Thin wall internal reflection light optic

An example lamp optic comprises a light guide (100) to receive light from a light source (108) and generate a light beam via internal reflection. The light guide includes a proximal end (104) to receive the light and a distal end (106) to emit the light beam. An optical axis (OA) extends from the proximal end to the distal end, and a transverse axis (TA) extends perpendicular to the optical axis. A surface of the distal end has a stepped portion (110) including a central surface (112) substantially parallel to the transverse axis and centered on the optical axis, and linear steps (114) extending in opposing directions from the central surface parallel to the transverse axis and along the optical access towards the distal end. Each linear step includes an optical face (116) extending perpendicular to the optical axis and a transverse face (118) extending perpendicular to the transverse axis.

TECHNICAL FIELD

The present disclosure relates to lamps comprising at least one light source and a light guide having glare-reducing features that may be applicable to, for example, vehicular lighting.

BACKGROUND

At least one area of concentration for electronic technology development is designing products that operate with increased efficiency, reliability, etc. over longer periods of time. For example, at least one area of development where this trend is highly visible is lighting. Existing incandescent bulb technology is quickly being replaced by compact fluorescent lamp (CFL) and light emitting diode (LED)-based light sources. CFL and LED-based light sources may perform better (e.g., with higher efficiency) and may comprise longer lifetimes than existing incandescent light sources. As a result, many applications are transitioning to these new lighting technologies.

An example application in which LED-based lighting is utilized is in vehicular lighting. For example, automotive lighting such as headlights benefit from the long life, efficiency and reliability of LEDs. LEDs typically do not emit light in a manner focused enough to generate a headlight beam, and thus a light guide may be employed to generate a beam based on the light produced by at least one LED. Total internal reflection (TIR) may be used to very efficiently reflect light generated by the at least one LED light source internally within the light guide to focus the light into a light beam usable as a headlight. Solid TIR light guides operate with high efficiency, but are hard to manufacture (e.g., mold) as the size of the light device (e.g., headlight) increases. Orbital thin wall TIR light guides such as illustrated in U.S. Pat. No. 8,068,288 B1 (Pitou) are easier to manufacture than solid TIR light guides. However, thin wall TIR light guides generate extensive unfocused peripheral light (e.g., glare) that may obstruct the vision of a driver at night.

SUMMARY

In a least one embodiment, a lamp optic comprises at least a light guide to receive light from a light source and generate a light beam using the received light. The light guide generates the light beam via internal reflection (e.g., TIR). The light guide includes a proximal end to receive the light and a distal end to emit the light beam. An optical axis extends from the proximal end to the distal end, and a transverse axis extends perpendicular to the optical axis. A surface of the distal end has a stepped portion formed therein, the stepped portion including a central surface substantially parallel to the transverse axis and centered on the optical axis, and linear steps extending in opposing directions from the central surface parallel to the transverse axis and along the optical access towards the distal end. Each linear step includes an optical face extending perpendicular to the optical axis and a transverse face extending perpendicular to the transverse axis. Other example configurations that will be disclosed herein may include, but are not limited to, changes in the configuration of light guide regarding a lateral surface, step angle, optical face, etc.

This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the subject matter. The detailed description is included to provide further information about the present patent application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS INCLUDING BEST MODE

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It may be evident, however, to one skilled in the art, that the subject matter of the present disclosure may be practiced without these specific details. Moreover, technologies, structures, terms of art such as “total internal reflection,” etc. may be referenced herein to provide a readily comprehensible perspective from which the more general teachings of the disclosure may be understood. These references are merely explanatory, and are not intended to limit embodiments consistent with the present disclosure to a particular manner of implementation. Other implementations consistent with the present disclosure are possible without departing from the teachings disclosed herein.

FIG. 1illustrates a first example light guide100from various directions consistent with the present disclosure. In general, as opposed to existing light guide geometries, the light guide100comprises linear steps114that substantially reduce the amount of glare experienced along vertical axis (VA). This reduction in vertical glare is especially valuable in applications such as automotive headlights where the glare may obstruct the vision of drivers when driving at night. Any of the example light guides disclosed herein are formed from a material that is transparent in the visible portion of the spectrum, such as from glass or plastics. Examples of usable materials may include, but are not limited to, polycarbonate, acrylic, silicone, etc. In particular, any of the example light guides disclosed herein may be formed from polymethyl methacrylate (PMMA) or MAKRALON® 2245 brand polycarbonate plastics material from Bayer Material Science. Any of the example light guides disclosed herein may be formed by molding, grinding and polishing (e.g., performed alone or in combination), or through another suitable manufacturing process.

Light guide100is shown inFIG. 1from a first side view102, a front view126, a perspective view128and a second side view130. In first side view102, the optical axis OA extends vertically and the transverse axis TA runs horizontally. Proximal end104of the first example light guide100comprises a recess120to receive light source108. The light source108preferably includes at least one LED, but other embodiments may include, for example, an incandescent light source, a fluorescent light source, a gas-discharge light source (e.g., a sodium-vapor lamp), etc. At least a light emitting portion of light source108is inserted into the recess120, which is configured to receive light emission from all directions. In at least one embodiment, the recess120includes a lens122formed into an upper surface to, for example, control how light generated by the light source108is focused for light beam forming.

The distal end106comprises at least a stepped portion110formed therein. Light from light108that is internally reflected within the first example light guide100may exit as a light beam from at least the stepped portion110. The stepped portion110comprises central surface112and a plurality of linear steps114(an example of which is shown at114inFIG. 1). Each linear step114includes an optical face116and a traverse face118. When both the optical face116and the transverse face118are planar, they are also orthogonal to each other. The size of the optical face116and the transverse face118may vary based on a number of factors. For example, the size of the optical face116and the transverse face118may be selected based on the size of first example light guide100, the desired optical characteristics of first example light guide100(e.g., beam size, shape, intensity, etc.), the manufacturing limitations of example light guide100(e.g., molding requirements such as minimum mold/material feature tolerances, fillet radius, etc.), the desired mechanical characteristics of the first example light guide100(e.g., resistance to mechanical wear, temperature and other environmental stresses, etc.), etc.

The first example light guide100also includes lateral surface124. Lateral surface124covers the exterior of first example light guide100. The front view126of first example light guide100includes the TA and a vertical axis (VA) perpendicular to the TA. The front view demonstrates the relationship of the optical faces116to the central surface112and how the length of steps114is linear (e.g., that steps114are linear steps) and parallel to the VA. The perspective view128of the first example light guide100also demonstrates these relationships. The second side view130of the first example light guide100illustrates an alternative example view of the transverse face118, the recess120and the lateral surface124.

FIG. 2illustrates a second example light guide200from various directions consistent with the present disclosure. Item numbers corresponding to the same or similar features in the drawing figures are maintained the same throughout the figures to show correspondence between these features in different embodiments. In general, the second example light guide200may be similar to the first example light guide100except that the lateral surface120may comprise at least two planar portions204.

FIG. 2illustrates second example light guide200from a first side view202, a front view206, a perspective view208and a second side view210. In first side view202the planar portion is shown at204. The amount that the first example light guide100is “cut down” (e.g., the amount of material that is removed from the first example light guide100with respect to at least the planar portions204) depends on, for example, the particular application for which second light guide200is intended. For example, in a vehicular application it may depend on whether the second example light guide200is for a headlight, a fog light, a side illumination light, the type/size/height of the vehicle in which second example light guide200will be installed, etc. The planar portions204are seen in greater clarity in the front view206, the perspective view208and the second side view210. In at least one embodiment, the second example light guide may comprise two planar portions204located on opposing sides of the second example light guide200, wherein the two planar portions204are perpendicular to VA.

FIG. 3illustrates a third example light guide from various directions consistent with the present disclosure. A third example light guide300is based on the second example light guide200illustrated inFIG. 2except that at least one outermost linear step304(e.g., draft wall) may be angled with respect to VA. Angling the outermost linear step304alters the light beam emitted by the third example light guide300to comply with headlight light output regulations in some jurisdictions. For example, European automobile headlight light emission requirements are controlled by the United Nations Economic Mission for Europe (ECE, having a website located at www.unece.org), which stipulates in ECE Regulation No. 112 that the curb side of a headlight must emit a light beam that is extended or curved to form an emission pattern different than what is now required in the United States. The light beam emission of the third example light guide200achieves this requirement via the implementation of the angled outermost linear step304.

FIG. 3illustrates the third example light guide from a front view302and a perspective view306. In the front view302, the outermost linear step is set at an angle θ from VA. In at least one embodiment the angle θ may be 15 degrees. When the third example light guide300is employed as a vehicular headlight, light focused on the angled outermost linear step304(e.g., redirected from light source108via TIR) may be directed at an angle to curve around the front of vehicle. This curvature of the emitted light beam may fulfill requirements such as those set forth in ECE rule112regarding the required performance of vehicular headlights in Europe.

FIG. 4illustrates a fourth example light guide400from various directions consistent with the present disclosure. The fourth example light guide400presents examples of modifications that may be made to surfaces of distal end106to control the characteristics of the emitted light beam. For example, surfaces previously shown as planar may be rounded (e.g., made convex or concave) or gradually stepped to change the size, shape or emission direction of the light beam.

FIG. 4illustrated the fourth example light guide400from a perspective view402and a second side view410. The perspective view402illustrates at404how the optical face116of one or more steps114may be rounded. Rounding the optical face116of one or more steps may cause the emitted light beam to spread out over distance. This same effect is realized by rounding at least a portion of central surface112as shown at406. Having the emitted light beam expand over distance may be beneficial in vehicular headlights in that a wider span in front of a driver may be illuminated, providing greater visibility. While the surfaces404and406are illustrated as convex, they could also be concave, rotated, slanted, etc. Moreover, the optical face116of the fourth example light guide400may be stepped along VA as shown at408in the perspective view402and in the second side view as shown at410. The stepped surface408controls how the light beam is emitted from fourth example light guide400. For example, the light beam emerges in a direction opposite of the direction in which the stepped surface extends. For example, as shown at408inFIG. 2if the stepped surface extends downwards along VA, then the light beam would be focused upward based on, for example, the degree of stepping in the surface as shown at408.

FIG. 5illustrates different types of light guide types and, based on simulations modeled by computer, corresponding isocandela plots that approximate light output from each of the different TIR light guide types consistent with the present disclosure. As mentioned above, different configurations of light guides may generate different types of beam emissions. InFIG. 5a conventional solid TIR light guide is illustrated at500, a conventional thin wall TIR light guide is illustrated at504, both of which are rotationally symmetric. Second example light guide200is also shown inFIG. 5representative of the various light guides consistent with the present disclosure. Isocandela plots are illustrated at502,506and510corresponding to the light guides at500,504and208, respectively. The isocandela plots approximate the luminous intensity of the emitted light beam over a certain area based on computer simulation. The purpose ofFIG. 5is to illustrate at least one benefit that is realized through light guide configurations consistent with the present disclosure.

Based on computer simulation, the prior art solid TIR light guide500has an isocandela plot as illustrated at502. The light beam emitted by the solid TIR light guide may be tightly constrained and have little or no glare as shown by the centralized disposition of the plot. However, as mentioned above it is difficult to manufacture the solid TIR light guide500, especially in larger sizes like those needed for vehicular headlights. The prior art thin wall TIR light guide504is much easier to manufacture than the solid TIR light guide500, but computer simulation demonstrates increased glare in all directions, as is evident in the isocandela plot506. While a constrained central beam portion is present similar to that of the simulation of the solid TIR light guide500, a substantial amount of unfocused light (e.g., glare) is evident surrounding the central beam portion (e.g., in the halo area identified by508). The vertical portions of the glare508are caused by portions of the orbital steps of thin wall TIR light guide504that rise above and fall below a bisecting horizontal axis of the thin wall TIR light guide504(e.g., all curved lens portions above and below horizontal). At least the vertical portions of the glare508are undesirable for vehicular headlights as the glare508can obstruct the view of drivers.

The weaknesses of thin wall TIR light guide504are overcome by the light guide208and other light guide configurations consistent with the present disclosure. As shown in the simulated isocandela plot510, at least the vertical and horizontal glare portions seen at508in isocandela plot506are now eliminated through at least the advent of the linear steps116(e.g., the missing portions of the glare508are highlighted as missing at512and514, respectively). While some horizontal portions of the glare508still exist, when used in vehicular headlight applications these portions of the glare508do not interrupt the vision of drivers. As a result, consistent with the present disclosure the benefits of thin wall TIR light guide manufacturing may be realized with substantially improved light beam emission performance (e.g., reduced vertical glare) when compared to existing thin wall TIR light guides such as illustrated at504.

The description of the invention and its applications as set forth herein is illustrative and is not intended to limit the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and practical alternatives to and equivalents of the various elements of the embodiments would be understood to those of ordinary skill in the art upon study of this patent document. These and other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

GLOSSARY: a non-limiting summary of above reference numerals100first example light guide102first side view of example light guide104proximal end of example light guide106distal end of example light guide108example light source110stepped portion of distal end112central surface of stepped portion114step of stepped portion116optical face of step118transverse face of step120recess formed in proximal end122lens formed in recess124lateral surface of example light guide126first side view of example light guide128perspective view of example light guide130second side view of example light guide200second example light guide202first side view of second example light guide204planar portion of lateral surface of second example light guide206first side view of second example light guide208perspective view of second example light guide210second side view of second example light guide300third example light guide302front view of third example light guide304angled version of outermost linear stepθ angle of outermost linear step306perspective view of third example light guide400fourth example light guide402perspective view of fourth example light guide404convex optical face in fourth example light guide406convex central surface in fourth example light guide408vertically stepped optical face410second side view of fourth example light guide500perspective view of example solid TIR light guide502isocandela plot of solid TIR light guide504perspective view of example orbital thin wall TIR light guide506isocandela plot of orbital thin wall TIR light guide508vertical glare portion of light emission510isocandela plot of second example light guide512upper eliminated glare portion in isocandela view514lower eliminated glare portion in isocandela view