An original application of the Laser-Induced-Incandescence (LII) technique was set up to quantify soot particles inside the combustion chamber of an optically accessible Direct-Injection Diesel engine. Planar soot concentration and local particle diameter were measured for several Exhaust Gas Recirculation (EGR) rates. The impact of the injection timing on the soot evolution for the highest EGR rate was also studied. Based on the analysis of LII images it is shown that the planar distribution of soot becomes more and more uniform across the combustion chamber and globally the soot maximum more important with the EGR rates increase. High EGR rates, combined with a retarded start of injection may lead to lower soot production inside the combustion chamber. Comparison between exhaust and in-cylinder soot concentration highlights the effect of post-combustion oxidation on the particle-emissions amount.