OPTICAL MEASUREMENT METHOD, OPTICAL MEASURING APPARATUS, OPTICAL MEASURING SYSTEM, AND IMAGE-FORMING APPARATUS

摘要

PROBLEM TO BE SOLVED: To obtain an optical measuring apparatus which can measure with an optimum accuracy necessary for image control. SOLUTION: The optical measuring apparatus 10 is constituted of a light source 12 for projecting light in a reflection area, namely, an irradiation area Ar of a predetermined size set on a paper face P, a lens 14 for condensing a reflecting light from the irradiation area Ar, and a photoelectric transducing element 18 set to a rear focal plane PL3 of the lens 14. A light reception area of the photoelectric transducing element 18 is included in the rear focal plane PL3, having a specific size for receiving part of the light passing the lens 14. Moreover, an effective detection area of the photoelectric transducing element is made variable. A signal-processing part 20 and a driving part 22 are connected to the photoelectric transducing element 18. The driving part sets the effective light reception area (light reception size) of the photoelectric transducing element 18 to a predetermined size.