Guoxiong Zhang

A Confocal Probe based on Time Difference Measurement

Abstract A low cost confocal probe based on time difference measurement has been developed. A tuning fork is used to modulate the focal length of the probe. An auxiliary arm is introduced to the optical system. This arm can be utilized for carrying out lateral measurement or for providing a reference signal. The position of the surface is determined by measuring the time difference between two successive peak intensities of the measuring signal or that between peak intensities of measuring and reference signals. Some key problems in probe design are discussed. A correlation based technique for determining the time difference between two peak pulses is developed. Error compensation technique for nonlinearity and other errors is introduced. The excellent performance of the probe has been proven by experiments.

Structure Design of A Laser Confocal Probe For Measuring the Micro-Sphere

To achieve the aim of precise position measurement of a target micro-sphere, approximately 0.2mm in diameter, a laser confocal probe, on an active focus adjusting principle, was introduced in this paper. For finding the effect way to improve the output signal, a mathematical modal of the photoelectric signal was proposed. Based on the mathematical modal, the diameter of the pinhole was decided and the optical path was adjusted, which forward the performance of the probe. The tuning fork stimulating, inductive coils and the pinhole adjuster device were designed according to the theoretical analysis, which were more convenient to the measure task. The stability of the intact oscillating unit was tested; and the optical and mechanical performance of the probe was validated by experiments using gage blocks combining with a calibrated micro-driven table. Besides, a more accurate signal processing method was suggested in this paper.

In-situ optical measurement of separation angles between bifacial lines in large scale space

An optical method is proposed for in-situ measurement of angles of space elements separated at a distance of several or several tens of meters. When it is necessary to measure large objects or geometrical elements within a large scale space, it is not always possible to bring these workpieces to conventional coordinate measuring machines (CMMs) which are widely used in industries. Mobile measuring systems provide ideal solutions for these applications. The basic idea of the presented research work is to set up the multiple common optical references through which the dimensional inspections of separation angles of bifacial lines in a large scale space can be fulfilled. The angles between the projection light and each element can be captured through a machine vision system, and thereafter the angles between those corresponding elements can be determined using the geometrical principles. The method and the calibration approach have been validated on our designed work station.