Patent ID: 8291001

Claim:
A method for identifying a type of recording medium using a time-varying output signal from a photosensor, the time-varying output signal being obtained by sensing an output of the photosensor as a function of time while the recording medium is being moved with respect to the photosensor, the method comprising: amplifying the time-varying output signal of the photosensor; converting the amplified time-varying output signal of the photosensor to digitized data points using an analog to digital converter thereby creating a first set of digitized data; applying a digital filtering operation to the first set of digitized data to provide a low pass data set that includes low temporal frequencies; applying a digital filtering operation to the first set of digitized data to provide a high pass data set that includes high temporal frequencies, the high temporal frequencies being higher than the low temporal frequencies; computing the standard deviation of the low pass data set; computing the standard deviation of the high pass data set; and identifying the recording medium type using values from both the standard deviation of the low pass data set and the standard deviation of the high pass data set.