WO2014148729A1 - Système d'éclairage de surface basé sur un guide d'ondes incurvé - Google Patents

Système d'éclairage de surface basé sur un guide d'ondes incurvé Download PDF

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Publication number
WO2014148729A1
WO2014148729A1 PCT/KR2013/012375 KR2013012375W WO2014148729A1 WO 2014148729 A1 WO2014148729 A1 WO 2014148729A1 KR 2013012375 W KR2013012375 W KR 2013012375W WO 2014148729 A1 WO2014148729 A1 WO 2014148729A1
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Prior art keywords
waveguide
optical
illumination
target surface
light
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PCT/KR2013/012375
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English (en)
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Sam Hyeon Lee
Oliver B. Wright
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Plum Science
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Publication of WO2014148729A1 publication Critical patent/WO2014148729A1/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S6/00—Lighting devices intended to be free-standing
    • F21S6/002—Table lamps, e.g. for ambient lighting
    • F21S6/003—Table lamps, e.g. for ambient lighting for task lighting, e.g. for reading or desk work, e.g. angle poise lamps
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2103/00—Elongate light sources, e.g. fluorescent tubes
    • F21Y2103/10—Elongate light sources, e.g. fluorescent tubes comprising a linear array of point-like light-generating elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]

Definitions

  • This invention concerns a system of illumination based on a partly-curved or curved multimode optical waveguide made of smooth-walled transparent material or materials and having a high-aspect-ratio cross section.
  • the field of application includes desk lighting, panel illumination, decorative lighting and vehicle lighting.
  • Optical waveguides have been used extensively used in optical illumination.
  • One example is in the case of a bundle of optical fibers with cleaved output ends or with an attached lens.
  • optical fibers with modified output ends are presented in the US patents Nos. 7,620,290 B2 (I. M. Rizoiu et al.) and 5,772,657 (M. Hmelar et al.). These patents reveal means to change the distribution of light exiting an optical fiber by tailoring the shape of the output end in various ways, such as by the use of symmetric or asymmetric faceted or lens-like output faces.
  • the use of a single optical fiber or single bundle of optical fibers is not well suited to producing a uniform illumination over an approximately rectangular target surface.
  • US patent No. 7,278,774 (C.-Y. Chang) reveals the use of an optical waveguide with two major surfaces in opposition, such as a rectangular or wedge cross-section waveguide, used with light-extracting elements on one of the major surfaces.
  • This type of waveguide can be used to couple light out onto a target surface. While this configuration allows a larger degree of freedom of choice of the light distribution exiting the waveguide compared to the use of a single optical fiber or single bundle of fibers, the optical losses from one of the major surfaces in this method is not suited to the operation of an illumination system based on light exiting the waveguide output end meant only for a single specified target surface.
  • a problem with many illumination systems is that the requirement for a relatively uniform distribution of illumination over a region of a target surface conflicts with the requirement for the system of illumination not to be placed too close to the user or target surface. For example, standard desk lights must be placed above and close to the target surface if a relatively uniform illumination is desired, thus producing eye strain and dazzling the user.
  • Illumination systems based on multimode optical waveguides to guide light from an optical source or optical sources placed at the input end of such a waveguide are in common use.
  • To redirect light to the required region of a target surface it is advantageous to make use of a waveguide that is curved or partly curved.
  • a waveguide that is curved or partly curved.
  • the present invention aims to alleviate these problems by illuminating the input end of a partly-curved or curved optical waveguide, of high-aspect-ratio cross section perpendicular to the main axis of optical propagation and made of smooth-walled transparent material, that possesses a tailored output end to compensate for the waveguide-curvature-related redistribution of light inside the waveguide. It may also be possible to also choose a distribution of illumination at the input end of the waveguide to compensate for the effect of the angular divergence of the light after exiting the waveguide. By directing the light exiting the output end onto a target surface one can by this means produce a distribution of light with enhanced uniformity thereon within an approximately rectangular target surface.
  • the present invention can be constructed so that the system of illumination does not interfere with the viewing of the target surface.
  • This invention features the combination of the use of a uniform or non-uniform distribution of illumination of the input end of a partly-curved or curved optical waveguide, made of smooth-walled transparent material, of high-aspect-ratio cross section perpendicular to the main axis of optical propagation, and a tailored output end.
  • the exiting light is directed onto an approximately rectangular target surface to produce a distribution of light with enhanced uniformity thereon.
  • An important aspect of the present invention is that it provides illumination that is useful for a wide range of situations, and the spatial distribution of the illumination can be tailored to exhibit enhanced uniformity without dazzling the user and without hindering the viewing of the target region.
  • Another important aspect of the present invention is that it provides illumination that is energy saving, the required illumination reaching the required target surface with the minimum of optical losses.
  • One of the possible applications of the present invention is for a desk light.
  • a seated reader can carry out work with a more uniform distribution of illumination that is normally available from a standard desk light and thereby avoid eye strain.
  • the present invention can also be useful as a means to illuminate a computer keyboard and at the same time not dazzle the user.
  • the present invention can also be useful as a panel light that can illuminate a painting, notice board or poster.
  • the present invention can also be used as a functional or decorative table-, wall- or ceiling light.
  • the present invention can also be used for illumination inside or outside a vehicle.
  • Fig. 1 Oblique view of the first embodiment of the present invention based on a rectangular-cross-section waveguide composed of straight and curved parts, and with a lateral positioning of optical sources 10 arranged to be non-uniform.
  • the housing is not shown.
  • Fig. 2 Side view of the first embodiment of the present invention.
  • Fig. 3 Side view of the first embodiment of the present invention showing the shape of the curved section of the waveguide. The origin of the extremal rays is drawn for convenience at the midpoints of the end faces 33 and 35.
  • Fig. 4 Graph of the measured normalized density of light-emitting diodes per unit length as a function of the absolute value
  • of the distance y at x 31 cm in the experiment realizing the first embodiment of the present invention.
  • Fig. 5 Graph of the measured distribution of illumination as a function of distance x in the experiment realizing the first embodiment of the present invention.
  • Fig. 6 Graph of the measured distribution of illumination as a function of the absolute value
  • of the distance y at distances x 7.5, 31 and 56 cm in the experiment realizing the first embodiment of the present invention.
  • Fig. 7 Graph of the measured distribution of illumination as a function of distance x in the experiment realizing the first embodiment of the present invention for the top and bottom surfaces of the output end of the waveguide measured separately, as well as for their sum.
  • Fig. 8 Graph of the measured distribution of illumination as a function of distance x as a function of the absolute value
  • of the distance y at x 31 cm in an experiment in which the light-emitting diodes are uniformly spaced.
  • Fig. 9 Flow diagram for the prescription for finding the waveguide output-end shape used in embodiment 1 using numerical simulations.
  • Fig. 11 Graph of the calculated normalized cumulative optical intensity contributed by each ray at the target surface 1 as a function of the position of the ray when it crosses the output end 30.
  • the arrows show the points on the respective curves chosen for calculation of the quantity ⁇ x .
  • Fig. 13 Graph of the change in the angle of refraction ⁇ in air as a function of b , in which the solid curve corresponds to the rays from CD and the dotted curve to the rays from AD.
  • Fig. 14 Graph of the value of ⁇ x as a function of b calculated by trigonometry.
  • the dashed curve shows the total optical intensity distribution at the target surface 1.
  • the horizontal axis represents the distance x .
  • Fig. 16 Flow chart showing the prescription used to obtain the required distribution in the density of optical sources per unit length along the longer axis of the input end of the waveguide, or other parameters governing the distribution of illumination of the input end of the waveguide.
  • Fig. 17 Side view of the second embodiment of the present invention, for application to the illumination of a painting, poster, notice board, wall, or vertical or sloping surface. The details of the optical sources and waveguide inside the housing are not shown.
  • Fig. 18 Side views of embodiments of the present invention showing different cross sections perpendicular to the main axis of optical propagation of the waveguide: (a) curved waveguide, (b) S-shaped waveguide, (c) hook-shaped waveguide, (d) wiggly-shaped waveguide.
  • Fig. 19 Side views of embodiments of the present invention showing different cross sections perpendicular to the main axis of optical propagation of the waveguide of the output end of the waveguide: (a) two cylindrically-curved end faces with different radii of curvature, (b) three cylindrically-curved end faces with different radii of curvature, (c) four cylindrically-curved end faces with different radii of curvature, (d) cross section defined by a smooth curve that departs from a cylindrical surface, (e) two different transparent materials of different refractive index, which may have curved or flat faces, are bonded to the waveguide to form the output end.
  • Fig. 20 Cross-sectional view of embodiments of the present invention showing different types of optical sources.
  • This view shows a cross section containing the longer axis of waveguide 5 and the main axis of optical propagation in the waveguide 5.
  • (c) Means to produce a distribution of illumination of the input end of the waveguide that is non-uniform with respect to the longer axis of the input end of the waveguide, produced by the use of serrated edge in the form of a blazed grating, in which the blaze angle varies as a function of distance along this longer axis.
  • This view also shows a cross section containing the longer axis of waveguide 5 and the main axis of optical propagation in the waveguide 5.
  • Fig. 21 Oblique view of an embodiment of the present invention based on a rectangular-cross-section waveguide composed of straight and curved parts, and with a lateral positioning of optical sources 10 arranged to be uniform.
  • the housing is not shown.
  • the first embodiment of the present invention is shown in an oblique view in Figure 1.
  • This embodiment 1 can be used, for example, as a desk light to illuminate a horizontal and flat surface, an approximately rectangular portion of this surface corresponding to the target surface 1.
  • the target surface 1 may in special cases be an approximately square portion.
  • the smooth, flat and horizontally-oriented input end 2 of a uniform transparent multimode optical waveguide 5 of rectangular-cross section perpendicular to the main axis of optical propagation and with smooth walls 6-9 and high-aspect-ratio is fixed above an array of optical sources 10 spaced in a non-uniform fashion along the longer axis PQ bisecting the input end 2 of the waveguide 5.
  • the waveguide 5 is made up of two parts that together comprise a single piece of transparent homogeneous material, a cuboid part 15 of uniform thickness d , width W and length L , arranged vertically, and a circularly-curved annular part 16 of a cylinder of inner radius R , thickness d and width W .
  • the aspect ratio W / d is typically chosen to be large, usually greater than 5.
  • the width W is chosen to be somewhat less than or equal to the width of the required approximately rectangular target surface 1.
  • the radius R and that, R + d , of the curved portion of wall 6 are chosen so that the majority of rays emitted from the array of optical sources 10 are injected into the waveguide 5 and are internally reflected inside it.
  • n the refractive index of the transparent waveguide 5.
  • Figure 2 shows a side view of the embodiment 1 in section in a vertical plane passing through point S and parallel to walls 7 and 8.
  • This vertical plane represents an axis of mirror symmetry of the illumination system.
  • the light-source electrical wiring not necessarily preserving this mirror symmetry, is not shown.
  • a opaque housing 20, not shown in Figure 1 shields light from the optical sources 10 apart from the light that enters waveguide 5.
  • This housing 20 also holds the waveguide 5 so that the plane of the input end 2 of the waveguide 5 is parallel to the target surface 1 and held at a height h above it.
  • Figure 3 shows a close-up view of the annular part 16 of the waveguide 5 of Figure 2, including the output end 30 whose axis in the width direction is parallel to that, PQ, of the input end 2.
  • the annular part 16 meets the cuboid part 15 in the plane marked by the dotted lines 25 in Figure 1, which is also parallel to PQ.
  • Annular part 16 possesses a specially-shaped output end 30 composed of two convex cylindrically curved surfaces termed end faces, an upper one 33 and a lower one 35, shown in section in Figure 3 by the arcs of the circles of radius r joining points C to D and D to A, respectively.
  • the distance along the arc AD can in embodiment 1 be chosen to be greater than, equal to or less than that along the arc BC. Therefore, the angle ⁇ 1 subtended by points F and A about the center of curvature passing through point K can be smaller, equal to or greater than the angle ⁇ 2 subtended by points F and C about K.
  • Angles ⁇ 1 and ⁇ 2 in this embodiment 1 are typically but not exclusively chosen between 90°and 180°
  • the point B in Figure 3 represents the point where a straight line from D meets the straight line AC at right angles.
  • the ratio BC/AC, referred to as f the ratio BC/AC, referred to as f
  • the distance BD, referred to as b angles ⁇ 1 and ⁇ 2
  • the radius r fully characterize the output end 30 in embodiment 1.
  • Being able to choose radius r is advantageous in that this provides an extra degree of freedom in choosing the distribution of illumination in the x direction on the target surface, where the x direction is defined in Figure 1 as the longitudinal direction perpendicular to the flat portion of wall 9.
  • the choice of the two surfaces for end faces 33 and 35 as curved surfaces can help to render the distribution of illumination in the x direction on the target surface more homogeneous.
  • the effect of the output end 30 on the distribution of the light exiting through it can be seen by the schematically-drawn extremal rays shown in the side view of Figure 3.
  • the extremal rays refer to those rays that represent the boundary of the illuminated region from each end face 33 and 35 of output end 30.
  • the origin of the extremal rays in the considered plane is drawn for convenience at the midpoints of the end faces 33 and 35.
  • Extremal rays 40 and 45 emanate from points between B and C on surface 30, respectively, whereas extremal rays 50 and 55 emanate from points between A and B on end face 35, respectively.
  • Choice of a positive distance BD results in the light exiting end face 33 being directed to a region closer to the base of the illumination system compared to that exiting end face 35. In this way the distribution of illumination on the target surface in the x direction can be rendered more uniform than for the case of a planar output edge 30.
  • a result of this choice of output end 30 and angles ⁇ 1 and ⁇ 2 is that it is possible to arrange for the extremal ray 55 to be sufficiently downward pointing so as not to dazzle the user, in particular if they are situated with the lamp output end 30 pointing towards them.
  • This usage of embodiment 1 is useful for example, to illuminate the keyboard of a computer from behind the computer screen or for miscellaneous desk work.
  • embodiment 1 is also useful, for example, for miscellaneous deskwork that may or may not involve the use of a computer.
  • the spacing of the sources 10 is chosen to vary with position along PQ so that the optical intensity entering the waveguide 5 through input end 2 decreases on average monotonically from positions corresponding to P and Q towards the midpoint S of the input end 2 of the waveguide 5 along this axis PQ.
  • the distribution of illumination on the target surface in the y direction defined in Figure 1 as the lateral direction perpendicular to the side walls 7 and 8, can be rendered more uniform than for the case of a uniform spacing of sources 10.
  • eleven vertically-oriented light-emitting diodes representing the optical sources 10 produce visible white illumination with maximum angle of deviation 8° from the vertical direction in air, corresponding, according to Snell's law, to a maximum angular deviation of approximately 5° from the vertical inside the straight portion 15 of the waveguide 5, and are placed in contact with the input end 2 of waveguide 5 along the line PQ.
  • the lateral positioning of the light-emitting diodes representing the optical sources 10 is arranged to be non-uniform but symmetrical about point S along line PQ, according to the graph of the normalized density of light-emitting diodes 10 per unit length plotted against the absolute value
  • the distribution of illumination on the target surface 1 was measured with a thin, upward-facing photodetector fitted with a diffusing surface on top, resulting in a detection sensitivity varying approximately as the cosine of the angle of incidence for an incident light beam.
  • the results of such measurements along the x axis, with the ( x , y ) coordinate origin taken at a point directly below point S, are shown in Figure 5.
  • a significant region along the x axis away from the system of illumination remains strongly illuminated.
  • the result of the non-uniform distribution of optical sources 10 is a largely uniform distribution of illumination of optical intensity on the target surface 1 in the y direction, even for values of
  • greater than the half width W /2 12.5 cm of the waveguide 5.
  • the distribution of Figure 4 can in fact be approximated by the formula c 1 - c 2 exp(- z 2 / a 2 ), where c 1 , c 2 and a are positive constants and z is the distance along the longer axis of the input end 2 of the waveguide 5, with point S taken as the origin.
  • FIG. 7 shows, together with the total normalized optical intensity reproduced from Figure 5, the separate distributions of illumination normalized so as to represent accurately their relative contribution.
  • the distribution from the top end face 33 shows a maximum for a smaller value of x than that from the bottom end face 35.
  • Each of these separate distributions alone show a reduced uniformity as a function of x .
  • the sum of the two produces a distribution of illumination of enhanced uniformity.
  • This principle of the use of two distributions to enhance uniformity is analogous to the principle behind the operation of Helmholtz coils in electromagnetism, in which a magnetic field of enhanced uniformity is created by the use of two parallel and axially-separated circular coils.
  • the shape of the separate distributions corresponding to the top and bottom end faces 33 and 35 are similar to those one would obtain from the use of a plane output end 30, and each produces a distribution of illumination of smaller uniformity than their sum.
  • the peaks in the separate distributions corresponding to the two end faces can be displaced by a certain optimally chosen amount along the x axis, allowing a distribution of illumination of optical intensity of enhanced uniformity in the x direction to be obtained.
  • the measurements of Figure 8 provide a prescription for finding the necessary non-uniform spacing of the optical sources 10 required, as in the example of Figure 4.
  • an appropriate distribution in the density of optical sources 10 per unit length that produces a distribution of illumination over the target surface 1 that is closer to a uniform distribution, is proportional to the reciprocal of the optical intensity distribution in Figure 8.
  • the distribution in density of optical sources 10 per unit length chosen in Figure 4 approximately satisfies this criterion. This rule of thumb is discussed further below.
  • the first step is to choose a convenient initial waveguide 5 shape with a flat output end 30, so that the output end 30 provides illumination in the general direction of the required approximately rectangular target surface 1.
  • the optical sources 10 their optical polarization and their angular distribution of emission of optical intensity.
  • Ray tracing is executed using the Fresnel equations of optical transmission, reflection and refraction.
  • a Gaussian distribution of light emission in air of an angular width at full-width-half-maximum equal to 10° distributed evenly and symmetrically over the input end 2 of the waveguide 5 was used, and this corresponded to the use of 10000 light rays of random polarization.
  • Figure 10 shows the calculated normalized optical intensity distribution at the target surface 1 as a function of distance x .
  • This optical intensity is calculated according to the number of rays hitting unit length of the target surface 1 multiplied by the cosine of the angle of incidence of the ray in question at the target surface 1.
  • This cosine factor accounts for the increase in area of illumination by a light beam incident obliquely on a surface.
  • Cosine factors are also used for calculation of transmission of optical intensity at the waveguide/air input and output ends 2 and 30, as is known to those skilled in the art of ray tracing with the Fresnel equations.
  • the coordinates of the points where each ray exits the output end 30 are recorded, as well as their longitudinal position, represented by distance x , on the target surface 1.
  • Figure 11 shows a graph of the calculated normalized cumulative optical intensity contributed by each ray at the target surface 1 as a function of the position of the ray when it crosses the output end 30.
  • the origin of the graph corresponds to point C, and the right-hand side of the graph to point A, both points being shown in Figure 3.
  • the normalized cumulative optical intensity is proportional to the integral of the optical intensity contributed from all rays that cross the output end 30, with the integration taken from point C up to a given position across the output end 30.
  • the position at which the normalized cumulative optical intensity reaches the value 0.5 is recorded, and this is used to calculate the required position of point B in Figure 3.
  • This distance b determines the angle between the end faces 33 and 35 that arise for non-zero b .
  • the principle is similar to the Helmholtz-coil approach in electromagnetism: namely, the use of the superposition of two distributions displaced with respect to one another. Choice of a non-zero value of b will allow this to be achieved by the different orientations of the end faces 33 and 35.
  • the sum of these two intensity distributions is represented by the graph of Figure 10.
  • the object of this stage of the prescription is to displace these two distributions so that the sum of the two distributions produce a distribution of illumination of enhanced uniformity on the target surface 1.
  • Choosing a positive value for b is advantageous because it avoids loss of light through the side walls 6-9 of the waveguide 5.
  • ⁇ x should be equal to the distance between the peak in the solid curve, this curve representing the rays exiting between C and B, and the position of the onset on the low x side of the dotted curve, this curve representing the rays exiting between A and B.
  • ⁇ x 11.7 cm.
  • ⁇ x should be equal to the distance between the peak in the solid curve and the position of the onset on the low x side of the dotted curve.
  • FIG. 14 A graph of the corresponding calculated value of ⁇ x as a function of b is shown in Figure 14, taking points close to D as reference points for the calculation of the angles.
  • ⁇ x is taken as a variable representing the difference in the calculated displacements on the x axis of the intensity distributions associated with CD and AD, that is, associated with the upper end face 33 and lower end face 35, respectively.
  • This graph is shown by the dashed curve, together with the separate contributions from the intensity distributions associated with CD and AD, that is, associated with the upper end face 33 and lower end face 35, respectively, as shown by the respective solid and dotted curves.
  • the expected separation of the two intensity distributions arising from faces 33 and 35 is obtained. It is clear by comparison with Figure 10 that the obtained distribution of illumination of optical intensity shown by the dashed curve in Figure 15 is of enhanced uniformity. Not only is the symmetry of the optical intensity distribution improved, but its full width at half maximum in the x direction is increased by a factor of approximately 1.4.
  • simulations can also be used to optimize the required distribution in the density of optical sources 10 per unit length, or other parameters governing the distribution of illumination to the input end 2.
  • simulations in three dimensions should be conducted.
  • a rule of thumb that can be advantageously adopted is to first conduct a simulation, in this case in three dimensions, based on a uniform distribution of optical sources 10 each providing identical illumination, and calculate the resulting distribution of illumination in the y direction.
  • a more appropriate distribution in the density of optical sources 10 per unit length, that produces a distribution of illumination over the target surface 1 that is closer to a uniform distribution, can be obtained by the use of a density of optical sources 10 per unit length that is proportional to the reciprocal of the optical intensity distribution in the y direction, at an appropriate value of distance or distances x , calculated from a simulation based on a uniform distribution of optical sources 10 each providing identical illumination.
  • the second embodiment of the present invention is shown in side view in Figure 17.
  • An approximately rectangular target surface 1 can be illuminated with enhanced uniformity in this way by bodily fixing the illumination system to a surface in the vicinity of the desired target surface.
  • a region of the ceiling or of sloping surfaces can be illuminated.
  • Figure 18a corresponds to a waveguide 5 with only a curved section.
  • Figure 18b corresponds to an example in which the input end 2 of the waveguide 5 lies in a vertical plane.
  • Optical sources 10 inject light horizontally into an S-shaped waveguide in this example.
  • Figure 18c shows a waveguide 5 in the form of a hook, whereas Figure 18d shows a waveguide with several wiggles.
  • the required output end 30 should be correspondingly chosen to produce a distribution of illumination of enhanced uniformity.
  • waveguide-curvature-related redistribution of light inside the waveguide can also include the effect of redistribution of light inside the straight section.
  • curved section also applies to a waveguide that contains a section which mimics a smooth curve by a combination of short straight segments connected at relatively small angles with respect to one another.
  • the above-mentioned prescription for optimizing the output end 30 can also be applied to these examples of different forms of waveguide 5.
  • the required values of the parameters characterizing the output end 30 will be different in general for each case.
  • output ends 30 are shown in Figure 19.
  • the output end 30 shown in Figure 19a is similar to that in embodiment 1, except that the two cylindrically-curved end faces 33 and 35 are chosen to have different radii of curvature, including the possibility of the choice of infinite or negative radii of curvature for either or both end faces 33 and 35, where a negative value corresponds to a concave surface.
  • Figure 19b shows an example of the use of three such cylindrically-curved end faces, 33, 35 and 36, all of different radii of curvature
  • Figure 19c shows an example of the use of four such cylindrically-curved end faces, 33, 35, 36 and 37, all of different radii of curvature.
  • Figure 19d shows an example in which the end of the waveguide 5 is shaped according to a smooth curve that departs from a cylindrical surface, which can also play a role in effectively separating the output end 30 of the waveguide 5 into two or more regions that redirect the light into two or more distributions of optical intensity. This may also be thought of as the limit of the above arguments from electromagnetism when applied to an arbitrary number of facets.
  • Figure 19e shows an example with a similar purpose in which two different transparent materials 38 and 39 of different refractive index, which may have curved or flat faces, are bonded to waveguide 5 to form the output end 30 of the waveguide 5.
  • Figure 20 shows examples of different types of optical sources 10.
  • Figure 20a shows, by a cross section containing the longer axis PQ bisecting the input end 2 of the waveguide 5 and the main axis of optical propagation in waveguide 5, a means to double the injection of light into the waveguide 5 by the use of mirrors 41 and 42 and two arrays of light-emitting diodes 10.
  • Figure 20b shows a means to produce a distribution of illumination of the input end 2 that is non-uniform with respect to the longer axis of the input end 2 of the waveguide 5 produced by the use of a varying tilt angle ⁇ of light-emitting diodes 10 as a function of the distance along this longer axis.
  • the tilt may be in a plane passing through the main optical propagation axis of the straight portion of the waveguide 5 and through the longer axis of input end 2, as shown in Figure 20b, or in another plane. Use of tilt can also be beneficial in optimizing the distribution of illumination of enhanced uniformity in the x direction.
  • Another way to produce a distribution of illumination of input end 2 that is non-uniform with respect to the longer axis of the input end 2 of the waveguide 5 is to use an array of identical optical sources 10 that are supplied with different electrical inputs so as to produce the required distribution of illumination of enhanced uniformity on the target surface 1.
  • An array of non-identical optical sources 10 can also be used for this purpose.
  • Other means to achieve a distribution of illumination of input end 2 that is non-uniform with respect to the longer axis of the input end 2 of the waveguide 5 are not excluded.
  • One example is to use a varying optical polarization of the optical sources 10 as a function of the longer axis of the input end 2 of the waveguide 5, because the transmission of light at an oblique incident angle into a transparent material depends on polarization.
  • Another example is to choose the input end 2 to be a shaped or patterned surface in order to produce a varying optical angle of incidence or a varying optical refraction as a function of the longer axis of the input end 2 of the waveguide 5.
  • Examples of such shaping or patterning of input end 2 are the use of a serrated surface, with the serrations varying in angle along the longer axis of the output end 30 of the waveguide 5, or the use of a microlens array, with the focal length or orientation angle of the lenses varying with distance along the longer axis of the output end 30 of the waveguide 5.
  • Figure 20c shows an example of such an embodiment that possesses a serrated surface in the form of a blazed grating, in which the blaze angle varies with distance along the longer axis of the input end 2 of the waveguide 5. This example of Figure 20c produces a similar effect to the case of Figure 20b.
  • An example of a single optical source 10 that can have a uniform intensity along the longer axis of the input end 2 of the waveguide 5 is a fluorescent strip light, shown in use in Figure 20c.
  • a fluorescent strip light shown in use in Figure 20c.
  • embodiments in which the longer axis of the output end 30 of the waveguide 5 are curved, serrated or patterned are also not excluded from this invention.
  • One possible variation is the use of light-emitting diodes 10 of different colors to produce different effects, either all switched on together or used separately, in order to produce the required distribution of illumination of enhanced uniformity on the target surface 1. It is also possible to embed the optical sources 10 inside the waveguide 5 material and silver the end face 2 to minimize coupling losses. Optical sources 10 are not confined to the use of light-emitting diodes or fluorescent strip lights, but can include other types of source of incoherent, coherent or partially coherent light. Embodiments in which the input end 2 of the waveguide 5 are curved in the through-thickness direction of the waveguide 5 are also not excluded from this invention. A cylindrically convex input end 2 could be useful, for example, in collimating the light from the optical sources 10 into the waveguide 5.
  • the high-aspect ratio cross-section of waveguide 5 perpendicular to the main axis of optical propagation does not necessarily have to be of rectangular shape.
  • Other non-exclusive possibilities are a rhombus, an ellipse, a bow-tie, a polygon, an annulus, a rectangular shape with rounded corners or a stadium shape.
  • waveguides with a cross-section that varies along the main axis of optical propagation of the waveguide, such as in the case of a tapered waveguide 5, are not excluded by this invention. This may be advantageous for decorative or weight-reduction purposes.
  • a possible non-uniform distribution of illumination appropriate for such a non-uniform cross-section waveguide is described by the optical intensity along the longer axis of the input end 2 of the waveguide 5 varying as c 1 - c 2 exp(- z 2 / a 2 ), where c 1 , c 2 and a are constants and z in this case is the distance along the possibly-curved longer axis of the input end 2 of the waveguide 5 as measured from the midpoint of this straight or curved axis.
  • a uniform distribution of illumination at the input end 2 may provide a means to achieve a distribution of illumination of optical intensity of enhanced uniformity over an approximately rectangular target surface 1.
  • a waveguide 5 whose cross section is a bow-tie shape is one such example.
  • the outside of the waveguide 5 it is also possible to silver the outside of the waveguide 5 or coat it with an anti-scratch or other protective coating. It is in addition possible to use a waveguide 5 consisting of core and cladding layers of different refractive indices. An opaque coating may if required be applied in this case to the outside surface of the waveguide 5 consisting of a transparent core and a sufficiently thick transparent cladding without affecting performance. Typical materials for the waveguide 5 are transparent plastic or glass.
  • the waveguide 5 can be formed out of a single homogeneous block of material. It is also possible to form the waveguide 5 by bonding elements of it together, possibly elements made of different transparent materials.
  • graded index materials may also be used in the present invention, for example for the purposes of minimizing optical losses.
  • optical-waveguide bending losses of the waveguide 5 or optical losses from defects or scratches on the waveguide 5 arising, for example, from wear and tear of the system do not invalidate the essential features of the invention.
  • the system of illumination described is primarily designed for flat target surfaces, the illumination of spherically or cylindrically concave or convex target surfaces or other curved surfaces can also be envisaged, and are not excluded from the invention.
  • An example of such an application is for the illumination of a poster mounted on a pillar.
  • This invention can be applied to a wide range situations such as desk lighting, panel illumination, decorative lighting and vehicle lighting.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Light Guides In General And Applications Therefor (AREA)

Abstract

La présente invention concerne un système d'éclairage basé sur un guide d'ondes optique multimode partiellement incurvé ou incurvé constitué de matériau ou de matériaux transparent(s) à parois lisses et ayant une section transversale à facteur de forme élevé. Une distribution d'éclairage à l'extrémité d'entrée du guide d'ondes résulte en l'injection de la lumière dans le guide d'ondes. La lumière est guidée à travers les parois latérales du guide d'ondes à l'intérieur du guide d'ondes par réflexion interne. L'extrémité de sortie du guide d'ondes, elle aussi à section transversale à facteur de forme élevé, est adaptée pour compenser la redistribution de la lumière associée à la courbure du guide d'ondes à l'intérieur du guide d'ondes et pour diriger la lumière sortante sur une surface cible. Il peut être possible de choisir aussi une distribution d'éclairage à l'extrémité d'entrée du guide d'ondes pour compenser l'effet de la divergence angulaire de la lumière après qu'elle a quitté le guide d'ondes.
PCT/KR2013/012375 2013-03-19 2013-12-30 Système d'éclairage de surface basé sur un guide d'ondes incurvé WO2014148729A1 (fr)

Applications Claiming Priority (2)

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KR20130029427 2013-03-19
KR10-2013-0029427 2013-03-19

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3215790B1 (fr) * 2014-11-07 2020-01-08 Quarkstar LLC Luminaire à source de lumière empilée
EP3818300A4 (fr) * 2019-03-06 2022-04-13 KT&G Corporation Dispositif de fixation comprenant un guide de lumière et dispositif de génération d'aérosol comprenant ce dispositif de fixation

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000030517A (ja) * 1998-07-10 2000-01-28 Sony Corp 導光体及び点灯表示装置
KR20020024656A (ko) * 2000-09-26 2002-04-01 이중구 씨씨디 카메라용 조명 장치
JP2008116609A (ja) * 2006-11-02 2008-05-22 Matsushita Electric Ind Co Ltd 照明装置用導光体

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000030517A (ja) * 1998-07-10 2000-01-28 Sony Corp 導光体及び点灯表示装置
KR20020024656A (ko) * 2000-09-26 2002-04-01 이중구 씨씨디 카메라용 조명 장치
JP2008116609A (ja) * 2006-11-02 2008-05-22 Matsushita Electric Ind Co Ltd 照明装置用導光体

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3215790B1 (fr) * 2014-11-07 2020-01-08 Quarkstar LLC Luminaire à source de lumière empilée
EP3818300A4 (fr) * 2019-03-06 2022-04-13 KT&G Corporation Dispositif de fixation comprenant un guide de lumière et dispositif de génération d'aérosol comprenant ce dispositif de fixation
US11493184B2 (en) 2019-03-06 2022-11-08 Kt&G Corporation Fixture including light guide and aerosol generating device including the fixture

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