1. A method for object detection in an image plane, comprising the steps of: constructing a Hidden Markov Model (HMM) for an image, and initializing a plurality of parameters of said HMM; obtaining an object mask Ω(t) at current time through an object mask Ω h (t−1) at previous time, and updating said plurality of HMM parameters of current time on the spatial domain; and re-estimating said object mask at current time based on said updated plurality of HMM parameters and a decoding algorithm.