Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
  • G02B27/0938—Using specific optical elements
  • G02B27/0994—Fibers, light pipes
• • 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
  • G02B6/0068—Arrangements of plural sources, e.g. multi-colour light sources
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S10/00—Lighting devices or systems producing a varying lighting effect
  • F21S10/02—Lighting devices or systems producing a varying lighting effect changing colors

Definitions

• the present invention relates to a new device for producing isotropic ambient light, comprising at least one extended light source consisting of several point light sources.
• a solid body having a light entry face and a light exit face is used, and between the two input and output faces of the light. , an internal cavity filled with air and perpendicular to the alignment of the input and output faces.
• This body allows a mixture of light waves by subjecting them to multiple internal reflections on the outer face of the internal cavity.
• the mixing of the light waves is improved by treating in particular the exit face to make it rough.
• the mixing of the light waves is improved by inserting elements of reflective discontinuities (bubbles, metal particles) into the solid body, so as to increase the number of internal reflections.
• a major disadvantage of this type of device lies in its very low light output resulting from the multiplicity of internal reflections of the light waves to obtain their mixture.
• the light wave mixture is obtained by diffusion by means of a translucent plate (for example frosted diffusing plate).
• a translucent plate for example frosted diffusing plate.
• the present invention aims to propose a new device for producing ambient light, which makes it possible to combine two advantages: a very good luminous efficiency, and a very good isotropy in the space of the light produced, that is to say a very good uniformity in every point of the space at the same time of the luminous intensity and the color of the light.
• Another object of the invention is to provide an isotropic ambient light generating device that is compact and can be manufactured at low cost.
• the invention thus relates to an isotropic ambient light production device comprising:
• At least one extended light source which comprises several point light sources spaced along two orthogonal axes (X, Y),
• a waveguide permitting propagation, by total reflections and in a propagation direction (Z) perpendicular to the (X 1 Y) plane, of the light beams produced by the point light sources, and a light scattering means; at the output of the waveguide.
• the dimension (L) of the waveguide along said propagation direction (Z) is furthermore sufficient for the curve (l iiX ) of the luminous intensity which is detected, for each light source (Sj), at the output of the waveguide along one of the two axes (X or Y ) and in a detection range corresponding to the output section of the waveguide along this axis (X or Y), has a maximum value (Imax) and a minimum value (Imin) that satisfy the following quasi- uniformity criterion (Imax-lmoy) ⁇ 0.3.lmoy and (Imoy-lmin) ⁇ 0.3.lmoy, Imoy being the average value of the light intensities (IJ X ) detected along this axis (X or Y).
• the invention thus rests on the new combination:
• a "waveguide" in the sense of the present text is defined in the usual manner in optics as any optical system in which a light wave propagates by total reflections on the edges of the guide, in a given direction of propagation.
• a waveguide can usually be constituted by a tube whose cross section is circular or polygonal (for example rectangular or square section) and preferably, but not necessarily, a central axis of symmetry.
• This guide can be full (eg full parallelepiped); in this case, the propagation of light in the guide by successive total reflections on the edges of the guide is linked to a jump of index between the constituent material of the guide (light propagation medium) and the external environment surrounding the guide (For example air or sheath in a different material having a suitable refractive index lower than that of the propagation medium).
• This guide may be hollow and composed of walls whose inner faces constitute mirrors.
• the device of the invention comprises the additional and optional features hereafter, taken alone or, if appropriate, in combination:
• the curve (lj, x ) of the luminous intensity that is detected, for each light source (Si), has a maximum value (Imax) and a minimum value (Imin) which respect the following quasi-uniformity criterion: Imax-lmoy) ⁇ 0.25.lmoy and (Imoy-lmin) ⁇ 0.25.lmoy;
• the diffusion means has a diffusion angle complementary to the emission angle of the point light sources, so that the light at the output of the diffusion means is emitted over 180 °; the emission angle of the point light sources is greater than or equal to 60 °;
• the overall light output p 'of the waveguide / diffusion means assembly is greater than 60%, and preferably greater than 70%; the light output (p) of the waveguide is greater than 70%, and preferably greater than 80%;
• the luminous intensity of at least one light source, and preferably of each light source (Si), is adjustable;
• the dipositif comprises at least two light sources (Sj) respectively having different emission wavelength ranges (Pi); - The device comprises at least three light sources (S 1 , S 2 , S 3 ) respectively having different emission wavelength ranges, which can overlap or not overlap; the device comprises three different light sources (Si, S 2 , S 3 ), a first light source (Si) being designed to transmit over a wavelength range between 450 nm and 60 nm, a second light source (S 2 ) being designed to transmit over a wavelength range between 400nm and 500nm, and a third light source (S 3 ) being designed to emit over a wavelength range between 600nm and 700nm;
• each light source (Sj) comprises a plurality of light-emitting diodes
• the waveguide comprises at least one solid solid body; more particularly, said solid body is made of polymer or glass;
• the waveguide comprises walls which are oriented parallel to the direction of propagation (Z) of the guide, whose inner faces are reflecting mirrors, and which delimit between them an internal cavity for propagation of light.
• FIG. 1 represents a first variant embodiment of a device of the invention
• FIG. 2 is a front view of the beam production module light of the device of Figure 1, said front view for viewing an example of spatial distribution of light sources;
• FIG. 3 is a schematic side view of the device of FIG. 1,
• FIG. 4 is an example of the emission spectra of the light sources of the device of FIG. 1
• FIGS. 5 to 14 represent measurement results of light intensities detected at the output of the waveguide of the device of FIG. 1. , for different length values of this waveguide,
• FIG. 15 shows in perspective another alternative embodiment of a waveguide.
• This device comprises three modules:
• a module 10 for producing light beams a waveguide 11 having a function of mixing the light beams produced by the module 10,
• the module 10 comprises a set of several point light sources in the form of light-emitting diodes 101 which are welded to a plate 102, and at least one power supply (not shown) which is connected to the diodes 101 by means of an etched electrical circuit on the plate, and which in known manner allows the ignition of the diodes 101.
• the light emitting diodes 101 are distributed in the configuration of Figure 2.
• the letters V identify green-colored diodes 101 which form a first light source S 1 extending over a range of wavelengths P 1, for example in the wavelength range 450 nm-600 nm;
• the letters B identify diodes 101 of blue color which form a second extended light source S 2 emitting over a range of wavelengths
• the letters R identify red-colored diodes 101 which form a third extended light source S 3 emitting over a range of wavelengths P 3, for example in the wavelength range 600 nm-700 nm.
• the invention is not limited to a device comprising the three extended light sources S 1 , S 2 , and S 3 mentioned above, but can be implemented with any light beam production module 10 comprising at least one extended light source which comprises several point light sources spaced apart and distributed along two orthogonal axes (X 1 Y).
• the light sources (Sj) may be identical (identical emission wavelengths) or different (light sources emitting at different wavelengths).
• the emission wavelength ranges of these sources may be different from the aforementioned wavelength ranges.
• the emission wavelength ranges of these sources may partially overlap or be disjoint.
• the light sources (Sj) are not necessarily arranged in the same plane, and do not necessarily consist of light-emitting diodes.
• the invention is also not limited to the particular configuration of diodes of FIG.
• the module 10 comprises means for adjusting the emission intensity of at least one of the light sources (S 1 to S 3 ), and preferably means allowing a separate adjustment of the emission intensity of each of the light sources (S 1 to S 3 ); these adjustment means make it possible to modify the light intensity ratios between the sources (S 1 to S 3 ), and thereby to adjust the color of the light produced at the output of the device 1 of the invention.
• the light intensity ratios between the sources (S 1 to S 3 ) may not be adjustable, and in this case the color of the light produced in output of the device 1 of the invention is not adjustable.
• the waveguide 11 is a solid solid body having a central axis of symmetry 11a, and made of a transparent material. This is for example a solid glass or plastic. In the particular example illustrated, it is a solid body of parallelepipedal shape, comprising:
• the light beams produced by the light sources S 1 to S 3 enter the waveguide 11 through its input face 110, and propagate in the longitudinal propagation direction Z which is parallel to the central axis of the waveguide 11.
• FIG. 3 illustrates by means of arrows examples of optical paths illustrating this propagation of light in the guide 11 by successive total reflections.
• these total reflections of the light waves inside the waveguide 11 are obtained by virtue of the index jump between the constituent material of the waveguide 11 and the air surrounding the guide 11.
• the length L of the waveguide 11 (that is to say with reference to FIGS. 1 and 3, the distance L separating the two input and output faces 110 in the direction of propagation Z) is set at case by case according to the quality sought for the spatial homogeneity of the color of the light produced at the output of the device 1. Examples of embodiment
• the input 110 and output 111 faces of the waveguide form a square approximately 50 mm apart;
• the diodes 101 are distributed according to the arrangement of FIG. 2, with a spacing x between two adjacent diodes along the X axis equal to 16 mm, and a spacing y between two adjacent diodes along the axis Y equal to 10mm;
• the diodes 101 are positioned against the input face 110 of the waveguide 11;
• a planar sensor for example a CCD matrix
• This sensor covers at least the entire output section of the waveguide 11 (surface of the output face 111 of the waveguide 11).
• This sensor makes it possible to measure the intensity in the plane (X 1 Y) of the light produced at the output of the device 1, in this case by means of the green light source (Si), over the entire output section of the waveguide. wave 11.
• the CCD matrix should preferably have a resolution sufficient to allow a measurement of at least 100 points over the entire output section of the waveguide 11 and according to a predefined axis (X axis in the examples below) ); the accuracy of the measurement shall be at least 1% of the power of the measuring point having the maximum power. It is also possible to use, in place of a CCD matrix, a point detector having the size of a measuring point, the measurement being made by moving this point detector over the entire output section of the guide 11 along the predefined measurement axis (X axis in the examples below).
• the left-hand view shows the spatial distribution at X and Y of the light intensities recorded by means of the sensor
• the right-hand view is a curve of the light intensities ⁇ 1 , x measured along the transverse axis X, for a given position along the Y axis (in this case on the left vertical edge of the waveguide 11), and over a range of measurements corresponding to the height (h) of the exit section of the guide
• this height (h) corresponds to the output section of the waveguide 11 along the axis (X).
• the reference 0 corresponds to the position at X of the central axis of symmetry 11a of the guide 11. It can be seen from FIGS. 5 to 11 that the longer the length L of the guide of FIG. wave
• FIG. 12 shows the profile of the light intensity li, x obtained with a waveguide 11 of length L equal to 60 mm, and in this FIG. 12 the three horizontal lines (in dotted lines) corresponding respectively to at the maximum intensity (Imax) measured along the X axis, at the minimum intensity (Imin) measured along the X axis, and at the average intensity (Imoy) measured according to X.
• the luminous intensity h , x for the source Si lies in a range of 30% around the average value Imoy [i.e. say:
• the maximum intensity Imax is 100
• the minimum intensity Imin is 62
• the average intensity is 80.
• (1max-1max) 0.25.lmoy
• (1mol-1min) 0.225lmoy.
• luminous intensities I 2 , x (blue diodes) and I 3, x (red diodes) are within a range of 30% around the average Imoy value.
• the distribution of the light intensity at the output of the waveguide 11 is thus almost uniform.
• the color of the light produced at the output of the waveguide 11 is, according to the invention, substantially uniform at all points in the space.
• This 30% limit value around the Imoy average value which defines the spatial quasi-uniformity of the color in the sense of the invention is related in practice to the sensitivity of the human eye. Beyond this limit, it is considered that the human eye is likely to detect color variations in space, which are not acceptable in terms of the quality of the light produced.
• the distribution of the light intensity li, x at the output of the waveguide 11 for the source Si is not quasi-uniform ((lmax-lmoy)> 0.3.lmoy) and ((Imoylmin)> 0.3.lmoy), and the devices concerned are therefore not in accordance with the invention.
• the length L of the waveguide 11 is an important parameter affecting the spatial uniformity of the light intensity of the light produced at the output of the device 1, but is not the only parameter.
• other parameters such as in particular the spatial distribution of the diodes 101 of the light sources Si, S 2 , S 3 , the emission angle of the diodes 101, the distance between the light sources Si, S 2 , S 3 and the input face 110 of the waveguide 11, also affect the spatial uniformity of the light intensity.
• the larger the cross section of the waveguide the greater the number of light propagation modes, and hence the longer the length of the waveguide L must be important to obtain the desired result of the waveguide. quasi-uniformity of the light intensities.
• the diffusion module 12 (FIG. 1) at the output of the waveguide 11 makes it possible to scatter light at the output of the waveguide 11 in all directions over 180 °.
• the light is completely mixed in all directions, and can no longer be broken down, for example using a prism.
• the diffusion module 12 has a diffusion angle ⁇ complementary to the emission angle ⁇ of the diodes 101.
• the diodes 101 have a total emission angle ⁇ of 60 °, the total diffusion angle ⁇ of the module 12 must be 120 ° to have at the output of this diffuser a source emitting on 180 ° .
• point sources 101 having a large emission angle ⁇ that is to say greater than or equal to
• the diffusion module 12 (whatever its embodiment) preferably has a low thickness so as not to degrade the light output too much.
• the diffusion module 12 is chosen so that the overall light output p 'of the waveguide / diffusion module 12 is greater than 60%, and preferably greater than 70%.
• the diffusion module 12 is for example a thin plate having many irregularities of structure. At the exit of the waveguide 11, the colored light passes through the diffusion plate 12 and undergoes multiple deviations (diffusion) due to the presence of irregularities in the structure of the plate 12.
• This diffusion plate could be replaced by any equivalent scattering element fulfilling the same function of light scattering.
• the plate 12 may be replaced by appropriate treatment of the exit face 111 of the waveguide 11, giving this exit face 111 a rough surface or equivalent (eg sandblasting).
• the diffusion module 12 is for example a holographic type diffuser whose total divergence angle of the light beam can be chosen between 1 ° and 160 °. This type of diffuser has the further advantage of having a transmission greater than 85%.
• the diffusion module 12 is for example a standard diffuser consisting of a glass plate, at least one of which has been sandblasted to give it a roughness that makes it possible to obtain the required divergence of the light beams.
• the diffusion module 12 may also be a tinted glass in which the diffusion is obtained by incorporating diffusing elements inside the glass (barium sulphate, for example).
• the diffusion must be in all directions and with the lowest possible loss of light power.
• Second waveguide embodiment mirrors
• the waveguide 11 of FIG. 1 is replaced by the guide 11 'of FIG. 15.
• This guide 11' consists of four walls 112 which are oriented parallel to the direction of propagation (Z ) of the guide, and which delimit between them an internal cavity 113 having a central axis of symmetry 11a and allowing the propagation of light.
• the internal faces 112a of the walls 112 constitute reflecting mirrors allowing the propagation of the light in the cavity 113 by total reflections in the direction (Z).
• the length L of the guide is adapted by applying the same teaching as that given above for the length L of the guide 11 of FIG. 1, so as to obtain the result of the quasi-uniformity of the light intensities at the output of the waveguide.
• the cross section of the waveguide is rectangular. This is not limiting of the invention. In other variants, the section of the waveguide may be different, and may more generally form a polygon or a circle.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Planar Illumination Modules (AREA)
• Light Guides In General And Applications Therefor (AREA)

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• 2007
  • 2007-03-20 EP EP07731163A patent/EP2005060A2/de not_active Withdrawn
  • 2007-03-20 US US12/225,406 patent/US8011800B2/en not_active Expired - Fee Related
  • 2007-03-20 WO PCT/FR2007/000473 patent/WO2007107650A2/fr not_active Ceased

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