The details of cross-sectional images based on Fourier domain optical coherence tomography play an important role that is limited to nonuniform sampling, spectral dispersion, inverse discrete Fourier transform (IDFT), and noise. In this section, we propose a method for emphasizing axial details to the greatest extent possible. After removing spectral dispersion, uniform discretization in the wavenumber domain is performed based on two interferograms via a specified offset in depth, with no spectrum calibration. The sampling number in IDFT is optimized to improve axial sensitivity up to 1.62 dB. The proposed process has the advantage of being based on numerical computation rather than hardware calibration, which benefits cost, accuracy, and efficiency.

Optical coherence tomography angiography (OCTA) has emerged as an advanced in vivo imaging modality, which is widely used for the clinic ophthalmology and neuroscience research in the rodent brain cortex among others. Based on the high numerical aperture (NA) probing lens and the motion-corrected algorithms, a high-resolution imaging technique called OCT microangiography is applied to resolve the small blood capillary vessels ranging from 5 μm to 10 μm in diameter. As OCT-based techniques are recently evolving further from the structural imaging of capillaries toward spatio-temporal dynamic imaging of blood flow in capillaries, here we present a review on the latest techniques for the dynamic flow imaging. Studies on capillary blood flow using these techniques will help us better understand the roles of capillary blood flow for normal functioning of the brain as well as how it malfunctions in diseases.

作为图像处理的一个重要手段, 边缘增强技术对振幅型和相位型物体成像有着重要的作用。而基于径向希尔伯特变换的涡旋滤波技术因其能够实现各向同性边缘增强倍受关注, 但传统的涡旋滤波由于中心奇点和锐利边缘引起的衍射会造成背景噪声的加剧和对比度的降低。近年来众多课题组针对涡旋滤波旁瓣抑制提出了种类各异的新型涡旋滤波器, 此外基于涡旋滤波的各向同性和各向异性边缘增强技术也得到了迅速发展。文中扼要地总结了近年来几种抑制涡旋旁瓣的方法, 包括拉盖尔高斯振幅调制、贝塞尔振幅调制、艾里振幅调制, 并从标量涡旋滤波和矢量涡旋滤波两个方面分别综述了各向同性和各向异性边缘增强的实现方法与研究进展。

报道了一种工作于1 μm波段、正常色散区、基于半导体可饱和吸收镜(SESAM)的被动锁模光纤激光器。激光器以高掺杂Yb光纤为增益物质，结合可调谐滤波器，形成环形腔结构。采用976 nm半导体激光器抽运，当抽运功率大于16 dBm时，激光器可实现1033~1069 nm波长范围内重复频率为25.4 MHz的宽带可调谐输出，性能稳定，在调谐范围内均可观测到非常规则的矩形输出光谱。在固定抽运功率下，对调谐范围内输出功率、光谱带宽、时域脉宽进行了实验测量和分析。在波长为1064 nm时，用单通道光栅对将谱宽为1.745 nm、时域脉宽为34.85 ps的脉冲压缩至15.45 ps。