METHOD AND DEVICE FOR MEASURING CONCENTRATION OF OPTICALLY ACTIVE SUBSTANCES IN CLOUDY SOLUTIONS Russian patent published in 2008 - IPC G01N21/21 

FIELD: physics.

SUBSTANCE: method of measuring concentration lies in that, in the cell with the optically active substance is placed between linear polarizers, the transmission planes of which differ by a ±45° angle. One of the polarizer is simple, and the other transmits two light beams with mutually orthogonal polarisation planes with intensities J₁ and J₂. The signal is controlled by the difference in light intensity J₁-J₂ and the simple polarizer is turned from the initial Θ=0 to angle Θ=α_λ which is equal to the angle of rotation of the polarisation angle in the cell of the substance, for which the difference J₁-J₂ equals zero. The simple polarizer is left in that position, the cell with the test substance is removed from the light, and then depending on the ratio of the difference to the sum of the intensities of the light beams J₁ and J₂, the rotation angle of the simple polarizer Θ=α_λ is determined. That result is multiplied by a coefficient M, which takes into account the length of the cell L and specific rotation of the substance. The device for implementing the technique consists of light source, cell with the test substance, which is put between linear polarizers, the transmission plane of which differ by ±45°, one of them is in the form of a Wollaston prism, which transmits two light beams, two photo-detectors, two amplifiers, shaping units of the difference and sum of signals U₁ and U₂, a unit for determining the ratio of the difference to the sum of these signals. The shaping unit of the signal differences, through the switch contacts, installed where the cell is located, and through an electronic switch, is connected to an amplifier, synchronous detector, and threshold device with two indicators. The simple polarizer is on the right side, joined with a mechanism for angular displacement. Between the light source and the simple polarizer there is a circular polarizer.

EFFECT: elimination of measuring errors.

2 cl, 6 dwg