Center of captured image is not the center of the lens

OpenMV Boards
1

I am using my OpenMV H7 Cam to assign a position to an object in space. I have it set up on my robot hand.
The problem is, the application needs to know where the center of the camera lens is.
I would assume that the center of the lens is at the center of the image I get back from my camera.

In testing that seams to not be the case. Bellow is a photo of my setup. The bright flashlight (on the chair) is at the center of the frame in the OpenIDE, but the robot hand is pointing slightly bellow that. Some 1 - 2° lower than it should. The resolution is set to QQVGA.

20211208_174505
20211208_1745051920×865 114 KB

Is this the limitation of my lens? Is maybe the global shutter lens more accurate?

2

The lens is mounted by set screws. It’s not calibrated or anything. You need to calibrate where the center of the camera lens is.

3

How do I calibrate? Is it even possible to get it to center?

4

Um, you crop your image such that it’s centered. Or, you move the lens around to fix.

5

The thing is, the problem is present only on the vertical line. The horizontal one seams to be in perfect center always.
I don’t know how to crop the image, but i did try to define a new center by code (on the vertical line). It seams to fix the problem, but when I move the object further away from the camera or closer the problem repeats.

It doesn’t work well. something is not right.

6 
OFFSET = 10
sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)
# if center is higher
sensor.set_windowing((0, 0, sensor.width(), sensor.height() - OFFSET))
# if center is lower
sensor.set_windowing((0, OFFSET, sensor.width(), sensor.height() ))

Tune offset until it’s centered.