Lamp assembly having light source with luminance peak portion at one of the long sides of the light source

1. A lamp assembly including an illumination direction, comprising:

a light source including an LED element with an emission surface; and

a projection optical system for projecting an image of the light source in the illumination direction so that a desired light distribution pattern is formed on a virtual vertical screen disposed in front of the lamp assembly, wherein

the light source has a rectangular shape having long sides and short sides, and is configured to provide a luminance distribution on the emission surface such that a luminance peak portion is provided substantially at one of the long sides,

the lamp assembly is configured to project an image corresponding to the luminance peak portion toward a predetermined area in the desired light distribution pattern,

the LED element has a first long side and a second long side and includes

a rectangular substrate,

a rear surface electrode formed on one surface of the substrate,

a p electrode formed on a surface opposite to the one surface of the substrate, the p electrode configured to serve as a reflection electrode,

a p-type semiconductor layer deposited on the p electrode,

an active layer formed on the p-type semiconductor layer,

an n-type semiconductor layer formed on the active layer, and

an n electrode formed on a narrow region including the first long side of a surface of the n-type semiconductor layer and extending in a direction parallel to the first long side of the LED element, the LED element being of a vertical type, and wherein

the projection optical system is configured to project an image of the light source in the illumination direction as a plurality of light source images so that the image of the luminance peak portion corresponding to the n electrode is positioned on one side of the light distribution pattern, thereby forming the light distribution pattern for a headlamp including a cut-off line formed of the images of the luminance peak portions of the plurality of the light source images on a virtual vertical screen located a certain distance away from the lamp assembly in the illumination direction, and

a plurality of concave and/or convex structural units are formed on the surface of the n-type semiconductor layer so that a density of the structural units is increased from the second long side of the LED element toward the n electrode.

2. The lamp assembly according to claim 1 , wherein the light source further includes a wavelength conversion layer disposed so as to cover the emission surface, so that the light source emits light with a desired color by additive color mixture using light emitted from the LED element which passes through the wavelength conversion layer and light emitted from the wavelength conversion layer as a result of excitation of the wavelength conversion layer by light from the LED element.

3. The lamp assembly according to claim 1 , wherein the LED element further includes an additional n electrode connected to the n electrode, extending in the direction parallel to the first long side of the LED element and formed in a midway position between the first long side of the LED element and the second long side of the LED element on the surface of the n-type semiconductor layer.

4. The lamp assembly according to claim 2 , wherein the LED element further includes an additional n electrode connected to the n electrode, extending in the direction parallel to the first long side of the LED element and formed in a midway position between the first long side of the LED element and the second long side of the LED element on the surface of the n-type semiconductor layer.

5. The lamp assembly according to claim 1 , wherein the LED element further includes a plurality of additional n electrodes each connected to the n electrode and extending in the direction parallel to the first long side of the LED element and formed so that a distance between adjacent additional n electrodes is decreased from the second long side of the LED element toward the n electrode.

6. The lamp assembly according to claim 2 , wherein the LED element further includes a plurality of additional n electrodes each connected to the n electrode and extending in the direction parallel to the first long side of the LED element and formed so that a distance between adjacent additional n electrodes is decreased from the second long side of the LED element toward the n electrode.

7. The lamp assembly according to claim 1 , wherein the LED element further includes a plurality of additional n electrodes each connected to the n electrode and extending in the direction parallel to the first long side of the LED element, and

the p electrode includes a plurality of first reflectance electrodes extending in the direction parallel to the first long side of the LED element and a plurality of second reflectance electrodes extending in the direction parallel to the first long side of the LED element, the second reflectance electrode having a reflectance lower than the first reflectance electrode, the first reflectance electrodes and the second reflectance electrodes being formed alternately, the plurality of second reflectance electrodes being formed so that a distance between adjacent second reflectance electrodes is decreased from the n electrode toward the second long side of the LED element.

8. The lamp assembly according to claim 2 , wherein the LED element further includes a plurality of additional n electrodes each connected to the n electrode and extending in the direction parallel to the first long side of the LED element, and

the p electrode includes a plurality of first reflectance electrodes extending in the direction parallel to the first long side of the LED element and a plurality of second reflectance electrodes extending in the direction parallel to the first long side of the LED element, the second reflectance electrode having a reflectance lower than the first reflectance electrode, the first reflectance electrodes and the second reflectance electrodes being formed alternately, the plurality of second reflectance electrodes being formed so that a distance between adjacent second reflectance electrodes is decreased from the n electrode toward the second long side of the LED element.

9. The lamp assembly according to claim 1 , wherein the LED element further includes a plurality of first transparent conductive films formed on the surface of the n-type semiconductor layer and extending in the direction parallel to the first long side of the LED element and a second transparent conductive film covering the plurality of first transparent conductive films and the surface of the n-type semiconductor layer exposed between the first transparent conductive films, the second transparent conductive film having a refractive index lower than the first transparent conductive film, and wherein

portions where the first transparent conductive film and the second transparent conductive film overlap with each other have a dimension in a direction parallel to a short side of the LED element so that the dimension is increased away from the second long side of the LED element toward the n electrode.

10. The lamp assembly according to claim 2 , wherein the LED element further includes a plurality of first transparent conductive films formed on the surface of the n-type semiconductor layer and extending in the direction parallel to the first long side of the LED element and a second transparent conductive film covering the plurality of first transparent conductive films and the surface of the n-type semiconductor layer exposed between the first transparent conductive films, the second transparent conductive film having a refractive index lower than the first transparent conductive film, and wherein

portions where the first transparent conductive film and the second transparent conductive film overlap with each other have a dimension in a direction parallel to a short side so that the dimension is increased away from the second long side of the LED element toward the n electrode.

11. The lamp assembly according to claim 2 , wherein the additive color mixture produces white light, and the lamp assembly is configured for use with a vehicle.