  Weyl points in three-dimensional photonic crystals behave as monopoles of
Berry flux in momentum space. Here, based on general symmetry analysis, we show
that a minimal number of four symmetry-related (consequently equifrequency)
Weyl points can be realized in time-reversal invariant photonic crystals. We
further propose an experimentally-feasible way to modify double-gyroid photonic
crystals to realize four equifrequency Weyl points, which is explicitly
confirmed by our first-principle photonic band-structure calculations.
Remarkably, photonic crystals with equifrequency Weyl points are qualitatively
advantageous in applications including angular selectivity, frequency
selectivity, invisibility cloaking, and three dimensional imaging.
