| Modern optical components which have high accuracy,freeform surface and large aperture,have been widely utilized in various fields.On-machine scanning measurement can be used to measure different size and kinds of optical surface.But the accuracy of scanning measurement is affected by the straightness error of the scanning motion.Multi-probes error separation techniques can be used to separate straightness error,but there are still some limitations when using these techniques.In this paper,based on the high repeatability of the flexure hinge,a new method of shear scanning with single probe is proposed to improve scanning measurement accuracy.We call this method as shear scanning.The main contents of this study are as follows:1.A new scanning method with single probe is put forward for realizing multi-probes error separation techniques.The principle of Sequential Two Points via the shear scanning method has been introduced.A scanning measurement system is built up for later research.2.A shearing stage which is composed of flexure hinges is designed utilizing Finite Element method.Test results indicate that the shearing stage has good repeatability,which can be used in the shear scanning method.3.The error sources in measuring progress of the shear scanning method are analyzed.The relationship between reconstruction error and each error source is established by computer simulation.Based on Monte Carlo method,reconstruction error and measurement uncertainty have been evaluated.4.Plane and curved surface are measured utilizing the shear scanning method.The measurement results are compared with that measured by an interferometer and PGI-1240.Experiments demonstrate that the method of shear scanning with single probe is able to improve scanning measurement accuracy and has high accuracy for optical surface’s profile reconstruction. |
