A Study Of Linearity Measurement Method Based On Magneto-optic Linear Modulation

Straightness is one of the important items in geometry measuring, which is combined with roundness and parallelism to be called three essential measuring items. Presently, the accuracy in roundness, parallelism and roughness have achieved the grade of sub-micron and even nanometer in the world, but straightness is not so precise. Especially, in the field of measuring straightness of greater dimension, the level of straightness is trailed by the other measuring items out and away.At present, long optical flat is still mainly adopted as calibrating benchmark in straightness measurement, whose accuracy is not so high (especially in measuring great-size parts). Such status restricts our country's developing step in the field of accurate measurement. Meanwhile, the way advanced previously that the collimation beam of light acts as illuminant and the four quadrant photocell as receiver is not applied practically. Moreover, laser interferometer is too expensive to be extended. Therefore, we cry for a measuring way which is simple, economical, effective and accurate. Based on the requirement, a new method of measuring straightness has been advanced, which is founded on Faraday Magneto-optical Effect, and translate the linearity changes into the phasic changes of polarized light, and then measure the phasic changes via follow-up optical path and numerical phase detector circuit whose core is microcontroller, and finally work out the straightness using the given relationship between phase and straightness. Based on the principle, the total design blueprint was advanced, and the Magneto-optic modulator was designed, and also the circuit and software. A suit of measuring system was established, and some related experiments was done, and experimental data was processed and analyzed.A new method of linearity measurement based on magneto-optic linear modulation is put forward in this paper, which offers a new idea for measuring straightness, provided with good reference and practicality. The result of experiment indicates that the method is a feasible way which is worth developing and studying further.