Patent ID: 8175832

Claim:
An automatic sensor-calibration method for an automatic sensor-calibration apparatus comprising a sensor input unit, a current level database, and a sensor control unit, the automatic sensor-calibration method comprising: upon entry to an initialization mode after booting, measuring a sensor signal by a sensor input unit and converting the measured sensor signal into a digital value; loading a stored digital value of a previous sensor signal, a currently set maximum digital value for a sensor signal of a light receiving device, a current level of a light emitting device, a minimum slice level, and an absolute slice level; comparing the loaded digital value of the previous sensor signal with the digital value of the sensor signal measured by the sensor input unit, calculating a new slice level if a difference between the loaded digital value of the previous sensor signal and the digital value of the sensor signal measured by the sensor input unit is greater than a preset value, and changing a current slice level to the calculated new slice level; characterized in that, if the changed slice level is lower than the minimum slice level, the method comprises, reducing the current level of the light emitting device to a minimum current level in a series of predetermined current levels for the light emitting device step; newly measuring a sensor signal by the sensor input unit, converting the measured sensor signal into a digital value, calculating a new slice level based on the digital value of the newly measured sensor signal, comparing the calculated new slice level with the absolute slice level, increasing the current level of the light emitting device stepwise in fixed increments until the new slice level calculated based on the digital value of the newly measured sensor signal is lower than the absolute slice level, and changing a current slice level to the new slice level calculated based on the digital value of the newly measured sensor signal when the new slice level is lower than the absolute slice level.