Patent ID: 7082832

Claim:
A recording medium identifying device for identifying the kind of recording medium for an image forming apparatus by applying vibration on the recording medium, comprising: a vibrator for applying vibration on the recording medium, a vibration sensor for detecting, via the recording medium, vibration applied by the vibrator; means for changing a vibrating state between the vibrator and the vibration sensor; and an identifying section for identifying the kind of recording medium based on a detection result of the vibration sensor, wherein the identifying section identifies the recording medium based on a difference between a frequency where a detection signal outputted from the vibration sensor has a maximum value and a frequency where the detection signal has another maximum value, a difference between a frequency where the detection signal has a minimum value and a frequency where the detection signal has another minimum value, or a difference between a frequency where the detection signal has a maximum value and a frequency where the detection signal has a minimum value.