The birefringent filter unit includes a planar birefringent plate arranged such that the light enters the birefringent plate at an approximate Brewster's angle, a first reflecting member arranged substantially parallel to the birefringent plate to allow the light having passed through the birefringent plate to enter the birefringent plate at the approximate Brewster's angle, and a second reflecting member arranged opposite to the first reflecting member and substantially parallel to the birefringent plate, which allows the light having passed through the birefringent plate after being reflected by the first regulating member to enter the birefringent plate at the approximate Brewster's angle.
