Research on the effect of numerical aperture on probing depth of OCT system with new Monte Carlo simulation model

As a numerical experiment, Monte Carlo simulation (MCS) has been proven to be a credible and flexible method for predicting the distribution of light in random media. It has full control of many parameters of optical system, which may be cumbersome to obtain in a real experiment. In standard OCT system, confocal microscopy structure with different Numerical Aperture (NA) is selected to acquire superior transverse resolution and unique property of optical sectioning. But the effects of numerical aperture on the probing depth of OCT system are difficult to estimate. In this paper, a new Monte Carlo simulation model of OCT system based on confocal mode is put forward to simulate the confocal microscopy structure and focused gaussian beam. It makes up the deficiency of traditional MCS model, which can only be applied to infinity narrow beam. By applying this new model, the effects of NA on probing depth of OCT system are analyzed, and the estimation of critical probing depth of OCT system is discussed. Study indicates that a smaller numerical aperture has more advantage on the probing depth when the transverse resolution is ensured.