The process flow of optical component processing varies with different processing methods. There are two main types of processing methods for optical components: traditional (classical) processing techniques and mechanized processing techniques. Traditional processing techniques are mainly used for small and medium-sized batches. The characteristics of traditional craftsmanship mainly include:
1. Using granular abrasives and universal machine tools, optical glass is ground using contour forming method. During the operation, rosin and tar adhesive is mainly used to bond the upper plate. First, use diamond sand for rough and fine grinding of the parts, and then use a rosin tar polishing mold and polishing powder (mainly cerium oxide) to polish the parts. There are many and variable factors that affect the process, and the machining accuracy is also highly variable, usually in the order of several wavelengths. High precision can reach hundreds of times the wavelength.
2. The manual operation involves a large amount of work, multiple processes, and high technical requirements for operators. The requirements for machine tool accuracy and tooling are not so strict, and are suitable for processing techniques with multiple varieties, small batches, and large changes in accuracy.
The traditional manufacturing process, taking a lens as an example, goes through the following steps in sequence:
(1) Rough processing. Including selecting suitable block materials according to the optical component diagram, cutting and leveling, dividing, gluing, and rolling to open the spherical surface.
(2) Rough grinding processing. Make the surface roughness and spherical radius meet the requirements for fine grinding. In traditional craftsmanship, rough grinding is performed on a single piece. In factories that generally use traditional processing techniques, the rough grinding workshop often includes rough machining.
(3) Upper plate: After rough grinding and cleaning, the lens blanks are combined into a plate with the same radius one by one. By relying on adhesive to fix the dispersed lenses on the spherical adhesive film, it should be noted that when forming the disc, the processed surface of each lens blank should be on the same radius spherical surface.
(4) Fine grinding and polishing process. When processing the surface of parts, it is generally not necessary to remove the disc during the polishing process, that is, to complete one disc at a time. In operation, first use three to four layers of steel sand with progressively finer particle size to grind the machined surface to the required surface roughness for polishing, then clean and polish. Polishing is carried out by adding polishing powder to a polishing mold with a certain radius. After one side is processed, apply a protective film and flip it over before putting it on the plate. Fine grinding and polishing the second surface.
(5) Centering and edging process. During the lens processing, there may be a deviation between the optical axis and the positioning axis (known as eccentricity). The task of centering edge grinding is to eliminate eccentricity and make the radial dimension of the side cylindrical surface meet the assembly requirements. The traditional process of edge grinding is often carried out on optical centering edge grinding machines.
(6) The coating process requires the addition of an anti reflective film to lenses with surface transparency requirements. Spherical mirrors need to be coated with reflective film. Some also need to be coated with thin films of other properties, which are determined by the design according to the usage requirements.
(7) Adhesive bonding process. For lenses with high imaging quality requirements, several lenses are often glued together. Bonding should be done after coating.