| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 105 === By through-glass via technique, thermal residual stress will be produced around the drilled hole on glass plates after laser drilling. The glass plate may be cracked due to the large residual stress if the laser manufacturing parameters are not appropriately chosen. Therefore, it is necessary to examine the residual stress of the glass plates after laser drilling. In this thesis, a normal incidence reflective micropolariscope was first built up to measure the residual stress of glass plates after laser drilling.
A normal incidence reflective micropolariscope can be used to measure the residual stress of opaque specimens. However, the variation of the polarization angle of the polarized light caused by the pellicle beam splitter in the system should be considered. Besides, in the microscopic system the captured images may rotate due to the rotation of the analyzer. Therefore, in this thesis the six-step phase shifting technique (PST) which only the polarizer and the quarter-wave plate are rotated was proposed. The calibrated polarization angles of the polarizer were substituted into the six-step PST to eliminate the error caused by the pellicle beam splitter. Moreover, the error caused by pellicle beam splitter using six-step PST and using four-step PST were investigated by simulation.
The accuracy of the micropolariscope was proved by obtaining the approximate phase retardation of the measured quarter-wave plate. Besides, by simulation of measuring specimens with phase retardation of 0.050 rad and 1.558 rad and by measuring the reflection mirror being similar to the zero phase retardation specimen, it was found that the pellicle beam splitter caused significant error when measuring the low phase retardation specimen. Therefore, it is necessary to substitute the calibrated polarization angles of the polarizer into the six-step PST to increase accuracy. Furthermore, because it is less sensitive to the pellicle beam splitter, simulation results showed that six-step PST is more suitable for the normal incidence reflective micropolariscope than four-step PST. Last but not the least, the residual stress of drilled glass plates with different laser scanning fill spacings and different preheating temperatures were measured to determine better laser manufacturing parameters.
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