A method for adjusting an optical axis of an imaging optical system is provided. A sample containing carbon nanotubes is positioned in a microwave cavity at a location corresponding to a maximum in the electric field component of a stationary wave having a microwave frequency. The circuit board receives an unlocking signal and starts the motor to rotate reversely together with the actuating member, letting the passive member moved inward by the recovering resilience of the spring and the deadbolt disengaged from the insert groove of the engage base to finish unlocking of the lock. A rating of at least one category within any one level of the hierarchy is received.