title: Effects of phosphor-based LEDs on vertical scanning interferometry.
abstract: High-power phosphor-based LEDs are replacing conventional white-light sources for vertical scanning interferometry, but the spectrum of the phosphor-based LED is different from that of the conventional light source. The phosphor-based LED has two peaks in its spectrum, while the conventional light source has only one peak in the Gaussian distribution. In this Letter, we investigate the effects of phosphor-based LEDs on vertical scanning interferometry. Our result shows that the use of a phosphor-based LED changes the fringe contrast function significantly, such that measurement repeatability decreases. We propose and demonstrate that a constraint on the input to the existing reconstruction algorithm improves the repeatability of the vertical scanning interferometer with a phosphor-based LED.
authors.affiliation: Precision Measurement Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075, Singapore. wkchong@simtech.a-star.edu.sg
authors.forename: Wee Keat
authors.initials: WK
authors.lastname: Chong
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.forename: Sardha
authors.initials: S
authors.lastname: Wijesoma