Abstract: A new method for accurate measurement of the time interval is proposed. In the time interval to be measured a given RC circuit is charged, and then the charged voltage across the capacitor is sampled by use of a precision A/D converter. Based on the law of charging, the width of the time interval is obtained by the look-up table method. The theoretical measurement accuracy could be as high as several picoseconds. In addition, this method has a smaller blind region of ranging than that of the analog time interpolation. When a 40MHz clock is used, the blind region of ranging is less than 18m.

Key words: pulse laser range-finding, A/D, time interval measurement, look-up table