Array detection for speckle reduction in optical coherence microscopy

This paper introduces a spatial-diversity method for speckle suppression in optical coherence microscopy. The method is based on combining interference signals from an array of detectors placed in the back focal plane of the objective lens, such that elements receive light backscattered from the sample volume at different angles. Incoherently adding ('compounding') the signals increases the signal-to-noise ratio of the processed image compared to that attainable with a single detector. The speckle-reduction method was demonstrated with a benchtop microscope equipped with a quadrant photodiode. To evaluate its potential application in dermatology, images of living skin acquired with and without compounding were compared. The quality of the compounded images was found to be substantially better. A signal-to-noise gain close to a factor of two (the theoretical maximum attainable using four detectors) was achieved without a significant loss in resolution. The method can be applied to arrays with a larger number of elements, potentially enabling more advanced forms of spatial-diversity, and adaptive-optics methods.