Performance comparison between 8 and 14 bit-depth imaging in polarization-sensitive swept-source optical coherence tomography

We compare true 8 and 14 bit-depth imaging of SS-OCT and polarization-sensitive SS-OCT (PS-SS-OCT) at 1.3μm wavelength by using two hardware-synchronized high-speed data acquisition (DAQ) boards. The two DAQ boards read exactly the same imaging data for comparison. The measured system sensitivity at 8-bit depth is comparable to that for 14-bit acquisition when using the more sensitive of the available full analog input voltage ranges of the ADC. Ex-vivo structural and birefringence images of an equine tendon sample indicate no significant differences between images acquired by the two DAQ boards suggesting that 8-bit DAQ boards can be employed to increase imaging speeds and reduce storage in clinical SS-OCT/PS-SS-OCT systems. We also compare the resulting image quality when the image data sampled with the 14-bit DAQ from human finger skin is artificially bit-reduced during post-processing. However, in agreement with the results reported previously, we also observe that in our system that real-world 8-bit image shows more artifacts than the image acquired by numerically truncating to 8-bits from the raw 14-bit image data, especially in low intensity image area. This is due to the higher noise floor and reduced dynamic range of the 8-bit DAQ. One possible disadvantage is a reduced imaging dynamic range which can manifest itself as an increase in image artefacts due to strong Fresnel reflection.