Patent Publication Number: US-11662082-B2

Title: Optical device for modifying light distribution

Description:
This application is the U.S. national phase of International Application No. PCT/FI2020/050029 filed Jan. 17, 2020 which designated the U.S. and claims priority to FI Patent Application No. 20195287 filed Apr. 8, 2019, the entire contents of each of which are hereby incorporated by reference. 
     FIELD OF THE DISCLOSURE 
     The disclosure relates generally to illumination engineering. More particularly, the disclosure relates to an optical device for modifying a distribution of light produced by a light source that can be, for example but not necessarily, a light emitting diode “LED”. 
     BACKGROUND 
     A distribution of light produced by a light source can be important or even critical in some applications. The light source can be, for example but not necessarily, a light emitting diode “LED”, a filament lamp, or a gas-discharge lamp. The distribution of light produced by a light source can be modified with optical devices such as lenses, reflectors, and combined lens-reflector devices that comprise sections which act as lenses and sections which act as reflectors. In many cases there is a need for an optical device that is adjustable for tuning a shape of a light distribution pattern produced by a light source and the optical device. For example, there can be a need to change a width of a light distribution pattern smoothly between a narrow light distribution pattern for illuminating a spot and a wider light distribution pattern for illuminating a larger area. 
     Publication WO2006072885 describes an optical device for adjusting a shape of a light distribution pattern. The optical device of WO2006072885 comprises a first optical element and a second optical element for modifying a distribution of light produced by a light source. The first and second optical elements are successively in a pathway of the light so that the second optical element receives the light exiting the first optical element. The optical device of WO2006072885 comprises an adjustment mechanism for adjusting the distance between the first and second optical elements along the optical axis of the optical device and thereby for varying the shape of the light distribution pattern. An inconvenience related to the optical device of WO2006072885 is the need for the adjustment mechanism for adjusting the distance between the first and second optical elements along the optical axis of the optical device. A further inconvenience related to the optical device of WO2006072885 is that the physical length of the optical device is changing when the shape of the light distribution pattern is changed. The changing physical length is an unwanted property in conjunction with many illumination applications e.g. in cases where optical devices are embedded in ceiling or wall structures so that a front surface of each optical device is substantially in flush with a wall or ceiling surface. 
     SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention. 
     In this document, the word “geometric” when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional. 
     In accordance with the invention, there is provided a new optical device for modifying a distribution of light produced by a light source. 
     An optical device according to the invention comprises:
         a first optical element being a first piece of transparent material and comprising a first surface for modifying a distribution of light exiting the first optical element through the first surface, and   a second optical element being a second piece of transparent material and comprising a second surface facing towards the first surface and for further modifying the distribution of the light entering the second optical element through the second surface.       

     The second optical element is rotatable with respect to the first optical element around a geometric optical axis of the optical device. One of the above-mentioned first and second surfaces comprises convex areas and the other one of the first and second surfaces comprises concave areas for at least partly compensating for an optical effect of the convex areas when the second optical element is in a first rotational position with respect to the first optical element so that the convex areas and the concave areas are aligned with respect to each other. A combined optical effect of the first and second surfaces is changeable by rotating the second optical element from the first rotational position towards a second rotational position in which the concave areas and the convex areas are non-aligned with respect to each other. Therefore, a shape of a light distribution pattern can be varied without changing the distance between the first and second optical elements i.e. without changing the physical length of the optical device. 
     The first and second optical elements comprise sliding surfaces for sliding with respect to each other and for mechanically supporting the first and second optical elements with respect to each other in radial directions perpendicular to the geometric optical axis. Therefore, a mechanical structure for supporting the first and second optical elements can be simpler than in a case where optical elements that are rotatable with respect to each other are not provided with sliding surfaces for keeping the optical elements in a desired radial position with respect to each other. 
     In accordance with the invention, there is provided also a new illumination device that comprises:
         a light source, and   an optical device according to the invention for modifying a distribution of light emitted by the light source.       

     The light source may comprise for example one or more light emitting diodes “LED”. 
     In accordance with the invention, there is provided also a new mold set that comprises:
         a first mold having a form suitable for manufacturing, by mold casting, a first piece of transparent material constituting the first optical element of an optical device according to the invention, and   a second mold having a form suitable for manufacturing, by mold casting, a second piece of transparent material constituting the second optical element of the optical device according to the invention.       

     Exemplifying and non-limiting embodiments are described in accompanied dependent claims. 
     Various exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in conjunction with the accompanying drawings. 
     The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below with reference to the accompanying drawings, in which: 
         FIGS.  1   a  and  1   b    illustrate details of an optical device according to an exemplifying and non-limiting embodiment, 
         FIGS.  2   a  and  2   b    illustrate details of an optical device according to another exemplifying and non-limiting embodiment, 
         FIGS.  3   a ,  3   b ,  3   c , and  3   d    illustrate an optical device according to an exemplifying and non-limiting embodiment, 
         FIGS.  4   a ,  4   b ,  4   c , and  4   d    illustrate an optical device according to an exemplifying and non-limiting embodiment, 
         FIGS.  5  and  6    illustrate details of optical devices according to exemplifying and non-limiting embodiments, and 
         FIG.  7   a    illustrates light distribution patterns produced by an illumination device according to an exemplifying and non-limiting embodiment shown in  FIG.  7     b.    
     
    
    
     DESCRIPTION OF EXEMPLIFYING AND NON-LIMITING EMBODIMENTS 
     The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated. 
       FIGS.  1   a  and  1   b    illustrate details of an optical device according to an exemplifying and non-limiting embodiment. The optical device comprises a first optical element  102  that comprises a first surface  104  for modifying a distribution of light exiting the first optical element  102  through the first surface  104 . The optical device comprises a second optical element  103  that comprises a second surface  105  facing towards the first surface  104  of the first optical element  102 . The second surface  105  is suitable for further modifying the distribution of the light that has exited the first optical element  102 . In  FIGS.  1   a  and  1   b   , exemplifying light beams are depicted with dashed line arrows. The second optical element  103  is mechanically supported with respect to the first optical element  102  so that the second surface  105  is movable with respect to the first surface  104  in parallel with the first surface  104 . In this exemplifying optical device, the first surface  104  comprises convex areas and the second surface  105  comprises concave areas. In  FIGS.  1   a  and  1   b   , one of the convex areas of the first surface  104  is denoted with a reference  106  and one of the concave areas of the second surface  105  is denoted with a reference  107 . It is however also possible that the second surface  105  comprises convex areas and the first surface  104  comprises concave areas. As shown in  FIG.  1   a   , the concave areas of the second surface  105  compensate at least partly for an optical effect of the convex areas of the first surface  104  when the second optical element  103  is in a first position with respect to the first optical element  102  so that the concave areas of the second surface  105  are aligned with the convex areas of the first surface  104 . A combined optical effect of the first and second surfaces  104  and  105  is changeable by moving the second optical element  103  with respect to the first optical element  102 .  FIG.  1   b    shows an exemplifying situation in which the second optical element  103  is in a second position with respect to the first optical element  102  so that the concave areas of the second surface  105  are not aligned with the convex areas of the first surface  104 . As illustrated in  FIG.  1   b   , the optical device spreads the originally collimated light. 
       FIGS.  2   a  and  2   b    illustrate details of an optical device according to another exemplifying and non-limiting embodiment. The optical device comprises a first optical element  202  that comprises a first surface  204  for modifying a distribution of light exiting the first optical element  202  through the first surface  204 . The optical device comprises a second optical element  203  that comprises a second surface  205  facing towards the first surface  204  of the first optical element  202 . The second surface  205  is suitable for further modifying the distribution of the light that has exited the first optical element  202 . In  FIGS.  2   a  and  2   b   , exemplifying light beams are depicted with dashed line arrows. The second optical element  203  is mechanically supported with respect to the first optical element  202  so that the second surface  205  is movable with respect to the first surface  204  in parallel with the first surface. In this exemplifying optical device, the first surface  204  comprises convex areas and concave areas between the convex areas. Correspondingly, the second surface  205  comprises convex areas and concave areas between the convex areas. In  FIGS.  2   a  and  2   b   , one of the convex areas of the first surface  204  is denoted with a reference  206  and one of the concave areas of the second surface  205  is denoted with a reference  207 . As shown in  FIG.  2   a   , the concave areas of the second surface  205  compensate at least partly for an optical effect of the convex areas of the first surface  204  and correspondingly the convex areas of the second surface  205  compensate at least partly for an optical effect of the concave areas of the first surface  204  when the second optical element  203  is in a first position with respect to the first optical element  202  so that the concave areas of the second surface  205  are aligned with the convex areas of the first surface  204 . A combined optical effect of the first and second surfaces  204  and  205  is changeable by moving the second optical element  203  with respect to the first optical element  202 .  FIG.  2   b    shows an exemplifying situation in which the second optical element  203  is in a second position with respect to the first optical element  202  so that the concave areas of the second surface  205  and the convex areas of the first surface  204  are not aligned with respect to each other. As illustrated in  FIG.  2   b   , the optical device spreads the originally collimated light. 
       FIGS.  3   a  and  3   b    show section views of an optical device  301  according to an exemplifying and non-limiting embodiment. The geometric section planes are parallel with the xz-plane of a coordinate system  399 . The optical device  301  comprises a first optical element  302  that is a piece of transparent material and comprises a first surface  304  for modifying a distribution of light exiting the first optical element  302  through the first surface  304 . The optical device  301  comprises a second optical element  303  that is a piece of transparent material and comprises a second surface  305  facing towards the first surface  304  of the first optical element  302 . The second surface  305  is suitable for further modifying the distribution of the light that has exited the first optical element  302 . The second optical element  303  is rotatable with respect to the first optical element  302  around a geometric optical axis  313  of the optical device  301 . The geometric optical axis  313  is parallel with the z-axis of the coordinate system  399 .  FIG.  3   c    shows an isometric view of the first optical element  302 , and  FIG.  3   d    shows an isometric view of the second optical element  303 . 
     The first and second optical elements  302  and  303  comprise sliding surfaces  309  and  310  for sliding with respect to each other and for mechanically supporting the first and second optical elements  302  and  303  with respect to each other at least in radial directions perpendicular to the geometric optical axis  313 . In this exemplifying optical device  301 , the first optical element  302  comprises a cavity that is concentric with the geometric optical axis  313  and the second optical element  303  comprises a projection that is concentric with the geometric optical axis and is in the cavity of the first optical element. Walls of the cavity and the projection constitute the sliding surfaces  309  and  310  for supporting the first and second optical elements with respect to each other. In this exemplifying case, the sliding surfaces  309  and  310  have first portions perpendicular to the radial directions and second portions perpendicular to the geometric optical axis  313 . The first portions of the sliding surfaces comprise a cylindrical side surface of the cavity of the first optical element  302  and a cylindrical side surface of the projection of the second optical element  303 , and they support the first and second optical elements  302  and  303  with respect to each other in the radial directions. The second portions of the sliding surfaces comprise a part of the bottom of the cavity and a part of an end-surface of the projection, and they support the first and second optical elements  302  and  303  with respect to each other in an axial direction parallel with the geometric optical axis. In this exemplifying case, the second portions of the sliding surfaces determine a minimum distance between the first and second surfaces  304  and  305 . It is also possible that first and second optical elements of an optical device according to an exemplifying and non-limiting embodiment comprise e.g. conical sliding surfaces. 
     In the exemplifying optical device  301  illustrated in  FIGS.  3   a - 3   d   , the bottom of the cavity of the first optical element  302  constitutes a part of the optically active first surface  304  and correspondingly the end-surface of the projection of the second optical element  303  constitutes a part of the optically active second surface  305 . In this exemplifying case, the projection of the second optical element  302  is hollow as illustrated in  FIGS.  3   a  and  3   b   . Therefore, light that propagates in the projection of the second optical element  303  is attenuated less by the transparent material of the second optical element  303  than in a case where a corresponding projection is solid i.e. not hollow. Thus, the construction of the optical device  301  illustrated in  FIGS.  3   a - 3   d    is advantageous concerning the mechanical support between the optical elements  302  and  303  as well as optical properties of the optical device  301 . 
     In the exemplifying optical device  301  illustrated in  FIGS.  3   a - 3   d   , the first optical element  302  comprises a reflector surface  308  for providing total internal reflection “TIR” to reflect light to the above-mentioned first surface  304 . The reflector surface  308  and a surface of the first optical element  302  for receiving the light from a point-form light source  311  can be shaped for example so that the reflected light is collimated light when the point-form light source  311  is in a predetermined position with respect to the optical device  301 . In  FIGS.  3   a  and  3   b   , exemplifying light beams are depicted with dashed line arrows. 
     In the exemplifying optical device  301  illustrated in  FIGS.  3   a - 3   d   , the above-mentioned first surface  304  of the first optical element  302  comprises convex areas and concave areas between the convex areas. Correspondingly, the above-mentioned second surface  305  of the second optical element  303  comprises convex areas and concave areas between the convex areas. As shown in  FIG.  3   a   , the concave areas of the second surface  305  of the second optical element  303  compensate at least partly for an optical effect of the convex areas of the first surface  304  of the first optical element  302  and correspondingly the convex areas of the second surface  305  compensate at least partly for an optical effect of the concave areas of the first surface  304  when the second optical element  303  is in a first rotational position with respect to the first optical element  302  so that the concave areas of the second surface  305  are aligned with the convex areas of the first surface  304 . A combined optical effect of the first and second surfaces is changeable by rotating the second optical element  303  with respect to the first optical element  302  around the geometric optical axis  313  of the optical device  301 .  FIG.  3   b    shows an exemplifying situation in which the second optical element  303  has been rotated so that the concave areas of the second surface  305  of the second optical element  303  are not aligned with the convex areas of the first surface  304  of the first optical element  302 . As illustrated in  FIG.  3   b   , the first and second surfaces spread the light arriving from the reflector surface  308 . 
     The first and second optical elements  302  and  303  can be manufactured for example with mold casting. The first optical element  302  can be made of for example acrylic plastic, polycarbonate, optical silicone, or glass. Correspondingly, the second optical element  303  can be made of for example acrylic plastic, polycarbonate, optical silicone, or glass. 
     The optical device  301  and the light source  311  shown in  FIGS.  3   a  and  3   b    constitute an illumination device according to an exemplifying and non-limiting embodiment. The illumination device further comprises mechanical support structures for mechanically supporting the optical device  301  and the light source  311 . The mechanical support structures are not shown in  FIGS.  3   a    and  3   b.    
       FIGS.  4   a  and  4   b    show section views of an optical device  401  according to an exemplifying and non-limiting embodiment. The geometric section planes are parallel with the xz-plane of a coordinate system  499 . The optical device comprises a first optical element  402  that is a piece of transparent material and comprises a first surface  404  for modifying a distribution of light exiting the first optical element  402  through the first surface. In this exemplifying optical device  401 , the first optical element  402  comprises a reflector surface  408  for providing total internal reflection “TIR” to reflect light to the above-mentioned first surface  404 . In  FIGS.  4   a  and  4   b   , exemplifying light beams are depicted with dashed line arrows. The optical device  401  comprises a second optical element  403  that is a piece of transparent material and comprises a second surface  405  facing towards the first surface  404  of the first optical element  402 . The second surface is suitable for further modifying the distribution of the light that has exited the first optical element  402 . The second optical element  403  is rotatable with respect to the first optical element  402  around a geometric optical axis of the optical device. The geometric optical axis is parallel with the z-axis of the coordinate system  499 .  FIG.  4   c    shows an isometric view of the first optical element  402 , and  FIG.  4   d    shows an isometric view of the second optical element  403 . 
     The first and second optical elements  402  and  403  comprise sliding surfaces  409  and  410  for sliding with respect to each other and for mechanically supporting the first and second optical elements with respect to each other at least in radial directions perpendicular to the geometric optical axis. In this exemplifying optical device  401 , the sliding surface  409  of the first optical element  402  is on an outer rim of the first optical element and the second optical element comprises a rim section  412  surrounding the sliding surface  409  of the first optical element. 
     In the exemplifying optical device  401  illustrated in  FIGS.  4   a - 4   d   , the above-mentioned first surface  404  of the first optical element  402  comprises convex areas and concave areas between the convex areas. Correspondingly, the above-mentioned second surface  405  of the second optical element  403  comprises convex areas and concave areas between the convex areas. As shown in  FIG.  4   a   , the concave areas of the second surface  405  of the second optical element  403  compensate at least partly for an optical effect of the convex areas of the first surface  404  of the first optical element  402  and correspondingly the convex areas of the second surface  405  compensate at least partly for an optical effect of the concave areas of the first surface  404  when the second optical element  403  is in a first rotational position with respect to the first optical element  402  so that the concave areas of the second surface  405  are aligned with the convex areas of the first surface  404 . A combined optical effect of the first and second surfaces is changeable by rotating the second optical element  403  with respect to the first optical element  402  around the geometric optical axis of the optical device  401 .  FIG.  4   b    shows an exemplifying situation in which the second optical element  403  has been rotated so that the concave areas of the second surface of the second optical element  403  are not aligned with the convex areas of the first surface of the first optical element  402 . As illustrated in  FIG.  4   b   , the first and second surfaces spread the light arriving from the reflector surface  408 . 
     In an optical device according to an exemplifying and non-limiting embodiment, the first and second optical elements are shaped to form a limiter which limits an angle of rotation of the second optical element with respect to the first optical element. Extreme rotational positions of the second optical element with respect to the first optical element can be for example such that optical effects of the above-mentioned first and second surfaces compensate for each other as much as possible in one extreme rotational position, i.e. convex and concave areas are aligned with each other, whereas, in the other extreme rotational position, the first and second surfaces spread light as much as possible.  FIG.  5    illustrates a detail of an optical device according to this exemplifying and non-limiting embodiment. The optical axis of the optical device is parallel with the z-axis of a coordinate system  599 .  FIG.  5    shows partial section views of first and second optical elements  502  and  503 . In other respects, the first and second optical elements  502  and  503  can be for example like the first and second optical elements  302  and  303  illustrated in  FIGS.  3   a   - 3   d.    
     In an optical device according to an exemplifying and non-limiting embodiment, one of the first and second optical elements comprises one or more grooves whose depth directions are radial and longitudinal directions are circumferential with respect to rotation between the first and second optical elements, and the other one of the first and second optical elements comprises one or more radially directed projections in the one or more grooves. The one or more grooves and the one or more projections are suitable for shape locking the first and second optical elements together in a direction parallel with the geometric optical axis. Installation of the second optical element on the first optical element can be based on flexibility of the transparent material of the first optical element and/or on flexibility of the transparent material of the second optical element.  FIG.  6    illustrates a detail of an optical device according to this exemplifying and non-limiting embodiment.  FIG.  6    shows partial section views of first and second optical elements  602  and  603 . In other respects, the first and second optical elements  602  and  603  can be like the first and second optical elements  302  and  303  illustrated in  FIGS.  3   a   - 3   d.    
       FIG.  7   a    illustrates light distribution patterns produced by an illumination device according to an exemplifying and non-limiting embodiment. A section view of the illumination device is shown in  FIG.  7   b   . The geometric section plane is parallel with the xz-plane of a coordinate system  799 . The illumination device comprises a light source  711  and an optical device  701  according to an exemplifying and non-limiting embodiment. The optical device  701  comprises a first optical element  702  and a second optical element  703 . The first optical element  702  comprises a first surface for modifying a distribution of light exiting the first optical element  702  through the first surface, and the second optical element  703  comprises a second surface facing towards the first surface and for further modifying the distribution of the light that has exited the first optical element  702 . The first and second surfaces comprise convex areas and concave areas. The first surface of the first optical element  702  can be for example such as shown in  FIG.  3   c   , and the second surface of the second optical element  703  can be for example such as shown in  FIG.  3   d   .  FIG.  7   b    shows an exemplifying situation where the concave areas of the second surface of the second optical element  703  are aligned with the convex areas of the first surface of the first optical element  702 . An optical effect of the optical device  701  is changeable by rotating the second optical element  703  with respect to the first optical element  702  around a geometric optical axis of the optical device  701 . The geometric optical axis is parallel with the z-axis of the coordinate system  799 . In  FIG.  7   b   , the geometric optical axis is depicted with a dash-and-dot line. 
     Each of curves  751 ,  752 , and  753  shown in  FIG.  7   a    represents normalized luminous intensity as a function of an angle α between a viewing direction and the geometric optical axis of the optical device  701 . The angle α is shown in  FIG.  7   b   . The normalized luminous intensity depicted with the curve  751  corresponds to the exemplifying situation shown in  FIG.  7   b    where the concave areas of the second surface of the second optical element  703  are aligned with the convex areas of the first surface of the first optical element  702 . The normalized luminous intensity depicted with the curve  752  corresponds to an exemplifying situation in which the second optical element  703  has been rotated by an angle of 5 degrees around the geometric optical axis from the position shown in  FIG.  7   b   . The normalized luminous intensity depicted with the curve  753  corresponds to an exemplifying situation in which the second optical element  703  has been rotated by an angle of 10 degrees around the geometric optical axis from the position shown in  FIG.  7     b.    
     The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.