Abstract:
A novel digital camera module includes an image capture device, a lens unit including a body, a housing including an opening for receiving the lens unit and positioning the lens unit with respect to the image capture device, and a contaminant trap formed by an isolated annular space between the lens unit and the opening of the housing. In a particular embodiment, the opening of the housing includes surfaces having at least two different perimeters, the smaller of which slidably engages the outer surface of the lens unit. The contaminant trap collects and contains any contaminants before they reach vulnerable components such as the image capture device and/or other optical components within the camera module.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of prior U.S. Provisional Patent Application Ser. No. 60/864,348, filed on Nov. 3, 2006 by at least one common inventor, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to electronic devices, and more particularly to digital camera modules. Even more particularly, the present invention relates to a system for focusing a digital camera module that prevents debris and particulate matter produced by the focusing process from contaminating the sensor array of an image capture device. 
     2. Description of the Background Art 
     Digital camera modules are currently being incorporated into a variety of electronic devices. Such camera hosting devices include, but are not limited to, cellular telephones, personal data assistants (PDAs), and computers. The demand for digital camera modules continues to grow as the ability to incorporate the camera modules into host devices expands. Therefore, one design goal of digital camera modules is to make them as small as possible so that they will fit into an electronic device without substantially increasing the overall size of the device. Means for achieving this goal must, of course, preserve the quality of the image captured by the camera modules. 
     Such digital camera modules typically include a substrate, an image capture device, a housing, and a lens unit. The substrate is typically a printed circuit board (PCB) that includes circuitry to facilitate data exchange between the image capture device and the host device. The image capture device is mounted and electrically coupled to the circuitry of the PCB. The housing is then mounted on the PCB over the image capture device. The housing includes an opening that receives and centers the lens unit with respect the image capture device. Typically, the opening includes a set of threads and the lens unit includes a complementary set of threads that facilitate the factory focusing of the camera module. During a factory focus operation, for example, focusing equipment rotates the lens unit with respect to the housing, which adjusts the distance between the lens unit and the image capture device. When the lens unit is properly focused, it is fixed in position with respect to the housing with an adhesive, a thermal weld, or the like. 
     Although camera modules that are focused via thread sets provide for relatively accurate focal adjustments, they still have disadvantages. For example, as the lens unit is rotated within the housing, sliding friction between threads creates particulate debris that could easily contaminate the image sensor and/or other optical components (e.g., infra-red filters, protective covers, other lenses, etc.). Consequently, these contaminants accumulate and noticeably degrade the quality of images captured by, for example, blocking light to the image sensor. 
     It should be noted that although threaded components are used here as an example, other types of focusing components can similarly produce particulate debris that reduces the quality of the captured images. For example, U.S. Pat. No. 6,426,839 issued to Dou et al. discloses a camera module including a plurality of ramps formed directly on a stationary lens located inside the camera module. A rotatable lens carrier (having a separate lens) includes a plurality of legs that engage the ramped surfaces of the stationary lens. Rotating the lens carrier causes the legs of the lens carrier to move up or down the ramped surfaces of the lens, thereby moving the second lens closer to or further from the stationary lens, depending on the direction of rotation. Because the legs of the lens carrier slide over the ramped surfaces of the stationary lens, particulate debris can still be produced and collect on the imaging components of the camera module. 
     In addition to particulate debris produced by friction, ramped housings are also susceptible to other contaminants. For example, adhesives used to fix lens units to housings can easily run down into the camera module and contaminate the imaging components. Ramped modules are particularly susceptible to fluid contamination because the interface between the lens unit and the housing is typically not as tight as that of threaded camera modules. Generally, the walls of the lens unit and the housing are smooth, as opposed to having threads formed thereon. In addition to providing a path for contaminant entry, the loose fit between the lens unit and the housing can allow the lens barrel to fall out of the housing during steps of the manufacturing process that occur prior to fixing the lens unit to the housing, thereby reducing yield. 
     In efforts to minimize the accumulation of such contaminants, manufacturers have employed contaminant collecting surfaces within camera modules. For example, U.S. 2006/0103953 (Lee et al.) discloses a camera module that includes a particle collecting groove defined within the housing. In particular, the groove is formed around the peripheral surface of the light receiving aperture of the housing. The groove collects some the debris before it can reach the image sensor or other optical components within the camera module. 
     Although the groove formed on the camera module disclosed in U.S. 2006/0103953 reduces the amount of debris that collects on the image sensor, there are still some disadvantages. For example, debris is still free to move out of the groove because the groove is not entirely isolated. Further, it is unlikely that the camera module will remain upright during use, thus debris is free to fall back out of the groove and obstruct the image sensor and/or optics. 
     What is needed, therefore, is a camera module design that minimizes the contamination of optical components during assembly and focusing processes. What is also needed is a camera module design that isolates contaminants before they collect on components within the camera module. 
     SUMMARY 
     The present invention overcomes the problems associated with the prior art by providing a camera module that includes a contaminant trap for collecting contaminants that may enter the camera module. In addition, features are provided for temporarily locking a lens unit of the camera module in position with respect to a housing of the camera module, and also for limiting tilt of the lens unit with respect to the housing. 
     According to one embodiment, a camera module includes an image capture device, a lens unit and a housing. The lens unit includes a body that extends perpendicularly with respect an image capture surface of the image capture device. The body of the lens unit includes a first surface having a first outer perimeter (e.g., a circumference) parallel to the image capture surface of the image capture device. 
     The housing includes a mounting portion and a receiver portion. The mounting portion is coupled to the image capture device. The receiver portion defines an opening for receiving the lens unit. The receiving portion of the housing includes a first surface having a first inner perimeter and a second surface having a second inner perimeter. The first inner perimeter is smaller than the second inner perimeter, and the first surface of the opening is disposed between the second surface of the opening and the image capture device. 
     When the lens unit is positioned in the receiver portion of the housing, the first surface of the lens unit slidably contacts the first surface of the opening, thereby preventing contaminants from passing between the first surface of the lens unit and the first surface of the opening. The first surface of the lens unit remains in contact with the first surface of the receiver portion, even when the lens unit is moved along an axis perpendicular to the image capture surface (e.g., during a focusing operation), thereby maintaining the integrity of the particle trap. 
     The first surface of the opening and the second surface of the opening are joined by a first contaminant collecting surface. In a particular embodiment, the contaminant collecting surface includes a flat (optionally tilted) surface parallel to the image capture surface (e.g., a horizontal ledge). Alternatively, the contaminant collecting surface defines a channel. As shown, a plurality of various types to contaminant collecting surfaces can be used together in a single embodiment. 
     In the embodiment shown, the lens unit further includes a second surface having a second outer perimeter. The second outer perimeter is larger than the first outer perimeter, and the second surface of the lens unit slidably contacts the second surface of the opening. 
     The outer surfaces of the lens unit and the inner surfaces of the housing together form a particle trap in the form of an enclosed annular space, which is apart from the image capture surface. In particular, the first and second surfaces of the opening are joined by a first transitional surface, and the first and second surfaces of the lens unit are joined by a second transitional surface. Together, the first transitional surface, the second surface of the opening, the second transitional surface, and the first surface of the lens unit enclose the annular space. The space remains enclosed, even when the lens unit is moved, the volume of the annular space increasing as the distance between the lens unit and the image capture device is increased. 
     The disclosed embodiment includes additional particle traps. The opening in the housing includes a third surface having a third inner perimeter larger than the second inner perimeter of the second surface. The second surface is disposed between the third surface and the image capture device, and the third surface of the opening is joined to the second surface of the opening by a third transitional surface. Similarly, the lens unit also includes a third surface having a third outer perimeter, which is larger than the second outer perimeter of the second surface. The third surface of the lens unit slidably contacts the third surface of the receiver portion and is joined to the second surface of the lens unit by a fourth transitional surface to form a second particle trap. 
     The second particle trap has an annular shape and is bounded by the third surface of the opening, the third transitional surface, the second surface of the lens unit, and the fourth transitional surface. The annular space remains bounded, even when the lens unit is moved, the volume of the annular space increasing as the distance between the lens unit and the image capture device is increased. 
     The disclosed embodiment includes yet a third particle trap. The opening in the housing includes a fourth surface, which has a fourth inner perimeter that is larger than the third inner perimeter. The third surface of the opening is disposed between the fourth and second surfaces of the opening, and the third surface is joined to the fourth surface by a fifth transitional surface. The fourth surface of the opening, the fifth transitional surface, and the third surface of the lens unit form at least a portion of the third particle trap. The third particle trap also serves to trap excess adhesive used to bond the lens unit to the housing. 
     A focus mechanism is also disclosed. In the example shown, a plurality of ramps are formed on one of the lens unit and the housing, and a plurality of ramp engaging structures (e.g., complementary ramps) are formed on the other of the lens unit and the housing. At least one of the ramps forms a recess (e.g., a channel) for receiving an adhesive. Alternatively, the focus mechanism can include a thread set on the lens unit and a complementary thread set on the housing. 
     The camera module also includes an optional locking feature operative to temporarily secure the lens unit to the housing during the manufacturing process. The locking mechanism includes a first portion formed on the lens unit and a second portion formed on the housing. In the embodiment shown, the first portion of the locking mechanism includes a plurality of protrusions (e.g., ribs) formed on an outer surface of the lens unit. The second portion of the locking feature includes raised areas on an inner surface of the receiver portion of the housing. When the protrusions engage the raised areas, the lens unit is locked in place in the housing. 
     The protrusions also provide a stabilizing function. In particular, the protrusions extend a sufficient distance in a direction perpendicular to the image capture surface to limit the tilt of the lens unit within the opening of the housing. 
     A method for manufacturing a camera module includes providing an image capture device, providing a housing, providing a lens unit, and providing a locking feature for temporarily fixing the lens unit with respect to the housing. The method further includes mounting the housing to the image capture device, mounting the lens unit to the housing, rotating the lens unit to engage a first portion of the locking feature with a second portion of the locking feature, and then performing an additional manufacturing process on the camera module. The method further includes rotating the lens unit to disengage the first portion of the locking feature from the second portion of the locking feature, focusing the lens unit, and, finally, permanently fixing the lens unit with respect to the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the following drawings, wherein like reference numbers denote substantially similar elements: 
         FIG. 1  is a perspective view of a camera module according to one embodiment of the present invention; 
         FIG. 2  is a partially exploded perspective view of the camera module of  FIG. 1 ; 
         FIG. 3   a  is a top view of the camera module of  FIG. 1  in an unlocked position; 
         FIG. 3   b  is a top view of the camera module of  FIG. 1  in a locked position; 
         FIG. 4  is a perspective view of the lens unit of  FIG. 1  shown in greater detail; 
         FIG. 5  is a cross-sectioned perspective view of the housing of  FIG. 1  shown in greater detail; 
         FIG. 6   a  is a cross-sectioned side view of the camera module of  FIG. 1  in an unfocused position; 
         FIG. 6   b  is a cross-sectioned side view of the camera module of  FIG. 1  in a focused position; 
         FIG. 7  is a side view of the camera module of  FIG. 1  showing the relationship between the lens unit and the housing. 
         FIG. 8  is a flow chart summarizing a method for manufacturing a camera module. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention overcomes the problems associated with the prior art by providing a digital camera module including a contaminant trap for isolating contaminants before they can collect on imaging components and degrade the quality of images captured. In the following description, numerous specific details are set forth (e.g., particular examples of focus devices, substrate types, attachment devices, etc.) in order to provide a thorough understanding of the invention. Those skilled in the art will recognize, however, that the invention may be practiced apart from these specific details. In other instances, details of well known camera module manufacturing practices (e.g., automated focus processes, materials selection, molding processes, etc.) and components (e.g., electronic circuitry, device interfaces, etc.) have been omitted, so as not to unnecessarily obscure the present invention. 
       FIG. 1  is a perspective view of a camera module  100  according to one embodiment of the present invention. Camera module  100  is shown mounted on a portion of a printed circuit board (PCB)  102  that represents a PCB of a camera hosting device. Camera module  100  communicates electronically with other components of the hosting device via a plurality of conductive traces  104 . Device  106  represents an electronic component (e.g., passive device, etc.) that may be mounted directly on PCB  102 . Those skilled in the art will recognize that the particular design of PCB  102  will depend on the particular application, and is not particularly relevant to the present invention. Therefore, PCB  102 , traces  104 , and device  106  are representational in character only. 
     Camera module  100  includes an image capture device  108  (not visible in the view of  FIG. 1 ), a circuit substrate  110 , a housing  112 , and a lens unit  114 . Circuit substrate  110  is mounted to one end (e.g., the bottom) of housing  112  and lens unit  114  is mounted to the other end (e.g., the top) of housing  112 . Image capture device  108  ( FIG. 2 ) is mounted on the top surface of circuit substrate  110 , so as to position image capture device  108  between substrate  110  and housing  112 . 
       FIG. 2  is a partially exploded view of camera module  100 , showing some additional details not visible in the view of  FIG. 1 . Note that the components of camera module  100  are aligned along an optical axis  200 . In particular, lens unit  114  and housing  112  are coaxial with respect to optical axis  200 . Additionally, image capture device  108  includes an image capture surface  202  that is perpendicular to and centered with respect to optical axis  200 . Proper optical alignment of lens unit  114  with respect to image capture device  108  facilitates proper focusing of images onto image capture surface  202 . 
     Image capture surface  202  provides a substantially flat planar surface whereon images are focused and converted into electrical data that is processed by the processing circuitry of image capture device  108  and/or the host device. Data communication between image capture device  108  and substrate  110  can be achieved by any suitable means known to those skilled in the art. For example, image capture device  108  can include a set of contact pads electrically coupled to a complementary set of contact pads of substrate  110  via wire bonding, soldering, or the like. Alternatively, camera module  100  can be assembled without a substrate by coupling image capture device  108  directly to housing  112  and including a means of electrically connecting image capture device  108  directly to PCB  102 . 
     Housing  112  includes a mounting portion  204  and a receiver portion  206 . Mounting portion  204  is adapted to mount to substrate  110  so as to enclose image capture device  108  (at least image capture surface  202 ) between substrate  110  and housing  112 . Receiver portion  206  includes an opening  208  that receives lens unit  114 . Opening  208  is defined by an inner surface  210  of housing  112 . Receiver portion  206  further includes a set of ramps  212  that engage a complementary set of ramps  214  formed on lens unit  114 . Ramps  212  are engaged by complementary ramps  214  so as to facilitate the focusing of camera module  100 . In particular, rotating lens unit  114  in a counter-clockwise direction raises lens unit  114  with respect to housing  112 , thereby increasing the distance between lens unit  114  and image capture surface  202 . Conversely, rotating lens unit  114  in a clockwise direction lowers lens unit  114  with respect to housing  112 , thereby decreasing the distance between lens unit  114  and image capture surface  202 . Thus, an image focused by lens unit  114  can be properly adjusted to lie in the focal plane of image capture surface  202 . After lens unit  114  is positioned correctly, lens unit  114  is fixed with respect to housing  112  by some suitable means (e.g., adhesive, thermal weld, etc.). 
     Before camera module  100  is fixed in a focused position, lens unit  114  can be temporarily locked into a fixed position via a locking feature  216  that prevents lens unit  114  from moving with respect to housing  112 . Temporarily fixing lens unit  114  to housing  112  with locking feature  216  prevents lens unit  114  from falling out of housing  112  before lens unit  114  is focused and fixed with respect to housing  112 . Locking feature  216  is, therefore, particularly useful when there are one or more processing steps between the insertion of lens unit  114  into housing  112  and the focus/fixation step. For example, during manufacturing, several camera modules can be made at one time, sometimes on a single unitary substrate, which is later separated to form the individual camera modules. If this processing occurs before focusing and fixation, then locking feature  216  will advantageously keep lens unit  114  securely seated in housing  112 . 
     Locking feature  216  includes a set of ribs  218  and a complementary set of rib receivers  220  formed on lens unit  114  and housing  112 , respectively. Ribs  218  are vertical protrusions extending parallel to optical axis  200  and formed on an outer surface  222  of lens unit  114 . Each one of receivers  220  includes a sloped surface  224  and a seat  226 . Sloped surfaces  224  enable ribs  218  to smoothly slide between inner surface  210  and seat  226  so as to facilitate the temporary locking of locking feature  216 . Details of locking feature  216  will be more thoroughly described with reference to  FIG. 3   a  and  FIG. 3   b.    
       FIG. 3   a  is a top view of camera module  100  in an unlocked position. Note that the top portion of lens unit  114  (including ramps  214 ) is cut away in  FIGS. 3   a  and  3   b  to provide a clear view of the relationship between inner surface  210  of housing  112  and outer surface  222  of lens unit  114 . In the unlocked position, lens unit  114  is rotatable within housing  112  such that ribs  218  slidably contact inner surface  210  of housing  112 . In addition to facilitating the locking of camera module  100 , ribs  218  also help maintain the coaxial relationship between lens unit  114  and housing  112  and limit tilting of lens unit  114  with respect to housing  112 . Ribs  218  are evenly spaced about outer surface  222  of lens unit  114  so as to evenly engage inner surface  210  of housing  112 . In particular, in this example embodiment, three ribs  218  are evenly spaced approximately 120 degrees about optical axis  200 . 
       FIG. 3   b  is a top view of camera module  100  in a locked position. During the locking of camera module  100 , lens unit  114  is rotated counter clockwise about optical axis  200  thereby sliding ribs  218  across inner surface  210 . As lens unit  114  is rotated further, ribs  218  slide from inner surface  210  to sloped surfaces  224  and onto seats  226 . Note that the distance between seats  226  and optical axis  200  is slightly less than the distance between the outer most surface of ribs  218  and optical axis  200  such that housing  112  provides a compressive force to lens unit  114 . This compressive force is sufficient to enable lens unit  114  to be temporarily press-fitted into housing  112 . Once press fitted, lens unit  114  is temporarily fixed to housing  112  so as to facilitate additional manufacturing processes to camera module  100  before the focusing process. Lens unit  114  can be disengaged from housing  112  by rotating lens unit  114  about optical axis  200  (clockwise) until ribs  218  disengage seats  226  and engage inner surface  210  of housing  112  again. 
       FIG. 4  shows a perspective view of lens unit  114  to include a flange  400  and a body  402 . Flange  400  includes previously described ramps  214  and provides a surface for a user and/or machine (e.g., automatic focusing machines) to engage during the focusing or locking/unlocking of camera module  100 . Flange  400  further includes a channel  404  that facilitates the fixation of lens unit  114  to housing  112  by providing a space for holding an adhesive or the like. The functionality of channel  404  will be further described later with reference to  FIG. 7 . 
     Body  402  includes a first perimeter  406 , a second perimeter  408 , and a third perimeter  410 . First perimeter  406  is defined by a cylindrical outer surface  412  extending parallel to optical axis  200 . Likewise, second perimeter  408  is defined by a cylindrical outer surface  414  extending parallel to optical axis  200 . Third perimeter  408  is also defined by a cylindrical outer surface  416  extending parallel to optical axis  200 . Note that the diameter of perimeter  406  is less than the diameter of perimeter  408 , and the diameter of perimeter  408  is less than the diameter of perimeter  410 . Surfaces  412  and  414  are joined by an intermediate surface  418 . Likewise, surfaces  414  and  416  are joined by a second intermediate surface  420 . 
       FIG. 5  is a perspective cross-sectional view of housing  112  showing additional features not visible in previously described figures. As shown, opening  208  has a first perimeter  500 , a second perimeter  502 , a third perimeter  504 , and a fourth perimeter  506 . First perimeter  500  is defined by a cylindrical inner surface  508  that is contoured to slidably contact outer surface  412  of lens unit  114  ( FIG. 4 ). Second perimeter  502  is defined by a cylindrical inner surface  510  that is contoured to slidably contact outer surface  414  of lens unit  114 . Third perimeter  504  is defined by a cylindrical inner surface  512  which is contoured to slidably contact outer surface  416  of lens unit  114 . Fourth perimeter  506  is defined by an inner surface  514  for slidably engaging ribs  218 . Inner cylindrical surface  508  and inner cylindrical surface  510  are joined by a first contaminant collecting surface  516 . Similarly, inner cylindrical surfaces  510  and  512  are joined by a second contaminant collecting surface  518 , and inner cylindrical surfaces  512  and  514  are joined by a third contaminant collecting surface  520 . 
       FIG. 6   a  shows a cross-sectional view of camera module  100  in an unfocused, locked position. In this particular embodiment, camera module  100  defines a first contaminant trap  600 , a second contaminant trap  602 , and a third contaminant trap  604 . First contaminant trap  600  is an isolated annular space defined by outer surface  412  of lens unit  114 , intermediate surface  418  of lens unit  114 , inner surface  510  of housing  112 , and contaminant collecting surface  516  of housing  112 . As shown, contaminant collecting surface  516  of housing  112  defines a rounded channel for collecting and holding any contaminants (e.g., particulate debris, glue, etc.) that enter contaminant trap  600 . Second contaminant trap  602  is an isolated annular space defined by outer surface  414  of lens unit  114 , intermediate surface  420  of lens unit  114 , inner surface  512  of housing  112 , and contaminant collecting surface  518  of housing  112 . Contaminant collecting surface  518  is a flat surface for collecting contaminants that enter contaminant trap  602 . Third contaminant trap  604  is an isolated annular space defined by outer surface  416  of lens unit  114 , flange  400  of lens unit  114 , inner surface  514  of housing  112 , and contaminant collecting surface  520  of housing  112 . Contaminant collecting surface  520  also defines a flat surface for collecting contaminants. 
       FIG. 6   b  shows a cross-sectioned view of camera module  100  in an unlocked, focused position. Note that lens unit  114  is relatively higher with respect to housing  112  than in  FIG. 6   a . Nevertheless, first outer surface  412  of lens unit  114  remains in contact with first inner surface  508 . Likewise, second outer surface  414  of lens unit  114  remains in contact with second inner surface  510 , and third outer surface  416  remains in contact with third inner surface  512 . As a result, the volumes of contaminant traps  600 ,  602 , and  604  all increase as the distance between lens unit  114  and image capture device  108  increases. Further, as the volumes are changed, contaminant traps  600  and  602  remain closed, so as to prevent any contaminants from escaping further into camera module  100 . 
     In summary, in the unlocked, focused position (raised), the lens unit  114  and the housing  112  are relatively positioned as follows. First outer surface  412  is simultaneously disposed within first inner surface  508  and second inner surface  510 . In addition, second outer surface  414  is simultaneously disposed within second inner surface  510  and third inner surface  512 , and the third outer surface  416  is simultaneously disposed within the third inner surface  512  and inner surface  514 . In this manner, particle traps  600 ,  602 , and  604  are formed between lens unit  114  and housing  112 . For example, particle trap  604  would be effective to catch excess adhesive used to fix lens unit  114  to housing  112 . 
       FIG. 7  is a side view of camera module  100  showing the relationship between channel  404  of lens unit  114  and ramps  212  of housing  112 . Channel  404  and ramps  212  form a recess for receiving an adhesive (not shown) which fixes lens unit  114  to housing  112 . During the focusing process, lens unit  114  is rotated about optical axis  200  until it is in proper focus. Then, an adhesive is applied within channel  404 . Channel  404  provides a small reservoir for the adhesive, which reduces the probability of the adhesive spreading into unwanted areas. The adhesive fuses channel  404  to one or more of ramps  212 , thereby immobilizing lens unit  114  with respect to housing  112 . It should be understood that lens unit  114  can be fixed in position with respect to housing  112  by any suitable alternative means (e.g., a thermal weld, fastener, etc.). 
       FIG. 8  is a flow chart summarizing a method  800  for manufacturing a camera module. In a first step  802 , an image capture device is provided. Next, in a second step  804 , a housing is provided. Then, in a third step  806 , a lens unit is provided. Next, in a fourth step  808 , the housing is mounted to the image capture device. Then in a fifth step  810 , the lens unit is mounted to the housing to form a camera module. Next, in a sixth step  812 , the lens unit is rotated to engage a locking feature on the lens unit with a complementary locking feature on the housing. Then, in a seventh step  814 , an additional manufacturing process is performed on the camera module. Next, in an eighth step  816 , the lens unit is rotated to disengage the locking feature on the lens unit from the complementary locking feature on the housing. Then, in a ninth step  818 , the lens unit is focused. Finally, in a tenth step  820 , the lens unit is fixed with respect to the housing. 
     The description of particular embodiments of the present invention is now complete. Many of the described features may be substituted, altered or omitted without departing from the scope of the invention. For example, alternate focus mechanisms may be substituted for those described above. Such focus mechanisms can include complementary thread sets in conjunction with the particle traps described herein. As another example, alternate methods may be used for mounting the circuit substrate to the housing. As yet another example, alternate types (e.g., socket, edge connector, etc.) and locations (e.g., side contacts, etc.) of electrical connections between circuit substrate  110  and PCB  102 . As yet another example, alternate means for fixing the lens unit with respect to the housing can be used. These and other deviations from the particular embodiments shown will be apparent to those skilled in the art, particularly in view of the foregoing disclosure.