Development of a Resonant Scanner to Improve the Imaging Rate of Astigmatic Optical Profilometers

An astigmatic optical profilometer provides numerous advantages such as compact size, low cost, and high resolution. In 2018, a
z
-axis modulation mode of the astigmatic optical profilometer was developed to realize quantitative height measurement for a surface comprising complex materials. However, the current imaging rate of the
z
-axis modulation mode is time-consuming. In this article, a resonant scanner was proposed to execute a high-speed
z
-axis scanning motion. By inducing the resonant mode, the resonant scanner enabled both a large travel range of over 87
μ
m and high oscillation frequency of 1.576 kHz. Additionally, a data analysis process was proposed to calibrate the nonlinear movement of the resonant scanner. Experimental results demonstrated that the developed optical profilometer successfully captured the quantitative height and reflectivity of the complex material comprising chrome patterns on a glass substrate. Furthermore, an imaging rate of 256 s/frame was achieved, which was approximately 50 times faster than that of a previous system employing a commercial flexure-guided scanner.