1. A method of imaging, comprising: scanning a sample with an incident beam from a light source; detecting one or more spectral interference signals from the sample and a reference mirror; modulating the one or more spectral interference signals at a constant frequency while scanning the sample in a cross-sectional direction (B scan); and obtaining at least one image of the sample from the modulated one or more spectral interference signals, the at least one image including a full range structural image of the sample or a separated structure/flow image of the sample.