Development and application of the hottest ultra p

2022-09-22
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Development and application of ultra precision machining technology

1.1 definition and name

micro optics is a new science that belongs to the interdisciplinary field of many frontier disciplines. With the help of the latest research results of microelectronic industry technology, micro optics is one of the most cutting-edge research directions in the world, and has a wide range of application prospects. Micro optical element (MOC) refers to free-form optical surface and microstructure optical elements with surface accuracy of sub micron level and surface roughness of nano level. Free-form optical surfaces include rotating aspherical surfaces with rotation axes (such as paraboloids, involutes, etc.) and non rotating aspherical surfaces without any symmetry axes, such as Zernike aberration equation surfaces. Microstructure refers to the topological shape of micro surface with specific functions, such as grooves, microlens arrays, etc., and the surface of micro pyramid structure as shown in Figure 1 (Figure 1 is omitted). These structures determine the reflection, transmission or diffraction properties of light, which is convenient for optical designers to optimize optical systems, reduce weight and reduce volume. Typical micro optical elements, such as holographic lens, diffractive optical element (DOE) and gradient refractive index lens, are applied to various optoelectronic instruments, which can make optoelectronic instruments and their parts more miniaturized, arrayed and integrated

1.2 application of micro optical elements

micro optical elements are the key components for manufacturing small optoelectronic systems. They have the advantages of small volume, light weight, low cost, and can realize new functions such as microminiaturization, array, integration, imaging, and wavefront conversion, which are difficult to be achieved by ordinary optical elements. As the miniaturization of the system continues to become a trend, it has application prospects in almost all engineering application fields, whether in the field of modern national defense science and technology, or in the general industrial field. In military affairs, aspheric optical parts have been used in military photoelectric systems developed and produced by western countries after the 1970s, such as military laser devices, thermal imaging devices, low light level night vision helmets, infrared scanning devices, missile guidance heads and various zoom lenses to varying degrees. In general civil photoelectric systems, free aspheric parts can be widely used in various photoelectric imaging systems. Such as the display system providing flight information in the aircraft; Viewfinder and zoom lens of camera; Germanium lens in infrared wide-angle horizon; Video recording and recording shall be read out with microscope objective lens; Indirect ophthalmoscope, endoscope, progressive lens, etc. for medical diagnosis. Microstructure optical elements are widely used, such as micro slot structure in optical fiber connector, micro lens array of liquid crystal display, f-theta lens for laser scanning, beam splitter of laser head, etc. These microstructure optical elements are used in many products we use daily, such as, handheld computers, CDs and DVDs

1.3 micro optical component processing methods

driven by the application requirements, the research on micro optical component processing technology is also deepening, and a variety of modern processing technologies have emerged, such as electron beam writing technology, laser beam writing technology, lithography technology, etching technology, LIGA technology, replication technology and coating technology, among which the most mature technologies are etching technology and LIGA technology. These technologies are basically developed from the micro machining technology of microelectronic components, but unlike electronic components, three-dimensional molding accuracy and assembly accuracy are crucial to optical components, which will directly affect their performance. Therefore, these methods have their own defects and limitations. For example, due to the depth of field of view 6.3, Party A's factory environment: power fluctuation range: 380V 10%; Frequency 50Hz 3%; Ambient temperature requirements: 1030 ℃; Humidity: less than 90%, lithography technology is limited to the processing of two microstructures and three-dimensional structures with small aspect ratio; Using sacrificial layer etching technology, although quasi three-dimensional processing can be achieved, it is easy to cause internal stress in the material, affect the final mechanical properties, and the equipment cost is very expensive; The X-ray light source with high collimation used by LIGA technology is generally obtained through synchrotron radiation accelerator, and the cost is much higher than that of lithography equipment, which is difficult for general laboratories and enterprises to afford; Electron beam writing technology can process nanoscale precision structures, but its efficiency is low. Cooling device: it is difficult to mass produce the formed plastic extruded layer after leaving the machine head. Replication technology, including hot press molding, molding and injection molding, is a low-cost technology suitable for mass production, but its molds are required to have high precision and durability

Another processing method of

micro optical components is ultra precision machining technology. Recently, there is a sentence in Fortune magazine: ultra precision machining technology plays a role in optical components as integrated circuits did in electronic components. Although this sentence is not without exaggeration, it shows that the processing of micro optical components with ultra precision machining technology has attracted great attention. The application of ultra precision machining technology in the processing of micro optical components will be discussed in detail in the next section

2 application of ultra precision machining technology in the processing of micro optical components

ultra precision machining technology is to use cutting tools to change the shape of materials or destroy the surface of materials, so as to achieve the required shape in the form of cutting. Such as single crystal diamond turning and milling, grinding, rapid cutting and mechanical polishing. This section mainly describes the ultra precision machining technology used to process optical elements and their molds. 2.1 development of key technologies of ultra precision machine tools

computer aided design technology, especially the development of finite element analysis technology, provides a convenient means for the optimization design of the overall structure of ultra precision machine tools, making the rigidity and stability of machine tools continuously improve. At present, the typical structure of single crystal diamond lathe has a T-shaped layout structure. The spindle is generally installed on the x-direction guide rail, and the cutter is installed on the z-direction guide rail. In recent ten years, with the rapid development of computer technology, some key technologies of ultra precision machine tools, such as control technology, feedback system, servo drive device, have made great progress, which has improved the machining accuracy of ultra precision machine tools. At present, ultra precision has been able to directly process surfaces with a roughness of 1nm. The development of these key technologies can be summarized as follows: using natural granite as machine tool bed, it has very high thermal stability and mechanical stability; Use air spring system to isolate vibration; Using liquid or aerostatic guide rail, the damping is increased, the motion is smooth, and there is no friction; The DC linear motor fast drive system has good dynamic stiffness; High speed air spindle has high bearing capacity and rigidity, which can improve machining accuracy; Open computer numerical control (CNC) technology is convenient for the application of third-party control software to improve machining accuracy; High resolution detection device, which can provide accurate position feedback; Using the fast servo mechanism, the macro micro combination technology of multi axis system is realized to process complex surfaces; Measurement and error compensation technology, correctly measure the residual error of the workpiece and finally eliminate the error

2.2 application examples

the development of electronic and optical technology has greatly promoted the application of free aspheric and other non-traditional geometric microstructure optical elements. The emergence of some optical design software makes it easy for optical designers to optimize the performance of optical systems, but it will also make optical components more complex, which requires micro optical component manufacturing technology to be competent to process these complex optical components. For designers and manufacturers of micro optical components, single crystal diamond ultra precision machining technology has many advantages, for example, it can process real three-dimensional structures; The forming accuracy of machined parts reaches sub micron level; The surface roughness reaches the Ra value of 5nm, and some materials can even reach 1nm; Capable of processing structures with large aspect ratio, etc. Therefore, in the past ten years, the application examples of ultra precision machining technology in the processing of micro optical components are also gradually increasing. For example, the ultra precision processing technology of single crystal diamond has been successfully applied to the processing of contact lenses, prisms, aspheric lenses, microlens arrays, pyramid microstructure surfaces, antireflection gratings and other structures. Figure 2 shows the microstructure processed by single crystal diamond lathe (Figure 2 is omitted). Although the ultra precision machining technology has many advantages for the processing of some structural optical elements, the combination of ultra precision machining technology and replication molding technology may be the most effective way to process micro optical elements, that is, there is a large amount of oil in the water return pipe. The ultra precision machining technology is used to process replication molds, and then fatigue experiments are widely used in aerospace, automobile, shipbuilding, metallurgy In construction and other industries, the mold produces micro optical components. When machining optical element dies with single crystal diamond lathe, we need to pay attention to selecting appropriate processing parameters to reduce burrs and die errors. In addition, we need to be able to process appropriate diamond tools. The Fresnel lens made of the mold processed by the diamond lathe has been used in the overhead projector with great success, as shown in Figure 3 (Figure 3 is omitted)

3 summary

the continuous development of micro optical technology puts forward higher requirements for micro optical component manufacturing technology. Ultra precision machining technology, after more than ten years of rapid development, has many advantages that traditional optical manufacturing technologies, such as lithography and LIGA technology, do not have: ① it can process real three-dimensional structures, and the accuracy reaches the nanometer level; ② Can process floating alignment structure on the mold; ③ The structure with different depth width ratio can be processed on the same component. In the field of micro optical manufacturing, many similar products are processed by many different methods, which shows the immaturity of micro optical manufacturing technology. Although the application of ultra precision machining technology in micro optical components and mold processing has many advantages, it is still in the initial stage of development. Therefore, ultra precision machining technology also has great development potential. We believe that the combination of ultra precision machining technology and replication technology will promote the development of micro optics and its integration technology

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