Surface characteristics are of vital importance for predicting the product life time and surface functionality, or even improving the manufacturing procedure. In consequence, this thesis focuses on the surface inspection using a non-contact technique.
The principle of Confocal Microscopy(CM) enables light microscopes to gain depth information through what is known as depth discrimination ability. Among the other optical inspection techniques, the principle of confocal microscopy allows a parallel and motionless depth scanning scheme to be developed. The chromatic confocal point sensor is one prominent example of a parallel depth scanning scheme. However, this technique requires a separate analysis unit to analyze light of different wavelengths. The complication and relatively low efficiency of light per wavelength can pose a limit on developing a simplified configuration and a cost effective unit.
Therefore, a novel approach to incorporate a tilted plane technique in a confocal imaging system is proposed in this thesis, namely a Confocal Line Scanning Sensor (CLSS). A parallel and motionless depth scanning scheme is then achieved with a cost-effective technique, resulting in a greatly simplified and robust configuration.
This thesis is devoted to establish new knowledge on incorporating a tilted plane technique in a confocal imaging system. A novel approach to explain and to correct the variation of the magnification inherent in a tilted plane system, known as keystone distortion, is proposed. Moreover, particular data processing and calibrations are developed to support the new concept. Here, the Scheimpflug's principle is first applied with confocal microscopy, whereas selected well-known theories are also used to support the system design and construction.
Finally, the experiments demonstrate that a tilted plane technique can successfully be incorporated in a confocal imaging system. In addition, the performance of the CLSS is evaluated through a series of experiments.