Utilizing a visible light filter to reduce visibility of fiducial images

A head mounted display (HMD) device comprising:

• a projection system comprising a left display image projector and a right display image projector;
• a left eye display optical path configured to transmit left eye images from the projection system for viewing and a right eye display optical path configured to transmit right eye images from the projection system for viewing;
• a display alignment tracker (DAT) system comprising,
• a DAT optical path comprising a left side DAT optical path and a right side DAT optical path,
• a camera optically coupled to an output of the DAT optical path, and
• a visible light filter located along the DAT optical path;
• and
• a controller configured to control the projection system to output a fiducial image comprising a color of light transmitted by the visible light filter.

A head mounted display (HMD) device comprising:

• a projection system comprising a left display image projector and a right display image projector;
• a left eye display optical path configured to transmit left eye images from the projection system for viewing and a right eye display optical path configured to transmit right eye images from the projection system for viewing;
• a display alignment tracker (DAT) system comprising,
• a DAT optical path comprising a left side DAT optical path and a right side DAT optical path,
• a camera, and
• a mirror device located along the DAT optical path and operable to selectively deliver light from the left side DAT optical path or the right side DAT optical path to the camera;
• and
• a controller configured to control a state of the mirror device.