[Jorge]

Arrrghhh...exactly, you develop for the type of enlarger, all current commercial densitometers are of the diffuse type, they all measure diffuse light. Again, if you want a densitometer that will measure specular light similar to a collimated condenser enlarger you would have to MAKE one.......

Much simpler: use your enlarger and your lab meter, as I have suggested initially.

BTW: these densitometers do exist and are called "micro densitometers", which in this case does not mean that their probe size is very small.

micro densitometers are used in thin film applications and this is a totally differnt field from photography. they cost thousands of dolars and you never see one on the market...they are made specially for people like Dupont, Dow Agfa...etc...