An authenticating system includes an authenticating device, a background display device, a sensing device, and an authentication pattern checking device. The authenticating device displays a first display pattern on a transparent display panel including a transmissivity pattern. The transmissivity pattern includes a plurality of regions with different transmissivities. The background display device displays a second display pattern on a display panel to overlap the transparent display panel. The sensing device generates a sensing pattern by sensing an authentication pattern generated based on the transmissivity pattern, the first display pattern, and the second display pattern. The authentication pattern checking device performs authentication by checking whether the sensing pattern is consistent with an authentication reference pattern.