A method for evaluation of target media parameters using visible through near infrared light is disclosed. The apparatus comprises a light source, illuminator/collector, optional illumination wavelength selector, optional light gating processor, imager, detected wavelength selector, controller, analyzer and display unit. The apparatus illuminates an in situ target. The sample absorbs some light while a large fraction of the light is diffusely scattered within the sample and some light exits the sample and may be detected in an imaging fashion using wavelength selection and an optical imaging system. The method extends the dynamic range of the optical imager by extracting additional information from the detected light that is used to provide reconstructed contrast of smaller concentrations of chromophore. Using a reiterative calibration method, acquired spectra and images are analyzed and displayed in near real time in such a manner as to characterize functional and structural information of the target tissue.
