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The GeV light curve of a pulsar is an important probe to detect accelerationregions in its magnetosphere. Motivated by the recent reports on theobservations of pulsars by {\it Fermi} Large Area Telescope (LAT), we restudythe two-pole caustic model and revise it to investigate the properties of thelight curves in the GeV band. In the revised model, although acceleration gapscan extend from the star surface to the light cylinder along near the last openfield lines, the extension of the gaps along the azimuthal direction is limitedbecause of photon-photon pair production process. In such gaps, high-energyphotons are emitted uniformly and tangentially to the field lines but cannot beefficiently produced along these field lines where the distances to the nullcharge surface are larger than $\sim0.9$ times of the distance of the lightcylinder, and the effective azimuth extension of the gaps is about $230^\circ$.The model is applied to the four pulsars Vela, PSR J1028-5819, PSR J0205+6449,and PSR J2021+3651 whose light curves obtained with {\it Fermi} have beenrecently released. The model is successful in reproducing the general featureof the light curves for the four pulsars, and the radial distances of the radiopulse for the four pulsars are estimated.

A Revisit of the Two-Pole Caustic Model for GeV Light Curves of Gamma-Ray Pulsars