Research On Lens Profile Measurement Based On High Contrast Laser Wavenumber Scanning System

As the most common optical component,lens is indispensable in optical equipment such as camera,astronomical telescope and microscope.Its surface processing quality directly determines the imaging quality of the equipment.How to realize the high-precision measurement of the three-dimensional contour of the lens surface has important research significance.At present,surface profile measurement methods can be divided into contact and non-contact.Contact measurement is rarely used in the field of surface profile measurement because the contact between mechanical probe and measured part is easy to scratch and damage the device surface.As a kind of non-contact optical measurement,laser wave number scanning interferometry has the advantages of high detection speed and high measurement accuracy.Now it is widely used in the fields of surface profile measurement of precision instruments,nondestructive testing of material defects and so on.Combined with the principle of laser wavenumber scanning,this thesis proposes and designs two new vertical interferometry systems with the advantages of high contrast and strong stability,and completes the research on the surface profile measurement of lenses with different reflectivity.Firstly,this thesis explains the research significance of lens surface three-dimensional contour measurement,describes the research status of three-dimensional contour detection at home and abroad and the measurement principle of common detection methods,and summarizes the development process of laser wave number scanning measurement technology.At the same time,based on the analysis of the principle of wave number scanning,the calculation method of wave number real-time monitoring is further deduced.The simulation shows that the measurement theoretical accuracy reaches the micron level.Secondly,according to the experimental requirements of lens contour measurement,the optical path design of the system and the construction of hardware system are completed.At the same time,aiming at the cumbersome steps of adjusting the imaging position of the measured sample interference signal,a set of clamping system convenient for sample debugging is designed,which realizes the adjustment of the sample in the X and Z dimensions,and can quickly make the sample interference image clear and imaged in the central area of the field of view.The system is calibrated by establishing the lens imaging model,the distortion model is introduced to improve the calibration accuracy,and the corresponding error analysis of the calibration results is made.Aiming at the problem of the optical axis tilt of the camera of the new vertical Fizeau interferometry system,the calibration in the Z direction is completed,and the offset law of the X and Y directions moving with the Z axis is obtained.Finally,the profile measurement of high and low reflectivity lens is completed under two modulation modes of temperature and current.Aiming at the temperature modulation mode,an overshoot model is proposed to solve the problem of nonlinear temperature rise;Aiming at the current modulation mode,combined with the dynamic adjustment exposure algorithm,the problem of pixel light intensity information distortion caused by local brightness saturation of interference signal is solved,the signal acquisition range is effectively expanded,and the measurement accuracy of the system is improved.Finally,the analysis of the signal contrast and stability of the measurement system shows that the maximum upper limit of the signal contrast of the two systems can reach about 0.9（the limit is 1）.The high contrast signal is helpful to solve the problem of signal separation caused by multi surface interference between different devices in the system.At the same time,the repeatability experiments verify that the system has good stability under two different modulation modes of temperature and current.Finally,the feasibility and practicability of the interference system combined with the principle of laser wave number scanning measurement are verified,and it has broad application prospects in the field of three-dimensional contour measurement of lens surface.