Since the detection of optical flow (two-dimensional motion field on an ima
ge) from image sequences is essentially an ill-posed problem, most of the c
onventional methods use a smoothness constraint for optical how heuristical
ly and detect reasonable optical flow. However, little discussion exists re
garding the degree of smoothness. Furthermore, to recover the relative thre
e-dimensional motion and depth between a camera and a rigid object, in gene
ral at first, the optical flow is detected without a rigid motion constrain
t, and next, the motion and depth are: estimated using the detected optical
flow. Rigorously speaking, the optical how should be detected with such a
constraint, and consequently three-dimensional motion and depth should be d
etermined. To solve these problems, in this paper, we apply a parametric mo
del to an optical flow, and construct an estimation algorithm based on this
model.