Study Of Dynamic And Invisible Messaging Technology Based On Visual MIMO

In this concept "visual MIMO" multiple light transmit elements of a light emitting array(LEA)are used as transmitters and the individual pixel elements of the camera act as multiple receive elements.The multiple parallel channels between transmitters and receivers realize a multiple input multiple output(MIMO)system.Although multiplexing information over parallel data channels is very similar to RF MIMO in concept,visual MIMO differs in its characterization significantly.Visual MIMO can avoid the problems,such as co-channel interference and eavesdropping,in RF communication,since the highly directional nature of optical transmissions.The large view of field of camera makes visual MIMO can meet the needs of mobile communication compared with the traditional wireless optical communication.As a result,visual MIMO is of great research significance and broad space for further growth.In this paper,visual MIMO technology is utilized to realize dynamic and invisible messaging.The information which is going to be sent is embedded into the image of an electronic display,and it is not visible to human.While a hand-hold moving camera pointed at the electronic display can receive a hidden message.The electronic display without changing its original purpose can have dual functionality by transmitting information.So the cost in communication equipments is reduced.And how to realize the embedding and extraction of the dynamic and invisible information is the work of this paper.Firstly,a computer LCD-camera communication system is established based on the principle of visual MIMO technology.And the computer vision algorithms which will be applied in the image processing are introduced in detail,including multi-resolution analysis,feature detection and matching,image segmentation and image geometric correction.Secondly,on the sending end,the original image is divided into four sub-images by Laplacian pyramid decomposition,and the message embedding is done by using a multiplicative constant on the top sub-image.The top sub-image which is the low frequency component of the original image is a not sensitive to human observer,so after the Laplacian pyramid reconstruction,the embedded message is invisible to human observer.The display images are played in form of video frame,so the dynamic and invisible messaging is implemented in sending end.Thirdly,on the receiving end,a camera observes the electronic display and images both the display and the background.The target image must be segmented from the observed image by image segmentation technique.For the position and orientation of the camera with respect to the display is unknown and not fixed,the imaging process creates geometric distortions in the observed image.So the observed image must be processed geometric correction before message extraction.Finally,the correction image is divided into four sub-images by Laplacian pyramid decomposition.And the message is extracted from the top sub-image.Compared the extracted message with the embedded message,it is showed that the communication system achieves the effective information transmission.