Abstract
Depth-visualizing sensitivity can be degraded due to imperfect optical alignment and non-equidistant distribution of optical signals in the pixel array, which requires a measurement of the re-sampling process. To enhance this depth-visualizing sensitivity, reference and sample arm-channeled spectra corresponding to different depths using mirrors were obtained to calibrate the spectrum sampling prior to Fourier transformation. During the process, eight interferogram patterns corresponding to point spread function (PSF) signals at eight optical path length differences were acquired. To calibrate the spectrum, generated intensity points of the original interferogram were re-indexed towards a maximum intensity range, and these interferogram re-indexing points were employed to generate a new lookup table. The entire software-based process consists of eight consecutive steps. Experimental results revealed that the proposed method can achieve images with a high depth-visualizing sensitivity. Furthermore, the results validate the proposed method as a rapidly performable spectral calibration technique, and the real-time images acquired using our technique confirm the simplicity and applicability of the method to existing optical coherence tomography (OCT) systems. The sensitivity roll-off prior to the spectral calibration was measured as 28 dB and it was halved after the calibration process.
Highlights
Optical coherence tomography (OCT) enables micrometer-resolution biomedical imaging to be performed in real time [1,2,3]
Camera number of pixels in current study: 2048). This all step 7, intensity points had to be interpolated to the total number of pixels of the optical coherence tomography (OCT) line scan camera the maximum intensity points were resampled using nearest adjacent intensity points coinciding with
According to the graphical representation, Figure suggests that the trend of the non-calibrated point spread function (PSF) width increasingly fluctuates in the deeper regions, while the width of the fluctuates in the deeper regions, whilerelatively thefluctuates widthconstant ofin thethe spectrally-calibrated
Summary
Optical coherence tomography (OCT) enables micrometer-resolution biomedical imaging to be performed in real time [1,2,3]. If the data are not linearized by being inserted into equidistant frequency slots, the depth-dependent PSF can be distorted, and each pixel of the line-scan camera of the optical spectrometer can integrate with a different spectral width [22,23,24]. Some studies have focused on optical hardware optimizations by using a wavelength-scanning filter technique, which provides lookup tables instead of interpolating non-linear data [34,35]; other studies have used prism implementations to achieve real-time imaging [17,25,36]. Semi-automatic spectral mapping is another technique, which was acquired using dual spectrometers, where a set of calibration interference fringes has to be acquired from both spectrometers [41,42] In these two aforementioned methods [41,42], non-linearity in the unwrapped phase information was sampled by generating linear vectors.
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