The proton auroral imager (PAI) is an all-sky imager designed to observe the proton aurora. At Syowa Station, two PAIs (PAI-1 and PAI-2) were installed during JARE51 (the 51st Japanese Antarctic Research Expedition) and JARE54. PAI-1 and PAI-2 are equipped with interference filters with different transparent wavelengths (485.0 nm for Hβ and 480.5 nm for Hβ background). Comparison between the Doppler-broadened Hβ emission line (486.1 nm) and the Hβ background level provides information about dynamical morphology of proton aurora. PAI consists of an optical system, a CCD controller and a control PC. The optical system contains a fish eye lens (Fisheye-Nikkor 16mm, F2.8), a dedicated reduced-size optical system manufactured by Nikon, and a digital CCD camera (Hamamatsu C4742-98-26G02). The HiPic8.3.0 software (Hamamatsu) is used for data acquisition. The exposure time and acquisition interval are respectively 7 sec and 15 sec. The acquisition time is set according to the PC's internal clock, which is adjusted to the NTP server placed at Syowa Station.