Research On Optical Parameter Characterization Of Microlens Array

Microlens arrays are arranged in a certain order by small lenses ranging in size from a few hundred nanometers to a few millimeters.Due to its two functions of spotlighting and imaging,it is widely used in the current optical field.The optical performance index of the microlens arrays directly affects the performance of the optical system in which it is located,so it is crucial to detect its optical parameters.At present,the optical performance indicators of microlens arrays mainly include: focal length and focal spot size,uniformity,point spread function,wave aberration,diffractive efficiency,scattering rate and transmittance,etc.This paper mainly studies and tests the uniformity and transmittance of the microlens arrays.First,the optical detection system for the distribution uniformity of the microlens arrays is designed and built,and the microlens arrays is sampled and collected from different areas.Then,the uniformity of the microlens arrays was evaluated digitally based on the image processing technology.Finally,an integral transmittance measurement system was built and designed to measure the transmittance of the microlens arrays,and analyze the transmittance of the microlens arrays at three different wavelengths.In this paper,a method for measuring the distribution uniformity of microlens arrays based on image processing is studied in detail.The surface morphology or focal spot of the sample can be used to characterize its homogeneity.When the laser passes through the microlens arrays,each small lens is focused on the focal plane to obtain a set of light spot distributions,and an optical detection system for evaluating the uniformity of the arrays is designed based on the microscopic transmission imaging theory.A micro-trapezoidal structure arrays based on K9 glass and coated with Si O2 thin film is used as the sample to be measured,and the lens arrays has a height of 0.5μm,a base width of 1μm,and a filling ratio of 50%.The microscopic imaging system is designed in combination with the basic parameters of the lens,and the selection of the light source,the microscope objective lens and the photodetector is completed,and then the microscopic imaging optical path is built according to the CCD imaging principle,and the lens arrays distribution diagram is sampled and collected from different areas of the microlens arrays.Based on the digital image processing technology,the uniformity of the microlens arrays is analyzed.First,the correlation,chi-square and Bavarian distance between the standard image and the random area image are calculated based on the histogram comparison,and the defect is determined whether some areas of the microlens arrays are defective.Then,the adaptive Otsu threshold is used to binarize the image,and the edge detection and flood filling algorithm are used to identify light spots.Finally,histogram statistics are used to identify the coordinates and proportion of defects,and the area,variance and uniformity of light spots are calculated.sexual error.Multiple uniformity error values were obtained by sampling and testing different areas of the microlens arrays,and the degree of consistency of the areas was compared,and the uniformity distribution of the microlens arrays was judged with the difference of ±5% as the standard.With the integrating sphere as the core,combined with the relevant detection principle and Labview data acquisition and processing,the integral transmittance measurement system is designed,and the software programming of the acquisition and processing of the corresponding voltage of the transmitted light intensity is completed,and the transmittance measurement of the microlens arrays is realized.The analysis shows that at 405 nm,525 nm and 635 nm,the microlens arrays show a weak decline trend with the increase of laser wavelength,but the change is not obvious,and the transmissivity is about 80%,maintaining a very high transmissivity.