An object detecting method, object detecting apparatus and intruding
object monitoring apparatus employing the object detecting method. A
predetermined monitor area having no object to be detected is imaged by
an imaging device and reference background sequential images are
registered in advance in a storage unit. When monitoring, the
predetermined monitor area is imaged by the imaging device while at the
same time sequentially outputting the images frame by frame from the
imaging device, a reference background image corresponding to the image
from the imaging device is selected from the reference background
sequential images, subtraction processing is carried out between the
image from the imaging device and a corresponding reference background
image, and the object detecting processing is carried out based on the
result of subtraction processing.