Abstract:
A wide angle, e.g., fisheye, surveillance, e.g., security, camera comprises an offsetting mechanism for offsetting a center of the image sensor relative to an optical axis of the fisheye lens system. Often when fisheye cameras are wall mounted a substantial area of the image may be dedicated to looking at sky or ceiling. A similar situation can arise when a fisheye camera is ceiling mounted next to a wall or other structure. Portions of the image will be unchanging and of little value for surveillance. The camera provides the capability to offset the lens system relative to the image sensor. In examples, this offset is performed as a factory manufacture or calibration step. In other examples, the offset is performed as an adjustment in the field at the time of installation or thereafter.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 62/132,602, filed on Mar. 13, 2015, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Video surveillance, e.g., security, systems are often deployed in and around buildings as well as in metropolitan settings. Example buildings and metropolitan settings include schools, government buildings, commercial buildings, residential buildings, roads and highways, and town and city centers. 
         [0003]    These video security systems typically include surveillance, e.g., security, cameras that connect via a security network to a control system. Additional components include network video recorder (NVR) systems and monitors for displaying images such as video from the security cameras. 
         [0004]    The security cameras typically have a lens and image sensor that are fixed, adjustable, or motorized. A fixed security camera will have the lens and imager system permanently fixed in a set position (i.e., lens and imager system cannot change position with respect to camera body). On the other hand, an adjustable security camera&#39;s lens and imager system is movable with respect to camera body (e.g., installer can move the lens and imager system to different positions) so that it can be pointed down a hall or at a door, for example. A motorized security camera, such as a pan-tilt-zoom (PTZ) security camera, utilizes motor(s) to automatically move the lens and imager system to different positions usually under operator or automatic control. 
         [0005]    Fixed security cameras often have wide angle lens systems to compensate for their inability to be aimed. An extreme example of a wide angle camera is a fisheye camera. The fisheye security camera uses an ultra-wide-angle fisheye lens to form an image on the image sensor. 
         [0006]    The fisheye security cameras are typically used in situations in which there is a need to capture a wide field of view in a single image. They also tend to be more mechanically robust than adjustable cameras. The fisheye security cameras provide this wide field of view by utilizing the fisheye lens to provide, for example, between 180 degrees and 360 degrees of surveillance range. Due to the wide field of view, the raw image captured by the imager chip is distorted, however. 
         [0007]    The installation process of a fixed security camera (e.g., fisheye security camera) in a video security system involves several steps. An installer mounts the fisheye security camera at a desired location that allows for the fisheye security camera to capture a wide area of interest. For example, the fisheye security cameras are typically installed in a wall mode orientation or ceiling mode orientation. In the wall mode orientation, the optical axis of the camera&#39;s lens system extends in a horizontal direction. This is common when the fisheye security camera is installed on a wall of a building or room. In the ceiling mode orientation, the optical axis of the camera&#39;s lens system extends in a vertical direction. This is common when the fisheye security camera is installed on a ceiling of a room or hallway or on a mounting arm extending from a building, lamppost or other structure. In either mode, the camera should usually be leveled to ensure good image orientation. Then, the installer will usually program the video security system with the fixed security camera&#39;s orientation. 
         [0008]    In general, there is distortion processing software to correct a distorted or warped image by de-warping the image. In particular, this distortion processing software uses image processing algorithms or models corresponding to the lens being used (e.g., fisheye lens) and information on the camera&#39;s orientation mode to correct and rotate the distorted image. 
       SUMMARY OF THE INVENTION 
       [0009]    When a wide angle or fisheye camera is mounted in the wall mode orientation, a substantial area of the image may be dedicated to looking at sky, if outdoor mounted, or the ceiling, if indoor mounted. A similar situation can arise when a fisheye camera is mounted in the ceiling mode orientation and located next to a wall or other structure. Thus, here also, portions of the image will be unchanging and of little value for surveillance. These portions of the captured image are unlikely to have any surveillance or security value and are often thus deemed to be “uninteresting.” 
         [0010]    At the same time, the typical wide angle or fisheye camera has an image “sweet spot”. The image distortion generated by the wide angle lens means optical resolution varies across the image. In some systems, optical resolution drops off dramatically being just over half the center resolution 66% across the lens and down to 40% at a point 80% across the lens. 
         [0011]    The present invention concerns modifying the standard wide angle, e.g., fisheye, camera so that it is better adapted or can be adapted to the particular situation in which it is installed. The regions of the image that are deemed uninteresting are reduced and/or the camera sweet spot is better directed to the regions of the image that are deemed to have the most value. 
         [0012]    This is accomplished by allowing the lens to be offset relative to the image sensor. In examples, this offset is performed as a factory manufacturing or calibration step. On other examples, the offset is performed as an adjustment in the field at the time of installation or thereafter. 
         [0013]    In general according to one aspect, the invention concerns a wide angle, e.g., fisheye, surveillance camera comprising an image sensor for detecting images, a wide angle lens system for forming images on the image sensor, and an offsetting mechanism for offsetting a center of the image sensor relative to an optical axis of the wide angle lens system. 
         [0014]    Typically, an area of a projected aperture of the wide angle lens system at the plane of the image sensor is larger than an area of the image sensor. For example, an area of a projected aperture of the wide angle lens system at the plane of the image sensor is 50% or 100% larger than an area of the image sensor. This provides leeway to adjust the sensor relative to the lens. 
         [0015]    In one embodiment, the offsetting mechanism offsets the center of the image sensor relative to an optical axis of the fisheye lens system along only one axis. However, in other embodiments, the offsetting mechanism offsets the center of the image sensor relative to an optical axis of the wide angle lens system along both axes of the plane of the image sensor, using a two dimensional stage, for example. 
         [0016]    In some implementations, the offsetting mechanism has the capability to offset the center of the image sensor relative to an optical axis of the wide angle lens system by a distance that is greater than 10% length of the image sensor. In other cases, the sensor offsetting mechanism has the capability to offset the center of the image sensor relative to an optical axis of the wide angle lens system by a distance that is greater than 20% or even 50% of the length of the image sensor. The sensor offsetting mechanism may even have the capability to offset the center of the image sensor relative to an optical axis of the wide angle lens system by a distance that is greater than 20% or even 50% of the length of the image sensor along both axes of the plane of the image sensor. 
         [0017]    In some cases, the system is field adjustable. For example, the offsetting mechanism can comprise an adjustment screw, for example, that is accessible from an exterior of a body of the camera. 
         [0018]    In other cases, the system may be factory configurable. Here, an indicium, which is visible on the camera and which indicates a direction that the image sensor is offset with respect to the fisheye lens system, is helpful. 
         [0019]    In general according to another aspect, the invention features a method for installing a wide angle surveillance camera. This method comprises installing the camera, and offsetting a center of the image sensor relative to an optical axis of the wide angle lens system to reduce uninteresting portions within images generated by the camera. 
         [0020]    In general, according to still another aspect, the invention features method for installing a wide angle surveillance camera. This method comprises installing the camera and adjusting a body offset direction indicia indicating direction that image sensor is offset to reduce uninteresting portions within images generated by the camera. 
         [0021]    The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
           [0023]      FIGS. 1A and 1B  show the relationship between the image sensor and the projected lens system aperture at the image sensor plane for a traditional full fisheye and a full frame fisheye, respectively; 
           [0024]      FIG. 2  is a perspective schematic view of a fisheye security camera including an image sensor offsetting system; 
           [0025]      FIG. 3  is a plan schematic view of a room or hallway with fisheye security cameras installed at various locations; 
           [0026]      FIG. 4  shows the relationship between the image sensor and the projected lens system aperture at the image sensor plane along with a distortion profile of the fisheye lens system; 
           [0027]      FIG. 5  shows the relationship between the image sensor and the projected lens system aperture with an image sensor offset relative to the optical axis of the fisheye lens optical system according to the present invention; 
           [0028]      FIG. 6  shows the relationship between the image sensor and the projected lens system aperture with an image sensor offset relative to the optical axis of the fisheye lens optical system according still another embodiment in which the projected lens system aperture is large relative to the image sensor at the sensor plane; 
           [0029]      FIG. 7  shows the relationship between the image sensor and the projected lens system aperture with an image sensor offset along two axes relative to the optical axis of the fisheye lens optical system according still another embodiment; 
           [0030]      FIG. 8  is a schematic cross-sectional view of the fisheye security camera showing the image sensor mounted on a sensor offsetting mechanism; 
           [0031]      FIG. 9  is a schematic cross-sectional view of the fisheye security camera showing the image sensor mounted on a sensor offsetting mechanism according to a second embodiment; and 
           [0032]      FIG. 10  is a method of installation and offset calibration. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0034]    As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Further, the singular forms including the articles “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms: includes, comprises, including and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, it will be understood that when an element, including component or subsystem, is referred to and/or shown as being connected or coupled to another element, it can be directly connected or coupled to the other element or intervening elements may be present. 
         [0035]      FIGS. 1A and 1B  show the relationship between the image sensor and the projected lens system aperture at the image sensor plane. 
         [0036]      FIG. 1A  illustrates the relationship for a traditional full fisheye. In this configuration, a relatively large portion of the image sensor  110  is unused since the lens system projected aperture  120  fits entirely within the area of the image sensor  110 . 
         [0037]      FIG. 1B  illustrates the relationship for a traditional full frame fisheye. Here, the lens system is designed relative to the placement of the image sensor  110  so that the area of the image sensor fits within the projected aperture  120  of the lens system. The advantage of this system is that it more fully utilizes the area of the image sensor at the expense of not being able to detect the full image formed by the lens system. In general, in this configuration, the area of the image sensor detects or covers about 80% of the projected aperture. 
         [0038]      FIG. 2  shows a fisheye surveillance, e.g., security, camera  100  including an image sensor offsetting system  200  for the image sensor  110 . 
         [0039]    In general, the fisheye camera  100  comprises a camera body  102 . The fisheye lens system  112  is held by this camera body and collects light from the surrounding environment to form an image on the internal image sensor  110 . 
         [0040]    In the illustrated embodiment, the image sensor  110  is held by an image sensor offsetting system  200 . This is internal to the body  102  and has the capability of moving the center of the image sensor  110  relative to the optical axis  126  of the fisheye lens system  112 . 
         [0041]    In the illustrated implementation, offset adjustment screw  220  is provided. This allows for the adjustment of the image sensor offsetting system  200 . This adjustment is accessible from the exterior of the camera body  102  so that it can be changed by an installer or at the time of its manufacture, for example. 
         [0042]    According to another aspect, a body offset direction indicium or indicia  105  are also included. This indicium indicates direction that image sensor is offset. As result, if the offsetting mechanism is configured in the factory, indicia are used so that the installer knows the direction in which the image sensor has been offset relative to the fisheye lens system  112 . As result, the installer will use this indicia to rotationally align the body  102  of the fisheye security camera  110  so that the indicium is aligned with an uninteresting direction or adjacent to structure (sky or wall), for example. 
         [0043]      FIG. 3  illustrates an exemplary room or hallway  300  with installed wide angle surveillance cameras  100  (e.g., fisheye security cameras). The security cameras  100  are installed in different orientations for monitoring the room or hallway  300  and individuals  306  in the room or hallway  300 . The security cameras  100 - 1 ,  100 - 2  are mounted to the ceiling  302 , ceiling mode orientation. Security camera  100 - 3  is mounted to the wall  304 , wall mode orientation. 
         [0044]    These different mounting positions illustrate how fisheye surveillance cameras may be installed such that they capture uninteresting portions of the image. For example, security camera  100 - 1 , being located in the center of the ceiling  103  probably has few uninteresting or stationary portions of its captured image. In contrast, security camera  100 - 2  is located adjacent to a wall. As result, large portions of its image will be uninteresting. In a similar situation, security camera  100 - 3  is installed on a vertically extending wall  104 . Therefore, it will “see” the ceiling which is probably uninteresting from a surveillance standpoint. 
         [0045]      FIG. 4  shows the relationship between the image sensor  110  and the projected lens system aperture  120  at the image sensor plane. 
         [0046]    Also shown is the distortion profile of the fisheye lens system. Due to this distortion effect from the wide angle fisheye lens, there is a resulting high accuracy or resolution region  108  of fisheye lens system. This corresponds to the lens&#39;s sweet spot. 
         [0047]    According to the invention, the relationship between the projected aperture  120  and specifically this sweet spot  108  is adjusted relative to the extent of the image sensor  110  in order to optimize the relationship between these areas and the specific image that is collected by the lens system  112 . 
         [0048]      FIG. 5  shows the relationship between the image sensor  110  and the projected lens system aperture  120 . Here, the image sensor  110 , and specifically its center  128 , is offset relative to the optical axis  126  of the fisheye lens optical system  112 . 
         [0049]    Typically, the offsetting mechanism has the capability to offset the center  128  of the image sensor  110  relative to the optical axis  126  of the fisheye lens system  112  by a distance (y offset) that is greater than 10% length of the image sensor. In the illustrated example, the center  128  of the image sensor  110  is offset relative to an optical axis  126  of the projected aperture/fisheye lens system  120 ,  112  by a distance (y offset) that is about 20% or greater than the length of the image sensor  110  along the direction of offset. 
         [0050]    Of note in the illustrated embodiment, the image sensor  110  is offset in only one direction in the two-dimensional plane of the image sensor  110 . Specifically, it is offset in the negative y-axis direction. 
         [0051]      FIG. 6  shows the relationship between the image sensor  110  and the projected lens system aperture  120 . In this example, the projected lens system aperture is large relative to the image sensor at the sensor plane. That is, this embodiment is a variant of the traditional full frame fisheye in which the frame is much smaller than projected aperture  120 . Generally, an area of a projected aperture  120  of the fisheye lens system at the plane of the image sensor  110  is 50% larger than an area of the image sensor  110 . In other embodiments, area of the projected aperture  120  of the fisheye lens system  112  at the plane of the image sensor  110  is 100% larger than an area of the image sensor  110 . 
         [0052]    The advantages of these configurations is that there is more leeway in which to adjust the image sensor  110  and specifically adjust the image sensor relative to the lens&#39;s sweet spot  108  to ensure that the image sensor is maximizing the interesting portions of the captured image. 
         [0053]      FIG. 7  shows the relationship between the image sensor  110  and the projected lens system aperture  120  according to another embodiment. In this example, the image sensor  110  is offset along two axes (in the plane of the sensor  110 ), relative to the optical axis  126  of the fisheye lens optical system  112  and specifically its projected aperture  120 . 
         [0054]    Specifically in the illustrated embodiment, the image sensor  110  is shifted in the negative y-axis direction and the negative x-axis direction. Although in other embodiments, it is shifted in either the positive y-axis direction or the positive x-axis direction. In general, this shift is either performed as an initial factory calibration or it is performed in the field by the operator in order to minimize the uninteresting portions of the image that are captured by the image sensor  110 . 
         [0055]    Typically, the offsetting mechanism has the capability to offset the center  128  of the image sensor  110  relative to the optical axis  126  of the fisheye lens system  112  by distances in both axes (x offset, y offset) that is greater than 10% length of the image sensor along the respective axis. In the illustrated example, the center  128  of the image sensor  110  is offset relative to an optical axis  126  of the projected aperture/fisheye lens system  120 ,  112  by distances in both axes (x offset, y offset) that is about 20% or greater than the length of the image sensor  110  along the direction of the offset. 
         [0056]      FIG. 8  is a schematic cross-sectional view of the fisheye surveillance camera showing the image sensor  110  mounted on the sensor offsetting mechanism  200 . 
         [0057]    In the illustrated embodiment, the fisheye lens system  120 , mounted within the housing  102 , captures light from the surrounding environment. The fisheye lens system forms an image of this light onto the image sensor  110 . Typically, this image sensor  110  is mounted on a circuit board  122 , which is mounted to a base  124  of the fisheye camera  100 . 
         [0058]    In the illustrated embodiment, the sensor offsetting mechanism  200  is mechanically located between the sensor PCB  122  and the base  124 . The offsetting mechanism  200  comprises a single axis stage system that is mounted to both the image sensor circuit board  122  and the base  124 . Specifically, lead nuts  124  are mounted on the bottom face of the circuit board  122 . These engage a lead screw  222 . The screw mounts  226  in turn mount the lead screw  222  to the base  124 . As result, when the operator, or the calibration system within the factory, turns this lead screw  222  at the offset adjustment screw head  220 , the circuit board  122  and thus the image sensor  110  are moved along the y-axis to thereby move or offset the center  128  of the image sensor  110  relative to the optical axis  126  of the fisheye lens system  120 . 
         [0059]      FIG. 9  is a schematic cross-sectional view of the fisheye security camera showing the image sensor mounted on a sensor offsetting mechanism  200  according to a second embodiment. This embodiment includes an x-y axis offset stage  228 . Specifically, this two axis stage is mounted mechanically between the image sensor circuit board  122  and the fisheye camera base  124 . This allows the center  128  of the image sensor  110  to be adjusted in long both the x-axis and the y-axis relative to the optical axis  126  of the fisheye lens system  120 . 
         [0060]      FIG. 10  is a method of installation and offset calibration. It illustrates how the fisheye camera system can be adjusted in the field. Specifically, the installer first mounts the camera body to the wall or ceiling in step  504 . Then, in step  506 , the installer views the image generated by the camera  100  using, for example, a portable or surveillance system monitor. The installer assesses the portion of the image that may contain uninteresting regions, such as a view of the sky or the ceiling or an adjacent wall. Then, in step  508 , the installer adjusts the sensor offsetting mechanism  200  at screw head  220  to reduce these uninteresting portions in the image. 
         [0061]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.