Abstract:
A micro-optical bench may include a substrate having a substantially planar surface on which an optical element is to be mounted, and two lithographs protruding above the substantially planar surface adapted to position and restrain movement of the optical element.

Description:
FIELD OF THE INVENTION  
       [0001]    Embodiments are directed to micro-optical benches and methods of fabricating micro-optical benches. More particularly, embodiments are directed to passive alignment optical micro-benches for out-of-plane optics and methods of fabricating such a micro-optical bench. 
       BACKGROUND OF THE INVENTION  
       [0002]    Micro-optical benches, i.e., optical motherboards, may be used to precisely align optical fibers and/or other components, e.g., lenses, detectors, lasers, etc. More particularly, e.g., micro-optical benches may be used for passive alignment of out-of-plane optical components and/or alignment of optical fiber waveguides. Micro-optical benches are generally formed using dry etching and/or wet etching techniques. For example, a silicon optical bench (SiOB) may be formed by anisotropically wet-etching silicon substrates, with various crystal orientations, in accordance with a desired sidewall angle. 
         [0003]    The use of, e.g., silicon substrates and/or wet etching methods may, however, be limiting. For example, silicon substrates, which are opaque and do not transmit light, may not be useful in visible light applications. Also, e.g., wet etching methods, which progress along crystal planes of a substrate, generally only enable certain sidewall angles to be formed due to an orientation of the crystal planes with respect to a crystal growth axis thereof. Additionally, wet etching methods of silicon substrates may be limited to one or two different aspect ratios due to the relatively large topography of the remaining substrate. Therefore, the positional orientation of optical components on the SiOB may be limited by the crystallographic orientation of the substrate. 
         [0004]    In some cases, dry etching methods have been employed to form optical benches, e.g., anisotropically dry etching polycrystalline substrates to form optical benches. However, forming sidewalls, e.g., wells, for positioning of micro-optics on the substrate may involve deep etches, e.g., greater than about 50 μm, may be difficult using lithographic techniques. Further, due to the nature of dry-etching processes, surface quality at, e.g., a bottom surface of the well may be poor, e.g., rough. As a result of such roughness, an optical element to be positioned at least partially within the well may not be positioned properly, and thus, alignment of the optical element with respect to the substrate and/or other elements on the optical bench may not be proper. 
       SUMMARY OF THE INVENTION 
       [0005]    Embodiments are therefore directed to optical benches for out-of-plane optical component(s) and methods of forming optical benches for out-of-plane optical component(s), which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. More particularly, embodiments are therefore directed to micro-optical benches for out-of-plane optical element(s) and methods of forming micro-optical benches for out-of-plane optical element(s), which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. 
         [0006]    It is therefore a feature of an embodiment of the present invention to provide a micro-optical bench that is free of positional orientation restrictions. 
         [0007]    It is therefore a separate feature of an embodiment of the present invention to provide a method of forming a micro-optical bench that is free of positional orientation restrictions. 
         [0008]    It is therefore a separate feature of an embodiment of the present invention to provide a micro-optical bench including a transmissive substrate. 
         [0009]    It is therefore a separate feature of an embodiment of the present invention to provide a method of forming a micro-optical bench including a transmissive substrate. 
         [0010]    It is therefore a separate feature of an embodiment of the present invention to provide a method of forming a micro-optical bench without requiring etching of the substrate thereof. 
         [0011]    It is therefore a separate feature of an embodiment of the present invention to provide a micro-optical bench including positioning projections on a surface thereof for passively aligning optical components with the positioning projections. 
         [0012]    It is therefore a separate feature of an embodiment of the present invention to provide a method of forming a micro-optical bench including positioning projections on a surface thereof for passively aligning optical components with the positioning projections. 
         [0013]    At least one of the above and other features and advantages of the present invention may be realized by providing a micro-optical bench, including a substrate having a substantially planar surface on which an optical element is to be mounted, and two lithographs protruding above the substantially planar surface adapted to position and restrain movement of the optical element. 
         [0014]    The two lithographs may define a footprint for the optical element. 
         [0015]    When the optical element is on the substrate, each of the lithographs may abut the optical element. Each of the lithographs may abut opposing faces of the optical element. Each of the lithographs may abut adjacent faces of the optical element. 
         [0016]    The two lithographs may include a plurality of lithographs, each lithograph may abut a different face of the optical element adjacent the substrate. Two lithographs of the plurality of lithographs may abut each different face of the optical element adjacent the substrate. 
         [0017]    The two lithographs may allow the optical element to be positioned in at least two rotational positions. Each lithograph may be adjacent to one side of the optical element at each rotational position. The two lithographs may be made of a polymer or a polymerizing vitreous material. The two lithographs may be integral with the substrate. The substrate may be transparent to wavelengths of interest. 
         [0018]    The optical element may be optically connected through the substrate. The substrate may include a plurality of substantially planar surfaces on which corresponding optical elements are to be mounted, and the two lithographs may include two lithographs adjacent each of the corresponding optical elements. The plurality of substantially planar surfaces may form a continuous substantially planar surface. 
         [0019]    At least one of the lithographs may have one of a circular cross-sectional shape, an oval cross-sectional shape and a polygonal cross-sectional shape. An adhesive layer may be arranged between the substrate and the optical element. 
         [0020]    The micro-optical element may include a second substrate overlapping at least a portion of the substrate and spaced apart from the substrate by a predetermined distance corresponding to a height of bonding spacers arranged between the substrate and the second substrate, wherein the second substrate may include a substantially planar surface on which an optical element is to be mounted. 
         [0021]    The two lithographs may include a plurality of lithographs and at least one of the plurality of lithographs may project a further distance away from the substrate than others of the plurality of lithographs. 
         [0022]    At least one of the above and other features and advantages of the present invention may be separately realized by providing a method of manufacturing an optical bench, including cleaning a surface of a substrate, priming the cleaned surface of substrate for photopolymer application, coating the primed surface of the substrate with a photopolymer layer, exposing a portion of the photopolymer layer based on a position of at least two positioning projections to be formed on the substrate, the positioning projections being positioned so as to define a predetermined space on the optical bench where an optical element is to be mounted, curing and developing the photopolymer layer to form the at least two positioning projections, and thermally treating the at least two positioning projections. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which: 
           [0024]      FIG. 1A  illustrates a plan view of a first exemplary embodiment of an optical bench in a state in which an optical element is being positioned thereon; 
           [0025]      FIG. 1B  illustrates a top plan view of the first exemplary embodiment of the optical bench of  FIG. 1A  without an optical element positioned thereon; 
           [0026]      FIG. 1C  illustrates a plan view of the first exemplary embodiment of the optical bench of  FIG. 1A  in a state in which the optical element is positioned thereon; 
           [0027]      FIG. 2A  illustrates a cross-sectional view of a second exemplary embodiment of an optical bench in a state in which a plurality of optical elements are positioned thereon; 
           [0028]      FIG. 2B  illustrates a top plan view of the second exemplary embodiment of the optical bench of  FIG. 2A ; 
           [0029]      FIG. 3  illustrates a cross-sectional view of a third exemplary embodiment of an optical bench in a state in which a plurality of optical elements are positioned thereon; 
           [0030]      FIG. 4  illustrates a top plan view of an exemplary surface showing exemplary configurations of positioning projections; and 
           [0031]      FIG. 5  illustrates a flow chart of stages in an exemplary process of forming an optical bench. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. 
         [0033]    In the drawings, the thickness of layers and regions may be exaggerated for clarity. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it may be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it may be directly under, or one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or one or more intervening layers may also be present. Like numbers refer to like elements throughout the specification. 
         [0034]      FIG. 1A  illustrates a plan view of a first exemplary embodiment of an optical bench  10  in a state in which an optical element is being positioned thereon,  FIG. 1B  illustrates a top plan view of the first exemplary embodiment of the optical bench  10  of  FIG. 1A  without an optical element positioned thereon, and  FIG. 1C  illustrates a plan view of the first exemplary embodiment of the optical bench  10  of  FIG. 1A  in a state in which the optical element is positioned thereon. 
         [0035]    Referring to  FIG. 1A , the optical bench  10  may include a substrate  100  with a plurality of positioning projections  110  and optical element(s), e.g., a micro-prism  105 . An optical element may be, e.g., a lens, a detector, a mirror, a light source, an optical fiber, etc. The positioning projections  110  may serve to precisely position, e.g., passively align, the optical element(s) on the substrate  100  by providing, e.g., reference or boundary points for the precise alignment of the respective optical element to be positioned therewith. The micro-prism  105  may be restrained against movement about one or more of axes X, Y, and Z shown in  FIG. 1A . The positioning projections  110  may be an integral part of the substrate  100  or may be made of a different material therefrom. The optical element(s) may be optically connected through the substrate  100 . 
         [0036]    The substrate  100  may include, e.g., transmissive material(s), and may be transparent to at least certain wavelengths of interest, i.e., predetermined wavelengths. More particularly, e.g., in some embodiments of the invention, the substrate  100  may be or may include, e.g., glass, e.g., fused quartz, fused silica, optical glass, Pyrex. However, embodiments of the invention are not limited to substrates  100  that are transmissive. For example, in some embodiments of the invention the substrate  100  may include opaque material(s), e.g., may be a silicon wafer. That is, the substrate  100  may include any material(s) on which the positioning projections  110  may be arranged and which is capable of supporting the optical element(s) thereon. 
         [0037]    The substrate  100  may have a planar and/or substantially planar surface  101 , and the positioning projections  110  may be arranged on the planar and/or substantially planar surface  101 . Although a single planar and/or substantially planar surface  101  is shown in  FIGS. 1A through 1C , embodiments of the invention are not limited thereto. For example, the substrate  100  may include a plurality of planar and/or substantially planar surfaces and some or all of the plurality of planar or substantially planar surfaces of the substrate  100  may include a plurality of positioning projections and one or more optical elements arranged thereon. 
         [0038]    The positioning projections  110  may project from the planar and/or substantially planar surface  101  of the substrate  100 . In some embodiments, e.g., all of the positioning projections  110  may project a same distance relative to the planar or substantially planar surface  101  of the substrate  100 . In other embodiments, some or each of the positioning projections  110  may project a different distance from the planar or substantially planar surface  101  of the substrate  100 . A distance that each positioning projection  110  extends away from the substrate  100 , i.e., a height of the positioning projection  110  along the z-direction relative to the substrate  100 , may be based on, e.g., a size, height and/or weight of the optical element being arranged on the substrate  100  in relation thereto, a number of the positioning projections  110  associated with one of the optical elements and/or a position of the positioning projection  110 , i.e., characteristics of the respective portion of the optical element that the positioning projection  110  is to help position. That is, the positioning projections  110  may each be respectively sized to be at least thick enough, e.g., along the x-y plane, and tall enough, along the z-direction, to serve as a positioning structure for the respective optical element and/or to withstand any pressure that may be subjected thereon by the respective optical element. 
         [0039]    In some embodiments of the invention, one or some of the positioning members  110  may be arranged on other ones of the positioning members  110 . The positioning projections  110  may have various cross-sectional shapes along the x-y plane. For example, the positioning projections  110  may have a L-shaped, concave-shaped, convex-shaped, round, oval, polygonal, e.g., square, rectangular, triangular, octagonal, etc., cross-sectional shape along the x-y plane. 
         [0040]    Referring to  FIG. 1A , the positioning projections  110  may project, e.g., along a first direction, e.g., z-direction, relative to the planar and/or substantially planar surface  101 . As shown in  FIGS. 1A and 1C , the micro-prism  105  may be precisely arranged at a respective predetermined position on the planar and/or substantially planar surface  101  of the substrate  100  in accordance with the positioning projections  110  associated therewith. 
         [0041]    As shown in  FIG. 1B , the plurality of positioning projections  110  may define one or more predetermined spaces, i.e., footprints, on the substrate  100  where the micro-prism  105  may be arranged. More particularly, the plurality of positioning projections  110  may define a predetermined space  112  on the substrate  100  by, e.g., defining a boundary along a plane extending along second and third directions, i.e., x-y plane, within which the micro-prism  105  may be arranged, or by serving as edge stops for respective portions or edges of the micro-prism  105 . For example, in some embodiments of the invention, a shape of the boundary defined by the positioning projections  110  may substantially correspond to a cross-sectional shape of a portion, e.g., lower portion, of the micro-prism that is to be arranged between the projecting portions  110 . In other embodiments of the invention, when the optical element, e.g., the micro-prism  105 , is arranged relative to the corresponding projecting portions  110 , portions or sides of the micro-prism  105  may abut or be arranged adjacent to respective ones of the projecting portions  110  while other portion(s), e.g., corner(s), of the micro-prism  105  may extend outward beyond the projection portions  110 . The predetermined spaces  112  may be defined in accordance with the optical functionality requirements and the optical bench  10  design requirements. 
         [0042]    Referring to  FIG. 1B , in some embodiments of the invention, an adhesive  115  may be provided on the substrate  100  in the predetermined space  112 . The adhesive  115  may be employed to secure the micro-prism  105  to the substrate  100 . The adhesive  115  may be provided at a portion of or all of the predetermined space  112 . The adhesive  115  may be, e.g., a thermal or UV-curable epoxy. In such cases, e.g., after the micro-prism  105  is arranged on the predetermined space  112 , the respective portion of the optical bench  10  may be thermally treated or exposed to UV light to cure the adhesive and fix the micro-prism  105  over the respective predetermined space  112 . 
         [0043]    Although the first exemplary embodiment is illustrated with the micro-prism  105  having a specific shape, embodiments of the invention are not limited to a micro-prism and/or a micro-prism having the shape shown in  FIGS. 1A and 1C . 
         [0044]    Further, although eight positioning projections  110  are illustrated in the exemplary embodiment of  FIGS. 1A to 1C , embodiments of the invention are not limited to eight positioning projections  110 . More particularly, e.g., two or more positioning projections  110  may be provided for arranging a single optical element, e.g., micro-prism  105 . Also, in the first exemplary embodiment illustrated in  FIG. 1 , the positioning projections  110  are arranged so as to have two positioning projections  110  on each side of the micro-prism  105 . However, embodiments of the invention are not limited to such an arrangement. For example, in some embodiments, only two positioning projections  110  may be provided and a portion of a first side of an optical element may, e.g., abut one of the two positioning projections  110  and a second side of the optical element may, e.g., abut a second side of the optical element. In such cases, the first side of the optical element may be opposite to the second side of the optical element. 
         [0045]    Referring to  FIGS. 1A ,  1 B and  1 C, embodiments of the invention may provide the plurality of positioning projections  110  to align the micro-optical benches on the optical bench  10  without requiring any etching of the substrate  100 . Accordingly, transmissive substrates, e.g., substrates that are generally difficult or slow to etch, may be used and embodiments of the invention may be employed in visible light applications. Further, embodiments of the invention may not be subjected to any positional orientation restrictions, e.g., restrictions resulting from the crystallographic orientation of the substrate. 
         [0046]      FIG. 2A  illustrates a cross-sectional view of a second exemplary embodiment of an optical bench  20  in a state in which a plurality of optical elements are positioned thereon, and  FIG. 2B  illustrates a top plan view of the second exemplary embodiment of the optical bench  20   FIG. 2A . 
         [0047]    As shown in  FIGS. 2A and 2B , the second exemplary optical bench  20  may include a substrate  200 , a plurality of positioning projections  210 , and a plurality of optical elements, e.g., a prism  215 , a beamsplitting cube  225 , a ball lens  235  and a beamsplitting prism  245 . Referring to  FIG. 2A , the plurality of positioning projections  210  and the prism  215 , the beamsplitting cube  225 , the ball lens  235  and the beamsplitting prism  245  may be arranged on a planar and/or substantially planar surface of the substrate  200 . The prism  215  may be a reflector with a metallic coating  216 . 
         [0048]    The arrows shown in  FIGS. 2A and 2B  illustrate an exemplary path  250  of light through opposing sides of the substrate  200  and further through the optical elements, e.g., the prism  215 , the beamsplitting cube  225 , the ball lens  235  and the beamsplitting prism  245 . 
         [0049]    Like the substrate  100  of the first exemplary embodiment, in some embodiments of the invention, the substrate  200  may be or may include opaque and/or transmissive material(s). For example, the substrate  200  may include, e.g., glass, e.g., fused quartz, fused silica, optical glass, Pyrex. 
         [0050]    Referring to  FIGS. 2A and 2B , any number of the positioning projections  210  may be arranged on the substrate  200  for positioning each of the optical elements. The positioning projections  210  may be arranged so as to abut or receive any portion, e.g., side portion or corner portion, of the respective optical element. For example, three positioning projections  210  may be arranged on the substrate  200  to define a predetermined space thereon for the prism  215 . More particularly, e.g., two of the positioning projections  210  corresponding to the prism  215  may abut a respective side portion of the prism  215  and one of the positioning members  210  corresponding to the prism  215  may abut or receive a corner portion of the prism  215 . Two positioning projections, e.g., one at two opposing corners, may be arranged on the substrate  200  to define a predetermined space thereon for the beamsplitting cube  225 . 
         [0051]    Four positioning members  210  may be arranged on the substrate  200  to define a predetermined space for the ball lens  235 . More particularly, the optical bench  20  may include positioning projections  210  and second positioning projections  210   a.  The second positioning projections  210   a  may project from the positioning projections  210  arranged on the substrate  200 . In such cases, the positioning projections  210  corresponding to the ball lens  235  may serve as a stage-like or propping-type positioning projection so as to enable the ball lens  235  to be aligned along the path  250  of light. That is, in some embodiments, e.g., when optical elements of different overall sizes are employed, the positioning projections, e.g.,  210 ,  210   a,  may be stacked on each other or may project different distances from the substrate  200  to enable the respective optical element(s) to be aligned in accordance with the design standards of the optical bench  20 . 
         [0052]    Referring again to  FIGS. 2A and 2B , four positioning projections  210  may be arranged on the substrate  200  to define a respective predetermined space for the beamsplitting prism  245 . For example, one of the positioning projections  210  may be arranged to abut each side of the beamsplitting prism  245 . 
         [0053]    In embodiments of the invention, as discussed above, the arrangement, shape, size, height, etc., of each of the positioning projections  210  may depend on the design requirements of the optical bench, the shape of the respective optical element(s), the size of the respective optical element(s), etc. For example, a height H 1  of at least one of the positioning projections  110  associated with the prism  215  may be based on a height H 2  of the prism  215 . The height H 1  of at least one of the positioning projections  110  associated with the prism  215  may be an order of magnitude shorter than the height H 2  of the prism  215 . More particularly, e.g., referring to  FIG. 2A , if the height H 2  of the prism  215  is about 0.3 mm to about 3.0 mm, the height H 1  of at least one of or all of the corresponding positioning projections  110  may be about 50 μm to about 500 μm. 
         [0054]      FIG. 3  illustrates a cross-sectional view of a third exemplary embodiment of an optical bench  30  in a state in which a plurality of optical elements are positioned thereon. More particularly, the optical bench  30  may be a multi-layered optical bench including the second exemplary optical bench  20  described above as one layer thereof and a second optical bench  25  as a layer stacked on the optical bench  20 . 
         [0055]    The second optical bench  25  may include a substrate  300  with a plurality of positioning projections  310 , and a plurality of optical elements, e.g., a beamsplitting cube  315  and a prism  325 , arranged on, e.g., a substantially planar or planar surface  300  thereof. The prism may be coated with a reflectively, e.g., metallic, layer  326 . A diffractive optical element  270  may be etched in the substrate  300 . In cases in which the substrate  300  is a transmissive substrate, light may be transmitted from the optical bench  20  up toward the optical elements  315 ,  325  on the second optical bench  30 . 
         [0056]    As shown in  FIG. 3 , bonding spacers  260  may be arranged between the optical bench  20  and the second optical bench  25 . A height of the bonding spacers  260  may be taller than a height of the tallest one of the optical elements on the optical bench  20  relative to the substrate  200  thereof. The bonding spacers  260  may be, e.g., polymer spacers. Positions of the bonding spacers on the substrate  200  and/or a number of spacers  260  may be based on mechanical design requirements of the optical bench  30 . For example, pre-existing planar refractive or diffractive components in the substrate(s)  200 ,  300  may be considered when placing the positioning projections  210 ,  310 . Although only two layers are shown in  FIG. 3 , micro-optical benches according to one or more aspects of the invention may have more than two layers, i.e., more than two stacked substrates. 
         [0057]      FIG. 4  illustrates a top plan view of an exemplary surface showing exemplary arrangement patterns of positioning projections  410 ,  410 ′,  420 . 
         [0058]    More particularly,  FIG. 4  illustrates first and second optical elements  415 ,  425  arranged on a substrate  400  in relation to first and second positioning projections  410 ,  410 ′ and  420 , respectively. 
         [0059]    As discussed above, the positioning projections  410 ,  410 ′,  420  may have various cross sectional shapes along the x-y plane. For example, the first positioning projections  410 ,  410 ′ may have circular cross sectional shapes along the x-y plane, and the second positioning projections  420  may have an octagonal cross sectional shape along the x-y plane. 
         [0060]      FIG. 4  illustrates two exemplary arrangement patterns for the first positioning projections  410 ,  410 ′ in relation to the first optical element  415 . More particularly, the illustrated arrangement pattern of the first positioning projections  410  may enable the first optical element  415  to be arranged in at least at two different positions relative to the substrate  400 , i.e., where the first optical element is arranged with different rotational positions relative to the first positioning projections  410 , while the first positioning projections  410  are arranged at a same position on the substrate  400 . The illustrated arrangement pattern of the first positioning projections  410 ′ may also enable the first optical element  415  to be arranged at least at two different positions relative to the substrate  400 . More particularly, by rotating a position of the first positioning projections  410 ′ relative to the substrate  400 , the first optical element  415  may also be arranged in different positions relative to the substrate  400 . 
         [0061]    With regard to the second positioning projections  420  and the second optical element  425 , the second positioning projections  420  may allow the second optical element  425  to be arranged at least at two different positions relative to the substrate  400 . More particularly, the octagonal cross sectional shape of the second positioning projections  420  may ensure more precise positioning of the second optical element relative to the second positioning projections  420  and the substrate  400 . Different arrangements of the second optical member  425  may be achieved while the second positioning projections  20  are at the same positions relative to the substrate  400 . 
         [0062]    The positioning projections may be made of any material having sufficient material strength and chemical resistance, and may be made by any process capable of realizing both the aspect ratio and the absolute dimensions thereof. For example, the positional projections may be a polymer or a polymeric vitreous material, e.g., a photopolymer that may be patterned using photolithography, as discussed below with respect to  FIG. 5 . 
         [0063]      FIG. 5  illustrates a flow chart of stages in an exemplary process of forming an optical bench. 
         [0064]    Referring to  FIGS. 1 through 5 , the process may begin in step S 500 , and may proceed to step S 510 . During step S 520 , a substrate, e.g.,  100 ,  200 ,  300 ,  400 , may be cleaned. The substrate may be cleaned using a material, e.g., a solvent, an acid and/or an alkaline, suitable for the material(s) of the substrate. Next, during step S 520 , a surface, e.g.,  101 ,  201 ,  301 , of the substrate may be primed to prepare for photopolymer application. 
         [0065]    Next, during step S 530 , the primed surface may be coated with a photopolymer, e.g., a negative-tone photoresist such as SU-8, to form the positioning projections using lithographic techniques. A thickness of the photopolymer on the substrate may be based on a height of the positioning projections, e.g.,  110 ,  210 ,  210   a,    310 ,  410 ,  410 ′,  420 , to be formed on the substrate, i.e., in accordance with design requirements of the optical bench, e.g.,  10 ,  20 ,  25 ,  30 . 
         [0066]    Next, during step S 540 , portion(s) of the deposited photopolymer may be exposed using, e.g., UV light, based on the desired positions of the positioning projections. 
         [0067]    Next, during step S 550 , the patterned photopolymer may be subjected to a cross-linking process and may be developed to form the positioning projections. 
         [0068]    Next, during step S 560 , the formed positioning projections may be subjected to a heating process. The heating process may help ensure that the formed positioning projections are permanently shaped and fixed to the substrate. 
         [0069]    Next, during step S 570 , optical elements may be arranged on the substrate in relation to the respective positioning projections formed on the substrate. The process may end in step S 580 . 
         [0070]    In some embodiments, prior to depositing a material for forming the projecting portions, e.g., photopolymer, and more particularly, e.g., SU8, an adhesion promoter may be applied on the substrate, e.g., glass, silicon wafer, to aid in the adhesion of the material to the substrate. For example, in embodiments in which the photopolymer is, e.g., SU8, and the substrate is glass or a silicon wafer, hexamethyldisilazane (HMDS) may be deposited therebetween as an adhesion promoter for promoting adhesion between the SU8 and the glass or silicon wafer. 
         [0071]    Exemplary embodiments of the present invention have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.