Abstract:
A PCB-mountable lens adapter includes an adapter lens for being a component of an imaging system that has a second field of view different from the first field of view, the imaging system comprising the adapter lens and the camera lens; and an adapter housing for holding the adapter lens and for attaching to a PCB. A method for modifying the field of view of an camera module includes attaching a PCB-mountable lens adapter to a PCB, the PCB-mountable lens adapter including an adapter lens mounted in an adapter housing, the PCB being configured for surface-mounting of the camera module thereto.

Description:
BACKGROUND 
     Digital cameras are used in a variety of consumer, industrial and scientific imaging devices to produce still images and/or video. Such digital cameras are for example implemented in webcams and mobile telephones and include a camera module such as a reflowable camera module (RCM) attached to a printed circuit board (PCB). The field of view (FOV) of an RCM is typically between 60 degrees and 70 degrees. The FOV can be increased by attaching an adapter lens in front of the camera module. The resulting imaging system (adapter lens plus camera module) has a wider FOV than the camera module alone. A wide FOV is valuable in applications such as autonomous vehicle navigation, car parking monitor systems, and gesture recognition. 
     An adapter lens that provides an ultra-wide field of view, e.g., 180°, is called a fisheye adapter lens or fisheye conversion lens. Existing fisheye adapter lenses removably attach to the outside of a digital camera. In one example a clip is used to attach the fisheye adapter lens to the digital camera so that it aligns with the camera module. In another example, a case encloses a mobile device (e.g., a cell phone) that includes an internal camera module and holds the fisheye adapter lens adjacent to the internal camera module. 
     SUMMARY OF THE INVENTION 
     According to one embodiment, a PCB-mountable lens adapter for a device that includes a camera module having a camera lens with a first field of view is provided. The PCB-mountable lens adapter includes an adapter lens for being a component of an imaging system that has a second field of view different from the first field of view, the imaging system comprising the adapter lens and the camera lens; and an adapter housing for holding the adapter lens and for attaching to a printed circuit board (PCB). 
     According to another aspect, a method for modifying the field of view of a camera module is provided. The method includes attaching a PCB-mountable lens adapter to a PCB, the PCB-mountable lens adapter including an adapter lens mounted in an adapter housing, the PCB being configured for surface-mounting of the camera module thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a prior-art vehicle equipped with a parking assist system with a printed circuit board (PCB), an image processor, and a display. 
         FIG. 2  is a cross-sectional view of the prior-art PCB of  FIG. 1 , which includes an RCM soldered to the PCB. 
         FIG. 3  shows further detail of the PCB shown in  FIG. 2 , with the addition of one PCB-mountable lens adapter mounted on the PCB and encircling the RCM, in an embodiment. 
         FIG. 4  is a plan view of a holder of the PCB-mountable lens adapter of  FIG. 3  mounted on the PCB and encircling the RCM. 
         FIG. 5  is a cross-sectional view of another PCB-mountable lens adapter mounted on the PCB of  FIG. 2  and encircling the RCM, in an embodiment. 
         FIG. 6  is a flowchart illustrating one method for modifying the field of view of an RCM, where the RCM is already bonded to a PCB, in an embodiment. 
         FIG. 7  is a flowchart illustrating another method for modifying the field of view of an RCM, where the RCM is not yet bonded to a PCB, in an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The prior-art adapter lenses discussed above are externally-attached: they attach to an external portion of the device containing a reflowable camera module (RCM). Such externally-attached adapter lenses have several drawbacks. First, they increase the device volume, which may reduce the device&#39;s value depending on its function and context of use. Second, the distance between the adapter lens and RCM can limit achievable image quality. And third, imprecise alignment of the adapter lens to the RCM lens can degrade image quality. 
     This disclosure relates to a PCB-mountable lens adapter for a camera module, such as a RCM. Although the description hereinbelow discusses RCMs, it should be appreciated that camera modules that are mountable to a PCB by means other than reflow soldering could be utilized without departing from the scope hereof. 
     Part or all of a PCB-mountable lens adapter as described herein is directly and permanently attached to the PCB that also attaches to the RCM. Compared to external attachment, such attachment adds less volume to the device and reduces the distance between the adapter lens and RCM which further eases constraints on image quality. Permanent attachment of the PCB-mountable lens adapter to the PCB also ensures accurate alignment of the adapter lens to the reflowable camera lens, and ensures that the accurate alignment remains constant. 
       FIG. 1  shows a prior-art vehicle  180  equipped with a parking assist system  160 . Parking assist system  160  includes a printed circuit board (PCB)  130 , an image processor  140 , and a display  150 . PCB  130  includes a RCM  120 . RCM  120  includes a camera lens  100  and an image sensor  116 . Camera lens  100  is for example a compound lens with a field-of-view (FOV)  113  substantially less than 180°. Image sensor  116  is for example implemented using complementary metal-oxide-semiconductor (CMOS) technology. 
     Camera lens  100  images an object in its FOV  113  onto image sensor  116 , which generates and sends raw image data  131  to image processor  140 . Image processor  140  transforms at least part of raw image data  131  into output view data  14  displayed on display  150 . 
       FIG. 2  is a cross-sectional view of a PCB  230 , which includes an RCM  220  mechanically and electrically connected thereto with solder bumps  225 . RCM  220  has RCM diameter  221  and includes camera lens  200 . Camera lens  200  has an entrance pupil  233 . 
     Camera lens  200  has an optical axis  223 . With respect to coordinate axes  298 , optical axis  223  is parallel to the z-axis and has radial position r=0. RCM  220  and PCB  230  f function as RCM  120  and PCB  130 , respectively, in parking assist system  160 . 
       FIG. 3  shows one PCB-mountable lens adapter  300  mounted on PCB  230  and encircling RCM  220 . PCB-mountable lens adapter  300  includes an adapter housing  304  and an adapter lens  303 . Adapter housing  304  includes a holder  301  and a lens barrel  302 . In  FIG. 3 , holder  301  is attached to PCB  230  and surrounds RCM  220 . Holder  301  may partially surround RCM  220  without departing from the scope herein. Holder  301  is sized and shaped so that holder  301  does not obstruct the field of view of RCM  220  when attached to PCB  230  (or RCM  220 ). 
     Holder  301  may be attached to PCB  230  via methods known in the art, such as by adhesive bonding and mechanical fastening. An intermediate part (not shown) may be between holder  301  and PCB  230  depending on design considerations and without departing from the scope hereof. The intermediate part may be a coupler that facilitates attachment of holder  301  to PCB  230 . 
     In an embodiment of PCB-mountable lens adapter  300 , lens barrel  302  is removably attached to holder  301 . In another embodiment of PCB-mountable lens adapter  300 , lens barrel  302  is permanently attached to holder  301 . 
     Unlike prior-art adapter lenses that attach to the outside of an imaging device, PCB-mountable lens adapter  300  is attached to PCB  130 , an interior component of the imaging device. PCB-mountable lens adapter  300  and RCM  220  are may independently attach to PCB  230  too. 
     In an embodiment of PCB-mountable lens adapter  300 , holder  301  attaches to one or both of RCM  220  and PCB  230 , which are for example interior components of parking assist system  160 . RCM  220  may attach to holder  301  before or after holder  301  is attached to PCB  230 . 
     Adapter lens  303  is for example a single-element lens, as depicted in  FIG. 3 . But adapter lens  303  may instead be a compound lens that includes multiple individual optical elements. 
     PCB-mountable lens adapter  300  mounts on PCB  230  such that adapter lens  303  and camera lens  200  are axially aligned (coaxial): adapter lens  303  has an optical axis  323  collinear with optical axis  223  of camera lens  200 . An exit pupil  333  of adapter lens  303  is located in the same plane as entrance pupil  233  of camera lens  200 . Exit pupil  333  and entrance pupil  233  are hence coplanar. 
     For purposes of clarity, when an entrance pupil of a first lens is coaxial with the exit pupil of second lens it means that the first and second lenses are coaxial. Hence, regarding PCB-mountable lens adapter  300  mounted on PCB  230 , entrance pupil  233  and exit pupil  333  are both coaxial and coplanar. 
     Adapter lens  303  has a lens surface  312  and holder  301  has a holder surface  314  separated from lens surface  312  by a distance  306 . If exit pupil  333  and entrance pupil  233  are coplanar, then distance  306  may be zero. 
     PCB-mountable lens adapter  300  may be designed such that camera lens  200  and adapter lens  303  collectively function as a macro lens, a zoom lens, a telephoto lens, a wide angle lens, or a fisheye lens. In one example of PCB-mountable lens adapter  300 , adapter lens  303  is a three-piece all-aspheric adapter fisheye lens system described in U.S. patent application Ser. No. 14/465,013 filed Aug. 21, 2014 and entitled “Three-piece all-aspheric adapter fisheye lens system.” In another example of PCB-mountable lens adapter  300 , adapter lens  303  is a four-piece all-aspheric adapter fisheye lens system described in U.S. patent application Ser. No. 14/465,146 filed Aug. 21, 2014 and entitled “Four-piece all-aspheric adapter fisheye lens system.” 
     Holder  301  has a first inner diameter  341  and a second inner diameter  342 . Inner diameter  341  is sized to be equal to or greater than RCM diameter  221  such that holder  301  may be disposed on PCB  230  and at least partially surround RCM  220 . Second inner diameter  342  is sized such that lens barrel  302  may be inserted into holder  301 . Holder  301  may be a machined or molded part and may be formed of a metal, such as aluminum or brass, or plastic. Holder  301  may be fabricated via other means and materials without departing from the scope herein. 
       FIG. 4  is a plan view of holder  301  mounted on PCB  230  and encircling RCM  220 . In an embodiment of holder  301 , first inner diameter  341  is larger than RCM diameter  221  such that PCB  230  is visible in the region between holder  301  and RCM  220 . In an embodiment of holder  301 , the first inner diameter  341  equals RCM diameter  221  such that holder  301  is in physical contact with RCM  220 . In this embodiment, holder  301  prevents electromagnetic interference from reaching RCM  220 . 
       FIG. 5  is a cross-sectional view of another PCB-mountable lens adapter  500  mounted on PCB  230  and encircling RCM  220 . Whereas PCB-mountable lens adapter  300  includes three parts, holder  301 , lens barrel  302 , and adapter lens  303 , PCB-mountable lens adapter  500  includes two parts: an adapter housing  504  and an adapter lens  503 . Adapter lens  503  is similar to adapter lens  303 ,  FIG. 3 . 
     In an embodiment of PCB-mountable lens adapter  500 , adapter housing  504  attaches to one or both of RCM  220  and PCB  230 . RCM  220  may be attached to adapter housing  504  before either RCM  220  or adapter housing  504  is attached to PCB  230 . 
     In  FIG. 5 , adapter housing  504  is shown attached to PCB  230  and holds adapter lens  503 , such that adapter housing  504  is attached to PCB  230  and surrounds RCM  220 . Adapter housing  504  may partially surround RCM  220  without departing from the scope herein. Adapter housing  504  is sized and shaped such when attached to PCB  230  (or RCM  220 ), holder  301  does not obstruct the FOV of RCM  220 . 
     Adapter housing  504  may be attached to PCB  230  via methods known in the art, such as adhesive bonding and mechanical fastening. An intermediate part may be disposed between adapter housing  504  and PCB  230  without departing from the scope hereof. 
     In an embodiment of PCB-mountable lens adapter  500 , adapter lens housing  504  has a holder region  501  and a lens barrel region  502 . Adapter housing  504  can be viewed as a fusion of holder  301  and lens barrel  302 , where holder region  501  functions as holder  301  and lens barrel region  502  functions as lens barrel  302 . 
     PCB-mountable lens adapter  500  mounts on PCB  230  such that adapter lens  503  and camera lens  200  are coaxial: adapter lens  503  has an optical axis  523  that is collinear with optical axis  223  of camera lens  200 . An exit pupil  533  of adapter lens  503  is located in the same plane as entrance pupil  233  of camera lens  200 ; thus exit pupil  533  and entrance pupil  233  are coplanar. 
     The distance between lens surface  512  and mount surface  514  is distance  506 . Distance  506  may be zero when exit pupil  533  and entrance pupil  233 , since lens surface  512  adjoins mount surface  514  directly. 
     Adapter housing  504  has a first inner diameter  541  and a second inner diameter  542 . Adapter housing  504  may be a machined part or molded part and may be formed of a metal, such as aluminum or brass, or of plastic. Adapter housing  504  may be fabricated via other means and of other materials without departing from the scope hereof. 
     In an embodiment of adapter housing  504 , first inner diameter  541  is larger than RCM diameter  221  such that a gap of width  507  is between adapter housing  504  and RCM  220 . In another embodiment of adapter housing  504 , the first inner diameter  541  equals RCM diameter  221 , such that width  507  equals zero and adapter housing  504  adjoins RCM  220 . When width  507  equals zero, adapter housing  504  acts to prevent electromagnetic interference from reaching RCM  220 . 
       FIG. 6  is a flowchart illustrating an exemplary method  600  for modifying the FOV of a RCM, where the RCM is bonded to a PCB and includes a camera lens. In optional step  602 , method  600  forms adapter housing for an adapter lens. The adapter housing is formed such that an exit pupil of the adapter lens and an entrance pupil of the camera lens are coplanar and coaxial. In an example of step  602 , method  600  forms adapter housing  504  for adapter lens  503  such that exit pupil  533  of adapter lens  503  and entrance pupil  233  of camera lens  200  are coplanar when (i) adapter lens  503  is mounted in adapter housing  504 , (ii) adapter housing  504  is bonded to PCB  230 , and (iii) RCM  220  is surface-mounted to PCB  230 . 
     In optional step  604 , method  600  mounts the adapter lens in the adapter housing, resulting in a PCB-mountable lens adapter. In an example of step  604 , method  600  mounts adapter lens  503  to adapter housing  504 . 
     In step  606 , method  600  aligns the adapter lens and the camera lens such that the adapter lens and camera lens are coaxial. In an example of step  606 , method  600  aligns adapter lens  503  and camera lens  200  such that adapter lens  503  and camera lens  200  are coaxial. 
     In step  610 , method  600  attaches the adapter housing to the PCB, the RCM surface-mounted thereto. In an example of step  610 , method  600  attaches adapter housing  504  to PCB  230 , RCM  220  being surface-mounted thereto 
       FIG. 7  is a flowchart illustrating an exemplary method  700  for modifying the field of view of an RCM, where the RCM is not yet bonded to a PCB. In optional step  702 , method  700  forms adapter housing. The adapter housing is formed such that an exit pupil of the adapter lens and an entrance pupil of the camera lens are coplanar and coaxial. In an example of step  702 , method  700  forms adapter housing  504  for adapter lens  503  such that exit pupil  533  of adapter lens  503  and entrance pupil  233  of camera lens  200  are coplanar when (i) adapter lens  503  is mounted in adapter housing  504 , (ii) adapter housing  504  is bonded to PCB  230 , and (iii) RCM  220  is surface-mounted to PCB  230 . 
     In optional step  704 , method  700  mounts the adapter lens in the adapter housing, resulting in a PCB-mountable lens adapter. In an example of step  704 , method  700  mounts adapter lens  503  in adapter housing  504 , resulting in PCB-mountable lens adapter  500 . 
     In step  706 , method  700  attaches the RCM to the adapter housing, such that the adapter lens and the camera lens are coaxial. In an example of step  706 , method  700  attaches RCM  220  to adapter housing  504 , such that adapter lens  503  and camera lens  200  are coaxial. 
     In step  708 , method  700  surface-mounts the RCM to the PCB. In an example of step  708 , method  700  surface-mounts RCM  220  to PCB  230 . 
     In step  710 , method  700  attaches the adapter housing to the PCB. In an example of step  710 , method  700  attaches adapter housing  504  to PCB  230 . 
     Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.