OPTICAL METHOD OF MEASURING THICKNESS OF TRANSPARENT OBJECTS Russian patent published in 2011 - IPC G01B11/06 

FIELD: physics.

SUBSTANCE: method involves generation of laser radiation which is directed onto the measured object using a mirror. Diffuse reflection from the front and rear walls of the object is "collected" by a condenser, one focus of which lies inside the "body" of the object and the other lies on the sensitive area of a photodiode (pin photodiode). The period of starting the laser is initially set equal to its initial period plus the delay time of the rising front of the signal from the photodiode calculated from the rising front of the laser start-up signal. This period is measured through its multiplication and populating the formed time interval with pulses of a standard frequency generator. The same method is used to measure the initial period of starting up the laser. The difference between the measured periods is calculated, which in turn is used to determine the delay time of thee rising front of the signal from the photodiode, calculated from the rising front of the laser start-up signal. The same method is used to calculate the delay time of the falling front of the signal from the photodiode calculated from the falling front of the laser start-up signal. The delay time difference between these two fronts is proportional to the thickness of the measured object. The coefficient of proportionality between the difference between the delay time of the two fronts and the thickness of the measured object are determined by measuring an object with calibrated thickness.

EFFECT: wide range of using non-contact optical methods of measuring physical parametres of transparent objects.

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