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Optical microstructures are increasingly applied in several fields, such as optical systems, precision measurement, and microfluid chips. Microstructures include microgrooves, microprisms, and microlenses. This paper presents an overview of optical microstructure fabrication through glass molding and highlights the applications of optical microstru...
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... a nitrogen environment. Both approaches of avoiding oxidation have advantages and disadvantages, as shown in Table 2. In addition, seven stations, namely, three heating stations, one pressing station, and three cooling stations, are placed in the PFLF7-60A machine to realize automatic production in the chamber simultaneously. ...
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Citations
... The rationality of the numerical model established by the FEM was verified. Zhou et al. [19][20][21] measured the viscoelastic properties of glass through uniaxial compression experiments. Based on the thermodynamic and viscoelastic parameters obtained from the experiments, finite element simulations of the PGM process were conducted, the stress distribution of the glass was visualized, and the residual stress of the lens was predicted. ...
Precision glass molding (PGM) technology, as an efficient and straightforward method for producing glass lenses, has been widely applied in the mass production of aspheric glass lenses. However, molding complex surfaces such as free-form and array surfaces is still in its infancy. To reveal the variations of temperature and stress of microlens array (MLA) optical elements during the molding process, a simulation model was established using the finite element method (FEM), and the heating and forming stages of a chalcogenide glass MLA optical element were studied. The influence of process parameters on the stress distribution of glass lenses was analyzed. Considering the long heating time and large deformation required for spherical chalcogenide glass preforms, the molding process was optimized. Different loads were applied at various stages of heating and pressurization of the preform, which reduced the stress in MLA optical elements during the molding process and decreased the molding time by over 21%.
... In recent decades, micro-nano three-dimensional surface topography detection has attracted much attention from related researchers due to the surface topography of micronano-structure devices directly determining the physical and chemical properties of the devices [1][2][3]. ...
Structured illumination microscopy (SIM) has attracted much attention from researchers due to its high accuracy, high efficiency, and strong adaptability. In SIM, demodulation is a key point to recovering three-dimensional topography, which directly affects the accuracy and validity of measurement. The traditional demodulation methods are the phase-shift method and Fourier transform method. The phase-shift method has a high demodulation accuracy, but its time consumption is too long. The Fourier transform method has high efficiency, but its demodulation accuracy is lower due to the loss of high frequency information during the process of filtering. However, in actual measurement, due to the gamma effect of the projector and charge-coupled device (CCD), the phase-shift interval is not strictly equal to the default value, which causes phase-shift error. Therefore, the restored topography contains carrier frequency fringes, which affects the accuracy of the measurement and limits the wide application of SIM. In this paper, a novel demodulation algorithm based on spatial-domain carrier frequency shift is proposed to solve the problem. Through recombining multiple full-period phase-shift images, the error spectrum and the signal spectrum are separated from each other in the frequency domain, so as to eliminate the effect of carrier frequency fringes. Simulations and experiments are carried out to verify the feasibility of the proposed method.
... been adopted by many optical manufacturers to fabricate aspherical lenses Aono et al., 2000) and more complex optical components (e.g., micro-lens arrays) (Zhou et al., 2017;Zhou et al., 2002). The high precision in PGM is achieved through the principle of error compensation, that is the form errors in the final glass product are compensated by adding error-compensation profiles in mold designs. ...
Glass with good processability, chemical inertness, and optical transparency has been widely used in optical and aesthetic products, many of which require curve pro-files with high precision. To meet the increasingly tightened geometrical tolerances and fast product updating rates, the traditional approach of developing a thermoform-ing process through trials and errors can cause a large waste of time and resources and often end up with failure. Hence, there is a need to develop an efficient predictive model, replacing the costly simulations or experiments, to assist the design of preci-sion glass thermoforming. In this work, we report a dimensionless back-propagation neural network (BPNN) that can adequately predict the form errors and thus compen-sate for these errors in mold design to achieve precision glass molding. Based on the precision molds, also discussed is the issue of error magnification considering that cover glass for AR/VR glasses or smartphones, with extremely large scale of produc-tion, may require a lower level of mold machining accuracy. It is expected that this BPNN will also be implementable in the glass-manufacturing industry, i.e., trained using industrial data for precision mold designs.
... Another method that has received a lot of attention recently is precision molding, which can be used to transfer micro-nano structures from a mold surface to a fused silica surface. However, this technique can only be applied to replicate the geometry of the mold at a very high temperature (∼1400 deg), and the volume of fused silica is prone to change during the molding process, leading to a reduction in molding accuracy and some material properties [20,21]. ...
Fused silica is the preferred material for applications requiring high temperature resistance, low thermal expansion coefficient and excellent optical properties. The machining of micro-cavities on fused silica surfaces is of particular interest for microfluidic manipulation, mechanical locking, and miniaturization of high-quality optical waveguides, but it still remains technically challenging via traditional manufacturing techniques especially for micro cavities with sharp corners. In the present study, the machining of micro-cavities in fused silica by a femtosecond laser-based method has been investigated numerically and experimentally. The effects of laser machining conditions, including laser power, laser scanning speed, laser incidence angle, and laser-off delay time, on the sidewall slope and bottom surface roughness of the micro-cavities were comprehensively investigated. The results indicated that laser power played a crucially important role in determining the sidewall slope of the micro-cavity, and the laser scanning speed had a significant influence on the bottom surface roughness. Furthermore, the sidewall slope of the micro-cavity was linearly increased as the laser incidence angle increases. By using a laser incidence angle of 10° and a laser-off delay time of 280 ms, a micro-cavity with sidewall slopes close to right angles (10°) was fabricated. This study confirms that femtosecond laser machining is an effective method for fabricating micro-cavities with sharp corners on fused silica surfaces, and the appropriate laser machining conditions should be considered based on practical application scenarios.
... Yi et al. [13] started his research on the glass molding process as early as 2005, using the finite element method to predict the aspheric lens molding process and considering the effects of stress relaxation, structural relaxation, and other properties of the glass on the refractive index of the lens during the cooling stage. The reasonableness of the numerical model established by the finite element method was demonstrated [14][15][16][17][18]. Zhou et al. [19][20][21][22] measured the viscoelasticity of glass by uniaxial compression experiments using an ultra-precision glass molding machine. The elastic modulus and viscosity of the glass were obtained by curve fitting for creep and stress relaxation using the Burgers and Maxwell models, respectively. ...
Precision glass molding (PGM) technology, as an effective method for mass-producing glass lenses, is relatively mature in the molding process of aspheric lenses, but the glass molding technology for freeform optical elements is still in its infancy. For freeform optical elements, processing by conventional ultra-precision methods requires multiple processes and the resulting costs are high, while processing by PGM is efficient and inexpensive. Therefore, this paper investigates the molding technology of freeform lenses, the pre-compensation model of the freeform mold core is established, and predicts the residual stresses of freeform lenses after molding by the finite element method. Three different process parameters, molding temperature, molding rate and molding force, are verified. Experimental and simulation results show that the trends of residual stresses for the three process parameters are consistent. The optimal process parameters of the molding process are determined, under which the PV value of the molding lens is around 1.5µm. The experimental results show that the PV value of the molded lens is reduced to less than 1µm after using the pre-compensated mold core, which proves the validity of the pre-compensated model.
... Flanges are welded, bolted, or lapped together and are the second most frequent connection method after welding. They are commonly used in pipeline operations to connect valves, pipes, link pumps, and other components of a piping system [24]. ...
A coupling is a mechanical element that allows one shaft to transfer its rotational energy to another shaft located at a great distance while maintaining a constant rotational speed. Flange coupling is a method of delivering power between two shafts by connecting their ends with flanges. The rigid flange coupling was created for use with gear units positioned on a horizontal shaft. The difficulty of improving the strength-to-weight ratio of a component is shared by all modern manufacturing sectors. This paper entails the reduction of flange coupling weight. The flange is made out of composite steel, which is both lightweight and has excellent thermal and mechanical qualities. The flange coupling design in this paper was optimized using Finite Element Analysis. Autodesk Fusion 360 and AutoCAD were used to create the flange coupling’s design, as well as the static structural analysis and the subsequent stress and deformation calculations. Significant progress can be made in the early stages of development thanks to the findings of the Finite Element Analysis. The primary goal of this effort is to minimize the material cost by decreasing the weight of the flange coupling without compromising its performance.
... Surface topography characterization is pivotal for extracting information about the functionalities of a material with a micro-or nanostructured surface due to the steady maturation of microstructures instrument and the ongoing expansion of linked industries [1][2][3][4]. Especially, in applications like silicon micropillars, micro-grids, and micron-scale step gratings [5][6][7], surface topography significantly influences the microstructures' performance [8]. With the continuous advancement of micro and nano technology, characterizing micron-scale structure with a wide field-of-view (FOV), high resolution, and high precision is significant for evaluating manufacturing technology and performance testing. ...
Topographic measurements of micro- or nanostructures are essential in cutting-edge scientific disciplines such as optical communications, metrology, and structural biology. Despite the advances in surface metrology, measuring micron-scale steps with wide field of view (FOV) and high-resolution remains difficult. This study demonstrates a dual-wavelength Fourier ptychographic microscopy for high-resolution topographic measurement across a wide FOV using an aperture scanning structure. This structure enables the capture of a three-dimensional (3D) sample's scattered field with two different wavelength lasers, thus allowing the axial measurement range growing from nano- to micro-scale with enhanced lateral resolution. To suppress the unavoidable noises and artifacts caused by temporal coherence, system vibration, etc., a total variation (TV) regularization algorithm is introduced for phase retrieval. A blazed grating with micron-scale steps is used as the sample to validate the performance of our method. The agreement between the high-resolution reconstructed topography with our method and that with atomic force microscopy verified the effectiveness. Meanwhile, numerical simulations suggest that the method has the potential to characterize samples with high aspect-ratio steps.
... Standard lithography can be used to create structures similar to the one shown in Figure 1c, which requires multiple intermediate steps for creating a mask, curing and baking photoresist, etching, etc. The prisms, although not particularly difficult to fabricate [63], are quite bulky and impractical for on-chip integrated thin devices. ...
Fundamental limits of thermal radiation are imposed by Kirchhoff’s law, which assumes the electromagnetic reciprocity of a material or material system. Thus, breaking reciprocity can enable breaking barriers in thermal efficiency engineering. In this work, we present a subwavelength, 1D photonic crystal composed of Weyl semimetal and dielectric layers, whose structure was optimized to maximize the nonreciprocity of infrared radiation absorptance in a planar and compact design. To engineer an ultra-compact absorber structure that does not require gratings or prisms to couple light, we used a genetic algorithm (GA) to maximize nonreciprocity in the design globally, followed by the application of the numerical gradient ascent (GAGA) algorithm as a local optimization to further enhance the design. We chose Weyl semimetals as active layers in our design as they possess strong, intrinsic nonreciprocity, and do not require an external magnetic field. The resulting GAGA-generated 1D magnetophotonic crystal offers high nonreciprocity (quantified by absorptance contrast) while maintaining an ultra-compact design with much fewer layers than prior work. We account for both s- and p-polarized absorptance spectra to create a final, eight-layer design suitable for thermal applications, which simultaneously minimizes the parasitic, reciprocal absorptance of s-polarized light.
... Fabricating large-area glass grooves with diverse profiles remains a significant challenge owing to glass's hard, brittle physical characteristics, and low heat conductivity resulting in heat and stress concentration. Glass groove fabrication can utilize additive 6,7 , formative 8,9 , and subtractive manufacturing methods. Three-dimensional printing, as an additive manufacturing approach for glass structuring, offers high shape design flexibility. ...
... Fabricating large-area glass grooves with diverse profiles remains a significant challenge owing to glass's hard, brittle physical characteristics, and low heat conductivity resulting in heat and stress concentration. Glass groove fabrication can utilize additive 6,7 , formative 8,9 , and subtractive manufacturing methods. Three-dimensional printing, as an additive manufacturing approach for glass structuring, offers high shape design flexibility. ...
