This paper proposed a frequency-domain-decomposition denoising algorithm for nano-scale measurement in white light interferometry (WLI). In this work, the captured correlogram is firstly divided into a series of short-time stationary signals, the phase distribution can then be derived as the sum of the corresponding phase components after Fourier transform. By applying windowed threshold filtering, the noises existed in phase map can be eliminated, and a denoised correlogram is precisely reconstructed. Afterwards, the surface height is retrieved through phase-frequency least-square fitting. In simulations, the phase noises with different levels are investigated. By comparing the noise deviations in the reconstructed phase map with the original one, the effectiveness on noise suppression of the proposed method is properly verified. In the experiments, a height step standard with calibrated values 182±2.0nm are tested, where the height deviations below 3nm and the repeatability of 0.5% has proved the robustness of our proposed method.
In this paper, we proposed an aero-engine turbine blade measurement technique based on photometric stereo, which can reconstruct the blade surface quite accurately and efficient from the images captured under multi-illuminations. In this work, a measurement system is designed by using 8 LEDs as the point light sources, a light propagation process under the point light illumination is developed. Based on this process, a normal estimation method is provided for the reconstruction process. The system calibration is implemented on a USAF resolution target manufactured by Edmund, which proves the method is capable of performing the surface recovery with the repeatability error down to 0.0272mm. The experiments are performed through a turbine blade from aero-engine, where the comparison result is also provided by using a commercial portable laser scanner from Creaform, which shows the better performance of the methodology presented in this paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.