Patent Publication Number: US-10330902-B1

Title: Illumination optics and devices

Description:
CROSS REFERENCE TO PRIOR APPLICATION 
     The present case claims the benefits of U.S. patent application No. 62/521,139 filed 16 Jun. 2017, the entire content of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The technical field relates generally to illumination optics and devices for use with light sources. 
     BACKGROUND 
     Illumination arrangements including a light source and a corresponding lens have been used in many applications to generate light projections. In general, it is desirable that the size of an illumination device, more particularly the overall length with reference to the central optical axis along which light propagate, be kept as small as possible for the intended use. This can be required in view of different constraints, such as space restrictions, weight limitations and manufacturing cost targets, to name just a few, depending on the application and the implementation. One approach to improve compactness includes using a reflector inside the illumination device, thereby allowing the light source to be positioned closer to the light output. While the term “reflector” often refers to an optical component having mirror-like coated surfaces to reflect incident light (i.e. having specular reflection), it also designates an optical component, for instance a lens, in which total internal reflection (TIR) can occur without the need of any mirror-like coated surfaces. Light can reflect back on a TIR surface inside a lens with almost a 100% efficiency when the angle of incidence of the light rays is above a critical angle and when some other conditions are met. 
     Some lenses can be used in illumination devices and arrangements to simultaneously collimate light coming from a light source at the lens entry and reflect this light towards the lens exit. Using TIR inside these illumination optics is generally preferred whenever possible because specular reflection is not as efficient as TIR. Most applications will thus have illumination optics relying on TIR without having any significant specular reflection therein or with only specular reflection being used therein in limited areas. Nevertheless, some implementations can use illumination optics relying only on specular reflection. 
     For the sake of simplicity, lenses used as collimator/reflectors in illumination devices and applications will now be referred to as collimator lenses from this point onwards. 
     Light coming from a light source with which an illumination device is optically coupled enters the collimator lens of the device but some of this light can be lost if the acceptance angle of the light is not optimum everywhere at the light entry surfaces. Improving the capture of this light is highly desirable since it can increase the overall light output efficiency and/or uniformity. In order words, energy savings can be made with a more efficient light collection at the entry of the collimator lens since more light can be outputted for the same input and the energy provided to generate light at the light source can then be reduced. Furthermore, there are implementations where the goal is to have a maximum amount of light so optimizing the efficiency of the collimator lens is also very desirable in such situation. 
     Various other challenges and limitations also exist in the related technical field. Among other things, some applications may require illumination optics capable of accommodating sensors, cameras or other features in the immediate vicinity of the front side of a collimator lens. This may be very difficult to achieve using a collimator lens having a circular perimeter. 
     Mass-producing collimator lenses with a very high surface accuracy and a stable batch-to-batch consistency while minimizing costs can often be difficult using known methods and designs, particularly when they involve injection molding of a plastic resin material because the injection molding process itself may cause deformations of the optical active surfaces. Plastic lenses tend to shrink during cooling and this phenomenon can create issues when certain portions of the lenses cool at a different rate compared to others. The presence of thicker portions in lenses often tend to be detrimental to the surface accuracy and performances. In general, it is thus desirable to design lenses where all portions can be cooled relatively at the same rate when it solidifies at the end of the injection molding manufacturing process. Furthermore, minimizing the amount of plastic resin material required for making each lens is also desirable to reduce manufacturing costs and the weight of the final products. 
     Still, there are several applications where the projected light to be changed somehow, for instance in size, shape, orientation, or a combination thereof, while the illumination devices are in use. Examples includes, among other things, headlights of vehicles, flashlights, stage lighting for concerts or other events, light art shows and exhibits, to name just a few. Many others exist as well. These devices include, for instance, illumination optics movable along the central optical axis or having a light source that is movable along the central optical axis. Moving parts along the central optical axis changes the focal distance between the light source and the optics inside the illumination device, thereby creating a zooming effect that can change the size of the light projection from narrow or wide, or vice-versa. This approach may be suitable in many applications but may be unsatisfactory or inadequate in others, particularly when the available space is very limited, such as in automotive applications. It may also create additional complexities. Furthermore, the light collection efficiency and the shape can be very difficult to control over the entire range of positions. 
     Overall, room for many improvements always exists in this area of technology. 
     SUMMARY 
     In one aspect, there is provided a collimator lens for conveying light rays coming from a light source and that are generally propagating along a central optical axis so as to form a light projection, the collimator lens having a solid monolithic structure and made of a transparent material having a first refractive index, the collimator lens having a rear side and a front side, the collimator lens including: a central core section; a plurality of spaced-apart and longitudinally-extending side lobed segments laterally disposed around the central core section, each lobed segment having a TIR inner peripheral surface extending from the rear side towards the front side of the collimator lens, and having a light exit surface generally facing the front side, the TIR inner peripheral surfaces being separated from one another by a medium having a second refractive index that is lower than the first refractive index; and a light entry cavity located inside the central core section, the light entry cavity being opened at the rear side of the collimator lens and having a plurality of longitudinally-extending and distinct convex side wall surfaces, one for each of the lobed segments, each side wall surface being configured and disposed to collimate a portion of the light rays onto a corresponding one of the TIR inner peripheral surfaces, from which the light rays are reflected inside the collimator lens towards a corresponding one of the light exit surfaces, each side wall surface having an edge extending along the rear side of the collimator lens. 
     In another aspect, there is provided an illumination device for conveying light rays coming from a light source and generally propagating along a central optical axis so as to form a variable light projection, the illumination device including: a collimator lens having a solid monolithic structure and made of a transparent material having a first refractive index, the collimator lens having a rear side and a front side, the collimator lens including: a central core section; a plurality of spaced-apart and longitudinally-extending side lobed segments laterally disposed around the central core section, each lobed segment having a TIR inner peripheral surface extending from the rear side towards the front side of the collimator lens, and having a light exit surface generally facing the front side, the TIR inner peripheral surfaces being separated from one another by a medium having a second refractive index that is lower than the first refractive index; and a light entry cavity located inside the central core section, the light entry cavity being opened at the rear side of the collimator lens and having at least one side wall surface configured and disposed to collimate a portion of the light rays onto a corresponding one of the TIR inner peripheral surfaces, from which the light rays are reflected inside the collimator lens towards a corresponding one of the light exit surfaces; a diffusion lens coaxially disposed with reference to the central optical axis, the diffusion lens being positioned next to the front side of the collimator lens to redirect light coming out of the light exit surfaces, the diffusion lens having a plurality of spaced-apart outlying optical regions disposed around the central optical axis, at least one for each light exit surface, to be selectively positioned in or out of alignment with a corresponding one of the light exit surfaces of the collimator lens depending on a relative angular position between the collimator lens and the diffusion lens; and means for changing the relative angular position between the collimator lens and the diffusion lens around the central optical axis. 
     The various aspects and advantages of the proposed concept will be apparent from the following detailed description and the appended figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a front isometric view of an example of an illumination optic incorporating the proposed concept. 
         FIG. 2  is a rear isometric view of the collimator lens in  FIG. 1 . 
         FIG. 3  is an enlarged view of the light entry cavity illustrated in  FIG. 2 . 
         FIG. 4  is a front view of the collimator lens in  FIG. 1 . 
         FIG. 5  is a rear view of the collimator lens in  FIG. 1 . 
         FIG. 6  is a side view of the collimator lens in  FIG. 1 . 
         FIG. 7  is a cross section view taken along lone  7 - 7  in  FIG. 6 . 
         FIG. 8  is a semi-schematic cross section view similar to  FIG. 7  but where a generic example of a light source is also shown. 
         FIG. 9  is a semi-schematic isometric view depicting light exiting through the front side of the collimator lens in  FIG. 8 . 
         FIG. 10  is a side view of what is shown in  FIG. 9 . 
         FIG. 11  is a rear isometric view of an example of an illumination device incorporating the proposed concept. 
         FIG. 12  is a front view of the illumination device in  FIG. 11 . 
         FIG. 13  is a rear isometric view of the illumination device in  FIG. 11  but where the collimator lens and the diffusion lens are at a different angular position relative to one another. 
         FIG. 14  is a front view of the illumination device as illustrated in  FIG. 13 . 
         FIG. 15  depicts an example of a light projection on a target surface receiving light exiting through the front side of the diffusion lens in  FIGS. 11 and 12 . 
         FIG. 16  depicts an example of the light projection on the target surface receiving light exiting through the front side of the diffusion lens when positioned as illustrated in  FIGS. 13 and 14 . 
         FIGS. 17 to 19  depict a few generic examples of micro-optical elements for use on a diffusion lens or on the collimator lens. 
         FIG. 20  is a semi-schematic view depicting a generic example of a housing for the illumination device. 
         FIG. 21  is a rear isometric view illustrating another example of an illumination device incorporating the proposed concept. 
         FIG. 22  is a front isometric view of a working example of an illumination device incorporating the proposed concept. 
         FIG. 23  depicts an example of a light projection on a target surface receiving light from the illumination device in  FIG. 22  when set at a spot (narrow) beam position. 
         FIG. 24  is a view similar to  FIG. 23  but depicts, for the sake of comparison, an example of the light projection where the illumination device in  FIG. 22  is set at a flood (wide) beam position. 
         FIG. 25  is an example of a graph of the light output with reference to the horizontal angle for the illumination device in  FIG. 22 . 
         FIG. 26  is a front view depicting an example of a diffusion lens having a variable machined texture with a smooth gradient transition over the range of angular positions. 
         FIG. 27  is an enlarged view depicting an example of micro-optical elements at the center of the diffusion lens in  FIG. 26 . 
         FIGS. 28 and 29  are schematic views depicting the general outline of a light projection having a variable size depending on the relative angular position between the collimator lens and the diffusion lens. 
         FIGS. 30 and 31  are schematic views depicting the general outline of a light projection having a variable orientation depending on the relative angular position between the collimator lens and the diffusion lens. 
         FIGS. 32 and 33  are schematic views depicting the general outline of a light projection having a variable shape and size depending on the relative angular position between the collimator lens and the diffusion lens. 
         FIGS. 34 and 35  are enlarged rear isometric views depicting other examples of light entry cavities for the collimator lens in the illumination device. 
         FIGS. 36 and 37  are rear isometric views depicting other examples of collimator lenses for use in the illumination device. 
         FIGS. 38 to 45  are front isometric views depicting other examples of collimator lenses for use in the illumination device. 
         FIGS. 46 and 47  are front views depicting other examples of diffusion lenses for use in the illumination device. 
         FIGS. 48 and 49  are views similar to  FIGS. 4 and 5 , respectively, and depicting an implementation where the light exit surfaces or the TIR inner peripheral surfaces include micro-optic elements. 
         FIGS. 50 to 53  depict an illumination arrangement using a collimator lens and an array of four spaced-apart lenses, each lens having a corresponding light source. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a front isometric view of an example of an illumination optic incorporating the proposed concept. This illumination optic is referred to as a collimator lens  120 . 
     The collimator lens  120  is provided for conveying light rays coming from at least one light source  102  ( FIG. 8 ) and that generally propagate along a central optical axis  104  so as to form a light projection  106 , such as the ones shown in  FIGS. 15 and 16 . The collimator lens  120  has a rear side  130  and a front side  132 . In use, light outputs the collimator lens  120  at its front side  132 . 
     The collimator lens  120  has a solid monolithic structure and is made of a transparent material, such as a solidified moldable plastic resin material. Examples of materials include acrylic glass, polymethyl methacrylate, polycarbonate, silicon, cyclic olefin copolymer, and combination thereof. These materials general have an index of refraction between 1.42 and 1.65. Using a material having an index of refraction outside this range is also possible. Still, using other materials or even materials that are not plastics, including materials such as glass or others, is possible as well. 
     The collimator lens  120  includes a central core section  122  and a plurality of spaced-apart and longitudinally-extending side lobed segments  124 . These lobed segments  124  are laterally disposed around the central core section  122 . The example of  FIG. 1  shows that the lobed segments  124  of the collimator lens  120  are axisymmetric with reference to the central optical axis  104 . However, other configurations are possible, including some where the lobed segments  124  do not have an axisymmetric configuration. The illustrated example also has four lobed segments  124  and a cruciform layout. Using a different number of lobed segments  124  is possible as well. For instance, some implementations can include between three and eight while others could even have more than eight. Other variants are possible as well. 
     Each lobed segment  124  has a total internal refection (TIR) inner peripheral surface  126  extending between the rear side  130  and the front side  132  of the collimator lens  120 . Some implementations can also use specular reflection instead of TIR but in general, TIR is preferred because it can reflect light with a 100% efficiency. 
     In the illustrated example, each TIR inner peripheral surface  126  extends uninterruptedly between the rear side  130  and the front side  132  of the collimator lens  120 . Each TIR inner peripheral surface  126  also has a curved shape and, in the context of TIR, it is a concave surface for the refracted light impinging thereon. The curvature can be parabolic or circular in cross section. When the surfaces  126  are circular in shape, they can be concentric with the central optical axis  104 . Other variants are also possible. 
     Each lobed segment  124  also has a light exit surface  140  located adjacent to the front side  132 . In the illustrated example, the light exit surfaces  140  are planar and they extends perpendicular to the central optical axis  104 . Variants are possible as well, as shown for instance in other figures. Still, each light exit surface  140  on the example of  FIG. 1  is located on a projecting tip part  142  of the corresponding lobed segment  124 . These projecting tip parts  142  extend beyond the central core section  122 . They are separated from one another by intervening slots  144  extending radially from the central optical axis  104 . These slots  144  can be configured and shaped differently in other implementations, or even be omitted entirely. They may useful for various reasons, such as to decrease the quantity of material, to save weight in the end product, to optimize cooling during the injection molding manufacturing process, or to provide space for other features, to name just a few. Other variants are possible. 
     As can be appreciated, the open exterior spaces  128  between the lobed segments  124  create multiple outer surfaces and since these surfaces are not the TIR inner peripheral surfaces  126 , they can be used as mounting surfaces or for other purposes. The outer side of the TIR inner peripheral surfaces  126  must be surrounded by a medium, for instance ambient air. Using another medium is also possible as long as its refractive index, like air, is lower than that of the material forming the collimator lens  120 . This allows the TIR to occur inside the lens. The TIR inner peripheral surfaces  126  are also separated from one another of the side by the medium filling the open exterior space  128  between the lateral walls of each lobed segment  124 . The TIR inner peripheral surfaces  126  are thus disconnected from one another, unlike for instance circular lenses devoid of lobed segments. 
     The collimator lens  120  further includes a light entry cavity  150  located inside the central core section  122 , as best shown in  FIGS. 2 and 3 .  FIG. 2  is a rear isometric view of the collimator lens in  FIG. 1 .  FIG. 3  is an enlarged view of the light entry cavity illustrated in  FIG. 2 . 
     The light entry cavity  150  is opened at the rear side  130  of the collimator lens  120 . It also has a plurality of longitudinally-extending and distinct convex side wall surfaces  152 . There is one side wall surface  152  for each one of the lobed segments  124 . Thus, in the illustrated example, there are four of these side wall surfaces  152  and the light entry cavity  150  is concentric with the central optical axis  104 . Each side wall surface  152  also has an edge  152   a  ( FIG. 3 ) extending along the rear side  130  of the collimator lens  120 . The side wall surfaces  152  are, in this implementation, distinct from one another since they have delimitations between them. Variants of this configuration are possible. 
     The light entry cavity  150  of the illustrated example also includes an end wall surface  154 . This end wall surface  154 , however, may be omitted in some implementations or may be configured differently compared to what is shown. 
       FIGS. 4 to 7  are additional views of the collimator lens  120  shown in  FIG. 1 .  FIG. 4  is a front view thereof,  FIG. 5  is a rear view thereof and  FIG. 6  is a side view thereof.  FIG. 7  is a cross section view taken along lone  7 - 7  in  FIG. 6 . 
       FIG. 8  is a semi-schematic cross section view similar to  FIG. 7  but where a generic example of a light source  102  is also shown. This light source  102  can be, for instance, a solid state light, such as a LED producing light in the visible spectrum. Other kinds of solid state lights can be used as well. Using non-solid state light sources is also possible and, in some implementations, the light source could also output light outside of the visible spectrum. Still, one can use two of more light sources instead of just one with the same collimator lens  120 . Expressions such as “a light source”, “the light source” or the like, even when used in a singular form, do not exclude this possibility. 
     Still, in  FIG. 8 , only two examples of light rays are depicted for the sake of explanation. As can be appreciated, each side wall surface  152  of the light entry cavity  150  is configured and disposed to collimate a portion of the light rays, coming from the light source  102 , onto a corresponding one of the TIR inner peripheral surfaces  126 . These light rays will then be reflected inside the collimator lens  120  towards a corresponding one of the light exit surfaces  140 .  FIG. 8  shows that some of the light rays pass through the end wall surface  154  and exit through a central light exit surface  160  located at a front end of the central core section  122 . This central light exit surface  160  is located at the bottom of a central front cavity  162 . This central front cavity  162  is circular in shape in the illustrated example but variants are possible. It may even be omitted in some implementations. 
       FIG. 9  is a semi-schematic isometric view depicting light exiting through the front side  132  of the collimator lens  120  in  FIG. 8 .  FIG. 10  is a side view of what is shown in  FIG. 9 . 
       FIG. 11  is a rear isometric view of an example of an illumination device  100  incorporating the proposed concept.  FIG. 12  is a front view of the illumination device  100  in  FIG. 11 . As can be seen, this illumination device  100  includes the collimator lens  120  and a diffusion lens  200 . The collimator lens  120  can be, for instance, identical to the one illustrated in  FIG. 1  but variants are also possible as well. 
     The center of the diffusion lens  200  is coaxial with the central optical axis  104 . This diffusion lens  200  is also positioned next to the front side  132  of the collimator lens  120  to redirect light coming out of the light exit surfaces  140 . In the illustrated example, the diffusion lens  200  is positioned at a fixed distance immediately next to the front side  132  of the collimator lens  120  and can only pivot around the central optical axis  104 . Variants are possible as well. 
     In use, the diffusion lens  200  can pivot around the central optical axis  104 , thereby changing the relative angular position between the collimator lens  120  and the diffusion lens  200 . Depending on the implementation, this can also be achieved by mounting the collimator lens  120  on a pivoting arrangement while the diffusion lens  200  remains stationary. Some implementations could even include an arrangement where the collimator lens  120  and the diffusion lens  200  are both pivotable. Other variants are possible as well. 
     The diffusion lens  200  of the illustrated example is in the form of a planar disk-shaped element that extends radially with reference to the central optical axis  104 . Variants are possible. For instance, the periphery of the diffusion lens  200  could be noncircular in some implementations. The diffusion lens  200  could also be nonplanar, for instance being conical in shape or having another kind of tridimensional shape. Other variants are also possible. 
     The diffusion lens  200  of the illustrated example includes a main body  204  made of a transparent material and that is used as a substrate for supporting a plurality of outlying optical regions  210  disposed around the central optical axis  104 . There is at least one region  210  for each light exit surface  140  and since there are four light exit surfaces  140 , there are four regions  210 . Each of them can be selectively positioned in or out of alignment with the light exit surfaces  140  of the collimator lens  120 , depending on the relative angular position between the collimator lens  120  and the diffusion lens  200 .  FIGS. 11 and 12  illustrate a first position where the outlying optical regions  210  are almost entirely out of registry with corresponding light exit surfaces  140 . A second position is illustrated in  FIGS. 13 and 14 .  FIG. 13  is a rear isometric view of the illumination device  100  in  FIG. 11  but where the collimator lens  120  and the diffusion lens  200  are at a different angular position relative to one another.  FIG. 14  is a front view of the illumination device  100  as illustrated in  FIG. 13 . 
     The four outlying optical regions  210  in the illustrated example are somewhat rectangular in shape and they include micro-optical elements  220 . These regions  210  are spaced-apart from one another, meaning that most of their lateral sides are spaced-apart from adjacent outlying optical regions  210 . They are shown as being completely detached from one another but in some implementations, they can, for instance, be in contact to one another at the center of the diffusion lens  200 , or be all connected at a central area. The regions  210  are said to be optical, meaning that they are refracting light and not simply blocking the light. 
     In the illustrated example, the intervening spaces between adjacent regions  210  are simply transparent portions of the main body  204 . The diffusion lens  200  of the illustrated example also includes a distinct central region  214 . This central region  214  is positioned right above the central core section  122  and receives light therefrom. This central region  214  can be integrated with the other regions  210 . Some implementations may have no or very little light coming out of the central core section  122  and as a result, the central region  214  can be omitted or even be non-optical, for instance be an opaque surface. Other variants are possible as well. 
     In use, most of the light coming out the collimator lens  120  will pass through the diffusion lens  200  and the light refraction will depend on where the regions  210  are located, thus on the relative angular position between them.  FIGS. 11 and 12  show a first position where most of the light coming from the light exit surfaces  140  of the collimator lens  120  will pass through the transparent portions on the main body  204 . In  FIGS. 13 and 14 , most of the light coming from the light exit surfaces  140  of the collimator lens  120  will pass through the regions  210 . The small proportion of the light rays coming out of the central core section  122  of the collimator lens  120  will mostly go through the central region  214 , regardless of the relative angular position. 
       FIG. 15  depicts an example of a light projection on a target surface receiving light exiting through the front side of the diffusion lens  200  in  FIGS. 11 and 12 .  FIG. 16  depicts an example of the light projection on the target surface receiving light exiting through the front side of the diffusion lens  200  when positioned as illustrated in  FIGS. 13 and 14 . As can be seen, there is a variation of the size and of the overall shape of the light projection between the first position and the second position. This variation is incremental since the relative angular position can be also be set anywhere between the first and the second position. This creates a zooming effect or a variable focus effect without axially displacing one of the illumination optics or the light source. Such results would not be possible using a conventional circular lens. 
     It should be noted that the light projection examples depicted in  FIGS. 15 and 16  are only for the sake of explanation. The actual light projections, including the way they vary depending on the relative angular position, can be different from what is depicted. 
       FIGS. 17 to 19  depict a few generic examples of micro-optical elements  220  for use on a diffusion lens, such as the one shown in  FIGS. 11 to 14 , or on the collimator lens  120 . These micro-optical elements  220  are generally very small and may even not be seen with a naked eye. They can be convex or concave with reference to the light passing through them, depending on the needs and other factors. These micro-optical elements  220  provide a diffusing effect on the light rays when the light rays are received from the collimator lens  120 . 
     The micro-optical elements  220  can be, for instance, in the form of lenslets, micro-lenses, micro-prisms, micro-cylinders and/or textured surfaces, to name just a few.  FIG. 17  depicts an example of an array of micro-optical elements  220  that are in the form of micro-prisms.  FIG. 18  depicts an example of an array of micro-optical elements  220  that are in the form of micro-lenses.  FIG. 19  depicts an example of micro-optical elements  200  of different sizes that were machined to form a hexagonal pattern. Other kinds of micro-optical elements  220  are possible as well. 
       FIG. 20  is a semi-schematic view depicting a generic example of a housing  300  for the illumination device  100 . This illumination device  100  can be, for instance, a light bulb for a general lighting application. Many other implementations are possible as well. In  FIG. 20 , the illumination device  100  includes a collimator lens  120  that is stationary, a light source  102  positioned adjacent to the rear side  130  of the collimator lens  120 , and a diffusion lens  200  provided in front of the collimator lens  120 . In this example, the collimator lens  120  is mounted on a pivotable ring  310  attached to the housing  300  and that can be manually pivoted by a user to change the angular position of the diffusion lens  200 . The upper side of the housing  300  can be closed by a protective lens or be left open, depending on the implementation. 
       FIG. 21  is a rear isometric view illustrating another example of an illumination device  100  incorporating the proposed concept. This example includes a diffusion lens  200  having a plurality of sector-shaped outlying optical regions  210 ,  212  covering the entire surface. These regions  210 ,  212  have an axisymmetric configuration but other configurations are possible as well. For instance, if the lobed segments  124  are not axisymmetric with reference to the central optical axis  104 , the outlying optical regions  210 ,  212  could be arranged differently compared to what is shown. The number of first regions  210  and the number of second regions  212  each match the number of lobed segments  124 . These regions  210 ,  212  can also be subdivided themselves. 
       FIG. 22  is a front isometric view of a working example of an illumination device  100  incorporating the proposed concept. This example includes a housing  300  over which a mounting plate assembly  302  is bolted to pivotally mount the diffusion lens  200  in front of a collimator lens located inside the housing  300 . The mounting plate assembly  302  has a central opening allowing light from the diffusion lens  200  to exit. The diffusion lens  200  can be pivoted over a range of about 45 degrees using one of the two oppositely-disposed side tabs  304  in this example. The side tabs  304  can be moved within a corresponding arc-shaped slot  306 . Variants are possible as well. 
     It should be noted that if desired, one can design the illumination device  100  with a motorized mechanism to change the relative angular position of the diffusion lens  200  with reference to the collimator lens  120 , or vice-versa. This motorized mechanism can be manually or automatically controlled, or even be both manually and automatically controlled. Automatic control can involve using signals from sensors or from other devices to determine the relative angular position of the illumination optics inside the illumination device  100 . Other variants are possible as well. 
     Furthermore, while the main goal of an arrangement such as the mounting plate assembly  302  is to change the relative angular position between the collimator lens  120  and the diffusion lens  200 , some implementations may include an arrangement where the diffusion lens  200  could also be movable along the central optical axis  104  in addition to the possibility of changing the relative angular position. The two motions can be independent from one another, or be simultaneous, for instance be helical or the like. The light source  102  may also be movable as well. Other variants are possible. 
       FIG. 23  depicts an example of a light projection on a target surface receiving light from the illumination device  100  in  FIG. 22  when set at a spot (narrow) beam position.  FIG. 24  is a view similar to  FIG. 23  but depicts, for the sake of comparison, an example of the light projection where the illumination device in  FIG. 22  is set at a flood (wide) beam position. 
       FIG. 25  is an example of a graph of the light output (in candelas) with reference to the horizontal angle for the illumination device  100  in  FIG. 22 . At the center position in the graph (0 degree), the line at the top corresponds to what is shown in  FIG. 23 , namely to the spot (narrow) beam position, and the line at the bottom corresponds to what is shown in  FIG. 24 , namely to the flood (wide) beam position. The measurements follow the stippled reference lines shown in  FIGS. 23 and 24 . 
       FIG. 26  is a front view depicting an example of a diffusion lens  200  having a variable machined texture with a smooth gradient transition over the range of angles. This texture is formed by micro-optical elements, for instance micro-optical elements. They may even have a specular finish to minimize losses. The micro-optical elements are about 100 microns in scale on the illustrated example but other dimensions are possible as well. They were molded on a thermoplastic material, such as polymethyl methacrylate or polycarbonate. Other materials are possible as well. In  FIG. 26 , the darker areas (such as the one marked by stippled line  230 ) correspond to the narrow beam position and the lighter ones (such as the one marked by stippled line  232 ) correspond to the wide beam position. 
       FIG. 27  is an enlarged view depicting an example of micro-optical elements at the center of the diffusion lens  200  in  FIG. 26 . 
       FIGS. 28 and 29  are schematic views depicting the general outline of a light projection having a variable size depending on the relative angular position between the collimator lens  120  and the diffusion lens  200 .  FIG. 28  depicts a spot (narrow) beam position, as shown for instance in  FIGS. 15 and 23 .  FIG. 28  depicts a flood (wide) beam position, as shown for instance in  FIGS. 16 and 24 . The stippled lines represents the area where most of the light rays are concentrated. 
       FIGS. 30 and 31  are schematic views depicting the general outline of a light projection having a variable orientation depending on the relative angular position between the collimator lens  120  and the diffusion lens  200 . They illustrate that changing the relative angular position between the collimator lens  120  and the diffusion lens  200  is not limited to changing the size of the light projection. One can design the diffusion lens  200  to change the orientation of a noncircular light projection, as shown for instance in  FIGS. 32 and 33 .  FIGS. 32 and 33  are schematic views depicting the general outline of a light projection having both a variable shape and size depending on the relative angular position between the collimator lens  120  and the diffusion lens  200 . Still, other possibilities exist as well. 
       FIGS. 34 and 35  are enlarged rear isometric views depicting other examples of light entry cavities  150  for the collimator lens  120  to be used in the illumination device  100 . In  FIG. 34 , the side wall surfaces  152  are planar, thus not convex or otherwise curved. In  FIG. 35 , the light entry cavity  150  includes a single side wall surface  152  that is circular. Other variants for the light entry cavity  150  are possible as well. 
       FIGS. 36 and 37  are rear isometric views depicting other examples of collimator lenses  120  for use in the illumination device  100 .  FIG. 36  has three lobed segments  124  and in  FIG. 37 , the four lobed segments  124  have lateral outer wall surfaces meeting at right angles adjacent to the central core section  122 . 
       FIGS. 38 to 45  are front isometric views depicting other examples of collimator lenses  120  for use in the illumination device  100 . Among other things,  FIG. 43  shows an implementation where the collimator lens  120  has one lobed segment  124  shorter than the others.  FIG. 44  shows a collimator lens  120  with eight lobed segments  124 . 
       FIGS. 46 and 47  are front views depicting other examples of diffusion lenses  200  for use in the illumination device  100 . 
     It should be noted that the few examples depicted in  FIGS. 34 to 47  are not an exhaustive list of variants and that other variants can be devised as well. 
       FIGS. 48 and 49  are views similar to  FIGS. 4 and 5 , respectively, and depicting an implementation where the light exit surfaces  140  or the TIR inner peripheral surfaces  126  include micro-optic elements  220 . The micro-optic elements  220  are only partially shown and are not to scale. What is shown in  FIGS. 48 and 49  is only for the sake of explanation. The micro-optic elements  220  can cover different areas of the surfaces  126 ,  140 . They need not necessarily to be identical everywhere or be symmetric. One can also design a collimator lens  120  where micro-optic elements  220  are present at least partially on both the light exit surfaces  140  and on the TIR inner peripheral surfaces  126 . 
       FIGS. 50 to 53  depict an illumination arrangement  400  using a collimator lens  200  and an array of four spaced-apart lenses  410 , each lens  410  having a corresponding light source  420  ( FIG. 53 ). These lenses  410  can have a simpler design compared to that of the collimator lens  210  and may even involve no internal reflection, either TIR or specular reflection. The collimator lens  200  can pivot around a central axis. This illumination arrangement  400  can be useful in certain applications. Variants of this design are possible as well, including some where the parts are not axisymmetric as shown. 
     The present detailed description and the appended figures are meant to be exemplary only, and a skilled person will recognize that variants can be made in light of a review of the present disclosure without departing from the proposed concept. Among other things, when terms such as perpendicular, parallel, radial or the like are used, these terms refer to an angle being substantially perpendicular, substantially parallel, substantially radial, etc. Thus, even without any adjective or adverbs, these terms do not necessarily require a high degree of precision and, unless otherwise indicated, they must be understood as including design variants or manufacturing tolerances that are, for instance, of ±20 degrees. They may also be, for instance, ±10 degrees in precision, or even ±5 degrees, depending on the specific context. These design variants or manufacturing tolerances would fall within the intended definitions. Likewise, when shape-related terms such as planar, flat, disk-shaped and the like, these terms refer to something that is substantially planar, substantially flat, substantially disk-shaped, etc. The same principle applies to many other terms and expressions through the entire specification. Words such as “substantially” and the like were generally omitted for the sake of legibility. 
     LIST OF REFERENCE NUMERALS 
     
         
           100  illumination device 
           102  light source 
           104  central optical axis 
           106  variable light projection 
           120  collimator lens 
           122  central core section 
           124  lobed segment 
           126  TIR inner peripheral surface 
           128  open exterior space 
           130  rear side 
           132  front side 
           140  light exit surface 
           142  projecting tip part 
           144  slot 
           150  light entry cavity 
           152  side wall surfaces 
           154  end wall surface 
           160  central light exit surface 
           162  central front cavity 
           200  diffusion lens 
           204  main body 
           210  first outlying optical region 
           212  second outlying optical region 
           214  central optical region 
           220  micro-optic elements 
           230  narrow beam position 
           232  wide beam position 
           300  housing 
           302  mounting plate assembly 
           304  side tab 
           306  arc-shaped slot 
           310  pivotable ring 
           400  illumination arrangement 
           410  lens 
           420  light source