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

我们研制了一种具有纳米级高度分辨率的高速垂直扫描轮廓仪。所研制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通滤光器和超高功率发光二极管(LED)组成。在三维轮廓测量中，这种轮廓术在垂直扫描具有0.4微米步进和交替闪烁的LED的Mirou型物镜时记录了许多干涉图。奇数干涉图用503 nm发光二极管捕捉，偶数干涉图用591 nm发光二极管捕捉。对于记录的干涉图，计算机利用相移技术提取相位和调制幅度。在同一发光二极管的连续采集之间进行两步运动，相位步长约为6ππ/2(503 Nm)和约6π-π/2(591 Nm)。在搜索有调制峰的干涉图后，计算机从相位信息中提取出具有纳米分辨率的干涉图捕获时刻的光程差。在垂直步长为0.4μm，捕获速率大于110 Hz的情况下，垂直扫描速度超过46μm/S。这种速度是商用高速垂直扫描轮廓仪的四倍

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