Camera calibration on OAK-FFC 4P

shivathapa

Hello, I'm trying to calibrate the camera on OAK-FFC 4P modules and for this, there isn't any board config provided in the repo https://github.com/luxonis/depthai-boards, so I defined the config on my own, here is the config I used

When I run the calibration script provided in the repo https://github.com/luxonis/depthai, I always end in an error for extrinsic calibration regarding

'high Reprojection Error', 'high epipolar error between left and right', 'high epipolar error between right and lef'

Is there any issue with the config I provided to the calibration script? The script mostly end with high Reprojection Error
Charuco board use for calibration is charuco board 11X8 provided in script
The camera used are
- OAK-FFC-OV9282 stereo mono camera

jakaskerl

Hi shivathapa
What command/args did you use to initialize the calibration script?
Perhaps the calibration was bad because of the lighting condition / the board not being fully visible?
Also, could you maybe modify the script so the cam_c doesn't have spec translation. Not sure if it will make a difference, but maybe the calibration is interpreted incorrectly because both cameras have translation information.

Thanks,
Jaka

shivathapa

Hello jakaskerl
The command I used is
python .\calibrate.py -s 3 -nx 11 -ny 8 -brd oak-fc-4p.json

Still getting the same issue even though I removed spec translation from the config file.

jakaskerl

Hi shivathapa
Like this?

{
"board_config":
{
"name": "Custom FFC",
"revision": "R1M0E1",
"cameras":{
 
"CAM_B": {
"name": "left",
"hfov": 71.86,
"type": "mono",
"extrinsics": {
"to_cam": "CAM_C",
"specTranslation": {
"x": 6,
"y": 0,
"z": 0
},
"rotation":{
"r": 0,
"p": 0,
"y": 0
}
}
},
"CAM_C": {
"name": "right",
"hfov": 71.86,
"type": "mono",
},
"stereo_config":{
"left_cam": "CAM_B",
"right_cam": "CAM_C"
}
}
}

And are you sure the square size is exactly 3cm? Also try passing the -db argument as well since you are using the default board.

Thanks,
Jaka

shivathapa

Thank you jakaskerl
By changing the square size to 2.2, and passing -db argument works successfully.
Also, I've one additional question, the config I use is just for mono camera. So for RGB Camera, adding a camera config like CAM_C will work, or need to change anything apart from camera config?

jakaskerl

Hi shivathapa
If you wish to add an additional camera (COLOR) you will need to create another entry eg. CAM_A (to which the rgb ffc camera is connected) and set the configuration so type is color and extrinsics are in relations to either the CAM_B or CAM_C. Then, the calibration should work fine for all three cameras.

Thanks,
Jaka

Tjjl

Hi ，jakaskerl

I'd like to inquire about an issue regarding FFC-4P AD calibration. When setting camera A to "mono," it reports an error KeyError: 'OV9782'. However, when setting A to "color," calibration can proceed, but the error in camera A is significantly large, ultimately leading to calibration failure. I'm using OV9282 cameras, and BC calibration proceeds normally. How can I resolve this issue?
Thanks

jakaskerl

Hi @Tjjl
I'll edit the calibration script to fix this. In the meantime:

Update the repo and this to the line below 356:

cameraProperties[0].sensorName = "OV9282"
cameraProperties[0].supportedTypes = [dai.CameraSensorType.MONO]
cameraProperties[3].sensorName = "OV9282"
cameraProperties[3].supportedTypes = [dai.CameraSensorType.MONO]

jakaskerl

luxonis/depthai1165