Digital holography with two wavelengths that are close to each other is applied to the height measurement of solder bumps having a spherical specular surface and a height of several tens of micrometers. To meet industrial requirements, the error should be less than about1 μ m, and therefore the two wavelengths should have a difference of just a few nanometers for digital holographic measurement. In this research, an optical system in which two beams with wavelengths that are close to each other travel in opposite directions when they enter and exit the interferometer was developed for the first time. The main feature of the optical system is that it requires no special optical element for separating the two wavelengths. In this paper, we describe the position calibration of two cameras that support two-wavelength measurement, the accuracy evaluation of the digital holography, and the height measurement of the solder bumps.

中文翻译：

---

数字全息技术，具有两个接近的波长，用于测量焊料凸点的高度

将具有彼此接近的两个波长的数字全息术应用于具有球形镜面表面和数十微米高度的焊料凸块的高度测量。为了满足工业要求，误差应小于约1μm，因此，对于数字全息测量，两个波长之间的差值应仅为几纳米。在这项研究中，首次开发了一种光学系统，其中波长彼此接近的两个光束在进入和离开干涉仪时以相反的方向行进。光学系统的主要特征在于，它不需要用于分离两个波长的特殊光学元件。在本文中，我们描述了支持两波长测量的两台摄像机的位置校准，