Reflection-mode digital gradient sensing method: measurement accuracy

Chengyun Miao; Hareesh V. Tippur

doi:10.1117/1.OE.58.4.044101

5 April 2019 Reflection-mode digital gradient sensing method: measurement accuracy

Chengyun Miao, Hareesh V. Tippur

Author Affiliations +

Optical Engineering, Vol. 58, Issue 4, 044101 (April 2019). https://doi.org/10.1117/1.OE.58.4.044101

Abstract

Surface topography evaluation from measured surface slopes is critical in many engineering applications, including metrology of electronic substrates, optical elements, and small deformation measurement of engineering structures subjected to external thermomechanical stimuli. A recently proposed noncontact full-field optical method called reflection-mode digital gradient sensing (r-DGS) is able to measure small angular deflections of light rays proportional to two orthogonal surface slopes. It has been shown that submicron scale deformations can be detected by processing the slope data using a robust numerical integration scheme called the higher-order finite-difference-based least-squares integration. However, the smallest measurable deformations and the associated accuracy are yet to be determined. In our work, this very issue is addressed by carrying out experiments at temporally different recording frequencies, namely (a) ultrahigh-speed digital photography at 10⁶ frames per second (fps) and (b) slow recording speeds of 10¹ fps. The results show that r-DGS is able to measure submicron out-of-plane deformations under latter conditions and nanoscale deformations in the former conditions.

Citation Download Citation

Chengyun Miao and Hareesh V. Tippur "Reflection-mode digital gradient sensing method: measurement accuracy," Optical Engineering 58(4), 044101 (5 April 2019). https://doi.org/10.1117/1.OE.58.4.044101

Received: 30 January 2019; Accepted: 11 March 2019; Published: 5 April 2019

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