Adaptive Linear Frequency Multiplication in Double-frequency Laser Orientation System

In order to reduce the effect of variable speed on the resolution improvement via linear frequency multiplication in double-frequency laser interferometric system of displacement measurement, this paper presents a new adaptive digital linear frequency multiplication method. A counter with timing fiducial oscillator acts as a frequency multiplier, and the count value in the prior period is taken as the reference for the current period to give the decimal part of a signal period. From a numerical simulation on a practical possible mode: uniform acceleration-unifom speed-uniform deceleration, we obtain the relationship between the measurement error and the acceleration value. The simulation results show the feasibility of this method which provides a new and simple way through hardware linear multiplication for frequency multiplication of periodic signal with unequal periods.