Twin System

The settings on the Twin System page are used to enable and control the Twin system feature. This feature enables a Twin master system to control a Twin slave system on another computer. It can for example be used to combine an underwater system with one above water. For more information about the Twin system feature, see chapter Twin systems.

To enable the Twin master functionality select the Enable Twin Master option on the system that you want to use as Twin master. The Twin System settings are then used to control the Twin slave computer and the merging of data.

You do not need to change any settings related to Twin systems on the Twin slave system.

To enable the automatic transfer of the Twin slave file you must select the Merge with Twin Slave option on the Processing page.

The two systems must also be calibrated with a twin calibration, for information about the settings see chapter Twin System Calibration.

Twin Slave System

The Twin Slave System settings controls which slave is controlled by the Twin master system.

Use the Find Slaves button for QTM to search for any available QTM programs on other computers. QTM must be running on the other computer and connect via Ethernet (directly or via the LAN) to the Twin master computer. Only computers with a located camera system will show up in the list. Select the computer that will be the Twin slave from the list below the Address setting.

It is possible to enter an address manually in the Address setting if the Find Slaves option fails. The Port and the Password setting only needs to be changed if they have been modified in QTM of the Twin slave system.

Capture Frequency

The Capture Frequency settings control the frequency and synchronization of the Twin master and slave systems. The settings that are set for the two systems will override any other settings on the two systems. However, the timing settings will not change until you start a new measurement on the Twin master with New on the File menu. The following settings can be set:

  • Frequency
    The frequency for the two systems must always be set. The Twin slave frequency cannot be higher than the Twin master. It is recommended to use the same frequency or a divisor of the Twin master frequency for the Twin slave, but it can be any frequency.

    If you do not use the same frequencies for the two systems then the data of the slave system is interpolated. When you use a divisor of the twin master frequency, then the interpolated data is just filled between the actual 3D data. If the twin slave frequency is not a divisor of the twin master frequency, then QTM will interpolate all of the slave data so that it matches the twin master frequency.

  • Enable Frame Sync
    When enabled the frame sync will control the External timebase settings of the two systems so that they are frame synchronized with each other. The use of Frame Sync is recommended. For information about how to connect the synchronization signal between the systems see chapter How to use frame synchronized twin systems with separate volumes.
    You need to select the Frame Sync Master Source that will send the 100 Hz continuous signal on its Sync out connection. The system with the Frame sync master source will be set to the Internal 100 Hz option for external timebase. The other system will be set to using the Control port or SYNC option. The Multiplier and Divisor options of the systems will be set to numbers displayed next to the Frequency setting.

    The 100 Hz continuous output is not available on Oqus 1, 3 and 5 series cameras; the use of Frame sync requires at least one other type of Oqus camera or a Camera Sync Unit.

  • Frame Sync Master Source (only available with the Frame sync option)
    Select the device that you want to use as frame sync master. This can be a sync output on the Camera Sync Unit or an Oqus camera. Devices with multiple sync out ports (e.g. Camera Sync Unit) will additionally let you specify which port to use (currently, only the Out 1 port on the Camera Sync Unit is supported for Twin). The Frame sync master source can be in either the Twin master or the Twin slave system.

Trajectory Conflicts

If there are two labeled markers with the same names in the twin master and twin slave file, then QTM will have to know how to handle the trajectories. QTM can either Merge trajectories or Rename trajectories with extension. If the trajectories are merged then the twin slave trajectory will be added to the twin master trajectory and if there are any overlaps the twin master data is used. When renaming the trajectories then the extension _slave is added to all of the labeled twin slave trajectories.

This option will only be used if the Twin slave file contains labeled trajectories. Most of the time it is recommended to not identify the data on the slave file and instead apply AIM to the merged data.

If the volumes are completely separated there will be no overlaps in the merged data.

Twin System Calibration

The Twin System Calibration page contains settings for the twin calibration of the two systems and describes the Translation and Rotation that is used for transforming the twin slave data to the twin master coordinate system. For information on how to perform a twin system calibration see chapter Performing a Twin calibration.

The result of the last twin calibration is displayed below the transformations:

  • Calibration time
    The processing time of the current twin calibration. Since it is only the processing time that is displayed you need to check which files that are used to be sure exactly what is used, see chapter Twin System Calibration dialog.

  • Average Wand Length (mm)
    The average wand length of the current twin calibration.

  • Wand Length Error RMS (mm)
    The wand length error of the current twin calibration.

Click on Reset Calibration if you want to zero the twin calibration data. Click on Calibrate to change the twin calibration, see chapter Twin System Calibration dialog.

Twin System Calibration dialog

The Twin system calibration dialog is opened with the Calibrate button on the Twin system calibration page. From the dialog you can control and change the current twin calibration. It can either be changed by updating the measurements used for twin calibration or manually.

  • Manual calibration
    Enter the translation and position of the twin calibration. If you have made a twin calibration from two files then it is the result that is displayed. However, you can also enter the numbers manually, but it is not recommended if you want the best accuracy. Click on Calibrate to update the twin calibration with the manually entered data.

  • Calibrate using two measurements
    These settings displays the current files used for the twin calibration. You can click Browse to change the files or change the Wand length. Click on Calibrate to update the twin calibration.