In optical systems, the accuracy of the lens is the basis for system performance. To ensure the accuracy of the lens, high-precision detection methods are crucial in lens processing. Commonly used phase-shifting interferometers are susceptible to environmental influences, while the quadriwave lateral shearing interferometer (QWLSI) can solve this problem. QWLSI reconstructs the wavefront from just one interferogram and is becoming increasingly popular owing to its compactness and portability. The most commonly used method to analyze interferograms in QWLSI is the Fourier transform method (FTM), which requires more sophisticated processing and computing time and is erroneous at the edge of the aperture. This study deduces that the spatial carrier phase-shifting (SCPS) algorithm should replace the FTM in QWLSI. Theoretical derivations and simulation results showed that QWLSI works faster and more accurately when the SCPS replaces the FTM.
When using the Fourier transform method to demodulate the phase from an interferogram, the Gibbs effect often occurs at the edge of the phase picture. Fringe extrapolation is a straightforward method to suppress the Gibbs effect. Currently, many algorithms are used in fringe extrapolation, and exemplar-based methods are one such alternative. However, the traditional exemplar-based algorithm is based on the Criminisi algorithm, which is extremely time-consuming. In this study, the structure-guided image-completion method was applied to interferogram extrapolation. Simulations and experiments show that the new method reduces computer memory requirements and saves computing time. Compared with extrapolation using the Criminisi algorithm, the speed can be increased by tens or even hundreds of times.
Optical testing, having the merits of non-destruction and high sensitivity, provides a vital guideline for optical manufacturing. But the testing process is often computationally intensive and expensive, usually up to a few seconds, which is sufferable for dynamic testing. In this paper, a GPU-accelerated phase extraction algorithm is proposed, which is based on the advanced iterative algorithm. The accelerated algorithm can extract the right phase-distribution from thirteen 1024x1024 fringe patterns with arbitrary phase shifts in 233 milliseconds on average using NVIDIA Quadro 4000 graphic card, which achieved a 12.7x speedup ratio than the same algorithm executed on CPU and 6.6x speedup ratio than that on Matlab using DWANING W5801 workstation. The performance improvement can fulfill the demand of computational accuracy and real-time application.
Comparative simulations are designed to evaluate the noise suppression performance of three typical phase shifting algorithms under different testing environments. The results show that random phase shifting algorithm is robust under different level of noise and has higher testing accuracy than conventional normal steps phase shitting algorithm while it’s computationally low. Guidelines are given to choose a proper PSI algorithm under a certain testing environment with noises.
A convenient method to study the influence of error sources in Fizeau is to build a ray-tracing model to simulate the error sources. In this paper an interferometer model is presented; an extension program is called to simulate the interference; and a preliminary research of several error sources is conducted. These examples demonstrate error analysis based on interferometer models is feasible and provide some guidance for optimizing our interferometer design.
A simultaneous phase-shifting interferometry(SPSI) based on the common-path Fizeau interferometer has been discussed.In this system,two orthogonal polarized beams, using as the reference beam and test beam ,are detached by a particular Wollaston prism at a very small angle,then four equal sub-beams are achieved by a combination of three non-polarizing beam splitters(NPBS),and the phase shifts are introduced by four polarizers whose polarization azimuths are 0°, 45°, 90°, 135° with the horizontal direction respectively,the four phase shift interferograms are collected simultaneously by controlling the CCDs working at the same time .The SPSI principle is studied at first,then is the error analysis, finally we emulate the process of surface recovery by four steps phase shifts algorithm,the results indicate that, to ensure the feasibility of the SPSI system, we have to control the polarization azimuth error of the polarizer in ± 0.5°.
We present a method to measure the radius of curvature of a concave conic asphere. By analysis the central area of the asphere, we can measure the radius of an arbitrary point in the central area instead of the vertex of asphere. In the procedure, we firstly adjust the interferometer until the interferogram of the central area approach nulls, then put the laser tracker ball at the beam focus of the interferometer and move the tracker ball to touch the central area of the aspherical surface to get the two positions. With these measurement data, we can calculate the radius of curvature of the aspherical vertex and its uncertainty.
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.