PROBLEM TO BE SOLVED: To achieve a reflection-type optical sensor which detects at least one of toner pattern position and toner density.;SOLUTION: The reflection-type optical sensor has: an integral type light emitting/receiving element in which a semiconductor light emitting element Ei and a photodiode Di are made close to each other and arranged integrally so that the light emitting axis of the semiconductor light emitting element and the light receiving axis of the photodiode are in parallel and have an interval L; and an illuminating light condensing lens LEi which converges a light flux emitted from the semiconductor light emitting element onto the surface of a carrying medium 2040. The illuminating light condensing lens shifts the optical axis to the photodiode in parallel with the light emitting axis. The positional relations among the semiconductor light emitting element, the photodiode, and the illuminating light condensing lens are adjusted so that the light beam emitted from the semiconductor light emitting element onto the light emitting axis is refracted by the illuminating light condensing lens, enters obliquely the surface of the carrying medium orthogonal to the light emitting axis with an angle of incidence Θ, is regularly reflected by the surface of the carrying medium, and enters the center of the light receiving part of the photodiode, wherein the interval L is smaller than about 1 mm, and the angle of incidence Θ is smaller than 10 degrees.;COPYRIGHT: (C)2011,JPO&INPIT
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