In this paper

the detection results in the case that laser light source has a certain space distribution of light intensity are critically analysed on the basis of detecting principle of optic-deflection ultra microforce detecting.We find that the space distribution of light intensity of the laser source has no influence on the detecting results on the condition of ultra-microforce detecting.That is the output of PSD completely and correctly reflects the value of the force acting on cantilever.Howeve

with different values of force acting on cantilever the lights corresponding to the position of weight center of light spot detected by PSD are different.Calculation method and calculation example of the variation of the space distribution of light intensity of incident light after reflected by the deflected cantilever are also given

and suggestion for further extraction the information of the above mentioned variation from the reflected beam and putting it in use is pointed out in the article.