A method for calibrating an imaging apparatus configured for scanning a document, the imaging apparatus including a scanner head having an illuminant and a sensor, and a phosphorescent material forming a phosphorescent area located opposite the scanner head, the method including at least one of performing an ambient light calibration based on a background light emission intensity level of the phosphorescent area; performing an ambient light time calibration based on a decay constant of the phosphorescent material; performing a horizontal calibration to compensate for irregularities in at least one of the illuminant and the sensor across a width of the phosphorescent area; and performing a vertical calibration to compensate for changes of scanning speed of the scanner head in a lengthwise scanning direction along a length of the phosphorescent area.