FIELD OF THE INVENTION

The invention relates to a lens. The invention further relates to a light generating system comprising the lens. The invention further relates to a light generating device comprising the light generating system.

BACKGROUND OF THE INVENTION

Linear lenses are known in the art. For instance, US2016238202A1 describes an optical element for dispersing light from a plurality of linearly aligned LEDs including a body made of a transparent polymeric material, in which the body has a longitudinally extending center portion having a transverse cross-sectional profile that is uniform along the length of the optical element, and legs extending away from opposite sides of the center portion and extending downwardly to define a recess. The center portion has a top surface and a bottom surface that together define a longitudinally extending lens portion that collects light from the LEDs and refracts the light to produce a desired beam pattern. Uniformly and closely spaced apart transverse grooves can be provided on the top surface of the longitudinally extending lens portion to uniformly spread light on an illuminated surface and eliminate the appearance of dark and light areas on the lens portion when it is illuminated by the LEDs.

SUMMARY OF THE INVENTION

Linear lens designs provide freedom in the number of light sources, such as LEDs, and the position of these light sources along the lens axis. This design freedom may facilitate re-use of the optical component in different product generations, such as those following the LED roadmap. This in turn may translate to a reduction in development cost and time. Furthermore, a linear lens may allow the placement of multiple light sources, with (for example) different spectra, very close together, which may improve color uniformity, both in near field (illuminance) and in far field (intensity). Finally, linear lenses may often be cheaper to produce than 3D freeform lenses and may thus be an attractive option. However, the linearity may also be a restriction making it harder to control the light beam with a linear lens. When the linear lens is used to illuminate, e.g., a ceiling, then at the ends unwanted (pointy) artefacts may appear due to the limited control of the beam in the direction along the lens axis. As a result, unappealing bright spots or stripes may appear at the ceiling and possibly also at adjacent walls (also see below).

These artefacts may a result of that for a linear lens, there may always be direction(s) along which the source is exactly in focus. In those directions, sharp focus peaks may be formed.

The typical peaks in the beam produced by the linear lens may also cause light to end up as sharp spots or stripes on the wall, while there is almost no light hitting the wall when, for example, a peanut lens array is used instead. Moreover, far field intensity plots of the two designs may also look quite different; the linear lens beam may be far wider, especially in the directions close to the direction of the lens axis.

Hence, it is an aspect of the invention to provide an alternative lens, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Hence, in a first aspect, the invention may provide a lens having a lens length L parallel to a cylindrical axis, especially a modulated linear lens. The lens may have a lens surface shaped according to a lens surface shape, especially wherein the lens surface shape is defined in a cylindrical coordinate system by y, 9, and R. Specifically, y may be (or “indicate”) an axial position (or “axial coordinate”) along the cylindrical axis, 9 may be (or “indicate”) an angular position (or “angular coordinate”) with respect to the cylindrical axis, and R may be (or “indicate”) a radial distance to the cylindrical axis. Hence, in embodiments, the lens surface shape may be defined by axial position y, angular position 9, and radial distance R. In further embodiments, the lens surface shape may have a local average radius R (depending on axial position ). In further embodiments, R may be defined according to:

In such embodiments, Ay may especially be selected from the range of 1 - 199 mm and wherein is a position along the cylindrical axis. In further embodiments, along at least 89% of the cylindrical axis may apply that (a) for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis for Ay, wherein Ci < 9.3; and (b) for a first angular position 91, R differs by at least RA * C2 between a first axial position yl (i.e., =yl) and a second axial position y2 ( =y2) wherein C2 > 0.03, and wherein RA is an average value of R for the first angular position 91 (along the cylindrical axis).

The lens provided by the invention may especially be a modulated linear lens. In particular, the lens may be locally smooth, which may be beneficial with regards to avoiding large differences between intensity distributions of neighboring light sources, but may be (substantially) modulated along the lens axis to smooth out focus directions. Thereby, above-mentioned sharp focus peaks may be avoided, resulting in a more desirable illumination region (also see below). In particular, the local smoothness may be beneficial as thereby the produced overall intensity may be relatively robust (or “insensitive”) to small changes in the (positions of the) light source(s), such as LEDs, facilitating more consistent performance, and providing compatibility with a larger selection of light source arrays, such as with light source arrays with varying numbers of light sources and varying pitches.

In particular, the invention may relate to adding a modulation to a linear lens along the lens axis to mitigate bright spots, stripes, and/or focus peaks, while maintaining the attractive features of linear lenses: the number of light sources may be varied without the need for redesigning the optics, the sources may be placed close together, and the optic may still be a single component.

In specific embodiments, the invention may provide a lens, wherein the lens has a lens surface shaped according to a lens surface shape, wherein the lens surface shape is defined in a cylindrical coordinate system by y, 9, and R, wherein y is an axial position along a cylindrical axis, wherein 9 is an angular position with respect to the cylindrical axis, and wherein R is a radial distance to the cylindrical axis, wherein the lens surface shape has a local average radius R, wherein: wherein Ay is selected from the range of 1mm - 199mm, and wherein along at least 89% of the cylindrical axis applies that: (a) for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis for Ay, wherein Ci < 9.3; and (b) for a first angular position 91, R differs by at least RA * C2 between a first axial position yl and a second axial position y2 wherein C2 > 9.93, and wherein RA is an average value of R for the first angular position 91.

Hence, the invention may provide a lens, especially a (modulated) linear lens. The term “linear lens” may especially refer to an elongated lens configured to be functionally coupled with an array of (linearly arranged) light sources. In particular, the linear lens has an axis of elongation, which is parallel to the cylindrical axis or may coincide therewith. Especially, in embodiments, the cylindrical axis may be the axis of elongation. In further embodiments, the (linear) lens may have a lens length L, especially parallel to the cylindrical axis, and a lens width W perpendicular to the lens length L, especially wherein the lens width is a largest lens width Wl, or especially wherein the lens width is an average lens width. In further embodiments, L/W > 10, such as > 25, especially > 50. In further embodiments, L/W

< 10000, such as < 1000.

In further embodiments, the lens may have an optical axis O, especially wherein the length L and the lens width W may (both) be (essentially) perpendicular to the optical axis O. Hence, the optical axis O may especially be (essentially) perpendicular to the cylindrical axis.

Hence, the lens may have a lens length L that is substantially longer than a (largest or average) lens width W. However, the lens width may vary along the cylindrical axis in view of the modulation. In embodiments, the lens may thus have a largest lens width W 1 (perpendicular to the lens length L) and a smallest lens width W2 (perpendicular to the lens length L). In further embodiments, Wl < 100 mm, such as < 80 mm, especially < 60 mm. In further embodiments, W2 > 1 mm, such as > 3 mm, especially > 5 mm. In further embodiments, W2 > 8 mm, such as > 10 mm, especially > 12 mm. In further embodiments, W1/W2 > 1.03, such as > 1.05, especially > 1.1, such as > 1.3. In yet further embodiments, W1/W2 > 2, such as > 3, especially > 5. In further embodiments, W1/W2 < 20, such as < 15, especially < 10, such as < 5. In yet further embodiments, W 1/W2 < 3, such as < 2, especially

< 1.75.

Hence, in embodiments, the width (and thereby the radius of an outer lens surface) may be modulated along the cylindrical axis, i.e., the width of the lens may vary along the cylindrical axis. In further embodiments, the width of the lens may remain (essentially) the same along the cylindrical axis, while the radius of a lens surface (for one or more angular positions) may vary along the cylindrical axis.

In particular, the term “modulated linear lens” may herein especially refer to a linear lens of which a lens surface varies cross-sectionally along the cylindrical axis, i.e., a cross-sectional view of the lens perpendicular to the cylindrical axis changes when sliding the cross-section along the cylindrical axis.

Hence, the lens may have a lens surface shaped according to a lens surface shape. In particular, in embodiments, the lens surface may approximate the lens surface shape. In further embodiments, the lens surface may define the lens surface shape. In embodiments, the lens surface shape may have a cylindrical axis. In particular, the lens surface shape may be defined with respect to the cylindrical axis in a cylindrical coordinate system. The cylindrical axis may especially be parallel to an axis of elongation of the lens. In embodiments, the axis of elongation may be the cylindrical axis.

The term “approximate” and its conjugations herein, such as in “to approximate a lens surface shape”, refers to being nearly identical to, especially identical to, the following term, for example to a lens surface shape. For example, a lens surface may have a shape that is nearly identical to the lens surface shape, but for a defect. In particular, an object approximating a first shape may herein refer to: a first shape realization encompassing the object, wherein the first shape realization is defined as the smallest encompassing shape of the (2D or 3D, respectively) object wherein the first shape realization has the shape of the first shape, wherein a ratio of the area (volume) of the first shape realization to the area (volume) of the object is < 1.1, such as <1.05, especially <1.02, such as < 1.01, including 1. Further, especially if the dimensions of the first shape are defined, the term approximate may refer to the object and the first shape being superimposable (in 2D or 3D, respectively) such that an intersection between the object and the first shape covers at least s% of the object and at least s% of the shape, wherein s is at least 90%, such as at least 95%, especially at least 98%, such as at least 99%, including 100%.

The lens may especially comprise a concave inner lens surface and a convex outer lens surface, either of which (or both of which) may be modulated to provide the modulated linear lens. Hence, in embodiments, the lens surface shape may comprise an inner lens surface shape, especially wherein the lens surface comprises a concave inner lens surface shaped according to the inner lens surface shape. In further embodiments, the lens surface shape comprises an outer lens surface shape, especially wherein the lens surface comprises a convex outer lens surface shaped according to the outer lens surface shape.

The lens surface shape, especially the inner lens surface shape, or especially the outer lens surface shape, may, in embodiments, be defined in a cylindrical coordinate system. In particular, the cylindrical coordinates y, 9, and R may define the lens surface shape in the cylindrical coordinate system, especially wherein y indicates an axial position along a cylindrical axis, wherein 9 indicates an angular position (with respect to the cylindrical axis), and wherein R indicates a radial distance (to the cylindrical axis). The cylindrical axis may especially be arranged in parallel to the length of the lens. In particular, the lens may have an axis of elongation, wherein the axis of elongation is the cylindrical axis in the cylindrical coordinate system. The lens surface shape may have a local average radius R, which is the average radius of the lens surface shape for a (narrow) band (of length Ay) between axial locations ^-Ay/2 and ^+Ay/2, i.e., around axial location S, and for a given value of 0.

In particular, the lens surface shape may have a local average radius R, wherein:

In embodiments, Ay may especially be selected from the range of 0.5 - 150 mm, especially from the range of 1mm - 100 mm, such as from the range of 2 - 50 mm. In further embodiments, Ay may be at least 1 mm, such as at least 2 mm, especially at least 5 mm, such as at least 10 mm. In further embodiments, Ay may be at most 100 mm, such as at most 50 mm, especially at most 30 mm, such as at most 20 mm.

It will be clear to the person skilled in the art that the local average radius R may not be defined at an end of the lens surface shape (along the cylindrical axis), as either y-Ay/2 or y+Ay/2 would lie outside of the lens surface shape. Hence, the (local) smoothness of the lens and the (global) modulation are hereinafter defined to be satisfied along at least a lens surface section. The lens surface section may comprise at least 70% of the lens surface shape along the cylindrical axis, such as at least 80%, especially at least 90%, such as at least 95%.

In particular, the lens surface shape may have a minimal axial position ymin and a maximal axial position y _ma x arranged at opposite ends of the lens along the cylindrical axis, wherein position S, is arranged between the minimal axial position and the maximal axial position y _ma x, especially wherein S, is arranged at a distance of at least Ay from the minimal axial position ymin, and especially wherein S, is arranged at a distance of at least Ay from the maximal axial position y _max .

As indicated above, the lens may be locally smooth, i.e., locally the modulation may be smooth. Hence, in embodiments, along the lens surface section may apply that for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis for Ay, i.e., for each value of 9, any two points arranged at a distance of Ay along the cylindrical axis may differ in local average radius R by at most Ci*Ay. In further embodiments, Ci < 0.4, especially < 0.3, such as < 0.25. In further embodiments, Ci < 0.2, such as < 0.15, especially < 0.1.

Hence, in further embodiments, along the lens surface section, may apply that: However, as also indicated above, the lens may be (substantially) modulated along the cylindrical axis. Hence, in embodiments, along the lens surface section may apply that for a first angular position 91, R differs by at least RA * C2 between a first axial position yl and a second axial position y2, wherein RA is an average value of R (along the cylindrical axis) for the first angular position 91, i.e., there exists a value of 9 (91) for which the modulation along the cylindrical axis exceeds C2 times the average radius for that value of 9. In further embodiments, C2 > 9.92, such as > 9.93, especially > 9.935. In further embodiments, C2 > 9.94, such as > 9.95, especially > 9.98. In further embodiments, C2 > 9.1, such as > 0.15, especially > 0.2. In further embodiments, C2 < 1, such as < 0.7, especially < 0.5, such as < 0.4.

Hence, in further embodiments, along the lens surface section may apply that

In further embodiments, there may be at least n first axial positions yl and n second axial positions y2, for which applies that at the first angular position 91, R differs by at least RA * C2 between any one of the first axial positions yl and any one of the second axial position y2, especially wherein n > 3, especially n > 5, such as n > 10. For instance, in embodiments, the modulation along the cylindrical axis may (partially) have a wave shape, such as a sine shape.

Hence, the lens may be locally smooth but may be (substantially) modulated along the cylindrical axis (at the first angular position). In particular, in embodiments, C2 * RA > Ci * Ay, such as C2 * RA > 2 * Ci * Ay, especially C2 * RA > 5 * Ci * Ay, such as C2 * RA > 10 * Ci * Ay. In further embodiments, C2 * RA > 20 * Ci * Ay, such as C2 * RA > 50 * Ci * Ay, especially C2 * RA > 100 * Ci * Ay.

In particular, by satisfying both the smoothness and the modulation criteria, the lens of the invention may provide more desirable illumination patterns (also see below).

In specific embodiments, along at least 90% of the lens surface shape along the cylindrical axis applies that: (a) for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis for Ay, wherein Ci < 0.3, especially wherein V0, y : Ay; and that (b) for a first angular position 91, R differs by at least RA * C2 between a first axial position yl and a second axial position y2, wherein C2 > 0.03, especially wherein 3yl, y2, 0i: |R(01,yl) — R(01,y2) | > R^ * C ₂ . In embodiments, the lens surface, especially the lens surface shape, may surround the cylindrical axis, i.e., the angular position 9 may comprise the interval of 0 - 2*7t (0 E [0,2 * TT)). In such embodiments, the lens may have a (modulated) cylindrical shape, and may especially be configured to host a light source array along the cylindrical axis. In general, however, the lens surface, especially the lens surface shape, may only partially surround the cylindrical axis. In particular, in embodiments, (values of) 9 may span the interval of 0 - 9 _ma x, i.e., 0 E [0, 0 _max ], especially wherein 9 _ma x is selected from the range of 0.25*7t - 2*7t, especially from the range of 0.5*7t - 2*7t, such as from the range of 0.5*7t - 1.5*7t, especially from the range of 0.75*7t - 1.25*71. In further embodiments, 9 _max may be (about) 7t.

Especially, in further embodiments, 0 6 [0,2 * TT), especially 0 6 [0,1.5 * TT], such as 0 E [0,1.25 * TT], more especially 0 E [O, TT] .

In embodiments, along the lens surface section may apply that there are a plurality of first angular positions 91 for which R differs by at least RA * C2 between respective first axial positions yl and second axial positions y2, especially wherein C2 > 0.03.

In further embodiments, along the lens surface section may apply that for each angular position 9n, R differs by at least RA * C2 between a (respective) first axial position ynl and a (respective) second axial position yn2, especially wherein C2 > 0.03, and especially wherein RA is an average value of R (along the cylindrical axis) for the (respective) angular position 9n. Hence, in further embodiments, along the lens surface section may apply that: wherein ynl and yn2 are selected from the range of y _m in - y _max .

In particular, and y _max may especially be arranged at a distance of lens length L, i.e., ymin may correspond to a first lens end along the cylindrical axis, whereas y _max may correspond to a second lens end along the cylindrical axis, especially wherein y _max > ymin; hence, in embodiments, L = y _max - ymin. For convenience, the halfway point between ymin and y _max may especially be defined as y=0. Hence, in embodiments Ymin “Ymax.

In further embodiments, there may be at least n (respective) first axial positions ynl and n (respective second axial positions yn2, wherein applies that for each angular position 9n, R differs by at least RA * C2 between any one of the (respective) first axial positions yl and any one of the (respective) second axial positions y2, especially wherein n > 3, especially n > 5, such as n > 19.

In embodiments, the lens surface shape may have radial distances R selected from the range of 9.5 - 159 mm, especially from the range of 1 - 199 mm. In embodiments, the radius of the lens surface shape may especially be defined according to a first component r(9) (dependent on the angular position 9), and a second component p(9,y) (dependent on both the angular position 9 and on the axial position y). Hence, in embodiments, /?(0, y) = r(0) + (0, ). In particular, in embodiments, the first component r(9) may define a constant radius for each angular position, and the second component r(9,y) may define a (angular position-dependent) modulation of the radius along the cylindrical axis.

In embodiments, p(9,y) may define a wave shape along the cylindrical axis. In further embodiments, p(9,y) may define a sinusoidal shape along the cylindrical axis. In further embodiments, the sinusoidal shape may be (at least partially) defined by cos(y), especially wherein Ymin “Ymax. Hence, in embodiments, the wave shape, especially the sinusoidal shape, may be mirrored along the cylindrical axis at y=0.

As indicated above, in embodiments, the inner lens surface may be shaped according to an inner lens surface shape, and the outer lens surface may be shaped according to an outer lens shape. In further embodiments, the inner lens surface shape and the outer lens surface shape may be (essentially) the same shape (but a different size). In general, however, the inner lens surface shape and the outer lens surface shape may be different shapes. Hence, in embodiments, the inner lens surface shape may differ from the outer lens surface shape.

In embodiments, the lens surface may comprise a surface structure, such as surface roughness, a surface texture, and/or a micro-lens. In particular, the lens surface may locally vary, such as due to roughness, at a scale smaller than Ay. Hence, the surface structures may (essentially) have a negligible effect on the local average radius R. In particular, the lens surface may comprise a plurality of (different) surface structures. In further embodiments, neighboring surface structures may be separated by a structure distance of at most Ay, especially at most 9.5* Ay, such as at most 9.2* Ay, (along the cylindrical axis).

In further embodiments, the surface structure may comprise a surface roughness and/or a surface texture, especially a surface roughness, or especially a surface texture. For instance, the surface texture may have been applied by thermal, chemical or mechanical processes, especially by one or more of laser texturing, spark erosion, and sand blasting.

In further embodiments, the surface structure may comprise a micro-lens. In further embodiments, the lens surface may comprise a micro-lens array. In particular, microlenses may be used to shape a light beam in the direction along the cylindrical axis. Hence, in embodiments, the micro-lenses may be configured to shape a light beam along the cylindrical axis.

The lens may, in embodiments, especially be configured to be functionally coupled to a linear light source array, especially configured to be arranged in a light receiving relationship with a plurality of light sources of a linear light source array.

In a second aspect, the invention may provide a light generating system comprising a linear light source array and the lens according to the invention. In embodiments, the linear light source array may comprise a plurality of (linearly arranged) light sources, especially wherein the lens is configured in a light receiving relationship with the plurality of light sources.

In embodiments, the plurality of light sources of the linear light source array may be arranged at a pitch y _p , especially a (constant) pitch y _p along the cylindrical axis. In such embodiments, the relevant distance along the cylindrical axis with respect to smoothness may especially be the average pitch y _a (of pitch y _p ). Hence, in embodiments, y _a > Ay (or Ay < y _a ), especially y _a > Ay (or Ay < y _a ). Hence, in embodiments, the plurality of light sources of the linear light source array may be arranged at an average pitch y _a , wherein y _a > Ay.

In further embodiments, the plurality of light sources of the linear light source array may be arranged at a pitch selected from the group comprising a constant pitch, a linearly varying pitch, and a polynomially varying pitch, especially a polynomially varying pitch.

In embodiments, the pitch y _p may be a constant pitch along the cylindrical axis, i.e., the plurality of light sources are arranged equidistantly. In further embodiments, the plurality of light sources may be arranged at a constant pitch y _p along the cylindrical axis (A).

For instance, in embodiments, the pitch between two consecutive (linearly arranged) light sources in a linear arrangement may be selected from the range of 0 - 100mm, such as from the range of 0.5 - 50 mm. Especially, in further embodiments, each set of two neighboring light sources in the linear arrangement may be separated by a pitch independently selected from the range of 0 - 100 mm, such as from the range of 0.5 - 50 mm.

The light sources in the linear light source array may, in embodiments, be arranged in clusters. For instance, a linear light source array may comprise two different types of light sources, such as two LEDs with different illumination spectra, arranged in clusters, especially wherein each cluster comprises two or more abutted light sources. In such embodiments, the pitch y _p may relate to clusters of light sources rather than individual light sources.

Hence, in embodiments, the linear light source array may comprise a plurality of linearly arranged clusters of light sources, wherein the plurality of clusters are arranged at the pitch y _p .

The pitch y _p may especially be determined based on the central location of (each of) the (clusters of) light sources with respect to the cylindrical axis.

The term “light source” may in principle relate to any light source known in the art. It may be a conventional (tungsten) light bulb, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, a LED (light emissive diode). In a specific embodiment, the light source comprises a solid state LED light source (such as a LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-200 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so- called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module.

The light source has a light escape surface. Referring to conventional light sources such as light bulbs or fluorescent lamps, it may be outer surface of the glass or quartz envelope. For LED’s it may for instance be the LED die, or when a resin is applied to the LED die, the outer surface of the resin. In principle, it may also be the terminal end of a fiber. The term escape surface especially relates to that part of the light source, where the light actually leaves or escapes from the light source. The light source is configured to provide a beam of light. This beam of light (thus) escapes from the light exit surface of the light source.

The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc... The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid-state light source (such as a LED or laser diode). In an embodiment, the light source comprises a LED (light emitting diode). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED). The term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of semiconductor light sources may be configured on the same substrate. In embodiments, a COB is a multi-LED chip configured together as a single lighting module.

The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state light sources. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid-state light source, such as a LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise a LED with on-chip optics. In embodiments, the light source comprises a pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering).

In embodiments, the light source may be configured to provide primary radiation, which is used as such, such as e.g. a blue light source, like a blue LED, or a green light source, such as a green LED, and a red light source, such as a red LED. Such LEDs, which may not comprise a luminescent material (“phosphor”) may be indicated as direct color LEDs.

In other embodiments, however, the light source may be configured to provide primary radiation and part of the primary radiation is converted into secondary radiation. Secondary radiation may be based on conversion by a luminescent material. The secondary radiation may therefore also be indicated as luminescent material radiation. The luminescent material may in embodiments be comprised by the light source, such as a LED with a luminescent material layer or dome comprising luminescent material. Such LEDs may be indicated as phosphor converted LEDs or PC LEDs (phosphor converted LEDs). In other embodiments, the luminescent material may be configured at some distance (“remote”) from the light source, such as a LED with a luminescent material layer not in physical contact with a die of the LED. Hence, in specific embodiments the light source may be a light source that during operation emits at least light at wavelength selected from the range of 380-470 nm. However, other wavelengths may also be possible. This light may partially be used by the luminescent material.

In embodiments, the light generating device may comprise a luminescent material. In embodiments, the light generating device may comprise a PC LED. In other embodiments, the light generating device may comprise a direct LED (i.e. no phosphor). In embodiments, the light generating device may comprise a laser device, like a laser diode. In embodiments, the light generating device may comprise a superluminescent diode. Hence, in specific embodiments, the light source may be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source may comprise an LED.

The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers

The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source. Hence, a white LED is a light source.

The term “light source” herein may also refer to a light source comprising a solid state light source, such as an LED or a laser diode or a superluminescent diode. The “term light source” may (thus) in embodiments also refer to a light source that is (also) based on conversion of light, such as a light source in combination with a luminescent converter material. Hence, the term “light source” may also refer to a combination of a LED with a luminescent material configured to convert at least part of the LED radiation, or to a combination of a (diode) laser with a luminescent material configured to convert at least part of the (diode) laser radiation. In embodiments, the term “light source” may also refer to a combination of a light generating device, like a LED, and an optical filter, which may change the spectral power distribution of the light generated by the light generating device.

The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin. Especially, the term “light source” herein refers to solid state light sources, more especially to LED, diode lasers, or superluminescent diodes, more especially to LEDs.

Further, the term “light source array” may especially refer to solid state light sources of the same bin (though this is not necessarily the case).

Yet further, in embodiments the light source array may comprise a plurality of white emitting LEDs.

The terms “light-receiving relationship” or “light receiving relationship”, and similar terms, may indicate that an item may during operation of a source of light (like a light generating device or light generating element or light generating system) may receive light from that source of light. Hence, the item may be configured downstream of that source of light. Between the source of light and the item, optics may be configured.

The terms “upstream” and “downstream”, such as in the context of propagation of light, may especially relate to an arrangement of items or features relative to the propagation of the light from a light generating element (here the especially the light source(s)), wherein relative to a first position within a beam of light from the light generating element, a second position in the beam of light closer to the light generating element (than the first position) is “upstream”, and a third position within the beam of light further away from the light generating element (than the first position) is “downstream”. For instance, instead of the term “light generating element” also the term “light generating means” may be applied.

The terms "radiationally coupled" or “optically coupled” may especially mean that (i) a light generating element, such as a light source, and (ii) another item or material, are associated with each other so that at least part of the radiation emitted by the light generating element is received by the item or material. In other words, the item or material is configured in a light-receiving relationship with the light generating element. At least part of the radiation of the light generating element will be received by the item or material. This may in embodiments be directly, such as the item or material in physical contact with the (light emitting surface of the) light generating element. This may in embodiments be via a medium, like air, a gas, or a liquid or solid light guiding material. In embodiments, also one or more optics, like a lens, a reflector, an optical filter, may be configured in the optical path between light generating element and item or material. The term “in a light-receiving relationship” does, as indicated above, not exclude the presence of intermediate optical elements, such as lenses, collimators, reflectors, dichroic mirrors, etc. In embodiments, the term “lightreceiving relationship” and “downstream” may essentially be synonyms. In a further aspect, the invention may provide a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, and an optical wireless communication device, comprising the light generating system according to the invention. In embodiments, the light generating device may especially be configured for illumination of a ceiling.

The light generating system may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems. In embodiments, the light generating system may be part of or may be applied in a ceiling lighting system.

As indicated above, the lighting unit (or device) may be used as backlighting unit in an LCD display device. Hence, the invention also provides an LCD display device comprising the lighting unit as defined herein, configured as backlighting unit. The invention also provides in a further aspect a liquid crystal display device comprising a back lighting unit, wherein the back lighting unit comprises one or more light generating systems as defined herein.

In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, and an optical wireless communication device, comprising the light generating system as defined herein. The light generating device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. For instance, in embodiments the light generating device may comprise a housing or a carrier, configured to house or support one or more of the (modulated linear) lens and the linear light source array.

Instead of the terms “lighting device” or “lighting system”, and similar terms, also the terms “light generating device” or “light generating system”, (and similar terms), may be applied. A lighting device or a lighting system may be configured to generate device light (or “lighting device light”) or system light (“or lighting system light”).

The lighting device may comprise a light source. The device light may in embodiments comprise one or more of light source light and converted light source light (such as luminescent material light).

The lighting system may comprise a light source. The system light may in embodiments comprise one or more of light source light and converted light source light (such as luminescent material light).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. 1 A-C schematically depict an embodiment of the lens;

Fig. 2 schematically depicts simulation results;

Fig. 3 A-C schematically depict further embodiments of the lens;

Fig. 4A-4B schematically depict simulation results;

Fig. 5A-B schematically depict further aspects of the invention;

Fig. 6A-6B schematically depict further aspects of the invention. The schematic drawings are not necessarily to scale. DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 A schematically depicts an embodiment of the lens 200, especially of the modulated linear lens. In the depicted embodiment, the lens 200 has a lens surface 210 shaped according to a lens surface shape 220. The lens surface shape 220 is especially defined in a cylindrical coordinate system by y, 0, and R, wherein y is an axial position along a cylindrical axis A, 9 is an angular position with respect to the cylindrical axis A, and R is a radial distance to the cylindrical axis A. In the depicted embodiment, the lens 200 is, for visualization purposes, depicted in a cartesian coordinate system with coordinates x, y, and z (in mm), especially wherein x = R*cos(9), y=y, and z=R*sin(9). For visualization purposes, the y-axis is compressed (see scales).

In embodiments, the lens surface shape 220 may have a local average radius R, wherein:

In particular, at a given position S, along the cylindrical axis A, the local average radius R may be determined according to:

It will be clear to the person skilled in the art that the local average radius R may not be defined at the ends of the lens along the cylindrical axis A, as ^+Ay/2 may lie outside of the lens. Hence, the lens surface shape 220 may have a minimal axial position and a maximal axial position y _ma x arranged at opposite ends of the lens 200 along the cylindrical axis (A), wherein position S, is arranged between the minimal axial position and the maximal axial position y _ma x, wherein S, is arranged at a distance of at least Ay from the minimal axial position y _m in, and wherein S, is arranged at a distance of at least Ay from the maximal axial position y _max . Hence, the (local) smoothness of the lens and the (global) modulation are herein defined to be satisfied along at least a lens surface section. The lens surface section may comprise at least 70% of the lens surface shape along the cylindrical axis, such as at least 80%, especially at least 90%, such as at least 95%.

In embodiments, Ay may be selected from the range of 1 - 100 mm, such as from the range of 2 - 50 mm.

In further embodiments, 0 E [0, 0 _max ], especially wherein 9 _max is selected from the range of 0.5*7t - 1.5*7t. Specifically, in the depicted embodiment, 0 E [0, zr] .

In embodiments, along a lens surface section, such as along at least 80% of the lens surface along the cylindrical axis A, may apply that for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis A for Ay, especially wherein Ci < 0.3, such as wherein Ci < 0.25. Hence, locally (within a range of Ay), the lens surface 210 may be relatively smooth. In further embodiments, along the lens surface section may apply that:

In further embodiments, along a lens surface section, such as along at least 80% of the lens surface along the cylindrical axis A, may apply that for a first angular position 91, R differs by at least RA * C2 between a first axial position yl and a second axial position y2, especially wherein C2 > 0.03, such as C2 > 0.05, and especially wherein RA is an average value of R (along the cylindrical axis A) for the first angular position 91. Hence, the modulation may be substantial along the lens length L. In yet further embodiments, along the lens surface section may apply that:

3yl,y2, 01: |

The lens surface 210 may especially comprise an inner lens surface 221 or an outer lens surface 222, i.e., the inner lens surface 221 and/or the outer lens surface 222 may be modulated. In embodiments, the lens surface shape 220 may comprise an inner lens surface shape 221, and the lens surface 210 may comprise a concave inner lens surface 211 shaped according to the inner lens surface shape 221. In further embodiments, the lens surface shape 220 may comprise an outer lens surface shape 222, and the lens surface 210 may comprise a convex outer lens 212 surface shaped according to the outer lens surface shape 222.

In specific embodiments, along at least 90% of the lens surface shape 220 along the cylindrical axis (A) applies that: (a) for each value of 9 the local average radius R changes at most by Ci*Ay when moving along the cylindrical axis A for Ay, wherein Ci < 0.3; and (b) for a first angular position 91, R differs by at least RA * C2 between a first axial position yl and a second axial position y2 wherein C2 > 0.03, and wherein RA is an average value of R for the first angular position 91.

Specifically, for the depicted embodiment applies that Ci=0.05 and C2=0.25. As indicated above, there may be a first angular position for which there is a substantial modulation along the lens length L. However, there may also be a plurality of first angular positions for which there is a substantial modulation along the lens length L, such as for all angular positions. Hence, in embodiments, along the lens surface section may apply that: for each angular position 9n, R differs by at least RA * C2 between a first axial position ynl and a second axial position yn2, especially wherein C2 > 0.03, especially wherein RA is an average value of R for the angular position On, and especially wherein 0 _n E [0, 0 _max ], more especially wherein 9 _m ax is selected from the range of 0.5*7t - 1.5*7t.

Specifically, for the lens 200 in the depicted embodiment, applies that: /?(0, y) = r(0) + p(0,y)

Hence, the radial distance R may have a first component r(6) dependent on the angular position 6, which is thus constant along the cylindrical axis A, and a second component r(6,y) dependent on both the angular position 6 and the axial position y, which may thus especially vary along the cylindrical axis A (also depending on the angular position 0). Specifically, Fig. IB schematically depicts the first component of the lens 200 schematically depicted in Fig. 1 A, and Fig. 1C schematically depicts the second component of the lens 200 schematically depicted in fig. 1 A.

Fig. 2 schematically depicts simulated illumination profiles of a ceiling 30 and a wall 40 with a comparative linear light source array and a comparative linear lens. The simulations were performed with commercial ray tracing software. For the simulations, a linear light source array of rectangular sources (representing LEDs) along the y-axis, uniformly spaced from y=-2000mm up to y=+2000mm was represented. The z-axis corresponds to their principal direction of emittance. The ceiling is represented by a plane at z=500mm and, and the wall is represented by a plane at y=3000mm. The goal may be to uniformly illuminate the ceiling from x=-750mm up to x=+750mm. Specifically, Fig. 2 schematically indicates the simulated illumination I (in lumen) of the ceiling 30 with respect to the y-axis and the x-axis (in mm), and of the wall 40 with respect to the z-axis and the x- axis (in mm), along with corresponding distributions of the illumination values. As depicted in Fig. 2, the illuminated area of the linear lens has unwanted "pointy” artefacts at sides corresponding to the ends of the linear lens. These artefacts may be caused by the characteristic that in a linear lens, there may generally be a direction along which the source is exactly in focus. In those directions, sharp and undesirable focus peaks may be formed.

Fig. 3 A-C schematically depict embodiments of the lens 200. Specifically, Fig. 3 A schematically depicts a wide-to-narrow modulated linear lens 200 for which the radial distance is largest at y=0 and decreases towards (y=-2000 and y _ma x (y=2000). In further embodiments, for the depicted lens 200, the width of illumination at the ceiling (in mm) may be approximated by: w(y) = 4000 In this configuration, the light distribution may be more concentrated at the outer ends of the modulated linear lens. This concentration of light may be counteracted by varying the LED pitch (see below).

Fig. 3B schematically depicts a modulated linear lens 200. In further embodiments, for the depicted lens 200, the width of illumination at the ceiling (in mm) may be approximated by: w(y ^J ) = 1000 3000

In the depicted embodiment, the lens surface may have a wave shape 20, especially a sinusoidal shape 21, along the cylindrical axis A. Specifically, in the depicted embodiment, the sinusoidal shape 21 is at least partially defined by cos(y), wherein = -ymax. In particular, in embodiments, p(9,y) (see above) may define a wave shape, especially a sinusoidal shape 21, along the cylindrical axis A.

Fig. 3C schematically depicts a harmonically modulated linear lens 200 comprising a combination of the lenses depicted in Fig. 3 A-B; the lens 200 is both linearly wide-to-narrow and harmonically modulated. In further embodiments, for the depicted lens 200, the width of illumination at the ceiling (in mm) may be approximated by: w( ^J y) = 4000

In the embodiments depicted in Fig. 3A-C, both the inner lens surfaces 210, 211 and the outer lens surfaces 212 are modulated. Specifically, in the depicted embodiment, the inner lens surface shape 221 and the outer lens surface shape 222 are different shapes. In further embodiments, the inner lens surface shape 221 and the outer lens surface shape 222 may have the same shape (but a different size).

Fig. 4A schematically depicts the simulated illumination of the modulated linear lens 200 depicted in Fig. 3B. Specifically, Fig. 4A schematically depicts the simulated illumination I of the ceiling 30 with respect to the y-axis and the x-axis (in mm), and of the wall 40 with respect to the z-axis and the x-axis (in mm), along with corresponding distributions of the illumination values. In particular, the artefacts may be less severe compared to the purely linear lens (see Fig. 2), while the illuminance in the cross sections may have a similar quality, and the far field intensity may be substantially less peaked.

Fig. 4B schematically depicts the simulated illumination of the modulated linear lens 200 depicted in Fig. 3C. Specifically, Fig. 4B schematically depicts the simulated illumination I of the ceiling 30 with respect to the y-axis and the x-axis (in mm), and of the wall 40 with respect to the z-axis and the x-axis (in mm), along with corresponding distributions of the illumination values. Specifically, the ceiling illumination area may be more rectangular, and the number of rays hitting the wall may be limited.

For the simulation of Fig. 4 A a linear light source array 10 with a constant pitch y _p was used. Specifically, the constant pitch y _p was set at about 40.5 mm (corresponding to the constant pitch depicted in Fig. 6A).

For the simulation of Fig. 4B a light source array 10 with a non-uniform source spacing was used. Specifically, the pitch y _p of the light source array was a linearly varying pitch corresponding to the linearly varying pitch depicted in Fig. 6A.

Fig. 5A schematically depicts a further (very schematic) embodiment of the lens 200. In the depicted embodiments, the lens 200 has a lens length L parallel to the cylindrical axis A, and the lens 200 has a largest lens width W 1 and a smallest lens width W2 perpendicular to the lens length L, and especially perpendicular to an optical axis A of the lens 200. In particular, W1 may be parallel to W2. In embodiments, L/Wl > 10. In further embodiments, W1/W2 < 2.

In the depicted embodiment, the lens surface 210 further comprises a plurality of surface structures 215. In further embodiments, neighboring surface structures 215 are separated by a structure distance of at most 0.2*Ay. In further embodiments, the surface structures 215 may be selected from the group comprising a surface roughness, a surface texture, and a micro lens.

Fig. 5A further schematically depicts an embodiment of a light generating system 1000 comprising a linear light source array 10 and the lens 200 according to the invention. In particular, in the depicted embodiment, the linear light source array 10 comprises a plurality of (linearly arranged) light sources 100, and the lens 200 is configured in a light receiving relationship with the plurality of light sources 100.

In the depicted embodiment, the plurality of light sources 100 are arranged at a pitch y _p , especially wherein y _p > Ay, and wherein the pitch y _p is constant along the cylindrical axis (A).

Fig. 5B schematically depicts embodiments of light generating device 1200. The light generating device 1200 may especially be selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, and an optical wireless communication device, comprising the light generating system 1000 according to the invention.

Specifically, Fig. 5B schematically depicts an embodiment of a luminaire 2 comprising the light generating device 1200 as described above. Reference 301 indicates a user interface which may be functionally coupled with a control system 300 comprised by or functionally coupled to the lighting device 1200. Fig. 5B also schematically depicts an embodiment of a lamp 1 comprising the lighting device 1200. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating device 1200. Hence, reference 1200 refers to a light generating device, which may e.g., be selected from the group of a lamp 1, a luminaire 2, a projector device 3. The light generating device 1200 may comprise the beam shaping element 100. Fig. 5B also schematically depicts an embodiment of the light generating device 1200 comprising a wall light device (such as especially wall washers). The light generating device 1200 may also comprise a cove lighting device (for illuminating a cove).

In embodiments of the light generating system 1000, besides the modulation of the lens 200, also the pitch between the light sources 100 may be modulated to affect the illumination profile. Fig. 6A schematically depicts the pitch (in mm) between light sources 100 as a function of the axial position y of the light sources 100 along the cylindrical axis A for different embodiments of the light generating system 1000. Specifically, in Fig. 6A line LI indicates a constant pitch, line L2 indicates a linearly varying pitch, and line L3 indicates a polynomially varying pitch.

Hence, in embodiments, the pitch y _p between light sources 100 may be selected from the group comprising a constant pitch, a linearly varying pitch, and a polynomially varying pitch.

Fig. 6B schematically depicts the simulated illumination of the modulated linear lens 200 depicted in Fig. 3 A together with the polynomially varying pitch depicted in Fig. 6A. Specifically, Fig. 6B schematically depicts the simulated illumination I of the ceiling 30 with respect to the y-axis and the x-axis (in mm), and of the wall 40 with respect to the z- axis and the x-axis (in mm), along with corresponding distributions of the illumination values. In particular, the illuminated ceiling area may have an oval shape with relatively little artefact effect (also see Fig. 2). Also, relatively few rays still hit the wall and the far field intensity may be well-behaved, with (essentially) no peaks in any direction.

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.