US Patent 6918688 Vehicle headlamp apparatus

A vehicle headlamp device contains a rotation-state recognizing circuit operating such that when any of Hall elements used for controlling a rotational position of a drive motor for deflecting the optical axes in a headlamp device is abnormal, a rotation-state recognizing circuit recognizes a rotational position of the drive motor based on the output signals of the remaining Hall elements and a predetermined angle prediction time computed using a rotational period of the drive motor. With provision of the rotation-state recognizing circuit, even when any of the Hall elements becomes defective, the rotation of the drive motor is normally controlled to thereby secure a proper optical-axis deflection control in the headlamp device.