3D PRINTED REFLECTOR AND METHOD FOR ITS MANUFACTURE

Abstract

The invention provides a reflector (2) comprising a reflector wall (20), the reflector wall (20) comprising a first wall surface (22) and a second wall surface (23) defining said reflector wall (20), the reflector wall (20) comprising a light transmissive material (21), wherein the reflector wall (20) has a first dimension (d1) and a second dimension (d2) defining a first reflector wall area, wherein each wall surface (22,23) comprises a plurality of parallel arranged elongated corrugations (210), wherein the corrugations have corrugation heights (h2) relative to recesses (220) between adjacent corrugations (210) and corrugation widths (w2) defined by the distance between adjacent recesses (220) at the respective wall surfaces (22,23), wherein the corrugations (210) have curved corrugation surfaces (230) between said adjacent recesses (220) having corrugation radii (r2) at the respective wall surfaces (22,23), and wherein over at least part of one of the first dimension (d1) and the second dimension (d2) one or more of (i) the corrugation heights (h2), (ii) the corrugation widths (w2), (iii) the corrugation radii (r2), and (iv) a shortest top-top distance (w12) of corrugations tops (211) configured at different wall surfaces (22,23) vary over said wall dimension (d1,d2) for at least one of the wall surfaces (22,23). The reflector (2) has a first end (3) and a second end (4), wherein a third distance (d3) between the first end (3) and the second end (4) is bridged by one or more reflector walls (20), wherein the one or more reflector walls (20) are configured tapering from the second end (4) to the first end (3), and wherein the reflector (2) has a reflector cavity (5).

Claims

1. A reflector comprising a reflector wall, the reflector wall comprising a first wall surface and a second wall surface defining said reflector wall, the reflector wall comprising a light transmissive material, wherein the reflector wall has a first dimension and a second dimension defining a first reflector wall area, wherein each wall surface comprises a plurality of parallel arranged elongated corrugations, wherein the corrugations have corrugation heights relative to recesses between adjacent corrugations and corrugation widths defined by the distance between adjacent recesses at the respective wall surfaces, wherein the corrugations have curved corrugation surfaces between said adjacent recesses having corrugation radii at the respective wall surfaces, and wherein over at least part of one of the first dimension and the second dimension one or more of (i) the corrugation heights, (ii) the corrugation widths, (iii) the corrugation radii, and (iv) a shortest top-top distance of corrugations tops configured at different wall surfaces vary over said wall dimension for at least one of the wall surfaces, wherein the reflector has a first end and a second end, wherein a third distance between the first end and the second end is bridged by one or more reflector walls, wherein the one or more reflector walls are configured tapering from the second end to the first end, and wherein the reflector has a reflector cavity.

2. The reflector according to claim 1, wherein the reflector wall is a fused deposition modeling printed reflector wall and wherein the corrugations are defined by filament surfaces.

3. The reflector according to claim 1, wherein the reflector wall comprises one or more of PC, PET, PLA and PMMA.

4. The reflector according to claim 1, comprising sets of corrugations with a first corrugation at the first wall surface and a second corrugation at the second wall surface with said shortest top-top distance between a first corrugation top of the first corrugation at the first wall surface and a second corrugation top of the second corrugation at the second wall surface selected from the range of 0.01w2/w12100.

5. The reflector according to claim 1, wherein the reflector has an elongated V-shape or has a conical shape.

6. A lighting system comprising a light source configured to provide light source light and a reflector according to claim 1, wherein the reflector is configured to reflect at least part of the light source light.

7. The lighting system according to claim 6, wherein the reflector is configured to collimate at least part of the light source light.

8. The lighting system according to claim 6, wherein the reflector has a first end and a second end, wherein a third distance between the first end and the second end is bridged by one or more reflector walls, wherein the one or more reflector walls are configured tapering from the second end to the first end, and wherein the reflector has a reflector cavity.

9. The lighting system according to claim 8, wherein the light source comprises a light exit face, and wherein the light exit face is configured at the first end or wherein the light source is configured to provide said light source light into said cavity through one or more reflector walls.

10. The lighting system according to claim 6, further comprising a second reflector configured to redirect at least part of light source light that escapes through one or more reflector walls back through the one or more walls into said reflector cavity.

11. A method for manufacturing a reflector, wherein the reflector comprises a reflector wall, the reflector wall comprising a first wall surface and a second wall surface defining said reflector wall, the reflector wall comprising a light transmissive material, wherein the reflector wall has a first dimension and a second dimension defining a first reflector wall area, wherein each wall surface comprises a plurality of parallel arranged elongated corrugations, wherein the corrugations have corrugation heights relative to recesses between adjacent corrugations and corrugation widths defined by the distance between adjacent recesses at the respective wall surfaces, wherein the corrugations have curved corrugation surfaces between said adjacent recesses having corrugation radii at the respective wall surfaces, wherein the method comprises providing a filament of 3D printable material and printing during a printing stage said 3D printable material on a receiver item with a fused deposition modeling (FDM) 3D printer, to provide said reflector, wherein the printing stage comprises varying over at least part of one of the first dimension and the second dimension one or more of (i) the corrugation heights, (ii) the corrugation widths, (iii) the corrugation radii, and (iv) a shortest top-top distance of corrugations tops configured at different wall surfaces over said wall dimension for at least one of the wall surfaces by controlling 3D printer method parameters.

12. The method according to claim 11, wherein the method comprises defining a desired distribution of light after reflection of light of a light source at a reflector surface, defining a design of a 3D printable reflector that meets best said desired distribution of light when combined with the light source, and printing said reflector in dependence of said design, wherein the printing stage comprises controlling one or more of a deposition speed and a printer nozzle opening dimension for providing said variation over said wall dimension for at least one of the wall surfaces.

13. The method according to claims 12, wherein the reflector comprises sets of corrugations with a first corrugation at the first wall surface and a second corrugation at the second wall surface with said shortest top-top distance between a first corrugation top of the first corrugation at the first wall surface and a second corrugation top of the second corrugation at the second wall surface selected from the range of 0.01w2/w12100, wherein w2/w12 varies over said wall dimension for at least one of the wall surfaces, and wherein the method comprises providing said variation in w2/w12 varies over said wall dimension by controlling one or more of said deposition speed and said printer nozzle opening dimension.

14. A computer program product, which when loaded on a computer is capable of bringing about the method as described in claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] 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:

[0053] FIGS. 1a-1b schematically depict some general aspects of a 3D printer that may be used in the method described herein;

[0054] FIGS. 2a-2f schematically depict some aspects and variants of the reflector;

[0055] FIGS. 3-8 schematically depict some aspects and variants of the reflector and lighting system;

[0056] FIGS. 9a-9b and 10a-10b schematically depict some embodiments of the reflector and lighting system.

[0057] The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] FIG. 1a schematically depicts some aspects of the 3D printer. Reference 500 indicates a 3D printer, herein also indicated as fused deposition modeling 3D printer. Reference 530 indicates the functional unit configured to 3D print, especially FDM 3D printing; this reference may also indicate the 3D printing stage unit. Here, only the printer head for providing 3D printed material, such as a FDM 3D printer head is schematically depicted. Reference 501 indicates the printer head. The 3D printer of the present invention may especially include a plurality of printer heads, though other embodiments are also possible. Reference 502 indicates a printer nozzle. The 3D printer of the present invention may especially include a plurality of printer nozzles, though other embodiments are also possible. Reference 320 indicates a filament of printable 3D printable material (such as indicated above). For the sake of clarity, not all features of the 3D printer have been depicted, only those that are of especial relevance for the present invention (see further also below).

[0059] The 3D printer 500 is configured to generate a 3D item 10 by depositing on a receiver item 550, which may in embodiments at least temporarily be cooled, a plurality of filaments 320 wherein each filament 20 comprises 3D printable material, such as having a melting point T.sub.m. The 3D printer 500 is configured to heat the filament material upstream of the printer nozzle 502. This may e.g. be done with a device comprising one or more of an extrusion and/or heating function. Such device is indicated with reference 573, and is arranged upstream from the printer nozzle 502 (i.e. in time before the filament material leaves the printer nozzle 502). The printer head 501 may (thus) include a liquefier or heater. Reference 201 indicates printable material. When deposited, this material is indicated as (3D) printed material, which is indicated with reference 202.

[0060] Reference 572 indicates a spool or roller with material, especially in the form of a wire. The 3D printer 500 transforms this in a filament or fiber 320 on the receiver item or on already deposited printed material. In general, the diameter of the filament downstream of the nozzle is reduced relative to the diameter of the filament upstream of the printer head. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging filament by filament and filament on filament, a 3D item 10 may be formed. Reference 575 indicates the filament providing device, which here amongst others include the spool or roller and the driver wheels, indicated with reference 576.

[0061] Reference A indicates a longitudinal axis or filament axis.

[0062] FIG. 1b schematically depicts in 3D in more detail the printing of the 3D item 10 under construction. Here, in this schematic drawing the ends of the filaments 320 in a single plane are not interconnected, though in reality this may in embodiments be the case.

[0063] Hence, FIGS. 1a-1b schematically depict some aspects of a fused deposition modeling 3D printer 500, comprising (a) a first printer head 501 comprising a printer nozzle 502, (b) a filament providing device 575 configured to provide a filament 320 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a receiver item 550.

[0064] A 3D printed (FDM) structure exhibits a rippled surface. These ripples surprisingly appear to be exceptionally useful in the printing of clear materials because they can act as biconvex cylinder lenses which are perfectly aligned in the 3D printing process. In all of these concepts, proper alignment of these linear structures is not trivial.

[0065] A 3D printing product is very schematically shown in FIG. 2a. This drawing may schematically depict the printer nozzle 501 of the 3D printer schematically depicted in FIG. 1a. The printer nozzle opening dimension is indicated with reference d4. In specific embodiments, the 3D printer 500 may have a variable printer nozzle opening dimension d4. In this way, the thickness or diameter of the printed filament may be controlled (during printing).

[0066] Geometric parameters in the design are amongst others the aspect ratio (w2/w12) of the layers and the curvature at the polymer/air interface. The parameters are explained in FIGS. 2a and 2b. The aspect ratio of the layers and curvature of the interfaces can be tuned by the processing conditions (printing speed, polymer flow) in the 3D printing process. Reference h2 indicates the corrugation height. The corrugations are indicated with reference 210. Reference w2 indicates a corrugation width and reference R2 indicates a radius of curved corrugation surfaces 230. Angle 2 is the angle which the corrugation surface 230 spans (in cross-section the circular segment with central angle), which will in general be in the range of 30-150, especially in the range of 45-135, such as 60-120. Reference w12 indicates the width or length between two corrugation tops. The corrugation tops are indicated with reference 211. The corrugations 210 are provided by filament surfaces 321. Tops 211 defining w12 are herein also indicated as corresponding corrugation tops. The variation in one or more parameters is in a direction perpendicular to the elongated structures. This is by way of example in this drawing indicated with the arrow (note that the variation itself is here in w12, the top-top distance).

[0067] FIG. 2c schematically depicts, in perspective view, a wall 20 of a reflector 2 in some more detail. The reflector 2 comprises a reflector wall 20. The reflector wall 20 comprising a first wall surface 22 and a second wall surface 23 defining the reflector wall 20. The two faces 22,23 are configured opposite of each other and are configured substantially parallel to each other. The reflector wall 20 comprises a light transmissive material 21. The reflector wall 20 has a first dimension dl and a second dimension d2 defining a first reflector wall area A. Each wall surface 22,23 comprises a plurality of parallel arranged elongated corrugations 210. The corrugations have corrugation heights h2 relative to recesses 220 between adjacent corrugations 210 and corrugation widths w2 defined by the distance between adjacent recesses 220 at the respective wall surfaces 22,23. The corrugations 210 have curved corrugation surfaces 230 between said adjacent recesses 220 having corrugation radii r2. Though not shown in FIG. 2c, over at least part of one of the first dimension d1 and the second dimension d2 one or more of (i) the corrugation heights h2, (ii) the corrugation widths w2, (iii) the corrugation radii r2, and (iv) a shortest top-top distance w12 of corrugations tops 211 configured at different wall surfaces 22,23 vary the dimension d1,d2 for at least one of the wall surfaces 22,23, especially both surfaces 22,23. References 3 and 4 indicate a first end 3 and second 4 of the wall, respectively. FIG. 2c schematically depict four corrugations at the first wall surface 22 and the second wall surface 23, respectively. A reflector wall may comprise about 1-100 corrugations/cm over a first dimension (here d1). In FIG. 2c, the corrugations 210 are parallel to the dimension d2. The corrugations 210 have (elongated) corrugations tops 211 and are configured between (elongated) recesses 220. Especially, the variation in one or more parameters is in a direction perpendicular to those elongated structures. This is by way of example in this drawing indicated with the arrow (note that the variation itself is not visible). This variation may thus especially include a gradient in one or more of the corrugation heights, corrugation widths, corrugation radii, and top-top distances over the reflector wall surfaces, especially such gradient in a single direction (parallel to one of the wall dimensions) as schematically depicted here.

[0068] FIG. 2d and FIG. 2e schematically an embodiment wherein the reflector 2 has a first end 3 and a second end 4, wherein a third distance d3 between the first end 3 and the second end 4 is bridged by one or more reflector walls 20, wherein the one or more reflector walls 20 are configured tapering from the second end 4 to the first end 3, and wherein the reflector 2 has a reflector cavity 5. Here, the reflector 2 has a conical shape. FIG. 2d schematically also depicts a lighting system 1 comprising a light source 10 configured to provide light source light 11 and the reflector 2 which is configured to reflect at least part of the light source light 11. Hence, the reflector is configured in a light receiving relationship with the light source. For instance, in the schematically depicted embodiment of FIG. 2d the reflector 2 is configured to collimate at least part of the light source light 11. FIG. 2d also shows that a third distance d3 between the first end 3 and the second end 4 is bridged by one or more reflector walls 20, here in fact a single reflector wall 20, wherein the one or more reflector walls 20 are configured tapering from the second end 4 to the first end 3. The reflector 2 has a reflector cavity 5. Note that the reflector wall 20 of FIG. 2d has a curvature in a first dimension d2 (diameter), but does not necessarily have an overall curvature in the other dimension d1 (length or height of wall 20). The light source 10 comprises a light exit face 12. In the embodiment schematically depicted in FIG. 2d, the light exit face 12 is configured at the first end 3. The light exit face 12 may in embodiments be configured within the cavity 5. Note that not all light source light is necessarily directed to the reflector; in embodiments part of the light source light may also propagate from the light source without coming into contact with the reflector. FIG. 2e schematically depicts a cross-section. Note that d2 may depend upon the distance of the filament 320/curvature 210 from a first end 3 or second end 4.

[0069] FIG. 2f schematically depicts a perspective view of a V-shape reflector 2. The reflector has a kind of trough shape or hollow triangular shaped prism. Further, FIG. 2f also schematically depicts an embodiment of the lighting system 1. Here, by way of example the lighting system 1 includes a plurality of light sources 10.

[0070] The printing material may especially be a clear polycarbonate (PC), PET, PLA or PMMA. Also mixture of two or more clear materials may be used as well. A cross section of a 3D print using clear PET is shown in FIG. 3. The printed component is the reflector (or part of a compound reflector) in a LED based luminaire.

[0071] FIG. 4 depicts a ray-tracing example of the reflectivity of the reflector wall 20. Reference indicates the angle of incidence. Further, from this figure it can also be concluded that at other angles of incidence the dimensions of the corrugations 210 may be different in order to provide the desired directionality and/or angular distribution of the reflected light. Hence, with (a) light source(s) at a fixed position, dependent upon the angle of incidence of the light source light the dimensions of the corrugations 210 may be designed.

[0072] Hence, the working principle of the invention is explained in FIG. 4. An incoming light beam is transmitted by the first lens surface and reflected (total internal reflection; TIR) by a second lens surface on the opposite site of the sheet. The second lens is shifted over a distance d with respect to the first lens. The printed structures are defined by the parameters w12,w2, R2 and (FIG. 2b) and the refractive index n of the polymer.

[0073] This is also schematically depicted in FIG. 5, wherein the angle of incidence is varied. On the y-axis the reflectivity in % is indicated, on the y-axis v is indicated. Reference v is related to w12 (with v=w122*h2). As can be seen in FIG. 5, with tuning the corrugation width w2 from about 0.5 to 0.7 mm the maximum of the reflection can shift the optimal angle of incidence from 70 to 60. FIG. 5 shows some typical configurations. At around v=0.62 mm, the reflectance of the printed structure becomes 92% at an angle of incidence of 60 with respect to the normal to the printed sheet surface. At an angle of incidence of 70 structures with v around 0.53 mm show an even higher reflectance of 95%.

[0074] FIG. 6 shows the angular distribution of the reflected beam (at 60) for a beam with an angle of incidence of 60. As can be seen, the reflection is substantially specular. FIG. 6 shows that the reflected light is confined in a narrow cone of light which is perceived as a specular reflecting/silverish surface. RB indicates reflected beam and IB indicates beam of incidence. The x-axis indicates the angle (). As can be seen, there is a substantially mirror like reflection with the beam of incidence at about 60 and the reflected beam at 60.

[0075] In FIGS. 4-6, as material polycarbonate with a refractive index of 1.59 was applied, with w2 being 0.6 mm, with r2 being 0.5 mm, and with h2 being 0.1 mm.

[0076] FIG. 7 depicts a simple optical model is depicted, explaining the shape of the structures at which a specular reflection is expected. The model relates geometry of the printed structures to the angle of incidence at which specular reflection occurs.

[0077] is the angle of incidence. The angle is defined above and can also be defined as arcsin (w2/(2*R2)).

[0078] Some results of the model are given in FIG. 8 for three different lens curvatures 1/R and a range of incident angles . 3D printed layers have typical dimensions in the range 0.05 mm and 2 mm.

[0079] In FIGS. 9a-b, a 3D printed clear reflector is applied to shape the intensity profile of at least one light emitting diode (LED). Because the reflectance of the printed layers is strongly dependent on the incident angle, a small area source is helpful to achieve effective collimation. An attractive source for the described construction is a so-called COB (Chip On Board). These LEDs combine a high flux (typically 500-2500 lm) with a small footprint (<13 mm diameter). Nevertheless, some light leaks through the printed collimator to the outside. However, for many applications, such a reflector is highly appreciated (compare e.g. to the leakage of some light through a reflector of a halogen bulb). In the off-state, the luminaire show a silverish appearance at specific viewing angles. This effect is highly appreciated as well. The complete reflector can have a great variety of geometries (round, linear, free-form). The walls of the reflector can be straight or curved (preferred to optimize reflectance for all incident angles). By manipulating the shape of the reflector, it is possible to tune the amount of reflected and transmitted (leaked) light and the far-field intensity distribution of the luminaire. The reflector wall 20 comprises first wall surface 22 and second wall surface 23. First wall surface 22 may also be indicated as cavity surface. Second wall surface 23 may also be indicated as external surface. FIG. 9a schematically depicts a cross-section of e.g. a conically shaped reflector 2 (see FIG. 2d) or a V-shape reflector 2 (see FIG. 2f). Further, FIG. 9a also schematically depicts an embodiment of the lighting system 1. Here, the cavity 5 is tapering from the second end 4 to the first end 3. As can be derived from FIG. 9a, but also be derived from other drawings, such as 2d, etc., the light source 10 generating rays of light 11 towards the reflector wall 20 provide rays that have a shorter path length to a wall surface 22 and rays that have a longer path length to the (same) wall surface 22.

[0080] FIGS. 10a-b show an alternative construction in which a clear 3D printed reflector 2 is combined with a reflector 300, such as a white, diffuse reflector or a classical specular reflector (e.g. an aluminum coated polymer). The white reflector can be 3D printed as well. The upper part of the clear polymer element is the reflector, while the lower part (close to the LEDs) may (also) act as diffuser for the light source light 11 of a light source, such as a high brightness LEDs. Such a construction allows also a large variety of forms and shapes. In FIG. 10a, and especially FIG. 10b a linear structure is shown. The polymer reflector can be printed in (at least) two orientations. One option is depicted in FIGS. 10a-b, with FIG. b being a top view of FIG. 10a. Here, the reflector 2 has a kind of U shape, or a V-shape with a rounded first (tapering) end 3.

[0081] The term substantially herein, such as in substantially consists, will be understood by the person skilled in the art. The term substantially may also include embodiments with entirely, completely, all, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term substantially 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.

[0082] 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.

[0083] The devices herein are amongst others 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 in operation.

[0084] 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. 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 the device 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.

[0085] The invention further applies to a device 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.

[0086] 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.