To achieve high-resolution image using optical synthesis aperture telescope, it’s necessary to co-phase accurately of all the telescopes so as to reduce the effect of co-phase errors including piston error, tip/tilt error, and mapping error, etc. Though simulation analysis of the optical system, error sources can be identified and thus save time of alignment. This paper introduces the Fizeau-type Y-4 prototype under development, including the layout of the Y-4 prototype, the layout of the reflective mirrors in the delayed light paths and the beam combiner. With the optical transfer function as the evaluation index, the actual equivalent diameter of Y-4 prototype is calculated. Furthermore, the effect of polarization introduced by coating and polarization differences on the contrast of interference fringe is analyzed. At present, the installation and alignment of the prototype in laboratory have been completed, and the interference synthesis of 4 light paths has been realized. One aim of this paper is to share some experiences in optical design and detection for the development of optical synthetic aperture telescopes. Another aim is to expand these new techniques to the larger optical synthesis aperture telescope project in the future.
In general, most of the adaptive optical systems for human eye aberration detection are based on the wavefront slope measurement provided by the Shark-Hartman wavefront sensor (SHWS), and then the wavefront slope is fed back to the deformable mirror to correct the human eye aberrations. Compared with the SHWS, the pyramid wavefront sensor (PWS) has the characteristics of fast sampling speed, wide linear capture range, and high sensitivity. Our works show that the modulation angle of the dynamic high-frequency modulator affects the dynamic measurement range, linearity and sensitivity of the pyramid sensing. The dynamic measurement range and the linear fitting residuals are both proportional to the modulation angle, and the sensitivity is inversely proportional to the modulation angle. Pixel combination affects the sensitivity of the detection signals of the pyramid sensor. The pixel combination mode of 1 × 1, 2 × 2, and 3 × 3 is tested respectively. When the pixel combination mode of 2 × 2 is used, the sensitivity of the signals will be highest significantly. In addition, the beacon light used to detect the human eye should not be too strong. The grinding “blind zone” of the spires and edges will have a scattering effect on the incident light and cause loss of light energy. Therefore, it is necessary to optimize the parameters of the pyramid sensor and further improve the processing technology of the pyramid prism.
Deformable mirror (DM) is the most main wavefront corrector in adaptive optics, which can be used to compensate optical aberrations through changing the reflective mirror’s surface frequently. However, a commercial piezoelectric DM can’t have an ideal flat initial surface under zero-voltage condition due to limitation of thin mirror fabrication and support structure of actuators behind of mirror. Optical aberrations generated by this initial distortion will seriously attenuate the performance of DM’s close-loop control, so a flat-surface calibration of mirror needs to be carried out before DM properly correct optical aberrations. In order to properly control the optical figure of the DM we have to obtain an interactive matrix which is the response of optical surface to the DM actuator’s stroke. We measured a serious of surface phase data of OKO 109-channel DM through self-collimation using a ZYGO-GPI interferometer directly, then construct the interactive matrix by zonal and modal methods. After several close-loop iterations, the initial RMS surface error of OKO 109-channel deformable mirror, 1.506λ has been remarkably reduced to 0.145λ.
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