Microregion Stress Measurement Technique Based on Microscopic Technique
Microregion stress is a prevalent issue in printed-circuit board welding,transparent conductive-film plating,and micro-optical system assembly and will reduce the performance and operation safety of devices.Existing stress measurement systems are suitable for large-scale optical materials but cannot be used for microregion stress measurements.To solve the problem of noncontact and nondestructive measurement of microregion stress,a microregion stress measurement scheme based on microscopic technology was proposed.The proposed scheme integrated an optical stress measurement system based on polarization with a micro-imaging microscopic system,which could realize stress measurement at the transverse scale of millimeter or submillimeter.Taking the 2.3%relative error measurement accuracy requirement of the national standard GB/T 7962.5-2010 as an example,the system design and component error analysis of the measuring device were performed.To validate the theoretical design and measurement scheme,a set of devices was constructed for measuring stress distribution in the microregion.The device operated at a working wavelength of 532 nm with a microscopic objective power of 50×and a corresponding theoretical spatial resolution of 0.59 μm.A zero-order 1/4 wave plate working at 532 nm with a phase delay value assigned by the measuring department was the measuring object.The diameter of the measuring area was 0.96 mm,and the phase delay was 1.595 rad.Comparison with the testing result of the China Institute of Metrology 1.604 rad,the absolute error is 0.009 rad,and the relative error is only 0.6%,thereby verifying the measuring accuracy of the measuring device.Using this device,the phase distribution of quartz glass was measured in different measurement areas under different prepressures.The results show that the measurement error of this method is within 1%and there are small regional stresses that cannot be resolved by the measuring system.
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