I. From smartphones that everyone owns, to TVs and computers in daily life, and even to military and aerospace applications in national defense, the demand for optical components has grown increasingly extensive with the advancement of modern science and technology.
A growing number of precision instruments have adopted new opto-mechatronics technologies, driving the realization of increasingly stringent requirements for multi-functionality, high performance, and low cost. This has further promoted the development of traditional optical component production technologies and the transformation of grinding and polishing processes. Such transformation has propelled optical machining technology toward two distinct directions.
First, the trend toward high-efficiency processing for smaller, lighter, and more cost-effective components. The rapid development of optical plastic and glass molding technologies has significantly reduced the cost of aspherical lenses, enabling a substantial increase in supply. Consequently, a growing variety of optical systems have begun to adopt these lenses. For example, ultra-thin zoom lenses are now widely used in mobile phones. The expanding application of these small, lightweight, and affordable optical components across various fields has driven the rapid advancement of high-efficiency optical machining technologies.
Second, the trend toward ultra-precision machining. Technological progress in cutting-edge science and technology, particularly in the national defense industry, has imposed new requirements on ultra-precision optical components.
For instance, optical systems for manned spaceflight, laser weapons, fiber optic communication components, and micro-optical parts in optical integrated circuits are all ultra-precision optical components. The machining accuracy of these components even reaches the nanometer level. Traditional processing methods are inadequate for manufacturing these parts, which can only be achieved through ultra-precision machining technologies.
Traditional optical component processing methods have a history of over a century, which can be colloquially described as “a handful of abrasive and a splash of water”. In contrast, modern optical component processing methods emerged in the 1970s. Driven by the expansion of military optical systems from visible light to infrared and laser systems, arduous requirements were placed on optical components, including superior imaging quality, compact size, light weight, and simplified structure. This triggered large-scale technological revolutions and innovations in the optical machining industry, leading to the continuous emergence of new optical component processing methods.
Currently, the most commonly adopted optical component machining technologies include: CNC single-point diamond turning, CNC grinding and polishing, optical lens molding, optical plastic molding, magnetorheological finishing, electroforming, and traditional grinding and polishing technologies.
II. Basic Principles of Ultra-Precision Machining Technologies
1. CNC Single-Point Diamond Turning
CNC single-point diamond turning is an aspherical optical component machining technology. It utilizes a natural single-crystal diamond tool on an ultra-precision CNC lathe to perform single-point turning of aspherical optical components under precisely controlled environmental conditions. This technology is primarily used for machining small-to-medium sized optical components made from infrared crystals and metallic materials.
2. CNC Grinding and Polishing
CNC grinding and polishing is an optical component manufacturing technology in which a CNC precision machine tool grinds the workpiece surface into the desired profile, followed by polishing with a flexible polishing pad to meet the technical specifications of the component. The principle of this technology is closest to classical optical machining methods, achieving precision machining of optical components mainly through the digital precision control of machine tools.
3. Optical Lens Molding
Optical lens molding involves placing softened glass into a high-precision mold and directly molding it into optical components that meet application requirements under conditions of controlled temperature, pressure, and oxygen-free environment. The widespread application of optical lens molding technology represents a significant revolution in optical glass component machining. This technology has epoch-making significance for reducing the cost and increasing the production volume of aspherical glass components.
III. Application Scope of Ultra-Precision Optical Component Machining Technologies
1. CNC Single-Point Diamond Turning
Currently, materials that can be directly machined to optical surface quality using diamond turning primarily include non-ferrous metals, germanium, plastics, and infrared optical crystals. However, this method cannot achieve optical surface quality for glass, which requires subsequent grinding and polishing for correction. Another major application of CNC single-point diamond turning is the machining of precision molds for various molding processes.
2. CNC Grinding and Polishing
The primary material processed by CNC grinding and polishing is glass, which precisely compensates for the limitation of CNC single-point diamond turning in directly producing finished optical glass components. This technology is mainly used for machining spherical and aspherical optical components, serving as the primary alternative to traditional classical optical glass processing methods. It offers advantages such as high precision and high processing efficiency. With a long development history in the market, this technology has a comprehensive range of mature equipment. For example, German companies including Satisloh, Optotech, and Schneider have launched various types of grinding, milling, and polishing machines. Meanwhile, extensive research on CNC technologies has also been conducted in China.
CNC grinding and polishing technology has made significant progress not only in the automation and machining accuracy of CNC equipment but also in the research of various polishing methods and principles, which has greatly promoted the development of optical aspherical machining technology.
3. Optical Lens Molding
At present, optical lens molding technology is used for mass production of precision spherical and aspherical lenses. It can manufacture not only commonly used medium-aperture lenses but also extends to micro-lens arrays as small as 100 microns and larger-aperture lenses up to 50 millimeters. It is applicable to the production of spherical and aspherical optical components for both military and civilian optical instruments, as well as aspherical lenses for fiber optic couplers used in optical communications.