Noise sources and optoelectronics which affect axial detection performance of time domain, Fourier domain, and swept source optical coherence tomography

Abstract

Techniques based on spectral interferometry (SD-OCT) have recently been examined, with authors often suggesting superior performance compared to time domain optical coherence tomography (TD-OCT) techniques. While these technologies have similar resolutions and the spectral techniques may currently claim faster acquisition rates, their detection parameters may be inferior. This work examines the theoretical signal to noise ratio and dynamic range of these techniques including time domain. Considering the practical limits of optoelectronics, the often ignored or misunderstood factors which affect performance, such as vacuum fluctuations, the actual source of thermal noise, excess noise and A/D conversion losses, were taken into account. Methods for potentially improving signal to noise ratio (SNR), such as fast laser sweeping with high laser intensities and CCD integration, were evaluated as well. This is critical because dynamic range translates directly into imaging depth. The technologies are compared relative to the differences in these parameters. While Fourier domain OCT (FD-OCT) has some advantages such as signal integration, it appears unlikely that its disadvantages can ultimately be overcome. Ultimately, time TD-OCT appears to have the superior performance with respect to SNR and dynamic range. However certain positive aspects of swept source OCT (SS-OCT) leave open the possibility that its performance may approach that of TD-OCT.