In this study, we evaluated the influence of retrieval algorithms and sensor characteristics, such as spectral resolution (SR) and signal to noise ratio (SNR), on the retrieval accuracy of fluorescence signal (Fs). Here Fs was retrieved by four commonly used retrieval methods, namely the original Fraunhofer Line Discriminator method (FLD), the 3 bands FLD (3FLD), the improved FLD (iFLD) and the spectral fitting method (SFM). Fs was retrieved in the oxygen A band centered at around 761nm (O2-A). We analyzed the impact of sensor characteristics on four retrieval methods based on simulated data which were generated by the model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes), and obtained consistent conclusions when compared with experimental data. Results presented in this study indicate that both retrieval algorithms and sensor characteristics affect the retrieval accuracy of Fs. When applied to the actual measurement, we should choose the instrument with higher performance and adopt appropriate retrieval method according to measuring instruments and conditions.
In the development and production process of laser gyros, reflective mirrors have always been a core component, as they are directly related to the performance of laser gyros. Besides, surface profile deviation and surface defects of mirrors may lead to irreversible serious damages to gyros. In order to achieve effective three-dimensional (3D) quantitative measurements of their surface profiles and defects, we adopt digital holographic microscopy (DHM). Using a DHM system with multiple magnifications and the aberration compensation method, we obtained 3D profile images and estimated the precise quantitative sizes of not only a profile with an aperture of 6.41 mm and a curvature radius of 8.39 m, but also a scratch with a line-equivalent width of 0.45μm and an equivalent depth of 137.28 nm and a pit with an equivalent diameter of 0.86μm and an equivalent depth of 42.95 nm. These results demonstrate that the method is feasible and effective to meet the requirements of engineering practice.