1. Field of the Invention
The present invention relates to surveillance systems, and, more particularly, to security systems that detect the presence of humans.
2. Description of the Related Art
Surveillance systems, also known as security systems, are known to include security devices, such as motion detectors, for sensing the presence of human activity. A problem with such motion detectors is that they are unable to discern between activity by humans and activity by pets or other moving objects like blinds or fans. Consequently, households that include pets may need to disable the motion detectors of their security systems in order to avoid false alarms.
Human-only detection (HoD) is an attempt to achieve robust detection of human activities while ignoring all other moving objects. It is a very challenging task mostly because such detection may call for some intelligence in the first place as to what characterizes human activities and what does not.
Some attempts at human activity detection have been based on the use of radar sensing technology. Radar has some obvious advantages in surveillance applications. Radar is inexpensive and easy to deploy on a large scale. In contrast to video cameras, radar may work covertly and can be functional continuously, 24/7, both days and nights. A disadvantage of radar, however, may be that its output is not so straightforward to visualize or translate into useful information.
In the current literature, the state-of-the-art method of radar based human detection involves modeling human activities. Specifically, an attempt is made to model each individual body part and its corresponding response in the radar signals and estimate the most likely activity being observed given the currently received signal. This type of approach is similar to the subsource fitting and yields reasonable performance as long as the human being detected is acting in a normal fashion, e.g., walking with a constant rate of arm swings. A problem may arise when an intruder tries to trick the system by acting in an unusual fashion. In such cases, the intruder's actions almost never match the ideal action model, and hence the system does not identify the intruder as being human. Moreover, it is not clear how such a system will perform if other activities occur, such as a pet walking around. Finally, known methods employ only a continuous wave (CW) type of radar.
What is needed in the art is a security sensor that can effectively discriminate between humans and non-human motion activity (e.g., pets).