海水折射率测量在海洋学中发挥了重要作用，但对于海洋气候和海水流场监测领域，现有的折射率传感器无法满足应用场景的高精度与高采样率要求。有鉴于此，文中基于光外差干涉原理设计了海水折射率传感器，分析了该原理下的散粒噪声、相位解调噪声对传感器折射率测量的影响，研制了高精度海水折射率传感器样机，其采样频率为24 kHz，折射率变化量测量值的标准偏差为 $1.584\;8\times $$ {10}^{-8}\;\mathrm{R}\mathrm{I}\mathrm{U}$，该技术促进了海水折射率测量在海洋气候及海洋洋流等领域的应用。

基于视频的非接触光电容积脉搏波（Photoplethysmography， PPG）可以实现非接触式心率监测。为改善非接触PPG信号质量和提高非接触PPG技术检测心率的准确性，提出一种自适应感兴趣区域（Region of Interest， ROI）的方法。使用独立向量分析对人脸分区域处理，然后使用归一化分割选取信噪比和相关度最高的小区块作为自适应ROI来获取心率，通过对自适应ROI加权平均和频域处理得到非接触PPG信号。相比于预选定ROI的方法，该方法将头部静止状态下心率误差的均值和标准差从（4.72±6.46） 次/分降低至（0.52±1.49） 次/分，根均方误差（Root Mean Square Error， RMSE）从7.96次/分降低至1.50 次/分，平均误差率从9.45%降低至1.73%。头部运动状态下该方法的误差为（1.02±2.91） 次/分，RMSE为2.11 次/分，误差降低50%以上。使用Bland-Altman及相关性分析比较该方法与使用接触式PPG仪器得到的心率，计算得到头部静止时95%置信区间为-2.44~3.48 次/分，运动时为-2.76~4.79 次/分。最后通过对比与接触式PPG信号的波形，证明该方法得到了细节完整的PPG信号。实验结果表明，该方法显著提升了PPG信号的质量与心率的准确率。

This Letter proposes a coordinate difference homogenization matching method to solve motion influence in three-dimensional (3D) range-intensity correlation laser imaging. Firstly, features and feature pairs of gate images are obtained by speeded-up robust figures and bi-directional feature matching methods. The original mean value of the feature-pair coordinate differences is calculated. Comparing the coordinate differences with the original mean value, the wrong feature pairs are removed, and then an optimized mean value is updated. The final feature-pair coordinates are re-registered based on the updated mean value. Thus, an accurate transformation is established to rectify motion gate images for 3D reconstruction. In the experiment, a 3D image of a tower at 780 m is successfully captured by our laser gated imaging system on a pan–tilt device.

This Letter proposes a high bit-depth coding method to improve depth map resolution and render it suitable to human-eye observation in 3D range-intensity correlation laser imaging. In this method, a high bit-depth CCD camera with a nanosecond-scaled gated intensifier is used as an image sensor; subsequently two high bit-depth gate images with specific range-intensity profiles are obtained to establish the gray depth map and finally the gray depth map is encoded by an equidensity pseudocolor. With this method, a color depth map is generated with higher range resolution. In our experimental work, the range resolution of the depth map is improved by a factor of 1.67.

We present a method of time coding with ABAB synchronization timing control for real-time 3D super-resolution range-gated imaging (3DSRGI). To meet the high precision of time delay and pulse width in ABAB synchronization time sequencing, phase shift is implemented to achieve ns-scaled delay and width accuracy without restoring to high clock frequencies. Theoretical analysis and experiments prove that 1 ns delay and width precision is obtained by our timing control unit based on a single field-programmable gate array with 5 ns clock cycle. Finally, a prototype experiment of 3DSRGI is demonstrated at a 10 Hz video rate with 696 pixels×520 pixels.