Illuminate the ocular by narrow parallel beam when measuring high power aberration ocular would debase the precision of wavefront measurement. This paper designs and realizes an auto adjustable illumination system

adds a position adjustable collimation lens in the inlet beam path

adjusting which can precisely alter the diopter of illumination light source. The motorized stage can exactly and rapidly scan and locate the position of collimation lens. This paper measures model eye aberrations

and compares the experiment data by using narrow parallel beam illumination and results by using adjustable illumination system. The result shows that after improvement of illumination system

the signal-noise ratio was improved from 2:1 to 10:1; the result when measuring a -5D model eye is -5.041D±0.157D

while the former result -4.285D±0.208D. Thus

the improved illumination system obviously increases the signal to noise ratio of hartmann-shack sensor and makes the measurement result preciser.