# Patent

## Title
Focusing lens system

## Abstract

A lens for a flashlight or other lighting unit provides for focusing light from a source, such as an LED, to provide a light beam adjustable between a spot beam and a wide beam. The lens includes a lens body with a front face, a rear LED-receiving well, and a side surface extending between the front face and the rear well. The front face includes a central surface surrounded by an annular concave surface. The rear well includes a space for the LED to be adjusted in position. The rear well space is defined by a concavely-curved sidewall and a concavely-curved base. The concave curvature of the sidewall and base may be Bezier curves.

## Background
FIELD OF THE INVENTION
The present invention relates to a lens for producing a beam of light from a light source, such as a light emitting diode (LED), in a flashlight or other lighting unit. The lens may be combined with an adjustment mechanism for varying the focus of the beam of light and may be housed in a structure supporting the lens, light source, and adjustment mechanism. Such structure may also include a power source, controls, interconnections, and electronics.
BACKGROUND OF THE INVENTION
Lenses for flashlights and other lighting units have been provided in a variety of forms, generally having in common a shape that is symmetrical about an axis along which the light is directed, i.e., the optical axis. Several such lenses have included a hole in a rear end of the lens adjacent a light source. Within the hole, the light source may be adjusted in position along the optical axis. Typically, adjusting the light source's position relative to the rear hole of the lens results in a varying light beam emerging from a front face of the lens. However, prior art lenses were limited in their capacity to combine a maximum intensity for a spot beam with a substantial uniformity for a wide beam.
Prior art lenses were also typically provided with a central convex lens surface on a front face combined with at least one additional convex surface where the light was either received into the lens, reflected within the lens, or emitted from the lens. The additional convex surface in the prior art may have been deemed necessary for a proper focusing of light from the source into a beam. Prior art lenses were alternatively provided with light-receiving, reflecting, and emitting surfaces that were flat as viewed in cross-section. Such flat surfaces were also likely deemed necessary for light-focusing or manufacturing purposes.
SUMMARY OF THE INVENTION
The lens system described in the present application provides a lens that may be combined with a light source and an adjustment mechanism. The lens system may be incorporated in a flashlight or other lighting unit and provide for focusing the light from the source. A light emitting diode or LED is a suitable source although other light sources, such as incandescent or fluorescent bulbs may be used. The light beam may be adjustable between a spot beam and a wide beam.
The lens may include a lens body with a front face, a rear LED-receiving void or well, and a side surface extending between the front face and the rear well. The front face includes a central surface surrounded by an annular concave surface. The rear well includes a space for the LED to be adjusted in position defined by a concavely-curved sidewall and a concavely-curved base. The concave curvature of the sidewall and base may be Bezier curves.
The lens system may include a housing structure built in two portions with an adjustment mechanism for moving one portion relative to the other. Typically the LED will be coupled to one portion of the housing and the lens coupled to the other.
The side surface of the lens body may define in cross-section an elliptical curve. The side surface is typically a light-reflecting surface, reflecting the light that strikes it from within the lens body. The side surface, viewed internally of the lens body as a reflector, typically defines in cross-section a concave curve. The side surface viewed from outside the lens body typically defines a convex curve.
The central surface of the lens body is typically convex and so includes a forwardmost point, typically at the center of the surface. The annular surface of the front face of the lens body may extend forward to a front rim that is farther forward than the forwardmost point of the central surface. The lens body may further include an outer, front rim defining a chamfer between the annular surface and the side surface.
The concave curves of the sidewall and base of the well may be Bezier curves, or use other curves. A rim may run around the rear well and the rear well adjacent the rear rim may be provided with a draft angle to facilitate removal from a mold.
A flashlight incorporating the lens system may include the housing structure in two portions, the adjustment mechanism, the LED and the lens. The body of the lens may include the side surface, the rear well, with the base and the sidewall, and the front face with the central and annular surfaces. Generally, in this lens body, the base and the sidewall are light-admitting surfaces, and the central surface and the annular surface of the front face are light-emitting surfaces, while the side surface is a light-reflecting surface. All of these surfaces may be concave, except typically the central surface is convex.
A lighting unit may include a power supply, such as batteries or an AC-DC converter with electronics to condition a voltage waveform compatible with the LED. For example, a pulse width modulator may be used to adjust the effective brightness of the LED.
The lens body is typically formed of solid, transparent material such as PMMA, molded or otherwise formed as a single piece for total internal reflection (TIR).



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of lens body for the lens system according to an embodiment of the present description.
FIG. 2 is a cross-sectional view of the lens body of FIG. 1 incorporating a light source that is adjustable in position along an optical axis.
FIGS. 3A-3D show the light refraction and reflection to form varying beams (3A wide beam to 3D spot beam) as the light source is moved in the rear well of the lens body.
FIG. 4 is an exploded cross-sectional view of the lens system with the two-portion housing structure, including a head portion with an outer profile providing a finger-grip portion and a body portion, with an adjustment mechanism, e.g., a slidable mount of the head portion on the body portion, allowing movement of the head portion relative to the body portion, and the LED in one portion and the lens in the other, and showing the lens held in position between a lip of a cap of the head portion by an internal nut.
FIG. 5 is a partial cross-sectional view of the assembled lens system showing the movement of the head portion relative to the body portion.
FIG. 6 is an end view of the lens system, showing a control switch and lanyard connection structure.
FIG. 7 is an external view of an embodiment of the lens system, with an outer profile for the head portion providing indentations on a finger-grip portion.
FIG. 8 is an external view of an embodiment of the lens system, with an outer profile for the head portion providing indentations and a button on a finger-grip portion.
FIG. 9 is an external view of an embodiment of the lens system, with an outer profile for the head portion providing indentations on a finger-grip portion.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a lens 10 for focusing light. Lens 10 may include a lens body 12 with a front face 14, a rear void, such as well 16, and a side surface 18 that extends between front face 14 and rear well 16. Front face 14 includes a central surface 20 surrounded by an annular surface 22 that may define in cross-section a concave curve. Rear well 16 defines a space 24 within which an LED or other light source may be adjusted in position (FIGS. 2, 3, and 5).
Well 16 is typically defined by a sidewall 26 and a base 28. Sidewall 26 preferably defines in cross-section, as shown in FIG. 1, a concave curve. Base 28 typically defines in cross-section a concave curve. Rear well 16 may include a rear rim 30, which as shown in FIG. 1, may be understood to define a reference line RL.
The shape of the concave curves in the base and sidewall may be any shape suitable for manufacture and use. The curve of sidewall 26 is typically a Bezier curve. A preferred Bezier curve for the sidewall of the rear well may include a first angle S1 adjacent the base of the well of about 74° relative to reference line RL and a second angle S2 adjacent the rear rim of the well of about 90° relative to the reference line with the angle of the curve varying therebetween in accordance with the standard for a Bezier curve.
The curve of base 28 may be substantially arcuate. A typical radius for such arcuate curve is no less than about 38-mm.
The curve of annular surface 22 of front face 14 is typically a Bezier curve. A preferred Bezier curve for annular surface 22 may include a first angle A1 adjacent a front rim 32 of front face 14 of about 48° relative to reference line RL and a second angle A2 adjacent central surface 20 of front face 14 of about 20° relative to reference line RL.
Side surface 18 of lens 10 typically defines in cross-section an elliptical curve, as shown in FIG. 1. Side surface 18 is ordinarily a light-reflecting surface. That is, it generally reflects light within lens body 12 (See, e.g., FIGS. 3C-3D). Side surface 18 may define in cross-section a curve that is concave with respect to the light that it reflects.
Central surface 20 is typically convex, defining a forwardmost point 34. Central surface 20 may incorporate various curvatures and a typical curvature is substantially arcuate with a radius of no more than about 7-mm.
The measurements of embodiments of the lens described herein are typical for a medium-sized lens system, such as one with an external diameter around the lens of about 1.25-inches. For smaller and larger lens systems, the measurements for the lens may be varied accordingly. As an example, lens 10 may in a large lens systems be at least about twice as large as the typical measurements provided herein.
Annular surface 22 of front face 14 of lens body 12 may extend forward to front rim 32. Typically front rim 32 is farther forward than forwardmost point 34 of central surface 20. Front or outer rim 32 may include a chamfer 35 between the annular surface and the side surface of at least about 1-mm of width. Chamfer 35 may have a width selected for a desired lens size and operational characteristics, and, as examples only, may be about 1.5-mm, about 1.6-mm, about 2.6-mm, or about 3.0-mm in width.
Lens 10 defines a width W that is the outer diameter at front rim 32 and a height H between rear rim 30 and front rim 32 or chamfer 35. Typically width W is between about 20-mm and about 50-mm, and, as examples only, may be about 20.7-mm, about 26.0-mm, about 39.0-mm, or about 46.6-mm.
Rear well 16 typically has an inner diameter at rear rim 30 of at least about 9-mm. Rear well 16 may have an inner diameter selected for a desired lens size and operational characteristics, and, as examples only, may be about 9.8-mm, about 12.6-mm, about 19.4-mm, or about 22.1-mm. Rear well 16 may be provided adjacent rear rim 30 with a draft angle of between about 2° and about 3° to ease removal of the mold parts from around the rear well.
As seen in FIG. 2, a light source, such as LED 36, is preferably adjustable in position along an optical axis OA, generally within rear well 16, from a typical starting position, shown in solid line, through intermediate positions, P1 and P2, to a final position, P3. The adjustment may be continuous or it may be provided with stops or detents at selected positions. Any range of position adjustments may be incorporated as suited to the particular lens size, design, and desired beam variations. Typically the range is about 5-mm to about 6-mm, and other examples of range include about 6.1-mm, about 6.8-mm, about 14.0-mm, or about 16.9-mm. LED 36 may be located at or below reference line RL at its rearmost position, or may start within rear well 16 above reference line RL. Typically rear well 16 is about 9-mm deep and other examples of depth include about 12.8-mm, about 15.9-mm, about 23.2-mm, or about 28.6-mm. LED 36 may be movable forward within the well to within about 3-mm to 5-mm of base 28, or to other limits as selected for desired operational characteristics of the lens system. In general, the concave curvatures of sidewall 26 and base 28 allow for increased movement and larger structure of the LED and its supporting structure within rear well 16 as compared to convex curvatures.
A preferred embodiment of a lens, e.g., for a medium-sized lens system, combine a lens width of about 20.7-mm, a height of about 12.8-mm, an inner diameter of about 9.8-mm, a chamfer width of about 1.6-mm, and a range of position adjustment of about 6.1-mm. Other combinations may be selected for desired operational characteristics. Typically such dimensions may be varied by at least about ±10%.
As best seen in FIGS. 3A-D, adjustment of the LED position relative to the lens provides a beam ranging between a wide beam (FIG. 3A) and a narrow or spot beam (FIG. 3D). A spot beam may provide about +/−4.3° of angular distribution at about 50% of maximum intensity. An example of a wide beam is about +/−20° of angular distribution at about 50% of maximum intensity. With the design of the present embodiment, the light may be varied from spot beam to wide beam with the adjustment in position of the LED being no more than about 5-mm. A representation of the light rays LR calculated for a typical lens and LED configuration is shown in each of FIGS. 3A-3D. As can be seen, lens 10 typically directs a substantial portion of light rays LR into the desired beam and a smaller portion of light rays LR may be expected to travel outside the desired beam.
A lens system 38, as shown in FIGS. 4-9, for focusing a light beam may include a housing structure 40 including a first portion, such as body 42, a second portion, such as head 44, and an adjustment mechanism 46 for moving the first portion relative to the second portion. Adjustment mechanism 46 is preferably a slidable mounting of head 44 onto body 42, or alternatively may be a threaded engagement between portions 42 and 44 or other suitable mechanism allowing a user to adjust the relative positions of the housing portions.
LED 36 may be coupled to body 42 of housing 40. Lens 10 may be coupled to head 44 of housing 40. A slidable mounting between the portions allows direct movement of head 44, while a threaded engagement between the portions allows rotating one portion relative to the other, in either case allowing a relative movement or adjustment in position RP (FIG. 5) of LED 36 and lens 10 to adjust the light beam between a spot beam and a wide beam.
LED 36 and lens 10 may combine to produce a diode image visible in the light beam. The present embodiment is believed to substantially reduce such diode image if the range of movement RP in adjusting the relative position of lens 10 and LED 36 is limited to no more than about 5-mm.
Lens system 38 of the present embodiment, with the adjustment mechanism as described may provide the light beam with a wide beam of at least about +/−20° of angular distribution at about 50% of a maximum intensity. For that wide beam, lens system 38 is believed to provide a substantially uniform intensity between at least about +/−10° of angular distribution. Lens system 40 is also believed to provide an increased intensity for the spot beam as compared to a similar lens incorporating one or more flat or convex surfaces among its rear well sidewall, rear well base, front annular surface, and/or side surface.
A flashlight 48 according to the present embodiment may include, as seen in FIGS. 4 and 5, the housing structure with the adjustment mechanism, LED, and lens as described above. Head 44 may include a cap 50 with an opening 52 defined by a lip 54 adjacent front rim 32 of lens 10. A bracket, such as internal nut 56 may be threadably engaged in cap 50 to hold lens 10 in place by pressing front rim 32 and/or chamfer 35 against lip 54. Typically, lip 54 overlaps front rim 32 and/or chamfer 35 by between about 0.5-mm and about 1.0-mm, or such overlap as selected for particular lens dimensions and desired application of the flashlight. Flashlight 48 may include a clear protective plate in front of lens 10 or the lens may provide the external surface. Typically electronics, batteries, and interconnections 58 are provided in body portion 42 of housing structure 40.
Body 42 may include a threaded engagement for receiving a mount 60 for LED 36. Head 44 may include a base portion 62 with a threaded engagement for attaching to cap 50. O-rings may be provided as desired to seal the threaded connections. Adjustment mechanism 46 may include an internal O-ring 64 mounted in head 44 that bears on an external surface 66 of body 42 as the position of the head is adjusted. Mount 60 of LED 36 may be provided with an O-ring 68 on which an internal surface 70 of head 44 bears as the position of the head is adjusted.
Head 44 is preferably provided with a grip-enhanced region, such as groove 72 and swell 74, typically extending around base portion 62. The grip-enhanced region aids a user, e.g., in a one-handed adjustment of the focus of the beam by providing a convenient grip for the thumb and forefinger on the head while the body is gripped by the other three fingers. Various other grip-enhanced regions may be provided, such as one or more indentations 76, as shown in FIGS. 7-9, on swell 74 or elsewhere on head 44. As shown in FIGS. 5-9, a control button 78 may be provided on flashlight body 42, e.g., at an end opposite the head. A button 80 (FIG. 8) may also be provided on head 44 for any purpose, such as control of adjustment of head position or other gripping or control purposes.
Housing structures may be made from a metal such as aluminum or steel or a plastic such as ABS. Component materials may be selected to be compatible with lighting unit operation in harsh environments such as very high or very low ambient temperatures.
Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention, except as it may be limited by the claims.
Applicants regard the subject matter of their invention to include all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed examples is essential to all examples. The following claims define certain combinations and subcombinations which are regarded as novel and non-obvious. Other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such claims, whether they are different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of applicants' invention.

## Claims

1. A lens system for focusing a light beam, the system comprising:
a housing structure including a first portion, a second portion, and an adjustment mechanism for moving the first portion relative to the second portion;
an LED coupled to the first portion of the housing; and
a lens coupled to the second portion of the housing, the lens including a lens body defining a front face, a rear-facing void for receiving the LED, and a side surface extending between the front face and the rear void, wherein the front face includes a central surface surrounded by an annular surface that defines in cross-section a concave curve, the rear void dimensioned to receive the LED, the void defined by a side wall and a base, wherein the sidewall and the base define in cross-section concave curves;
wherein the adjustment mechanism and lens provide for adjustment of the light beam between a spot beam and a wide beam.

2. The lens system of claim 1 wherein the lens defines an optical axis and the adjustment mechanism provides for a range of movement of no more than about 5-mm, along the optical axis, of the first portion of the housing relative to the second portion of the housing.

3. The lens system of claim 2 wherein the LED and the lens combine to produce a diode image, and further wherein the range of movement of no more than about 5-mm substantially reduces the diode image.

4. The lens system of claim 1 wherein the side surface of the lens body defines in cross-section an elliptical curve.

5. The lens system of claim 1 wherein the central surface of the lens body is convex.

6. The lens system of claim 1 wherein the annular surface of the front face of the lens body extends forward to a front rim and wherein the central surface defines a forwardmost point, and further wherein the front rim is farther forward than the forwardmost point of the central surface.

7. The lens system of claim 1 wherein the front face of the lens body further includes an outer rim defining a chamfer between the annular surface and the side surface.

8. The lens system of claim 7 wherein the chamfer has a width of no more than about 2-mm.

9. The lens system of claim 1 wherein the concave curve of the sidewall of the void is a Bezier curve.

10. The lens system of claim 9 wherein the rear end of the lens body includes a rear rim defining a reference line, and further wherein the Bezier curve of the sidewall of the rear void defines a first angle adjacent the base of the void of about 74° relative to the reference line and a second angle adjacent the rear rim of about 90° relative to the reference line.

11. The lens system of claim 1 wherein the concave curve of the annular surface of the front face is a Bezier curve.

12. The lens system of claim 11 wherein the rear end includes a rear rim defining a reference line and wherein the front face of the lens body includes a front rim, and further wherein the Bezier curve of the of the annular surface of the front face defines a first angle adjacent the front rim of about 48° relative to the reference line and a second angle adjacent the central surface of the front face of about 20° relative to the reference line.

13. The lens system of claim 1 wherein the rear end includes a rear rim and wherein the rear void at the rear rim has a diameter of at least about 10-mm.

14. The lens system of claim 1 wherein the rear end includes a rear rim and wherein the rear void adjacent the rear rim is provided with a draft angle of at least about 2°.

15. The lens system of claim 1 wherein a rear rim of the rear void is provided with a draft angle of no more than about 3°.

16. The lens system of claim 1 wherein the concave curve of the base of the rear void is substantially arcuate with a radius of no less than about 38-mm.

17. The lens system of claim 1 wherein the convex surface of the central surface of the front face is substantially arcuate with a radius of no more than about 7-mm.

18. The lens system of claim 1 wherein the adjustment mechanism may be set to provide the light beam with a wide beam of at least about +/−20° of angular distribution at about 50% of a maximum intensity, and wherein the wide beam provides a substantially uniform intensity between at least about +/−10° of angular distribution.

19. The lens system of claim 1 wherein the rear void is at least about 9-mm deep and the adjustment mechanism is limited to provide no more than about 5-mm of movement of the first housing portion relative to the second housing portion.

20. A lens for focusing light from an LED to provide a light beam, the lens comprising:
a lens body defining a front face, a rear LED-receiving well, and a side surface interconnecting the front face and the rear well, wherein the front face includes a central surface surrounded by an annular surface that defines in cross-section a concave curve,
further wherein the rear well defines a space within which the LED may be adjusted in position, the well defined by a sidewall and a base, wherein the sidewall and the base define in cross-section concave curves.

21. The lens of claim 20 wherein the lens provides the beam ranging from between about +/−4.3° of angular distribution and about +/−20° of angular distribution with the adjustment in position of the LED being no more than about 5-mm.

22. The lens of claim 20 wherein the side surface of the lens body defines in cross-section an elliptical curve.

23. The lens of claim 20 wherein the central surface of the lens body is convex.

24. The lens of claim 20 wherein the annular surface of the front face of the lens body extends forward to a front rim and wherein the central surface defines a forwardmost point, and further wherein the front rim is farther forward than the forwardmost point of the central surface.

25. The lens of claim 1 wherein the front face of the lens body further includes an outer rim defining a chamfer between the annular surface and the side surface.

26. The lens of claim 25 wherein the chamfer has a width of no more than about 1-mm.

27. The lens of claim 20 wherein the concave curve of the sidewall of the rear well is a Bezier curve.

28. The lens of claim 27 wherein the rear well includes a rear rim defining a reference line, and further wherein the Bezier curve of the sidewall of the rear well defines a first angle adjacent the base of the well of about 74° relative to the reference line and a second angle adjacent the rear rim of the well of about 90° relative to the reference line.

29. The lens of claim 20 wherein the concave curve of the annular surface of the front face is a Bezier curve.

30. The lens of claim 29 wherein the rear well includes a rear rim defining a reference line and wherein the front face of the lens body includes a front rim, and further wherein the Bezier curve of the of the annular surface of the front face defines a first angle adjacent the front rim of about 48° relative to the reference line and a second angle adjacent the central surface of the front face of about 20° relative to the reference line.

31. The lens of claim 20 wherein the rear well has a diameter at a rear rim of at least about 12-mm.

32. The lens of claim 20 wherein the rear end includes a rear rim and wherein the rear well adjacent the rear rim is provided with a draft angle of at least about 2°.

33. The lens of claim 20 wherein the rear end includes a rear rim and wherein the rear well adjacent the rear rim is provided with a draft angle of no more than about 3°.

34. The lens of claim 20 wherein the concave curve of the base of the rear well is substantially arcuate with a radius of no less than about 38-mm.

35. The lens of claim 20 wherein the convex surface of the central surface of the front face is substantially arcuate with a radius of no more than about 7-mm.

36. The lens of claim 20 wherein the side surface is a light-reflecting surface, the side surface defining in cross-section a curve that is concave with respect to the light that it reflects.

37. A flashlight with a lens system for focusing a light beam, the flashlight comprising:
a housing structure including a first portion, a second portion, and an adjustment mechanism for moving the first portion relative to the second portion, wherein a relative movement of the portions of the housing is between about 5-mm and about 6-mm;
an LED coupled to the first portion of the housing; and
a lens coupled to the second portion of the housing, the lens including a lens body defining a front face, a rear-facing void for receiving the LED, and a side surface extending between the front face and the rear void, wherein the front face includes a central surface surrounded by an annular surface that defines in cross-section a concave curve, the rear void dimensioned to receive the LED, the void defined by a side wall and a base, wherein the sidewall and the base define in cross-section concave curves, and
wherein the adjustment mechanism and lens provide for adjustment of the light beam between a wide beam of at least about +/−20° of angular distribution at about 50% of a maximum intensity and a spot beam of no more than about +/−5° of angular distribution at about 50% of the maximum intensity.

38. The flashlight of claim 37 wherein the second portion of the housing includes a grip-enhanced region.