Thin LED flash for camera
A thin flash module for a camera uses a flexible circuit as a support surface. A blue GaN-based flip chip LED die is mounted on the flex circuit. The LED die has a thick transparent substrate forming a “top” exit window so at least 40% of the light emitted from the die is side light. A phosphor layer conformally coats the die and a top surface of the flex circuit. A stamped reflector having a knife edge rectangular opening surrounds the die. Curved surfaces extending from the opening reflect the light from the side surfaces to form a generally rectangular beam. A generally rectangular lens is affixed to the top of the reflector. The lens has a generally rectangular convex surface extending toward the die, wherein a beam of light emitted from the lens has a generally rectangular shape corresponding to an aspect ratio of the camera's field of view.
1. A light emitting device comprising:
a support structure;
a light emitting diode (LED) die mounted on the support structure,
the LED die having a top surface and at least one side surface and comprising LED semiconductor layers and a transparent substrate, the substrate comprising the top surface of the LED die so that the LED die has anode and cathode electrodes on a bottom surface, the substrate being thicker than the LED semiconductor layers, wherein light emitted from the side surfaces is at least 30% of all light emitted by the LED;
a phosphor layer covering the top surface and side surfaces;
a reflector surrounding the LED die, the reflector having curved surfaces surrounding the LED die, wherein the curved surfaces extend from a generally rectangular opening for the LED die and reflect the light from the side surfaces of the LED die to form a generally rectangular beam; and
a generally rectangular lens affixed to walls of the reflector, the lens having a generally rectangular convex surface extending toward the LED die and a flat top surface facing away from the LED die.
2. The device of claim 1 , wherein the device is a flash for a camera.
3. The device of claim 2 , wherein an aspect ratio of the beam is substantially the same as an aspect ratio of a field of view of the camera.
4. The device of claim 1 , wherein the support structure is a flexible circuit.
5. The device of claim 1 , wherein the reflector comprises a stamped metal reflector, where the opening has a knife edge facing the LED die.
6. The device of claim 1 , wherein the lens has a focal length and wherein a distance from a side of the LED die, taken normal to the side of the LED die, to the reflector plus a distance from the reflector to the lens is approximately the focal length.
7. The device of claim 1 , wherein light from the at least one side surface of the LED die is at least 40% of all light emitted by the LED die.
8. The device of claim 1 , wherein light from the at least one side surface of the LED die is at least 50% of all light emitted by the LED die.
9. The device of claim 1 , wherein the substrate is a growth substrate for the LED semiconductor layers.
10. The device of claim 1 , wherein the phosphor layer conformally coats the top surface and the at least one side surface and has substantially uniform thickness.
11. The device of claim 1 , wherein the phosphor layer comprises phosphor particles infused in a binder, wherein the phosphor layer covers a portion of a top surface of the support structure, and wherein a bottom surface of the reflector is affixed to the support structure by the binder acting as an adhesive.
12. The device of claim 1 , wherein a footprint of the reflector is substantially the same as a footprint of the support structure.
13. The device of claim 1 , wherein a total height of the device is less than 1 mm.
14. The device of claim 1 , wherein a total height of the device is less than 2 mm.