Research On Naked-eye 3D Printing Technology Based On Microlens Array

The naked-eye 3D printing technology based on microlens array can achieve the naked-eye 3D display effect within 3600 full angle without the help of glasses,helmet and other visual aids or observation skills.It can significantly improve the information display level,interest and anti-counterfeiting performance of the product,increase the visual impact and sensory experience of the product,and greatly enhance the added value of the product,which has significant engineering application values in the fields of printing,publishing,anti-counterfeiting,decoration,display,etc.However,the naked-eye 3D printing technology based on microlens array currently lacks the necessary theoretical analysis method of moire display,which embody in the following aspect:the existing methods only focus on the array magnification features of moire pattern,ignoring the spatial direction features and unit magnification features of moire pattern.Secondly,the existing naked-eye 3D display based on microlens array is mostly the display effect of monochrome or polychromatic color block,which can not achieve true color 3D display effect with different tone and gradation changes.In addition,due to the high cost,low efficiency and inability to quick respond to production tasks,the large-scale commercial application of naked-eye 3D printing technology based on microlens array is limited.Aiming the above issues,the main research contents and conclusions are listed as follows.(1)On the basis of the existing geometric transformation method,a moire display theoretical analysis method was proposed for microlens array with regular hexagonal aperture and honeycomb arrangement,which gave consideration to the imaging characteristics of moire pattern,such as periodic amplification,unit amplification and spatial direction.The mathematical relationship between the period,direction angle,period magnification,unit magnification of moire pattern and the period of microlens array,the period of micrographics array,as well as the superposition angle of them were derived in detail.(2)The five typical cases were selected,the period of the micrographics array is equal to that of the microlens array,the period of the micrographics array is slightly less than that of the microlens array,the period of the micrographics array is slightly greater than that of the microlens array,the period of the micrographics array is twice that of the microlens array,the superposition angle of the micrographics array and the microlens array is 0°,the period of the microlens array is constant,but the period of the micrographics array changes within a certain range.The computer simulation and analysis of the relationship between the period,direction angle,period magnification and unit magnification of moire pattern with the period of microlens array,the period of micrographics array,as well as the superposition angle of them were carried out by using Matlab.(3)An integrated technology of naked-eye 3D printing based on microlens array was proposed,which was a combination of the roll to roll UV-LED nanoimprinting technology and the high-resolution UV offset printing technology.The nanoimprint manufacturing process of microlens array optical film and UV offset manufacturing process of micrographics array were introduced in detail.The influence of pet substrate performance,UV-LED imprint photoresist performance,imprint force and imprint speed on the manufacturing quality of microlens array optical film were studied and analyzed.The influence of CTP publishing resolution,printing speed and printing pressure on the manufacturing quality of micrographic array were studied and analyzed.The results show that the PET film has good surface smoothness and light transmittance,which is very conducive to the fabrication of microlens array and the presentation of excellent optical properties of microlens array optical film.The imprint photoresist has low viscosity,good interface properties and small curing volume shrinkage,which is very beneficial to the filling of mold groove and the molding and demoulding process of microlens array.For the nanoimprint manufacturing of microlens array optical film:it is necessary to ensure that the imprint force is large enough to make the photoresist fully fill the mold groove,and to avoid the extrusion deformation of the microlens array structure caused by the excessive imprint force,which leads to the damage of the mold.When the imprinting speed is controlled at 5 m/min-7 m/min,the replica accuracy of microlens array is high and the forming quality is stable,and there is no bubble defect or break defect.For UV offset printing of micrographics array:with the increase of publishing resolution,the micrographics become more delicate,and dot gain and other graphic deformation phenomena are less obvious.The publishing accuracy of micrographics array should generally be above 12800 dpi.When the printing speed is controlled at 20 m/h-30 m/h,the printing pressure is controlled at 0.05 Pa-0.15 Pa,the printing quality and naked-eye 3D display effect of the micrographics array are relatively the best.(4)The two typical cases were selectes,and the theoretical and experimental values of the period,the direction angle,the period magnification and the unit magnification of moire pattern were calculated and tested respectively.The differences between the theoretical and experimental values were then compared.The results show that the deviation rates between the experimental and theoretical values of the period,the direction angle,the period magnification and the unit magnification are all less than 2%in two typical cases,which verifies the effectiveness of the moire display theoretical analysis method in the third chapter.(5)A novel design and production method of true color 3D printing micrographics based on microlens array was proposed,that is,a combination of the microstructure halftone processing technology and the micrographics array processing technology.The new design and production method can make the repetitive 3D array elements have different sizes and colors,and more importantly,can present the true color 3D display effect with different tones and gradation changes.(6)The application of the integrated technology can achieve fine naked-eye 3D display effect,improve the efficiency of engineering application by about 90%,reduce the cost by about 33%,and respond to the production task quickly with high flexibility.