WO2011154735A1

WO2011154735A1 - Lens element arrangement

Info

Publication number: WO2011154735A1
Application number: PCT/GB2011/051072
Authority: WO
Inventors: Mark Sutton-Vane
Original assignee: Mark Sutton-Vane
Priority date: 2010-06-08
Filing date: 2011-06-08
Publication date: 2011-12-15
Also published as: GB201009554D0; GB2474921B; GB2474921A

Abstract

A lens element arrangement (10) is provided for use in a luminaire. The lens element arrangement (10) has two substantially parallel lens elements (12,120), each having an undulating facetted surface (16,116) and being separated by an air gap (24). In use, a light beam is passed through the lens arrangement (10). The two lens elements (12,120) are moveable relative to each another to create a variable amount of divergence and to create various lighting effects. Such luminaires are used in theatrical and architectural environments.

Description

LENS ELEMENT ARRANGEMENT

The present invention relates to a lens element arrangement particularly, but not exclusively, for use with luminaires. More particularly, the present invention relates to a lens element arrangement for variably adjusting the divergence angle of a beam of light.

BACKGROUND OF THE INVENTION Lenses which increase the divergence angle of a beam of light are well known. The beam of light can be diverged in either one or two directions, depending on the desired effect. Typical lens arrangements utilise arrays of cylindrical plano-concave or cylindrical plano-convex lenses. Plano-concave lenses have a flat surface on one side and a concave surface on the other side. Plano-convex lenses have a flat surface on one side and a convex surface on the other side. Such lenses are commonly known as "elongation" or "spreader" lenses.

It is also known to provide lens elements having a flat surface on one side and a contoured smooth surface on the other side with positive and negative regions in a wave form calculated using a sinusoidal equation. In other words, the thickness of the lens element varies sinusoidally. When two identical lens elements of this type are used in combination back to back in a lens element arrangement, the lenses can be configured to controllably move one lens relative to the other independently along its two axes, so as to provide independent control of beam spread in both dimensions. It is also known to use circular lens elements, which rotate, one relative to the other to provide a beam spread.

A problem of lens elements of this type used in this way is that the beam spread is constantly variable, and it can be difficult to replicate exact divergence of a light source.

It is an object of the invention to provide a new lens element and lens element arrangement, which provides divergence and enhanced control of that divergence. Such lens element arrangements are particularly desirable for use in, for example, architectural and theatrical spot lights and in car headlights.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a lens element arrangement comprising first and second lens elements, at least one of the first and second lens elements comprising first and second opposing sides, at least one of the first and second opposing sides having an undulating surface formed of a plurality of facets disposed at different angles relative to one-another, the first lens element being mounted adjacent the second lens element in a substantially parallel plane, wherein the first and second lens elements are arranged for movement relative to one another, the relative movement enabling step-wise divergence and convergence of a light beam passing through the facets.

By providing a pair of lens elements, a large number of lighting effects are achievable in use when light passes through the facets of the adjacent lens elements.

The lens element arrangement is advantageous because it makes the behaviour of light directed through the lens elements easier to model, because each facet directs light in a predetermined way. The facetted nature of the undulating surface is essential for successful operation of the invention.

The facets themselves are individually identifiable, even on a macroscopic level. Each facet is a simple planar or substantially planar surface through which light can pass. Each facet has definite and distinguishable boundaries. The shape and configuration of each individual facet has been controlled with the result that the resultant lighting effects are wholly predictable and programmable. The first side may have a substantially regular surface. Alternatively, both first and second opposing sides may be formed of a plurality of facets disposed at different angles relative to one-another. The first substantially regular surface may be flat and the second side may have an undulating surface. In this arrangement, the undulating surface may be provided substantially as a wave form, a trough of each wave being formed from a facet substantially parallel with the substantially regular surface and a peak of each wave also being formed from a facet substantially parallel with the substantially regular surface.

Alternatively the substantially first regular surface may be curved. Furthermore, the substantially regular surface may be part-curved and part-flat. Again, the second side may have an undulating surface.

In this alternative arrangement, the undulating surface may be provided substantially as a wave form, a trough of each wave being formed from a facet parallel with a tangent to the substantially regular surface at a central position directly behind the facet and a peak of each wave being formed from a facet parallel with a tangent to the substantially regular surface at a central position directly behind the facet.

A plurality of facets may be disposed at different angles between the trough and peak facets of the undulating surface.

There may be between 1 and 20 facets disposed at different angles between the trough and peak facets.

Furthermore, there may be between 3 and 5 facets disposed at different angles between the trough and peak facets. In commercial use, it is considered that this will be the optimum range of facet numbers for achieving different lighting effects utilising the convergence and divergence of the different facet angles. This number also is a sufficiently large number of facets to use in the planning and design of lighting effects.

There may be a different numbers of facets disposed between the respective trough and peak facets across the undulating surface. By having a different number of facets extending along the length and breadth of the undulating surface, lighting effects achievable using the lens element can be modified according to which portion of the lens element the light rays pass through. This facility could be harnessed when the lens element is moved or translated relative to the incident light beam(s), resulting in a multitude of different and reproducible lighting effects. The facets may be stepped relative to one another in the depth of the undulating surface.

The facets may be discontinuous across the undulating surface. The first and second sides of the lens elements may be coated with an anti-reflective treatment.

At least one facet may be provided with at least one surface irregularity. The surface irregularity may include one or more bobbles, lenslets, dimples or bumps. The irregularities may be used to enhance the divergence angle of a ray or beam of light in more than one direction, leading to potentially spectacular architectural and theatrical lighting displays in use.

The surface of each facet may be smooth. Alternatively, the surface of each facet may be textured.

It is envisaged that the lens elements may be made from glass or plastic.

The lens elements may be made from a film of micro-prisms, or by casting or etching. One or more facets may include a film of micro-prisms, or a region of casting or etching. This is advantageous as a convex profile may be achieved on a substantially flat surface.

The configuration of the two lens elements determines the characteristics of the output beam and the resultant lighting effects in use. In particular, divergence and convergence can be controlled in a step-wise manner.

For example, the first sides of the respective first and second lens elements may face one-another. Alternatively, the second sides of the respective first and second lens elements may face one-another. Alternatively, the first side of the first lens element faces the second side of the second lens element.

One of the first and second lens elements may be provided in convex, plano-convex, or Fresnel lens type form.

At least one of the first and second lens elements may be mounted for movement relative to the other of the first and second lens elements.

At least one of the first and second lens elements may be mounted for translational movement relative to the other of the first and second lens elements.

At least one of the first and second lens elements may be mounted for angular rotation relative to the other of the first and second lens elements. The lens element arrangement may be adapted for use in non-imaging apparatus.

According to a second aspect of the invention, there is provided a luminaire comprising a light source and a lens element arrangement as described in accordance with the first aspect of the invention.

According to a third aspect of the invention, there is provided a method for varying the amount by which light from a light source is diverged comprising the steps of: (a) providing a lens element arrangement, in accordance with the first aspect of the invention, in front of the light source; and (b) moving at least one lens element relative to at least one other lens element.

The method may comprise the step of providing a reflector behind the light source. Since light emitted by the light source is emitted uniformly in all directions, the role of the reflector is to catch this light and convert it into a light beam. The shape of the reflector and its relationship with the light source determines the 'beam angle' of the beam, or in other words, whether a broad or a narrow beam is produced.

The method may comprise the step of moving at least one of the first and second lens elements along at least one of two orthogonal axes disposed in a plane substantially parallel to the other lens element of the first and second lens elements. This is beneficial in the context of architectural lighting because the lens element arrangement can be used as a 'variable spreader lens', effecting divergence of the beam in one axis, instead of two. If however divergence of the beam is required in two axes, at least one of the first and second lens elements may be moved along two orthogonal axes disposed in a plane substantially parallel to the other lens element of the first and second lens elements.

The method may comprise the step of translating at least one of the first and second lens elements along an axis substantially perpendicular to the other lens element of the first and second lens elements. Varying the distance between first and second lens elements is useful as it means that both relatively narrow and more divergent original beams of light can be used in the method of diverging light. The method may comprise the step of rotating at least one of the first and second lens elements about an axis substantially perpendicular to the other lens element of the first and second lens elements.

The movement of the at least one lens element relative to at least one other lens element may occur incrementally to controllably produce diverged light. The convergence/divergence effects only change when the respective facets of adjacent lens elements through which a beam of light is passing, change. In other words, there may be some movement before the light effect changes, thus providing a tolerance for recreation of a different lighting effect created by predetermined positioning of the lenses in a particular orientation relative to one-another.

The size of the facets determines the amount of effective tolerance in achieving a reproducible effect. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a schematic 3D representation of a non-stepped lens element arrangement in accordance with a first embodiment of the invention, configured to achieve maximum divergence of a light beam, showing in particular an undulating surface on one side of a lens element;

Figure 2 is a schematic cross- sectional representation of the lens element arrangement of Figure 1; Figure 3 is the optical equivalent representation of Figure 2;

Figure 4 is a schematic representation of the diverged beam of light as it exits the lens element arrangement of Figure 1, coupled with an indicative light intensity distribution diagram;

Figure 5 is a schematic cross- sectional representation of the lens element arrangement of Figure 1, in which the second lens has been moved along an axis that is substantially parallel to the first lens, thereby adding no divergence; Figure 6 is the optical equivalent of Figure 5;

Figure 7 is a schematic representation of the non-diverged beam of light as it exits the lens element arrangement of Figure 5, coupled with an indicative light intensity distribution diagram;

Figure 8 is schematic 3D representation of a non- stepped lens element arrangement in accordance with a second embodiment of the invention, configured to achieve maximum divergence of a light beam; Figure 9 is a schematic representation of the shape of the resultant light beam as it exits the lens element arrangement of Figure 8;

Figure 10 is a close-up schematic cross- sectional representation of the lens element arrangement of Figure 5, showing in particular how the facets of the first lens element are in alignment with the facets of the second lens element;

Figure 11 is a schematic cross- sectional representation of the lens element arrangement of Figure 10, showing in particular how the facets of the first and second lens elements are out of alignment by approximately half a facet length, causing thereby adding partial divergence;

Figure 12 is a schematic cross-sectional representation of a partially diverged beam of light occurring when the lens element arrangement is as shown in Figure 11, coupled with an indicative light intensity distribution diagram;

Figure 13 is a schematic 3D representation of a lens element arrangement in accordance with a third embodiment of the invention, in a stepped arrangement that achieves maximum divergence of a light beam;

Figure 14 is a schematic cross-sectional representation of the lens element arrangement of Figure 13; and

Figure 15 is a schematic cross- sectional representation of the lens element arrangement of Figure 13, in which the second lens has been moved along an axis that is substantially parallel to the first lens, thereby adding no divergence of the light beam.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

Referring to Figures 1 and 2, a lens element arrangement, indicated generally at 10, comprises a first lens element 12 and a second lens element 120 mounted adjacent to the first lens element 12. Each lens element 12, 120 has a first side having a smooth planar surface 14, 114 and a second side having an undulating surface 16, 116. Each undulating surface 16, 116 comprises a plurality of substantially planar facets 18 or prisms. The inclusion of facets 18 significantly improves the ease with which lighting designers can plan and simulate lighting effects before implementing the lighting apparatus in situ, for example, inside a theatre or church, or outside a monument or historic building. Facets 18 facilitate the exact reproduction of pre-planned lighting effects in situ, because each facet 18 provides a particular effect and as long as the facets 18 are disposed in the predetermined orientation, the different lighting effect will be achieved.

The shape of each facet 18 is square, but may be circular, triangular, rectangular, hexagonal, octagonal or any other shape. The number of facets 18 may vary across the undulating surface 16, 116, for example, in Figure 1 there are 16 facets across the breadth and 17 facets across the length of the first lens element 12. In use, when a beam of light passes through the first lens element 12, light rays are sent in (16 x 17 =) 272 distinct directions, with convergence occurring in some areas, divergence in other areas, and no effect when the facet 18 surfaces are perpendicular to the beam of light. Many of these distinct directions have the same angle of divergence, where the facet angles repeat over the width of the lens element. There may be equal or different numbers of facets 18 provided across the length and breadth of the lens element. The distance or spacing between adjacent facets 18 or prisms may be minimal; indeed the facets 18 or prisms may be adjoining across the length and/or breadth of the lens element, 12, 120. The spacing between adjacent facets 18 or prisms may be constant across the length and/or breadth of the lens element 12, 120. Alternatively, the spacing may vary across the length and/or breadth of the lens element 12, 120 to create various lighting effects as required.

As shown in Figure 1, the first side 14 of the first lens element 12 faces the first side 114 of the second lens element 120. Alternatively, the second side 16, 116 of each respective lens elements 12, 120 may face one another. Alternatively, the first side 14, element 120, 12. Each undulating surface 16, 116 is formed with a wave pattern, for example, a sinusoidal wave pattern, having peaks 20 and troughs 22. The wave pattern repeats regularly across the length and breadth of each lens element 12, 120.

The lens elements 12, 120 are spaced typically between 0.25mm and 5mm apart by an air gap 24, for example, 1mm, 2mm, 3mm or 4mm apart.

The lens elements 12, 120 are transparent and may be made from glass or plastics or any other suitable composite materials. The material properties of each lens element 12, 120 are identical, but may be different. For example, one of the first or second lens elements 12, 120 may take a convex, a plano-convex or a Fresnel lens type form. At least one of the first and second lens elements 12, 120 may be coated with a film of micro-prisms. Furthermore, at least one of the first and second lens elements 12, 120 may be made by casting or etching. A slight stippling of the surface is occasionally also desirable.

Figure 3 shows the optical equivalent of Figure 2. The first and second lens elements 12, 120 are modelled by a discrete series of adjacent prisms 26, having first 28 and second 280 sides. When the air gap 24 between the first and second lens elements 12, 120 is small, the effect of the air gap 24 can be ignored in terms of refraction. As such, the first and second lens elements 12, 120 effectively work together in unison and act as a series of individual prisms 26. In use, a light source (not shown), for example a light bulb, aided by a reflector directs a substantially collimated beam of light, having a plurality of light rays 30, towards the lens elements 12, 120. The light rays 30 impinge on the undulating surface 16, 28 of the first lens element 12 and refract through the first lens element 12. Since the air gap 24 between the first and second lens elements 12, 120 is small, the light rays 30 continue on effectively the same path through the second lens element 120. Since the peaks 20 and troughs 22 of the second lens element 120 are in alignment with the peaks 20 and troughs 22 of the first lens element 12, the light rays are diverged in all directions, in a conventional manner, as they leave the second lens element 120. The beam of light exiting the lens element arrangement 10 is a diverged beam of light and the light rays that constitute the beam of light, are no longer collimated.

As indicated by the dashed lines in Figure 4, the diverged beam of light 32 is substantially circular and has a greater diameter than the source beam of light. Although the beam of light in this embodiment is circular, the diverged beam of light may have an alternative shape, for example, the diverged beam may take a square or substantially square form. The light intensity curve 34, corresponding to the diverged beam of light 32, indicates how the intensity of the light is at a maximum and is substantially uniform within the diverged beam of light. This is due to the regular repeating wave form of the undulating surface 16, 116 across the length and breadth of the lens elements 12, 120. An irregular undulating surface leads to variations in light intensity across the lens elements and causes bright spots within the resultant light beam. This can be desirable for lighting engineers as they align luminaires with particular structural features in situ in preparation for a lighting display.

Turning now to Figure 5, in order to cancel the divergence of the light rays, the second lens element 120 is moved relative to the first lens element 12 with movement occurring in two orthogonal directions in a plane that is substantially parallel to the first lens element 12. The peaks 20 of the first lens element 12 are in alignment with the troughs 22 of the second lens element 120.

As the second lens element 120 moves between the positions shown in Figure 1 and Figure 5, there are three alternative intermediate positions that could be selected, with each position corresponding to a particular degree of divergence. For example, when the lens elements 12, 120 are in the relationship as shown in Figure 1, there is 40 degrees of divergence on the resultant light beam. When the second lens element 120 has moved the distance of one facet, there is 30 degrees of divergence. When the second lens element 120 has moved the distance of two facets, there is 20 degrees of divergence. When the second lens element 120 has moved the distance of three facets, there is 10 degrees of divergence. When the second lens element 120 has moved the distance of four facets to reach the position shown in Figure 5, there is 0 degrees of divergence. These degrees of divergence are illustrative only and the angles of divergence of the beam will depend on several factors, in particular the precise angle of the facets. The range of angles of divergence may be greater, for example, 0 degrees to 120 degrees, and may not be linear, for example, 50 degrees, 30 degrees, 20 degrees, 8 degrees, 0 degrees. The behaviour of the collimated beam of light through the first and second lens elements 12, 120 is simplified and best seen in Figure 6. The first side 28 of each prism 26 is substantially in parallel with the second side 280 of each prism. Therefore when collimated light rays 30 impinge on the first side 28 of each prism 26, each light ray 30 refracts as it travels through the prism, and refracts back again to its original path upon leaving the prism 26. The light rays 30 remain collimated throughout the process.

As shown in Figure 7, the resultant beam of light 36 is circular and smaller than the diverged beam of light. The intensity 38 of the resultant beam of light 36 is greater than the corresponding diverged beam of light 34, 32.

If and when movement occurs in only one of the two orthogonal axes, the resultant beam of light reduces in size in only one axis and its shape becomes elongate. Referring to Figures 8 and 9, a second embodiment of the lens element arrangement is indicated generally at 58 and comprises a first lens element 60 and a second lens element 600. Each lens element 60, 600 is identical and has a substantially planar surface 62 and an undulating surface 64 formed using a plurality of elongate rectangular facets 66. The peaks 68 and troughs 70 of the first lens element 60 are in vertical alignment with the peaks 68 and troughs 70 of the second lens element 600. In use, when light passes through the lens element arrangement 58, maximum divergence occurs and the resultant light beam is indicated at 74. When one of the first 60 and second 600 lens elements is moved in the directions indicated by the arrow, light diverges in one axis only and the resulting light beam is indicated at 72. In this way, the lens element arrangement acts as a 'variable spreader lens'.

Figure 10 shows a close-up of the first embodiment of the invention, in which the individual facets of the lens element are shown more clearly. There are three facets 18 between each peak 20 and trough 22 of the wave, although any number of facets could be used. Each peak 20 and trough 22 has a facet 18, although it is possible that this may not be the case and that there are simply facets leading to a maximum and a minimum in the surface profile. When the first and second lens elements 12, 120 are in vertical alignment and light rays 30 pass through the lens element arrangement 10, there is no divergence of the incident light beam. Furthermore, the resultant light beam is collimated, like the incident light beam.

In Figure 11, the second lens element 120 is moved in an axis parallel to that of the first lens element 12 such that the second lens element 120 has shifted the equivalent distance of half a facet 18 length relative to the first lens element 12. When light rays 30 pass through the lens element arrangement, rays of light pass through a facet 18 in the first lens element 12 and then through two parts of a facet 18 in the second lens element 120. Consequently, some light rays 30 are diverged and some light rays 30 are not diverged, thus adding partial divergence.

Figure 12 indicates the resultant beam of light that corresponds to that of Figure 9. The resultant beam of light 44 has a bright central spot and a peripheral ring of less intense light. This is advantageous for lighting designers when positioning and directing luminaires in preparation for lighting displays.

A third embodiment of the lens element arrangement is indicated generally at 46 in Figure 13. Like components have been given the same reference numerals as in previous figures. The undulating surface 48, 480 of the first 50 and second 500 lens elements comprises a plurality of stepped facets 52, as well as non- stepped facets 18, with each stepped facet 52 being stepped along at least one of its edges. The edges of the steps are substantially perpendicular to the lateral plane of the lens element 50, 500. Stepped facets 52 are grouped together on vertical levels. For example, as shown in Figure 11, in each trough 22 of the first undulating surface 48, 480 is a first group 54 of nine facets 52, arranged in a 3 by 3 array. Surrounding this first group 54, is a second group 56 of facets 52, situated on a lower level relative to the upper most surface on the undulating surface 48. For each of the outer facets in the first group 54, there is an adjacent and stepped facet 52 in the second group 56. At each corner of the first group 54, there is an additional stepped and adjacent facet 52, provided at a lower level than the second group 56. The size of each step is typically between 2 and 5 mm, but can be up to 10 mm. Stepped facets 52 are beneficial as the thickness of each lens element 50, 500 may be reduced, thereby reducing the material cost of each lens element. As best seen in Figure 14, individual and grouped facets, both non-stepped 18 and stepped 52 alike, are angled relative to the horizontal by various amounts to form a substantially interrupted sinusoidal wave. This achieves unique and distinct lighting effects in use. For example only, facets (a) and (e) are substantially horizontal and substantially parallel with the first side 14 of the first lens element 12. Facets (b) and (d) have an angle of approximately minus 5° to minus 10° to the horizontal. Facet (c) has an angle of approximately minus 25° to the horizontal. Facets (f) and (h) have an angle of approximately 5° to 10° to the horizontal. Facet (g) has an angle of approximately 25° to the horizontal. Each angled facet results in a different angle of beam divergence. It is envisaged that a surface of each lens element may have a rough or jagged profile, for example, rather than an undulating or wave profile, the facets rise gently to the left (like facet d), steeply to the right (like facet g), steeply to the left (like facet c), gently to the left (like facet d), gently to the right (like facet f), flat (like facet a). Since the second lens element 500 is substantially identical to the first lens element 50, light rays diverge as they pass through the lens element arrangement 46.

To cancel the divergence, as shown in Figure 15, the second lens element 500 is moved relative to the first lens element 50 in a plane that is parallel to the first lens element 50. An air gap 24 of constant magnitude is maintained between the first and second lens elements 50, 500. Since each lens element 50, 500 has a repeating surface contour, and the first and second lens element 50, 500 are identical, moving the second lens element 500 to the right produces the same lighting effect as moving the second lens element 500 to the left. However, if the first and second lens elements 50, 500 did not include a repeating surface contour, moving the second lens element 500 to the left (or right) would produce a different lighting effect to that achieved when moving the second lens element 500 to the right (or left), which can be included as part of a bespoke lighting display. Translating one or both of the lens elements so as to increase the air gap 24 between the lens elements will result in enhanced lighting effects. Furthermore, this translation may be beneficial because the incident light beam need not be as narrow and can be more divergent. The shape of the reflector is therefore less critical.

The lens elements are ideally suited for use in luminaries, for example, for lighting of architectural features, because by using a two lens arrangement, as described above, a feature can be lit precisely by a specific luminaire. The lens element arrangements may be used in luminaries, either singly or in multiples and independently or interactively, as desired.

For example, two or more of the lens element arrangements could be mechanically or electro-mechanically linked together, so that the luminaires to which the lens element arrangements are fitted would have their light output modified in an identical or a similar or related way.

Any of the lens elements or alternative features described may be used in a lens element arrangement including two lens elements and a light source. Furthermore, extra lens elements, light filters or other optical components can be used in conjunction with the embodiments described.

In addition to using the lens arrangements in lights for architectural and theatrical purposes, it is envisaged that the lens arrangement may be used in car headlights. It is also envisaged that the headlights might be linked together in such a way that each of the two lens element arrangements would be able to provide different degrees of divergence of the light beams.

In brief, a lens element including facets on one or more of its surfaces makes planning and simulating lighting effects in the early stages of the lighting display design process easier. It also means that proposed lighting displays are more accurately reproduced in situ, for example, when used to highlight architectural features or when used as part of a dynamic sound and light show. It is understood that variations may be made in the foregoing without departing from the scope of the invention. For example, the elements and teachings of the various illustrative embodiments may be combined in whole or in part in some or all of the illustrative embodiments. In addition, one or more of the elements and teachings of the various illustrative embodiments may be omitted, at least in part, and/or combined, at least in part, with one or more of the other elements and teachings of the various illustrative embodiments.

Claims

A lens element arrangement comprising first and second lens elements, at least one of the first and second lens elements comprising first and second opposing sides, at least one of the first and second opposing sides having an undulating surface formed of a plurality of facets disposed at different angles relative to one-another, the first lens element being mounted adjacent the second lens element in a substantially parallel plane, wherein the first and second lens elements are arranged for movement relative to one another, the relative movement enabling step-wise divergence and convergence of a light beam passing through the facets.

A lens element arrangement as claimed in claim 1 , in which the first side has a substantially regular surface.

A lens element arrangement as claimed in claim 2, in which the substantially regular surface is flat.

A lens element arrangement as claimed in claim 2, in which the substantially regular surface is curved.

A lens element arrangement as claimed in any one of claims 1 to 4, in which the second side has an undulating surface.

A lens element arrangement as claimed in claim 5, in which the undulating surface is provided substantially as a wave form, a trough of each wave being formed from a facet substantially parallel with the substantially regular surface and a peak of each wave being formed from a facet substantially parallel with the substantially regular surface.

A lens element arrangement as claimed in claim 5, in which the undulating surface is provided substantially as a wave form, a trough of each wave being formed from a facet parallel with a tangent to the substantially regular surface at a central position directly behind the facet and a peak of each wave also being formed from a facet parallel with a tangent to the substantially regular surface at a central position directly behind the facet.

8. A lens element arrangement as claimed in claim 6 or 7, in which there are a plurality of facets disposed at different angles between the trough and peak facets.

9. A lens element arrangement as claimed in any one of claims 6 to 8, in which there are between 1 and 20 facets disposed at different angles between the trough and peak facets.

10. A lens element arrangement as claimed in claim 9, in which there are between 3 and 5 facets disposed at different angles between the trough and peak facets.

11. A lens element arrangement as claimed in any of claims 8 to 10, in which there are a different numbers of facets disposed between the respective trough and peak facets across the undulating surface.

12. A lens element arrangement as claimed in any one of claims 5 to 11, in which the facets are stepped relative to one another in the depth of the undulating surface.

13. A lens element arrangement as claimed in any one of claims 5 to 12, in which the facets are discontinuous across the undulating surface.

14. A lens element arrangement as claimed in any preceding claim, in which the first and second sides of the lens element are coated with an anti -reflective treatment.

15. A lens element arrangement as claimed in any preceding claim, in which at least one facet is provided with at least one surface irregularity.

16. A lens element arrangement as claimed in claim 15, in which the surface irregularity includes one or more bobbles or lenslets or dimples or bumps.

17. A lens element arrangement as claimed in any preceding claim, in which the surface of each facet is smooth.

18. A lens element arrangement as claimed in any preceding claim, in which the surface of each facet is textured.

19. A lens element arrangement as claimed in any preceding claim, in which at least one of the first and second lens elements is made from glass or plastic.

20. A lens element arrangement as claimed in any preceding claim, in which at least one of the first and second lens elements is made from a film of micro- prisms, or by casting or etching.

21. A lens element arrangement in which at least one of the first and second lens elements is substantially as described herein with reference to and as illustrated in the accompanying drawings.

22. A lens element arrangement as claimed in any one of the preceding claims, in which the first sides of the respective first and second lens elements face one- another.

23. A lens element arrangement as claimed in any one claims 1 to 21, in which the second sides of the respective first and second lens elements face one-another.

24. A lens element arrangement as claimed in any one claims 1 to 21, in which the first side of the first lens element faces the second side of the second lens element.

25. A lens element arrangement as claimed in any one of the preceding claims, in which one of first and second lens elements is provided in convex, planoconvex, or Fresnel lens type form.

26. A lens element arrangement as claimed in any one of the preceding claims, in which at least one of the first and second lens elements is mounted for translational movement relative to the other of the first and second lens elements. A lens element arrangement as claimed in any one of the preceding claims, in which at least one of the first and second lens elements is mounted for angular rotation relative to the other of the first and second lens elements.

A lens element arrangement as claimed in any preceding claim when used in non-imaging apparatus.

A lens element arrangement substantially as described herein with reference to and as illustrated in the accompanying drawings.

A luminaire comprising a light source and a lens element arrangement as claimed in any one of claims 1 to 29.

A method for varying the amount by which light from a light source is diverged comprising the steps of :

a. Providing a lens element arrangement, as claimed in any one of claims 1 to 29, in front of the light source; and

b. Moving at least one lens element relative to at least one other lens element.

A method for varying the amount by which light from a light source is diverged as claimed in claim 31, comprising the step of:

a. Providing a reflector behind the light source.

A method for varying the amount by which light from a light source is diverged as claimed in claim 31 or 32, comprising the step of:

a. Moving at least one of the first and second lens elements along at least one of two orthogonal axes disposed in a plane substantially parallel to the other lens element of the first and second lens elements.

A method for varying the amount by which light from a light source is diverged as claimed in claims 31 to 33, comprising the step of:

a. Translating at least one of the first and second lens elements along an axis substantially perpendicular to the other lens element of the first and second lens elements.

35. A method for varying the amount by which light from a light source is diverged as claimed in any one of claims 31 to 34, comprising the step of: a. Rotating at least one of the first and second lens elements about an axis substantially perpendicular to the other lens element of the first and second lens elements.

36. A method for varying the amount by which light from a light source is diverged as claimed in any one of claims 31 to 35, in which the movement of the at least one lens element relative to at least one other lens element occurs incrementally to controllably produce diverged light.

37. A method for varying the amount by which light from a light source is diverged substantially as described herein with reference to and as illustrated in the accompanying drawings.