A method and apparatus for real-time polarization difference imaging video including an imaging lens focusing the light on to a collimating lens, whereby the stimulus beams becomes parallel before striking a polarizing beam-splitter. In some implementations, calibrated magnetometer data for a magnetometer of a mobile device is retrieved from a calibration database and validated by data from another positioning system, such as course or heading data provided by a satellite-based positioning system. A cleaner housing has wall members defining a housing space, a first one of which is formed with a first ventilation hole. 0 \u03bcm, and includes toner particles having a particle diameter not greater than 5 \u03bcm in an amount of from 60 to 90% by quantity.