Abstract:
An image capture device and method of assembling same is disclosed which provides an improved technique of mounting a CMOS detector and also isolates the optics for image capture from the optics for illumination, thereby simplifying the adjustment process. An exemplary arrangement using the camera module is also shown.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to a camera module, and more specifically, to a camera module and a method of assembling same with particular advantageous use in the capture of two-dimensional bar codes and similar symbols.  
       BACKGROUND OF THE INVENTION  
       [0002]     Two-dimensional bar code symbol capture devices are known in the art. An example of such device is shown in U.S. Patent Publication No. 2003/0089776, a figure from which is reproduced as  FIG. 1  here.  
         [0003]     These image capture devices typically include a CMOS or other type of light sensor that comprises an array of sensing elements, each of which outputs an electrical signal proportional or in some way related to the amount of incident light. The image may then be stored electronically for later processing or reproduction.  
         [0004]     Such image capture devices typically include the sensor mounted on a printed circuit board (PCB) and placed behind a set of one or more lenses, as shown in the &#39;776 publication cited above, and in  FIG. 1  hereof. Additionally, the prior art image capture devices often include an illumination means, a set of several light sources to light up the symbol being imaged, and to help aim the image capture device at the symbol to be captured.  
         [0005]     The aiming light is used to help ascertain where to position the image capture device. By positioning the aiming light, often implemented as a series of LEDS, in the correct place, a user can ascertain when the image capture device is correctly positioned to be activated for capturing the desired image.  
         [0006]     Several problems exist with these prior art devices. First, any lenses associated with the illumination LEDs must be correctly adjusted to properly illuminate the symbol or image to be captured. Specifically, the distance between the lens and the illumination and aiming LEDs must be correctly set.  
         [0007]     However, the additional lens or lenses employed to direct light reflected from the image onto the sensor must also be adjusted, so that the distance between these additional lenses and the sensor are also correct. Because these two adjustments are related in a rather complicated and nonlinear fashion, it is very difficult to properly adjust focal lengths in an arrangement such as that shown in the &#39;776 publication.  
         [0008]     Another problem in such systems results from the type of sensor array utilized. More specifically, these types of sensor arrays may be packaged in several different types of packages, such as bare chip mount, ceramic packaging, or what has commonly become known as BGA or ball grid array packaging. Ball grid array packaging is a type of shell case packaging known in the art and which permits the size of the package to be minimized.  
         [0009]     In the conventional image capture devices, BGA type of packaging is rarely if ever employed. One of the problems with BGA type packaging is that when mounted on a PCB for use in the camera module, stray light from the opposite side of the PCB reaches the BGA packaged sensor array, and causes distortion of the image. However, BGA type of packaging is beneficial for making the camera module as small as possible. Therefore, there are competing requirements when this type of packaging is employed.  
         [0010]     In view of the foregoing, there exists a need in the art for a more efficient image capture device utilizing BGA type sensors.  
       SUMMARY OF THE INVENTION  
       [0011]     The above and other problems of the prior art are overcome, and a technical advance is achieved in accordance with the present invention which relates to a novel assembly method for such image capture devices, and the resulting device. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  shows a prior art two-dimensional image capture device;  
         [0013]      FIG. 2  shows an exemplary embodiment of a two-dimensional image capture device in accordance with the present invention, depicting also an exemplary assembly process therefore;  
         [0014]      FIG. 3  depicts another exemplary embodiment showing the sensor mounted on a PCB,  
         [0015]      FIG. 4  shows an close up side view of a lens stopper in accordance with the present invention,  
         [0016]      FIG. 5  depicts two different camera modules side by side; and  
         [0017]      FIG. 6  depicts an additional view of the cameras of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     FIGS.  2 A-E show an assembly process for the image capture device in accordance with the present invention. In accordance with one advantageous aspect of the invention, the assembly and adjustment of the aiming and illumination portion of the image capture device  216  is kept separate from that of the camera portion. This separation eliminates the difficulties caused by the trying to adjust all the lenses correctly when each adjustment affects the others.  
         [0019]     Turning to  FIG. 2A , shown therein are an LED PCB tool  1 , which is a circuit board that includes at least a set of illumination LEDs  202  and a set of aiming LEDs  203 . The aiming LEDs  203  serve to “frame out” or otherwise designate the area to be imaged, so that a user can ascertain when the image capture device is properly positioned for activation. The illumination LEDs  202  provide the light to be reflected by the image for capture.  
         [0020]     The assembly process begins by combining the LED PCB  201  with a body  204  and mask lens element  206 . As indicated therein, the mask lens includes one or more lenses  205  that are lined with the illumination LEDs  202 , and one or more lenses  207  that are aligned with the aiming LEDs  203 . As shown in  FIG. 2B , the resulting assembled device is an illumination element  210 , which includes the LEDs and lenses for aiming and illuminating the symbol to be read. Whatever adjustments need to be made in terms of the distances between any of the illumination or aiming LEDs and the lenses can be made entirely independently of anything to do with the lens that is used for image capture of the reflected light, to be explained below.  
         [0021]     Turning to  FIG. 2C , the figure includes a body  212  for mounting a lens  211 . The lens  211  is utilized to capture and focus light returned from the image to be captured onto a detector  213 , shown as CMOS mounted on a capturing PCB  213 . It is understood that the invention is not limited to CMOS detectors, and any type of such detectors may be employed such as Charge Coupled Devices (CCD), etc.  
         [0022]     Unlike the LED PCB  201 , the capturing PCB  213  preferably does not have a hole in the middle thereof, as the hole  220  in the middle of PCB  201  is to allow the lens  211  to be assembled, as explained further below. The capturing PCB may have other electronic components such as gates, interface logic, connectors, etc. installed on a side opposite to that of sensor  213 .  
         [0023]     The final step in the process involves connecting the illumination element  210  with the camera module  215  shown in  FIG. 2D , thereby connecting together the portions shown in  FIGS. 2B and 2D .  
         [0024]     Notably, however, the camera module  215  can be adjusted by moving the lens  211  to any desired distance without at all affecting focal points, distances, or other parameters associated with the aiming and illumination LED shown and described with respect to  FIGS. 2A and 2B . Accordingly, all of the design parameters and adjustments can be done independently, thereby leading to a more streamlined and efficient assembly process. Any known mechanism for moving lens  211  in and out of body  212  for adjustment purposes may be utilized, such as a slide fit with a lock screw, or a screw fit, etc.  
         [0025]     Turning to the sensor PCB  214 , a preferred manner of mounting the sensor on the PCB  214  is shown in  FIG. 3 . As indicated therein, the sensor  213  is placed on the PCB and a connector  315  for bringing signals to the remainder of the system is placed over the same area, on the opposite side of the PCB. Importantly, the connector is placed over the through holes in the PCB  214 , in order to cut down and/or prevent light from leaking through the holes and distorting the image on sensor  213 . As explained previously, this is particularly important in embodiments where the sensor  213  is packaged using BGA technology, as previously discussed.  
         [0026]     Also as noted on  FIG. 3 , the connector may be replaced with any type of blocking mechanism such as tape, or an opaque material in order to prevent the light from passing. However, if the connector is utilized for the system anyway, then it simply can serve two purposes, and avoid an extra element utilized merely to block the light.  
         [0027]      FIG. 4  shows an additional embodiment in which a lens stopper is built in to a portion of body  212  in order to provide a starting point for the adjustment of the lens. Also shown in  FIG. 4  is the CMOS  213 .  
         [0028]     It is also noted that rather than blocking light through the PCB through holes via a connector or other opaque material, walls surrounding the CMOS may be utilized instead. However, this technique is less preferred as it may increase cost of the device.  
         [0029]     It has also been determined that it is preferable to mount the CMOS or other sensor on the capturing PCB after all elements on the other side of the capturing PCB  214  have been mounted. This avoids heat damage to the CMOS sensor that would otherwise occur when parts are mounted on the other side of the sensor PCB which may require heat and or soldering.  
         [0030]     In accordance with another preferred embodiment to the invention,  FIGS. 5 and 6  depict plural cameras with different focal lens that are mounted together in order to achieve a larger focal area. These cameras may be of the same or a different type than that described herein, but are preferably of the same type.  
         [0031]     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.