We present a method to contrast the blood flow of retinal vessels from the surrounding static tissue. It is based on the extinction of the interference fringes by phase shifts of π. If moving particles within the sample introduce an additional phase shift, the signal from these particles will, in contrast to the signal from static tissue, not be attenuated. We demonstrate different variants of this method, where we introduce phase shifts during single A-scans, consecutive A-scans and consecutive B-scans. We show proof-of-principle measurements with a piezo mirror, as well as in-vivo measurements of the human retina for the different phase shifting schemes. We demonstrate its capability to contrast a wide range of perfused retinal vessels; from large vessels present in the optic nerve head region to the capillary network surrounding the fovea.
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