Spherical lenses have constant curvature from the center of the lens to the edge, whereas Aspheric lenses have continuous curvature changes from the center to the edge.Many aberrations must be corrected to ensure optical performance,If only a spherical lens is used for correction, then pieces of spherical lenses will be needed. Aspheric lenses, whose curvature changes with the central axis, are used to improve optical quality, reduce optical components and reduce optical costs. Aspheric lenses have unique advantages over spherical lenses.
Calculation formula in optical design:
1, technical principle
Aspheric lenses, whose curvature radius varies with the central axis, are used to improve optical quality, reduce optical components and reduce design costs. Aspherical lenses have unique advantages over spherical lenses, so they are widely used in optical instruments, images and industries, such as digital cameras, CD players and high-end microscopic instruments.
2. Comparative advantage
A Spherical aberration is used to calibrate aspheric lenses to replace spherical lenses. The most significant advantage is that spherical aberration caused by spherical lenses in collimation and focusing systems can be corrected.By adjusting surface constant and aspheric coefficient, aspheric lens can eliminate spherical aberration to the maximum extent. Aspheric lenses (where light rays converge at the same point, providing optical quality) essentially eliminate spherical aberration (where light rays converge at different points, resulting in blurred images) caused by spherical lenses.Three spherical lenses are used to increase the effective focal length and eliminate spherical aberration.However, an aspheric lens (high numerical aperture, short focal length) can be achieved, simplifying system design and providing light transmittance.B System advantage Aspheric lenses simplify the elements involved by optical engineers in order to improve optical quality, while improving system stability.In zoom system, for example, typically 10 or more of the lens is made (additional: high mechanical tolerance, extra assembly process, improve the antireflective coating), but 1 piece or 2 piece aspheric lens can achieve similar or better optical quality, so as to decrease the size of the system, increase the rate of cost, reduce the comprehensive cost of the system.
3, Molding process A Precision glass molding precision glass molding, is to heat the glass material to high temperature and become plastic, through the aspheric mold to shape, and then gradually cool to room temperature.At present, precision glass molding is not suitable for aspherical lenses with diameters greater than 10mm.But new tools, optical glass and measurement processes are pushing the technology forward.Precision glass molding, although in the early design cost is high (high precision mold development), but after mold molding, the production of high-quality products can be amortized out of the early development cost, especially suitable for large-scale production occasions.B Precision polishing molding lapping and polishing are generally applied to the occasion of producing single aspherical lens at one time. With the improvement of technology, its precision is getting higher and higher.Most notably, precision polishing is controlled by computer and automatically adjusted to optimize parameters.If a higher quality finish is required, Magneto-Rheological finishing will be used.Compared with standard polishing, Mr Polishing has higher performance and shorter time.Precision polishing molding, which requires professional equipment, is currently the first choice for sample production and small batch samples.C Mixing molding Mixing molding, with a spherical lens as the base, through the aspheric die on the surface of the spherical lens die casting and uv curing of a layer of molecular polymer aspherical body.Mixed molding, generally using achromatic spherical lens as the base, a layer of aspheric surface die-casting, to achieve the elimination of chromatic aberration and spherical aberration.FIG. 7 shows the manufacturing process of hybrid forming aspheric lens.Mixed-shaped aspherical lenses are suitable for mass manufacturing where additional characteristics are required (eliminating color and spherical aberration at the same time).D In addition to glass aspherical lenses, plastic aspherical lenses also exist in injection molding.Plastic molding is the injection of molten plastic into an aspheric mold.Compared to glass, plastics have less thermal stability and compression resistance and require special treatment to produce similar aspheric lenses.However, the biggest characteristics of plastic aspherical lens are low cost, light weight, easy molding, widely used in optical quality, thermal stability is not sensitive, little pressure resistance occasions.
4. Selection is based on various types of aspheric lenses, which have their own comparative advantages.Therefore, it is very important to choose suitable products for different application situations.Key considerations include volume, quality and cost.A precision glass molding aspheric lens, has the characteristics of mass production and high thermal stability, suitable for large batch, high quality, high thermal stability situation b precision polishing aspheric lens, with a short sample preparation period and do not need to mold the characteristics of the suitable for the occasion of the sample and small batch sample c mix molding aspheric lens,Has the characteristics of the spherical aberration and chromatic aberration calibration at the same time, suitable for wide spectrum, the occasion of big bulk, high quality plastic molding d aspheric lens, has the characteristics of low cost and light weight, suitable for large batch, quality is moderate, thermal stability is not high Need to customize the aspheric lens (no standard products, and insufficient inventory products),Development cost, sample cost, mass price, lead time and other factors should be taken into account.