An optimized design of a scanning confocal probe

Abstract

Basing on the principle of dynamic active confocal measuring method, a non-contact probe was introduced. The relation between the displacement of the object measured and the displacement of the oscillating unit was established by applying to the measure principle. To find the effect way to improve the output signal, a mathematical modal of the photoelectric signal was proposed. According to the mathematical modal, the diameter of the pinhole was decided and the optical path was adjusted, which improved the performance of the probe. It valuable to emphasize that the double lens oscillating unit was the crucial parts of the mechanical and optical structure. The tuning fork stimulating, inductive coils and the pinhole and photodiode adjuster device were designed according to the theoretical analysis, which were more convenient to the measure task. The stability of the oscillating unit was tested; and the optical and mechanical performance of the probe was validated by experiments using gage blocks combining with a micro-motion measuring mount model. The cost of a micro-displacement testing sensor was saved in designing of this kind of probe. A more accurate signal processing method was discussed in this paper.