A Laser Precision Liquid Level Sensor

A beam of He-Ne laser light will, on encountering a two-phase fluid menisci, be deflected from its normal straight line path by up to 90 degrees. This is caused by an effective liquid prism synthesized by the liquid menisci bifurcation contour. This phenomena can be used to good effect in sensitive liquid volume measurements. Volume measurement sensitivities of the order of 0.0001 percent or better are achievable. Applications include menisci position sensing in the calibration of scientific glassware, eliminating the use of expensive and dangerous mercury. Calibration accuracies can be increased by three to four times over that given by existing techniques. Precision volume reliquification of freeze dried biological samples, by laser marking at the original liquid level, can enhance the accuracy of clinical test results by eliminating a major source of technician error.