Patent Publication Number: US-8534879-B2

Title: LED unit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is related to two patent applications, having respective Ser. Nos. 13/278,109 and 13/277,237, both entitled “LED UNIT”, assigned to the same assignee, and disclosures of which are incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to LED (light emitting diode) units, and more particularly, to an LED unit having a lens. 
     2. Description of Related Art 
     Light emitting diodes (“LEDs”) are widely used as new types of light sources in various applications, such as road lamps, traffic lamps, tunnel lamps, resident lamps and so on. A lens is often used with an LED for collimating the light beams generated from the LED in a predetermined pattern. For LED products designed to illuminate areas at a long distance, a convex lens may be used to converge the light beams emitted from the LED. However, in other applications, such as vehicle headlamps, the LED products need to be able to provide illuminations not only to the area far away from the LED, but also the area near the LED. LED products with the conventional convex lens may not meet such requirements. 
     What is needed, therefore, is an LED unit which may overcome the deficiencies as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an isometric view of an LED unit in accordance with an embodiment of the present disclosure. 
         FIG. 2  is a cross sectional view of the LED unit taken along line II-II of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIG. 1 , an LED unit  100  in accordance with an embodiment of the present disclosure is shown. The LED unit  100  may be applied in vehicle headlamps or other suitable products where the areas both near and remote from the LED unit  100  are required to be illuminated. The LED unit  100  includes a lens  20  on the light emitting side of an LED  10 . 
     In one embodiment, the LED  10  generates white light. However, other types of LEDs which generate different light colors, may also be used in the LED unit  100 . The lens  20  may be made of a transparent material such as epoxy, silicon, glass and so on. Referring to  FIG. 2 , the lens  20  may include a base  25 , a first member  22  and a second member  26  formed on a top face  250  of the base  25 . The base  25  may have a substantially disk shape. A bottom face of the base  25  may function as a light incident face  21  for transmitting light emitted from the LED  10  to the lens  20 . In the embodiment of the present disclosure, the light incident face  21  is a concave surface to diffuse light emitted from the LED  10  into the lens  20 . A top face  250  of the base  25  may be planar. 
     The first member  22  is a convex dome curves outward from the top face  250  of the base  25 . Circumferences of the first member  22  have diameters gradually decreasing outward from the top face  250  to a top of the convex doom. The first member  22  may converge a part of incident light from the light incident face  21  into narrow light beams to illuminate areas far away from the LED unit  100 . Preferably, the first member  22  has an optical axis O perpendicular to the top face  250  of the base  25 . The LED  10  may be placed on the axis O and on the concave side of the lens  20  so that the light emitted by the LED  10  may be collimated by the first member  22  to parallel light beams emitted out of the LED unit  100 . An outer face of the first member  22  may function as a first light emergent face  220  for transmitting the light out of the lens  20 . 
     The second member  26  is connected with the first member  22 . A continuous annular lateral face  28  comprises a sidewall of the second member  26  and a sidewall of the first member  22 . The continuous annular lateral face  28  is connected to the top face  250  of the base  25 . The continuous annular lateral face  28  has a largest height where the second member  26  and the first member  22  join. The second member  26  has an inclined top face with a flat surface finish. The inclined top face of the second member  26  may function as a second light emergent face  23  to direct light from the LED to illuminate areas near the LED unit  100 . The convex doom of the first member  22  is intersected by a third light emergent face  24 , which is connected to the second member  26 . The third light emergent face  24  is bordered by a curved top edge  240  and a straight bottom edge  242 . The third light emergent face  24  is connected to the second light emergent face  23  at the straight bottom edge  242 , and connected to the first light emergent face  220  at a curved top edge  240 . The third light emergent face  24  has a surface area less than a surface area of the second light emergent face  23 , and the surface area of second light emergent face  23  is much smaller than a surface area of the first light emergent face  220 . The third light emergent face  24  is at an angle α from the top surface  250  of the base  25 , wherein the angle α is equal to or less than 90 degrees. The third light emergent face  24  has a rough surface finish which may be formed by a plurality of parallel saws. The third light emergent face  24 , together with the second light emergent face  23 , may uniformly diffuse light from the light incident face  21  to provide even better illuminations to areas near the LED unit  100 . The second light emergent face  23  is at an angle β from the top face  250 , wherein the angle β is smaller than the angle α. An angle γ between the second light emergent face  23  and the third light emergent face  24 , measured facing the LED  10 , is between 180 degrees and 270 degrees. 
     When the LED unit  100  is applied to a headlamp of a vehicle, light emitted from the first light emergent face  220  may form a high beam to illuminate areas far away from the vehicle; whereas light emitted from the second light emergent face  23  and the third light emergent face  24  may form a low beam to illuminate areas near the vehicle. As a result, areas in front of the vehicle may have a better visibility. 
     It is believed that the present disclosure and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the present disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments.