Measurements of size and absorption coefficient of a single moving particle by using dual burst Doppler signal

•Modified LDV method is proposed for measuring absorption coefficient of a particle.•The proposed method employs only a single photodetector.•The optimum conditions of an optical system are estimated theoretically.•Experimental results show the feasibility of the proposed method.

Modified LDV method is proposed for measuring the diameter and absorption coefficient of a single moving particle by applying the Lambert–Beer’s law to dual burst Doppler signal. The diameter and absorption coefficient of a particle are determined simultaneously from the time difference and intensity ratio between burst components of reflected and refracted rays in a dual burst Doppler signal, using only a single photodetector. This method can be applied to a particle larger than the cross-sectional area of an illuminating beam. The optimum conditions of an optical system were estimated theoretically. Experiments were performed with polystyrene particles in water, water droplets, and water-black ink droplets to confirm usefulness of the proposed method.