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Direct conversion of pixels to millimeters?

asked 2019-06-26 08:06:34 -0600


I found a point, I have its coordinates in pixels.

I would like to somehow convert these pixels into millimeters. I have internal and external camera data. I have X and Y in pixels, which I am looking for.

Can I directly translate pixels to millimeters and read in millimeters the data, does the lens get distorted? Will I be able to read the point like that? Does anyone know how different I can do it?

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answered 2019-06-26 11:33:13 -0600

crackwitz gravatar image

use intrinsic calibration parameters to turn the pixel coordinate (in 2d screen space) into a viewing ray (in 3d camera space). that is done in two parts, undistortion and "un"-projection (using the camera projection matrix). when you write down the linear algebra, you'll see how that results in a ray: projection removes one dimension, so this operation must add one dimension.

use extrinsic calibration parameters (transformation matrix between world space and camera space) to transform the viewing ray from camera space to world space.

intersect the ray with whatever surface you think made that pixel.

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Asked: 2019-06-26 08:06:34 -0600

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Last updated: Jun 26 '19