Spherical Lens- processing
Sep. 23, 2021
Commonly used spherical lenses include plano convex lenses, plano concave lenses, biconvex lenses and meniscus lenses. Spherical lenses are widely used in machine vision and laser applications.
The cold working of spherical lenses is blank cutting, rough grinding, polishing, core taking, coating, bonding and blacking.
Before processing optical parts, it is necessary to prepare optical materials used for processing, that is, blanks or glass materials. The rough material is cut on a cutting machine. The hardness of the glass is matched with the particle size of the cutting wheel. In order for the two curved surfaces to be closer to the radius of the target spherical lenses, the center thickness is reserved. And bad materials such as pits on the surface are excluded to prepare for the subsequent rough grinding and polishing.
Rough grinding is an intermediate process of grinding, which is equivalent to semi-fine processing in mechanical processing. This process eliminates pits on the surface left during cutting to meet the requirements of surface accuracy, surface quality, and center thickness. In this process, the particle size of the diamond particles, the degree of wear of the glass material, the rotation speed of the main shaft, and the amplitude of the swing arm are coordinated with each other.
Grinding and polishing is the main process to obtain the surface quality of spherical lens. It removes the remaining defects in the previous process, so that the surface accuracy，center thickness and dimension meet the specifications. In this process, it is necessary to pay attention to the cleanliness of the grinding powder, the concentration of the mixing ratio of the grinding liquid, the temperature of the liquid, the selection of the polishing skin, the rotation speed and the amplitude of swing arm and so on.
Next, use a diamond wheel to grind the outer circle. Superimpose the center line (optical axis) corresponding to the two spherical surfaces of the spherical lens with the mechanical fixture axis (geometric axis), while ensuring that the lens is not scratched, and the outer diameter, chamfering, and depth requirements (for concave lenses) meet the specifications. This process is the same as cutting. It is necessary to consider the interaction between the particle size of the diamond grinding wheel and the glass abrasion.
After grinding and polishing, take out the lenses and clean the polishing liquid and other impurities. After the core is taken, the lenses are taken out. The cutting coolant remaining on the surface is cleaned. During the cleaning, it is necessary to consider factors such as the quality of pure water, lotion concentration, ultrasonic intensity, drying conditions, water resistance, acid resistance, and alkali resistance of the glass material to ensure the quality of the spherical lenses after cleaning.
In order to make the lens have the required optical performance, the two surfaces of the lens could be plated with different thicknesses of film layers to make it have certain spectral characteristics and influence effects. In the vacuum chamber of the vacuum coating machine, the coating material is heated and vaporized upward to the surface of the lens facing the material. The coatings of optical lenses are mainly divided into AR coating (anti-reflection coating) and IR coating(infrared cut-off coating). According to different requirements of product design, different coatings are plated. After coating, inspect adhesion strength, central wavelength, transmittance, reflectance, etc. of the coating. The coating materials commenly used are magnesium oxide, zirconium oxide, titanium oxide, carbon dioxide and so on.
In order to reduce the loss of light energy during reflection and simplify the processing of complex lenses, two or more lenses must be glued together with special glue in accordance with technical requirements to achieve optical performance. According to the needs of the application, the outer diameter of the lens and the vertical chamfer are uniformly blacked withto eliminate or reduce the diffuse reflection of stray light in the lens and reduce the imaging effect.
CLZ Precision Optics Co., Ltd. processes all kinds of high-precision optical components in strict accordance with international quality standards (US military standards and European national standards). If you need custom high-quality spherical optical lenses, please contact email@example.com.