Design and Development of an Adaptive Optical Phase Compensation Device for Volume Hologram Exposure Technology

• Main Authors: Hung-Lin Wu, 吳泓霖
• Other Authors: Kuang-Yuh Huang
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/s2qs2x

碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === Volume hologram technique is one of a holographic projection with high angle sensitivity. It is often used as an optical filter to pure the light source and select a specific angle or wavelength. Recently, volume hologram technique often uses to make into multi-focal lens, by recording different light shapes at different angles on Volume hologram sheet, which apply in medical development scanning, which can effectively improve the scanning speed. However, when recording diffraction gratings, the laser phase is often unstable, and it will affect diffraction grating on Volume hologram sheet, reducing the diffraction efficiency. In order to improve the diffraction efficiency, this paper attempts to introduce an active optical phase compensation device into the volume holographic exposure system, which has stabilized the phase change of the laser. The adaptive optical phase compensation device is an optical feedback system, and most of the applications are in the space telescope to achieved the effect of correcting images. In this paper, digital micro-mirror display (DMD) and mechanical two methods are used for phase compensation. DMD produces digital holographic image, and the angle of the diffracted light is corrected by adjusting the digital holographic grating, which has high reproducibility and precision and high correlation coefficience up to 0.9091. The resolution of changing angle can reach 3.49 urad. The DMD adaptive optical phase compensation device can compensate the frequency up to 11 Hz and can effectively reduce the oscillation of the horizontal tilt angle. However, the digital hologram will produce multi-order diffracted light, which will damage the volume hologram gratings during exposure process. Therefore, this paper designs and develops a two-dimensional galvo-mirror for mechanical adaptive optical phase compensation device for feedback laser beam tilt angle to improve laser stability. The servo motor is used to drive the precision screw to push the mirror to rotate, and the tension spring is used to provide the galvo-mirror restoring force and reduce the precision screw clearance to achieve higher precision. After reducing structure, the resolution can reach 0.087 urad. In the five-time laser beam phase compensation test, the peak error of the optical axis tilt angle is significantly reduced after phase compensation. In order to reduce the volume hologram gratings exposure process, this paper sets up an automated system to achieve automatic exposure system.