A liquid surface height controller for surface spectroscopy

We present a simple and inexpensive liquid surface height controller that can monitor maintain the of in surface-sensitive experiment. The system is based on commercial laser pointer, universal serial bus webcam, syringe pump, homemade control software. sense changes ±1 µm, maximum range device without readjustment around 2.5 mm. intended use to sample at air–water interface sum-frequency generation spectroscopy measurement, which constantly due water evaporation. A demonstration maintaining tolerance ±5 µm over period 8 h shown illustrate stability controlled by this device.