Optical imaging techniques provide low-cost, non-radiative images with high spatiotemporal resolution, making them advantageous for long-term dynamic observation of blood perfusion in stroke research and other brain studies compared to non-optical methods. However, high-resolution imaging in optical microscopy fundamentally requires a tight optical focus, and thus a limited depth of field (DOF). Consequently, large-scale, non-stitched, high-resolution images of curved surfaces, like brains, are difficult to acquire without z-axis scanning. To overcome this limitation, we developed a needle-shaped beam optical coherence tomography angiography (NB-OCTA) system, and for the first time, achieved a volumetric resolution of less than 8 μm in a non-stitched volume space of 6.4 mm × 4 mm × 620 μm in vivo. This system captures the distribution of blood vessels at 3.4-times larger depths than normal OCTA equipped with a Gaussian beam (GB-OCTA). We then employed NB-OCTA to perform long-term observation of cortical blood perfusion after stroke in vivo, and quantitatively analyzed the vessel area density (VAD) and the diameters of representative vessels in different regions over 10 days, revealing different spatiotemporal dynamics in the acute, sub-acute and chronic phase of post-ischemic revascularization. Benefiting from our NB-OCTA, we revealed that the recovery process is not only the result of spontaneous reperfusion, but also the formation of new vessels. This study provides visual and mechanistic insights into strokes and helps to deepen our understanding of the spontaneous response of brain after stroke.

人体呼出气包含氮气、氧气、二氧化碳等多种气体,其中很多气体可以作为各种疾病的相关标志物,通过测定特征呼出气体的组分及含量可以对多种疾病进行无创诊断。可调谐半导体激光吸收光谱(TDLAS)法由于具有灵敏度高、选择性好、响应速度快的优点,是一种常用的痕量气体光学检测技术。综述了基于TDLAS法检测痕量气体的原理,包括TDLAS技术种类、光源及多光程腔的选择等,并介绍了其在几种常见的呼出气检测中的应用进展。

Natural logarithm wavelength modulation spectroscopy (ln-WMS) is demonstrated in this Letter. Unlike the conventional wavelength modulation spectroscopy (WMS)-2f technique, it is a linear method even for large absorbance, which is the core advantage of ln-WMS. The treating method used in ln-WMS is to take the natural logarithm of the transmitted intensity. In order to determine the proper demodulation phase, the η-seeking algorithm is introduced, which minimizes the absolute value of the first harmonic within the non-absorbing region. Subsequently, the second harmonic of the absorption signal is extracted by setting the demodulating phase as 2η. To illustrate the validity of ln-WMS, it was applied to water vapor experimentally. The result shows that even if the absorbance (base-e) is between 1.60 and 6.26, the linearity between ln-WMS-2f and volume fraction is still established. For comparison, measurement with conventional WMS-2f was also done, whose response no longer kept linearity. The η values retrieved in continuous measurements and the residuals were shown so as to evaluate the performance of the η-seeking algorithm. Time consumed by this algorithm was roughly 0.28 s per measurement. As an alternative WMS strategy, ln-WMS has a wide range of potential applications, especially where the absorbance is large or varies over a wide area.

高能激光功率高、能量大, 造成激光能量计容易损坏和测量不确定度增加。围绕上述问题对国内外现有的几种高能激光能量直接测量方法进行了比较和归纳, 对各种技术的优点和缺点作了深入的分析, 在此基础上阐述了高能激光能量直接测量技术的发展趋势。研究表明, 提高热交换效率是提升高能激光能量计测量能力最高效的措施, 尤其是在采用体吸收模式和强制热交换模式的情况下这种效果更加明显; 消除吸收体上温度梯度对吸收体材料比热和温度传感器响应时间的影响是提高被动吸收型高能激光能量计测量准确度的关键, 在水流冷却型高能激光能量计和水流直接吸收型高能激光能量计中消除水流相变的影响和控制水流温度场不均匀造成的影响则是保证温度准确测量的关键。目前各种高热交换效率和新体制的测量方法得到快速发展和应用, 系统的测量能力和测量准确度大幅提高, 为了适应未来长时间测量需求, 能量累积型高能激光能量计逐渐被功率平衡型高能激光能量计所替代。

在高能激光能量计吸收体上很长时间内均存在较大的温度梯度，这导致吸收体真实温度的测量非常困难，材料的比热、传感器的响应度和吸收体的热损失对测量准确度的影响较显著，模拟了吸收体上温度场特性，提出了一种利用多个分立的热电偶传感器测量吸收体的温升的方法，通过对热电偶的间距以及在吸收体中的深度加以控制，可以准确地反映吸收体上每一小部分的平均温度，从而达到对比热和传感器响应度修正的目的；采取措施大幅降低热损失比例，并结合实际温度场分布和系统热平衡时间对热损失可以获得热损失占比；利用光线追迹方法可以大幅简化吸收体吸收率研究，以实际光束和吸收腔参数为模拟对象计算了吸收腔的吸收率，并对测量结果进行修正。在分析了系统各个环节的测量不确定度的基础上估算出设计的激光能量计的测量不确定度约为5.8％(k=2)，采用现场比对方法验证该测量不确定度的合理性。

提出了一种利用电加热丝作为校准源的高能激光能量计校准方法,将水流从吸收腔前端导入至加热容器,在加热后流入吸收腔。通过精确计量水流吸收的热能并与能量计测量结果进行比较,达到对高能激光能量计校准的目的。研究表明校准系统的热交换模型与吸收腔内的热交换模型一致,均经历了储能和功率平衡两个阶段。水流及相变气体的散射效应对测量结果的影响较小,经过修正后可以忽略其影响。通过深入分析各个环节的测量不确定度表明,残留能量和流量变化对测量不确定度的影响最显著,增加水箱的容积可以有效降低残留能量对测量不确定度的影响。在对各个环节的影响修正后估算出系统的测量不确定度约为4.8％(k=2),被校高能激光能量计校准后的测量结果与其他类型的参考高能激光能量计进行比对,两者具有很好的一致性,修正因子仅为1.006,标准偏差为1.4%。

氧碘高能激光近场存在较多的杂散光，这些光会严重影响光束传输和光束质量控制。通过对杂散光的产生机理、类型和传输规律的分析和模拟确定了不同类型杂散光的测量方法。利用两个能量计测量了30 m通道自由传输时的传输效率，利用测试光阑获得了通道内杂散光角谱曲线和镜面散射光能量。实验表明30 m通道自由传输时的能量损失约为5.2%，杂散光的角谱随着传输距离的增加逐渐增大，角谱也会随着光束质量的恶化显著增加。利用角谱曲线可以获得通道内任意位置处光阑上的热负荷，这为高能激光热管理技术奠定了坚实的基础。

设计并实现了一种对正交信号进行高速相位检测的FPGA电路，并将其成功应用于 自制单频激光干涉测长系统中。该电路主要采用CORDIC算法并使用流水线结构，同时为了矫正 实际测量时正交信号存在的畸变，增加了信号修正处理部分。仿真和实验结果表明该电路稳定可 靠，满足高速、高精度相位检测的需求。

A diffusion theory model induced by a line source distribution is presented for oblique-incidence reflectometry. By fitting to this asymmetric diffusion model, the absorption and reduced scattering coefficients \mu_a and μ^'_s of the turbid medium can both be determined with accuracy of 10% from the absolute profile of the diffuse reflectance in the incident plane at the negative position –1.5 transport mean free path (mfp') away from the incident point; particularly, μ^'_s can be estimated from the data at positive positions within 0–1.0 mfp' with 10% accuracy. The method is verified by Monte Carlo simulations and experimentally tested on a phantom.

传统的电荷耦合器件(CCD), 在400nm以下CCD的量子效率太低, 而传统的基于CCD的紫外增强技术可以提高CCD对紫外波段的响应,但是存在光谱信号弱的缺点, 并且系统分辨率也因此降低。一种自行研制的CCD紫外荧光增强技术, 其创新在于去除CCD表面保护玻璃, 通过真空镀膜的方法将晕苯直接沉积在CCD敏感元件表面,能有效地提高CCD的紫外响应度, 并削弱薄膜对分辨率的影响。对于离散谱线, 253.6nm波长的相对强度提高10倍。对于连续谱线, 紫外波段的信号也得到明显增强, 截止频率从290nm降至220nm。该种方法制作紫外CCD成本不高, 可以实现批量生产, 适合工业应用。