Abstract: A device for measuring a distribution of selected properties of a material. The device includes an emitter configured to emit electromagnetic radiation at at least a first and second frequency in a selected frequency range through the material, at least one sensor configured to detect electromagnetic radiation transmitted through the material, and an analyzer configured to determine the distribution of selected properties based on the detected electromagnetic radiation at the at least first and second frequency. Further, the distribution of the selected properties is unchanged between the emitted electromagnetic radiation at the first and second frequencies.