Multidirectional Interferometer Research Articles

Three-dimensional modeling of the instantaneous temperature distribution in a turbulent flame using a multidirectional interferometer

We have reconstructed a three-dimensional instantaneous temperature distribution inside the turbulent flame of a propane-air premix burner using multidirectional holographic interferograms by constructing a geometric model of the three-dimensional isothermal surfaces, and have read out the temperature values. To reconstruct this asymmetric temperature field, interference fringe data were acquired using an eight-directional Twyman-Green interferometer surrounding the object flame, and all data were simultaneously acquired. A ruby laser was used to obtain clear fringe patterns. The temperature distribution was reconstructed from the refractive index distribution, obtained from the fringe patterns, by a computed tomography technique using a convolution reconstruction algorithm. Isothermal profiles were calculated in horizontal cross sections from the temperature data. All of the multiple isotherms in each horizontal section were approximated with polygons and then stacked vertically to form polyhedra in a solid model format, having side facets with the corresponding isothermal values. Models, not only of the initial isothermal solids, but also of the solids resulting from multiple Boolean operations on them, were reconstructed to show the distribution in detail. This development will be of help in studying the local instantaneous structure of turbulent flames.

Method for calibrating system parameters of a multidirectional interferometers system

A multidirectional interferometer system has been proposed and developed to measure the position and orientation of a positioning stage. In this method the system parameters, such as positions of the corner-cube reflectors and directions of the rays in the interferometers, must be determined beforehand. However, it is difficult to find ways to determine the system parameters for each different system with necessary accuracy. This paper proposes a systematic method for calibrating the system parameters when the number of the interferometers is larger than the degrees of freedom of the stage. The method is verified for a two-dimensional stage by both simulation and experiment.

Measurement by multidirectional interferometers of the position and orientation of a positioning stage.

A multidirectional interferometer system is developed to determine the position and orientation of a stage moved in a two-dimensional (2-D) space. In this system four corner-cube prisms are mounted on the moving stage, and four laser beams are incident on the corner cubes in different directions. Moving distances in the observed directions are measured by laser interferometers. The position and orientation of the stage are calculated from the moving distances of the corner cubes. Some experiments are done on the 2-D moving stage with four interferometers, and measurement errors are estimated from redundant data. The estimated accuracy is higher than 0.2 microm for translation and 0.3 x 10(-3) deg for rotation for a measurement range of 0.5 mm and 0.5 deg.