| Autor: |
Gabriel Usera, German Da Costa, Rafael Guarga, Jose Cataldo, Felix Mosqueda, Arturo Lezama |
| Rok vydání: |
1999 |
| Předmět: |
|
| Zdroj: |
SPIE Proceedings. |
| ISSN: |
0277-786X |
| DOI: |
10.1117/12.370254 |
| Popis: |
A light beam StrUCtUred as a hollow cone is obtained by oblique illumination of a cylindrical surface with a laser beam. Thecylindrical surface may be a metallic needle or the core of an oiical fiber. In the first case a speckle pattern appears aroundthe light cone. The direction and mean length of light speckles are studied in the text. In the second case the light intensitydistribution around the light cone presents bright and dark regions resulting from interference between light rays reflectedfrom and pissing through the fiber core. The hollow light cone is transformed into a hollow light cylinder (HLC) by means of a lens whose focus coincides with the cone vertex. The HLC is used to explore the cylindrical layer placed in the neighborhood of the internal wall of a combustion chamber model. Due to the large diameter of the model a Fresnel lens isused to transform the light cone into a light cylinder. This introduces additional optical noise in the system. The HLC iscollected again by another Fresnel lens at the model output. A photodetector placed at the focus of the collected beamproduces an electrical outpit showing pulses whenever residual particles xiss through the explored region. A quantitativeexperimental analysis of the performance of the combustion chamber is thus performed.Keywords: light cone. light cylinder, swirl flow. combustion chamber1. INTRODUCTIONProperties of light cones obtained by oblique illumination of an oical fiber are studied in refs.(1.2). The light intensitydistribution around the light cone presents bright and dark regions due to interference between light rays reflected at thefiber surface and light rays passing through the fiber. A light cone is also Obtained by oblique illumination of a cylindricmetallic needle with a laser beam. In that case the surface is opaque so there are no transmitted light rays. Therefore.periodic maxima and minima of light intensity are not present in the scauered light cone. But the light intensity distributionhas the siructure of a speckle paftem if the metallic needle surface is not perfectly smooth. In a preceding xiper the shapeand dimensions of speckles obtained by normal illumination of a rough metallic cylinder were studied. In the present per(Section 2) the study is extended to cover the case of an arbitrary angle between the cylinder and the laser beam. which isuseful in any application related to Speckle Metrology . |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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