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FAQ: EyeLink II: What does the message "Extra Markers" mean?
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* This FAQ only applies to the EyeLink II systems *

The error message "Extra Markers" means the headband's marker camera is detecting more infrared (IR) light sources than it expects. The EyeLink II system relies on its own specific IR markers to calculate the headset's position and distance, and it was not designed to work in conjunction with other IR-emitting devices.

This error is almost always caused by an external IR source or by improper positioning of the eye cameras themselves.
  • Remove External IR Sources
    First, identify and remove any other devices that emit infrared light from the marker camera's field of view. Common sources include:
    • Sunlight from a window.
    • Other motion capture or tracking systems.
    • Remote controls.
  • Check Eye Camera Positioning
    If there are no external IR sources, the error may be caused by the marker camera seeing the IR illuminators from the two eye cameras.

    Ensure the eye cameras are positioned correctly, as outlined in Section 3.4 of the EyeLink II User Manual. Proper positioning will prevent the illuminators from being visible to the marker camera.
If you’re unsure of the source of these reflections, please email support@sr-research.com with screenshots of the EyeLink Host PC (see How can I take a screenshot on the Host PC monitor? for how to take and retrieve the images), along with the photos of the physical experimental setup so that we can attempt to help to locate the source of the interference.