From IGSTK

Contents 1 Features not yet implemented 1.1 Support for multi-cameras 1.2 Miscellaneous Extensions to MicronTracker support in IGSTK 1.2.1 Augmented reality 1.2.2 Video feedback 2 MicronTracker Parameters

Features not yet implemented

Additional MicronTracker functionalities/features not currently implemented in the MicronTracker class.

1. Process markers that were recognized by the algorithm but not matched with marker template types specified during initialization.
2. Collect new samples to recognize unidentified facets
3. Create new markers template type
4. processing facets partially identified
5. Use of multiple cameras
   1. processing markers
   2. registering camera coordinates

Support for multi-cameras

In multi-camera setup, there are 4 types of situations

1. Marker is identified by a given camera
2. Marker is identifed by another camera, reigstered to the given camera
3. Marker is identied by another camera, not registeredd to the given camera
4. Mark is not identied by any camera

Camera to camera registration can be setup

1. Cameras_Camera2CameraOXfSet() method
2. Using markers identifed by both cameras ( update the registration) Markers_AutoAdjustCam2CamRegistrationGet

Miscellaneous Extensions to MicronTracker support in IGSTK

Augmented reality

Micron Tracker video images can be augmented using surgical tool information as follows

Overlaying surgical tool representation on top of the MicronTracker video images. The surgical tools can be represented using axis spatial objects and their position and orientation will be set using tracking data from the MicronTracker

Video feedback

The left and right images of the MicronTracker camera can be grabbed and set to image spatial objects.

MicronTracker Parameters

This parameters can be specified using the initialization file.

1. Exposure level ( ratio between light intensities reaching the camera and the corresponding pixel values. It is the product of the GainF and ShutterMsecs properties )
2. Gain and Shutter time:
   1. Gain ( GainDB ): determines the amount of amplification the analog signal from the sensor undergoes before being converted to digital pixel values. ( A gain factor of 1, which is the lowest setting, no magnifications. Higher gain factors result in an increase in brightness, but also increase in pixel noise which proportionally affects measurement noise, i.e jitter
   2. Shutter time : duration in which the shutter remains open at each frame. This parameter determines the amount of light energy collected by the sensor from a given scene. The longer the duration, the stronger the light signal and thus the lower image noise and measurement jitter. Longer shutter , however, increase the likelihood of blurring during motion. Hence, longer shutter time is not appropriate for a marker with fast motion.
3. Autoexposure: The camera's exposure level is automatically adjusted following frame grabs to maintain the average image brightness near a constant mid-grey level, ignoring other exposure properties. Option to turn on/off this functionality.
4. Light coolness property: The spectrum of the illumination reflected off an XPoint affects the way the camera lens focuses the XPoint image on the sensor, and therefre, affects the measurement of the position. The light coolness property provides an indication to the camera of how the illumination spectrum is distributed, allowing it to correct for the difference between the calibration light spectrum and the measurement light spectrum. The property value ranges from -0.5 to 1.5. A value of 0( "warm" ) represents coolness of filament-type light source, such as incandescent and halogen. These light sources emit a large amount of light in the red and infra-red range and relatively small amount in the blue end of the spectrum. A value of 1("cool") corresponds to the spectrum of "daylight" flourescent light sources.
   1. Use of a special color sequence (CoolCard ) marker to adjust automatically the light coolness property
5. Marker identification algorithm parameters:
   1. Template Match tolerance: sensitivity of the deviation between the measured relative positions of XPoints and their relative positions as described in the facet templates.
   2. Predictive Frame Interleave property: In predictive-only frames, the algorithm will search only for markers that have been identified in the previous frame, at a location predicated from their past position and motion history. In full matching frames, the algorithm will search the full field of measurement for a match to all markers. Full matching requires more computing resources than predictive. Property value 0 means full-matching. A value of 3 means. 3 out of every 4 frames would be predictive-only.
   3. Number of extrapolated frames: controls the number of future frames for which the markers, which have been identified in the current frame are remembered.
   4. Jitter filter: This filter is applied to reduce measurement noise by averaging subsequent measurements when markers and the camera are motionless with respect to each other.
   5. Over exposure control property: exposure is lowered ( some scenes might be overexposed: washed out ) if the algorithm discovers that there are over-exposed regions in the image. The exposure is reduced to the lowest possible without losing detection of vectors. This property specifies the number of frames interval this operation will be performed.