Methods and apparatus for precise measurement of time delay between two signals

Abstract

Apparatus and methods are disclosed for measuring time delays between pulse streams or other input signals and for measuring ion beam energies in an ion implantation system. A variable delay apparatus is applied to one input signal, and the signals are correlated or compared in a correlator apparatus providing a minimum, maximum, or other ascertainable output signal value when a delay value of the variable delay is representative of the time delay between the first and second input signals. By adjusting or sweeping the variable delay until the ascertainable correlator apparatus output value is obtained, the actual time delay is determined as the dialed-in value of the variable delay that produces the ascertainable correlator output value. The variable delay measurement apparatus and methods may be employed in ion implantation system for measuring ion beam energies using time of flight probes, wherein the system and the time delay measurement apparatus may be calibrated to remove any residual delays of the system, such as delay offsets related to channel imbalance in the system and connecting devices. In addition, a unique error correction method is disclosed, which may be applied to the time delay measurement system measurement to minimize or mitigate errors introduced by electronic components of the system.