A radiation detector (9, 1109, 1219, 1229), comprising: a first scintillator (91, 92a) having a first emission peak wavelength; a second scintillator (93, 92b) positioned on the first scintillator (91, 92a), the second scintillator (93, 92b) having a second emission peak wavelength different from the first emission peak wavelength; and a plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000), the first scintillator (91, 92a) positioned over and contacting each of the plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000), the plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000) including first detectors (202, 402, 502, 602, 702, 802, 902, 1002) and second detectors (204, 404, 504, 604, 704, 804, 904, 1004), where the second detectors (204, 404, 504, 604, 704, 804, 904, 1004) differ from the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) in doping profile, pn junction depth, or front-versus-backside illumination geometry, the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) being more sensitive to the first emission peak wavelength than the second emission peak wavelength, the second detectors (204, 404, 504, 604, 704, 804, 904, 1004) being more sensitive to the second emission peak wavelength than are the first detectors (202, 402, 502, 602, 702, 802, 902, 1002), wherein the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) and second detectors (204, 404, 504, 604, 704, 804, 904, 1004) are arranged in a two-dimensional array for measuring 2D coordinates of impinging photons, wherein the 2D array has a plurality of sides, each of the plurality of sides has a border row or a border column adjacent thereto, and each border row and each border column has at least one first detector (202, 402, 502, 602, 702, 802, 902, 1002) and at least one second detector (204, 404, 504, 604, 704, 804, 904, 1004), characterized in that each border row and each border column has at least one third detector (808, 1008), each third detector (808, 1008) is sensitive to photons in a wavelength band including the first emission peak wavelength and the second emission peak wavelength. a first scintillator (91, 92a) having a first emission peak wavelength; a second scintillator (93, 92b) positioned on the first scintillator (91, 92a), the second scintillator (93, 92b) having a second emission peak wavelength different from the first emission peak wavelength; and a plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000), the first scintillator (91, 92a) positioned over and contacting each of the plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000), the plurality of photon detectors (200, 400, 500, 600, 700, 800, 900, 1000) including first detectors (202, 402, 502, 602, 702, 802, 902, 1002) and second detectors (204, 404, 504, 604, 704, 804, 904, 1004), where the second detectors (204, 404, 504, 604, 704, 804, 904, 1004) differ from the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) in doping profile, pn junction depth, or front-versus-backside illumination geometry, the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) being more sensitive to the first emission peak wavelength than the second emission peak wavelength, the second detectors (204, 404, 504, 604, 704, 804, 904, 1004) being more sensitive to the second emission peak wavelength than are the first detectors (202, 402, 502, 602, 702, 802, 902, 1002), wherein the first detectors (202, 402, 502, 602, 702, 802, 902, 1002) and second detectors (204, 404, 504, 604, 704, 804, 904, 1004) are arranged in a two-dimensional array for measuring 2D coordinates of impinging photons, wherein the 2D array has a plurality of sides, each of the plurality of sides has a border row or a border column adjacent thereto, and each border row and each border column has at least one first detector (202, 402, 502, 602, 702, 802, 902, 1002) and at least one second detector (204, 404, 504, 604, 704, 804, 904, 1004), characterized in that each border row and each border column has at least one third detector (808, 1008), each third detector (808, 1008) is sensitive to photons in a wavelength band including the first emission peak wavelength and the second emission peak wavelength.