Abstract:
An optical module for a camera device, the camera device including an image capturing element arranged on a base substrate portion, and has a top lens element and optionally further lens elements for imaging an object on the image capturing element, and further a baffle defining a predetermined field of view of the image capturing element. The baffle includes a generally transparent baffle substrate portion having a front surface and a rear surface, a generally non-transparent first layer with a plurality of first openings on the front surface and a generally non-transparent second layer with a plurality of second openings on the rear surface. The top lens element is arranged on the front and/or the rear surface of the baffle substrate, which leads to a reduced number layers/substrates in the module and to a reduced number of reflections on material-air interfaces, for example. The baffle has an improved ability to suppress unwanted light and enables protection of the inner part of the device as well as manufacture on wafer scale.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is in the field of integrated optical modules, in particular integrated camera devices with an image capturing element, such as a CCD sensor, and at least one lens element for imaging an object on the image capturing element, e.g. a refractive and/or diffractive lens. Integrated device means that all components are arranged in a well defined spatial relationship. Such integrated camera devices are, for example, cameras of mobile phones which are preferably manufactured in a mass production process at low cost. 
         [0003]    More concretely, the invention relates to an optical module for a camera device comprising a baffle that defines a predetermined field of view (FOV) of the image capturing element, while suppressing beam paths coming from points outside this FOV. The invention further relates to a wafer scale package representing a plurality of such optical modules, to a baffle substrate with a plurality of baffles and to methods for manufacturing a plurality of optical modules for camera devices and for manufacturing a baffle substrate. 
         [0004]    2. Description of Related Art 
         [0005]    Especially in the field of mobile phones with cameras, but also for other applications, it is desirable to have a camera device that can be mass produced at low cost in an as simple process as possible and still has a good image quality. Such camera devices comprise an image capturing element and at least one lens element arranged along a common axis and are known from WO 2004/027880, for example. The known camera devices are manufactured on a wafer scale by replicating a plurality of lens elements on a disk-like substrate (wafer), stacking and connecting the substrates to form a wafer scale package (wafer stack) and dicing the stack in order to separate the individual camera devices from one another. 
         [0006]    The camera devices are integrated optical modules, which include functional elements such as the image capturing element and the at least one lens stacked together along the general direction of light propagation. These elements are arranged in a predetermined spatial relationship with respect to one another (integrated device) such that further alignment with each other is not needed, leaving only the integrated device as such to be aligned with other systems. 
         [0007]    Wafer-scale replication of lens elements allows the fabrication of several hundreds of generally identical devices with a single step, e.g. a single or double-sided UV-embossing process. Replication techniques include injection molding, roller hot embossing, flat-bed hot embossing, UV embossing. As an example, in the UV embossing process, the surface topology of a master structure is replicated into a thin film of a UV-curable replication material such as an UV curable epoxy resin on top of a substrate. The replicated surface topology can be a refractive or a diffractive optically effective structure, or a combination of both. For replicating, a replication tool bearing a plurality of replication sections that are a negative copy of the optical structures to be manufactured is prepared, e.g. from a master. The tool is then used to UV-emboss the epoxy resin. The master can be a lithographically fabricated structure in fused silica or silicon, a laser or e-beam written structure, a diamond turned structure or any other type of structure. The master may also be a submaster produced in a multi stage generation process by replication from a (super) master. 
         [0008]    A substrate or wafer in the meaning used in this text is a disc or a rectangular plate or a plate of any other shape of any dimensionally stable, often transparent material. The diameter of a wafer disk is typically between 5 cm and 40 cm, for example between 10 cm and 31 cm. Often it is cylindrical with a diameter of either 2, 4, 6, 8 or 12 inches, one inch being about 2.54 cm. The wafer thickness is for example between 0.2 mm and 10 mm, typically between 0.4 mm and 6 mm. 
         [0009]    If light needs to travel through the substrate, the substrate is at least partially transparent. Preferably, especially if CMOS sensors are present, at least one of the optical surfaces comprises a coating acting as an IR cutoff filter. Otherwise, the substrate can be nontransparent as well. In case of a camera device, at least one substrate bears electro-optical components, like the image capturing element, and may thus be a silicon or GaAs or other semiconductor based wafer; it may also be a CMOS wafer or a wafer carrying CCD arrays or an array of Position Sensitive Detectors. 
         [0010]    Such integrated optical modules can be manufactured by stacking wafers along the axis corresponding to the direction of the smallest wafer dimension (axial direction). The wafers comprise functional elements, like lens elements or image capturing elements, in a well defined spatial arrangement on the wafer. By choosing this spatial arrangement in an adequate way, a wafer stack comprising a plurality of generally identical integrated optical modules can be formed, wherein the elements of the optical module have a well defined spatial relationship with respect to one another. 
         [0011]    By spacers, e.g. a plurality of separated spacers or an interconnected spacer matrix as disclosed in US 2003/0010431 or WO 2004/027880, the wafers can be spaced from one another, and lens elements can also be arranged between the wafers on a wafer surface facing another wafer. 
         [0012]    It is known to place a baffle in front of the top lens element of a camera device. A baffle is an element that defines a three-dimensional passage for light but is otherwise intransparent for light. In a camera device, a baffle serves to define a field of view (FOV) of the image capturing element and to suppress beam paths coming from points outside this FOV. Known baffles consist of a layer of non-transparent material having a given thickness in an axial direction and a through-hole for light transmission with normally varying cross sectional areas. In known baffles, the through-hole has the shape of a truncated cone with a given extent in the axial direction and given opening angle. The thickness as well as the angle of the side walls of the through hole determines the FOV and the critical angle (collection angle) under which incident light can pass the baffle and enter the camera device. It is often desired that the collection angle does not exceed a predetermined value. This is because light entering the device under higher angles is stray light and/or may not directly fall onto the photosensitive part of the image capturing element but may hit the photosensitive part only after one or more reflections inside the camera device. This may lead to artifacts in the image generated by the image capturing element, and, thus, to a reduced image quality. 
         [0013]    Known baffles have thus a thickness of several 100 μm (e.g. 100-300 μm) and side walls of the through hole which are tapered with respect to the normal direction of the front wall baffle such that an opening with a varying cross section having a diameter in the range of 1-3 mm is formed. This, among other parameters of the sensor and optical system, restricts the full angle of the field of view to about 40 to 80°. A disadvantage of such baffles are reflections at the side walls of the through hole which also lead to artifacts in the image generated by the image capturing element, and thus to a reduced image quality. Reduction of the area of the side walls, however, is not possible, because this would lead to an increased collection of unwanted stray light. 
         [0014]    Known baffles are normally injection molded parts. They are attached to the integrated camera device only after its complete manufacture, i.e. after the dicing step if a wafer scale manufacturing process is employed. This is not compatible with low cost wafer scale manufacture of the optical modules. The additional steps of attaching each individual baffle to each individual camera device associated therewith is time-consuming and complicated and thus another disadvantage of known modules and manufacturing processes. 
         [0015]    A further disadvantage is that the optical system, or at least the top lens element, is fully accessible via the through hole. This may lead to damage and contamination. 
         [0016]    WO 2005/041561 discloses a camera module and manufacturing method thereof, where a semiconductor housing comprises a solid-state image sensor and a lens element located above the solid-state sensor. The housing forms a shield against laterally scattered radiation, by having at least one plate of transparent material of which two sides are covered with a radiation-opaque layer which is provided with an aperture. The aperture in the layer, close to the sensor, has a smaller surface than the aperture in the layer located remote from the sensor. The lens element is formed in a transparent substrate which is sandwiched in between the image sensor and the plate with the apertures. This construction has the disadvantage that the number of optical interfaces (e.g. air/glass) is increased, leading to losses due to reflections at these faces. 
       BRIEF SUMMARY OF THE INVENTION 
       [0017]    It is an object of the invention to provide an optical module for a camera device with improved image quality. 
         [0018]    It is a further object of the invention to provide an optical module for a camera device that can be manufactured in a mass production process at low cost, and a corresponding manufacturing process. 
         [0019]    It is a further object of the invention to provide a wafer scale package comprising a plurality of generally identical optical modules for camera devices. 
         [0020]    It is a further object of the invention to provide a baffle substrate with a plurality of baffles and a corresponding manufacturing method. 
         [0021]    The optical module for the camera device comprises a top lens element and optionally further lens elements for imaging an object on the image capturing element. It further comprises a baffle which defines a field of view of the image capturing element in the assembled camera device by geometrically determining a critical angle under which incident light can enter the camera device and eventually fall onto a photosensitive part of the image capturing element. An image capturing element arranged on a base substrate portion is present in the completed camera device. According to the invention, the baffle comprises a generally transparent baffle substrate portion having a front surface and a rear surface. It further comprises a generally optically non-transparent first layer on the front surface which has a first opening in an inner region of the front surface, and a generally optically non-transparent second layer on the rear surface which has a second opening in an inner region of the rear surface. This generally corresponds to two planar apertures that are arranged at a distance from one another, as seen in a direction normal to their planes, with the transparent substrate sandwiched in between the layers. The layers can be very thin (e.g. several hundred nm or few atom layers), because it only needs to have a thickness sufficient to achieve an optical density that is sufficient to completely or at least partially block light transmission through the layer. Light can then reach the image capturing element only by passing through the first opening and subsequently through the second opening. Among other parameters, the field of view is determined by the shape of the two openings, their axial distance and their lateral position with respect to one another. 
         [0022]    The first and second openings are arranged at an axial distance from one another, said distance being defined by the thickness of the baffle substrate. This distance may correspond to the thickness of the non-transparent layer in conventional baffles, but may also be smaller. The shape of the openings may, for example, be circular, wherein the circles are preferably concentric. Preferably, the first opening has a larger diameter than the second opening. 
         [0023]    The top lens element is arranged on the front or rear surface of the baffle substrate in the region of the first or second opening in the non-transparent layer. 
         [0024]    In combination, the spaced apart first and second openings with the lens element directly attached to the baffle substrate portion form a passage for light that has generally the same effect as a conventional baffle with a through-hole and a lens spaced therefrom, but the following advantages:
       Though the double layers with first and second openings have the same effect as a through hole with spaced front and rear surfaces, there are no physical side walls present. Consequently, there are no artifacts caused by reflection at such side walls. Light enters the camera device either without reflections, or not at all. Light rays that would hit the side walls of the through-hole in a conventional baffle here enter the transparent baffle substrate portion. They are trapped by total internal reflection and consequently suppressed.   As there is no through-hole, all lens elements arranged inside the camera device are fully protected from damage or contamination. In particular, the baffle substrate ensures scratch protection of the top lens, if it is arranged on the rear surface. It can also ensure protection of further optical elements, including lens elements and the image capturing element, from contamination and damage during the dicing step in a wafer scale manufacturing process.   The baffles can be manufactured on a wafer scale, e.g. by coating a transparent substrate (wafer) such that non-transparent layers are formed on both main surfaces, and by removing the coating in predetermined regions in order to form a plurality of first and second openings. This makes the attachment of the baffles fully compatible with a wafer scale manufacturing process of the camera device as such (without the baffle). It can be done without attaching individual baffles to individual integrated devices, and thus in a much more efficient way and at reduced cost.   Forming the through-hole in conventional baffles is mechanically complicated. According to the invention, no through-hole is needed. The openings in the first and second layers, which are much thinner than the conventional baffle, can be formed by known techniques, e.g. by photolithography, on a wafer scale. Thus, manufacture of the baffle as such is easier.   The baffle substrate serves as a substrate for the top lens. For example, the top lens may be arranged on the rear surface in close proximity of the second opening. As a consequence, the baffle substrate has a double function, and it can be done without a separate carrier substrate for the top lens. The whole module can thus be made thinner and with less components. Furthermore, the number of material interfaces (air-glass, air-plastic) within the module is reduced. Efforts for special treatment of the surfaces or other corrections in order to reduce reflections and to improve image quality can thus be reduced. If, as in a preferred embodiment, the front surface of the baffle substrate portion, is planar (with exception of the layer), all lens elements present are arranged in the interior of the module and thus protected from contamination and damage.   The baffle can be manufactured by applying one or more non-transparent layers to one or more transparent substrates. This has the advantage that arbitrary shapes of the opening and of the three dimensional passage for light can be realized. The shape of the opening can, for example, be adapted to the shape of the active sensor area to achieve a more homogenous light distribution on the sensor. For rectangular sensors it is advantageous to use openings that have a generally rectangular base wherein the side lines are curved in a concave or convex manner (cushion shape, barrel shape). Any surface of any substrate may serve as a carrier for a non-transparent layer, and also more than two layers, e.g. three or four, may be present with arbitrary shapes of the respective opening.       
 
         [0031]    The top lens element is generally a convex semi-lens, wherein the lens is arched towards the image capturing element. It should be noted that, in conventional designs, the top lens element is always placed on top of a substrate, thus being arched towards the object to be imaged. In one embodiment of the invention, the top lens element of the invention is “reversed” with respect to such known designs. The invention enables a design where two lens elements are arranged on different substrates and face one another. Regarding the optical function, this generally corresponds to a classical double-sided lens or two lens elements on a common substrate. The “reverse” design, however, provides additional freedom of design, as parameters like the distance of the two curved surfaces are not limited by the thickness of the substrate, but can be freely chosen. 
         [0032]    As the front surface of the baffle substrate portion is preferably planar, the baffle substrate can, over its entire area, rest against a support during replication of the top lens elements on its rear surface. The baffle substrate thus does not need to have the stability required for replication by itself; it can be made thinner than conventional substrates. 
         [0033]    The invention further relates to a wafer scale package, comprising a baffle substrate a plurality of a top lens elements, optionally a base substrate with a plurality of image capturing elements, and optionally further lens elements for imaging an object on the image capturing elements. The generally transparent baffle substrate has a generally planar front surface and a generally planar rear surface, a generally non-transparent first layer with a plurality of second openings on the front surface and a generally non-transparent second layer with a plurality of second openings on the rear surface, wherein the first and second openings are shaped to define, among other parameters, a predetermined field of view of the image capturing element. The top lens elements are arranged on the front or rear surface of the baffle substrate. In addition to the advantages of the optical module or the camera device itself, the package has the advantage that individual devices/camera devices already comprising baffles can be manufactured in a mass production process from said wafer scale package by means of dicing. 
         [0034]    The camera device as well as the package may also contain a spacer or a spacer layer, e.g. a spacer wafer or spacer plate with a plurality of openings or a plurality of individual spacers. The spacer or spacer layer ensures a well defined distance between the substrates and consequently between the baffle, the lens elements and the image capturing element. In a preferred embodiment, the lens elements are fully encapsulated by the substrates and the spacers, and are thus well protected. 
         [0035]    The invention further relates to a method for manufacturing a plurality of optical modules for camera devices on a wafer scale, comprising the following steps:
   1. Providing a generally transparent baffle substrate having a front surface and a rear surface, a generally non-transparent first layer with a plurality of first openings on the front surface and a generally non-transparent second layer with a plurality of second openings on the rear surface, and with a plurality of lens elements on the front or rear surface. The baffle substrate may be a glass wafer, or consist of any other transparent material. The non-transparent layers may be constituted by a thin film on the respective surfaces, e.g. formed by applying a non-transparent foil or a coating of suitable material and with suitable thickness (e.g. by PVC, sputtering, CVD, painting, spraying, immersing or other processes).   2. Optionally, also spacer layers and/or further lens elements arranged on further (intermediate) substrates are provided.   3. The substrates are then stacked and connected to one another in such a way that the top lens elements, and the first and second openings and optionally also the spacers and/or further lens elements are arranged in a predetermined spatial relationship. Usually, this step includes alignment of the elements present on the different substrates along common axes.   4. The package is then diced along predetermined planes, in order to separate the individual modules from one another.   
 
         [0040]    Optionally, in case of wafer scale production of complete camera devices:
   5. Providing a base substrate having a plurality of image capturing elements prior to or after dicing. The base substrate may be a silicon or GaAs or other semiconductor based wafer; it may also be a CMOS wafer or a wafer carrying CCD arrays or an array of Position Sensitive Detectors.   
 
         [0042]    Preferably, the top lens elements are formed on the baffle substrate by means of a replication process. Preferably, at first, the first and second layers are formed by depositing a material on the surfaces. Then, openings are formed by selectively removing this material in certain regions, e.g. by photolithography and etching. Then, the top lens elements are replicated in the regions of the openings, preferably covering a slightly larger area than the second openings. The openings could also be formed by depositing material on selected regions of the front and rear surface, e.g. by protecting certain areas with a shield or an anti-adhesion coating. 
         [0043]    The baffle substrate with the lens elements could also be manufactured in one piece, e.g. by injection molding or another replication process. 
         [0044]    The invention further relates to a baffle substrate with a plurality of baffles, and to a corresponding manufacturing method. The baffle substrate comprises a generally transparent substrate having a front surface and a rear surface, a generally non-transparent first layer with a plurality of second openings on the front surface and a generally non-transparent second layer with a plurality of second openings on the rear surface, as well as a plurality of lens elements attached to the front or rear surface. It is manufactured by providing a generally transparent substrate having a front surface and a rear surface, e.g. a glass wafer; providing the front surface with a generally non-transparent first layer and providing the rear surface with a generally non-transparent second layer, e.g. by applying a thin film or coating, for example by means of PVD, sputtering, CVD or other material depositing processes; and providing the first layer with a plurality of first openings and providing the first layer with a plurality of second openings, preferably by photolithography. 
         [0045]    One preferred application of the camera device is for CMOS cameras, including CMOS cameras for mobile phones. Here, the front surface of the baffle substrate, which can be flat and unstructured with the exception of the (thin) first layer, could be directly used as the cover window of the camera, of a module within the camera, or even of the phone cover instead of a separate cover window. This leads to both simplified assembly and lower material cost. 
         [0046]    Among others, the invention has the advantages that the number of optical interfaces and losses in connection therewith can be reduced, smaller axial dimensions of the device can be achieved, unwanted light can be suppressed more efficiently, protection of functional elements of the module is ensured during manufacture and use, and the production process of the baffles as well as of the complete devices is fully compatible with a wafer scale manufacture, and can thus be realized in a mass production process at low costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]      FIG. 1  shows schematically a camera device according to the prior art; 
           [0048]      FIG. 2  shows schematically a baffle according to the invention; 
           [0049]      FIGS. 3-7 ,  11  show schematically camera devices according to the invention; 
           [0050]      FIGS. 8   a - d  show schematically details of the manufacturing process; 
           [0051]      FIGS. 9 &amp; 10  show baffle substrates; 
           [0052]      FIG. 11  shows a camera device wherein the first openings as smaller than the second openings; 
           [0053]      FIGS. 12   a - c  show examples for the shape of the first and second openings; 
           [0054]      FIGS. 13   a - c  show further examples for camera devices with three or four non-transparent layers. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0055]    The camera device  1  according to the prior art comprises an optical system with one bi-convex lens, which is here constituted by two half-lenses  3 ,  4  arranged on a front surface  6  and a rear surface  7  of a lens substrate portion  5 . The lens elements  3 ,  4  are replicated lens elements, for example. The camera device  1  further comprises a base substrate portion  8  with an image capturing element  9 , e.g. a CMOS substrate with an image sensor. The lens substrate portion  5  and the base substrate portion  8  are stacked in an axial direction z (normal to their main surfaces) and are spaced from one another by means of spacers  10 . Thereby, a well defined axial distance between the lens elements  3 ,  4  and the image capturing element  9  is realized. The modules consisting of the lens substrate portion  5 , spacers and base substrate portion  8  are typically manufactured on wafer scale by means of providing a lens substrate having a plurality of lens elements  3 ,  4 , providing a spacer layer, e.g. a spacer substrate having a plurality of through-holes, and providing a base substrate having a plurality of image capturing elements  9 ; then stacking and connecting these substrates, and subsequent dicing. 
         [0056]    According to the prior art, these individual modules are provided with a baffle  2 , only after the dicing step. A typical known baffle  2  is shown in  FIG. 1 . It comprises a front wall  20  running parallel to the substrate portions  5 ,  8  and side walls  22 ,  24  running perpendicular thereto. The baffle  2  encloses the module in the way of a housing. A typical thickness t of the front wall is 100-300 μm. The baffle  2  is typically made of plastic, e.g. in an injection molding process. 
         [0057]    The front wall  20  of the baffle  2  has a through-hole  26  with a typically circular cross section which serves as an entry aperture for light. The viewing angle or field of view of the image capturing element  9  is defined by the distance of the through-hole  26  to the image capturing element  9 , as well as the diameter of the through-hole  26 . The side wall  26   a  of the through-hole  26  is tapered and defines a cone with an opening angle Ω. The front wall  20  with a thickness t of several 100 μm has the effect that light incident on the device or the front wall  20  under small angles of incidence α is prevented from entering the camera device  1  via the through-hole  26  (for an infinitesimal small thickness t, also light impinging under α≈0° would enter the module). Consequently, the baffle  2  defines a collection angle θ collect  for incident light. It is desired that θ collect  is smaller than 90°, because rays entering under a very small angle of incidence generally correspond to stray light and/or lead to reflections/straying within the module. 
         [0058]    On the other hand, the non-infinitesimally small thickness t of the front wall  20  leads to artifacts in the image generated by the image capturing element  9 . As shown in  FIG. 1 , there can be reflections/straying at the side wall  26   a  of the through hole  26 . Such a reflected ray  28  is schematically shown in bold dashed lines. These reflections are an intrinsic problem of the prior art baffles. 
         [0059]    Another problem is that the top lens element  3  is freely accessible through the through-hole  26 . It can thus be contaminated or damaged during manufacture of the device or during use. 
         [0060]      FIG. 2  shows a baffle  30  according to the invention. The baffle  30  comprises a generally transparent baffle substrate portion  32 , e.g. a portion of a glass wafer or any other generally planar piece of material, which is generally transparent in the optical range. 
         [0061]    In this embodiment, the baffle substrate portion  32  has a generally planar front surface  33  and a generally planar rear surface  34 , i.e. without a cut-out like the prior art through hole  26 . The substrate portion  32  has a thickness t′, e.g. in the range of 150-500 μm. As shown in  FIG. 4  or  6 , there could be a lens element attached to the rear surface  34 . The baffle substrate portion could also be pre-shaped with, for example, integrated spacers. 
         [0062]    There is a first layer  35  of generally non-transparent material on the front surface  33  and a second layer  36  of generally non-transparent material on the rear surface  34 . The layers  35 ,  36  cover the whole area of the respective surface  33 ,  34  with the exception of a first and second opening  37 ,  38  in a middle region thereof. The openings  37 ,  38  preferably have the shape of circles with diameters d 1  and d 2 . They could have other shapes as well. In this example, the openings  37 ,  38  are arranged concentrically with respect to one another, as seen in an axial direction. The center of the openings  37 ,  38  preferably, but not necessarily corresponds to the optical axis of the completed module (as shown in  FIG. 3 ). The diameter d 1  of the first opening  37  is greater than the diameter d 2  of the second opening  38 . Both diameters range from 0.5 tot mm, for example. 
         [0063]    This arrangement of the two spaced apart layers  35 ,  36  with their respective openings  37 ,  38  has generally the same effect as the baffle  2  of the prior art with its through-hole  26 . In particular, the openings  37 ,  38  define the angles Ω and θ collect  as described above and thus enable definition of the field of view as well as suppression of light incident under small incidence angles. Light can enter the module via the openings  37 ,  38  and the transparent material of the baffle substrate portion  32 . 
         [0064]    The advantage of the invention is also illustrated in  FIG. 2 : A ray  28  corresponding to an incidence on the side wall  26   a  in  FIG. 1  is shown in bold dashed lines. This ray  28  is not reflected, because there are no physical side walls. Instead, it enters the baffle substrate portion  32  and is reflected at the interface to the first and second layers  35 ,  36 . Consequently, the light cannot pass the baffle  30 . 
         [0065]    Another advantage is that the baffle  30  according to the invention can act as cover window for the optical module because of the continuous, but in parts transparent baffle substrate. 
         [0066]    The baffle  30  according to the invention has, by means of the two layers  35 ,  36  on both sides of a transparent substrate and the openings therein, an optically transparent, but mechanically impermeable window which has advanced performance compared to prior art baffles. 
         [0067]    A lens element  3  is arranged on the rear surface  34  of the baffle substrate portion  32  in the region of the second opening  38 . The lens element corresponds to the top lens element  3  in  FIG. 1 . It covers the complete area of the second opening  38 , and is even wider, such that all light passing through the opening  38  is affected by the lens element  3 . The second layer is, at least in the bordering regions of the opening  28 , sandwiched between the material of the lens element  3  and the baffle substrate portion  32 . The lens  3  could also be laterally smaller than the opening  38 . 
         [0068]      FIGS. 3-7  show camera devices  1  with a baffle  30  as shown in  FIG. 2 . These embodiments have the advantage that the baffle substrate portion  30  is used to support the lens needed to image an object onto the image capturing element. This is not possible with prior art devices. It can thus be done without a separate lens substrate or lens substrate portion, and the camera device can have a smaller extent in axial direction. 
         [0069]      FIG. 3  shows a stack comprising the baffle  30  (acting as top lens substrate  5 ) as shown in  FIG. 2 , a further substrate portion  13  and two layers of spacers  10 ,  11  stacked in axial direction z and connected to one another to form an optical module  40 . A camera device  1  is formed by connecting a base substrate portion  8  (or a complete base substrate prior to dicing) with an image capturing element  9  to the stack. The further substrate portion  5  comprises one lens elements  4  attached to its front surface. The top lens element  3  on the baffle substrate portion  32  and the upper lens element  4  on the further substrate portion  5  correspond to the two halves of the conventional lens  3 ,  4  in  FIG. 1 . The “reverse” arrangement of the lens elements with respect to  FIG. 1  is illustrated. 
         [0070]    The upper spacers  11  between the further substrate portion  13  and the baffle  30  serve for keeping the lens elements  3 ,  4  at an axial distance from one another. The lower spacers  10  between the top lens substrate portion  5  and the base substrate portion  8  serve for keeping the further substrate portion  13  at an axial distance from the front surface of the base substrate portion  8 . 
         [0071]    The baffle  30  limits the field of view of the image capturing element  9 , reduces artifacts caused by rays incident through the first opening  37  in between the two layers  35 ,  36  and, as an additional effect, also serves as cover glass to protect the inside of the camera device  1  or the device  40 , in particular the top lens element  3  from damage and contamination. 
         [0072]      FIG. 4  shows a further example of the invention. The camera device  1  comprises a baffle with a baffle substrate portion  32  as shown in  FIG. 2 , a base substrate portion  8  with an image capturing element  9  and spacers  10  between these two substrate portions  32 ,  8 . The top lens element  3  is directly attached to the rear surface  34  of the baffle substrate portion  32 . The top lens element  3  covers partly or completely the second opening  38  in the second layer  36 . It may be replicated directly on the baffle substrate, or otherwise attached thereto. 
         [0073]      FIG. 5  shows a variant of the embodiment of  FIG. 4 , where the top lens element  3  is arranged on the front surface  33  of the baffle substrate portion  30 , where it covers the first opening  37 . 
         [0074]      FIG. 6  shows a further embodiment of the invention. The camera device  1  comprises a baffle substrate portion  32  with the top lens  3  attached to its rear surface and a base substrate portion  8  with an image capturing element  9 . It further comprises a further substrate portion  13  arranged between the baffle substrate portion  32  and the base substrate portion  8  and spaced with two layers of spacers  10 ,  11  therefrom. The further substrate portion  13  comprises two lens elements  4 ,  4 ′ on both of its surfaces. 
         [0075]    It is also possible that there is more than one single or double sided intermediate substrate portion. 
         [0076]      FIG. 7  corresponds to a combination of the embodiments of  FIGS. 4 and 7 : Lens elements  3 ,  4  are arranged on both surfaces  33 ,  34  of the baffle substrate portion  30 . 
         [0077]      FIGS. 8   a - d  show different steps of the process of manufacturing an optical module or camera device according to the invention on a wafer scale, e.g. a module as shown in  FIG. 4 . In  FIG. 8   a , an optically transparent substrate  320  is provided and coated on both main surfaces in order to produce a thin, optically non-transparent layer  35 ,  36 . The coating material is preferably a mix of Chromium and Chromiumoxide, applied in a PVD process and having a total thickness in the range of some 100 nm (e.g. 500 nm), i.e. a few atom layers. This is generally sufficient to produce an optically dense structure that absorbs incoming light. The coating could as well be any other absorbing material, applied in a PVD, CVD, sputtering or other process. The coating could also be a thin plastic film or foil. 
         [0078]    In the next step, which is shown in  FIG. 8   b , first openings  37  are produced in the first layer  35 , and second openings  38  in the second layer  36 . Preferably, a photolithographic technique is used to form the openings  37 ,  38 : A light-sensitive photoresist is applied to the respective layer and optically illuminated with a mask. A series of chemical treatments then engraves the exposure pattern into the material underneath the photoresist. 
         [0079]    As an alternative, the openings  37 ,  38  can be produced at the same time as the layers  35 ,  36  by leaving certain areas blank. This could be achieved by covering these areas with a material to which the material of the layers  35 ,  36  does not adhere, such that it can be washed off. 
         [0080]    In the next step, which is shown in  FIG. 8   c , lens elements  3  are formed on the rear surface of the baffle substrate  320  in the regions of the second openings  38 . They are preferably formed by means of a replication technique on wafer scale. For example, a replication tool having replication sections with a surface structure corresponding to the negative of the shape of the lens elements  3  is provided, and then aligned and brought into contact with the substrate  320  with a replication material between the replication sections and the rear surface of the substrate  320 . The replication material is then hardened. 
         [0081]    In addition, further lens elements could also be formed on an intermediate substrate ( FIG. 3  or  FIG. 6 ). 
         [0082]    An additional substrate  50 , which could be a substrate carrying a plurality of lens elements or a base substrate carrying a plurality of image capturing elements, is aligned with and brought into contact with the substrate  320 . A layer of spacers  10 , e.g. a spacer matrix, is arranged in between the substrates  320 ,  50 . The spacers and substrates are then connected, e.g. by means of a UV-curable adhesive, in order to form a wafer stack  100  (wafer scale package). 
         [0083]    Such a completed stack  100  is shown in  FIG. 7   d . Individual optical modules  40 , or, in case of a base substrate with image capturing elements as additional substrate  50 , camera devices  1  are formed by dicing the stack  100  along planes P running in an axial direction, preferably through the spacers  10 . 
         [0084]      FIGS. 9 and 10  show plan views of the baffle substrate  320 , here by way of example of the rear surface. The substrate  320  comprises a circular plate. An optically intransparent layer  36  is formed thereon, here on the rear surface of the substrate  320 . Openings  38  are formed in the layer by means of removing deposited material or by selectively depositing material only in the areas around the openings  38 . 
         [0085]    In  FIG. 10 , the layer  36  is formed only in regions around the openings  38 , while leaving other areas uncovered. These free areas have improved surface properties, e.g. for bonding the spacer substrate to the baffle substrate by means of an UV curable adhesive. 
         [0086]      FIG. 11  shows an embodiment of the invention where the first openings  37  in the first layer  35  on the front surface  33  are smaller than the second openings  38  in the second layer  36  on the rear surface  34 . The effect is generally the same as illustrated in  FIG. 2 . Lens elements  3 ,  4  may be present on one or both surfaces  33 ,  34 . 
         [0087]      FIGS. 12   a - c  show examples for non-circular shapes of the first and second openings  37 ,  38 .  FIG. 12   a  shows a rectangular opening  37 ,  38 .  FIG. 12   b  shows a cushion shape, and  FIG. 12   c  a barrel shape. 
         [0088]    Generally, the contour of the opening preferably corresponds to the image of the active area of the sensor in the plane of the opening, as generated by the lens elements. The spot of light passing through the opening thus has the shape of the sensor, the sensor is illuminated homogeneously, and scattered light is reduced. 
         [0089]    Baffles with the described non-circular shapes can also be used in connection with other optical modules or camera devices, e.g. as shown in the other figures. In particular, also conventional baffles (real holes in a substrate that has a certain thickness in direction of the optical axis) could be shaped like that. The contour preferably has 2-fold or 4-fold symmetry. Rectangular, cushion-like or barrel-like shapes are preferred in connection with rectangular sensors.  FIGS. 13   a - c  show that the invention is not limited to the case where a baffle is defined by two intransparent layers. The three-dimensional passage for light can as well be defined by three or more layers  35 ,  36 ,  36 ′,  36 ″ with corresponding openings therein. The openings may have an arbitrary shape, e.g. circular or like in  FIGS. 12   a - c . The shapes are not necessarily the same. The diameters can increase or decrease in direction of light propagation, or can first decrease, then increase or vice versa. Preferably, lens elements are arranged also between the first and last layer, as seen in direction of light propagation. 
         [0090]    The camera device of  FIG. 13   a  has two substrates or substrate portions. It generally corresponds to the embodiment of  FIG. 6  with the exception that there are three non-transparent layers  35 ,  36 ,  36 ′, arranged on the top and rear surface of the first substrate and on the top surface of the second substrate. 
         [0091]    The device of  FIG. 13   b  corresponds to  FIG. 13   a , but has four non-transparent layers  35 ,  36 ,  36 ′,  36 ″ arranged on both surfaces of the two substrate portions. 
         [0092]    In the embodiment of  FIG. 13   c , there are three non-transparent layers  35 ,  36 ,  36 ′,  36 ″, arranged on the surfaces of the two substrates, with the exception of the top surface of the first substrate.  FIGS. 13   a - c  show the versatility of the invention and the ability to create almost any shape of the three dimensional passage. There could be even more substrates with corresponding non-transparent layers and with or without lens elements.