Research Of Digital Pherometer Based On DSP

Digital spherometer is a revolution to traditional spherometer. This paper mainly introduces a kind of means about subdivision of grating moire fringe and its device used on digital spherometer system. Based on principle of subdivision, this device could realize 200 part-subdivisions and the resolution of system reached to 50nm, depended on common effects of differential amplifier, filer, comparator, trigger, analog-to-digital converter and DSP.Differential amplifier circuit and filer circuit improve the quality of original moire fringes and ultra-fast comparators improve the quality of pulse. The set adapts the high speed 12 bits A/D which has eight-channel track/hold circuits, so the parts of the apparatus are reduced and the system stability is improved. The DSP completes software-subdivision of grating moire fringes, the data process time is less 12ns and responding-frequency of the system is improved. The system acquires A/D value of shift-point by means of combined effect of software and hardware, which is innovational compared with traditions. Combined hardware and software, the application of subdivision to digital spherometer will be developed toward the nice prospect.