the invention describes a method for measuring a property of a sample by : 1 ) irradiating a portion of the sample with an excitation pattern characterized by at least one spatial phase and spatial period ; 2 ) diffracting a portion of a probe beam off a surface of the sample ; 3 ) detecting the diffracted portion of the probe beam with an optical detector to generate a light - induced signal ; 4 ) adjusting the spatial phase of the excitation pattern ; 5 ) repeating the irradiating , diffracting and detecting steps to generate an additional light - induced signal ; and 6 ) processing the light - induced signals to determine a property of the sample .