Characteristics And Image Restoration Research On Reflection-type Terahertz Confocal Scanning Imaging

As the combination of THz imaging and laser confocal scanning microscopy, it is a new trial of THz imaging system. Compared to transmission-type system, the situation of reflection-type is more usful. In optical microscopy area, the high resolution imaging is an important target to be pursued. As for the reflection-type system, confocal pinhole size and the offset of cell detector are vital factors that influence the system resolution. THz radiation has a higher wave length than visible region and the existing THz laser outputs unstably, the imaging quality is severe when the pinhole size is reduced. The study on the influencing factors of reflection-type THz confocal scanning system is very necessray. The improvement of imaging quality is also important.For the purpose of improving the axial resolution of THz confocal scanning microscopy, the 2.52 THz biaxial reflection-type imaging scheme is designed. The influences of incidence angle and detecor 3D offset on the axial, transverse and vertical resolutions are emulated. Simultaneously, for analysis and comparison, the influence of detecor offset on the system resolution is also studyed in coaxial reflection-type system. The sutdy is also focused on the influence of confocal pinhole size on system resolution and receiving light intensity. To improve the spatial resolution of reflection-type system, the situation of adding the annular pupil is emulated.The experiment data of scanning the 0.4mm copper clad PE board whth 0.2mm step length is analysed. The situations when the pinhole is 75 mm away and when the pinhole is tightly appressed to the surface from the photosurface are discussed. The practical influence of confocal pinhole size and detector offset on system resolution and receiving light intensity is studyed. To discuss the axial resolution of the system, the imaging results of two couples of metal strips are analysed.Against the imaging characteristic of our system, we discussed the best parameters of BF, NLM and GF. On the basis above, synthesis comparison about three algorithms is executed. Finally, comparison about three algorithms used in the image result of r=0.3mm biaxial system is executed.