The parameters of an off-axis cylindrical mirror-focused line-scanning system were studied to optimize the flatness of the 2 mm scan field. The scanning system parameters included the beam size, the distance between the scanning and the focusing mirror, the angle between the incident beam and the reflected beam, the optical scan angle, and the effective focal length of the cylindrical mirror. Because of the off-axis line-scanning system configuration, the scanning could be carried out either in the tangential (Y-scan) or in the sagittal (X-scan) plane. A 53 nm spectral bandwidth light source was used to evaluate the imaging performance of the scanning system. Since reflective optics is employed in this work for focusing, the scanning system could be used with a higher spectral bandwidth light source for optical coherence tomography applications. The effect of the angle between of the incident and reflected beams, the distance between the mirrors, the focal length of the cylindrical mirror and the scanning directions, on the flatness of the scan field were studied. It was proved that the sagittal scanning is least sensitive to variations in scanning system parameters and thus provides maximum flexibility in design.
The quality of the spectrometer affects the sensitivity fall-off, axial resolution, and depth scan range, therefore overall
performance of the spectral domain optical coherence tomography (SD-OCT) imaging. Chromatic aberration, optical
resolution, and detector array resolution are the key design consideration for high-quality OCT spectrometer.
Traditionally refractive optics spectrometer is used in SD-OCT. In the present work, the optical design of the reflective
optics spectrometer and of the refractive optics spectrometers is reported for high-speed line field optical coherence
tomography imaging. The performance of the spectrometers was compared by using the ZEMAX optical design
software. The ZEMAX optical modeling analysis shows that the reflective optics spectrometer provides better
performance by comparison with the refractive optics spectrometer.
Optical design of a spectrometer for all-reflective optics based line scan Fourier domain optical coherence tomography
(FD-OCT) imaging has been reported in this work for high-speed scanning. FD-OCT imaging data acquisition offers
significantly improved imaging speed in the depth direction compared to conventional time domain optical coherence
tomography (TD-OCT). On the other hand, line focused scanning improve imaging speed in the transverse direction
compare to commonly used flying spot scanning. Combination of FD-OCT acquisition and line focused scanner can give
higher imaging speed. Spectrometer is a critical submodule in FD-OCT system. Apart from the spectrometer optical
resolution, and detector array resolution, the chromatic aberration should be considered to design a high-quality FD-OCT
imaging spectrometer. The proposed imaging spectrometer consists of a planer reflective grating, off-axis parabolic
cylindrical mirror and a CCD array detector. Mirror focusing reduces the chromatic aberration because of its insensitivity
to the wavelength of the laser beam, therefore the spectrometer image quality enhanced by the reflective optics focusing.
Spot profile fall-off characteristic was analyzed by using ZEMAX optical design software.
The optical and analytical modeling of a line-scan optical coherence tomography (LS-OCT) system for high-speed three-dimensional
(3D) endoscopic imaging is reported. To avoid complex lens system and image distortion error, an off-axis
cylindrical mirror is used for focusing the line illumination on the sample surface and a micro mirror scanner is
integrated with the proposed configuration for transverse scanning. The beams are swept on the cylindrical mirror by the
micro mirror rotation and finally focused on the sample surface for transverse scanning. A 2mm by 3.2mm en-face
scanning is configured with a 2mm focused line and ±3° scanning mirror rotation. The proposed configuration also has
the capability of dynamic focusing by the movement of the cylindrical mirror without changing the transverse resolution.
The cylindrical mirror enhances the image quality by reducing the aberration. The system is capable of real-time 3D
imaging with 5μm and 10 μm axial and transverse resolutions, respectively.
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