Calcium indicator dyes have led to the advent of time lapse microscopic techniques for the study of neuronal and neural circuit function (Tsien, 1981; Grynkiewicz et al., 1985). After loading these dyes into populations of neurons, experimenters are able to measure action potential generation in neuronal ensembles via their fluorescence (Yuste and Katz, 1991; Smetters et al., 1999; Goldberg and Yuste, 2009). Such imaging was initially performed using wide-field excitation, that is, simply bathing the whole field of view in large amounts of excitation light and imaging fluorescent emission with a camera as a detector (Yuste and Katz, 1991; Smetters et al., 1999). This is straightforward and easy to instantiate but provides limited spatial resolution of imaging, especially in the direction parallel to the optical axis (axial or Z-resolution as referred later).