Marker cameras

Qualisys offers a variety of marker cameras for Arqus, Miqus and Oqus systems. For an overview and specifications of the various types and models, see Qualisys camera sensor specifications (marker mode).

The marker cameras calculate the positions and sizes of the detected markers on the camera, which then are sent to the computer over the camera network. This leads to a great reduction of information, which allows the cameras to be connected in a daisy chain. The edges of the markers are detected by using an intensity threshold. The center and size of the markers is calculated in subpixels, a subdivision of each pixel in 64 units per dimension.

The following features are available for Qualisys marker cameras:

• Sensor mode
  Most marker cameras have the possibility to use different sensor modes. For an overview of available sensor modes per camera model, see Qualisys camera sensor specifications (marker mode). The available sensor modes are:

  • High-resolution mode: in high-resolution mode the full resolution of the sensor is used. This is the default sensor mode.

  • High-speed mode: in high-speed mode one fourth of the pixels is used, allowing for increased capture rates at full field of view.

• Marker size filtering
  Size filtering can be used to filter markers that are smaller or larger than a set minimum or maximum threshold.

• Marker masking
  Marker masking can be used to block marker detection at selected areas of the sensor. For more information, see chapter Marker masking.

• Circularity filtering (Oqus only)
  Filtering of markers based on their circularity level. This feature is supported by all Oqus marker cameras. For more information, see chapter Marker circularity filtering (Oqus only).

• Exposure delay
  Exposure delay can be used to improve marker detection in setups with opposing cameras by shifting the exposure of one or more cameras relative to other cameras in the system. For more information, see chapter Delayed exposure to reduce reflections from other cameras.

• Active filtering
  Active filtering can be used to improve marker detection in environments with high background illumination. Active filtering works by capturing each image twice to remove the background light. This significantly increases the ability to capture passive markers in an outdoor environment. Active filtering is supported by all camera types, except the Oqus 3 and 5-series cameras. For more information, see chapter Active filtering for capturing outdoors.

• Marker types
  All marker cameras support the use of different types of markers, namely passive and several types of active markers. For more information, see chapter Choice of markers.

• Video mode
  All marker cameras can be used in video mode. This can be helpful, for example for pointing the cameras when setting up the system. Most cameras have the possibility to stream compressed video images. For an overview, see Qualisys video sensor specifications (in-camera MJPEG).