| Planar optics,spherical optics,aspherical optics,and free form optics motivate modern industry and technology.Optical elements exist everywhere from eyeglasses,digital cameras and projectors in our life to mask aligners in the semiconductor industry,inertial confinement fusion facilities in clean energy production and space telescopes in space exploration.New requirements for optical elements-including higher accuracy,larger aperture,and smaller weight-pose new challenges to optical manufacture industry.The demand for accuracy and efficiency in modern optical manufacture industry characterizes new precision metrology technology:high accuracy,non-contact,large measurement volume,short measurement time,and universal.As one of the latest forms of coordinate metrology,non-contact coordinate metrology combines the high accuracy,high efficiency,and non-invasive character of non-contact techniques with the versatility of coordinate metrology,which makes it one of the most promising metrology technologies in milling and grinding.This project concentrates on the common requirements in non-contact coordinate metrology.In this project,we developed a specialized software for controlling scanning motion and acquiring data.We also proposed a centering method to solve the common centering problem in cylinder coordinated scanning.Apart from this,we evaluated the measuring uncertainty of this measuring system and researched on surface defects detection.The contents of this research project are listed as follows:1.The application,manufacturing techniques,key types and evaluation metrics of common optics are introduced.Current measuring technologies,including interferometry,stylus profiling,and coordinate metrology,are reviewed,followed by comparing and analyzing domestic and foreign research on non-contact coordinate metrology.The first chapter ends with the significance and content of this project.2.Specialized software for controlling scanning motion and acquiring data was developed.The software can conduct raster scanning,concentric scanning,and spiral scanning,together with the synchronous acquisition of four grating signals and two analog data of the sensor.The maximum data acquisition speed exceeded 40,000 groups per second.Based on this software,measurement experiment of a Φ 10 mm hyperbolic reflector was carried out.3.An iterative centering method based on minimizing scanning amplitude were designed.This centering method can achieve probe centering with centering error less than 5 μm within 10 minutes.4.Measurement uncertainty of this metrology system was evaluated.Probe centering error was calculated,and motion error including straightness,flatness,and runout was measured.Calculation suggests the value of comprehensive measuring uncertainty is 9.18μm.5.A surface defect detecting method based on the K nearest neighbor point cloud filtering algorithm was proposed.Measurement experiments conducted on a head up display reflector suggested that this method can implement simultaneous measurement of surface shape and surface defects.6.The research contents of this thesis were summarized.And future research directions were discussed. |
