Research On Morphology Detection Technique Of Dual-wavelength Digital Holography Micro-optical Elements

Micro-optical elements are a common type of miniaturized optical elements,and in recent years,with their increasing range of applications,the production and variety of micro-optical elements have also increased.Therefore,the detection of the three-dimensional morphology of micro-optical elements has become increasingly important.Digital holography technology,with its advantages of non-destructive measurement,full-field imaging,and real-time measurement,has been widely used in the field of micro-optical component morphology detection.However,traditional digital holography technology cannot measure stepped samples in which the optical path difference between adjacent pixels exceeds the wavelength of the laser.Dual-wavelength digital holography technology can effectively solve this problem.The dual-wavelength digital holography was in this paper for further study.The main work is as follows:The relevant theory of dual-wavelength digital holography for measuring the threedimensional morphology of micro-optical elements.This includes the principles of interference recording,diffraction reproduction,dual-wavelength digital holographic morphology measurement,and phase reconstruction in digital holography.Simulation of the three-dimensional morphology of micro-optical elements using dualwavelength digital holography.MATLAB is used to simulate the measurement of stepped objects and continuous surface objects with an optical path difference between adjacent points exceeding a single wavelength.The measurement results have good consistency with the standard values,proving the feasibility of the dual-wavelength digital holography algorithm for measuring such objects.Measurement of the three-dimensional morphology of micro-optical elements using dualwavelength digital holography.A device is designed for the detection of micro-optical element morphology using dual-wavelength digital holography.The synthesized wavelength of the device is 4950 nm,composed of lasers with wavelengths of 450 nm and 495 nm.The Michelson interferometer is used in the interference optical path.When using a 10 x microscope objective,the lateral resolution is 5.52μm,and the relative error in the vertical direction is 8.98%.The device is used to measure stepped samples,and the measurement result of 2206.8nm is basically consistent with the standard value of 2025 nm,proving that the device can realize the detection of stepped samples.A algorithm is proposed to effectively suppress noise amplification in dual-wavelength digital holography.The algorithm uses the traditional dual-wavelength algorithm to recover the morphology information.The recovered morphology result is subtracted from the fitting value to obtain the noise value.Since the amplification factor of the noise is a known value,the amplification of the noise can be eliminated.The algorithm is applied to the measurement of standard stepped samples.The recovered height of 2109.1nm is compared with the height of2206.8nm recovered by the traditional dual-wavelength algorithm.The results show that the relative error is reduced from 8.98% to 4.17%.It was verified that the algorithm can effectively suppress noise and improve the measurement accuracy of stepped samples.