Monte Carlo simulation model of OCT system based on confocal mode

Confocal scanning technique is widely used in standard OCT system with single-point detection. The beam incident into tissue is a cone-shaped beam focused by object lens and each photon must be launched along a particular direction which is a function of position. Although confocal scanning technique has great significance in improving transverse spatial resolution and increasing probing depth of OCT system, it was not taken into consideration in most pre-proposed Monte Carlo simulation (MCS) model of OCT system. In order to supplement such shortcomings, the definition of confocal microscopy structare and focused Gaussian beam is introduced in this paper. Combined with the improved mechanism for classifying back-scattered photons, an integrated MCS model of OCT system based on confocal mode is established. By applying the new model, the intensity distribution of focused Gaussian beam in tissue is presented firstly. Then, the difference of transverse spatial resolution and collection efficiency of Class I_a photons between confocal mode and non-confocal mode is discussed. Filially, the critical detecting depth of OCT system is estimated. According to the simulation result, the new MCS model is proved to be valid and more practicable for the simulation of OCT system.