We advance a protocol to measure the complex spatial degree of coherence of a partially coherent light field obeying Gaussian statistics through a generalized Hanbury Brown and Twiss (HBT) experiment. The proposed generalized HBT experiment amounts to combining a partially coherent field with a pair of coherent reference fields and measuring the intensity-intensity cross-correlation of the cumulative field. The real or imaginary part of the complex spatial degree of coherence can be extracted directly from the intensity-intensity cross-correlation by adjusting the phase delay between the two reference fields to be $0$ or $\pi /2$. We test our method by carrying out a proof-of-principle experiment to measure the complex spatial degree of coherence of inhomogeneous light fields obeying Gaussian statistics. We find excellent agreement between the experimental results and our general theory. We show that our approach is extremely robust against the environment fluctuations (e.g., the atmospheric turbulence) during the measurement. We demonstrate experimentally that a moving target hiding behind a ground glass disk can be tracked with the aid of our complex spatial coherence measurement protocol.

中文翻译：

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用广义Hanbury Brown和Twiss实验测量随机光场的复杂相干度

我们提出了一个协议，通过广义汉伯里·布朗和特维斯（HBT）实验来测量服从高斯统计的部分相干光场的复杂空间相干度。提出的广义HBT实验等于将部分相干场与一对相干参考场合并，并测量累积场的强度-强度互相关。通过将两个参考场之间的相位延迟调整为，可以直接从强度-强度互相关中提取复杂空间相干度的实部或虚部。$0$ 要么 $\pi /2$。我们通过进行原理证明实验来测试我们的方法，以遵循高斯统计来测量不均匀光场的复杂空间相干度。我们在实验结果和一般理论之间找到了极好的一致性。我们证明了我们的方法在测量过程中对环境波动（例如，大气湍流）具有极强的鲁棒性。我们通过实验证明，借助我们复杂的空间相干性测量协议，可以跟踪隐藏在玻璃磨盘后面的移动目标。