supplied for the LEDs and the filling medium and the possible interconnecting passages between the cavities which are provided for the LEDs which are grouped at each of the focal points.

FIG. 4is an end view of an optical structure having a row of appropriately clustered LEDs402, a horizontal concentrator401, and a vertical concentrator405which is preferably a cylindrical lens which may optionally be a multi-element lens and which is preferably shared by several or all of the clusters of LEDs which each have their associated horizontal concentrating lens elements. For reasons given before, the representative rays403,404and406, which emanate from focal line402travel in paths through the horizontal concentrator401which appear as straight lines in the end view ofFIG. 4. Thus, for the ray traces of rays403,404, and406through horizontal concentrator401and vertical concentrator405, the vertical concentrator405continues to function to focus light rays emanating from the vicinity of focal line402and passing through the toroidal lens structure of the horizontal concentrator401much as if the horizontal concentrator was not there. This permits the horizontal and vertical concentrators to be cascaded with the horizontal concentrator effective to concentrate or pattern the light primarily in the horizontal direction and the vertical concentrator effective to concentrate or pattern the light primarily in the vertical direction.

InFIGS. 2 through 6, four horizontal concentrating lenses are chosen by way of example. With available LEDs, it is anticipated that many more than four groups of LEDs will be needed to supply the required amount of light. In the structure, there are many available trades as to the number and size of LEDs grouped with each of the horizontal concentrators, the size of the horizontal concentrator, and the amount of current which may be supplied to each of the LEDs. Also, there is likely to be substantial thermal mismatch between the substrate on which the LEDs are mounted and the lens structure. In the design of the mechanical structure to accommodate these mismatches in expansion coefficients, the overall size of the plastic pieces is one of the factors. This may require separation of the horizontal concentrators possibly into individual units or into smaller subgroups of units rather than to incorporate all of the units into one long plastic piece. It is conceivable, for example, that there may be as many as 24 or more horizontal concentrators in the overall headlamp structure.

FIG. 5is a wireframe view of the lens surfaces of a lens assembly500having horizontal concentrator401and vertical concentrator405. This is the assembly previously described and shown in an end view inFIG. 4. For purposes of illustration, there are four sections in the horizontal concentrator having lens surfaces503,505,507, and509with respective optical centers502,504,506, and508. In application, there would probably be more horizontal concentrators and the light sources, preferably LEDs, would be nominally centered at the optical centers502,504,506, and508. The focal points or optical centers of the individual horizontal concentrators also preferably fall on or close to the axis501. The vertical concentrator405is a cylindrical lens which is preferably common to all or to a significant subgroup of the horizontal concentrators. The vertical concentrator405preferably approximately shares a line of effective focus or optical center with the axis501which is preferably approximately the center of the surface of revolution for the lens surfaces in the horizontal concentrator and is also preferably approximately the line along which the effective focal points or optical centers of the lenses in the individual horizontal concentrators fall. The vertical concentrator405preferably extends modestly beyond the ends of the horizontal concentrator401in order to collect most of the light rays from the end units in the array of lens elements in the horizontal concentrator401. As will be described in a later example, for LED sources of differing colors each with their associated horizontal concentrator, the common axis501is preferably replaced by individual axes for each of the concentrators and associated clusters of LEDs positioning each to accommodate the effective focal length of the vertical concentrator at the characteristic color of the associated clusters of LEDs with their associated horizontal concentrator. The individual axes tuned for the associated color will tend to be close to the representative axis501but the fine tuning is an important step much as color correction is important for a camera lens.

InFIG. 6, the horizontal concentrator401similar to the horizontal concentrator401ofFIG. 5is oriented to direct light rays generally downward into a cylindrical reflecting lens which preferably has an approximately parabolic cross section and which performs a function similar to that of the vertical concentrator405ofFIG. 5. InFIG. 6, line501is the approximate axis of revolution of the horizontal concentrator, preferably the line along which the LED light sources are placed, preferably the line along which the focal points or optical centers of the horizontal concentrators lie, and also preferably the line of focus or optical center of the cylindrical parabolic reflecting surface611. In this Figure, the term cylindrical is used in the more general sense for which parallel line generators of the surface may follow a path which need not be circular as for a circular cylinder. In the case of this example, the path which the parallel generator elements follow to generate the surface is a segment of a curve which is approximately parabolic.

InFIG. 7, the outline700of a section of the horizontal concentrator is shown with lens profile709showing at the top and lens profile708showing at the bottom. Boundaries706or707may either or both be sides of an individual horizontal concentrator or may be the lines of attachment to an adjacent horizontal concentrator or may be the end of a group of attached concentrators or may be a boundary for another lens section such as a reflective portion of the lens that adjoins the section which is shown. Dotted line705indicates the outline of a cavity preferably filled with a transparent fluid or preferably compliant transparent material710in which a single LED or a cluster of LEDs is preferably placed. The material710preferably has good heat transfer characteristics and preferably has a high index of refraction. In the example, there are two LEDs720aand720bhaving power attachments to the substrate and/or to connecting wires of which704is typical. In the design, the light emitting areas of LEDs720aand720bare preferably as close to each other as possible and the optical center703of the lens is preferably nominally centered between these two LEDs. In the configuration ofFIG. 4andFIG. 5, the illumination pattern is inverted in the vertical direction by the vertical concentrator so that light from LED720ais generally directed to the lower portion of the pattern of illumination and light from LED720bis normally directed toward the upper portion of the pattern of illumination with the line between the two LEDs generally falling toward the center of the total pattern of illumination. Thus, it is preferable to illuminate LED720afor both the high and low beam modes and to illuminate LED720bfor the high beam mode only. It is preferable to choose the lower edge of LED720awhich projects into the field of illumination as the upper edge of the brightly illuminated area for the low beam pattern as the optical center of the two LEDs in the group. Depending on requirements of the design, it is not necessary that LEDs720aand720bbe the same size or even that the placement be exactly symmetrical nor are the die necessarily square.

It is generally intended that when colors from various LEDs need to be mixed, light from LEDs of a particular color (which optionally include a fluorescent material) in one of the units, such as depicted inFIG. 7, be overlaid by light of another of the required color components from one or more other horizontal concentrators which have a pattern or patterns of illumination which are substantially similar to the one projected by the horizontal concentrator inFIG. 7but which contain the LED or LEDs which emit light of other color components needed to achieve the desired color in the composite overlaid lighting pattern. Multiple groups of LEDs with their associated horizontal concentrators may project the same color in order to achieve the required intensity. For example, there may be six red, six green, and six blue concentrators projecting a total of 18 overlaid images with six projected images for each of the three component colors. As another example, the number of horizontal concentrators may differ for different colors depending on the brightness levels of the LEDs for each color and on the overall color requirements. To achieve the best color mixing, it is preferable that a set or subset of horizontal concentrators similar to the one depicted inFIG. 7having the combination of colors to produce light of the desired color project substantially overlaid similar patterns so that the color of the composite, overlaid, projected patterns of light tends to be correct and satisfactorily uniform.

Segmenting the pattern of illumination into more or less discrete areas to be covered by various subgroups of modules similar to that inFIG. 7tends to increase the size of the lenses that are required. Thus, it is desirable to fill as much of the overall pattern of illumination as practical with light from as many of the subunits similar toFIG. 7as practical. While generally following the principle above, some modification or variation in the illumination patterns of individual or sub groups of units similar to that ofFIG. 7is desirable for the following reasons. Features such as the die bonding area where electrical attachment is made to the illuminating surface of the LED or the gaps between multiple LEDs will tend to project poorly illuminated areas in the field of illumination. One way to counteract this effect is to modestly dither the positions at which anomalies in the illumination patterns appear for individual units, such as that ofFIG. 7. In so doing, adequate correlation should be maintained between the illumination patterns of the various color components in order to achieve satisfactorily uniform color in the resulting composite illumination pattern. The overall effect is to stagger areas of inadequate illumination in the overall patterns of individual or of subgroups of the lighting modules so that inadequacies of one subgroup are at least partially offset by the lighting pattern of other subgroups in the array. Other techniques including diffusion and intentional defocus particularly for the horizontal concentrator may be used to minimize these artifacts. In general, however, it is desirable to selectively apply diffusion or defocus characterizing to be greater in the horizontal direction. Diffusion or defocus needs to be generally limited in the vertical direction in order to prevent too much softening of the sharp cut off between the brightly and dimly illuminated regions in the vertical lighting profile. In general, the effects of diffusion mitigate against the ability to create a sharply defined pattern of illumination with a lens system of a given size and should accordingly be used sparingly. As will be described later, generally non-planar features such as the baffle1103with protruding forward edge1104which is depicted inFIG. 11may be added and the position of the optical center may be chosen as the forward edge1104bringing edge1104into relatively sharp focus to project a sharply defined upper edge on the low beam pattern of illumination, for example, to preserve adequate definition in the projected pattern of illumination while defocusing areas of the LED surfaces permitting areas such as gaps between adjacent LEDs to be defocused to reduce the non-uniformity in the projected field of illumination due to these features. Features including adjustment of relative sizes of the LEDs of differing colors and lens designs specific to the colors which they project may be individually characterized for the individual sections similar to that ofFIG. 7to optimize each unit for the color of the light which it is projecting. The position of each horizontal concentrator unit and its associated LEDs should be adjusted to the line of best focus for the vertical concentrator at the color projected from the LEDs in the unit. As an example, for polycarbonate, focal lengths are significantly shorter at the blue end of the spectrum than at the red.

In some headlamps systems, particularly HID headlamps, it is a normal practice to make the upper extent of the brightly illuminated portion of the low beam on the side that illuminates the side of the road higher than it is on the side which is normally projected into the lane of oncoming vehicles. The configuration which has been described so far is best adapted to provide a relatively straight line of demarcation between the brightly and dimly illuminated areas at the upper extent of the low beam pattern of illumination. InFIG. 8, some modifications are made to the optical design described inFIGS. 1 through 7in order to provide a modest side to side elevational offset in the upper extent of the brightly illuminated region of the low beam pattern of illumination while still adhering generally to the previous teachings of the patent.

InFIG. 8, the elliptical portion840aand the dashed elliptical portion840ctaken together are the general elliptical shape similar to that depicted inFIG. 1. Point821ais the focus of the ellipse and features807,811,805,809, and804generally correspond, respectively, to features107,111,105,109, and104ofFIG. 1. The view inFIG. 8includes the profile from807to815to808of the lens taken generally through its midsection in the horizontal plane. Line820represents a top front profile view of the LEDs similar to those shown as LEDs720aand720bin a front view inFIG. 7. The curve segment840bis preferably elliptical in shape and is offset from the portion840aso that its focal point falls generally at the edge of LED820has shown. As will be illustrated inFIG. 9, a first portion of the lens is a surface of revolution and its associated axis of revolution and focal point821a. It is generated by revolving the curve850awhich extends from807to815about an axis through its focal point821a. The focal point and axis of rotation are offset modestly in the vertical direction from the second portion of the lens which is generated by revolving the curve850bwhich extends from815to808about an axis through its focal point821b. Since this is a top view, the point821bwhich appears below point821ainFIG. 8appears to the right of point821aas viewed by the driver of a car in a normal automotive headlamp application with configurations as depicted inFIGS. 4 and 5. In this orientation in the vehicle for a normal headlamp application, the portion of the lens associated with focal point821bwill generally direct light from LEDs820to the driver's right side of center and a cylindrical vertical concentrating lens as depicted inFIG. 4,5, or6will generally preserve this directional orientation in the horizontal direction.

InFIG. 9, a profile900of a lens uses the profiles described in connection withFIG. 8to generate the lens surfaces. The lens constructed according to the description inFIG. 9may, for example, be applied in a general configuration as depicted inFIG. 4or5. The lens profile900is similar to the profile ofFIG. 7but has modifications to modestly elevate the upper extent of the profile of illumination generally to the right of center as viewed by the driver of a vehicle in which a headlamp of this design is employed. Portion950bof the lens has focal point921bgenerally located on its axis of revolution907bwhich is positioned modestly above the focal line907of the vertical concentrator and also positioned generally to the left edge of the array of LEDs920aand920bas viewed inFIG. 9. These sides would be reversed for countries where traffic preferentially uses the left lane. The modest elevational offset of axis of revolution907bupward from focal line907modestly elevates the upper edge of the pattern of illumination which is projected from the lower edge of LED920awhich is illuminated without illuminating LED920bduring low beam operation. As withFIG. 7, both LEDs920aand920bare illuminated during high beam operation. As indicated in the discussion ofFIG. 8, offset of the focal point921bto the left edge of the array of LEDs results in projecting a pattern of illumination from section950bof the lens which falls generally to the right of center as viewed by the driver of the vehicle in which the headlamp is employed.

Portion950aof the lens has focal point921agenerally located on axis of revolution907awhich is positioned modestly below the focal line or line of the focal line907of the vertical concentrator and also positioned generally on the vertical centerline of the array of LEDs920aand920b. The modest elevational offset of axis of revolution907bdownward from line focus907modestly lowers the upper edge of the pattern of illumination which is projected from the lower edge of LED920a. LED920ais illuminated without illuminating LED920bduring low beam operation. By slightly elevating axis of revolution907bfrom focal line907and by slightly lowering axis of revolution907afrom focal line907, the three axes are kept close together thereby minimizing aberrations in the optical system which degrade the sharp transition between the brightly and dimly illuminated portions of the pattern of illumination for the headlamp in the low beam mode. As inFIG. 7, a material910which preferably has a relatively high index of refraction and good heat transfer properties is used to fill the cavity in which the LEDs920aand920bare placed.

Color compensation gave a reason to individually adjust the axes of revolution and placement of focal centers of the clusters of LEDs for different horizontal concentrating units.FIGS. 8 and 9illustrate the use of multiple axis of revolution for various portions of the lens structure within an individual horizontal concentrator lens unit in order to refine the pattern of illumination projected by the unit. This technique is applicable to other features in other embodiments of this invention. For example, as an option inFIG. 26, the curves2605and2607used to generate a reflecting surface and an exit window for the reflected light might be revolved about an axis preferably close to but optionally distinct from centerline2607about which other portions of the profile are revolved to generate the lens surface. And such adjustment may be done to adjust the resulting pattern of illumination. In this particular case, the position and/or shape of the bright center spot into which the reflecting surfaces generated by curve2605preferably project a portion of their light might be adjusted. The similar segment2625might be rotated about the same or yet another axis than curve2605. Additionally, the generally toroidal surfaces need not be pure surfaces of revolution and the generally cylindrical surfaces need not be purely cylindrical. Such modifications might be viewed in somewhat the same way that aspheric surfaces are used in lens systems whose elements are predominantly spherical in order to meet certain requirements more readily than if the system is limited to spherical elements only. As the general similarity of the aspheric elements to their spherical cousins is usually retained, the same may be true of nearly or approximately toroidal or cylindrical surfaces used as elements within this invention.

In the modifications of areas105and106in the lens profile ofFIG. 1, the shifting of optical centers and the modest offsets of axes of rotation are a few techniques which may be employed to characterize the illumination pattern in the lens assembly. In the example ofFIG. 1, areas105and106of the curve were modified to characterize the pattern of illumination in the horizontal direction and to enhance the performance of the lens system. InFIGS. 8 and 9, offset in effective focal points for portions of the lens resulted in further characterization of the pattern and further offsets in the axes of rotation of portions of the lens elements were used to introduce modest changes in the vertical illumination pattern as a function of the position in the horizontal field of view. Intentional misfocus is another technique which may be used to characterize the illumination pattern projected by the concentrators.

In each of these cases, the separation of the vertical concentration and the horizontal concentration of the light rays into two at least partially separate cascaded lens systems served as the basis to allow separate characterization of the pattern of illumination in the vertical and horizontal directions. The directions for which the respective concentrators are operative to perform the light concentrating functions do not need to be horizontal and vertical for all applications or even for all headlamp lighting applications. It is however, preferred that the optical system include two concentrators for which the direction in which the first concentrator is operative to achieve a concentrating effect is approximately orthogonal to the direction in which a second concentrator is operative to achieve a further concentrating effect on light which has passed through the first concentrator. More generally, it is preferred that the optical system includes two cascaded light concentrating stages where the second stage is operative to concentrate light rays in a direction which is different from the direction that the first concentrator is operative to concentrate light rays.

FIG. 10illustrates an array having four horizontal concentrators1001,1002,1003, and1004with their associated arrays of LEDs. As noted earlier, in many embodiments, a full headlamp assembly will have substantially more groups of LEDs and associated horizontal concentrators than are shown inFIG. 10.FIG. 10is intended as a simplified illustration of how the multiple horizontal concentrators may be grouped together and as the basis for a discussion of how individual colors may be used in each of the horizontal concentrators to provide light of a desirable color by overlaying individual color components from multiple sections of the horizontal concentrator. The assembly is pictured with individual sections as described inFIG. 7but may also be constructed with sections as described inFIG. 9. Full white or various combinations of colored LEDs, not necessarily having the same number of LEDs of horizontal concentrators for each color, may be used to generate white light of the desired color balance. It is preferred that color rendering be good, particularly, for the colors of safety related objects such as the red for stop signs and the yellow for warning signs. For example, some combination of red, amber, green, and blue might be used or optionally amber and blue-green augmented by red or simply a combination of red, green, and blue LEDs may be combined to produce the white light. With the relatively high intensity of the light sources which increases their apparent sizes to a person viewing them and with the relatively close spacing of, for example, two or more horizontal concentrators per inch, it is anticipated that when viewed directly at a distance by an oncoming driver, the individual colors of the LEDs will tend to blend to appear as a white light source. At close distance, an observer will see the distinct colors, however, as spacing between the individually colored sources decreases and as intensity increases, the distance at which individual colors will be observed by directly viewing the headlamp source is decreased. It is preferable to order the colors of the concentrators in the array so that complementary colors tend to be adjacent to one another and so that the number of horizontal concentrators before the pattern approximately repeats is made small to reduce the effective spacing between repetitions of the color sequence in the array of horizontal concentrators.

As one more specific example, horizontal concentrator1001may use red LEDs, horizontal concentrator1002may use green LEDs, and horizontal concentrator1003may use blue LEDs. Horizontal concentrator1004may use red LEDs as the start of the next set of three colors and additional horizontal concentrators not shown may continue this repeated pattern. Preferably, sub groups, for example in this case horizontal concentrators1001,1002, and1003which are a subgroup having all of the component colors, should project their light into substantially similar patterns of illumination so that the light from the sources in the subgroup will mix over the pattern of illumination to yield light of a color balance which is acceptably close to white. Additional subgroups of the horizontal concentrators whose color components mix to produce the desired color may project a pattern of illumination which additionally overlays the pattern illuminated by another similar set or, optionally, may be designed to illuminate a different, perhaps partially overlapping, area in the overall pattern of illumination.

FIG. 11depicts a pair of LEDs1120aand1120bwhich may correspond to LEDs720aand720bofFIG. 7. A reflecting ridge1101has been added around the periphery of the LEDs. Preferably, the reflecting surfaces are specular but may optionally be diffused or partially diffused. It is generally desirable to keep the reflecting surfaces of which ridge1101and ridge1102are representative close to the boundaries of the light emitting diodes. The light reflected from these areas must then be taken into account in designing the lens system for the overall pattern of illumination. For low beam operation, LED1120ais illuminated and LED1120bis not illuminated. Because of the high contrast required between the bright and dimly illuminated areas of the low beam pattern, rays of light from LED1120awhich may strike and may be reflected from surfaces which surround LED1120b, for example from ridge1102, may project too much light into the dimly illuminated area. To prevent this, a baffle1103may be placed between LED1120aand LED1120b. This baffle1103is preferably thin so the LEDs may continue to be close together and preferably not higher than required since some rays reflecting from it may be projected into the area which is to be dimly illuminated. The baffle1103is preferably reflecting. If the forward edge1104of the baffle1103extends beyond the surface of the LEDs, as an option, the focus or optical center of the horizontal and vertical concentrators may be adjusted somewhat away from the LEDs surface and generally toward the forward edge1104of the baffle1103. This may be done so that the general defocus of the imaging surface will lead to additional smoothing of the image. This is a way to defocus the vertical concentrator except at the critical edge which projects as the upper edge of the brightly illuminated area of the headlamp low beam pattern of illumination. This technique may help considerably to blend areas between LEDs so that they do not project dark lines in the field of illumination.

This discussion points to another issue which may be addressed in the design not only here but in the entire design to accommodate differences in the patterns of light emission from LEDs of various types or colors or types. Some LEDs will emit more light from their edges than others and additionally the angular distribution of the light emitted may be different and even the intensity and the directional profiles of the light emitted may vary over the surface of the die. In general, these factors may be investigated experimentally and features such as sizes and configuration of various dies and individualized adjustments in the lenses for individual horizontal concentrators for various die colors and/or types are preferably made to improve matching of the resulting patterns of illumination so the mixing of the colors is improved to produce the desired resulting color balance preferably over the entire area of illumination.

FIG. 6illustrated the use of a reflecting lens for the vertical concentrator. In general, there are many options for the optical elements in both the horizontal and the vertical concentrators which are in the scope of this intention. Fresnel lenses of refracting and/or reflecting types may replace the lenses which have been used. Combinations of refracting and reflecting lenses may be used either by application of reflective coatings or through the use of total internal reflection. Reflecting lens surfaces which are generally surfaces of revolution about their focal point may be used to augment, replace, or partially replace the refracting lenses of the horizontal concentrators. One of the ways to characterize the pattern of illumination is to intentionally defocus either an entire or a portion of a lens surface, this is another way of looking at the modifications made to areas105and106inFIG. 1. These techniques to intentionally deviate from using sharp focus in portions of the lens design are considered to be within the scope of this invention. It should also be understood that the examples of the exemplary embodiments which were described are directed toward a specific automotive headlamp application.

In other applications, the vertical concentrator may be oriented in a non-vertical direction and the horizontal concentrators may be oriented in a non-horizontal direction. Each of the cascaded concentrators should preferably have a given direction in which it is operative to preferentially concentrate light and it is preferred that the given direction of preferential concentration for the second of the cascaded concentrators be approximately perpendicular or orthogonal to the given direction for the first concentrator. It is presumed that the scope of the invention extends beyond the specific horizontal and vertical orientations described in the preferred embodiments. Other applications including other headlamp applications may employ concentrators which are operative to concentrate light in preferential directions other than horizontal or vertical. In certain other applications, the functions of the horizontal and vertical concentrators may be interchanged from what has been described in this specification. That is, it is presumed that the entire optical system may be rotated to an entirely new orientation and remain within the scope of invention.

Transparent materials having high indexes of refraction have been formulated by, for example, mixing nanoparticles of silicon in silicones, or epoxies. With some of these materials, high indexes of refraction have been achieved. One possibility with the present design is to use a fluid or moldable solid which has an index of refraction which is substantially higher than that of the surrounding plastic to fill the cavity surrounding the LEDs. The wall of the cavity then becomes the surface of a positive lens and may be designed either as the primary lens surface or as one of the lens surfaces in a multi-element lens structure for the horizontal concentrating function. In the case that it performs the primary horizontal concentrating function, the exterior of the containing plastic may serve either as an element in the vertical concentrating lens or may possibly perform the entire vertical concentrating function. Another option is to provide either single or arrays of micro lenses on the surfaces of either individual or multiple LEDs in the groups of LEDs which are associated with each horizontal concentrator. It is preferred that the micro lenses be made of the materials such as a mixture of nanoparticles which has an index of refraction which is significantly higher than that of the surrounding lens or encapsulating material.

As an alternative, the material which incorporates a mixture of nanoparticles to achieve high index of refraction may simply be used as the preferred high index of refraction material to fill a more conventional cavity surrounding the LED structures in a configuration as previously described.

FIG. 22is a cross-sectional view from the top of a preferred structure passing directly through the centers of the vertical concentrator2205having a two element cylindrical lens structure in the longitudinal direction.FIG. 22illustrates a longitudinal cross section taken directly through the center of an outer cylindrical lens element2226of the two element cylindrical lens structure making up the vertical concentrator2205.FIG. 22also illustrates a similar longitudinal cross section taken through the center of an inner cylindrical lens element2225of the vertical concentrator2205. The fragmentary view depicts a portion of a base assembly with its arrays of LEDs and associated horizontal concentrators2201through2204, each having a toroidal lens structure. The total structure may contain many more than the four horizontal concentrators with their associated LEDs which are depicted. This view illustrates the sharing of a single vertical concentrator with multiple horizontal concentrators and LED assemblies.FIG. 16is a front view of the same structure which includes a portion of the end of the structure not shown inFIG. 22and which does not include the detail shown here on the cylindrical lens elements of the shared vertical concentrator2205.

For most transparent refractive materials, the index of refraction is higher for shorter wavelengths resulting in a shorter focal length for blue than for red and intermediate focal lengths for colors such as green or amber. In the preferred structure, LEDs of similar or preferably identical colors are grouped together in individual horizontal concentrators and the projection of patterns of illumination of the various component colors which overlay one another is preferably utilized to perform at least a portion of the color mixing function. One of the significant advantages of this arrangement is that lens design and component positioning may be adjusted individually for each of the horizontal concentrators to accommodate the index of refraction with its resulting focal length and possibly other lens properties for the individual wavelength range of the LEDs in each of the particular horizontal concentrators. InFIG. 22, the position of each of the groups of LEDs and the associated toroidal lens structures in the horizontal concentrators2201through2204is individually selected based on the color of the LEDs in the respective structures so that each is at the proper focal distance from the inner cylindrical lens element2225and the outer cylindrical lens element2226of the vertical concentrator2205to attain proper focus and proper lens performance for the colors of the LEDs for each of the individual units. For example, in the exemplary structure which is substantially enlarged inFIG. 22, the nominal focal length of vertical concentrator2205may be about 10 mm, and depending on optical properties of the lens material, this nominal focal length may vary by approximately 0.3 to 0.4 mm between best focus for red and best focus for blue. Thus, in the unit as depicted, the horizontal concentrator2201has red LEDs so that the LEDs and associated toroidal lens structure are placed farther from the lens structure of the vertical concentrator2205to properly focus the concentrator for the red wavelength for which the index of refraction is lower. The toroidal lens structure of the horizontal concentrator2203has blue LEDs so that the LEDs and lens structure of the associated horizontal concentrator are placed closer to the lens structure of the vertical concentrator for proper focus of the concentrator for the blue wavelength for which the index of refraction is higher. The horizontal concentrator2202preferably has green or amber LEDs and the distance of its LEDs and associated toroidal lens structure from the lens structure of the vertical concentrator2205is between that of the red unit of the horizontal concentrator2201and the blue unit of the horizontal concentrator2203so the distance of its placement relative to the lens structure of the vertical concentrator2205is between that of the red and blue units.

With the very low F number optics which are used to efficiently collect the light from the LEDs and direct it into the required pattern, the color aberrations of the preferred system would be very large without adjustments of focal lengths to accommodate the individual color components. In the preferred system, light from individual sources having differing and more restricted color distribution is processed in partially individualized, parallel optical paths and focal lengths are adjusted to individually accommodate light of different color distributions within these individualized optical paths within the optical system. For systems which do not utilize sources of differing colors or which do not contain the individualized optical components, color corrected lenses which utilize combinations of lens materials and color correction techniques such as those used in photography may be employed to achieve the needed color correction. Other techniques which may be used to achieve color correction include the use of a combination of diffracting and refracting optics to implement color correction and/or the use of reflecting optics which, in general, do not exhibit the serious color aberration problem. The use of color corrected lenses for the optics is within the scope of this invention but does normally add to complexity and cost given the desire to use plastic lens elements and the limited selection of transparent plastic materials which are suitable for lens applications in the difficult automotive environment.

The horizontal concentrator2204which includes its associated red LEDs may be the start of another, for example, red, green, blue sequence of horizontal concentrators and is illustrated accordingly positioned for a focal length similar to that of the red unit of the horizontal concentrator2201. The profile view includes refracting lens portion2221, reflecting lens portion2223, exit surface2222for the reflecting lens portion2223, and inner cavity profile2220, all of which preferably form a profile for a lens which is generally a surface of revolution, preferably about an axis which runs in the plane of the paper, is preferably approximately parallel to and preferably approximately coincident with the focal center of vertical concentrator2205. Further, this axis of revolution is preferably positioned on or close to the optical center2254of the cluster of LEDs in the horizontal concentrator2204. The horizontal concentrators are preferably keyed to a heat conducting base2210. The heat conducting base2210preferably extends over the back of most or all of the LED headlamp unit. LED mounting posts2212are preferably of a good heat conducting material such as copper and are preferably pressed into holes2211in the heat conducting base2210so that good thermal and electrical contact is provided between LED mounting posts2212and the heat conducting base2210. A circuit2215may, for example, be fabricated from polyimide insulated flex circuit material which may be bonded to the heat conducting base2210. The circuit2215preferably extends partially over the hole2211into which the LED mounting post2212is pressed and the mounting post2212preferably has areas, preferably flat, which serve as a rigid backing for the circuit2215in the areas where it extends over the mounting post structure. The circuit2215has bonding pads or other LED electrically conductive attachment mechanism to terminate bond wires2217at points such as2213. The other end of the lead bond wires connect to the LEDs2218. A cavity2219formed by the inner cavity profile2220is preferably filled by a relatively flexible transparent material such as a silicone gel. In another view,FIG. 15for example, an expansion interface between air and the gel-filled cavity is depicted. The expansion interface is visible in the view ofFIG. 15but not in the view ofFIG. 22. Bonding layer2214is provided, preferably in addition to mounting posts2212to secure and seal the horizontal concentrators to the base structure.

An optional insulating layer2227may be provided to electrically isolate the heat conducting base2210from a heat conducting mounting structure (shown inFIG. 15) to which the lamp is mounted. As an option in some designs, it may be desirable to further electrically isolate the mounting substrate for LEDs in one or more of the horizontal concentrators from mounting substrates of other horizontal concentrators. To accomplish this, the heat conducting base2210may be divided into electrically isolated portions. When this is done, it is preferable to use circuit2215and perhaps also insulating layer2227to maintain proper spacing between electrically isolated regions of heat conducting base2210in the finished structure. To facilitate the assembly, it is further preferable to provide temporary connecting links between regions of heat conducting base2210which will ultimately be isolated and to leave these links in place through a portion of the manufacturing process to maintain precise relative positioning of parts in the assembly through the manufacturing process. These links are then removed in a stage in the manufacturing process where they are no longer required.

Typically, some of the electrical connections to the LEDs are made through an electrical connection to the mounting base which may, for example, be facilitated by the use of a solder connection or of conducting epoxy to mount the LEDs to the substrate. Additional connections to the LEDs may be made through the lead bond connections. Appropriate electrical connections are made between circuit paths of the circuit2215and the one or more electrical conducting areas of heat conducting base2210which preferably provides both thermal and electrical connection to the LEDs. As illustrated, the heat conducting base2210and the mounting posts2212normally provide dual electrical and thermal conducting functions.

FIG. 19is a top view,FIG. 20a side view, andFIG. 21a front view of an LED mounting post2212depicted with mounted LEDs2218.FIG. 19illustrates a first column1904and a second column1905of LEDs2218. Surface1901shown in profile serves as the backing for traces of the flexible circuit2215shown in fragmentary view inFIG. 17. The extended portion1902of the post2212provides the standoff distance for proper focus of the LEDs. It is preferred to use different posts and different horizontal concentrators with different standoff heights to establish the proper focal distance for LEDs of different colors. InFIG. 20, four rows2004,2005,2006, and2007of LEDs2218are depicted in profile view on the face of the LED mounting post2212. In this exemplary application, the upper two rows2004and2005are preferably illuminated for both the low and high beam modes of operation and the lower two rows2006and2007of LEDs are illuminated only for high beam operation. Either group of LEDs may optionally be replaced by a larger LED or some other number or pattern of LEDs. In the front view ofFIG. 21, cylindrical portions2107of the mounting post2212are shown. These are the surfaces which are pressed into the hole2211provided in the heat conducting base2210illustrated inFIG. 22and mate with secure mechanical, electrical, and thermal contact with the heat conducting base. Beveled edge2102facilitates the insertion operation in the press fit assembly process. Flat surfaces2106provide annular openings between the support post and the preferably round hole2211in the conducting base2210ofFIG. 22into which the LED mounting post2212is pressed. These annular openings are used to inject the preferably transparent, preferably flexible material which preferably has a relatively high index of refraction into the lens cavity of the associated horizontal concentrators. The openings also provide a volume into which the fill material may expand or from which it may contract to accommodate differences in expansion rates between the fill material and the containing volume. The openings may optionally be of other shapes and are convenient but do not have to be incorporated as part of the LED supporting post.

FIG. 17depicts a simplified fragmentary section1704of the circuit2215which covers the heat conducting base2210in the region around one of the clusters of LEDs2218. Bond wires2217connect to bonding pads1703which are preferably part of the pattern of conductors on the circuit2215. Circuit traces not shown in the simplified drawing make appropriate connection of the LEDs to circuit components. A top1705of the mounting post2212which is shown in more detail inFIGS. 19,20and21, may provide an additional electrical connection to each of the LEDs2218, providing a conductive path to the heat conducting base2210described in the description ofFIG. 16below. The heat conducting base2210, as described inFIG. 16, is preferably also electrically connected to a conductive path on the circuit2215. Circular contours1707form the outer portion of the outline of two annular openings1706in the circuit board material of fragmentary section1704. They are preferably sized and positioned to approximately coincide with the edges of the hole2211in the heat conducting base2210into which the LED mounting post2212is pressed. As described inFIGS. 19,20and21, a space between the hole2211in the heat conductive base2210and flats or other channels on the LED mounting post2212provide open access channels to the cavity around the LEDs2218. In the finished assembly, these cutouts in the circuit maintain an unblocked path of the channels into the lens cavities which surrounds the LEDs. The tab-like areas on the fragmentary section1704of the circuit2215which have the circuit board bonding areas for the lead bonds to the LEDs preferably extend over supporting flats on the mounting post as described in the description ofFIG. 19below.

FIG. 18is a vertical cross section view through the center of one of the horizontal concentrators (e.g.,2201) oriented in its preferred location for the exemplary automotive headlamp application. Horizontal concentrator2201includes refracting lens portion2221, inner cavity profile2220, support base area1811and integral mounting posts1808all shown in sectional view. Heat conducting base2210has portions of a conducting plate1807, insulating layer2227and bonded circuit2215all of which appear in sectional view. LED mounting post2212with LEDs and associated lead bonds are also illustrated inFIG. 18.

In an exemplary assembly process, the finished circuit2215may be bonded to the heat conducting base2210. Circuit components may be soldered or otherwise assembled to the laminated circuit board assembly. The LED support posts2212optionally with or without the LEDs die bonded to them may be inserted from the back into the heat conducting base2210. Any remaining die bond and the lead bond operations may be completed. Bonding layer2214may be dispensed either to the back of horizontal concentrator2201or to the heat conducting base2210around the LED assemblies and the horizontal concentrator2201may be pressed into position. Transparent fill material1804may then be injected through openings1817and cured.

Several features of the structure enhance its ability to withstand relative movement of parts with temperature excursions due to thermal expansion differences. The bonding layer2214is preferably relatively flexible as is transparent fill material1804. The interface1805of fill material1804to air in openings1817provides a flexible interface for expansion and contraction of the fill material1804during thermal excursions. Without this flexible interface, the pressure due to the expansion of the fill material1804might fracture the bonding layer2214or cause other unwanted displacements or mechanical damage. Shrinkage of the fill material1804in a confined chamber might lead to tears in or separation of the fill material1804from surfaces in the cavity, for example, separation along an optical interface such as at the inner cavity profile2220or from the LEDs leading to distortion and reflections in the optical path and possible damage to LED bonds. The holes2211in heat conducting base2210are preferably shaped in an hour glass like pattern as shown. The features just described are exaggerated for clarity in the view andFIG. 18. The area of greatest constriction in the hole2211preferably occurs toward but not at the outer end of post1808. With this configuration, the posts1808may be sized for a secure press fit in an area of constriction1809while providing a modest clearance at the top of the hole in the area1810. This modest clearance provides a good conically shaped constriction into which to press the posts1808. Furthermore, small differences in spacing of the posts1808on horizontal concentrator2201relative to the spacing of holes2211in heat conducting base2210due to thermal expansion mismatches and/or initial spacing mismatches are accommodated at least in part by bending or flexing of the posts along their length instead of requiring direct deformation of the part as would be the case if the hole and post where a press fit along the full length of the post or toward the area where the post joins the heat conducting base2210of the lens part.

Groove area1802provides a small offset step so that base area1811may be pressed into solid contact with the face of the circuit2215while providing a small controlled clearance for bonding layer2214. The groove area1802may optionally also provide a space for spill out of excess glue of the bonding layer2214around the glue joint area.

Turning now toFIGS. 12aand12b, there are depicted profile views of an illumination assembly1200comprising the horizontal concentrator2201; the inner cylindrical lens element2225; and the outer cylindrical lens element2226. The cross section depicted inFIG. 12bis along the line12b-12bofFIG. 12a. As depicted inFIG. 12a, a first light source or LED2218and a second light source or LED2218may be included to project light through individual inner lens elements which may in turn be associated with a plurality of inner lens elements to project light through a given middle lens element and/or an outer lens element. As depicted inFIG. 12b, a given inner lens element may only have a single light source associated therewith. It should be understood that more than two light sources may be associated with a given inner lens element, a given middle lens element, a given outer lens element, a combination thereof or a sub-combination thereof. In at least one embodiment an inner lens element comprises the refracting lens portion2221at least partially surrounded by the exit surface2222. In at least one embodiment, the reflecting lens portion2223at least partially surrounds the refracting lens portion2221and/or the exit surface2222. In at least one embodiment, the material1804having a different refractive index as compared to material of the horizontal concentrator is provided. In at least one embodiment, the inner cylindrical lens element2225comprises a first surface1245and a second surface1246. In at least one embodiment, the outer cylindrical lens element2226comprises a first surface1253and a second surface1254.

FIGS. 13athrough13cdepict plan views of various illumination patterns with topographical type illustrations. The individual gradient lines1300a,1300b,1300crepresent normalized values with ten increments.FIG. 13aillustrates the illumination pattern emitted from a horizontal concentrator similar to that depicted inFIG. 12awith two light emitting diode chips similar to that depicted inFIG. 7.FIG. 13billustrates the illumination pattern emitted from a lens element that has received the illumination pattern as depicted inFIG. 13a.FIG. 13cillustrates the illumination pattern emitted from a lens element that has received the illumination pattern as depicted inFIG. 13b. The x and y axis ofFIGS. 13a-13crepresent degrees of divergence with respect to a central optical axis.

FIGS. 14athrough14cdepict plan views of various illumination pattern topographical type illustrations. The individual gradient lines1400a,1400b,1400crepresent normalized values with ten increments.FIG. 14aillustrates the illumination pattern emitted from a horizontal concentrator similar to that depicted inFIG. 12awith two offset light emitting diode chips similar to that depicted inFIG. 9.FIG. 14billustrates the illumination pattern emitted from a lens element that has received the illumination pattern as depicted inFIG. 14a.FIG. 14cillustrates the illumination pattern emitted from a lens element that has received the illumination pattern as depicted inFIG. 14b. The x and y axis ofFIGS. 14a-14crepresent degrees of divergence with respect to a central optical axis.

FIG. 15is a sectioned side view of an exemplary LED headlamp assembly1500. The assembly1500includes the vertical concentrator2205consisting of a two element cylindrical lens assembly having the outer cylindrical lens element2226and the inner cylindrical lens element2225. These lenses focus light from an array of individual LED and horizontal concentrators (one of which is shown in sectioned view as2201) which are mounted to the heat conducting base2210. The heat conducting base2210is mounted to and is preferably in good thermal contact with a heat conducting mounting assembly1510which has an adjustable position. The mounting assembly1510hinges on an elongated rod-like assembly1560which includes a mounting member1561shown in partial detail which may optionally provide additional adjustment in the horizontal direction. The mounting member1561preferably maintains good thermal contact of the headlamp assembly to a heat sink member which may optionally be a massive portion of the frame of the vehicle and/or, for example, a finned heat sink having fins which are preferably external to any windowed enclosure in which the lamp assembly may be placed. Most of the components other than spring clips1501, the heat conducting mounting assembly1510and the elongated rod like assembly1560are described elsewhere in some detail. Features of the heat conducting base2210are described in association withFIG. 16and various features of the horizontal concentrator2201are described in association withFIG. 18in particular and also in association withFIGS. 17,19,20,21and22.

The surface1562is preferably cylindrical rather than spherical in shape so that a long, relatively continuous line of thermal contact may preferably be maintained preferably along nearly the full length of the LED headlamp assembly. Clearance between cylindrical surface1562of the elongated rod like assembly1560and mating cylindrical surface1513in heat conducting mounting assembly1510is preferably small to maintain good thermal contact and is preferably lubricated with a heat conducting grease. Further, a spring member1505preferably maintains pressure to hold the cylindrical surface1562in secure contact with the mating surface1513of the heat conducting mounting assembly1510to provide a low backlash pivot and good thermal conductivity across the hinged area. The spring member1505preferably includes a feature to securely retain it. For example, one edge may be folded over to an acute angle. This is inserted into the slot1512in the heat conducting mounting assembly1510and serves to spring against the opposing walls of the slot in order to retain the spring member in its proper position. The opposite edge of spring member1505is preferably formed to contact cylindrical surface1562smoothly to allow rotation without binding and is preferably designed to provide uniform pressure along the length of elongated rod-like assembly1560holding it in close contact with the cylindrical surface1513of the heat conducting mounting assembly1510. This pivotal structure is preferably linked to a headlamp adjustment system which may provide manual and preferably also automatic headlamp aiming features. Heat conducting base2210includes mounting holes2211for a number of the horizontal concentrators. These horizontal contractors are described in some detail elsewhere.FIG. 15illustrates the engagement of the V-shaped positioning surfaces1524with the corresponding channel in the inner cylindrical lens element2225and the V-shaped projection1541of the inner cylindrical lens element2225which engages a mating groove in the outer cylindrical lens element2226. Spring clips1501preferably maintain pressure along substantially the full length of the lens assembly at both the top and bottom or opposing sides of the assembly. There are preferably features such as the slanted surface shown in surface1511of the heat conducting mounting assembly1510and surface1552of outer cylindrical lens element2226which the spring clip engages to prevent the spring clip from coming off. Outer cylindrical lens element2226preferably does not make direct contact with the heat conducting base2210. Instead, the clamping pressure of the pair of spring clips1501is preferably transferred generally across the V-shaped positioning surfaces from the outer cylindrical lens element2226to the inner cylindrical lens element2225, from the inner cylindrical lens element2225to the heat conducting base2210, and finally from the heat conducting base2210to the heat conducting mounting assembly1510. Heat conducting mounting assembly1510may optionally be electrically isolated from the heat conducting base2210by insulating layer1521. The heat conducting mounting assembly1510and the heat conducting base2210should be fastened or otherwise key together so that they are registered in and maintain proper position one to another. The detailed structure is exemplary and other configurations are within the scope of the patent. In summary, a system of springs and mating reference surfaces serve to maintain pressure across a prescribed pattern of reference surfaces holding precise and repeatable relative placement tolerances between parts of the lens assembly where required and allowing for relative motion or slippage in directions where differences in thermal or moisture induced expansion rates would otherwise cause problems and possible malfunction of the device. The system is designed to tolerate relative motion or variance in initial positioning in the directions where inter-part slippage is facilitated and to continue to operate normally in the face of slippage or differences in initial positioning due to temperature changes, or other environmental or tolerance related reasons. The path and general containment of O-ring1504is described in association withFIG. 16. As indicated, a seal is maintained generally between the surface of circuit2215which is part of heat conducting base2210and a surface molded into outer cylindrical lens element2226. The O-ring is retained in a channel which may in part be formed on the inner side by inner cylindrical lens element2225and on the outer side by a lip on outer cylindrical lens element2226. This cylindrical lens assembly consisting of inner and outer cylindrical lens elements2225and2226collects light from multiple horizontal concentrators including2201and focuses it in a direction generally forward of the vehicle. Optionally, more than one headlamp unit may be used in a headlamp module. As explained in other parts of the patent specification, the horizontal concentrators of which2201is one are designed so that relatively sharp focus of the lens elements2225and2226of the vertical concentrator2205is relatively unhindered by the intervening toroidal lens assemblies of the horizontal concentrators. Ray1502illustrates the upper extent and ray1503the lower extent of a relatively wide collection angle of the vertical concentrator2205.

It is preferable to shape supporting members1542of the inner cylindrical lens element2225so that the assembly springs against spacers1543allowing these spacers to establish the position of the inner cylindrical lens element2225with active lens surfaces1245and1246relative to the horizontal concentrator2201and the outer cylindrical lens element2226. Then, as an option, the height of spacers1543may be changed modestly to adjust focus over a limited range without the need to change tooling for the lens parts which are preferably fabricated by molding.

The index of refraction of the preferred polycarbonate lens material decreases with increasing temperature making it desirable to increase the focal distance more than in proportion to the increase in lens size due thermal expansion with increasing temperature. Because of the greater thermal expansion coefficient for the plastic relative to the material of the base1522, the distance between V-shaped positioning surfaces1524expands more for the inner cylindrical lens element2225when unrestrained than the comparable distance between V-shaped positioning surfaces1524for the restraining base1522. This restraint of the inner cylindrical lens element2225by the heat conducting base2210effectively squeezes the supporting members1542of the lens support slightly closer together than they would otherwise be as temperature increases. This displacement is accommodated primarily by bending of angled portions1544of the lens support. If the angled portions1544of the lens support were perpendicular to supporting member1542, this thermally induced displacement would have minimal effect on the spacing of the inner cylindrical lens element2225relative to the horizontal concentrator2201, but with the obtuse angle as depicted between support member1542and the angled portions1544, the inner cylindrical lens element2225will be pushed away from the horizontal concentrator2201as temperature increases. This motion is in the correct direction to at least partially compensate for the decrease in refractive index of the lens material with increasing temperature. Furthermore, the obtuse angle shown is only for illustration and increasing the obtuse angle between lens support members1542and lens angled portions1544generally within the range of 90 to 180 degrees will increase the displacement and the resulting focal distance of the lens with increasing temperature providing at least partial compensation for the change in the refractive index of the lens material with temperature.

There are a number of possible options for the optical design of the lens elements of the vertical concentrator which constitute the optical portions of inner cylindrical lens element2225and the outer cylindrical lens element2226. Since the low beam pattern is the most difficult to provide, the following discussion will assume that only the LEDs normally used for the low beam pattern are illuminated. For the general proportions indicated in the example ofFIG. 15, if the lenses in the inner cylindrical lens element2225and the outer cylindrical lens element2226of the vertical concentrator2205are designed for sharp focus, the LEDs illuminated for the low beam function project into a pattern having an elevational pattern of 5 to 6 degrees due to the size of the pattern of LEDs relative to the focal length of the lens system. The elevational angle desired for the system is somewhat more than twice that with considerable gradation in intensity desired with the highest intensity desired close to the upper edge of the brightly illuminated area of the pattern. Several goals which are in partial tension with each other and a set of viable objectives for the lens design will be presented here. Among competing goals are to collect light over a wide angle as, for example, indicated by bounding rays1502and1503. Another goal is to “share the refractive load” keeping the maximum refractive angle at each of the four lens surfaces approximately equal and preferably in the neighborhood of 15 degrees, for example, for rays which are approximately in the plane of the paper forFIG. 15, i.e., approximately normal to the longitudinal axis of the lens. Another goal is to limit the thickness of each lens to improve molding properties. Another goal is to keep the overall height of the lens reasonably small. This objective translates generally into keeping the air spaces between lenses relatively small and in getting as much use out of surfaces1246and1245as is reasonable. The lenses as depicted provide approximately equal maximum refractive angles at each surface and were initially designed for relatively sharp focus with dashed surface1556as the front surface of the lens, with the objective to generally focus light from the optical center of the LED array into parallel rays as viewed from the end as inFIG. 15. Next, the dashed surface1556was modified by generally retaining the radius of curvature of the upper part of the outer cylindrical lens element2226in the first surface1253to generally maintain relatively sharp focus in the upper area of the first surface1253to maintain the higher intensity at the upper portion of the low beam pattern. As part of the modification, the radius of the lower portion1555of this outer lens face was generally increased, preferably keeping it approximately tangent to the upper portion. This increased radius has the effect of moving the focal point for this lower portion of the lens to a position back of the focal center of the LEDs serving to fan the projected light pattern in the downward direction. The modifications as indicated to this point leave the upper portion of the lens essentially unchanged from the dotted profile and progressively increase the thickness of the lens in moving downward through the lower portion1555roughly from the center of the lens toward the ray1503. To minimize this extra thickness, the entire front surface was rotated clockwise by about three degrees, for example, about a point roughly where upper bounding ray1502intersects the front lens surface. This introduces aberrations and requires re-trimming the focus; but, the primary effect since it effectively removes a prism shaped piece of plastic is to refract the entire beam pattern upward in elevational angle by just over one degree. This overall bending may be accommodated for by overall aiming of the lamp. With cylindrical surfaces, a prescription for choice of appropriate segments of a lens surface followed by translation may lead to a similar modification. A more general description of the effect achieved is as follows. The lens system is modified in a way which reduces the thickness and/or increases the symmetry of a lens element with the side effect of creating a change in the angle of emission of the project pattern of illumination. The resulting change in the angle that the pattern of illumination is projected from the lamp assembly is then corrected at least in part by changing the aiming of the lamp structure.

FIG. 16depicts a fragmentary portion of the base assembly for the exemplary LED headlamp assembly1500. Four clusters of LEDs with their associated toroidal lens structures or horizontal concentrators are depicted as units2201,2202,2203, and2204. There may be many more clusters of LEDs in a total headlamp assembly. The assembly, as depicted, is generally rectangular in shape and is bounded on the outside by outline1601. The fragmentary portion is shown extending to cut line1628. The assembly preferably is built on a heat conductive base, for example, a strip of preferably work hardened copper which may, for example, be 1.5 mm thick. This base preferably has isolated conductive circuits formed on it or attached to it. For example, a polyimide insulated flex circuit may be bonded to the stamped and formed copper strip and provides connecting paths to the LEDs. The circuit preferably includes an external connection to receive power and control signals and perhaps to return status signals. Connection is provided by flex circuit area1606which may extend beyond the base preferably as an extension of the circuit material which extends over the base, may be flexible so that it may be positioned to make the connection, and preferably has contact areas depicted as1605and interconnecting traces not shown in this simplified drawing. The circuit may support components represented here by component1627and may include various interconnections, for example, a connection depicted at1619to the underlying copper strip. The underlying strip is preferably in electrical and thermal contact either directly serving to mount the LEDs or indirectly as illustrated serving to attach the members to which the LEDs are attached. With the preferred assembly which is depicted, it is preferable that the base assembly serve multiple functions which may include the functions just described and also may include functions to be described below. To meet the requirements for the pattern of illumination especially for the low beam as described before and to overlay patterns of differing colors precisely enough to properly blend the colors and to maintain a reasonably small structure, it is necessary to accurately position the LEDs and lenses relative to each other. It is especially important to maintain precise repeatability in the positioning pattern since the repeatability in the optical system from one group of LEDs to the next is one of the main factors which leads to proper registration of the patterns of illumination from one group of LEDs to the next.

The underlying strip preferably includes features, for example holes1636, to position and secure the LED assemblies and holes2211to position and secure the individual horizontal concentrators. Holes1609and1610are like holes2211and1635and show more clearly inFIG. 16because a horizontal concentrator and LED assembly is not placed in them. Glue is preferably also used to retain and seal the toroidal LED lens assemblies to the base structure. The preferred structure includes raised projections1629-1634. These raised projections preferably have pairs of precisely formed preferably V-shaped positioning surfaces1524to properly register and position the cylindrical lens assembly relative to the LEDs and their associated toroidal lenses. For example, in the preferred structure the formed, raised portions1629through1634provide a pair of rows of aligned V-shaped reference surfaces. One is close to the upper and one is close to the lower edge of the base structure. These rows of reference surfaces register with corresponding V-shaped grooves in the inner cylindrical lens element. When positioned on the base, the inner cylindrical lens element assumes the position indicated by the outline shape1604which depicts the nominal edge of the inner cylindrical lens element. The outer cylindrical lens element is then referenced by a similar V engagement to mating V-shaped projections in the inner cylindrical lens element with V-shaped grooves in the outer cylindrical lens element. It is preferable to provide some extra clearance in the outer cylindrical lens element close to its ends to allow for the differential expansion of the end of the outer cylindrical lens element relative to the base structure. Except for these portions of the structure, slight flexing of the lens structures can take place to accommodate the difference in expansion rates between the lens material and the base material as it affects the spacing of the rows of reference surfaces and the mating grooves and the lens structure. When the structure is relatively long, there may be considerable differential movement between the base and the cylindrical lens assembly in the direction parallel to the rows of positioning projections. This is the reason that the groove structure is preferred, since the structure may readily slide along these grooves to accommodate differences in thermal expansion rates while maintaining the required alignment and focus distance in the directions which are generally perpendicular to the grooves. The choice of a lens type (cylindrical, for example) for the vertical concentrator with optical properties which are tolerant to displacement along the axial direction and the mechanical design to permit movement due to expansion differences of the vertical lens structure relative to the lens structures of the horizontal concentrators with their associated LEDs are features of the invention which solve a difficult problem in accommodating differential thermal expansion. The end blocks of which the one1608is shown are preferably used to retain an O-ring seal as it goes around the end of the structure and also to directly or indirectly register the positions of the intermediate and outer lens assemblies. The end blocks are preferably positioned to allow clearance for differential expansion over the required temperature range while maintaining proper positioning of the cylindrical lens assemblies relative to the base assembly in the direction of the positioning grooves. The segmented array of locating projections in the base structure is preferred to a continuous formed groove so that the circuit material may extend around the segmented projections and, among other things, provide a smooth sealing surface to act as a portion of the seal with the lens cover assembly. This structure also allows the circuit material to pass under the seal and thereby form a continuous section with the flex circuit area1606as depicted. The requirements for precision make it preferable to use a progressive die in forming the positioning projections and holes for the LED and lens structures. It is preferable to fabricate a metal strip which is part of the base assembly as a continuous strip. This is why the projections1629and1630and the associated sets of holes for example1609and1610are provided and perhaps not fully utilized. The segmented pattern of projections in addition to providing space for the circuit to surround the projections has also provided space for flat contact to the seal at the ends of the structure. Thus, it is a desirable feature of the structure to provide for utilization of a continuously formed and/or punched substrate section where the features which are provided at uninterrupted uniform intervals along the strip are accommodated by the design whether or not they are fully used. This also saves tooling when different lamp modules use different numbers of horizontal concentrators in a strip.

Contours1602and1603and outline shape1604do not necessarily represent visible features in the base structure. Instead, they are included to indicate regions of interest in the structure. Outline shape1604is nominally at the edge of the intermediate lens assembly and the region between contours1602and1603is the area which should preferably be kept flat and smooth to serve as a surface to form a seal with the O-ring which is captured by a gland in the cover portion of the outer cylindrical lens assembly. The end block1608and the outline shape1604of the intermediate lens assembly may serve to retain the O-ring in a space between the base and the outer lens assembly.

FIG. 23is a top view,FIG. 24a side view, andFIG. 25a front view of the toroidal lens of the exemplary horizontal concentrator. The part is preferably a one-piece part preferably molded of a material such as transparent polycarbonate. One of these lens assemblies is preferably used for each cluster of LEDs in the lighting unit. There are preferably several versions of this unit having different distances from the surface of a support base area which engages the mounting surface to the optical center of the lens to properly align the axes of the surface of revolution of the lens with the standoff height of the LEDs and the focal length of the cylindrical lens assembly of the vertical concentrator for each of the various colors used in the lamp assembly. InFIG. 23, parabolic curve section of reflecting lens portion2223, exit surface2222and refracting lens portion2221correspond, respectively, to lines or curves2605,2607, and2621of the profile2600ofFIG. 26. The profile2600ofFIG. 26is preferably used as the profile to generate the surface of revolution of the horizontal concentrator depicted inFIGS. 23 through 25. Inner cavity profile2220is the outline of the portion of the lens cavity used to contain the LED and lead bond wire assembly and is also preferably part of the overall surface of revolution. Portion2301of the overall curve is the outline of the portion of the cavity where the surface of revolution is blended into the base opening.

InFIG. 24, semicircular curve2406is the outline of the tip of refractive lens portion2221generated by rotation of reflecting lens portion2221; semicircular curve2220is traced by the intersection of curve exit surface2222and reflecting lens portion2221in the surface of revolution; and curve2407is traced by the intersection of reflecting lens portion2223and exit surface2222in the surface of revolution. The semicircular portion of curve2408is the outline of the toroidal portion of the inner cavity generated by rotation of inner cavity profile2220. Base area1811supports integral mounting posts1808and has surface2402shown in profile view which positions the lens against the surface of the circuit board when posts1808are pressed into the base of the assembly shown inFIG. 16. The groove area1802shown in profile view is a transition to surface2404also shown in profile view which serves to glue the lens assembly to the base assembly ofFIG. 16. The groove area1802optionally includes space for excess glue to spill out during the gluing process.

InFIG. 25, the refractive lens portion2221is shown, the window area for the reflective lens portion2223of the lens is outlined by2504and the exit surface2222of the reflective lens portion2223is shown. The toroidal portion of the inner cavity is outlined by inner cavity profile2220and the opening into this cavity at the base of the lens assembly is outlined by curve2408.

A profile2600is composed of curve2605to generate a reflective surface, curve2607to generate an exit window for the rays reflected from the surface generated by2605, curve2621to generate a refracting lens surface, profile segment2624to generate an exit window for rays reflected from the surface generated by profile segment2625, and profile segment2625to generate a second reflecting surface. This composite profile2600is rotated about centerline2603to generate the lens surface. LED or LED cluster2218is preferably situated so that centerline2603passes approximately through the portion of the LED chosen to project into the primary area in the projected field of illumination. This is an exemplary design and many modifications to this design are within the scope of this patent.

The curve2621to generate the refractive surface is elliptical and has its focal point at2614. Representative ray2619emanating from focal point2614is refracted at curve2621emerging as ray2620which is approximately parallel to centerline2626of the lens structure. Similarly, symmetrically placed ray2623is refracted emerging as ray2622which is also parallel to the centerline2626. Rays2619and2623may be considered boundaries of a cone of focus which intersects light emitting diode2218in an area extending from2611to2615. In the example, the LED or LED array2218has been placed well short of focus between the focal point2614and the corresponding lens surface which is generated by curve2621. This is to illustrate that even though the LED2218is placed well short of focus, the intensity of the central beam parallel to centerline2626may still be relatively strong, perhaps nearly as strong as if the centerline2603and an LED were placed closer to the focal point2614. With the substantial defocus, rays2618and2627which are close to the outer extent of lens curve2621are projected, respectively, into rays2608and2628which diverge substantially from the direction of the centerline2626. Ray2629which emanates from the most distant edge of LED2218is refracted as ray2630which diverges even farther from centerline2626. In the headlamp application, the action of the curve2621to bend rays generally toward centerline2626while allowing the rays to fan or diverge over a substantial range is generally what is required for the relatively wide horizontal pattern of illumination for the automotive headlamp.

Added desirable features for the lens are to capture more divergent rays such as ray2616and to direct them into a useful portion of the pattern of illumination of the headlamp. It is desirable to project these divergent rays in a direction which is very nearly parallel to centerline2626in order to increase the intensity of the center area for the pattern of illumination projected by the headlamp. The curve2605has center axis2613and is preferably parabolic with focal point2612nominally at the center of LED2218. Ray2616emanating from focal point2612is reflected as ray2606which is parallel to the center axis2613of the parabolic curve2605. Ray2606is refracted as it passes through curve2607and emanates as ray2609. As part of the design, the direction of the center axis2613of parabolic curve2605is selected to compensate for the refractive angle at curve2607so that ray2619emanates in a direction which is nearly parallel to center line2626. Rays from the LED which strike a parabolic surface generated by curve2605in the region of area2601may strike a surface generated by curve2621rather than passing through the intended window generated by curve2607. The number of rays reflecting from the surface generated by curve2605which do not pass through the window generated by curve2607may be reduced by increasing the focal length of parabolic curve2605maintaining its center at focal point2612and its central axis2613. This has the effect to move curve2605generally upward as depicted inFIG. 26and to increase the length of curve2607. This also increases the width of the lens reducing the number of horizontal concentrator selections which will fit into a given length of lens structure. Depending on the pattern of emission of light from LED2218, relatively few light rays may strike area2601in which case it may be preferable to use the smaller size as depicted rather than to employ a parabolic curve having a larger focal length which allows rays striking it over a larger part of the generated surface to exit through the intended window generated by curve2607. These are the general considerations to balance against one another in the choice of the focal length for parabolic curve2605. Another option is whether to coat the reflecting surface generated by parabolic curve2605with a reflecting layer or to use it in a totally internal reflecting (TIR) mode. For rays emanating from LED2218which impinge on curve2605generally close to area2601, the angle of incidence may be too shallow for total internal reflection to take place. It is optional and a matter of cost, efficiency, and performance trade-offs as to whether the surface generated by curve2605should be used uncoated in a totally internal reflection mode or whether it should be coated with a reflective surface. Profile segment2625is preferably placed symmetrically to curve2605and the same general description given for curve2605also applies to the surface generated by profile segment2625and its associated exit window area generated by profile segment2624.

FIG. 19is a top view,FIG. 20a side view, andFIG. 21a front view of the preferred LED mounting post2212depicted with an array of eight LEDs2218mounted. In the top view ofFIG. 19, two columns1904and1905of LEDs are depicted. Surface1901shown in profile view provides a backing for bonding areas on the flexible circuit2215shown in fragmentary view inFIG. 17. The extended portion1902of the post2212provides the proper mounting height from the base assembly for the LEDs. In the preferred structure, mounting posts of different heights are used for LEDs of different colors in order to establish the correct focal distance for the LEDs of each color. In the side view ofFIG. 20, four rows2004,2005,2006and2007of mounted LEDs are shown. In the preferred application, the upper two rows of LEDs2004and2005are preferably illuminated for both low and high beam operation and the lower two rows of LEDs2006and2007are preferably illuminated for high beam operation only. In the front view ofFIG. 21, cylindrical portion2107showing in profile view at the base of the LED post assembly is pressed into a mating hole in the conducting base assembly ofFIG. 16. A beveled edge2102facilitates the press fit operation. Flat surfaces2106shown in profile view provide a pair of annular openings between the hole into which the post is pressed and the mounting post. These facilitate filling of the cavity around the LEDs and provide an opening to accommodate expansion differences between the volume of the cavity and the fill material.

It should be understood that the above description taken in combination with the accompanying figures is not intended to limit the scope of the invention in any regard. The appended claims shall be construed to include all equivalent structures and functions within the scope.