在激光通信、激光制导和交会对接的过程中, 为了实现对远距离目标的捕获和跟踪, 提出了一种基于单元探测器的激光跟踪技术, 该技术以单元探测器测量距离信息, 通过快反镜使光束螺旋扫描视场, 并反馈角度信息, 由此得到三维图像。信号处理端通过处理三维图像可以获取目标相对视场中心的脱靶量, 控制端根据脱靶量驱动快反镜偏转, 使目标一直处于扫描视场中, 从而实现目标跟踪。该技术的优点是能将单元探测器引入到捕获跟踪领域中, 不再需要使用阵列探测器定位回波光斑的中心, 所以回波能量密度更高, 有利于实现远距离的激光跟踪, 特别是能够结合单光子探测器来极大地提高跟踪距离。使用该方法进行了仿真实验, 并在室内使对3.75 m处的目标进行了捕获跟踪实验。实验结果表明, 仿真与实验结果具有很高的一致性, 其中对角速度为9.07 mrad/s目标的捕获概率达到了72.5%。

The spectral properties of entangled photon pairs generated via quasi-phased matching in spontaneous parametric down-conversion are proposed and demonstrated experimentally. A general mathematical model for evaluating the spectral properties is developed to obtain the spectrum shape and range of down-converted photons. The model takes into account the effects of phase mismatching due to non-ideal pumping and the relationship between crystal periodic modulation function and the incidence angle of the pump beam. The spectrum curve shape is determined by the discrete Fourier transform of a Gaussian pump beam and the integration of parametric down-conversion generated by an individual plane wave. An experiment is carried out with a PPLN non-linear crystal and dispersing optics, which shows a good consistency in their spectral ranges and shapes with our model predictions within the spectrum of 600–633 nm. This therefore illustrates that both the simulation model and the experimental process are reasonable. This novel method has potential applications in high-accuracy calibration in the wide spectrum using correlated photons.

The diffractive field distributions of the dark edge on the negative, the edge of the knife and the single edge of the wire were investigated using photo-multiplier system. The results show that the new diffractive formula with the parameters describing the property of the edge of the diffractive object should be established and that the property of the object may be realized by the investigation of the weak diffractive field distribution of the object.