文章：Dirk Lorenser, Xiaojie Yang, and David D. Sampson, "Ultrathin fiber probes with extended depth of focus for optical coherence tomography," Opt. Lett. 37, 1616-1618 (2012) 链接：https://doi.org/10.1364/OL.37.001616 实现extend depth of focus的原理：the light travels through two sections of GRIN fibers with different apertures to create two different focal positions, which results in a extended depth of focus. […]
The reviewed paper is Rapid-scanning forward-imaging miniature endoscope for real-time optical coherence tomography. One advantage of forward-viewing OCT endoscope over transverse-imaging counterpart is that it eliminates the need for mechanically actuating the entire endoscope assembly or a rotational fiber-optic coupler. Another possible merit is that the lateral-priority image acquisition sequence greatly reduces the depth-scanning speed. […]
This old paper introduced two setups of forward-viewing instruments for optical coherence tomography (OCT). In the beginning, the author mentioned one advantage of forward-viewing devices: permitting data to be collected before the device is introduced into the tissue. I assume it’s because of forward-viewing OCT’s characteristics. Two setups were proposed: a hand-held probe, and a […]
If you are interested in this paper Shot-noise limited, supercontinuum-based optical coherence tomography, please find it here. Main contribution Current supercontinuum (SC) -based SD-OCT system cannot be operated in the shot-noise limited area because of its strong pulse-to-pulse relative intensity noise of the supercontinuum source. The authors propose an all-normal dispersion (ANDi) fiber based supercontinuum […]
1 Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation In OCT, dispersion compensation is usually performed by matching the optical materials and path lengths in the two interferometer arms. Dispersion can also be compensated by using numerical techniques. Principle of SD-OCT: The sample is illuminated with broadband light. Backreflected or backscattered […]
Based on the direction of the imaging beam with respect to the longitudinal axis of the probe, OCT endoscopes can be divided into side-viewing endoscopes and forward-viewing endoscopes. Based on the location of the beam scanning device, OCT endoscopes can be divided into proximal-end scanning probes and distal-end scanning probes.
1.在Optical Coherence Tomography – Technology and Applications的第39页中，提到： The spectral resolution is governed by multiple factors including the optical aberrations in the spectrometer lenses, the resolution of the diffraction grating, camera pixel size, and electronic pixel cross talk. 关于光谱仪的分辨率，可以见How to build a spectrometer – theory，或者这里.
1.在Optical Coherence Tomography – Technology and Applications的第36页中，提到： The interference of the two beams will have a spectral modulation as a function of frequency which can be measured using a spectrometer. The periodicity of this modulation will be inversely related to the echo time delay. Therefore, different echo delays will produce different frequency modulations. The echo […]
1.在Optical Coherence Tomography – Technology and Applications的第27页中，提到： OCT imaging is performed with low numerical aperture focusing in order to have a large depth of field. 通常情况下，成像的焦深大于相干长度，这样就能保证在一定的深度下，系统能够实现相干成像。 2.在Optical Coherence Tomography – Technology and Applications的第29页中，提到： OCM images can be obtained at different depths by adjusting the focus depth while matching the reference arm path delay to the […]
1.在Optical Coherence Tomography – Technology and Applications的第10页中，提到： Using low-coherence length light, interference only occurs when the path lengths are matched to within the coherence length。 为什么要在OCT系统中使用弱相干光，就是为了获得较小的相干长度，而理论的轴向分辨率是相干长度的2倍。因此，这样就可以得到更小的轴向分辨率。补充一下相关内容： Low-coherence light can be characterized as having statistical phase discontinuities over a distance known as the coherence length, which is inversely proportional to the frequency bandwidth of the light. […]