Patent ID: 7184908

Claim:
A calibration method for a time measurement apparatus comprising a time-voltage converter for converting the time interval of measurement signals and clock signals to voltage, an analog-digital converter for converting said voltage to digital values, and a time-interval measurement unit for measuring said time interval of measurement signals from said digital values, said method comprising: generating calibration signals for a subperiod of said clock signals by measuring the period of said clock signals, and shifting the period of said calibration signals by said period difference, with said calibration signals having a shorter period difference than the time corresponding to the resolution of said analog-digital converter; measuring said calibration signals, finding said digital values, and analyzing the cumulative frequency distribution of said digital values; determining a calibration value for said digital values such that said cumulative frequency distribution is linear; converting said voltage converted by said time-voltage converter to said digital values in accordance with said calibration value; and measuring said time interval of measurement signals from said digital values converted in accordance with said calibration value, wherein said time interval is outputted to a predetermined apparatus or stored in a memory of said time-interval measurement apparatus.