Abstract:
A multi-sensor network camera providing up to 360 degrees angle of view. The includes multiple image sensors with individual optics, one or more image processors, compression units and network interfaces mounted in the single housing. The image sensors are positioned in non-parallel planes, cumulatively providing panoramic field of view and image streams originating from all sensors share the same image compression and network interface hardware, providing for low cost implementation. The images from all sensors are transmitted over the network simultaneously via packet interleaving, with appropriate bandwidth reduction achieved by image decimation. Simultaneously with transmission of decimated images from all sensors, full resolution window or entire image of one or more sensors may also transmitted, where the selection of contents is based on motion detection or user setting.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/486,928, filed Jul. 14, 2003, the contents of which are incorporated by reference herein. 

   Also incorporated by reference herein are the following applications filed on even date herewith: 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Priority 
             
             
                 
               Title 
               Application 
             
             
                 
                 
             
           
           
             
                 
               WIDE DYNAMIC RANGE 
               60/486,929 
             
             
                 
               NETWORK CAMERA 
             
             
                 
               DUAL SPECTRAL BAND 
               60/486,927 
             
             
                 
               NETWORK CAMERA 
             
             
                 
               DISTRIBUTED VIDEO 
               60/486,926 
             
             
                 
               SURVEILLANCE SYSTEM WITH 
             
             
                 
               SECURE REMOTE STORAGE OF 
             
             
                 
               ALARMED IMAGES AND 
             
             
                 
               REMOTELY ACCESSIBLE IMAGE 
             
             
                 
               ARCHIVES 
             
             
                 
               HIGH-RESOLUTION NETWORK 
               60/486,930 
             
             
                 
               CAMERA WITH AUTOMATIC 
             
             
                 
               BANDWIDTH CONTROL 
             
             
                 
               VIDEO SURVEILLANCE SYSTEM 
               60/486,931 
             
             
                 
               WITH TARGET PATH 
             
             
                 
               RECONSTRUCTION 
             
             
                 
                 
             
           
        
       
     
   
   SUMMARY 
   The subject of this invention is a multi-sensor network camera providing up to 360 degrees angle of view. The camera disclosed in the present invention comprises multiple image sensors with individual optics, one or more image processors, compression units and network interfaces mounted in the single housing. In the preferred embodiment image sensors are positioned in non-parallel planes, cumulatively providing panoramic field of view. In the preferred embodiment image streams originating from all sensors share the same image compression and network interface hardware, providing for low cost implementation. In the preferred embodiment the images from all sensors are transmitted over the network simultaneously via packet interleaving, with appropriate bandwidth reduction achieved by image decimation. In one of the embodiments of this invention, simultaneously with transmission of decimated images from all sensors, full resolution window or entire image of one or more sensors is also transmitted, where the selection of contents is based either on motion detection or user setting. 
   In its preferred embodiment the present invention includes computer on the receiving end of the network interface and connected to the computer monitor, where said computer runs image processing and acquisition software configured to produce composite panoramic image by performing image “stitching”, where said “stitching” is designed to eliminate image overlaps and to assemble composite panoramic image from images taken by different sensors of the panoramic camera. 

   
     BRIEF DESCRIPTION OF FIGURES 
       FIG. 1  depicts block diagram of panoramic network camera system; 
       FIGS. 2A-2C  depict multi-sensor panoramic network camera head designs; 
       FIG. 3  depicts panoramic network camera cross-sections; 
       FIG. 4  depicts block diagram of multi-sensor panoramic network camera; 
       FIG. 5  depicts transmission and visualization of images from multi-sensor panoramic network camera; 
       FIG. 6  depicts mounting arrangement of panoramic cameras in multi-camera surveillance system with complete coverage of area under surveillance. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a block diagram illustrating the main components of the multi-sensor panoramic network camera. The present invention is a multi-sensor network camera comprising two or more image sensors with individual optics ( 101 ), one or more image processors, network interface for transmission of the images off camera ( 104 ) and may comprise one or more memory buffers for temporary image storage, where said image sensors are positioned in non-parallel planes as to increase the cumulative field of view of the camera, said image processors may provide image sensor control, color processing and image compression and include at least one image processing module common to all image sensors ( 103 ), where said common to all sensors image processing module provides selection/multiplexing of the data stream to be output from the camera and may also be equipped with image compression engine. 
   In one embodiment of this invention, three or more image sensors ( 205 ) are positioned as to cumulatively provide 360 degrees field of view along at least one circumference with the center at the camera location  201  ( FIG. 2A) and 202  ( FIG. 2B ). In another embodiment of this invention, two or more image sensors are positioned as to cumulatively provide 180 degrees field of view along at least one circumference with the center at the camera location  203  ( FIG. 2C ). In yet another embodiment of the present invention the sensors are mounted inside the camera as to provide cumulative field of view completely covering at least 180 degrees hemisphere centered on the camera ( 301  through  304 ).  FIGS. 2 and 3  illustrate the examples of the arrangement of the image sensors in multi-sensor panoramic network camera. In each case illustrated, the image sensors are side-to-side with each other, but at different angles that together cover the desired field of view. 
   In one embodiment of the present invention, a camera contains one image processing/multiplexing module that is equipped to decimate and compresses the images from multiple sensors in a time-interleaved fashion and to submit them to the network interface or buffer in on-board image memory buffer. In one embodiment of this invention camera transmits over the network interface decimated images from some sensors and full resolution images from others, where image-processing module is configured to decimate images from one or more image sensors prior to compression while compressing full-resolution images or portions/windows of the images from one or more other image sensors. 
   In one embodiment of the present invention the image sensors are high-resolution CMOS image sensors. In another embodiment of this invention multiple image-processing units perform the image compression, where each said image-compression unit is configured to compress images from one of the image sensors in the camera. In the later embodiment, common to all image sensors image processor is equipped to perform the function of selection/multiplexing of compressed image streams to the network interface of the camera. 
   In one of the embodiments of the present invention the image-processing unit is equipped with motion detection and tracking capability, where image-processing unit can identify the moving target as it exits the field of view of one image sensor and enters the field of view of another. In the later embodiment the camera transmits over the network interface the un-decimated image window centered on the selected moving target and may also transmit decimated or un-decimated images from some or all of the sensors in the camera in a time-interleaved fashion where said interleaving may be performed on a frame-by-frame basis or on a packet-by-packet basis. In yet another embodiment of this invention the selection of the image streams to be transmitted off camera via network interface is performed by the user, where said selection is communicated to the camera via network interface. 
   A block diagram of an embodiment of the present invention is shown in  FIG. 4 . In this embodiment of the present invention, the multi-sensor panoramic network camera comprises multiple image sensors ( 403 ), image buffer memory ( 420  and  421 ), network interface ( 422  and  407 ) and ASIC or Field Programmable Gate Arrays (FPGAs) operating under control of low cost microprocessor ( 404 ), where said ASIC or FPGAs implement image pre ( 401 ) and post ( 402 ) processors in the form of massively parallel image processing pipeline executing time-critical operations on image pixels, where the flow of image pixels is operated on by the sequential stages of the pipeline with each pipeline stage operating in parallel with all or many of the other pipeline stages, while said microprocessor controls the operation of the image processing pipeline, performs image pipeline and network initialization operations, relatively slow operations (performed on a once-per-frame basis) associated with auto exposure, white balance, image stream multiplexing and protocol-level network interface computations as well as maintains the register space constituting the user interface to the camera. 
   In one embodiment of the present invention the output of each image sensor is processed in association with said image sensor image pre-processor. The image pre-processors are implemented as image processing pipelines that comprise multiple line memory buffers for 2-dimensional processing ( 408 ), block for interpolation of one-color-per-pixel Bayer pixel array into 3 color-per-pixel stream ( 409 ), block implementing image sharpening and low-light signal-to-noise improvement by applying high-pass and low-pass filters to the image ( 410 ), color correction block implementing the multiplication of the RGB pixel components by 3×3 color correction matrix ( 411 ), RGB to YUV transformation blocks ( 412  and  414 ), gamma correction block implemented as look-up table ( 416 ), as well as Auto Exposure (AE) ( 418 ) and Auto White Balance (AWB) ( 419 ) measurement engines that collect image brightness and color statistics required for AE and AWB algorithms, at least 2 frame buffers ( 420  and  421 ) and associated memory access controller ( 417 ) for assembly ping-pong buffering of processed and incoming frames. 
   In one embodiment of the present invention the image buffers storing the output of the image pre-processors are connected to a single image multiplexer and decimation block ( 429 ), where said block is in turn connected to the image post-processor ( 402 ). 
   In another embodiment of the present invention all image sensors are connected to the single image stream multiplexer and decimator that in turn is connected to the single image pre-processor, where said image pre-processor is then connected to a single post-processor. This embodiment allows low-cost implementation of the present invention due to resource sharing but, in general, has lower overall image processing and transmission bandwidth than that of the preferred embodiment. 
   In one embodiment of the present invention image post-processor ( 402 ) comprises pipelined JPEG image compression and network packet generation modules. 
   In one embodiment of the invention, pipelined implementation of JPEG compression includes blocks that perform MCU formation and buffering ( 428 ), Forward Discrete Cosine Transform (FDCT) ( 427 ), zigzag scan, quantization ( 426 ) and entropy coding ( 425 ). In one embodiment of the present invention 2-dimensional FDCT is implemented as two passes through 1-Dimensional FDCT transform, utilizing the fact that FDCT is a separable transformation. 
   In yet another embodiment of the present invention, more efficient image compression, such as JPEG2000 or MPEG-2 is substituted for baseline JPEG implementation. 
   In one embodiment of the present invention a modified version of Trivial File Transfer Protocol (TFTP—as described in RFC783) is implemented as the primary mode of image transmission, where TFTP protocol headers are formed and recorded in the transmit packet buffers ( 422 ) by the microprocessor ( 405 ), data fields of the TFTP packets, i.e. image data, along with the corresponding checksums are formed by the output stages of the image post-processor ( 423 ). 
   In one embodiment of the present invention, following the image compression, the image stream is stored in one of the three network packet buffers, where these buffers are arranged in such a way, that one buffer contains the packet currently being transmitted to the Media Access Control (MAC) Ethernet interface ( 407 ), one buffer contains a packet to be transmitted next and one buffer is available for storage of the compressed data coming out of the image compression module. This triple buffered arrangement guarantees that there is always a packet available for transmission, thus maximizing utilization of available network bandwidth and also facilitates re-transmission in the event of network errors. 
   In one embodiment of the present invention, microprocessor interfaced with image processing pipeline and Ethernet MAC and PHY hardware is also used to support a number of network protocols. In one embodiment, to reduce overall complexity of implementation, a minimal set of protocols consisting of UDP, TFTP, ARP, IP, and ICMP protocols are supported. 
   In another embodiment of the present invention TCP/IP and DHCP protocols are also supported. 
   In one embodiment the present invention includes a computer on the on the receiving end of the network interface and connected to the computer monitor ( 106 ), where said computer runs image processing and acquisition software configured to produce composite panoramic image by performing image “stitching”, where said “stitching” is designed to eliminate image overlaps and to assemble a composite panoramic image from images taken by different sensors of the panoramic camera. In one embodiment of the present invention images from individual sensors of the panoramic camera are transmitted over the network in decimated (reduced resolution) mode. The visualization of multiple images acquired from multi-sensor panoramic camera as a single composite image displayed on the computer or other monitor is illustrated in  FIG. 5 . 
   In one embodiment of the present invention panoramic network camera is equipped to output both decimated and full resolution images and portions of images (windows). In one embodiment the computer software is also configured to display on the monitor full resolution image or portion of the image ( 502 ) to allow for instantaneous electronic zooming-in and inspection of the details of the panoramic image. 
     FIG. 6  illustrates exemplary mounting arrangements of the panoramic cameras in multi-camera surveillance system with complete area coverage. In one embodiment all image sensors mounted in the camera are high-resolution CMOS image sensors.