The velocity field approach has become very important in the last few years in robot control, since it has many advantages. For instance, it allows to describe a control objective for robot manipulators without providing a function of time. Despite this, on the contrary to usual point-to-point regulation, this method delivers a good transient response. Furthermore, most control algorithms assume that velocity measurements are available for feedback. For this reason, in this article it is shown that a well-known observer for robot manipulators can be used together with a visual servoing approach based on velocity fields. It is assumed that the robot is planar and the camera is fixed, so that the image plane is parallel to the manipulator workspace. Experimental results show the good performance of the complete system.