CarieScan PRO works on the principle of:
The CarieScan PRO (CarieScan, LLC, Charlotte, NC) is a device for the detection and monitoring of caries by the application and analysis of AC (alternating current) impedance spectroscopy (ACIST).
The CarieScan PRO claims to enable clinicians to evaluate demineralized tooth structure using ACIST by providing information about tissue being healthy, in the early stages of demineralization, or already significantly decayed.
The device provides a color scale and a numerical scale to determine the severity of the caries lesion and is accompanied by management recommendations that range from therapeutic prevention to operative intervention appropriate for the extent of the demineralization.

Reference- Sturdevant 6th ed Pg- 96
Beer lambert law
Laser fluorescence
Alternating current impedance spectroscopy
Complementary metal oxide technology have CMOS