**5. Conclusions**

This paper investigated an AOTF-based 10 nm spectral resolution HSL, and for which the consecutive spectral bands were tunable covering 500–1000 nm. An AOTF was installed after the super-continuum laser source and consecutively selecting the wavelength of the passing laser beam. 51-channel spectral information was acquired. Then, four different plants with four green leaves and two yellow leaves were measured by the AOTF-HSL and with corresponding referenced spectral profiles collected by an SVC spectrometer. For green leaves, the "Red Edge"-related parameters extracted using the first-order reflectance slope (FRS) from the AOTF-HSL and SVC spectrometer were trivial, and this demonstrated the AOTF-HSL was capable of measuring vegetation "Red Edge"-related parameters. Moreover, the observed shift behaviours were consistent with previous research results, which also supported the fact that measurement results from the AOTF-HSL are reliable. In addition, another two methods, LFPIT and LET, were employed for calculating the REP for further comparing the results between HSL and SVC. The results were similar to those from the FRS method, which further demonstrated the effectiveness of the HSL in this vegetation index detection and measurement.

**Author Contributions:** C.J. wrote this paper and processed the data; Y.C. proposed the idea, revised the paper designed this HSL and offered the funding; W.L. set up the HSL, the idea, collected the data, revised the paper and offered the funding; H.Z. discussed the idea and revised the paper; H.J. offer the funding, revised the paper and the guided the HSL design. Y.B., H.S., S.S. and E.P. reviewed the paper and provided valuable advice for paper writing and revision.

**Funding:** This research was financially supported by the Academy of Finland projects "Centre of Excellence in Laser Scanning Research (CoE-LaSR) (307362)" and "New laser and spectral field methods for in situ mining and raw material investigations (project 292648). Additionally, the Chinese Academy of Science (181811KYSB20160113), by the Chinese Ministry of Science and Technology (2015DFA70930) and Shanghai Science and Technology Foundations (18590712600) are acknowledged.

**Conflicts of Interest:** The authors declare no conflict of interest.
