WO2008149277A1

WO2008149277A1 - Variable beam illumination assembly

Info

Publication number: WO2008149277A1
Application number: PCT/IB2008/052138
Authority: WO
Inventors: Matthias Wendt; Bernd Ackermann; Reinhold Elferich
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2007-06-05
Filing date: 2008-06-02
Publication date: 2008-12-11

Abstract

An illumination assembly comprising a light source, an optical component and a positioning mechanism comprising a movable member and at least one electromechanical polymer actuator, being operable to move either the optical component or the light source or both to different positions along a mechanical axis, is configured and can be conveniently adjusted to project a light beam at a distant location with a variable beam spread and over a variable distance. The capability of an electromechanical polymer actuator to realize large deformations allows for ample displacement of the positioning mechanism. Thus, the illumination assembly according to the invention is highly suited for fine-tuned actuation of a light beam, particularly from spot to flood illumination. These features further provide for a mechanically simple device that is both inexpensive and reliable.

Description

VARIABLE BEAM ILLUMINATION ASSEMBLY

TECHNICAL FIELD OF THE INVENTION

This invention relates to a variable beam illumination assembly, particularly a spotlamp, comprising a light source, an optical component and a positioning mechanism that is capable of manipulating a light beam by adjusting the position of the light source relative to the optical component.

TECHNICAL BACKGROUND OF THE INVENTION

It is well known in the art to provide for adjustability in spotlamps, that permits variation of the beam from a relatively narrow "spot" type beam to a relatively wide "flood" beam. Conventionally, the adjustment is accomplished by moving a light bulb back and forth in a lamp housing relative to a fixed focusing reflector or a fixed lens by means of a screw mechanism. In the past, this type of adjustability has been generally satisfactory because spotlamps were of sufficient size to contain the necessary adjustment mechanism. However, recent advances in the art have resulted in miniature light sources. Particularly light-emitting diodes, but also high-intensity light bulbs, are quite small in size.

While such small-sized light sources have permitted a substantial reduction in the overall size of the spotlamps, which employ them, this has at the same time resulted in a number of problems associated with the provision of a movable arrangement for focusing the light beam.

The Maglite™ flashlight is a prior art device that has an adjustable spot beam. An incandescent light bulb is arranged inside an essentially parabolic reflector.

This device enables a variable beam angle ranging from a narrow spot beam to a wide flood beam, by including a rotating actuator for moving the reflector axially with respect to the incandescent bulb. Also WO 98/40665 discloses a light source comprising an array of multicolor light emitting diodes (LEDs), wherein the array is mounted on a flexible diaphragm- like support structure, which may be deflected to focus a beam of variable colored light by a conventional actuator. However, conventional actuators have the disadvantage that small actuators exhibit low efficiency and large actuators, such as screw mechanism, are bulky and heavy.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a variable beam illumination assembly with the ability to readily adjust or focus a light beam, using few lightweight moving parts, while still offering ease of adjustment.

The present invention provides an illumination assembly comprising a light source 2, an optical component 1 and a positioning mechanism comprising a movable member 3 and at least one electromechanical polymer actuator 4, being operable to move either the optical component 1 or the light source 2 or both to different positions along a mechanical axis.

The capability of an electromechanical polymer actuator to realize large deformations - up to 40% in the current state of the art - allows for ample displacement of the movable member. Thus, the illumination assembly according to the invention is highly suited for fine-tuned actuation of a light beam, particularly from spot to flood illumination. Such an illumination assembly is configured and can be conveniently adjusted to project a light beam at a distant location with a variable beam spread and over a variable distance. These features further provide for a mechanically simple device that is both inexpensive and reliable.

According to one embodiment of the invention, the electromechanical polymer actuator 4 is operable in parallel to the mechanical axis.

According to an alternative embodiment of the invention, the electromechanical polymer actuator 4 is operable transversely to the mechanical axis.

Preferably, the positioning mechanism comprises an array of electromechanical polymer actuators. Preferably, the array of actuators may be stacked in parallel in a multilayer arrangement and electrically connected in parallel. Alternatively, the array of actuators may be arranged in series side by side and electrically connected in parallel.

The optical component 1 may be a reflective element, preferably a reflector, more preferably a parabolic reflector. Alternatively, the optical component 1 may be a refractive element, preferably a lens 6. However, other optical components are also within the scope of the invention.

Typically, the positioning mechanism is operable for linear displacement. Alternatively, the positioning mechanism may be operable for tilting displacement. According to a preferred embodiment of the invention, the illumination assembly comprises additionally a control mechanism, wherein the control mechanism is operable by remote control.

Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view of a first embodiment of an illumination apparatus, wherein the actuator is contracted. Fig. 2 is a cross-sectional view of a first embodiment of an illumination apparatus, wherein the actuator is expanded. Fig. 3 is a cross-sectional view of a second embodiment of an illumination apparatus, wherein the actuator is expanded. Fig. 4 is a cross-sectional view of a second embodiment of an illumination apparatus, wherein the actuator is contracted.

Fig. 5 is a cross-sectional view of a third embodiment of an illumination apparatus, wherein the actuator is expanded.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, the invention is described in broad terms as an illumination assembly comprising a positioning mechanism that is configured to control the position of an optical component 1 with respect to a light source 2. The positioning mechanism includes an electromechanical polymer actuator 4 configured to move a movable member 3 to adjust the distance between a light source 2 and an optical component 1. This adjusted distance controllably adjusts the beam spread of the imaged light. The positioning mechanism is preferably mounted on a frame. In the illustrated embodiments, the frame structure is shown as a single plate, but typically the plate will be part of a housing, comprising a base and/or sidewalls, defining a frame for support of the illumination source 2 and/or the optical component 1 and/or the positioning mechanism. The light source 2 in the illustrated embodiments is a light-emitting diode, but it should be understood that the light source may include any light source that is capable of producing visible, UV or IR radiation. Preferably, the light source has an emission in the visible range. Thus, the term "light source" should be understood to refer to any one or a number of a variety of radiation sources, including, but not limited to LED-based sources, incandescent sources, e.g., filament lamps and halogen lamps, and gas discharge sources, e.g. sodium vapor, mercury vapor, and metal halide lamps. Particularly light-emitting diode (LED) lamps can be used as light sources.

The light source 2 is preferably supported by a lamp base that accommodates current supply means, such as lead-in wires. One main feature of the illumination assembly is the use of a beam adjustment mechanism by an optical element to provide a desired light distribution over a target surface.

A light source generally emits divergent radiation that has to be manipulated by an optical component 1 to provide a light beam. Thus, the illumination assembly according to the invention includes an optical component 1 that is positioned relative to the light source 2 in such a way that the divergent radiation from the illumination source is shaped into a light beam of desired beam width and shape.

Preferably, the optical component 1 is a reflective or refractive optical component. A reflective optical component is defined as a component that changes the direction of a light ray at an interface of the component between two dissimilar media so that the light beam returns into the medium from which it originated. A refractive optical component is defined as a component that bends a light ray, as it passes obliquely from one medium into another, toward the normal of the interface of the component.

Thus, the reflective optical component 1 may preferably be or comprise a reflector or a mirror, the refractive optical component 1 may preferably be or comprise a lens or a lens system.

Shape and color of the light beam may be further influenced by additional optical components such as a color filter, a prism, a shutter, a waveguide or any other suitable optical component 1 for manipulating a light beam.

In a system comprising an optical element, the optical axis is an imaginary line that defines the path along which light propagates through the system. For a system composed of simple reflectors, lenses or mirrors, the optical axis passes through the center of curvature of each surface, and coincides with the axis of rotational symmetry. The optical axis of an illumination assembly according to the invention is often, but not necessarily, coincident with the mechanical axis of the assembly. Another feature of the invention is that a positioning mechanism, supported by the frame, is configured to control the position of the optical component with respect to the light source.

The mechanism for positioning a light source 2 relative to an optical member comprises a movable member 3 and at least one electrically movable, electromechanical polymer actuator 4 connected to said movable member 3 and operable to move said movable member 3 to selected positions to manipulate the light beam emitted by the light source 2.

The adjusted distance of the selected positions contra llably adjusts the beam spread of the imaged light. An electromechanical polymer actuator 4 utilizes the Maxwell stress phenomenon. This phenomenon relates to the deformation of an electroactive polymer member sandwiched between two electrodes.

Known in the art as polymer actuators are gel actuators using a conductive polymer gel, polymer membrane actuators using a conductive polymer membrane, etc.

The polymer member is advantageously made of a dielectric elastomer, such as silicone or fluorocarbon rubber or an acrylic polymer rubber such as acrylnitril rubber NBR, styrol butadiene rubber SBR, chloroprene rubber CR, butadiene rubber BR and ethylene propylene diene rubber EPDM. The characteristics of dielectric elastic polymers are such that they are soft (compliant), have a relatively high dielectric constant and a high breakdown voltage. The electrodes are made of compliant (soft) material too, so that they can deform with the polymer member. The electrodes may be deposited via spraying, screen- printing, or photolithography. The electrodes can be made of graphite paste, graphite powder, very thin metal wires, or very thin metal films.

The capabilities of the electroactive polymer can be used for a single actuator or for an actuator array comprising a plurality of actuators.

According to one embodiment of the invention, the plurality of actuators are alternately stacked in a multilayer arrangement and electrically connected in parallel, thereby forming a multilayer actuator. The strain of the polymer (generally of the order of several ten percent) has a quadratic relation to the voltage difference V. It must be of the order of a few kV, depending on the thickness of the polymer film. To reduce the voltage to several 100 V, the multi- layered structure of the polymer actuator may be advantageously used.

Alternatively, a plurality of polymer actuators may be arranged in parallel side by side and electrically connected in parallel.

The actuator or the actuator array is connected to suitable circuitry, which may be mounted thereon or embedded therein for providing electrical signals to each actuator.

When a voltage difference is applied between said electrodes, the electrostatic forces resulting from the free charges squeeze the polymer perpendicularly to the direction of the electric field. The squeeze is compensated by a stretch of the polymer perpendicular to the direction of the electric field. Thus, the actuator has a varied extent of expansion and contraction, depending on the magnitude of an applied voltage. This can be utilized as a driving force to exert a force on an object or move an object.

According to an important aspect of the invention, the actuator is configured to move a movable member 3 in the direction of a mechanical axis, which is preferably coincident with the optical axis of the illumination assembly.

The movable member 3 is configured to support either the light source 2 or the optical member 1 or both. The movable member 3 may be preferably configured as an expandable support member or a slideable support member.

According to one embodiment of the invention, the movable member 3 is an expandable support member, i.e. a resilient member that generates a restoring force against expansion and contraction of the actuator, such as an elastomer membrane or a flexible spring, a Belleville spring washer, a cup spring washer, a disk washer or any other expandable member of conventional design.

According to another embodiment of the invention, the movable member 3 is a slideable support member and may be configured as a self-supporting scissor grid, telescopic means, a pantograph-type manipulator or rack and pinion gear or any other slideable member of conventional design.

When using a slideable support member there may be a need to employ a separate restoration mechanism such as a spring or a flexible or elastic member. The restoration mechanism generates a restoring force against the actuator that is compressed or expanded. The positioning mechanism may be configured for linear displacement parallel to the optical axis or transverse thereto in a push-pull arrangement for forward and rearward movement. Alternatively, it may be configured for a rotational, tilting movement relative to a mechanical axis.

To guide the movable member 3 for stable operation, the movable member 3 may be combined with guiding means, such as a sliding baffle that is received in an open slot in the housing or in a guide rail.

In an illumination assembly according to the invention, the light source 2 as well as the electrically movable electromechanical polymer actuator 4 are adapted to be connected to conventional current connector means providing alternating current electrical power to the illumination assembly, so that the assembly may easily substitute conventional illumination assemblies.

To achieve this aim, the lamp support base is a conventional connector member, which may be connected to a conventional alternating current source of electrical energy, not shown.

Likewise, the actuator is electrically connected to a voltage-supplying unit to supply an actuating voltage. Further, the illumination assembly may comprise certain electrical control components for energizing and controlling the light source, such as electrical control circuitry and voltage conversion or rectifier devices. Such components may be mounted on the housing and can be easily replaced when defective or in need of repair. It will be recognized that such electrical components are well known to those skilled in the art. Operation control of the device may be done manually or by electronic control means. Particularly, the system may be coupled to a remote operating unit via IR or RF signals (not shown) in a manner known to those skilled in the art.

The first exemplary embodiment illustrated in the drawings relates to a spot and flood lamp of the general type wherein the adjustability of the light beam is accomplished by axial movement of an illumination source relative to a fixed optical component in the direction of the main optical axis of the optical component.

Referring to the drawings of Fig. 1 and 2, an illumination assembly according to the first exemplary embodiment of the invention comprises a light-emitting diode as the light source and a reflector 1 as the optical component 1. Such an assembly is commonly referred to as reflector lamp.

The kind of reflector used for illumination purposes generally has an elliptical, parabolic or conical section basic shape.

Preferably, the reflector is a parabolic-shaped reflector because such a reflector provides a theoretical focus of the light when the light source is positioned at the parabolic reflector's focal point. Light emanating from a light bulb positioned at the focal point of a parabolic reflector is reflected parallel to the parabolic reflector's optical axis to provide for a uniform or substantially uniform light beam.

The reflector 1 comprises a reflector body including a reflector portion having a concave reflecting surface with an optical axis and, integral therewith, a hollow neck-shaped portion about the optical axis.

The neck-shaped portion is formed as a receptacle that accommodates the light source 2.

In this embodiment, the reflector 1 is held in position by mechanical fastening means (not shown), fixed to the frame or the outside of the housing. The light source 2 is aligned with the reflector 1 , but not fixed to it. The positioning mechanism includes an expandable membrane as the movable member 3.

The expandable membrane is suitably connected to the frame to form a space with an expandable wall and is operably connected to the light source 2.

The extensible side faces of a multilayer electromechanical polymer actuator 4 are connected to the movable member 3 and the frame.

If a voltage V is applied between the electrodes of the actuator, the actuator expands in the horizontal direction, in a plane transverse to the plane defined by the expandable membrane.

The actuator is configured to move the membrane forward and rearward relative to the frame. Movement of the membrane causes a corresponding movement of the lamp support and the illumination source relative to the optical means on the frame. The controlled movement of the illumination source relative to the reflector 1 adjusts the beam angle of the illumination source.

A comparison of Fig. 1 to 2 illustrates the effect that the movement of the movable member 3 in a forward and a rearward direction has on the support and lamp within the receptacle of the reflector 1.

Fig. 1 shows the position of the movable member 3 and the lamp support when the actuator is fully contracted in a rearward direction. The lamp is drawn to its closest position to the base portion of the reflector 1 at its greatest distance from the focal point of the reflector 1, causing the beam of light emanating from the lamp to be focused to a wide or flood beam of light on the target area 5, as indicated by curved arrow 5.

When an electric field is applied at the electrodes, the polymer contracts due to electrostatic forces and expands in orthogonal direction. Fig. 2 shows the position of the lamp support and the lamp after the actuator has fully expanded in a forward direction and the lamp is seated in the focal point of the reflector 1. The lamp is drawn to the focal point of the reflector 1. Consequently, the beam of light emanating from the lamp is focused to a narrow or spot beam on the target area 5, as indicated by curved arrow 5.

By positioning the lamp holder in any position intermediate between its forward position and its fully retracted position, the proportion of light intensity of the beam to that of the diffused light can be selected as required.

Figs. 3 and 4 depict an alternative exemplary second embodiment according to the invention.

Also the second exemplary embodiment relates to a reflector lamp - to an illumination assembly comprising a light-emitting diode as the light source 2 and a reflector 1 as the optical component 1.

In the second embodiment, the light source 2 and the reflector are displaceable, or movable, together in the direction of the main optical axis of the reflector. This alternative allows the use of a conventional reflector lamp design, wherein an end portion of the electric lamp is secured in the neck portion of the reflector body. It differs also from the first embodiment in that the actuator moves transversely to the optical axis of the illumination assembly.

In the second illustrated embodiment, the actuator is arranged between two interconnected disk springs. The centre of the first disk spring is arranged on the frame in a fixed manner. The lamp and the reflector 1 are arranged on the centre of the second disk spring, also in a fixed manner.

The actuator is arranged in the cavity between the two disk springs and fastened to the rim of the interfacial rim of the two disk springs.

Figs. 3 and 4 depict the second exemplary embodiment of an illumination assembly according to the invention in a first and a second position. If a voltage V is applied between the electrodes, the actuator expands in the radial direction, in a plane parallel to the plane defined by the rim of the disk springs. As a consequence, the two disk springs also deform in opposite directions, which causes their radius of curvature to change.

Accordingly, the light beam projected from the reflector and the lamp may be altered to provide a somewhat focused beam or a diffused beam directed to a centroid point of the target area 5. The diffused light obtained is equal in intensity but is spread over a larger target area 5.

Fig. 5 shows a third embodiment of an illumination assembly, wherein a light source 2 is associated with a converging lens 6 as an optical element, which is displaceable, or movable, in the direction of the main optical axis of the light source 1 in order to focus the light distribution pattern.

The positioning mechanism of this third embodiment is based on a mechanical sliding principle.

The movable member 3 thereof comprises a scissor grid mechanism that is provided with scissor arms, which are interconnected in a crosswise pivotable manner. The scissor mechanism can move between a collapsed position and an extended position for positioning the lens 6 with respect to the light source 2.

As shown, the scissor grid is self-supporting, but may be supported in a guide rail fastened to a frame member.

The scissor grid is manipulable by at least one polymer actuator 4. The actuator is located adjacent to the scissor grid, parallel to the mechanical axis and connected to at least two fastening points of the scissor grid.

As shown, a converging lens 6 is mounted in front of the scissor grid, which allows the lens 6 to be moved freely back and forth in the direction of the optical axis of the diverging light emitted by a light source 2. The actuator is operable to move the scissor grid in opposite directions along the central axis of the apparatus between a forward and a rearward position.

When a voltage V is applied between the electrodes, the actuator 4 contracts in the axial direction and expands in the radial direction. Accordingly, the actuator 4 tries to contract in its longitudinal direction. As a result, the distance between the light source and the lens becomes shorter, and the focus of the light beam is moved rearward.

When the voltage application is suspended, the deformed actuator 4 returns to the original shape preferably by virtue of a restoring force of the restoring mechanism, not shown. Thus, the actuator 1 returns from the contraction state. Decreasing the distance between the front lens 6 and the rear light source causes the optical system's focal length to shorten, thus controllably increasing the beam spread at the target surface 5. Conversely, increasing the distance between the front lens 6 and the rear light source causes the optical system's focal length to lengthen, thus contra llably decreasing the beam spread at the target surface 5.

By positioning the lens in any position intermediate between its forward position and its fully retracted position, the proportion of light intensity of the beam to that of the diffused light can be selected as required.

The invention has been described by means of several preferred embodiments. Modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. This description is to be construed as illustrative only, and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the intention, and the exclusive use of all modifications, which come within the scope of the appended claims, is reserved.

LIST OF NUMERALS:

1 reflector

2 light source

3 movable member

4 electromechanical polymer actuator 5 illuminated target area

6 lens

Claims

CLAIMS:

1. An illumination assembly comprising a light source 2, an optical component 1 and a positioning mechanism comprising a movable member 3 and at least one electromechanical polymer actuator 4, being operable to move either the optical component 1 or the light source 2 or both to different positions along a mechanical axis.

2. An illumination assembly according to claim 1, wherein the electromechanical polymer actuator 4 is operable in parallel to the mechanical axis.

3. An illumination assembly according to claim 1, wherein the electromechanical polymer actuator 4 is operable transversely to the mechanical axis.

4. An illumination assembly according to claim 1, wherein the positioning mechanism comprises an array of electromechanical polymer actuators being stacked in parallel and electrically connected in parallel.

5. An illumination assembly according to claim 1, wherein the positioning mechanism comprises an array of electromechanical polymer actuators arranged in series and electrically connected in parallel.

6. An illumination assembly according to claim 1, wherein the optical component 1 is a reflective element.

7. An illumination assembly according to claim 1, wherein the optical component 1 is a refractive element.

8. An illumination assembly according to claim 1, wherein the positioning mechanism is operable for linear displacement.

9. An illumination assembly according to claim 1, wherein the positioning mechanism is operable for a tilting displacement.

10. An illumination assembly according to claim 1, comprising additionally a control mechanism, wherein the control mechanism is operable by remote control.