Optical sensor, paper sheet identification device, paper sheet processing device, and light detection method

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):
• A
• =
• [
• A
• 11
• …
• A
• 1
• ⁢
• n
• ⋮
• ⋱
• ⋮
• A
• (
• n
• -
• 1
• )
• ⁢
• 1
• …
• A
• (
• n
• -
• 1
• )
• ⁢
• n
• ∑
• i
• =
• 1
• n
• -
• 1
• A
• i
• ⁢
• 1
• …
• ∑
• i
• =
• 1
• n
• -
• 1
• A
• i
• ⁢
• n
• ]
• 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.