WO2018129581A1

WO2018129581A1 - Lenses and apparatus including lenses

Info

Publication number: WO2018129581A1
Application number: PCT/AU2018/000003
Authority: WO
Inventors: Rolf Roald MEUMANN
Original assignee: Meumann Rolf Roald
Priority date: 2017-01-12
Filing date: 2018-01-12
Publication date: 2018-07-19

Abstract

Apparatus for adjusting the angle of divergence of a light beam said apparatus comprising a light source, a flexible transparent element mounted in front of said light source, and means for applying a pressure to said flexible element to thereby alter the shape of the flexible element to an extent corresponding to the amount of said pressure so applied.

Description

Lenses and Apparatus Including Lenses

This invention concerns optical lenses. There have been many lens systems suitable for the projection of light from a light source where the lens system may be easily adjusted to produce a narrow beam of light, such as in a spot-light, or a wide beam such as in a flood light. However such lens systems are notoriously inefficient in delivering the light to the intended place. Also, existing variable lens systems have been designed for light sources at a single point source, such as an incandescent light globe, and are inefficient for Light Emitting Diode (LED) light sources where the light is produced by a matrix of individual LEDs spaced across a significant area. Only one LED can be at the focus of a single lens. Each LED therefore requires its own lens for efficient control of the divergence of the beam. But there is difficulty in creating and controlling separate adjustable lenses for each LED.

An aim of the present invention is to provide a lens system, apparatus including lens systems, and methods of adjusting lens systems which overcome or at least reduce these difficulties.

The invention provides apparatus for adjusting the angle of divergence of a light beam said apparatus comprising a light source, a flexible transparent element mounted in front of said light source, and means for applying a pressure to said flexible element to thereby alter the shape of the flexible element to an extent corresponding to the amount of said pressure so applied.

Said flexible transparent element may comprise a pair of thin, clear elastomeric membranes with a substantially optically clear liquid filling a plenum space between said membranes. The apparatus may comprise means for controllably varying the pressure of said liquid in said plenum and thereby controlling the degree to which the liquid distends the membranes to form a convex lens and thereby alter said angle of divergence. Said membranes preferably have at least substantially the same refractive index as said liquid.

Each said LED may shine through its own respective Fresnel lens element and then through its own respective said flexible transparent element, whereby said light beam exiting said respective Fresnel lens element is divergent. Alternatively, each LED may shine through its own respective Fresnel lens element and then through its own respective said flexible transparent element, whereby said light beam exiting said respective Fresnel lens element is substantially parallel. Preferably a plurality of LEDs provide an array of said light sources with each said light source associated with its own respective said flexible transparent element.

The invention also provides a method of adjusting the angle of divergence of a light beam emanating from a light source, said method comprising applying a pressure to a flexible transparent element mounted in front of said light source, to thereby alter the shape of the flexible element to an extent corresponding to the amount of said pressure applied.

Said flexible transparent element may comprise a pair of thin, clear elastomeric membranes with a substantially optically clear liquid filling a plenum space between said membranes and the pressure of said liquid in said plenum is controllably varied to thereby vary the degree to which the liquid distends the membranes to form a convex lens and thereby alters said angle of divergence. Embodiments of the invention are described with reference to the following attached drawings:

Fig. 1 is a cutaway view of a flashlight according to a first embodiment of the invention having an array of seven LED light sources, Fig. 2 is an exploded view of the components shown in Fig. 1 ,

Fig. 3 is a thin-section through Fig. 1 showing the paths of light rays when the power is turned on and the flashlight's variable lens system is not activated,

Fig. 4 is a thin-section similar to Fig. 3 but with the lens system activated,

Fig. 5 is a cutaway view of some of the components in Fig. 3,

Fig. 6 is a thin-section showing the cutaway face in Fig. 5 together with the paths of light rays,

Fig. 7 is a cutaway view of some of the components in Fig. 4,

Fig. 8 is a thin-section showing the cutaway face in Fig. 7 together with the paths of light rays while the lens system is activated,

Fig. 9 is a cutaway view showing a variable lens system according to a second embodiment of the invention where the variable lens system is not activated, Fig. 10 is a thin-section showing the cutaway face in Fig. 9 together with the paths of light rays,

Fig. 11 is a cutaway view of the variable lens system in Fig.9 but where the variable lens system is activated,

Fig. 12 is a thin-section showing the cutaway face in Fig. 11 together with the paths of light rays,

Fig. 13 is an exploded view of a variable lens system according to a third

embodiment of the invention,

Fig. 14 is a thin-section view showing the assembled lens system shown in Fig. 13 where the variable lens system is not activated,

Fig. 15 is a thin-section of the system in Fig. 14 but with the lens system activated, Fig. 16 is a thin-section showing the face in Fig. 14 together with the paths of light rays when the variable lens system is not activated,

Fig. 17 is an enlargement of the portion marked "A" in Fig. 16,

Fig. 18 is a thin-section as in Fig. 6 but with the variable lens system activated to a first extent,

Fig. 19 is an enlargement of the portion marked "B" in Fig. 18,

Fig. 20 is a thin-section as in Fig. 18 but with the variable lens system activated to a second, greater, extent,

Fig. 21 is an enlargement of the portion marked "C" in Fig. 20, Fig. 22 is a thin-section as in Fig. 20 but with the variable lens system activated to a third, even greater, extent,

Fig. 23 is an enlargement of the portion marked "D" in Fig. 22,

Fig. 24 is an exploded view of a variable lens system according to a fourth

embodiment of the invention,

Fig. 25 is a thin-section view showing the assembled lens system in Fig. 24 where the variable lens system is activated,

Fig. 26 is a thin-section showing the face in Fig. 25 together with the paths of light rays while the variable lens system is activated, and

Fig. 27 is an enlargement of the portion marked Έ" in Fig. 26.

Figs. 1 to 4 show components of a flashlight 10. The main casing of the flashlight is not shown so as to more clearly illustrate the relationships between the components. The flashlight's illuminating source is an array 12 of seven LEDs 14 mounted on a printed circuit board (PCB) 15. A battery 18 and on-off switch 20 provide the power supply to the PCB. Six of the LEDs 16 are spaced hexagonally on the periphery of the array with the seventh LED 17 central to the others. The LEDs are equally spaced and can be considered as acting as individual separate point light sources.

Immediately in front of the LEDs is a Fresnel-type first fixed lens array 22 which provides separate circular lens elements 24 for each LED. The Fresnel lens array 22 is preferably made of a polymer material but may be glass. In front of the lens array 22 are, in order, a first lens spacer 25 (also called the rear lens spacer), a first flexible lens film 28 (also called the rear membrane), a lens film spacer seal 30, a second flexible lens film 32 (also called the front membrane), a second lens spacer 33 (also called the front lens spacer), and a protective flat lens cover 36. The first lens spacer, first flexible lens film, lens film spacer-seal, second flexible lens film, second lens spacer and protective flat lens cover are all clamped together by a retaining ring 38 which is crimped to permanently clamp those components together.

While the membranes are optically clear across their entire surface, the lens spacers 25 and 33 are thick components made of black plastic with holes formed through from face to face to provide lens apertures for the light to pass through. The rear lens spacer 25 includes six such holes creating lens apertures 26 aligned with the peripheral LEDs 16 plus a central hole creating a lens aperture 27 which is aligned with the central LED 17. The front lens spacer 33 includes six such holes creating lens apertures 34 aligned with the peripheral LEDs 16 and a central hole creating a lens aperture 35 which is aligned with the central LED 17.

The flexible lens films 28 and 32 are each a thin, clear elastomeric membrane. They are a rubbery material stretched under tension. The lens film spacer-seal keeps the films 28 and 32 separated. The lens plenum 40, formed by the spacer seal 30, between the films 28 and 32 is filled with an optically clear liquid having an appropriate refractive index the same as the refractive index of the films. The first lens spacer bears upon the rear face of the first film while the second lens spacer bears upon the front face of the second film.

In Fig. 3 the natural stasis of the rubbery films across the holes 26, 27, 34 and 35 provides an optically flat surface across the lens apertures.

The lens plenum 40 is connected by a tube 42 to a reservoir 44 of the optically clear liquid. The reservoir is in the form of a bladder which may be squeezed by depressing a two-finger hand grip 46 on a lever arm 48. The lever arm pivots from the flashlight's main casing (not shown) such that manually squeezing the hand grip squeezes the bladder 44 between the lever arm and the battery casing 50 which forces liquid from the bladder, through the tube into the lens plenum 40. This causes the elastomeric lens membranes 28 and 32 to distend into the holes 26, 27, 34 and 35 so they form parabolic curved surfaces 52 and 54 within those respective lens apertures. Each corresponding pair of curved surfaces 52 and 54 therefore forms a convex lens element 55 comprising the curved portions of membrane and the liquid between them, and bounded by the respective lens apertures. The lens elements 55 each have the same focal length which varies with the fluid pressure within the lens plenum 40. Filling and connection of the bladder to the plenum would preferably be done under vacuum conditions in order to preclude any inclusion of gases.

The parabolic shape is determined by how much fluid enters the lens plenum, the elasticity of the membranes and any thickness variations across the membranes. The membranes may be formed to have a different thickness in the regions of the lens apertures, and even a varying thickness across each aperture, so that a particularly desired parabolic shape is formed when the lens plenum is increased.

Figs. 3 and 6 show how, when the bladder is fully distended and the lens plenum is therefore unpressurized, light emanating from the central LED 17 is partially focused by its respective lens element 24 before passing essentially unrefracted through the flat-walled fluid-filled lens plenum 40 and the lens cover 36 to issue as a divergent beam 56 having a beam angle in the range 40° to 45°.

Figs. 4 and 8 show how, when the lens plenum is pressurized, the partially-focused light from the Fresnel lens element 24 is further focused by the lens element 55 to issue as an almost undivergent beam 58. The beam angle is in the range 6° to 8°. When the manual force on the lever arm 48 is released, the pressure is released from the bladder, the rubber membranes spring back to their flat stasis position and the light beam returns to its divergent beam angle as shown in Fig.3.

In a variation of this embodiment the light could be operated remotely where a device such as a servo in the assembly could be installed so as to press on the bladder, or provide some other pumping action, to transfer liquid to the lens plenum.

A further variation would be to have no bladder but instead have a fixed volume of fluid. In this variation, to create the adjustable parabolic lens elements, either one or both of the lens spacers are selectively moveable towards each other by way of some mechanical means (eg a screw thread) causing the flexible convex lens elements to inflate. Only a small movement of the lens element(s) would be required to achieve the desired effect. The embodiment illustrated by Figs 9 to 12 has most of its features in common with the variable lens system in the flashlight embodiment described above with reference to Figs. 1 to 8. The major difference is the Fresnel lens elements 124 have a more extreme shape and thus greater refracting power so that the light beam exiting from each Fresnel lens element 124 is roughly parallel. This means that when the lens plenum 140 is unpressurized, and the lens membranes 128 and 132 are therefore in their unbent state, the beam exiting the flashlight is roughly parallel. Furthermore, when the lens plenum is pressurized, and the lens membranes 128 and 132 are therefore distended, the beam exiting the flashlight is divergent because the light beams exiting each lens aperture 134 and 135 "cross over".

The cross over of the light seen in Fig. 12 allows for the use of a shroud (not shown) around the perimeter of the LED array equal to double the distance from where the light is emitted to where the crossover occurs. This would make the light

apparatus/lens system invisible when seen from the side. This would be

advantageous at night when the user does not want to be seen from the side. The shroud does not affect the beam angle, or diminish light intensity, and is not illuminated when the light is in use .

In this embodiment the light beam 156 is roughly parallel between each Fresnel lens element 124 and the corresponding adjustable lens element 155. Accordingly the Fresnel lens elements 124 may be larger than the lens elements 24 and/or the density of the LEDs 116 and 117 can be greater. The adjustable lens elements 155 can therefore be smaller than the lens elements 24.

The embodiment illustrated by Figs. 13 to 15 is a lens system 21 which may be used on a flashlight or on any other light as desired. The illuminating source is an array 212 of seven LEDs 214 mounted on a printed circuit board (PCB) 215. Six of the LEDs 216 are spaced hexagonally on the periphery of the array with the seventh LED 217 central to the others. The LEDs are equally spaced and can be considered as acting as individual separate point light sources. Immediately in front of the LEDs is a disc-shaped rigid optically clear Fresnel-type first fixed lens array 222 which provides separate circular lens elements 224 for each LED. The Fresnel lens array 222 is preferably made of a polymer material but may be glass. In front of the lens array 222 are, in order, a honeycomb-shaped spacer 262, an optically clear elastomeric lens disc 264, a protective rigid lens 266 and a moveable retaining ring 268. The PCB, lens array, honeycomb spacer, elastomeric lens disc, and rigid lens are all held within an outer housing 270 and retained there by a retaining ring 272 which is attached to, but rotatable with respect to, the housing.

The PCB is heat conductive with the LEDs surface mounted. The outer housing 270 provides a heat sink as well as functioning as a retaining shell.

The honeycomb spacer is made of a rigid material and has an array of holes formed axially through it. The holes 276 are in offset rows to form a close packed configuration with the maximum possible total aperture area while maintaining sufficient strength.

The elastomeric lens disc is made of an optically clear, soft but tough rubbery material having excellent elastic memory.

The retaining ring is adjustable such that in one position (as shown in Fig. 14) there is no or only very light contact between the honeycomb spacer and the elastomeric disc. At this natural stasis, the elastomeric disc provides an optically flat surface adjacent the honeycomb spacer. But at other positions of the retaining ring the elastomeric disc is brought into increasingly firm contact with the front face 263 of the honeycomb spacer. The front face 274 of the elastomeric disc then bears upon the rear face 267 of the rigid lens while the front face 263 of the honeycomb spacer bears upon, and presses into, the rear face 265 of the elastomeric disc 264 (for example as seen in Fig 15). The face 265 is not permanently cut or damaged in any way so that when the pressure is removed the surface 265 returns quickly to its flat state. But, as seen in Fig. 5, the protrusion of portions of the rear face 265 of the elastomeric disc into the channels of the honeycomb spacer creates convex surfaces in the face 265 at the holes 278 and these diffract the light coming through the channels of the honeycomb.

Each Fresnel lens element 224 turns the light from its respective LED into a parallel beam which passes out through the nearby aligned holes 276. When the

honeycomb spacer 262 is not pressing into the elastomeric lens disc 264 the light passes straight through and is projected from the light as a parallel beam (spotlight beam). This is shown in Figs 16 and 17. With a small force pushing the honeycomb surface against the flexible disc, curvatures induced in the face 264 act to refract the incoming light and this results in a spreading or divergence of the beam. This is shown in Figs. 18 and 19.

Figs. 20 and 21 show the situation when the force is increased again and Figs 22 and 23 show the even wider spread of the light beam as the honeycomb spacer distorts the elastomeric lens rear face even more.

The embodiment of the invention shown in Figures 24 and 25 is a lens system 311 having generally the same structure as the system 211 described above. However the lens system 311 has an additional rigid honeycomb-shaped spacer 380, this one between the elastomeric lens disc 364 and the protective rigid lens 366. The rear spacer 362 is held rigid relative to the housing 370 but, as seen most clearly in Fig 25, when the ring 368 is adjusted to compress the contents of the housing 370, and thus press the front spacer 380 rearwards, convex bulges are created on both the front face 374 and the rear face 365 of the elastomeric lens disc. This allows creation of a more widely diverging beam.

The rear spacer 380 is made much thinner than the front spacer 362 because the light rays coming through the holes 384 in the front spacer are not parallel like they are in the holes 378 in the rear spacer 362.

Claims

1. Apparatus for adjusting the angle of divergence of a light beam said apparatus comprising a light source, a flexible transparent element mounted in front of said light source, and means for applying a pressure to said flexible element to thereby alter the shape of the flexible element to an extent corresponding to the amount of said pressure so applied.

2. Apparatus according to claim 1 wherein said flexible transparent element comprises a pair of thin, clear elastomeric membranes with a substantially optically clear liquid filling a plenum space between said membranes.

3. Apparatus according to claim 2 further comprising means for controllably varying the pressure of said liquid in said plenum and thereby controlling the degree to which the liquid distends the membranes to form a convex lens and thereby alter said angle of divergence.

4. Apparatus according to claim 2 or 3 wherein said membranes have at least substantially the same refractive index as said liquid.

5. Apparatus according to claim 4 wherein each said LED shines through its own respective Fresnel lens element and then through its own respective said flexible transparent element, and said light beam exiting said respective Fresnel lens element is divergent.

6. Apparatus according to claim 4 wherein each said LED shines through its own respective Fresnel lens element and then through its own respective said flexible transparent element, and said light beam exiting said respective Fresnel lens element is substantially parallel.

7. A light comprising apparatus according to any one of claims 1 to 6 wherein a plurality of LEDs provide an array of said light sources with each said light source associated with its own respective said flexible transparent element.

8. A flashlight comprising a light according to claim 7.

9. A method of adjusting the angle of divergence of a light beam emanating from a light source, said method comprising applying a pressure to a flexible transparent element mounted in front of said light source, to thereby alter the shape of the flexible element to an extent corresponding to the amount of said pressure applied.

10. A method according to claim 9 wherein said flexible transparent element comprises a pair of thin, clear elastomeric membranes with a substantially optically clear liquid filling a plenum space between said membranes and the pressure of said liquid in said plenum is controllably varied to thereby vary the degree to which the liquid distends the membranes to form a convex lens and thereby alters said angle of divergence.