Research For The Multi-beam Interference Microscopy Probe For Ultra-smooth Surface

This project is to design a multi-beam interference microscopy probe used toUltra-smooth surface measurement. The optical structure is the main part of thesystem, and the signal processing circuit element is the auxiliary part. Axialresolution is one of the most important performance of optical probe, and the coreto ensure the resolution of the system is the optical structure.Optical structure is divided into two parts to design:1) Multi-beaminterference;2) Confocal microscopy. The multi-beam interference is to ensure theaxial resolution of the system, and the confocal microscopy technology is used toquickly and accurately find the system work area and accumulate the technology ofthe next step of horizontal resolution. The signal processing circuit is divided intothree parts:1) photo-electric conversion circuit;2) signal conditioning circuit;3)filter circuit. photo-electric conversion circuit is used to achieve the change of lightintensity signals to electrical voltage signals, the signal conditioning circuit is tocomplete the preprocessing of the two voltage signals according to thecharacteristics of the optical signals. Filter circuit is to eliminate the noise andinterference which cased by the environment to ensure the resolution of the system.The main work of this project completed as follows:1) Designed a optical structure of confocal multi-beam interference microcopyprobe which have a differential path.2) Introduce the basic theory of multi-beam interference and confocalmicroscopy technology which used in the optical structure.3) Derivation the distribution curve of the interference fringes of the opticalsystem.4) Design the optical parameters, includes: the best reflectivity of theReflection plate is40%, the diameter of the Pinhole is300um, the optical pathbetween the Measurement lens and the Acquisition lens is80mm.5) Design the photo-electric conversion circuit, design the signal conditioningcircuit according to the characteristics of the curve of the interference fringes of theoptical system, design the filter circuit according to the characteristics of theambient noise. 6) Verify the practicality of the signal conditioning circuit and the filter circuitby experiment.7) Test the curve of the interference fringes of the system, the phase error ofthe two interference fringes between the P light and S light, the axial resolution ofthe system, and calibration the Nanopositioning which used in the test of axialresolution.