My measurements with the OAK-D Pro out of the box have been off anywhere from 1-8cm. and I'd like to try calibrating the camera to see if it improves the depth accuracy. I can't find documentation on how to use the calibrate.py script at https://github.com/luxonis/depthai/blob/main/calibrate.py I see there is a youtube video here for it but the instructions are unclear https://www.youtube.com/watch?v=ZT2AqNC2xDY How is this script meant to be used?

@"erik"#175 Awesome! That's what I was looking for. I went through the calibration steps and for the most part the depth information seems to be more accurate now, however I noticed the depth isnt as accurate when the subject is not centered. For example, If I have a book that I move horizontally along a counter, the depth reading is fairly accurate when it is straight ahead of the camera and gets less and less accurate as it goes on. [upl-image-preview url=https://discuss.luxonis.com/assets/files/2024-08-09/1723241857-95268-tv-1.png] Diagram here shows what I measure with a tape from the camera to the book itself. The actual results from the depthai_viewer are Expected: 75cm -- Measured: 72.8 Expected 75.5 -- Measured: 72.8 Expected 77.5 -- Measured: 74.2 Expected 81 -- Measured: 74.6 I have tried with various objects and distances, and experimented with the speckle filter and it seems simlarly to lose accuracy if not centered. Is this a result of improper calibration or has this issue been resolved before?

Calibrating OAK-D Pro

JakeMarquez

My measurements with the OAK-D Pro out of the box have been off anywhere from 1-8cm. and I'd like to try calibrating the camera to see if it improves the depth accuracy. I can't find documentation on how to use the calibrate.py script at luxonis/depthaiblob/main/calibrate.py

I see there is a youtube video here for it but the instructions are unclear

How is this script meant to be used?

erik

@JakeMarquez what's unclear about the script? Are you interested in any specifics?

JakeMarquez

@erik just general expected usage. I did not know what a charuco board is, but I found this online generator for one but I have no way of knowing they are all the same or there is a specific configuration required https://calibrate.deepen.ai/target-generator

Additionally, the script comment by the args says the board should be printed and fixed to a flat surface yet the video shows it being done with a computer screen. When I try with my computer screen it does not recognize the squares.

Are the square size measurements to be taken on the physical monitor? I measured the squares on my monitor at 2.9cm for this. What distance is the camera supposed to be from the monitor? What angle?

Some general guidance would be apreciated, thanks

erik

@JakeMarquez ah I see, you should follow the tutorial on our docs page:
https://docs.luxonis.com/hardware/platform/depth/calibration/

JakeMarquez

@erik Awesome! That's what I was looking for. I went through the calibration steps and for the most part the depth information seems to be more accurate now, however I noticed the depth isnt as accurate when the subject is not centered. For example, If I have a book that I move horizontally along a counter, the depth reading is fairly accurate when it is straight ahead of the camera and gets less and less accurate as it goes on.

Diagram here shows what I measure with a tape from the camera to the book itself.

The actual results from the depthai_viewer are

Expected: 75cm -- Measured: 72.8

Expected 75.5 -- Measured: 72.8

Expected 77.5 -- Measured: 74.2

Expected 81 -- Measured: 74.6

I have tried with various objects and distances, and experimented with the speckle filter and it seems simlarly to lose accuracy if not centered. Is this a result of improper calibration or has this issue been resolved before?

jakaskerl

Hi JakeMarquez
It's very likely this is an undistortion issue which stems from a bad calibration. Are you reading raw depth values or are you performing any calculations on top? Can you show a disparity image of a flat surface. It should be radially symmetric in that case.

Thanks,
Jaka

JakeMarquez

@jakaskerl using gen2-calc-spatials-on-host example I took this disparity image, also BW photo for reference

71cm was the expected distance from the camera to the wall. Additionally I took these photos with a box in front of the wall, just moving the ROI from center to edge of box expecting distance to increase:

Photo A -- Expected: 66cm, Actual: 66cm

Photo B -- Expected 71cm, Actual 66cm

There is definitely distortion, is this amount unexpected, or due to calibration issues? -- Thanks

jakaskerl

JakeMarquez
Oh, that's to be expected. The Z gives you shortest path from object plane to camera plane - looking at Z when pointing camera at a flat perpendicular surface (pointing at a wall), all points on the wall should have the same depth Z.

You want euclidean distance which is -- sqrt(x^2 + y^2 + z^2)

Thanks
Jaka

JakeMarquez

Ah thank you for clearing that up!