LARGE-FIELD LASER HOLOGRAPHIC FOCUSING SCHLIEREN SYSTEM

A large-field laser holographic focusing schlieren system for high-spe ed three-dimensional now visualization has been built and evaluated. T his system is based on a recently improved large-field focusing schlie ren technique and is combined with laser holography methods to obtain a three-dimensional recording. A coordinated experimental and computat ional study of supersonic flows over a two-dimensional wedge and a sph ere was conducted to evaluate the capabilities and limitations of the system. Also, the concept of a spread function is introduced to descri be the dependence of the recorded intensity change on the refractive i ndex for focusing schlieren systems. The ability of the system to focu s on planes normal to its optical axis is demonstrated. However, the s harpness of focus of the present system was found to be limited.