Intrinsic using print
This method of calibration requires us to record a sheet of paper with charuco markers printed on it from various distances and angles.
Calibration is performed for a specific resolution and zoom level. When this calibration file is later loaded into a device, the device will support only that particular resolution.
Unlike extrinsic calibration, intrinsic calibration needs to be done just once for the given settings and can be reused without any problems.
If you do not have a board, please head over to [ Requirements ] and choose your use-case. Intrinsic calibration does not require big board, A4 is enough as we can physically move the camera or the board.
Navigate to Recording tab in AImation Studio and enable device you want to calibrate by clicking on the camera icon (enabled device turns green).
Switch from Recording Mode to Live Intrinsic Mode.
Select recording format ( Any FPS format that supports resolution you're targeting ) and resolution, remember that resulting calibration file will allow you to record ONLY at the resolution you've selected here.
Grab your print and place it on a flat surface, it can be for example floor, desk or attached to a wall. Make sure you can record the print from all angles, in this example we will place the print on the floor. Make sure the print is not wrinkled and it is as straight as possible.
Start preview of a device (play button under Recording Format), physically grab the recording device into your hand and point it at the print, at this stage we want to make sure it is visible with current lightning. This is great moment to tweak camera parameters such as exposure/brightness or other properties that the device registered in Windows, you can do this by clicking wrench button under camera icon. Once it's done you can stop the preview.
Input your print dimensions into Board Settings. If you've used image generated by AImation Studio you should also have a text file that contains this data.
It is good idea to measure squares and markers of your print to make sure that everything has been scaled properly during printing.
Before we begin recording our print, it is recommended to set a small delay before the process starts, it gives you a moment to get in place with the device.
Recording Length how long we will be recording the print, it cannot be stopped mid-recording. Recommended length is 1 minute and from the entire recording we will be prompted to select 10-15 images which will be used for calibration.
Once you're ready press Start Live Intrinsic and record the board from as many angles as possible. In example below we physically rotate and move the device around the board, at least 50% of the board has to be in view. Keep doing this for entire length of the recording while briefly holding still at each position to get at least one clear image.
Another way to place and record the print is to pin it to a wall and record it by moving recording device from side to side and then from the top to the bottom of the print.
Yet another way is to place the print on a flat board that does not bend and instead of moving the device, move and rotate the board with the print in front of the device.
Once the recording finishes you will be prompted with Intrinsic Picker UI.
Videos below represent in-app view during calibration as well as a recording of camera movements.
Intrinsic Picker UI
In the modal window that appeared we have to select 10-15 recorded images that will be used for calibration. Each item will have detections drawn over it to help you visualize.
We do this by right-clicking on the frame boxes in the bottom part of the screen. When frame is selected a smaller thumbnail will appear so you can go back and forth between selections and other frames. If an image does not have enough detections, you will not be allowed to select it for calibration.
Proper frame is where the detections are perfectly drawn over the markers and squares, and the lines are not tilted or looking imperfect.
Once selection is completed, press OK button to send the frames to calibration system. If you can find more unique images that you think are valid for calibration, you can always add more, it will slightly increase the calibration time. When it finishes you will be allowed to give it a name, we recommend to give it a unique name so you can later identify for which device this calibration file belongs to.
To load intrinsic calibration into device, press the wrench button under the camera icon and your calibration file should be present on the right side of the pop-up.
Below is a video example of above, saving and loading into a device.
