Optical filter and optical device provided with this optical filter

The disclosures of the following priority applications are herein incorporated by reference: Light emitted from a taking lens enters a first birefringent plate to be spatially divided along a first direction extending perpendicular to the direction in which the light advances to achieve two separate rays Land LThe vibrational planes of the two light fluxes Land Lemitted from the first birefringent plate are converted to a circularly polarized light by a phase plate The two light fluxes L′ and L′ emitted from the phase plate are each spatially divided into two by a second birefringent plate along a second direction extending perpendicular to the first direction to achieve four separate rays LLLand Lto be guided to an imaging plane of an imaging device At least either the first birefringent plate or the second birefringent plate is constituted of lithium niobate, rutile, Chilean nitrate, or the like.