光学成像因其分辨率高，信息量丰富，具有其他探测和感知技术不可替代的地位，是人们获取信息最重要的技术手段之一。光子是光学成像系统中的信息载体。光学图像的高质量重构，依赖于对信号光子的高效耦合和对光信息的精准解耦。然而，在遥感或生物成像等重要应用场景中，由于作用距离远或辐照功率低，到达探测面的物体信号光子数少，信噪比低，对光学系统设计、信号探测和图像恢复都带来了极大困难，严重限制了光学成像性能。如何在极弱光条件下获得高质量图像，是光电成像系统研究的基础性难题，也是推动光学成像不断向更大视场、更远作用距离、更高信息通量发展亟待克服的关键技术。近年来，在光场调控和量子探测技术支撑下，并基于光场的高阶经典/量子关联发展起来的关联成像，由于探测灵敏度高、抗干扰能力强，为发展极弱光条件下的光学成像技术带来了新的机遇。文中将简要回顾关联成像的原理机制，在此基础上系统介绍极弱光条件下关联成像方案和方法。并尝试从光子动力学层面解释这些方法的物理本质，讨论这些方法的能力极限，比较这些方法所适用的场景。

Applications of ghost imaging are limited by the requirement on a large number of samplings. Based on the observation that the edge area contains more information thus requiring a larger number of samplings, we propose a feedback ghost imaging strategy to reduce the number of required samplings. The field of view is gradually concentrated onto the edge area, with the size of illumination speckles getting smaller. Experimentally, images of high quality and resolution are successfully reconstructed with much fewer samplings and linear algorithm.

Correlation imaging is attracting more and more attention as a novel imaging technique taking advantage of the high-order coherence of light fields. To reconstruct an image of the object, many frames of different speckle patterns are required. Therefore, the speed of imaging is strongly limited by the speed of the refreshing rate of the light field. We propose a coprime-frequencied sinusoidal modulation method for speckle pattern creation using a spatial light modulator in a computational ghost imaging system to increase the speed of imaging. The performance of the proposed method is discussed as well.