Method and apparatus for correcting responsivity variation in photothermal imaging

An apparatus for correcting responsivity variation in nanoscale photothermal imaging, the apparatus comprising:

• a memory storing instructions;
• and
• a processor in communication with the processor, when the processor executes the instructions, the processor is configured to cause the apparatus to:
• send, 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,
• obtain, during the first time period, a first deflection signal from a cantilever, wherein the cantilever is configured to interact with the sample,
• send, during a second time period, an 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,
• obtain, during the second time period, a second deflection signal from the cantilever, and
• obtain a photothermal image of the sample based on the first deflection signal and the second deflection signal.