Non-contact optical hand-held viscosity sensor with incident angle and irradiation timing controls.

This paper proposes a novel optical hand-held viscosity sensor based on a laser-induced capillary wave method that can be used as a noncontact and quick in situ viscometry of liquid samples. Incident angle and irradiation timing control systems were integrated into the hand-held viscosity sensor to robustly measure viscosity by detecting the optical signal in a hand-held condition. We report the stability evaluation of these systems under the hand-held condition. Finally, the proposed sensor's applicability to the hand-held viscometer was confirmed by measuring the viscosity distribution that the temperature gradient of the liquid sample caused.