Fig. 1. Process chains for manufacturing aspheric optical elements

Fig. 2. PGM schematic diagram. (a) Heating stage; (b) Pressurizing stage; (c) Annealing stage; (d) Cooling stage

Fig. 3. Optical glass materials^[15]. (a) Optical glass blanks; (b) HWS series sulfur-based infrared glass; (c) Precision glass molded aspheric lenses

Fig. 4. Mold materials for molding technology^[16]. (a) Tungsten carbide material; (b) Microcrystalline aluminum material

Fig. 5. Single point diamond turning process^[20]. (a) Single point diamond turning; (b) Moulding concave core; (c) Moulding convex surface

Fig. 6. Glass molding simulation^[25]. (a) Heating of glass preforms and molds to a molding temperature of 700℃; (b) Molding of preforms at constant temperature; (c) Annealing of molded lenses

Fig. 7. Refractive index change distributions of P-SK57 glass cylinder and P-LASF47 glass cylinder cooled at different rates^[25]

Fig. 8. Temperature distributions of glass preforms at different heating times^[31]. (a) 120 s; (b) 180 s; (c) 220 s

Fig. 9. Stress-strain diagram in conventional glass forming distribution^[32]. (a) Stress distribution; (b) Strain distribution diagram

Fig. 10. Stress-strain diagram in two-step glass forming ^[32]. (a) Stress distribution; (b) Strain distribution diagram

Fig. 11. Simulated stress results for molded lenses^[33]. (a) Equivalent stress on the lens surface 1; (b) Shear stress σ_yzin the cross section

Fig. 12. MATLAB plotted temperature clouds of the mold, core, and glass preforms^[34]. (a) Initial temperature; (b) Final temperature

Fig. 13. Temperature clouds of the mold, core, and glass preforms plotted by MSC.Marc software^[34]. (a) Initial temperature; (b) Final temperature

Fig. 14. Development of precision glass molding technology

Fig. 15. Adhesion of sulfide glass to the surface of a mold coated with Re-Ir^[42]. (a) Mold surface before molding; (b) The surface of the mold after molding at 330 ℃ ; (C) The surface of the mold after molding at 340 ℃

Fig. 16. Results of cylindrical glass molding at molding temperatures between 352 ℃ and 392 ℃ and pressures of 1362 N^[49]

Fig. 17. Surface images of molded sulfur-based glass lenses^[50]. (a) Lens 1; (b) Lens 2

Fig. 18. Physical picture of the molded lens. (a) D-K9 glass^[51] ; (b) Sulfur glass^[52]

Fig. 19. Change of refractive index of Ge₂₈Sb₁₂Se₆₀ and As₄₀Se₆₀ samples after heat treatment^[53]

Fig. 20. Distribution of refractive index variation at different cooling rates^[30]. (a) 360 K/h; (b) 180 K/h; (c) 90 K/h; (d) 36 K/h

Fig. 21. Statistical distribution of refractive index changes^[54]

Fig. 22. Self-developed ultrasonic vibration-assisted molding machine^[56]

Fig. 23. Principle of injection molding process. (a) Plasticizing stage; (b) Injection stage; (c) Holding stage; (d) Cooling stage; (e) Mold opening and unmolding

Fig. 24. Refractive index distribution of optical plastic materials^[16]

Fig. 25. Percentage light transmission of optical grade polymers^[16]

Fig. 26. Precision optical plastic injection molding system^[66]. (a) A mold mounted on an injection molding machine; (b) A three-dimensional model of the mold

Fig. 27. Precision injection molding mold processing^[68]. (a) Ultra-precision machine; (b) Mold insert after cutting

Fig. 28. The MOLDFLOW software simulates the injection molding technology of aspheric surfaces^[70]. (a) Flow channel system; (b) Initial parameters face shape accuracy; (c) Optimized process parameters

Fig. 29. Moldflow software simulates the residual stress magnitude on different lens surfaces^[72]. (a) Front surface; (b) Back surface

Fig. 30. Residual stress and birefringence distribution of optical components^[74]. (a) Simulation and comparison of maximum residual stress of PC optics; (b) Simulation and experimental comparison of residual stress distribution of optical components

Fig. 31. Optical quality optimization results by numerical simulation ^[75]. (a) Lens warpage distribution; (b) Optical path difference

Fig. 32. Simulation model current limiter design and short-shot experiment ^[77]. (a) Dimensional parameters of restrictor; (b) Runner with restrictor for 4-cavity mold; (c) Velocity field plot for original runner; (d) Velocity field plot for runner with restrictor; (e) Short-shot simulation; (f) Results of short-shot experiments

Fig. 33. Design of the mold runner^[78]. (a) Schematic plot for temperature distribution of the melt at the intersection of runners; (b) Temperature distributions of the melt in runner, gate and mould cavity during the filling

Fig. 34. Details of the iteration loop for machining a high precision freeform surface on the mold^[79]. (a) Surface deviation before iteration loop, 3D view; (b) Surface deviation before iteration loop, top view; (c) Fitted Fourier function as error description of the surface deviation; (d) Error between fitted deviation and found mathematical description; (e) Surface deviation after one iteration loop, 3D view; (f) Surface deviation after one iteration loop, top view

Fig. 35. Microphysical structure of crystalline Ni-P produced after heat treatment^[68]

Fig. 36. Precision shape accuracy after injection molding^[68]. (a) Mold core without heat treatment; (b) Mold core after heat treatment

Fig. 37. Schematic of the injection molding and injection compression molding^[88]. (a) Fill stage; (b) Injection compression molding is a compression operation by adding a mold core

Table 1. Comparison of manufacturing techniques of aspherical optical elements

Table 2. Precision glass molding technology processing components

Table 3. Precision injection molding technology processing components