Different objectives are considered in the paper as candidates for the receiving antennas of a lidar. Those are lenses (three types), mirrors (two types), combination of a mirror and a lens (three types), and multicomponent objectives of two types. The comparison is being done using some generalized quality criteria. The technique proposed for making a comparison together with power and size diagrams allow one to select an optimal objective according to the coefficient of relative efficiency introduced or aiming at minimum length (at the same clear aperture). It is shown that the most compact objectives are those constructed following the Mangene scheme, the Fresnel lenses, and the multicomponent ones (in the order of increasing size).