Abstract:
A camera module having a liquid crystal shutter that controls the time period during which the image sensor is exposed to light directed into the camera module. The shutter is located within the camera module housing, which may include EMI shielding and may include a lens actuator for moving a movable lens group. The shutter may be located before or after the movable lens group and before or after a fixed lens group that may also be included. The camera module may also include an IR filter for reducing the amount of IR light that reaches the image sensor.

Description:
CROSS REFERENCE  
       [0001]    This application is the nonprovisional of U.S. Provisional Pat. Appl. No. 61/446,151, filed Feb. 24, 2011, entitled “AUTOFOCUS-ZOOM CAMERA MODULE INTEGRATING LIQUID CRYSTAL DEVICE AS HIGH SPEED SHUTTER,” which is hereby incorporated by reference into this application. 
     
    
     BACKGROUND  
       [0002]    Digital camera modules are currently being incorporated into a variety of host devices such as, for example, cellular telephones, personal data assistants (PDAs), computers, etc. Such host devices are becoming increasingly more compact and, therefore, permitting less and less space for camera module form factors. Accordingly, host device manufacturers prefer digital camera modules to be small, so that they can be incorporated into the host device without increasing the overall size of the host device. Of course, host device manufacturers also prefer camera modules that capture images of the highest possible quality. Therefore, the goal in designing and manufacturing camera modules is to minimize size, maximize performance (i.e. image quality, and simplify the overall manufacturing process. 
         [0003]    It is against this background that the camera module disclosed herein has been developed. 
       SUMMARY   
       [0004]    The disclosed camera module overcomes the issues associated with the prior art by combining a liquid crystal shutter. A camera module that is attached to and is a component in a mobile electronic device includes: an image sensor; a housing having an internal cavity within which the image sensor is located, the housing further having an opening at one end thereof to allow ambient light to pass into the housing; and a liquid crystal shutter positioned in the housing between the opening and the image sensor, to selectably either allow light to pass therethrough or block light from passing therethrough. 
         [0005]    The camera module may further include a lens positioned in the housing between the opening and the image sensor. The lens may include a fixed lens group. The lens may further include a movable lens group and the camera module may further include an actuator to selectably move the movable lens group. The shutter may be positioned between the fixed lens group and the movable lens group. The shutter may be positioned between the opening and the movable lens group. The shutter may be positioned between the movable lens group and the image sensor. The shutter may be attached directly to the image sensor. The attachment may be made via glass-on-die (GOD) technology. The actuator may be formed as a housing located inside of the first housing. 
         [0006]    The camera module may further include a circuit substrate to which the housing is attached, the substrate having a top side to which the image sensor is attached and a bottom side on which a plurality of electrical contact pads are provided for electrical connection of the image sensor and the shutter to circuitry external to the camera module. The housing may include a shield for reducing electromagnetic interference in the interior of the cavity from electromagnetic signals outside of the housing. 
         [0007]    A camera module that is attached to and is a component in a mobile electronic device, including: an image sensor; a housing having an internal cavity within which the image sensor is located, the housing further having an opening at one end thereof to allow ambient light to pass into the housing; a lens positioned in the housing between the opening and the image sensor, wherein the lens further includes a movable lens group; an actuator to selectably move the movable lens group; and a liquid crystal shutter positioned in the housing between the opening and the image sensor, to selectably either allow light to pass therethrough or block light from passing therethrough. 
         [0008]    The lens may further include a fixed lens group. The shutter may be positioned between the fixed lens group and the movable lens group. The shutter may be positioned between the opening and the movable lens group. The shutter may be positioned between the movable lens group and the image sensor. The shutter may be attached directly to the image sensor. The attachment may be made via glass-on-die (GOD) technology. The actuator may be formed as a housing located inside of the first housing. The camera module may further include a circuit substrate to which the housing is attached, the substrate having a top side to which the image sensor is attached and a bottom side on which a plurality of electrical contact pads are provided for electrical connection of the image sensor and the shutter to circuitry external to the camera module. The housing may include a shield for reducing electromagnetic interference in the interior of the cavity from electromagnetic signals outside of the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a exploded perspective view of a camera module. 
           [0010]      FIG. 2  is a top perspective view of the camera module of  FIG. 1 . 
           [0011]      FIG. 3  is a bottom perspective view of the camera module of  FIG. 1 . 
           [0012]      FIG. 4  is a cross-sectional view of the camera module of  FIG. 1   
           [0013]      FIG. 5  is a schematic view of an alternative embodiment of a camera module. 
           [0014]      FIG. 6  is a schematic view of a second alternative embodiment of a camera module. 
           [0015]      FIG. 7  is a schematic view of a third alternative embodiment of a camera module. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    While the embodiments of the present invention are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that it is not intended to limit the invention to the particular form disclosed, but rather, the invention is to cover all modifications, equivalents, and alternatives of embodiments of the invention as defined by the claims. The present invention is described with reference to the drawings, wherein like reference numbers denote substantially similar elements: 
         [0017]      FIG. 1  shows a perspective view of a camera module  100  according to one embodiment of the present invention. The camera module  100  includes a circuit substrate  102 , a plurality of electrical components  104 , an image sensor  106 , an infrared (IR) filter  108 , an actuator system  110 , a lens system  112 , a liquid crystal shutter device  114 , and an actuator housing which acts as an electromagnetic interference shield  116 . As shown, the camera module  100  is exploded along a Z-axis that is coaxially aligned with the optical center of the lens system  112  and perpendicularly centered with respect to a planar image sensor surface  118  of the image sensor  106 . 
         [0018]    The circuit substrate  102  includes electrical circuitry that facilitates electrical communication between the camera module  100  and a hosting device such as a mobile electronic device (e.g., a mobile phone). 
         [0019]    Electrical components  104  (e.g., resistors, capacitors, IC chips, electrical connectors, terminals, processors, memory storage device, etc.) are mounted on the top surface of the circuit substrate  102  and electrically connected to the circuitry formed thereon. More specifically, the electrical components  104  are mounted on the circuit substrate via surface mount technology (SMT). 
         [0020]    The image sensor  106  is also mounted on the top surface of the circuit substrate  102  and electrically connected to the circuitry formed thereon. The image sensor surface  118  of the image sensor  106  is operative to convert light, focused thereon via the lens system  112 , into image data. 
         [0021]    The IR filter  108  is mounted in the actuator system  110  so as to filter infrared radiation out of the light focused onto the image sensor surface  118  by the lens system  112 . The IR filter  108  also prevents debris from accumulating on the image sensor surface  118 . Alternatively, an IR filter could be incorporated into the lens system  112  and the IR filter  108  could be substituted by a non-filtering substrate that protects the image sensor surface  118  from debris. 
         [0022]    The actuator system  110  is, for example, an autofocus/zoom actuator system that includes a bottom portion  120  and an opposite top portion  122 . The bottom portion  120  is adapted to receive the IR filter  108  and is mounted on the top surface of the circuit substrate  102 , over the electrical components  104  and the image sensor  106 . The top portion  122  is adapted to receive the lens system  112 . In this particular embodiment, the actuator system  110  includes a voice coil motor (VCM) for driving the lens system  112  along the Z-axis during autofocus/zoom operations. 
         [0023]    The lens system  112  is a VCM driven lens barrel that houses a lens assembly (not visible) and is movably coupled to the top portion  122  of the actuator system  110 . Further, the lens system  112  is responsible to move along the Z-axis when actuated by the actuator system  104  during autofocus/zoom operations. 
         [0024]    The liquid crystal shutter device  114  is optically aligned with, and positioned between, the lens system  112  and the electromagnetic interference shield  116 . The liquid crystal shutter device  114  is operative to control the passage of light into the camera module  100  via liquid crystal display technology wherein the amount of light that passes through the liquid crystal shutter device  114  is voltage dependent. The amount of light passing through a liquid crystal panel can be controlled with extremely high precision and speed. Accordingly, the passage of light through the liquid crystal shutter device  114  and, therefore, into the camera module  100  can be controlled with extremely high precision and speed. Indeed, the liquid crystal shutter device  114  contributes significantly to the overall performance of the camera module  100 . For example, the liquid crystal shutter device  114  can change from opaque to transparent (one half cycle) at frequencies greater and 200 Hz such that extremely high shutter speeds can be achieved. Not only can the liquid crystal shutter device  114  achieve high shutter speeds, but also very low shutter speeds and any intermediate speeds therebetween. As another example, the exposure time can be controlled with extremely high precision such that the image quality of the camera module  100  can be maximized by exposing the image sensor  106  to the correct amount of light for given lighting conditions. 
         [0025]    In addition to excellent performance, the liquid crystal shutter device  114  is extremely reliable, thin, and energy efficient. For example, the liquid crystal shutter device  114  is non-mechanical and, therefore, has a useful operating life that is not limited by the number of operating cycles. In other words, it does not wear out and, therefore, has a higher reliability than mechanical shutter devices, which often fail after less than 100,000 cycles. As another example, the liquid crystal shutter device  114  is thinner than 0.5 mm and, therefore, has minimal affect on the overall Z-height of the camera module  100 . As another example, the liquid crystal shutter device  114  operates on very little low driver current (e.g., 15-30 mA) and, therefore, consumes only a small amount of host device power. The liquid crystal shutter device  114  will typically be one without a polarizer. It may have light transmission in the open state of approximately 95% or greater. 
         [0026]    The EMI shield  116  is mounted over the actuator system  110 , the lens system  112 , and the liquid crystal shutter device  114 . The EMI shield  116  may include a solid enclosure (or a cage) made of electrically conductive or magnetic materials. It serves to greatly reduce the amount of electromagnetic (particularly RF) energy that passes from outside the shield  116  to the interior of the camera module  100 . It could also include a plastic housing coated with a metallic substance, such as a metallic ink. Other possible functions of the EMI shield  116  may be to prevent or reduce light leakage into the camera module  100  and to prevent or reduce the intrusion of foreign contaminants into the camera module  100 . 
         [0027]      FIG. 2  shows a top perspective view of the camera module  100  assembly. As shown, the camera module  100  includes a set of voice coil motor terminals  200  and a set of liquid crystal shutter device terminals  202 . 
         [0028]      FIG. 3  shows a bottom perspective view of the camera module  100  assembled. As shown, the circuit substrate  102  includes a bottom surface wherein a set of electrical contact pads  300  is formed. Electrical contact pads  300  provide a means for electrically connecting the camera module  100  to host device circuitry. 
         [0029]      FIG. 4  shows a cross-sectional view of the camera module  100  assembly. 
         [0030]      FIG. 5  illustrates a camera module  500  accordingly to an alternative embodiment. The camera module  500  includes a circuit substrate  502 , an image sensor  504 , an actuator system  506 , a fixed lens group  508 , a liquid crystal shutter device  510 , and a movable lens group  512 . The image sensor  504  is fixably mounted on the circuit substrate  502 , the actuator system  506  is fixably mounted on the circuit substrate  502 , the fixed lens group  508  is fixably mounted in the actuator system  506 , the liquid crystal shutter device  510  is fixably mounted in the actuator system  510  between the fixed lens group  508  and the movable lens group  512 , and the movable lens group  512  is movably coupled to the actuator system  506  so as to facilitate autofocus/zoom operations by moving along the Z-axis when actuated by the actuator system  506 . 
         [0031]      FIG. 6  illustrates a camera module  600  accordingly to another alternative embodiment. The camera module  600  includes a circuit substrate  602 , an image sensor  604 , a liquid crystal shutter device  606 , an IR filter  608 , a holder/frame  610  an actuator system  612 , and a movable lens group  614 . The image sensor  604  is fixably mounted on the circuit substrate  602 , the liquid crystal shutter device  606  and the IR filter  608  are fixably mounted on opposite sides of the holder/frame  610 , the holder/frame  610  is fixably mounted on the circuit substrate  602 , the actuator system  612  is fixably mounted on the holder/frame  610 , and the movable lens group  614  is movably coupled to the actuator system  612  so as to facilitate autofocus/zoom operations by moving along the Z-axis when actuated by the actuator system  612 . 
         [0032]      FIG. 7  illustrates a camera module  700  accordingly to yet another alternative embodiment. The camera module  700  includes a circuit substrate  702 , an image sensor  704 , a liquid crystal shutter device  706 , an IR filter  708 , an actuator system  710 , and a movable lens group  712 . The image sensor  704  is fixably mounted on the circuit substrate  702 , the liquid crystal shutter device  706  is mounted on and/or integrated with the image sensor  704  via glass-on-die (GOD) technology, the IR filter  708  is fixably mounted to the actuator system  710 , the actuator system  710  is fixably mounted to the circuit substrate  702 , and the movable lens group  712  is movably coupled to the actuator system  710  so as to facilitate autofocus/zoom operations by moving along the Z-axis when actuated by the actuator system  710 . 
         [0033]    As can be seen, in particular embodiments of the present invention, a camera module includes a circuit substrate, an image sensor, an actuator system, a movable lens system, and a liquid crystal shutter device. 
         [0034]    In one particular embodiment, the image sensor is mounted on the circuit substrate, the actuator is mounted on the circuit substrate so as to cover the image sensor, the movable lens system is coupled to the actuator system, and the liquid crystal shutter device is disposed over the movable lens system such that the lens system is located between the liquid crystal shutter device and the image sensor. 
         [0035]    In an alternative embodiment, the camera module further includes a fixed lens group fixably mounted in the actuator system. Further, the image sensor is mounted on the circuit substrate, the actuator system is mounted on the circuit substrate such that the image sensor is positioned between the circuit substrate and the fixed lens group, the liquid crystal shutter device is positioned in the actuator system such that the fixed lens group is positioned between the image sensor and the liquid crystal shutter device, and the movable lens system is coupled to the actuator system such that the liquid crystal shutter device is positioned between the fixed lens group and the movable lens system. 
         [0036]    In another alternative embodiment, the camera module further includes an IR filter fixably mounted within the top portion of the actuator system. Further, the image sensor is mounted on the circuit substrate, the liquid crystal shutter device is mounted to the bottom portion of the actuator system, the bottom portion of the actuator system is mounted on the circuit substrate such that the liquid crystal shutter device is positioned above the image sensor, and the movable lens system is coupled to the top portion of the actuator system such that the IR filter is positioned between the movable lens system and the liquid crystal shutter device. 
         [0037]    In another alternative embodiment, the camera module further includes an IR filter fixably mounted within the bottom portion nof the actuator system. Further, the image sensor is mounted on the circuit substrate, the liquid crystal shutter device is mounted over the image sensor, the actuator system is mounted on the circuit substrate such that the image sensor and the liquid crystal shutter device are positioned between the IR filter and the circuit substrate, and the movable lens system is coupled to the top portion of the actuator system such that the IR filter is positioned between the movable lens system and liquid crystal shutter device. 
         [0038]    While the embodiments of the invention have been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as examples and not restrictive in character. For example, certain embodiments described hereinabove may be combinable with other described embodiments and/or arranged in other ways (e.g., process elements may be performed in other sequences). Accordingly, it should be understood that only example embodiments and variants thereof have been shown and described.