Abstract: This paper presents a new noncontact measuring instrument system with image processing technology.The architecture and the principle are described.Aiming at distilling the pointer signal,based on computing the centre and the radius of a circle by using point Hough transform,and then obtaining the probable pointer's angle through applying the method of the center projection,it brings forward a new means with sub-pixel orientation,and successfully actualizes the automatic detection of instrument.Experiments show that this system can satisfy the demand of the measuring with high precision and speediness.