Abstract
Form characterization of a machined optical freeform surface demands accurate alignment of the sampled measured data points on the machined surface, and they are compared with the designed geometry of the surface through positioning. In this paper, a fiducial-aided robust positioning method (FAPM) is developed which attempts to evaluate freeform surfaces with high efficiency and precision. The FAPM method makes use of fiducials as reference datum to form a fiducial-aided computer-aided design (FA-CAD) of the freeform surface which not only establishes an inherent surface feature, but also links the different coordinate systems among design coordinate frame, machine tool, and measurement instrument. To verify the capability of the proposed method, a series of experiments were conducted. Compared with the traditional freeform measurement method (e.g., least squares method), the results indicate that the robustness and accuracy of the measurement is significantly enhanced by the FAPM.
Highlights
Freeform surfaces possessing non-rotational symmetry have been widely used in many industries, including aerospace, telecommunication, biomedical engineering, etc. [1]
An optical freeform surface named an F-theta lens was defined by Equation (7) which was designed to verify the proposed fiducial-aided robust positioning method (FAPM): z = (−1/250) x2 + (1/92000) x4 − (1/25)y2 x ∈ [−18, 18], y ∈ [−7.5, 7.5]
The designated positions of the six calibrated spheres were used as the fiducials, which were located around the edges of the fixture, and they were designed with different heights
Summary
Freeform surfaces possessing non-rotational symmetry have been widely used in many industries, including aerospace, telecommunication, biomedical engineering, etc. [1]. The proposed fiducial-aided robust positioning method (FAPM) was purposely developed to position the freeform surface among different coordinate systems of the designed surface model, the machine tools, and the measurement instrument. The fiducials serving as reference datum are used to determine a transformation matrix from the coordinate frame of the designed surface to that of the machining workpiece so as to transfer the FA-CAD to the coordinate frame of the machine tool.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
