Joo Kyung-Il, Park Chang-Sub, Park Min-Kyu, Park Kyung-Woo, Park Ji-Sub, Seo Youngmin, Hahn Joonku, Kim Hak-Rin
School of Electrical Engineering and Computer Science, Kyungpook National University, Buk-gu, Daegu, Korea.
Appl Opt. 2012 May 10;51(14):2624-32. doi: 10.1364/ao.51.002624.
Optical profilometry is widely applied for measuring the morphology of objects by projecting predetermined patterns on them. In this technique, the compact size is one of the interesting issues for practical applications. The generation of pattern by the interference of coherent light sources has a potential to reduce the dimension of the illumination part. Moreover, this method can make fine patterns without projection optics, and the illumination part is free of restriction from the numerical aperture of the projection optics. In this paper, a phase-shifting profilometry is implemented by using a single liquid crystal (LC) cell. The LC phase modulator is designed to generate the interference patterns with several different spatial frequencies by changing selection of the spacing between the micro-pinholes. We manufactured the LC phase modulator and calibrated it by measuring the phase modulation amount depending on an applied voltage. Our optical profilometry using the single LC cell can generate multi-spatial frequency patterns as well as four steps of the phase-shifted patterns. This method can be implemented compactly, and the reconstructed depth profile is obtained without a phase-unwrapping algorithm.
光学轮廓术通过在物体上投射预定图案来广泛应用于测量物体的形态。在这项技术中，紧凑的尺寸是实际应用中一个有趣的问题。通过相干光源的干涉产生图案有潜力减小照明部分的尺寸。此外，这种方法无需投影光学器件就能制作精细图案，并且照明部分不受投影光学器件数值孔径的限制。在本文中，通过使用单个液晶（LC）单元实现了相移轮廓术。LC 相位调制器被设计成通过改变微针孔之间间距的选择来生成具有几种不同空间频率的干涉图案。我们制造了 LC 相位调制器，并通过测量取决于施加电压的相位调制量对其进行了校准。我们使用单个 LC 单元的光学轮廓术能够生成多空间频率图案以及四步相移图案。这种方法可以紧凑地实现，并且无需相位展开算法就能获得重建的深度轮廓。
