The effect of laser beam attenuation on nitric oxide measurements in a diesel engine is presented. A number ofexperimental ways to correct for this attenuation are discussed: transmission measurements, bidirectional laserinducedfluorescence, and Raman scattering by N2. Comparison of the results indicates that the attenuation isgenerally not uniform over the cylinder. Instead it seems to be less severe over the field of view (i.e. the upper partof the cylinder)
