| CPC G01S 17/04 (2020.01) [G01J 1/0228 (2013.01); G01J 1/4228 (2013.01); G01S 7/4863 (2013.01)] | 7 Claims |

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1. A light detection sensor for use in a sheet processing apparatus that performs a sheet recognition processing, the light detection sensor comprising:
a light source configured to radiate light to a detection object attached to a sheet; and
a light receiver comprising a plurality of detectors configured to detect intensity of light from the detection object, wherein
the plurality of detectors comprises a first detector configured to detect intensity of light of a first wavelength band, and a second detector configured to detect intensity of light of a second wavelength band different from the first wavelength band,
a first sensitivity of the first detector to the light of the first wavelength band is lower than a second sensitivity of the second detector to the light of the second wavelength band,
a first light receiving area of the first detector is larger in size than a second light receiving area of the second detector,
sizes of the first light receiving area and the second light receiving area are adjusted to correct a variation in sensitivities of the first and second detectors and to compensate for the first sensitivity being lower than the second sensitivity, and
a size of the first light receiving area of the first detector is set in accordance with an emission intensity of the light radiated by the detection target, and a distance between the light detection sensor and the detection object.
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