In temporal phase-shifting interferometer, environmental vibrations can induce the wobbling of fringes pattern that usually results in erroneous surface measurement. In order to actively compensating for the external vibration, wave-front phase variation, in proportion to the variation of optical path difference between reference and test arm of the interferometer, should be measured firstly. So, an optical heterodyne interferometric vibration measuring system is embedded in the interferometer, the real-time wave-front phase variation due to vibration is measured by comparing phase difference of two heterodyne signals at 40MHz, one is from reference arm, another is from test arm. An acousto-optical modulator (AOM) is used as optical frequency shifter. After wave-front phase measuring, secondly, a vibration servo compensating system is built. In this system, if real-time wave-front phase is differ from preset phase, an adaptive feedback signal is formed to drive a piezoelectric transducer (PZT), and the PZT drives the standard reference mirror to shift optical path difference in order to pulling wave-front phase to the preset value, thus, vibration is compensated and fringes pattern is stabilized. Thirdly, if preset phase value is periodically changed, a series of phase-shifting interferograms can be sampled. In the end, vibration-compensated effect of this adaptive interferometer is evaluated by an actual optical surface testing, results show this system works very well in the presence of vibrations which amplitude-frequency product is greater than 100 wave-Hertz. Frequency response of this system is restricted by PZT driven reference mirror.
A vibration-resistance phase-shifting interferometer (PSI) was recently constructed and demonstrated. In this instrument, we have developed a method for actively compensating for vibration using a closed-loop phase servo system. An essential feature of this is phase modulating interference fringes fractionizing technology. This method can detect the fringe movement at 1/400 fringe interval, so fringes phase can be locked by the closed-loop feedback within 0.005 π. And the instrument implements phase shifting with the same piezoelectric transducer (PZT) that also compensates for vibration as feedback device. A microprogrammed control unit (MCU) is used to process phase information from photoelectric receiver, and then output the control signal to PZT driver. Experiments show that this solution is unique.
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.