when producing an object by subsequent solidification of material layers 1 at places corresponding to the object there is a problem of limited production speed because the scanning speed or laser power of the light beam scanning the material layer 1 cannot be increased at will , if the light beam 4 used for solidification is focused as required for exact resolution . according to the invention this problem is solved by providing a variable focusing device 8 in the light beam 4 , whereby the focus of the light beam 4 can be varied during the solidification of the layer 1 . thus , a different focus , laser power and scanning speed can be used in different regions of the layer 1 .