LED lens array optic with a highly uniform illumination pattern
An LED (light emitting diode) illumination device that can generate a uniform light output illumination pattern. The illumination source includes an array of LEDs. Forward of the LEDs is an array of negative lens surfaces. At a distance from the LED the width W of the lens and the spacing D between the LEDs enhances creating the uniform light output illumination pattern. The negative lens surface can be non-symmetric and take a conic or conic-like shape.
1. An illumination source comprising:
(a) an array of light emitting diodes (LEDs);
(b) an array of individual lens surfaces integrated together and positioned forward of the array of LEDs by a distance D, wherein D is the distance from the array of LEDs to a closest surface of the array of individual lens surfaces, the individual lens surfaces having a width W;
(c) wherein the individual lens surfaces are substantially negatively powered; and
(d) wherein the lens surfaces and array of LEDs satisfy W/D between 1.6 and 3.2,
wherein the individual lens surfaces include at least one surface curvature incorporating a positive lens portion contained to an angle of between about 0° and 10° as well as 0° and −10° with respect to optical axes of the LEDs.
2. An illumination source according to claim 1 , wherein optical axes of the LEDs are separated by a distance C, and the LEDs are positioned so that an average ratio (C−W/2)/D is between 2.8 and 3.8.
3. An illumination source according to claim 1 , wherein the individual substantially negative lens surfaces are non-symmetric and have two or more surface curvatures.
4. An illumination source according to claim 3 , wherein at least one surface curvature of the individual lens surfaces is a conic or conic-like shape.
5. An illumination source according to claim 1 , wherein the conic or conic-like shape of the lens surfaces has a shape selected from the group consisting of: a hyperbola; a parabola; an ellipse; a sphere; or a modified conic.
6. An illumination source according to claim 1 , wherein the array of individual lens surfaces are integrated into a first surface of a cover formed of plastic, wherein a second surface of the cover faces externally.
7. An illumination source according to claim 6 , wherein the plastic is polycarbonate, acrylic, or silicone.
8. An illumination source according to claim 1 , wherein the substantially negative powered individual lens surfaces form a conic or conic-like curve.
9. An illumination source according to claim 8 , wherein the conic or conic like curve satisfies the equation:
z
=
cr
2
1
+
1
-
(
1
+
k
)
c
2
r
2
r
2
=
x
2
+
y
2
,
in which x, y, and z are positions on a 3-axis system, k is conic constant, and c is curvature.
10. An illumination source according to claim 8 , wherein the conic or conic-like curve satisfies the equation:
z
=
cr
2
1
+
1
-
(
1
+
k
)
c
2
r
2
+
F
r
2
=
x
2
+
y
2
,
in which x, y, and z are positions on a 3-axis system, k is conic constant, c is curvature, and F is an arbitrary function.
11. An illumination source according to claim 8 , wherein said conic or conic-like curve is represented by a set of points and a basic curve or a spline fit, resulting in a conic-like shape.
12. An illumination source according to claim 1 , wherein the width W of the negative lenses is limited and does not redirect the LED light between 58 degrees and 90 degrees and −58 degrees and −90 degrees with respect to optical axes of the LEDs.
13. An illumination source according to claim 6 , wherein a reflector is positioned adjacent to the LED, wherein the reflector reflects LED light near 90 degrees and −90 degrees with respect to optical axes of the LEDs, wherein the reflected light is directed forward of the LEDs and through the cover.