Localization of an object in tissue with phase modulation spectroscopy: reduction of the effects of the relative amplitude and phase on amplitude cancellation

In this paper, we discuss the effects of carious factors on the localizatio n of an object with amplitude cancellation phase modulation spectroscopy (P AIS) by an analytical method. The factors include the relative modulation p hase and the amplitude between two sources, the absorption coefficient and the size of the localized absorber. A localization method that can reduce t he effects of the relative modulation amplitude and phase between two sourc es on measurement is presented. In the new method, two measurements are car ried out, where modulation signals of mo sources in the second measurement are exchanged relative to those in the first measurement. The principle and the feasibility of the method are shown theoretically. Primary experimenta l results are presented.