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。

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.