Patent ID: 7699311

Claim:
A sheet discriminating apparatus comprising: a pair of conveying rotary members for conveying a sheet while rotating with the sheet sandwiched between the pair of conveying rotary members; a vibration detecting sensor for detecting vibrations of one conveying rotary member of the pair of conveying rotary members; and a discriminating portion for discriminating a thickness of the sheet based on the vibrations detected by the vibration detecting sensor, wherein the discriminating portion discriminates the thickness of the sheet based on vibrations of the one conveying rotary member which are detected by the vibration detecting sensor when a rear end of the sheet passes through the pair of conveying rotary members, wherein the discriminating portion discriminates the thickness of the sheet based on a peak value of the vibrations when the rear end of the sheet passes through the pair of conveying rotary members, and wherein the discriminating portion discriminates the thickness of the sheet based on a difference of the peak value of the vibrations when the rear end of the sheet passes through the pair of conveying rotary members and a mean value of the vibrations after the sheet has passed through the pair of conveying rotary members.