A simple method which can be used to map mid-spatial scale surface irregularities with high signal noise ratio is described. Two major sources of errors are analyzed and removed. One is the contributions of small-scale irregularities of the reference surface, which are subtracted by shifting the test surface laterally by a distance. The other is the spurious response of CCD, which is removed by interpolation function. The presented method is verified by simulations and experiments. It shows that it can measure mid-spatial scale surface irregularities exactly and smaller scale surface irregularities can be obtained by making measurement for a series of the lateral shifting values corresponding to one-half of the pixel space on CCD.
A 100-mm-aperture high lateral resolution interferometer has been developed in Fine Optical Engineering Research Center (FOERC), which is applied to the measurement of spatial frequencies of up to 2.5 lines/mm over a 100mm field of view. The system transfer function of the interferometer is greater than 60% at near half the Nyquist frequency. To demonstrate the performance of this high lateral resolution interferometer, theoretical errors of the system are thoroughly analyzed and the design implementation is carefully studied, such as light source, wave front slope, tolerance analysis, CCD sample and so on.
A 500-mm-aperture wavelength-tuning phase-shifting interferometer has been developed in FOERC applied to the measurement of large optics. The optical and mechanical design and the calibration technique of the phase shifter are described in detail. Test results show that Peak-to-Valley value smaller than 63nm of interference cavity is achieved.
A 500-mm-aperture wavelength-tuning phase-shifting interferometer has been developed in FOERC applied to the measurement of large optics. Also it can switches to a smaller 130-mm-aperture. We describes in detail the optical and mechanical design as well as calibration technique of phase shifter and phase-shifting algorithm design. A Zygo 4 inch standard reflective flat is used to evaluate the accuracy and repeatability of our wavelength-tuning phase-shifting system.