Patent Publication Number: US-2017359520-A1

Title: Imaging systems having an electrowetting lens

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/349,703, filed on Jun. 14, 2016, entitled “IMAGING SYSTEMS HAVING AN ELECTROWETTING LENS,” by Neil J. Boehm et al., the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to imaging systems having an electrowetting lens. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, an imaging system is provided comprising: an image sensor; an electrowetting lens positioned in front of the image sensor and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor; and a controller coupled to the electrowetting lens and configured to select a field of view of the image sensor by selecting the electrical stimulus to be applied to the electrowetting lens. 
     According to another embodiment of the present invention, an image sensor disposed in the vehicle is provided comprising: an image sensor disposed in the vehicle; an electrowetting lens positioned in front of the image sensor and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor; and a controller coupled to the electrowetting lens and configured to select a field of view of the image sensor by selecting the electrical stimulus to be applied to the electrowetting lens. 
     According to another embodiment of the present invention, an imaging system for scanning of a person&#39;s irises is provided comprising: an image sensor; an electrowetting lens positioned in front of the image sensor and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor; and a controller coupled to the electrowetting lens and configured to select a field of view of the image sensor by selecting the electrical stimulus to be applied to the electrowetting lens. 
     According to another embodiment of the present invention, an imaging system for scanning of a person&#39;s face for a facial recognition system is provided. The imaging system comprises: an image sensor; an electrowetting lens positioned in front of the image sensor and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor; and a controller coupled to the electrowetting lens and configured to select a field of view of the image sensor by selecting the electrical stimulus to be applied to the electrowetting lens. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a block diagram showing an imaging system according to a first embodiment; 
         FIG. 2A  is a block diagram illustrating use of an electrowetting lens to function with a narrower field of view; 
         FIG. 2B  is a block diagram illustrating use of an electrowetting lens to function with a wider field of view; 
         FIG. 2C  is a block diagram illustrating use of an electrowetting lens to function with a shifted field of view; 
         FIG. 3A  is a top view of a vehicle having a plurality of imaging systems constructed in accordance with the embodiment shown in  FIG. 1 ; 
         FIG. 3B  is a top view of the vehicle shown in  FIG. 3A  with the fields of view of the cameras altered; and 
         FIG. 4  is a block diagram showing an imaging system according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows an example of an imaging system  10  having an image sensor  20 , an electrowetting lens  30  positioned in front of the image sensor  20  and configured to change at least one optical characteristic in response to an electrical stimulus so as to change a field of view of the image sensor  20 , and a controller  40  coupled to the electrowetting lens  30  and configured to select a field of view of the image sensor  20  by selecting the electrical stimulus to be applied to the electrowetting lens  30 . The electrowetting lens  30  may also be used for auto-focusing. 
     The electrowetting lens  30  may take any form known in the art including the forms shown in  FIGS. 1 and 4 . In general, as shown in  FIG. 1 , the electrowetting lens  30  includes an oil  32  that may take various shapes to form a variable lens in response to the application of an electrical stimulus such as the application of a selected voltage to one or more electrodes  34  within the electrowetting lens  30 . The lens  30  may include two glass substrates  35   a  and  35   b  that combine with electrodes  34   a,    34   b  and insulating member  36   a  to form a chamber in which the oil  32  is disposed. The remainder of the chamber in which the oil  32  is located is filled with another fluid such as water  33  that does not mix with the oil  32 . Note that the electrode  34   b  that contacts the oil  32  may be coated with an insulator material.  FIGS. 2A, 2B, and 2C  show three examples of the shapes the oil lens  32  may form in response to two different voltages applied to electrodes  34   a  and  34   b.  In  FIG. 2A , the oil lens  32  takes the shape of a convex glass lens and the electrowetting lens  30  functions as a bi-convex lens. In  FIG. 2B , the oil lens  32  takes the shape of a concave glass lens and the electrowetting lens  30  functions as a bi-concave lens. In  FIG. 2C , the oil lens  32  takes a tilted or rotated shape so that the electrowetting lens  30  shifts the field of view to one direction (i.e., left, right, up, or down). By changing the shape of oil lens  32 , the focal length may be changed as may the direction of the optical axis. When placed in front of an image sensor  20 , the electrowetting lens  30  may be used to change the field of view of the image sensor  20  as well as to pan the field of view across the imaging surface of the image sensor  20 . Such a capability would provide many advantages in imaging systems used in vehicles as well as in security cameras and mobile devices, such as smartphones, notebooks, and laptop computers. 
     The electrowetting lens  30   a  shown in  FIG. 4  is similar to that as shown in  FIG. 1  except that the configuration of electrode  34   b  is different and rear glass substrate  35   b  includes a spherical recess with the electrode  34   b  coated over the entire surface of substrate  35   b.  An insulating layer  36   b  is provided across the entire surface of electrode  34   b  and fills the electrode-coated spherical recess in substrate  35   b.  Further, an annular glass ring  35   c  may be provided about the periphery of the chamber between substrates  35   a  and  35   b.  In this lens configuration, a drop of oil  32  is centered by a gradient in the electric field applied through electrodes  34   a  and  34   b.    
     One example of an application for imaging system  10  would be a rear vision camera  10   a  of a vehicle  18  as shown in  FIGS. 3A and 3B . In this application, the field of view  15   a  of the rear vision camera  10   a  could be dynamically changed without reducing the resolution of the image output from the rear vision camera  10   a.  For example, the field of view could be shifted to keep the image of any detected vehicle within the image. Further, the field of view could be widened or narrowed as shown in  FIGS. 3A and 3B  depending upon whether the vehicle was in reverse or driving forward, or depending upon the forward speed of the vehicle or the type of road upon which the vehicle is traveling. Note that the rear vision camera  10   a  may be located at the rear of the vehicle or at the sides of the vehicle as cameras  10   a ′ and  10   a ″ with respective variable fields of view  15   a ′ and  15   a ″. The images captured by the rear vision cameras  10   a,    10   a ′, and  10   a ″ may be displayed on a display located in the rearview mirror  16  or other location in the instrument panel or console. Additionally or alternatively, the images may be processed for use in autonomous vehicle control or a driver assist function, such as parking assist, blind spot detection, rear collision warning, lane departure warning, lane keeping assist, etc. 
     Another example of a vehicle application for imaging system  10  would be as a forward vision camera  10   b  as shown in  FIG. 3A . Such forward vision cameras  10   b  may be mounted at or near the rearview mirror  16  to capture images forward of the vehicle through its windshield. Images captured by the forward vision camera  10   b  may be used for a number of different driver assist functions or autonomous vehicle control functions. For example, the images may be used for headlamp control, lane departure warning, parking assist, adaptive cruise control, lane keeping assist, forward collision warning, object detection, pedestrian detection, and traffic sign recognition. However, it may be desirable to use a wider or narrower field of view  15   b  for each of these functions so as to limit the information in the captured images to that information that is relevant for the particular function. Accordingly, the provision of the electrowetting lens  30  in a forward vision camera  10   b  provides the advantage of changing the field of view for a selected function without a loss in resolution. Further, the ability of the electrowetting lens to shift the field of view  15   b  left or right allows the forward vision camera  10   b  to look in the direction of an upcoming turn. 
     When used for headlamp control, the forward vision camera  10   b  may advantageously maintain a high pixel count per degree of field of view when the field of view is narrowed to focus on distant objects. This allows for more accurate detection of vehicles and other objects at greater distances. Likewise, the field of view may be changed to look ahead in the direction of an upcoming turn so that vehicles on the turn may be detected more quickly and accurately. 
     Another example of a vehicle application for imaging system  10  would be as an interior vision camera  10   c  as shown in  FIG. 3A . Such interior vision cameras  10   c  may be mounted at or near the rearview mirror  16 , an upper console, or reading light assembly in order to capture images inside the vehicle and display the images to the driver or other occupants. For example, such a camera  10   c  may be mounted to view back seat passengers and display the images to the driver on a display that may be mounted in the rearview mirror  16  or other location in the instrument panel or console. This is particularly useful if one of the passengers is a baby and even more advantageous if the baby is in a car seat facing rearward. By employing an electrowetting lens in such the interior vision camera  10   c,  the field of view  15   c  may be shifted around the interior of the vehicle so as to view a particular passenger or location in the vehicle. The field of view  15   c  may also be widened or narrowed to capture front seat passengers or focus on rear seat passengers. Such a change in the field of view  15   c  may be effectuated by manual control of the driver or automated control. Automated control may be used for video conferences so as to shift the field of view to whichever vehicle occupant is speaking. 
     By using the electrowetting lens  30  in imaging systems used in a vehicle, one can avoid having to only rely upon digital zooming for changing a field of view, which results in a reduction in the resolution of the images captured by the system. Further, to the extent one intends to avoid this by providing a mechanical zoom lens, such a mechanical zoom lens is much more complex to make and subject to breakage. 
     If the variable lens  30 ,  30   a  was oscillated between two or more images or fields of view, a first image stream having a first field of view could be supplied to a first display  50   a  and a second image stream having a different second field of view may be supplied to a second display  50   b  and thus two or more different image streams could be captured and displayed in real time. The different image streams could also be displayed in different display areas of one display  50   a.  Using one camera to collect multiple images is an advantage over using multiple cameras. For example, if the camera was set to oscillate between two images at 30 Hz, one could update two different images on two different displays or two different display zones at 15 Hz. 
     The imaging system  10  may also find advantageous application in security cameras, particularly for those applications where two separate image sensors are used to capture retinal images of both a person&#39;s eyes. By using the electrowetting lens  30 , the field of view may be shifted from one eye to the other and thereby eliminate the need for two separate cameras. Further, the field of view may be initially set to wide to capture a person&#39;s face and identify the location of their eyes and then zoom in on each eye. This would make it more practical to implement biometric screening security measures (particularly retinal imaging) in mobile devices, which typically only have one camera aimed in any one direction. 
     Security cameras having an electrowetting lens with a variable field of view may be used in home security systems as well as in smoke detectors and strobe light fixtures. Similarly, a vehicle camera such as camera  10   c  may be used for security purposes to scan the irises of the driver prior to starting the vehicle. The imaging system may also be used for scanning of a person&#39;s face for a facial recognition system. 
     Although imaging system  10  is shown as having just the electrowetting lens  30  in front of image sensor  20 , additional conventional lenses may be used in combination with electrowetting lens  30  to obtain the desired fields of view and focus. The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the claims as interpreted according to the principles of patent law, including the doctrine of equivalents.