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recovering ext and int parameter from camera matrix

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recovering ext and int parameter from camera matrix

Postby deduu » Thu Jul 25, 2013 7:00 am

Hi,

I have been learning the material about camera calibration and got stuck in my way to understand how to recover extrinsic and intrinsic camera parameter from camera projection matrix.

In general, we can derive camera projection matrix by solving the equation from correspondence of 3D world coordinate to 2D screen coordinate and that is, we get an matrix let's say "C"

C = [c11 c12 c13 c14; c21 c22 c23 c24; c31 c32 c33 c34]

And ussually, without loss of generality we can assign c34 = 1 and we can find the rest of the element through correspondences 3D-2D.

After that, we can compare to conjuction of ext and int matrix (let's say M) that can be arranged to be

M = [fxr1+uxr3 fxtx+uxtz; fyr1+uyr3 fytx+uytz; r3 tz] where r1, r2, r3 are the row vector of Rotation matrix and tx,ty,tz are translation.

What I could not make out is when we compare each of C elements to M elements to get the ext and int parameter, our tz (translation about z) will be 1 because we have assigned c34 prior to be 1. Is this true?
deduu
 
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