Dear,Thanks a lot for your help.

You were right, arduino use TTL signal (5v) ... sorry for the annoyance.
So we have bought a new camera TTL 3.3v with a TTL3.35v converter.

Now it works but we are only able to take one snapshot, after that the camera is most of the time unable to resync, we need to power it down before take a new snapshot.

Have you got this problem yet ?

regards,