Thin Flash or Video Recording Light Using Low Profile Side Emitting LED

• US 20080308824A1
• Filed: 06/14/2007
• Published: 12/18/2008
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Harbers, Gerard, Epler, John, Shchekin, Oleg Borisovich, Bierhuizen, Serge, Eng, Gregory W.
• Granted Patent: US 9,046,634 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01L 2224/0554 External layer
• CPC Class Codes: H01L 2224/0555 Shape
• CPC Class Codes: H01L 2224/0556 Disposition
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05639 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/013 Alloys
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Very thin flash modules for cameras are described that do not appear as a point source of light to the illuminated subject. Therefore, the flash is less objectionable to the subject. In one embodiment, the light emitting surface area is about 5 mm×10 mm. Low profile, side-emitting LEDs optically coupled to solid light guides enable the flash module to be thinner than 2 mm. The flash module may also be continuously energized for video recording. The module is particularly useful for cell phone cameras and other thin cameras.

Claims

1. An illuminator in a camera for illuminating a subject comprising:

a side-emitting, non-lasing light emitting diode (LED), the LED comprising;

a first semiconductor layer of a first type;

a second semiconductor layer of a second type;

and active layer between the first semiconductor layer and the second semiconductor layer, the active layer having a major surface;

a first electrode in contact with the first semiconductor layer;

a second electrode in contact with the second semiconductor layer, the first electrode and the second electrode being on a first side of the LED so that the LED is a flip chip;

a reflector over a second side of the LED, substantially parallel to the major surface of the active layer, such that substantially all light impinging on the reflector is redirected back into the LED, the LED substantially only emitting light from its sides without the use of a side-emitting lens;

a light guide having a top surface through which light is emitted and having a reflective bottom surface, the light guide having at least one opening in which the side-emitting LED is positioned, whereby light emitted from the sides of the LED is optically coupled into the light guide; and

a driver electrically connected to the first electrode and the second electrode of the LED for supplying power to the LED to illuminate a subject for recording an image of the subject by the camera;

the LED and controller being mounted within a camera housing.

2. The illuminator of claim 1 wherein the camera is a still picture camera, and the driver is configured for controlling the LED to output a flash for taking a still picture of the subject.

3. The illuminator of claim 1 wherein the camera is a video camera, and the driver is configured for controlling the LED to continuously output light for taking a video recording of the subject.

4. The illuminator of claim 1 wherein the active layer and a bottom surface of the reflector are located even with or between a top surface plane and a bottom surface plane of the light guide.

5. The illuminator of claim 1 wherein the light guide has a thickness less than 2 mm.

6. The illuminator of claim 1 wherein the LED has a thickness less than 2 mm.

7. The illuminator of claim 1 wherein the LED further comprises a phosphor layer between the reflector and the second semiconductor layer.

8. The illuminator of claim 7 wherein the LED, including the phosphor layer, emits white light.

9. The illuminator of claim 1 wherein light emitting sides of the LED have a height less than 0.4 mm.

10. The illuminator of claim 1 wherein the active layer emits blue light.

11. The illuminator of claim 1 wherein the bottom surface of the light guide scatters light toward the top surface.

12. The illuminator of claim 1 wherein the top surface of the light guide has a light emitting surface area greater than 25 square millimeters.

13. The illuminator of claim 1 wherein the top surface of the light guide has a light emitting surface area greater than 50 square millimeters.

14. The illuminator of claim 1 wherein the illuminator is a flash module.

15. The illuminator of claim 1 wherein the reflector is attached to the remainder of the LED without an air gap.

16. The illuminator of claim 1 further comprising a plurality of side emitting LEDs in respective openings in the light guide.

17. The illuminator of claim 1 wherein the camera is a cell phone camera.