CC BY
2Enhanced spectral domain optical coherence tomography using a linear wavenumber spectrometer
Y. Cai1, J. Zhang2*
1- School of Optoelectronic Engineering, Guilin University of Electronic Technology, China 2- School of Life and Environmental Sciences, Guilin University of Electronic Technology, China
In spectral-domain optical coherence tomography (SDOCT), conventional spectrometers, which use a grating and a line-scan camera, inherently suffer from nonlinear wavenumber responses. This nonlinearity reduces the sensitivity and axial resolution of OCT signals, necessitating post-processing to remap spectral interferograms into wavenumber functions. However, this approach is limited due to the uneven frequency spacing between the camera's pixels, which restricts the imaging range.
To address these challenges, we present a novel linear-wavenumber spectrometer design. Our design, employing a dual-prism and reflector arrangement, is cost-effective, straightforward, and significantly enhances the linearity of spectral dispersion in wavenumbers, a critical factor for SDOCT. We utilize iterative calculations through a global stochastic gradient descent method to effectively linearize higher-order dispersion. Compared to conventional designs, our method achieves a substantial improvement in wavenumber linearity for an 80 nm bandwidth at an 850 nm wavelength.
To verify this wavenumber linearity, we developed an accurate calibration method that uses the interference phase to determine the wavenumber of each pixel in the detection spectrum. Additionally, our new structure eliminates the need for resampling, enabling depth imaging at the Nyquist sampling limit. This advancement marks a significant improvement in spectrometer design for SDOCT, offering enhanced performance and resolution without the complexities and limitations of traditional systems.
