A DUAL CHANNEL PHOTOACOUSTIC CELL FOR IMAGING EXPERIMENTS ON SOLID SAMPLES

摘要

High signal to noise ratio is an important requirement in photoacoustic detection experiments for imaging applications. The present paper describes the design and fabrication of a dual channel photoacoustic cell with two microphones having higher signal to noise ratio than single channel types. The cell has been designed and fabricated as an integral part of a scanning photoacoustic imaging set up. Intensity modulated laser beam is guided to the surface of a sample kept in the cell through a multi mode optical fiber. The signals from the symmetrically placed microphones are summed up after a stage of preamplification in each channel. The resultant signal is fed to a lock-in amplifier for processing. The frequency response of the cell is found to follow theoretical predictions. The cell enables one to perform photoacoustic experiments with better sensitivity and higher signal to noise ratio than single channel ones. When used for photoacoustic microscopy applications, the cell is expected to give better images of surface and subsurface features of solid samples.