Patent ID: 7382992

Claim:
An image forming apparatus having a sheet identification function, for forming an image in an image forming condition according to an identification result of a conveyed sheet by the sheet identification function, comprising: a conveying part adapted to convey a sheet; a sensor adapted to bring a probe having a built-in piezoelectric element into contact with a surface of a sheet conveyed by said conveying part, and thereby to generate electric detection signals corresponding to irregularities of the surface of the sheet; an identification part adapted to identify a material type of the sheet conveyed by said conveying part, based on detection signals outputted from said sensor; a correct part adapted to correct variations of detection features of said sensor based on detection output of said sensor at a time when said sensor detects a calibration sheet conveyed by said conveying part, the calibration sheet having a predetermined surface roughness; a count part adapted to count an accumulative number of sheets on which a material type of the sheet is identified by said identification part; and a notification part adapted to notify a user to feed the calibration sheet according to what the number of identifying sheets on which images are formed in said image forming apparatus reaches a predetermined number.