Eliminating the influence of source spectrum of white light scanning interferometry through time-delay estimation algorithm

• Published in: Optics communications Vol. 391; pp. 1 - 8
• Main Authors: Zhou, Yunfei, Cai, Hongzhi, Zhong, Liyun, Qiu, Xiang, Tian, Jindong, Lu, Xiaoxu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2017
• Subjects: Interference signal envelope; Profile measurement; Time-delay estimation; White light scanning interferometry (WLSI); Time-delay estimation; Interference signal envelope; Profile measurement; White light scanning interferometry (WLSI)
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2016.12.006

In white light scanning interferometry (WLSI), the accuracy of profile measurement achieved with the conventional zero optical path difference (ZOPD) position locating method is closely related with the shape of interference signal envelope (ISE), which is mainly decided by the spectral distribution of illumination source. For a broadband light with Gaussian spectral distribution, the corresponding shape of ISE reveals a symmetric distribution, so the accurate ZOPD position can be achieved easily. However, if the spectral distribution of source is irregular, the shape of ISE will become asymmetric or complex multi-peak distribution, WLSI cannot work well through using ZOPD position locating method. Aiming at this problem, we propose time-delay estimation (TDE) based WLSI method, in which the surface profile information is achieved by using the relative displacement of interference signal between different pixels instead of the conventional ZOPD position locating method. Due to all spectral information of interference signal (envelope and phase) are utilized, in addition to revealing the advantage of high accuracy, the proposed method can achieve profile measurement with high accuracy in the case that the shape of ISE is irregular while ZOPD position locating method cannot work. That is to say, the proposed method can effectively eliminate the influence of source spectrum. •We propose time-delay estimation (TDE) algorithm to eliminate the influence of source spectrum in white light scanning interferometry (WLSI).•When the spectral distribution of source is irregular, the conventional zero optical path difference (ZOPD) position locating method cannot work well, but the proposed method can be used well.•For the proposed method, the surface profile information is achieved by using the relative displacement of interference signal between different pixels instead of the conventional ZOPD position locating method.•Due to all spectral information of interference signal (envelope and phase) are utilized, in addition to revealing the advantage of high accuracy, the proposed method can achieve profile measurement with high accuracy.