Amplitude modulated continuous wave (AMCW) time of flight (ToF) range imaging provides a full field of distance measurement, but common hardware is implemented with digital technology which leads to unwanted harmonic content, a principle source of error in the distance measurements. Existing strategies for correction of harmonics require auxiliary measurements and amplify noise. A small modification of the data acquisition procedure is described which, intrinsically, is invariant to at least one harmonic. The third harmonic, the main cause of harmonic error, is targeted. Compared to traditional measurements the third harmonic is eliminated with no significant increase in noise variance observed.