A flashlight that can be adjusted to provide different size light patterns at a predefined distance from the light is disclosed. The light patterns are always in-focus thereby providing well defined and uniformly illuminated areas of light. The focusing mechanism utilizes stationary lenses and a movable lens to adjust the diameter of the light pattern without allowing the pattern to become out of focus.
1. A portable light generating device, comprising:
(a) a housing defining an opening therethrough and having at least one battery disposed therein;
(b) a light emitting element secured within the housing and electrically coupled to said battery via an electrical circuit;
(c) a light pipe extending from at least said light emitting element to the opening in said housing;
(d) a first stationary lens positioned within said light pipe between said light emitting element and the opening in said housing;
(e) a second stationary lens positioned within said light pipe, said second stationary lens located between said first stationary lens and the opening in said housing;
(f) an aperture defining component positioned within said light pipe between said second stationary lens and the opening in said housing; and
(g) a movable lens positioned between said aperture defining component and the opening in said housing, wherein the distance between the second stationary lens and the movable lens can be adjusted to sequentially project onto a surface, located at a predefined distance from said light generating device, at least a first in-focus pattern of light having a first diameter and a second in-focus pattern of light having a second diameter, wherein said first and second diameters are different.
2. The portable light generating device of claim 1 wherein said light pipe has a constant inside diameter.
3. The portable light generating device of claim 1 wherein said first stationary lens has a first convex surface, located on the side of said first stationary lens that is closest to said light source, and a second convex surface, located on the side of said first stationary lens that is furthest from said light source, said convex surfaces each having a surface radius, wherein the surface radius of said first convex surface is less than the surface radius of said second convex surface.
4. The portable light generating device of claim 1 wherein said second stationary lens has a first convex surface and a second convex surface, wherein said second stationary lens' convex surfaces have surface radii that are greater than said first stationary lens' surface radii.
5. The portable light generating device of claim 4 wherein the surface radii of said second stationary lens' first and second convex surfaces are the same.
6. The portable light generating device of claim 1 wherein said movable lens has a first convex surface and a second convex surface, said movable lens' convex surfaces each having a surface radius, wherein the surface radii of said movable lens' convex surfaces are greater than the surface radii of said second stationary lens' convex surfaces.
7. The portable light generating device of claim 1 wherein said aperture defining component comprises a circular aperture.
8. The portable light generating device of claim 1 comprises a base member to which said light emitting element is secured.
9. The portable light generating device of claim 8 wherein said light emitting element generates heat and said base member dissipates the heat.
10. The portable light generating device of claim 1 wherein said stationary lenses each comprise a planar portion having a uniform edge thickness and a centrally located portion having double convex surfaces, said double convex surfaces concentrically aligned with one another and defining a center thickness.
11. The portable light generating device of claim 10 wherein the ratio of said center thickness to said edge thickness is three or less.
12. The portable light generating device of claim 1 wherein said light emitting element is a light emitting diode.
13. The portable light generating device of claim 12 wherein said light emitting diode generates a light pattern having an angle of directivity of ±70° or less.
14. The portable light generating device of claim 1 wherein said electrical circuit comprises a switch.
15. The portable light generating device of claim 1 wherein the diameter of said first light pattern and the intensity of light in said first light pattern are inversely proportional to one another.
16. The portable light generating device of claim 1 , wherein the second stationary lens focuses light from the light emitting diode onto a focal point and said movable lens can be sequentially positioned within said light pipe between said second stationary lens and the focal point, at the focal point, and between the focal point and the opening in said housing.
17. The portable light generating device of claim 1 , wherein the ratio of said first diameter to said second diameter is at least 2.0:1.0 when the distance from the light generating device's opening and said surface is 1.5 m.
18. The portable light generating device of claim 17 , wherein said ratio is at least 3.0:1.0.