A method and system for capturing images of a liquid sample flowing through a field of view of an imaging device that can include stepping a focus mechanism of the imaging device through a plurality of focus values and capturing a plurality of images of the sample at each of the plurality of focus values as the sample flows through the field of view of the imaging device. In this way, image capture can proceed before a focus value has been determined and capture images that are in focus can be used for further processing subsequently.