Corbett, W.J. Huang, X. Li, C.L. Mitsuhashi, T.M. Wu, J. Xu, Y.H. Zhang, W.J. JACoW Geneva, Switzerland 978-3-95450-177-9 10.18429/JACoW-IBIC2016-MOPG70 English 237-240 MOPG70 controls electron coupling optics radiation Contribution to a conference proceedings 2017 2017-02 http://dx.doi.org/10.18429/JACoW-IBIC2016-MOPG70 http://jacow.org/ibic2016/papers/mopg70.pdf Double-slit interferometers are useful tools to measure the transverse the cross-section of relativistic charged particle beams emitting incoherent synchrotron radiation. By rotating the double-slit about the beam propagation axis, the transverse beam profile can be reconstructed including beam tilt at the source. The interferometer can also be used as a sensitive monitor for vertical emittance control. In this paper we outline a simple derivation of the Van Cittert-Zernike theorem, present results for a rotating double-slit measurement and demonstrate application of the interferometer to vertical emittance control using the Robust Conjugate Direction Search (RCDS) optimization algorithm.