Varifocal is a common function in optical system

and the agency performing it is called Varifocal Mechanism. However

the traditional varifocal mechanism has several disadvantages

when moving a group of zoom lens along or across the optical axis

such as large occupation of room

complicated configuration

long time consumption

disable in self-lock when power off

etc. In order to improve the performing of the varifocal mechanism

our research institution has developed a novel rotary varifocal mechanism driven by Ultrasonic Motor

and the test on it was successfully conducted which proved the availability of this mechanism. Moreover

this mechanism can realize several varifocal at one time

instead of two. The experiment suggested that this new varifocal mechanism realized the largest rotating angle with no error 0.432′

and corresponding ray displacement error in imager was less than 0.034mm when photo pixel was 30μm and focal length of optical system was 300mm

that less than the length of one pixel.