Introduction
This project introduces the calibration procedures available in the LabMaestro software.
Prerequisites
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LabMaestro is installed and activated.
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You have set up your TRACKPixx3 eye tracker through your DATAPixx device.
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Be familiar with Environment and Devices Overview
Preparing your tracker for calibration
Before calibrating your tracker, you can take steps to ensure higher calibration quality. These include defining the iris’s expected size and search limits. By clicking the Configure TRACKPixx option, LabMaestro gives you two options to do this:
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Automatic: From LabMaestro version 1.10 onwards, you can use the Detect Optimal Settings option. When clicking this option, your participant will be asked to look straight ahead. A detection algorithm will automatically run on the TRACKPixx visual recording to locate the eyes, define optimal search limits, and estimate the expected iris size. After this, a bar at the bottom will help you hone the TRACKPixx's focus to perfection. Once you are done, you can click the Stop Focus Tuning button to stop the focus bar from appearing. If needed, you can then manually adjust some of these parameters to your liking.
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Manual: You can also define these parameters manually.
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Iris expected size can be adjusted using a slider. The more you slide to the right, the bigger the iris region is.
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You can enable search limits using a toggle. Then, using your mouse, you can define a search area by highlighting it in the camera video feed. The left-eye search limit is defined by interacting with the left side of the screen, and the right-eye search limit by interacting with the right side.
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Calibrating the TRACKPixx3
Before running an experiment, it is necessary to calibrate your tracker to infer gaze location from your participant's eye movements. There are two main ways to calibrate your tracker: either the Configure TRACKPixx window or through the Calibrate Tracker component. Regardless of the calibration method you use, the LabMaestro calibration routine is the same: it displays calibration targets in sequence and shows a feedback screen once the calibration is complete.
Calibration Through Configure TRACKPixx
This option is best if you need to run a calibration before the start of an experiment session. First, select the Calibrate option. This will open a contextual window where you can edit the various properties of your calibration routine. These are the following:
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General:
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Mode: Define the calibration mode. Automatic automatically cycles between calibration targets. Triggered only cycles to the next calibration target when the trigger key is pressed.
Manual requires an experimenter to select calibration targets. This advanced option requires a second monitor. -
Target Count: Define the number of calibration points measured. Options are 3, 5, 7, 9 or 13.
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Trigger Key: Define a trigger key to switch calibration target if using triggered mode.
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Show Feedback Screen: Define when to show calibration feedback. Never will show any feedback. On Failure will only show feedback if one or more targets exceed the acceptable offset. Always will always show feedback after calibration.
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Feedback Screen Font Size (px): Define the text size of the feedback screen.
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Advanced:
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Target Stabilization Time (ms): The time (in ms) required for the calibration target to stabilize at its final size.
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Target Min Size (px.): Define the minimal/final width (in pixels) for calibration targets.
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Target Max Size (px): Define the maximal/starting width (in pixels) for calibration targets.
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Precalibration Countdown (s): Presents a countdown from the specified value, before beginning the calibration procedure. If the pre-calibration countdown is set to 0, no countdown will be shown.
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Appearance:
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BackgroundColor: Define the background colour during the calibration task.
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ForegroundColorA: Define the colour of fixation targets. Each calibration target will alternate between the colours specified by ForegroundColorA and ForegroundColorB at 5 Hz during the target stabilization time.
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ForegroundColorB: Define the colour of fixation targets. Each calibration target will alternate between the colours specified by ForegroundColorA and ForegroundColorB at 5 Hz during the target stabilization time.
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Custom Target: Replace the usual fixation targets with a custom resource. You must first import a resource before it becomes selectable.
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Media Scaling: Define the size of custom calibration target stimuli as a proportion. The default value of 1.0 will use the resource file's full size.
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Calibration Through the Calibrate Tracker Component
The second option is to use the Calibrate Tracker command component. This option is better suited to experiments where you may need to calibrate/recalibrate your tracker multiple times. Like all components, you can read more about its properties on the Command Components page.
Whenever you place a Calibrate Tracker component in your Timeline, a calibration routine similar to the one from the Configure TRACKPixx menu. You can also use a Validate Tracker component to measure the quality of your calibration. This allows you to run multiple calibrations and/or validations as needed during your experiment.