Abstract: A laser diode is disclosed which utilizes a feedback system which substantially reduces the dependency of the optical output power of the laser diode on laser junction temperature which is dependent on the pixel pattern. The feedback system of this invention generates a feedback signal through comparison of an averaged train of pixel information against an averaged optical output power from the back photodiode of the laser diode. By comparing the two averaged signals, one can determine the fluctuations of the heat in the laser diode. At any given point, any discrepancy between the two averaged signals shows a temperature change in the laser diode. Depending on the amount of the difference between the two signals, the degree of excess temperature can be determined and the difference will be used for feedback correction.

Abstract: A circuit used in laser scanners which allows the continuous calibration of a laser so that the output power of the laser is accurately modulated by the input video signal regardless of temperature changes or aging effects of the laser. The video signal includes a test segment which has two steps. The light output of the laser is measured during both steps. The lower step measurement is compared to a reference and the error is used to adjust the bias current of the laser. The difference between the upper step measurement and the lower step measurement is compared to a second reference and the error is used to adjust the gain of the video signal so that the variation in laser power maximum and minimum remains calibrated.