Light emitting diode

• US 4,301,461 A
• Filed: 12/18/1979
• Issued: 11/17/1981
• Est. Priority Date: 12/22/1978
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Asano, Toshiaki
• Primary Examiner(s): Edlow, Martin H.
• Application Number:
  US06/104,846
• Time in Patent Office: 700 Days
• Field of Search: 357/17, 357/18, 357/30, 357/72, 250/552
• US Class Current: 257/98
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A light emitting diode (LED) having excellent directivity, which is provided with a light emitting surface formed by a PN-junction of a semiconductor body, and a dome of a transparent material formed on the light emitting surface. The external surface of the dome is made a light emitting window. This external surface is in a semi-spherical shape at least in its one part, and the light emitting surface is on the symmetrical axis of the semi-spherical surface. Further, the light emitting surface is disposed at a position displaced for a finite distance in the direction opposite to the light emitting direction with respect to the center of curvature of the semi-spherical surface. With such construction of the LED, light from the light emitting surface intensifies its directivity at the time of its emission from the external surface of the dome.

Claims

1. System for projecting light from a light emitting diode comprising:

(a) projection optical means having means defining an aperture for restricting the range of the direction of the light from the light emitting diode,

(b) a light emitting diode having a dome provided on a light emitting portion,

at least one part of the outer surface of said dome being of semi-spherical shape having a rotatory symmetrical axis, and said light emitting portion being disposed at a position displaced by a finite distance |d|(|d|>

0) in a direction opposite to said projection optical means from the center of curvature of said semi-spherical outer surface.

2. System according to claim 1, wherein the F-number of said projection optical means is larger than 2.5, and the radius r of said semi-spherical shape and the finite distance |d| satisfies the following conditions.

3. System according to claim 1, wherein the F-number of said projection optical means is larger than 1.4, and the radius r of said semi-spherical shape and the finite distance |d| satisfied the following conditions.