Vertical-scanning profilometry having nanometric height resolution and high scanning speed using two short-coherent-light sources of different wavelengths

我们开发了一种高速垂直扫描轮廓术，具有纳米级的高度分辨率。所开发的轮廓术配备了两个短相干光源。这些光源由两种类型的带路滤波器和极高功率发光二极管（LED）制成。在三维轮廓测量中，该轮廓测量法记录了许多干涉图，同时以0.4微米步进和交替闪烁LED垂直扫描mirou型物镜。奇数干涉图用503纳米的LED捕获，偶数干涉图用591纳米的LED捕获。对记录的干涉图，计算机采用移相技术提取相位并调制幅值。由于在同一LED的连续捕获之间放置两个步进运动，相位步进对应于503 nm的约6π+π/2和591 nm的约6π-π/2。计算机在搜索具有调制峰的干涉图后，从相位信息中提取出纳米分辨率的干涉图捕获时刻的光程差。在垂直步长为0.4 μm，捕获速率大于110 Hz的范围内，垂直扫描速度大于46 μm/s。这个速度是商用高速垂直扫描轮廓术的四倍

We developed a high-speed vertical scanning profilometry which has nanometric height resolution. The developed profilometry is equipped with two short-coherent-light sources. These sources are made with two types of band-path filter and extremely high power light emitting diodes (LED). In 3-D profile measurements, this profilometry records many interferograms while vertically-scanning the Mirou-type objective with 0.4-micrometers step and alternately-flashing LED. Odd-numbered interferograms are captured with 503-nm LED and even-numbered interferograms are with 591-nm LED. Regarding the recorded interferograms, a computer extracts phase and modulation amplitude using phase-shifting technique. As two step movements are put between the sequential captures with the same LED, phase step corresponds to approximately 6π+π/2 with 503 nm and approximately 6π-π/2 with 591 nm.After searching the interferogram having modulation peak, the computer extracts optical path difference at the capturing moment of the interferogram with nanometric resolution from phase information.From 0.4 μm of the vertical step length and capturing rate more than 110 Hz, vertical scanning speed is given more than 46 μm/s. This speed is four times higher than commercial high-speed vertical scanning profilometry