Four-beam laser interferometry for three-dimensional microscopic coordinate measurement.
We propose a new method for calibrating the three-dimensional (3-D) behavior of a scanning stage. Four laser interferometers are used to determine the position of the corner point of a corner mirror attached to the stage. We calculated the 3-D coordinate of the corner point by using only the length information given by the four laser interferometers; thus a method is realized that is traceable from the practical definition of length and that facilitates the optical alignment that is necessary for the interferometers. We calibrated a commercial 3-D stage by the proposed method with a coordinate accuracy of 20-30 nm.
Modeling and algorithm of attitude measurement of moving target by laser tracking systems
We demonstrate theoretically the feasibility of the full-attitude measurement of a moving target by laser tracking systems. Based on the combination of retroreflector target, laser tracking, and interferometry techniques, two kinds of laser tracking systems known as distance- angle-measurement (DAM) and distance-only-measurement (DOM) sys- tems are proposed for the attitude measurement of a moving target in real time. Mathematical models and algorithms of both systems are built to determine and calculate the dynamic attitude of the target under the world coordinate system and the target's initial coordinate system re- spectively. The coordinate transform between different coordinate sys- tems and the initial geometric parameters of the laser tracking stations can be self-calibrated. The coordinate transform self-calibration algo- rithm can be solved by the singular matrix decomposition method, while the self-calibration algorithm of the initial geometric parameters of the DOM system can be solved by the Levenberg-Marquardt method. The simulation results show that the self-calibration algorithm converges rap- idly and its accuracy is satisfactory under noise measurement. © 2003
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine