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Radiation emitted near a black hole reaches the observer by multiple paths;and when this radiation varies in time, the time-delays between the variouspaths generate a "blinking" effect in the observed light curve L(t) or itsauto-correlation function xi(T)= <L(t)L(t-T)>. For the particularly important"face-on" configuration (in which the hole is viewed roughly along its spinaxis, while the emission comes roughly from its equatorial plane -- e.g. fromthe inner edge of its accretion disk, or from the violent flash of anearby/infalling star) we calculate the blinking in detail by computing thetime delay Delta t_{j}(r,a) and magnification mu_{j}(r,a) of the jth path(j=1,2,3,...), relative to the primary path (j=0), as a function of theemission radius r and black hole spin 0<a/M<1. The particular geometry andsymmetry of the nearly-face-on configuration enhances and "protects" theblinking signal, making it more detectable and more independent of certainastrophysical and observational details. The effect can be surprisingly strong:e.g. for radiation from the innermost stable circular orbit ("ISCO") of a blackhole of critical spin (a_{crit}/M = 0.853), the j=1,2,3 fluxes are,respectively, 27%, 2% and 0.1% of the j=0 flux.

Light Loop Echoes and Blinking Black Holes