Abstract

In this work we describe a system based on the reflection of a He-Ne laser beam on the glass surface. This glass level measuring laser system (GLEMLAS) can measure level variations as large as 10 mm with high accuracy. The GLEMLAS uses a 1 mW nonpolarized laser beam and a telescope to obtain the correct beam diameter. The beam is focused down on the CCD array by a 150 mm focal length cylindrical lens. A filter is positioned in front of the CCD array to avoid the blackbody radiation. The gas flow inside the oven produces strong turbulence in the medium density, producing fast variations in the refractive index along the laser beam path. Under these conditions the laser beam moves randomly. The GLEMLAS was tested, and it showed a range of ~10 mm, limited basically by the CCD size, the optical system, and the measuring accuracy. However, even when the glass level reaches the limit of the measuring range, it does not damage the system. Instead, it stops reading and it returns automatically to normal operation after the disturbance. The positioning of the GLEMLAS outside the oven makes the cooling requirement less critical and reduces maintenance costs.

© 1992 Optical Society of America