A spectral filter (1100; 1200; 1300) comprising: a first unit filter (111; 211) having a first center wavelength in a first wavelength range; and a second unit filter (121; 221) having a second center wavelength in a second wavelength range, wherein the first unit filter (111; 211) comprises: two first metal reflective layers (131, 132) provided spaced apart from each other and comprising a first metal; and a first cavity provided between the two first metal reflective layers (131, 132), and wherein the second unit filter (121; 221) comprises: two second metal reflective layers (151, 152) provided spaced apart from each other and comprising a second metal different from the first metal; and a second cavity provided between the two second metal reflective layers (151, 152), wherein the first unit filter (111; 211) and the second unit filter (121; 221) are provided in one dimension or two dimensions on a plane; the spectral filter (1100; 1200; 1300) characterized in that the first unit filter (111; 211) is included in a first filter array (110; 210; 310) comprising a plurality of first unit filters (111-113; 211-213; 315) having different center wavelengths in the first wavelength range, and the second unit filter (121; 221) is included in a second filter array (120; 220; 320) comprising a plurality of second unit filters (121-123; 221-223; 325) having different center wavelengths in the second wavelength range, wherein each of the first unit filters (111-113; 211-213; 315) included in the first filter array (110; 210; 310) and each of the second unit filters (121-123; 221-223; 325) included in the second filter array (120; 220; 320) comprises a cavity (141-143, 161-161; 145, 165) and the cavities (141-143, 161-161; 145, 165) having different thicknesses or effective indexes, in particular, the thickness or the effective index of the cavities (141-143, 161-161; 145, 165) with respect to each of the first filter array (110; 210; 310) and the second filter array (120; 220; 320) is subsequently increased. a first unit filter (111; 211) having a first center wavelength in a first wavelength range; and a second unit filter (121; 221) having a second center wavelength in a second wavelength range, wherein the first unit filter (111; 211) comprises: two first metal reflective layers (131, 132) provided spaced apart from each other and comprising a first metal; and a first cavity provided between the two first metal reflective layers (131, 132), and two first metal reflective layers (131, 132) provided spaced apart from each other and comprising a first metal; and a first cavity provided between the two first metal reflective layers (131, 132), and wherein the second unit filter (121; 221) comprises: two second metal reflective layers (151, 152) provided spaced apart from each other and comprising a second metal different from the first metal; and a second cavity provided between the two second metal reflective layers (151, 152), two second metal reflective layers (151, 152) provided spaced apart from each other and comprising a second metal different from the first metal; and a second cavity provided between the two second metal reflective layers (151, 152), wherein the first unit filter (111; 211) and the second unit filter (121; 221) are provided in one dimension or two dimensions on a plane; the spectral filter (1100; 1200; 1300) characterized in that the first unit filter (111; 211) is included in a first filter array (110; 210; 310) comprising a plurality of first unit filters (111-113; 211-213; 315) having different center wavelengths in the first wavelength range, and the second unit filter (121; 221) is included in a second filter array (120; 220; 320) comprising a plurality of second unit filters (121-123; 221-223; 325) having different center wavelengths in the second wavelength range, wherein each of the first unit filters (111-113; 211-213; 315) included in the first filter array (110; 210; 310) and each of the second unit filters (121-123; 221-223; 325) included in the second filter array (120; 220; 320) comprises a cavity (141-143, 161-161; 145, 165) and the cavities (141-143, 161-161; 145, 165) having different thicknesses or effective indexes, in particular, the thickness or the effective index of the cavities (141-143, 161-161; 145, 165) with respect to each of the first filter array (110; 210; 310) and the second filter array (120; 220; 320) is subsequently increased.