SPOT ERROR HANDLING FOR FOCUS TRACKING

Some implementations of the disclosure relate to an imaging system including one or more image sensors and a Z-stage. The imaging system is configured to perform operations including: capturing, using the one or more image sensors, a first image of a first pair of spots projected at a first sample location of a sample; determining whether or not the first image of the first pair of spots is valid; and when the first image is determined to be valid: obtaining, based on the first image, a current separation distance measurement of the first pair of spots; and controlling, based at least on the current separation distance measurement, the Z-stage to focus the imaging system at the first sample location.