Methods and devices for analyzing material properties and detecting objects in scattering media

A method for determining a phase spectrum of a complex spectral transfer function of a medium, said method being implemented by a computer program, stored on a non-transitory computer readable medium and configured to execute on a computer, said method comprising the steps of:

• a. determining a derivative of said phase spectrum, to obtain a phase-derivative spectrum, from a measured amplitude of said complex spectral transfer function using a measuring instrument;
• and
• b. integrating, using said computer, said phase-derivative spectrum to acquire said phase spectrum, wherein the phase-derivative spectrum is determined from the amplitude of the spectral transfer function by:
• 1. measuring the phase-derivative at one or more frequencies;
• and
• 2. using said measured phase derivatives to reconstruct said phase-derivative spectrum for all frequencies in the spectral range,
• c. providing a radiation source adapted to produce an beam having a wide spectral width;
• d. using a modulator controlled by electrical signals from a signal generator to modulate said beam;
• e. causing said modulated beam to interact with said medium;
• f. using an arrangement adapted for collecting radiation to collect radiation that has interacted with said medium;
• g. using a beam divider to divide said collected radiation into two portions;
• h. using a device configured to measure the intensity of radiation having different spectral components to measure the amplitude spectrum of the first portion of said collected radiation;
• i. transferring said measured intensity spectrum to the computer;
• j. using a device configured to divide a beam of radiation into its spectral components to divide the second portion of said collected radiation;
• k. using one or more detectors to detect said spectral components of said second portion of collected radiation;
• l. using one or more phase detectors to measure the phase lags of the electrical signals from said one or more detectors relative to said electrical signals from said signal generator;
• m. transferring said measured phase lags to said computer;
• and
• n. supplying said measured amplitude spectrum and said measured phase lags as inputs to the computer program and to determine said phase spectrum of said medium from said inputs.