WO2015036295A1

WO2015036295A1 - Optical device, lighting device and luminaire

Info

Publication number: WO2015036295A1
Application number: PCT/EP2014/068685
Authority: WO
Inventors: Wilhelmus Petrus Adrianus Johannus Michiels; Marcellinus Petrus Carolus Michael Krijn
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-09-10
Filing date: 2014-09-03
Publication date: 2015-03-19

Abstract

The invention relates to an optical device comprising a mutually spaced first and second optical layer, each comprising reflective, refractive and/or total internal reflection (TIR) purposely oriented, non-scattering shaping elements. The optical device is configured to a) transform light from a light source into a beam of uniform, pre-shaped light by the first optical layer, and subsequently b) fine-tune and condense said beam of uniform, pre-shaped light into a beam of uniform, end-shaped, condensed light by the second optical layer. Optionally a third optical layer is provided to subsequently collimate the beam of uniform, end-shaped, condensed light into a parallel beam of uniform, end-shaped, collimated light. The invention further relates to a lighting device comprising said optical device and to a luminaire comprising said lighting device.

Description

OPTICAL DEVICE, LIGHTING DEVICE AND LUMINAIRE

FIELD OF THE INVENTION

The invention relates to an optical device which is configured to reshape light from a light source into a light having a specified light distribution. The invention further relates to a lighting device comprising said optical device and to a luminaire comprising at least one said lighting device.

BACKGROUND OF THE INVENTION

Optical devices for transformation of light from a light source into a light rendering a specified light distribution are generally known in the prior art. Frequently these optical devices aim at reshaping a non-uniform light distribution of the light as issued from the light source into a desired light distribution over the target area to be illuminated. Such an optical device is known from, for example, US20120275187A1 disclosing a backlight system wherein the reshaped light distribution is such that it conforms to the ideal brightness distribution on the screen for human eyes' vision. Thereto the known optical device comprises a first optical layer, and optionally a second optical layer, with scattering microstructures which are distributed in a specified density pattern over the major surface of a light guide panel. By selection of the density of the scattering microstructure elements, the amount of light locally extracted from the light guide plate is controlled and hence the light (intensity) distribution as extracted from the light guide plate is controlled. However, the known optical device has the disadvantages that light beams with a sharp, detailed beam pattern cannot be obtained, and that the efficacy of the optical device is relatively low because a significant amount of light is issued to outside the target area.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an optical device of the type of known optical device as described above, in which at least one of the abovementioned disadvantages is counteracted. Thereto the optical device according to the invention comprises a mutually spaced first and second optical layer, each comprising reflective, refractive and/or total internal reflection (TIR) purposely oriented, non-scattering shaping elements, the shaping elements of the first optical layer facing away from the second optical layer, the optical device being configured to, a) transform light from a light source into a beam of uniform, pre-shaped light by the first optical layer, and subsequently b) fine-tune and condense said beam of uniform, pre-shaped light into a beam of uniform, end-shaped, condensed light by the second optical layer. Contrary to the known optical device, in which the scattering microstructures cause blurring and hamper generating sharp, detailed beam patterns and additionally cause light to be scattered to outside the target area, the optical device according to the invention has non-scattering shaping elements to reshape the light. Said non-scattering shaping elements are purposely oriented and are generally at least one of the group consisting of a specular reflective element, a refractive element and a totally internal reflection element. Said orientation renders that light from the light source essentially only is directed towards the target area and hence resulting in the optical device according to the invention to be relatively efficient as light losses due to light falling outside the target area are counteracted. Furthermore, because the shaping elements of the first optical layer face away from the second optical layer, hence when combined with a light source then face towards the light source, it can be avoided by a favourable orientation of each individual shaping element with respect to the light source, that light from the light source impings on the first optcial layer at relatively sharp angles. Thus a reduction in the level of undesired Fresnel reflection, and hence a further reduction in light losses is attained. The non-scattering renders that light issued from the optical device is not diffuse but that relatively sharp, detailed beam patterns can be issued from the optical device. It is thus enabled by the optical device according to the invention to reshape a relatively diffuse, inhomogeneous, round, light beam with a Lambertian light distribution, for example as issued from a LED light source, into a uniform, re-shaped, for example rectangular, light beam with a sharp perimeter.

Essentially, all the shaping elements of each of the optical layers are non-scattering, yet, per optical layer a small portion, for example up to at the most 20%, of a total area formed by all the shaping elements of the respective optical layer may be scattering, for example to smoothen the (perimeter of the) sharp, detailed beam patterns, if so desired. Alternatively, smoothening can be obtained by slightly roughening the surfaces of the shaping elements. Uniform in this respect means that the light intensity of a respective unit area, for example a fraction of 0.1% or 0.01% of the cross-sectional area of the light beam pattern, mutually differences from the light intensity of another unit area at the most by a factor two, preferably at the most by 50%, even more preferably at the most by 15%. The human eye can relatively easily correct for a difference in light intensity of a factor two . The optical device performs its function particularly well when the shaping elements are microstructures, in other words are microsized, i.e. each individual microsized shaping element has in at least one direction a smallest dimension in the range of about 0.0001-1 mm, typically in a range of about 0.001-0. lmm. A specific arrangement of the microsized shaping elements can form a higher structure of micro-sized shaping elements, for example a spiral, a line or a ring-shape. A number of arranged higher structures can form a superstructure of micro-sized shaping elements, for example a number of concentric, ring- shaped higher structures, a square/rectangle comprising a number of line-shaped higher structures, or even a checker-board pattern comprising a number of said squares.

Generally each optical layer is flat or slightly curved, but yet can be considered to lie substantially in a respective (curved) plane. Preferably, for relatively simply, mutually matching and/or alignment of the shaping elements between the various optical layers, the planes of the various optical layers extend substantially mutually parallel, substantially in the sense that the curvature of the plane can mutually differs by a few degrees, for example up to 5, 10 or 20 degrees. Furthermore, the optical layer can have several embodiments, for example as a film on a carrier substrate, a flexible foil or a sheet, as a pressed/embossed or laser-ablated structure in a rigid panel or plate.

The spacing between the first optical layer and the second optical layer generally is chosen such that light from the first optical layer is uniformly distributed when it reaches the second optical layer, said spacing generally being in the range of 1 to 50 mm.

Pre-shaping of light will be explained by means of an example having a rotationally symmetric structure of shaping elements.

A first optical layer is designed that contains a (cut-out of) rotationally symmetric structure of shaping elements. This shaping elements structure is defined such that the rotationally symmetric (extension of the) optical layer delivers a rotationally symmetric target distribution that "draws the rough contour" or the pre-shaped light which, for example, consists for about 90% of the desired shape of the target distribution. The term outer circle of a geometric shape is defined as the smallest circle that contains the surface area of said shape, and the term inner circle of a geometrical shape is defined as the largest circle that completely falls inside the surface area of said geometrical shape. It can be the case that said geometrical shape has a relatively large bump or indentation. To capture the notion of an outer and inner circle in which such an indentation or bump is dealt with, an n₀%-outer circle and ¾%-inner circle are defined. The n₀%-outer circle of a geometric shape is the smallest circle that contains n% of the area of that shape. The ¾%-inner circle of a geometric shape is the largest circle of which the perimeter falls for n% inside that geometry, n (¾,,¾) generally is about 90, but can have any other selected value which consists of the geometrical shape to a sufficient extent, for example n can be 70, 80, 95, 98 or 100. Subsequently, for light that has been pre-shaped by the first optical layer, the second optical layer is used to the tweak the pre-shaped light beam into the desired target distribution, preferably by using refractive shaping elements only.

An embodiment of the optical device is characterized in that it comprises a third optical layer, which is spaced from the first and second optical layer and which is configured to subsequently collimate the beam of uniform, end-shaped, condensed light into a further condensed beam of uniform, end- shaped, collimated light, preferably the further condensed beam is a parallel beam. Thus it is enabled to generate sharp, detailed beam patterns, which both in the near field and in the far field have about the same beam width and/or to generate beams having very small beam angles, for example 3°, 7°, 12° or 16° at FWHM.

An embodiment of the optical device is characterized in that the first optical layer comprises both refractive and TIR shaping elements. Compared to an optical layer with only TIR shaping elements, the combination of TIR and refractive shaping elements in an optical layer renders the advantage that light from the light source that impinges relatively transverse onto the plane of said optical layer, i.e. on that part of the optical layer that is directly opposite to the light source, can easily be accurately redirected via a relatively simple refractive shaping elements, but which would require relatively complex, vulnerable TIR elements which additionally would be difficult to be accurately manufactured. Compared to an optical layer with only refractive shaping elements, by TIR shaping elements the use of optical devices is enabled on which light from the light source impinges at relatively acute angles with the plane of the optical layer and yet light to propagate from the first optical layer in a direction at least almost normal to said plane. Refraction occurs at an interface between materials having a different index of refraction. The larger said difference in index of refraction, the larger the angle over which the light can be redirected via refraction at said interface. However, for each material there is a boundary angle over which light can be redirected via refraction only, for example refractive structures are not able to redirect light impinging at acute angles with a plane in a direction almost perpendicular to said plane, while via TIR this is still possible. Yet in the optical device of the invention for TIR to occur, the light will be refracted first as the light has to pass the interface between two materials to enter the material for subsequent redirection via TIR at internal surfaces. In other words, in the optical device of the invention light first has to pass the interface between two materials for being redirected either via refraction or via TIR. Hence, reflection at said interface upon entering the high refraction index material should be avoided as much as possible. Therefore the first optical layer preferably comprises both refractive and TIR shaping elements which are specifically arranged in the first optical layer, such that angle of incidence with respect to the normal of a respective light entrance surface of said elements is below a chosen maximum angle. This maximum angle is dependent on the index of refraction of the material used for refraction/TIR reflection, but can be set maximally at an angle for which the reflection coefficient for light upon entering the material is 20% for unpolarized light. Hence, for example for water said maximum angle then is 74°, for PMMA 72°, and for diamond 55°.

In a system with a centrally positioned light source with respect to the optical device, the optical device in its central part then has refractive shaping elements, for example in that the central part is a non- imaging Fresnel lens with flat surfaced segments/shaping elements, and at its outer parts has, for example, flat surfaced TIR shaping elements. The flat shape of the individual shaping elements renders the shaping elements to be free from having a focal point. Thus an advantageous, relatively compact and yet efficient illumination system, such as a compact lighting device, is enabled in which the light source is positioned in front of and relatively close to the first optical layer and yet the angle of incidence with respect to the normal of a respective light entrance surface of said shaping elements is below the chosen maximum angle. Hence, preferably the shaping elements of the first optical layer each have a respective light entrance surface configured to face a light source, wherein a maximum incident angle Θ of light with the normal of said light entrance surface is such that at said surface 20% or 10% reflection of unpolarized light is not exceeded. For water with an index of refraction n~1.33 then Θ~74° (for less than 20% reflection) respectively 66° (for less than 10% reflection), for material with an index of refraction n~l .50, like PMMA, then Θ~72° respectively 64°, and for example for a material with a relatively high index of refraction such as diamond n~2.42, the Θ~55° for less than 20% reflection. Less than 10% reflection does not occur at diamond (for a diamond - air interface).

An embodiment of the optical device is characterized in that the second optical layer comprises solely refractive shaping elements. As the first optical layer already has condensed the original light beam from the light source into directions close to the normal of the plane, the condensed beam impinges on the second optical layer at angles well lower than the maximum angle and that can suitably be managed and redirected via refraction. Instead of a second optical layer comprising both refractive and TIR shaping elements, a more simple manufacture of a second optical layer comprising only refractive shaping elements is enabled.

An embodiment of the optical device is characterized in that the first and second optical layer form opposite faces of a (single) sheet. Thus an even more compact optical device enabled which is not only simpler, but also involves less material costs, less complex assembling of the first and second optical layer, and has less weight compared to an optical device in which the first and second optical layer are on separate sheets.

An embodiment of the optical device is characterized in that the first optical layer is a rotationally symmetric optical structure around an optical axis or a cut-out part of a rotationally symmetric optical structure. Such a rotationally symmetric optical 3D-design is relatively easy to design through rotation around the (vertical) optical axis of a simple ID- design. Such rotationally symmetric optical structures, or cut-out parts thereof, are particularly suitable for use in combination with a point light source such as a LED or a closely spaced arrangement of several LEDs, to generate very well-defined, rotationally symmetric, far- field light distributions as end-shaped beams, for example beams with a 2- fold, 3-fold, 4-fold, 6-fold, 8-fold or 12-fold symmetry. Preferably, each individual light source is then to be combined with a respective optical device.

To obtain rotationally symmetrical end-shaped beams, both the light source and its associated optical device, i.e. all the optical layers, are aligned on the same optical axis. Thus various kinds of modular luminaires are envisaged that comprise one or more lighting devices mounted in/on a housing or carrier, which lighting device is a combination of a LED source with an associated optical device according to the invention, whether or not with mutually aligned light sources and optical devices. Thus the invention further relates to a lighting device comprising an optical device according to the invention and a light source positioned in front of the first optical layer, preferably a lighting device wherein the light source and the optical layers are mutually aligned on the same optical axis. The invention further relates to a luminaire comprising at least one lighting device according to the invention.

If a target distribution is desired that is not rotationally symmetric in the far field or on a plane at finite distance and parallel to the foil, and yet the starting point is a

(more or less) rotationally symmetric light source (e.g. LED), the design for the optical layers can then be realized as follows:

A first optical layer is designed that contains (a cut-out of) rotationally symmetric structure of shaping elements, as described above, and that is structured on only one side. This shaping elements structure is defined such that the rotationally symmetric (extension of the) optical layer delivers a rotationally symmetric target distribution that "draws the rough contour" or the pre-shaped light which, for example consists of about 90% of the desired target distribution.

The aspect of pre-shaping has already been explained at the hand of an inner circle or outer circle that draws up the rough contour of the pre-shaped light. The tweaking by the second optical layer, which has a rotationally asymmetric structure for obtaining the asymmetric target distribution, involves that the rough contour of the shape (or pre-shaped light), i.e. the inner circle or outer circle that consists of >= n% the desired target shape of the light beam, is then transformed from the inner/outer circle shaped beam into the desired target shape beam. Under these circumstances of the rough contour already drawn up by the first optical layer, the pre-shaped light can then easily be tweaked into the desired end-shaped light by the second optical layer, for example via refraction only. The design of the rotationally asymmetric second optical layer can be simplified and hence design costs can be saved in an embodiment of the optical device when the optical layers are mutually aligned on an optical axis and/or when the second optical layer comprises only refractive shaping elements.

EP2157359A2 discloses an artificial light source generator of relatively large size along the projection direction because of comrpising a parabolic reflector lamp, and further comprising an optical device with a first lens array with lenses facing towards a second lens array, the distance between the first and second lens array is 0.5 to 1.5 times the focal distance of the lenses of the first lens array.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be elucidated further by means of the schematic drawing, which may not be up to scale and in which some dimensions may be exaggerated for the sake of clarity, in which:

Fig. 1 shows a first embodiment of a lighting device according to the invention;

Fig. 2 shows a second embodiment of a lighting device according to the invention;

Figs. 3A-3E show illumination patterns of the various optical layers as well as the definition of specific parameters;

Figs. 4A-4B show Fresnel reflectivity curve and TIR range for PMMA; Figs. 5A-C show details of a first optical layer and principles of refraction and

TIR;

Fig. 6 shows an embodiment of a luminaire comprising a number of lighting devices according to the invention; and

Fig. 7 shows a far field distribution of a spot beam as obtained from a respective lighting device of the luminaire of Fig. 6.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows a first embodiment of a lighting device 1 according to the invention, comprising an optical device 3 spaced along an optical axis 25 from a light source 15 at a distance Dl of 3 mm, Dl typically being in a range of 1 to 10 mm. Said optical device comprises a first 5 and second optical layer 7 mutually spaced along the optical axis by a distance D2 of 25 mm, D2 typically being in a range of 0.1 to 40 mm. 0.1mm particularly could be the case when the first and second layer are combined into one (thin) sheet. The first optical layer is a microstructured foil comprising refractive 9 and total internal reflection (TIR) purposely oriented, non-scattering shaping elements 11. By the optical device, light source light 13 from the light source 15 is transformed into a beam of uniform, pre-shaped light 17 by the first optical layer. Subsequently said beam of uniform, pre-shaped light is tweaked into a beam of uniform, end-shaped, condensed light 19 by the second optical layer. The second optical layer is a microstructured foil comprising only refractive shaping elements for the transformation of the light. The light source in Fig. 1 is a blue LED with remote phosphor for generating white light. Alternatively, the light source could be a compact set of red, green, blue and amber (= RGBA) LEDs or a point-size like halogen incandescent or high intensity gas discharge lamp, for example a UHP lamp.

Fig. 2 shows a second embodiment of a lighting device 1 according to the invention. Compared to the lighting device of Fig.1, the second embodiment further comprises a third optical layer 21 which subsequently (further) collimates the beam of uniform, end-shaped, condensed light 19 into a parallel beam of uniform, end-shaped, collimated light 23. The third optical layer is a microstructured foil comprising only refractive shaping elements for the final transformation of the light. The third optical layer is spaced along the optical axis 25 from the (first and) second optical layer by a distance D3 of 10 mm, D3 typically being in the range of 1 to 50 mm.

Fig. 3A is a cross sectional view of IIIA of the lighting device of Fig. 2 and shows the illumination pattern as issued by the light source and impinging on the first optical layer 5. As is shown, the light source issues an inhomogeneous, unshaped, Lambertian beam of light source light 13 towards the first optical layer, with a central bright spot 27, i.e. around the optical axis 25, and with decreasing luminous intensity in radial direction away from the optical axis.

Fig. 3B is a cross sectional view of IIIB of the lighting device of Fig. 2 and shows the illumination pattern as issued from the first optical layer and impinging on the second optical layer 7. As is shown, the inhomogeneous illumination pattern/beam as issued by the light source (see Fig. 3A) is transformed by the first optical layer into a pre-shaped, uniform beam 17 which forms the rough contour 29, i.e. outer circle, consisting for about 70% of the desired end-shaped light beam.

Fig. 3C is a cross sectional view of IIIC of the lighting device of Fig. 2 and shows the illumination pattern as issued from the second optical layer and impinging on the third optical layer 21. As is shown, the homogeneous illumination pattern/beam as issued from the first optical layer (see Fig. 3B) is transformed by the second optical layer into an end-shaped, uniform, condensed beam 19 which has the desired shape 31 of the end-shaped light beam. The third optical layer further collimates the end-shaped, uniform, condensed beam further into an end- shaped, uniform, parallel beam (not shown). As shown in the combined Figs 2 and 3A-C, the inhomogeneous, unshaped, Lambertian beam of light source light is transformed in three steps by the optical device into a parallel beam of uniform, end- shaped, collimated light.

Fig. 3D-E show the definition of specific parameters used for determining the rough contour/pre-shape 29 of the uniform, pre-shaped light beam. The term outer circle 33 of a geometric shape 31 is defined as the smallest circle that contains the whole surface area 41 of said shape, and the term inner circle 35 of the geometrical shape is defined as the largest circle that completely falls inside the surface area of said that geometrical shape.

However, in Figs. 3D and 3E said geometrical shape contains a relatively large indentation 37 respectively bump 39. To capture the notion of an outer and inner circle in which such an indentation or bump is dealt with, an n₀%-outer circle and ¾%-inner circle are defined. The n₀%-outer circle of a geometric shape is the smallest circle that contains n% of the area of that shape. The ¾%-inner circle of a geometric shape is the largest circle of which the perimeter falls for n% inside that geometry, n generally is about 90, but can have any other selected value which captures the geometrical shape to a sufficient extent, for example n can be 70, 80, 95, 98 or 100. Fig. 4A-4B show Fresnel reflectivity curve and TIR range for the interface air - PMMA. The proportion of light reflected is dependent on the incident angle from normal, i.e. as shown in the reflectivity curve 47 for different angles of incidence in Fig. 4A, the flatter the angle at which the light falls on the surface (the larger angle with the normal to the surface) the greater the amount of light is reflected. The table 1 below demonstrates the proportion of the reflected light in relation to the angle of incidence for diamond.

Table 1. The dependence of the proportion of the reflected light to the angle of incidence for diamond.

When the light falls perpendicularly onto a surface the major part of it penetrates through the surface into the material. The intensity of the incidence at right angles does not sink to zero, but retains a residual quality Ro, as is apparent from Fig. 4A and from table 1. Ro is termed luster intensity, and is dependent solely on the refractive index (= n) according to the equation: Ro = {(n-1) / (n+1)}² , some examples for R_<,:

diamond n = 2.42. Thus the equation reads Ro = {(1.42) / (3.42)}² = 0.1723 =

17.23%

PMMA n = 1.5, hence Ro = {(0.5) / (2.5)}² = 0.04 = 4%

water n = 1.33, hence Ro = {(0.33) / (2.33)}² = 0.02 = 2%

The smaller n, the smaller Ro, however the less the angle over which the light can be redirected via refraction. Hence, an optimum has to be found between the desired maximum angle via refraction and Ro, Poly-methylene-meta-acrylate (PMMA) with n = 1.5, Polyethylene (PE) with n = 1.51 , Poly-carbonate (PC) with n = 1.58 and Ply-propylene-carbonate (PPC) with n= 1.46 are considered as suitable materials for the optical layers in the optical device of the invention.

With respect to TIR Fig. 4B shows the curve 49 of the dependency of the reflectivity for the PMMA - air interface at the internal surface of PMMA. As shown in Fig. 4B total internal reflection occurs at the critical angle of about 42° and higher angles with the normal to the internal surface.

Fig. 5A shows a schematic cross sectional view of a first optical layer 5 positioned opposite to a light source 15, in the figure a set of RGB-LEDs. A sheet 55 of PE has the first optical layer comprising shaping elements 11 provided at a first major surface 51, which first major surface faces away from the second optical layer (not shown in the figure) and hence faces towards the light source. The sheet 55 has a second major surface 53 facing away from the light source. The first major surface has two areas, a central area 43 directly opposite to the light source having refractive, microsized shaping elements 9, and a border/outer area 45 where microsized TIR shaping elements 11 are located. The microsized shaping elements each have two facet surfaces 63a, 63b (see Figs. 5B, 5C), In at least in one direction, a smallest dimension of the microsized shaping element typically is at the most 0.1mm, in the figure said smallest dimension is about 0.04 mm. In the embodiment shown in Fig. 5A, the first optical layer is on a separate sheet from the second optical layer, however, in an alternative embodiment of the optical device, the second optical layer is at the second major surface 53 of sheet 55, hence on the same, single sheet as the first optical layer.

Fig. 5B shows a detail of the central area, i.e. the refractive part, of the first optical layer of the sheet 55 of Fig. 5 A. A light ray 57 impinging on a facet 59 of a refractive shaping element 9 is refracted towards the normal 61 of a sloped facet surface 63a, i.e. of its light entrance surface, and refracted away from the normal to the second major surface when crossing the interface from PE to air. Due to the facet light entrance surface having a slope angle γ with the plane 65 of the first optical layer (i.e. plane of the sheet) the light ray is deflected/redirected when exiting the sheet via the second major surface, i.e. the light exit surface of the sheet that extends parallel to the plane of the sheet. There are, however, limits to the choice of said slope angle of the light entrance surface of the facet (i.e., the facet's normal) and the ray deflection that can be achieved. For instance, if in Fig. 5B a decrease in a is desired, this cannot be realized by increasing the slope γ since the light ray already makes an almost 90 degree angle with the normal of the facet, hence, another mechanism than refraction is required. In Fig. 5C it is shown that this desired further decrease in a is obtainable via TIR. Fig. 5C depicts a TIR structure with TIR shaping elements 1 1 for a 2D case. The TIR shaping element has a triangular shape defined by the angles Bi and B₂ that its two facet surfaces 63a,63b make with the plane 65 of the micro-structured sheet 55. The light ray 57 enters the TIR shaping element via facet light entrance surface 63 a by refraction. Next, it reflects at its other facet side 63b by TIR. In this way, a large and efficient deflection of the light can be realized. Besides being able to realize deflections that cannot be realized by a facet at that same location, a TIR structure can also be preferred over a refractive structure because it may result in less chromatic dispersion.

Fig. 6 shows an embodiment of a luminaire 67 comprising a number (three) of lighting devices 1 according to the invention. The lighting devices are electrically connected and mounted on a carrier/rail 69 which via a control circuit 71 is electrically connected and powered to mains voltage. Each lighting device comprises a respective light source (not shown) and a respective optical device 3 of which only the plate with the third optical layer is visible. Each lighting device issues a respective light beam in a respective direction. At least one of the light beams as issued by one of the lighting devices in Fig. 6 has a far field distribution 73 of a spot beam as shown in Fig. 7. The spot beam is a parallel light beam with a very narrow beam width, i.e. its Full Width at Half Maximum (= FWHM) 75 is only about

Claims

CLAIMS:

1. An optical device comprising a mutually spaced first and second optical layer, each comprising reflective, refractive and/or total internal reflection (TIR) purposely oriented, non-scattering shaping elements, the shaping elements of the first optical layer facing away from the second optical layer,

the optical device being configured to:

transform light from a light source into a beam of uniform, pre-shaped light by the first optical layer, and subsequently

fine-tune and condense said beam of uniform, pre-shaped light into a beam of uniform, end-shaped, condensed light by the second optical layer.

2. An optical device as claimed in claim 1, characterized in that it comprises, spaced from the first and second optical layer, a third optical layer configured to

subsequently collimate the beam of uniform, end- shaped, condensed light into a further condensed beam of uniform, end- shaped, collimated light, preferably a parallel beam of uniform, end-shaped, collimated light .

3. An optical device as claimed in claim 1 or 2, characterized in that the first optical layer comprises both refractive and TIR shaping-elements.

4. An optical device as claimed in claim 1, 2, or 3, characterized in that the second optical layer comprises solely refractive shaping-elements.

5. An optical device as claimed in claim 1, 2, 3, or 4, characterized in that the first and second optical layer form opposite faces of a (single) sheet.

6. An optical device as claimed in claim 1, 2, 3, 4, or 5, characterized in that the shaping elements of the first optical layer each have a respective light entrance surface configured to face a light source, wherein a maximum incident angle Θ from normal of said light entrance surface is such that 20% reflection of unpolarized light is not exceeded.

7. An optical device as claimed in claim 1, 2, 3, 4, 5 or 6, characterized in that the first optical layer is a rotationally symmetric optical structure around an optical axis or a cut-out part of a rotationally symmetric optical structure.

8. An optical device as claimed in anyone of claims 1 to 7, characterized in that shaping of the beam of end-shaped light is contained by the first optical layer for >=90% in the shaping of the pre-shaped light.

9. An optical device as claimed in anyone of claims 1 to 8, characterized in that the optical layers are mutually aligned on an optical axis.

10 An optical device as claimed in anyone of claims 1 to 9, characterized in that the shaping elements are flat surfaced.

11. An optical device as claimed in anyone of the claims 1 to 10, characterized in that essentially all shaping elements are non-scattering.

12. A lighting device comprising an optical device as claimed in anyone of claims 1 to 11 and a light source positioned in front of the first optical layer.

13. A lighting device as claimed in claim 12, characterized in that the light source and the optical layers are mutually aligned on an optical axis.

14. A lighting device as claimed in claims 12 or 13, characterized in that the light source is a point light source positioned on an axis and the first optical layer is a rotationally symmetric optical structure around said axis.

15. A luminaire comprising a lighting device as claimed in anyone of the claims

12 to 14 which are mounted in/on a housing or carrier.