Department of Electrical Engineering, Koç University, Sariyer, Istanbul 34450, Turkey.
Opt Lett. 2011 Jun 15;36(12):2254-6. doi: 10.1364/OL.36.002254.
Dynamic diffraction gratings can be microfabricated with precision and offer extremely sensitive displacement measurements and light intensity modulation. The effect of pure translation of the moving part of the grating on diffracted order intensities is well known. This study focuses on the parameters that limit the intensity and the contrast of the interference. The effects of grating duty cycle, mirror reflectivities, sensor tilt and detector size are investigated using Fourier optics theory and Gaussian beam optics. Analytical findings reveal that fringe visibility becomes <0.3 when the optical path variation exceeds half the wavelength within the grating interferometer. The fringe visibility can be compensated by monitoring the interfering portion of the diffracted order light only through detector size reduction in the expense of optical power. Experiments were conducted with a grating interferometer that resulted in an eightfold increase in fringe visibility with reduced detector size, which is in agreement with theory. Findings show that diffraction grating readout principle is not limited to translating sensors but also can be used for sensors with tilt or other deflection modes.
动态衍射光栅可以精确制造，提供极其灵敏的位移测量和光强调制。众所周知，光栅运动部分的纯平移对衍射级强度有影响。本研究集中于限制干涉强度和对比度的参数。利用傅里叶光学理论和高斯光束光学研究了占空比、反射镜反射率、传感器倾斜和探测器尺寸对光栅的影响。分析结果表明，当光栅干涉仪内的光程变化超过半波长时，条纹可见度会降至<0.3。通过减小探测器尺寸，可以仅通过减小探测器尺寸来补偿干涉部分的衍射光的干涉条纹可见度，从而牺牲光功率。通过光栅干涉仪进行了实验，结果表明，减小探测器尺寸可使条纹可见度提高八倍，这与理论相符。研究结果表明，衍射光栅读出原理不仅限于平移传感器，也可用于具有倾斜或其他偏折模式的传感器。
