| CPC G07D 7/12 (2013.01) [G01N 21/27 (2013.01); G01N 21/645 (2013.01); G06V 10/56 (2022.01)] | 8 Claims | 

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               1. An optical sensor that detects light from a sheet on which is printed at least one type of single-color ink among first to n-th n types of single-color inks that emit lights having wavelength bands different from one another, wherein n is an integer of 3 or greater, the optical sensor comprising: 
              a light source; 
                a light receiver including first to (n-1)th light-receiving elements respectively capable of selectively receiving lights emitted from the first to (n-1)th single-color inks among the first to n-th single-color inks and capable of receiving light emitted from the n-th single-color ink; 
                a memory configured to store a correction value based on reference data obtained by receiving lights emitted from the first to n-th single-color inks individually in the light receiver by type of single-color inks; and 
                a controller configured to correct detection data with the correction value, the detection data obtained by receiving, in the light receiver, light emitted from a sheet irradiated with light from the light source, wherein 
                the correction value is based on a matrix A with n rows and n columns represented by the following Formula (1): 
              ![]() where a matrix element Axy is an output value of an x-th light-receiving element when light emitted from a y-th single-color ink among the first to n-th single-color inks is received alone in the light receiver, x is an integer of 1 or greater and (n−1) or smaller, and y is an integer of 1 or greater and n or smaller. 
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