Size distortion occurs when image method is used to measure moving object size because there is relative movement between the image sensor and object.According to the dynamic measurement procedure of image sensor

mathematic modals of dynamic acquisition are created

and factors are analyzed which affect distortion characteristic

such as sensor sampling frequency

moving velocity of measured object

etc.Then experiments are finished.It indicates that distortion can be reduced by the means of optimizing the sample parameters based on the mathematic modals

and it can also improve the dynamic measurement accuracy by amend distortion data.