| Many of the modern industrial products have complicated surfaces, thus it is necessary to obtain the surface topography and the characteristic parameters of the objects. The surface topography measuring instrument is applied to detect the surface profiles of the objects and is widely used in the mold manufacturing. One of the most important surface topography is the surface roughness that affects the performance and the life of the mechanical devices. The current mainstream surface roughness measuring instruments contain the probe profiler, optical probe profiler, and the interference microscope etc. However there are several disadvantages in these instruments such as big noise, low precision and so on. To overcome these problems, in this thesis we have designed the common path and aplanatism differential interference surface topography profiler.This thesis has established the common path between and the reference light and the measuring light aplanatism interference system based on the self-adaption pure optical method and the birefringence of the uniaxial crystal. The system eliminated the influences to the measuring results those come from the wavelength and instability of the light source, and the variation of the refractive index of the air. This thesis has applied the LED as the weak interference light source because that it is able to improve the measuring precision by the weak signal measuring technology. The weak signal measuring method killed the impact on the measuring results from the white noise and increased the accuracy of the whole system.Using the optical designing software ZEMAX, the transfer properties and the energy distribution of the interference system have been studied in the thesis. According to the spatial and time coherence of the weak light source, the smaller of the light source leads to the better spatial coherence. We have found the appropriate size of the spatial filter by adjusting the radius of its aperture and further obtained the high quality interference pattern. We have made a general model of the differential phase shifting surface profiler in the ZEMAX and used it to measure a standard spherical surface. The results demonstrated that the simulated interference pattern of the spherical surface matched well with its real pattern. Comparing the simulation and the experimental results, it is shown that the general model based on the ZEMAX can make a good simulation to the experimental system. Then on the platform of the general interference model based on the ZEMAX, this thesis has analyzed various factors that may affect the performance of the interferometer.To further prove the reliability of the measuring system, we have measured the surface topographies of several standard samples. The good agreement between the experimental data and the standard surface roughness indicates that the system has high reliability. Moreover, we have investigated the horizontal resolution, perpendicular resolution, and the range of the height measuring of the system. The sources of the errors and the influences to the measuring results due to the errors have also been discussed in this thesis. |
