Abstract: An image forming apparatus includes a storage to store recording media, a smoothness detector to detect smoothness of the recording media, a memory unit to store smoothness values detected by the smoothness detector, a transfer device to transfer a toner image onto the recording media, a fixing device to fix the toner image onto the recording media, a temperature controller to determine a target fixing temperature for a second and subsequent recording media based on a predicted value calculated from the smoothness values, and a processor to reset the smoothness values in response to detection of an external factor that causes the smoothness detector to provide a smoothness value out of a predetermined range of the predicted value during an image forming operation from when the processor receives a sheet-feeding permission signal of one of the recording media stored in the storage until the recording medium is ejected.

Abstract: An optical sensor includes a light-emitting unit to emit light onto a measuring object, a regular reflection light receiver to receive regular reflection light from the measuring object out of the light emitted by the light-emitting unit, and a diffuse reflection light receiver to receive diffuse reflection light from the measuring object out of the light emitted by the light-emitting unit. An angle of incidence of the light emitted onto a surface of the measuring object is not smaller than 75° and not larger than 85°. The diffuse reflection light receiver receives, out of the diffuse reflection light from the measuring object, diffuse reflection light having an angle of reflection with respect to a perpendicular to the surface of the measuring object larger than 0° and smaller than an angle of reflection of the regular reflection light with respect to the perpendicular to the surface of the measuring object.

Abstract: An image forming apparatus includes paper trays to contain and feed a recording sheet on which a toner image is transferred; status sensors to detect a storage status of the recording sheet contained in the paper trays; a sheet sensor to detect a smoothness of the recording sheet; a memory to store detection values of the smoothness detected by the sheet sensor; a fixing device to heat and press the toner image transferred onto the recording sheet and fix it onto the recording sheet; and a control circuit to determine a target fixing temperature of the fixing device based on the detection values stored in the memory. The control circuit determines the target fixing temperature for successive recording sheets depending on the detected smoothness, and resets the detection values stored in the memory to zero when the status sensors detect a change in the storage status of the paper trays.