A high resolution spectrum analyzer is required to measure a large thickness of a glass plate with a spectral resolved interferometer. In order to solve this requirement, two positions of a reference surface are used to produce short optical differences in the interference signals. Moreover, in order to reduce the dispersion effect a compensation glass is used for the measurement of the rear surface of a glass plate. Linear and nonlinear components of spectral phase distribution of the interference signal are utilized to obtain position of a reflecting surface and thickness of a dispersive medium, respectively. Experimental results show that the measurement error is less than 800 nm and 2 μm for 1 mm and 5mm-thickness glass plates, respectively.
Advanced signal processing is required to make exact measurements with nanometer order accuracy. A complex-valued interference signal of a white-light scanning interferometer (WLSI) obtained from the detected real-valued interference signal through Fourier transform provides an accurate position of an object surface with an error less than 4 nm. Moreover, the sampling points of the interference signal of the WLSI detected with a camera are corrected with the measured scanning positions which are obtained from an interference signal detected by using an optical band-pass filter. This correction method provides more accurate surface profiles with an error less than 2 nm. In experiments a surface profile with a step shape of 3 μm-width is measured accurately.
A general equation of the interference signal of white-light scanning interferometer (WSI) and its Fourier transform are derived. Based on these equations, simulations and experiments are performed to investigate effects of phase random noise and dispersion phase. In the experiments a new method for elimination of a dispersion effect in WSI is proposed. A dispersion phase caused by the two sides of unequal length in a beam-splitter is detected with a spectrally resolved interferometer (SRI). A spectral distribution is obtained by using Fourier transform from an interference signal detected with a WSI. The spectral phase of the SRI is subtracted from the spectral phase of the WSI to get a dispersion-free spectral phase, which provides an improved complex-valued interference signal whose maximum amplitude and zero phase provide two measurement values. These two measurement values are compared to a measurement value obtained from the linear component in the spectral phase.
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.