Method and apparatus for correcting responsivity variation in photothermal imaging

The disclosure is directed to a method and apparatus for correcting responsivity variation in photothermal imaging. The method includes sending, during a first time period, light-driving signal to a light source so that the light source is configured to output a series of light pulses onto a sample, wherein the sample is under photothermal-induced expansion according to the series of light pulses. The method includes obtaining, during the first time period, first deflection signal from a cantilever. The method includes sending, during a second time period, actuator-driving signal to an electromechanical actuator so that the electromechanical actuator is configured to move according to the actuator-driving signal, wherein the electromechanical actuator is coupled with the sample. The method includes obtaining, during the second time period, second deflection signal from the cantilever and obtaining a photothermal image of the sample based on the first deflection signal and the second deflection signal.