Encapsulated light emitting diode and method for encapsulation

• US 5,122,943 A
• Filed: 04/15/1991
• Issued: 06/16/1992
• Est. Priority Date: 04/15/1991
• Status: Expired due to Fees

• Current Assignee: Miles Incorporated Elkhart Indiana
• Original Assignee: Miles, Inc. (Bayer AG)
• Inventors: Pugh, Jerry T.
• Primary Examiner(s): Lazarus, Ira S.
• Application Number:
  US07/684,833
• Time in Patent Office: 428 Days
• Field of Search: 362/363, 362/242, 362/248, 362/800, 362/255, 362/256
• US Class Current: 362/256
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A light emitting diode with reduced stray light includes a base with an active light emitting element mounted in the base. An epoxy envelope is mounted on the base. The envelope includes a conical side portion and a spherical dome portion. The envelope is encapsulated with optically absorbing material of low reflectivity. The optically absorbing material is in direct contact with the side portion of the envelope and part of the spherical dome portion leaving an exposed portion through which rays of light pass. The diameter d of the exposed portion is equal to: 2r[sin (x+arcsin (r/s/n))], wherein r is the radius of a spherical dome portion, x<arcsin (1/n) is the maximum angle between a surface normal and a ray emitted from the active light emitting element that strikes the envelope at the edge of the exposed portion of the spherical dome portion, s is the distance between the active light emitting element and the center of the spherical dome portion, and n is the index of refraction of the material of the epoxy envelope.

Claims

1. An encapsulated light emitting diode, comprising:

an LED lamp, an active light emitting element in said LED lamp, said LED lamp including an envelope;

said envelope including a side portion, and a spherical end; and

encapsulating material covering said side portion;

wherein said encapsulating material is black.

2. An encapsulated light emitting diode, comprising:

an LED lamp, an active light emitting element in said LED lamp, said LED lamp including an envelope;

said envelope including a side portion, and a spherical end; and

encapsulating material covering said side portion;

wherein said encapsulating material further covers at least part of said spherical end leaving an exposed diameter portion having a diameter equal to 2r [sin(x+arcsin(r/s/n))]wherein r is the radius of said spherical end, x<

arcsin (1/n) is the maximum angle between a surface normal and a ray emitted from the active light emitting element that strikes the envelope at an edge of the exposed portion of the spherical end, s is the distance between the active light emitting element in said LED lamp and the center of the spherical end, and n is the index of refraction of the material of said envelope.

3. A light emitting diode encapsulated for reduced stray light, comprising:

a base,

an active light emitting element mounted on said base;

an envelope with a conical side portion, said conical side portion mounted on said base;

said envelope including a spherical dome end extending from said conical side portion; and

encapsulating material surrounding said conical side portion and part of said spherical dome end with an exposed portion of said spherical dome end uncovered by said encapsulating material;

wherein the diameter of the exposed portion of said spherical dome is equal to 2r[sin (x+arcsin (r/s/n))] wherein r is the radius of said spherical dome end, x<

arcsin (1/n) is the maximum angle between a surface normal and a ray emitted from the active light emitting element that strikes the envelope at the edge of the exposed portion of the spherical dome, s is the distance between said active light emitting element and the center of said spherical dome end, and n is the index of refraction of the material of said envelope.

4. A light emitting diode encapsulated for reduced stray light, comprising:

a base,

an active light emitting element mounted on said base;

an envelope with a conical side portion, said conical side portion mounted on said base;

said envelope including a spherical dome end extending from said conical side portion; and

encapsulating material surrounding said conical side portion and part of said spherical dome end with an exposed portion of said spherical dome end uncovered by said encapsulating material;

wherein said encapsulating material is in contact with said conical side portion and part of said spherical dome end.

5. An encapsulated light emitting diode, comprising:

a light emitting diode in an envelope having a side portion and an end portion, and

an encapsulating material covering said side portion;

wherein said encapsulating material is an optically absorbing material which absorbs class, 2, class 3 and class 4 rays emitted from said light emitting diode.

6. A method of reducing stray light emitted from a light emitting diode wherein said light emitting diode includes an active light emitting element mounted within an envelope including a side portion and a spherical end portion, the method comprising the steps of:

encapsulating said side portion of said envelope with material of low reflectivity;

encapsulating a portion of said spherical end portion of said envelope with said material of low reflectivity leaving an exposed portion; and

applying the material of low reflectivity in direct physical contact with said side portion and said spherical end portion.

7. A method of reducing stray light emitted from a light emitting diode wherein said light emitting diode includes an active light emitting element mounted within an envelope including a side portion and a spherical end portion, the method comprising the steps of:

encapsulating said side portion of said envelope with material of low reflectivity; and

encapsulating a portion of said spherical end portion of said envelope with said material of low reflectivity leaving an exposed portion;

wherein the step of encapsulating a portion of the spherical end portion of said envelope further includes leaving said exposed portion with a diameter equal to 2r [sin (x+arcsin (r/s/n))] wherein r is the radius of the spherical end portion, x<

arcsin (1/n) is the maximum angle between a surface normal and a ray emitted from the active light emitting element that strikes the envelope at the edge of the exposed portion of said spherical end portion, s is the distance between the active light emitting element and the center of the spherical end portion, and n is the index of refraction of the envelope.

8. A method of reducing stray light exiting an envelope of a light emitting diode wherein said envelope includes a side portion and a dome portion and said light emitting diode includes an active light emitting element mounted within said envelope, the method comprising the steps of:

absorbing rays of light emitted from said active light emitting element and refracted by said side portion of said light emitting diode envelope, and

lowering the internal reflectance of said envelope;

wherein said steps of absorbing rays of light emitted by an active light emitting element and lowering the internal reflectance include encapsulating said side portion of said envelope and part of said dome portion of said envelope with an optically absorbing material leaving an exposed portion of said dome portion, the diameter of said exposed portion being equal to 2r [sin (x+arcsin (r/s/n))] wherein r is the radius of said dome portion, x<

arcsin (1/n) is the maximum angle between a surface normal and a ray emitted from the active light emitting element that strikes the envelope at the edge of the exposed portion of the dome portion, s is the distance between said active light emitting element and the center of said dome portion, and n is the index of refraction of said envelope.