High-precision topography measurement of laser-processed PET film
[Objective]With the progress of scientific research on polymer materials,an increasing number of polymer materials are widely used in electronic and mechanical fields such as flexible printed circuit boards,computer floppy disks,and membrane switches.Laser-etched bionic nanochannels are funnel-shaped,conical,etc.The morphology and size of nanostructures,such as thin-film trenches and holes after laser etching have a decisive effect on the performance of the material.Because the thickness and horizontal dimension of the film are very small,generally on the micrometer scale,and the reflectivity of the film is low,it is easily disturbed by imaging noise and other difficulties.[Methods]This paper proposes a parallel object-variance dynamic confocal imaging method for the measurement of thin film etched groove topography,which realizes the high precision of the micro-nano topography of the PET(Polyethylene terephthalate,PET)thin film after laser etching 3D topography measurement.First,the parallel object-variance dynamic confocal three-dimensional measurement system is introduced,which consists of a spatial light modulation illumination light source,a microscope imaging optical system,and a camera using a digital micromirror device(DMD)as the illumination pinhole.Then,the axial differential curve under the 40× objective lens of the parallel object-variance dynamic confocal system was calibrated.The system collected the confocal images of the laser-etched PET film sample at 1.5 μm before and after the focus,and subtracted the two images to obtain a differential image.Based on the previously fitted linear function relationship,the differential image was converted into a 3D topography image.[Results]The system uses a digital micromirror device DMD as the space for the illumination pinhole Light modulation illumination light source,modulates the illumination beam into a point light source array,realizes multipoint fast parallel measurement,and greatly improves the measurement efficiency;For the burr problem on the topography surface in the 3D topography,starting from the optical properties of the PET film,the surface burr in the three-dimensional topography comes from the uneven illumination of the system and the existence of the surface of the PET film itself.To solve the problem of low image contrast in images collected based on parallel confocal imaging system,gray histogram equalization was used to enhance the contrast between processing traces and background in the image,and through image processing technology.The spatial position information of the laser-etched grooves is obtained by means of morphological processing and removal of small connected domains in the confocal image,and then the area(background)outside the laser-processed area in the pre-focus and post-focus confocal images is set to zero to eliminate the influence of complex background with uneven reflectivity on 3D topography restoration;For impurities with low reflectivity,bubbles with high reflectivity,and columnar burrs caused by uneven reflectivity,the template size for differential images is 25*25 nonlinear spatial filter,that is,median filtering technology,eliminates the influence of isolated points with high or low reflectivity on the surface of the film,realizes smoothing of three-dimensional topography,completes line width 3 μm,depth 100 nm,stacking high-precision and fast three-dimensional restoration of the groove morphology of laser-processed thin films with a height of approximately 0.043 μm.[Conclusions]Transparent polymer films have excellent mechanical properties,optical properties,chemical resistance and heat resistance properties and are one of the best choices for the preparation of artificial nuclear pore membrane templates and biomimetic nano-channels.The micropore shapes of nuclear pore membranes prepared by using thin films as raw materials include cylindrical,biconical,ellipsoidal,etc.,and the internal morphology and size information of the pore channels have guiding significance for measuring the porosity and retention effect of nuclear pore membranes.Compared with traditional imaging characterization technology,which is complicated in operation and low in measurement efficiency,this method only needs to collect two images of the sample before and after the focus,and it only takes a few seconds to complete a three-dimensional topography measurement of a laser-etched PET film.For narrow trenches that cannot be measured,the method can still accurately restore topographical dimension information such as the line width and depth of the narrow trenches.The research provides a high-efficiency,high-precision and nondestructive measurement method for the measurement of the morphology of polymer thin films by laser microfabrication.
万方数据
维普
