Measurement system of cornea were designed to improve diopter parameter measurement precision of eye cornea.Standard ring was projected onto an eye cornea with infrared

after reflecting from eye cornea

the virtual object with eye cornea parameter was formed and imaged in the CCD image sensor through optical system processing.Binary image was divided up by DSP TMS320F2812

and diopter parameter of eye cornea was calculated with interpolation algorithm.The experiment was carried through by using the eye analogue with standard cornea

and comparison to refractor with model number TPCON KR-8100 made in Japan

results show both measurement error is less than ±0.02 mm which is minimum error of diopter prescribed by national metrology bureau

and measurement precision attain subpixel.