Research On Large Range And Ultra Precision Non-contact Scanning Measurement Method Of Optical Surface

In the optical system,various curved surface structures are widely used,such as spherical surface,aspheric surface and free-form surface.Among them,free-form surface has higher degree of freedom in design,which can effectively improve the performance of the optical system and reduce the number of optical lenses required.Therefore,it is widely used in various optical instruments,and its processing and measurement are also highly valued.However,optical free-form surfaces are generally difficult to measure.Scanning measurement is suitable for different types of surface measurement,so it has great advantages in optical surface measurement.Compared with the contact measurement,the non-contact measurement will not cause the workpiece scratch in the measurement process,and is suitable for the measurement after the final processing of optical surfaces.However,the range and accuracy of non-contact sensors are difficult to take into account.The range of high-precision non-contact sensors is often small,so it is difficult to scan and measure the large vector high optical surfaces.In order to solve the above problems,this theses has studied the large range ultra precision non-contact scanning measurement method of optical surface,expanded the range of the non-contact sensor,developed a large range non-contact scanning measurement device,studied the tracking scanning measurement method,and carried out performance tests and measurement experiments on the device.The main work of this theses includes:（1）The large range non-contact scanning measurement method of optical surface was studied,the range of the non-contact sensor was extended,and a large range scanning measurement device was developed,which lays a foundation for the ultra precision measurement of large vector height optical surface.The designed measuring device drives the high-precision non-contact sensor to make a linear motion through the flexure hinge to follow the measured surface,which ensures that the measured surface is always within the range of the non-contact sensor,and then measures the displacement of the flexure hinge through another displacement sensor.Finally,the surface information is obtained by combining the data of the non-contact sensor and the displacement sensor.（2）The tracking and scanning measurement method was studied.The adaptive surface tracking of the measurement device was realized,and the positioning error of the servo drive system was compensated to improve the measurement accuracy of the measurement device.Finally,the tracking and scanning measurement control was successfully realized.（3）The error of the measuring device was analyzed,the measurement accuracy was improved by improving the data processing method,and the measurement uncertainty of the scanning measuring device was evaluated.The expanded measurement uncertainty is 0.248μm.（4）A scanning measurement experiment was carried out to measure a two-dimensional profile that exceeded the range of the non-contact sensor,and then the same profile was measured with the Taylor profiler.The measured results were compared,and the difference between the two PV values was 0.2 μ m.It was proved that the designed measuring device has the ability of large range non-contact scanning measurement and sub micron measurement accuracy.The scanning measurement of three-dimensional surface was carried out,which proved that the designed measuring device has the ability of large range scanning measurement of three-dimensional surface.