Research Projects

With the advancement in the manufacturing the need for the nanometric surface finish on the optical components is increasing. This has extended to the functional optical surfaces utilized in aerospace, biomedical and defence etc., In order to ensure the surface finish requirement and stringent tolerance necessitates the need for advanced measurement systems. Use of traditional offline surface quality inspection will disrupt the workflow and hinders the production rates. Thus, attempts are made to address this issue using On-Machine Metrology (OMM) that can perform with in the machine tool environment. While earlier OMM systems utilized Sapphire/diamond microprobes for profile error compensation and freeform surface measurement, these contact probes can potentially damage optical surfaces. In recent times, chromatic confocal technology has gained popularity for non-contact surface measurement. However, point-by-point scanning acquisition in confocal systems can limit spatial resolution, working distance, and introduce position errors. Additionally, the acquired data often requires intensive post-processing, including filtering, to obtain accurate surface information. In addition to point-by-point strategies, full-aperture measurement methods, such as deflectometry and interferometry, have been introduced using vision systems. While most interferometric techniques are designed for off-machine measurements, their potential for on-machine metrology remains largely unexplored. Given the increasing demand for metal mirrors and the need for long-working distance measurement capabilities, this area warrants further investigation. To address the critical demand for the long working distance and complex geometry in fabrication of the diamond turned components, this work proposes a Low-Coherence Interferometry (LCI) system to assess surface quality during the machining process. Furthermore, a comprehensive and accurate evaluation of the roughness after obtaining the data stack of interferogram will be carried out using wavelet analysis. Wavelet analysis provides both spatial and frequency information, enabling the reconstruction of surface features. The primary goal of using wavelet analysis is to decompose the data into high-frequency and low-frequency components, which correlate with form, waviness, and roughness. Subsequently, software will be developed for the evaluation of the surface quality parameters in diamond turning. The proposed LCI-Wavelet based OMM system will be tested in various diamond turning applications and compared with industry-standard interferometers, such as Zygo® Verifier and Fizeau Phase Shifting Interferometer, to validate its effectiveness.