Test methodFull-field deflection measurement of the flexible transparent sheets

Because flexible transparent sheets (FTSs) have high transmittance and large deflection, their full-field deflections are difficult, or even impossible, to obtain experimentally. This study proposes a methodology based on Twyman-Green interferometry to measure the full-field deflection of FTSs. Several polyethylene terephthalates (PETs) with known deflections were prepared to verify the measurement precision of the proposed methodology. Results show that the proposed methodology can be used to measure full-field deflection up to 6.5 mm. The existing fringe of the null field significantly influences the measurement results under small deflections. To the authors' best knowledge, this is the first full-field and non-contact method of measuring the deflection of FTSs.