Position detection system, position detection method, image generation unit and image projection apparatus

A position detection system for detecting a position of a movable member, comprising:

• a magnetic field generation unit to generate a magnetic field;
• a magnetic field detection unit to detect a magnetic flux density of the magnetic field effecting the magnetic field detection unit from the magnetic field generation unit, the magnetic flux density of the magnetic field effecting the magnetic field detection unit changeable depending on a change of a position of the magnetic field detection unit relative to a position of the magnetic field generation unit, and to output a detection voltage corresponding to the magnetic flux density of the magnetic field detected by the magnetic field detection unit, the magnetic field detection unit disposed on the movable member;
• and
• circuitry to
• amplify the detection voltage,
• set a reference voltage to be used as a reference for amplifying the detection voltage, and an amplification level of the detection voltage based on at least one of a voltage input to the magnetic field detection unit and a gain value set for the amplification of the detection voltage or both of the voltage input to the magnetic field detection unit and the gain value set for the amplification of the detection voltage, and
• change the reference voltage to switch a region used for detecting the position of the movable member.