Research Of Two-Step Phase-Shifting Wide-Field Three-Dimensional Microscopy Based On Scattering Of Intermediary Layer

The curved optical components include curved optical components with microstructure and continuous curved optical components. Optical systems composed of these optics have significant advantages in imaging, thus they are applied widely. But, it is difficult to measure these optics by conventional optical methods. The reason is that in optical measurement systems such as confocal and interferometer microscopes, imaging light beams on the curved optical components were reflected away from imaging axis because of reflection laws, and this lead to imaging distortion. We should break through the imaging problem to solve the inspection problem.Therefore, this research of two-step phase shifting wide-field 3D microscopy based on scattering of intermediary layer is to provide techniques and theories support for the high-speed and wide-field optical 3D microscopy imaging of the curved optical components. The following are the major issues addressed by this study:Firstly, to investigate the reason for the imaging problem of curved optical components, the effective pupil model and optical transfer functions of sectioning structured illumination wide-field three-dimensional imaging microscopy(SSIWM) for curved optical components were built and derived. Then the cut-off frequency mathmatical expressions and several typical cases were investigated for various local slope angles and numerical apertures. This study solved the evaluation of imaging ability problem for curved optical components that are measured in SSIWM systems. This study can provide theoretical basement for SSIWM based on scattering of intermediary layer.Secondly, SSIWM based on scattering of intermediary layer was proposed for the optical imaging problem of the curved optical components. The method used SSIWM in the imaging of the sample with an uniform and easily removed fluorescent intermediary layer. Thus it changed the specular reflection to scattering, and made the imaging pupil full of imaging lights which can overlap the illumination pupil and imaging pupil. The proposed method can make the resolution of zones with various slope angles the same. So, the method solved the signal losing and imaging distortion problem, and can fullfil high-speed 3D wide-field imaging for the curved optical components.Thirdly, a two-step phase-shifting SSIWM(two-step method) was proposed for the strip artefacts problems of in-focus images resulting from the cosinesoidal phases mismatch of spatial domain in conventional three-step phase-shifting SSIWM. The two-step method resolved the cosinesoidal modulated in-focus structures using base frequency filtering of the two-step images difference. Compared with the conventional three-step method, it can avoid strip artefact and the phase-shifting steps decreases from 3 to 2. This reduces 1/3 illumination time, and thus decreased the possibility of photo-bleaching. It also reduce 1/3 of the whole data collecting time. Additionally, the method can be applied in conventional three-step system as a module without system modification.At last, a SSIWM experimental setup was designed and developed based on the above analysis and the proposed method. The micro-cylindrical surface was tested on the setup to verify the validity of the proposed methods. The experimental results showed that the strip artefacts shown in the three-step method can be avoided in the two-step method, and the slope angle that can be imaged was larger than which is 3.38 times as large as the angle obtained by conventional SSIWM with the same numerical aperture. The wide-field 3D microscopy based on scattering of intermediary layer can fufil imaging of curved optical components, and two-step phase-shifting method is better than the three-step method.