Master–slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography

Abstract

Conventional spectral domain interferometry (SDI) methods suffer from the need of data linearization. When applied to optical coherence tomography (OCT), conventional SDI methods are limited in their 3D capability, as they cannot deliver direct en-face cuts. Here we introduce a novel SDI method, which eliminates these disadvantages. We denote this method as Master - Slave Interferometry (MSI), because a signal is acquired by a slave interferometer for an optical path difference (OPD) value determined by a master interferometer. The MSI method radically changes the main building block of an SDI sensor and of a spectral domain OCT set-up. The serially provided signal in conventional technology is replaced by multiple signals, a signal for each OPD point in the object investigated. This opens novel avenues in parallel sensing and in parallelization of signal processing in 3D-OCT, with applications in high- resolution medical imaging and microscopy investigation of biosamples. Eliminating the need of linearization leads to lower cost OCT systems and opens potential avenues in increasing the speed of production of en-face OCT images in comparison with conventional SDI.

Master/slave: a better tool for Gabor filtering optical coherence tomography imaging instruments

“…In other words, for each spectral sweep, the FFT delivers more data than retained in the final image or final volume. Here, we demonstrate that the MS technology [2] is a better tool to be used in a GF instrument than the FFT based method. When using MS, the FFT operation is replaced by multiple comparison operations of the signal at the photo-detector output with replicas of the same signal (masks) corresponding to the photo-detected signal obtained when a mirror is used at different axial positions [2].…”

Complex master slave interferometry

“…Master-Slave Interferometry (MSI) is a new approach to SDI to eliminate the chirp effects [15]. The MSI proceeds in two stages.…”

“…In a second stage (Slave), the object replaces the mirror and the channeled spectrum is compared with every CS exp saved in the memory block and used as a mask. The comparison operation of each mask with the channeled spectrum was implemented via correlation [15][16][17][18][19] or by simplified dot product procedures for faster implementation of correlation for argument zero [20,21]. The maximum value of each comparison (correlation) is selected to provide the depth information profile (A-scan) at each OPD value selected during the Master stage.…”

“…As the phase is discarded, it is not possible to eliminate its effects. To reduce the effect of the random phase shift, the correlation function is averaged over several lags [15][16][17][18][19] that leads to some deterioration of the axial resolution.…”

“…This method, Complex Master Slave Interferometry (CMSI), does not directly use CS exp as masks, contrary to [15][16][17][18][19][20][21], but develops a procedure to infer any number of masks from a reduced number of CS exp acquired. Additionally, the masks generated are complex in order to conserve the phase information.…”