Patent ID: 8867937

Claim:
A diffuse reflection output conversion method, comprising detecting, via an apparatus, a plurality of gradation patterns that are formed sequentially on a surface to be detected and each of which is formed with a different amount of attached powder; using an optical detector arranged at a position facing the surface to be detected, the optical detector including a light emitter and a light receiver, and being configured to detect a specular reflection and diffuse reflections simultaneously, wherein in a relation between a specular reflection output obtained from the gradation patterns and an amount of attached powder, a specular reflection component is a component, in a detected specular reflection output, resulting from a light output from the light emitter and specularly reflected on the surface to be detected, a region before specular reflection saturation is a region where the specular reflection component decreases and saturates at a minimum level, a region after specular reflection saturation is a region where the specular reflection component, in the detected specular reflection output, saturates at the minimum level and remains constant despite an increase in the amount of powder attached on the gradation patterns, and a diffuse reflection detector is calibrated by: obtaining a diffuse reflection output resulting from an amount of attached powder at a border between the region before specular reflection saturation and the region after specular reflection saturation, calculating a ratio between the diffuse reflection output and a reference diffuse reflection output calculated in advance as a calibration coefficient, and multiplying a diffuse reflection output obtained from the gradation patterns by the calibration coefficient calculated at the calculating.