Optical filter and optical device provided with this optical filter

Light emitted from a taking lens 20 enters a first birefringent plate 1 a to be spatially divided along a first direction extending perpendicular to the direction in which the light advances to achieve two separate rays L 10 and L 20 . The vibrational planes of the two light fluxes L 10 and L 20 emitted from the first birefringent plate 1 a are converted to a circularly polarized light by a phase plate 1 c. The two light fluxes L 10 ' and L 20 ' emitted from the phase plate 1 c are each spatially divided into two by a second birefringent plate 1 d along a second direction extending perpendicular to the first direction to achieve four separate rays L 11 , L 12 , L 21 and L 22 , to be guided to an imaging plane 15 a of an imaging device 15 . At least either the first birefringent plate or the second birefringent plate is constituted of lithium niobate, rutilo, Chilean nitrate, or the like.