Image monitoring system and object area tracking method

An image monitoring system comprising:

• an object area detection processing section that detects object area information from an image obtained by an input image signal on a basis of the input image signal;
• and
• an object area tracking processing section that performs object area tracking processing by associating a current object area with a past object area on a basis of the object area information detected by said object area detection processing section;
• wherein said object area tracking processing section associates said current object area with said past object area using unique identifying information, and
• said object area tracking processing section continues retaining identifying information given to a predetermined object area that has disappeared, and gives the retained identifying information to the predetermined object area when the predetermined object area reappears, and wherein said object tracking processing section discontinues retaining identifying information as a function of a pre-determined number of frames, said pre-determined number of frames corresponding to a number of frames in which the predetermined object area existed before it disappeared.