Aspheric surface processing technology and principle

Material division:
The milling, turning and polishing are the representative, mainly including traditional milling and polishing; CNC milling, turning, precision grinding and polishing; Computer controlled polishing, etc. Especially for NC Polishing, the polishing medium can be divided into small grinding tools, stress plates, ion beams, plasma, magnetorheological, liquid jet polishing, etc.
The characteristics of the method are that the efficiency is relatively high, the interoperability with traditional optical processing is easy to accept, the flexibility is high, and it is suitable for the development of sample and small and medium-sized batch production. But the product consistency is poor, and the requirements for operators are higher.
Die forming method:
Glass hot pressing, optical plastic injection molding, thermal settlement and solidification forming. The characteristics of the product are high efficiency, good consistency of finished products, low requirements for operators, and suitable for mass production. But the requirements of the mould are high, the initial investment is large and the process flow is more complex.
Additional material method (adding material method):
Vacuum coating and copying. The essence of the material is to add a layer of thin layer material which matches the asphericity and refractive index on the basis of the closest to the sphere. The features of the work piece are good consistency, low requirements for equipment and good flexibility. It is suitable for the production of small and medium-sized and reflective elements. However, the application is limited by the matching of additional layer with the base material.
Aspheric processing method and equipment
1.JRCODE-CCOS
The main body of the machine is gantry structure. The moving parts are equipped with precise guide rail and high precision grating feedback. The 8-axis controller is used to realize the combination interpolation of any axis and the online contour measurement system is integrated. The process system is open, with multi track selection, multi format data compatibility, variable parameter control and optimization functions. It can realize the precise manufacturing of optical elements of optical glass, microcrystalline, silicon carbide, quartz and other materials. Especially, the adaptive processing model is developed for high-quality optical coaxial and off-axis aspheric elements, which achieves the polishing surface precision better than 1/50 λ( RMS, λ= 632.8nm).
2. Mr polishing q22-750p2
For optical glass, microcrystalline, silicon carbide, quartz and other materials, the surface roughness and surface shape accuracy can be obtained. It is especially suitable for ultra precision machining of high quality optical coaxial and off-axis aspheric elements.
3. magnetic jet polishing
The magnetic jet polishing is a combination of jet technology and magnetorheological technology. The magnetorheological effect is produced by the low viscosity magnetorheological fluid under the action of external magnetic field. The apparent viscosity increases to increase the stability of the jet beam surface. The jet beam with abrasive particles is mixed with the axial magnetic field at the nozzle to form a collimated and hardened jet beam sprayed to the workpiece surface at a certain distance, The material is removed by the high speed impact shear of abrasive particles, and the polishing surface finishing is realized in a controllable way.
So, let's look at the effect of the magnetic jet
4. polishing technology of stress disk
This is a very high polishing method. Chengdu photoelectric Co., Ltd. is doing it in China. There are some columns evenly distributed on the surface of the stress plate pulled by a series of motors above. These columns are connected by silk wires. These wires can be tightened and relaxed by the motor, so that the deformation of the panel surface can be controlled to make the disc face fit with the workpiece better, This enables precise polishing. The disadvantage of polishing stress disk is that it is too complex to control it - look at it and faint!
5. ion beam polishing
The ion beam with certain energy and spatial distribution emitted from the ion source bombards the surface of the workpiece. After the ion is incident to the surface of the workpiece, it collides with the workpiece atom within a certain depth. During the collision, the incident ion transmits its energy to the workpiece atom. When the energy obtained by the workpiece atom is greater than the lattice binding energy, The work-piece atom will continue to move away from the lattice binding and collide with other workpiece atoms in cascade. That is, repeat the above actions. When the energy transferred to the next atom is greater than the lattice binding energy, the next atom will also move away from its original position. If the energy obtained by the atom is not enough to overcome the lattice binding energy, the energy obtained will not be transmitted, Can only be released as phonon. In this process, energy is transferred between the ion and atom, between atoms and atoms. When the energy obtained by atoms on the surface of the workpiece is larger than that of the material surface and lattice binding energy in the normal direction of the mirror surface, the atom will fly away from the surface of the workpiece.
To be honest, it is to remove atoms on the surface of materials one by one (a little exaggeration).
The above mentioned mainly is various polishing, but only one process in aspheric processing. Other materials are milled and formed. Rough grinding and fine grinding are polishing below, and then coating and other processes. In addition, there are glass hot pressing molding, injection molding, heat deposition, replication and other technologies.