A Fizeou interferometer with instantaneous phase-shifting ability using a Wollaston prism is designed. to measure dynamic phase change of objects, a high-speed video camera of 10-5s of shutter speed is used with a pixelated phase-mask of 1024 × 1024 elements. The light source used is a laser of wavelength 532 nm which is split into orthogonal polarization states by passing through a Wollaston prism. By adjusting the tilt of the reference surface it is possible to make the reference and object beam with orthogonal polarizations states to coincide and interfere. Then the pixelated phase-mask camera calculate the phase changes and hence the optical path length difference. Vibration of speakers and turbulence of air flow were successfully measured in 7,000 frames/sec.
A digital phase-measurement interferometer using a tunable SHG blue laser at 410nm was developed. This system enables us to test high NA lenses used in high-density optical storage devices. Excellent features such as wavelength tunability, narrow spectral linewidth, and wavelength stability, make the SHG laser very suitable as a light source for a phase-shifting interferometer working at blue-violet wavelength region. We investigated the tuning characteristic of the SHG laser as a function of DBR-section current and found that the wavelength-changing ratio was 0.0017nm/mA. An unbalanced Twyman-Green interferometer with the SHG laser was composed to measure the transmitted wavefront of an optical pickup lens with a NA of 0.85. The theory and experimental results are presented.
A multimode spectrograph for tridimensional spectroscopic observations of faint extended objects is under development. The spectrograph has four modes, i.e., the imager mode with narrow (or wide) band filters, the long-slit spectrograph mode for area spectroscopy by means of spacial scans, the Fabry-Perot interferometer imager mode, and the microlens-array (MLA) spectrograph mode. Selection of the mode is made by moving optical parts relevantly in the spectrograph. The principles of the optics of the first three modes are ordinary ones. In the imager mode, a field lens is inserted behind the telescope focus and filters are set between the collimator and the camera lenses, while a Fabry-Perot etalon is inserted instead of the filters in the Fabry-Perot imager mode. In the long-slit mode, a slit is set at the telescope focus, and a grism replaces the filters or the etalon. The principle of the MLA spectrograph mode is essentially same as that of TIGER for the Canada-France-Hawaii telescope. Our spectrograph, however, is equipped with a dual-channel preoptics system for the MLA, one channel acquiring a target object and the other the neibouring sky appreciabily apart from the target object. The image of the sky is projected on the microlenses along a side of the array of the microlenses. The spectra of the sky are used to eliminate of contamination by sky background from spectra of the target object. The design of this spectrograph is primarily optimized for the MLA spectrograph mode at the 1.88 m telescope at Okayama. With this telescope, about eighty spectra of an area about 9# x 15 of an object and fourteen spectra of the nearby sky are obtained with a spacial resolution of 1.3" which matches the average seeing size at the telescope site. Performances of this spectrograph when it is used for other telescopes, including the SUBARU, are also presented.
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