Optical characteristics of ruby rods as optical masers are studied by interference of polarized light and with Twyman interferometer. Output patterns are observed with a camera of usual type and a high-speed streak camera of special design. The oscillation patterns are not affected by local deviation of the rod axis and are easily built up in inhomogeneous portions where the streaks are observed by ordinary ray of the crystal and also in portions where the wave front of the light traveling in the axial direction is likely to converge. The near field pattern of a spike is different from that of another even in a oscillation. The oscillation patterns of some spikes are of ring type when input excitation energy exceeds some critical value.