May 2006

EEEL collaboration produces noise model for polarization-sensitive Optical Coherence Tomography

In a collaboration between the EEEL Optoelectronics Division, the National Physical Laboratory (UK), and the University of Texas, a model has been developed to describe the sources of noise encountered in polarization-sensitive Optical Coherence Tomography (PS-OCT). This model will aid the development of noise reduction techniques, leading to faster and more sensitive measurements. Optical Coherence Tomography is a rapidly developing technique for three-dimensional imaging of tissue with spatial resolutions on the order of 1 m to10 m. When polarization sensitivity is added, PS-OCT increases contrast in many tissues, providing a sensitive measure of tissue health including early identification of glaucoma, characterization of the arterial plaques that lead to heart attacks, and assessment of burn depth.

Noise affects PS-OCT results by reducing image quality and increasing measurement time. In order to identify the sources of this noise, experimental results were used to guide the development of a model to predict the noise behavior observed in PS-OCT measurements. Three distinct noise mechanisms were identified (intensity noise, polarization speckle, and polarization-dependent scattering). The first two were included in a PS-OCT simulation. Experimental results indicate that the scattering strength of the tissue specimen determines which noise source dominates. Simulations for low and medium scattering strengths yielded good qualitative agreement with measurements on birefringent rat tail tendon. However, quantitative results obtained by comparing the polarimetric signal-to-noise ratios for experiment and simulation indicate that polarization-dependent scattering coefficients will need to be included in the model. This will be the next step in the project.

The EEEL portion of this work was done as a part of the OCT metrology development effort in the Optoelectronics Division, including Paul Williams, Shellee Dyer, Tasshi Dennis, and Shelley Etzel.

Contact: Paul Williams, phone 303-497-3805