Hewlett-Packard Company

Cheryl L McLeod

Frank Michael Steranka

George Edward Smith

Robert C Gardner

Dinesh C Shrimali

A lamp has a reflective cup with a light emitting device in the bottom of the cup. A transparent material having an index of refraction n fills the cup and extends to a hemispherical surface with radius R and an equator parallel to the opening of the cup. The reflective walls of the cup project substantially all of the light within a cutoff cone having an included half angle equal to the Brewster's angle of the transparent material. The center of the hemispherical lens surface is spaced from the rim of the opening of the cup a distance R/n. Thus, the opening of the cup is the locus of aplanatic points of the equator if the hemisphere. Most rays from within the cup are incident on the hemispherical lens surface at no more than the complement of the Brewster's angle. Thus, minimal light losses occur at the interface between the transparent medium and air. An aplanatic image is formed outside the hemispherical lens of a virtual source comprising a hemispherical surface extending through the rim of the cup opening. Such optics may also be used for a light accepting device. These principles may also be applicable to a an elongated cavity with a semicylindrical lens of radius R and edges spaced from the edge of the cavity a distance R/n.

High efficiency lamp or light accepter

A light-emitting diode is mounted in the bottom of a cavity in a metal lead and the assembly is potted in a transparent plastic material. The walls of the cavity surround the sides of the light-emitting diode in sufficiently close proximity to effectively shield the light-emitting diode from thermal expansion stresses from the plastic potting material which would induce light output degradation. Such a cavity may be a right-circular cylinder with a diameter less than 75 micrometers greater than the largest transverse dimension of the light-emitting diode. The front face of the light-emitting diode may be flush or beneath the face of the metal lead for minimizing stress. The cavity may be deep enough that the front face of the light-emitting diode is closer to the bottom of the cavity than to its open end. The front face may protrude beyond the open end of the cavity and be surrounded by a reflective surface. The edges of the front face of the light-emitting diode may be beveled for minimizing stress.

Growing community of inventors

Mountain View, CA, United States of America

Cheryl L McLeod