This paper addresses a depth estimation problem for a robotic system with a single camera. For this problem, several depth observers have been proposed so far. Most of them are based on the Persistency-of-Excitation (PE) condition. But, the PE condition is not always satisfied during a visual servoing task. The estimation of the depth observer stops if the PE condition fails. In our previous work [13], such a case has been illustrated via simulations, and also an estimation recovery method based on periodic IBVS has been proposed. In this paper, we evaluate the effectiveness of our proposed method experimentally. On the basis of experimental results, we discuss how the amplitude and the period of the periodic behavior contribute to recovering estimation.