LED package with a rounded square lens
View Patent ↗A rounded square lens is used instead of a hemispherical lens in an LED package to produce a substantially Lambertian light emission pattern. A cross-sectional view of the rounded square lens cut along its diagonal forms a semicircular surface so as to emulate a hemispherical lens in areas close to the diagonal. A cross-sectional view of the lens cut along its width bisecting the lens forms a bullet shaped surface narrower than the semicircular surface but having the same height as the semicircular surface. The four corners of the lens are rounded. The surface of the lens smoothly transitions between the two surface shapes. Since the rounded square lens has a diagonal dimension larger than a maximum allowable diameter of a hemispherical lens in the same package body, a larger LED die may be used with the rounded square lens to output more light without increasing the size of the package while maintaining a Lambertian emission.
1. A light emitting diode (LED) device comprising:
an LED die having a light emitting top surface;
a package containing the LED die, the package comprising a body and electrodes connected to the LED die; and
a rounded rectangular lens mounted on the body,
the lens having rounded corners in a plane that is parallel to the top surface,
the lens having a substantially semicircular surface along a diagonal cross-section of the lens that is orthogonal to the top surface, the diagonal cross-section of the lens having a first total width that is less than a total diagonal cross-section width of the body, the substantially semicircular surface having a maximum height H substantially above a centerpoint of the top surface of the LED die,
the lens having a non-semicircular bullet shaped surface along a width cross-section of the lens that is orthogonal to the top surface, bisecting the lens, the bullet shaped surface having a second total width smaller than the first total width, the bullet shaped surface having a maximum height H above the top surface of the LED die coinciding with the maximum height H of the substantially semicircular surface,
a surface of the lens smoothly transitioning between the substantially semicircular surface and the non-semicircular bullet shaped surface with no sharp corners above the top surface of the LED die,
wherein the lens produces a substantially Lambertian light emission pattern when the LED die is energized.
2. The LED device of claim 1 wherein the rounded rectangular lens is a rounded square lens.
3. The LED device of claim 2 wherein the LED die is substantially square, wherein corners of the LED die are sufficiently spaced from rounded corners of the lens so that there is substantially no total internal reflection (TIR) from the lens.
4. The LED device of claim 2 wherein the lens has a side-to-side width of about 2.5 mm, and the LED die has sides greater than 1 mm.
5. The LED device of claim 2 wherein a diagonal width of the lens is about 1.1-1.3 times a side-to-side width of the lens.
6. The LED device of claim 2 wherein the package body has a width of about 3 mm, and the LED die has sides greater than 1 mm.
7. The LED device of claim 2 wherein sides of the lens are straight.
8. The LED device of claim 2 wherein sides of the lens are bowed.
9. The LED device of claim 2 wherein the package body has a width of approximately 3mm, a side-to-side width of the lens is approximately 2.5 mm, a diagonal width of the lens is approximately 3 mm, and a height of the lens above the LED die is approximately 1.5 mm.
10. The LED device of claim 9 wherein the LED die has sides of greater than 1.3 mm.
11. The LED device of claim 10 wherein the LED die has sides of approximately 1.4 mm.