A method and apparatus using a duplex printer to print indicia on the back side of a printed page to provide privacy for confidential information appearing on the front side andor indicia to indicate that information which previously appeared on the back side of a printed sheet is not relevant to the information appearing on the front side of the printed sheet. In the present invention, a reflecting cup is used as a collector of the luminous flux of LED. In some embodiments, FPGA implemented down-range and cross-range resampling filters generate fully interpolated data which may be FFT processed as it is generated.