CODEWITHSUNDEEP
computer-visiontriangulation3d-reconstruction
AlbusPotter
AlbusPotter

Reputation: 19

Intrinsic Parameters of Camera

I'm trying to do triangulation for 3D reconstruction and I came across an interesting observation which I cannot justify.

I have 2 sets of images. I know the correspondences and I'm finding the intrinsic and extrinsic parameters using a direct linear transformation. While I'm able to properly reconstruct the original scene, the intrinsic parameters are different even though the pictures are taken from the same camera. How is it possible to have different intrinsic parameters if the camera is the same? Also, if the intrinsic parameters are different, how am I able to reconstruct the scene perfectly?

Thank you

Upvotes: 0

Views: 188

Answers (1)

Ash
Ash

Reputation: 4718

You haven't specified what you mean by "different", so i'm just going to point two possible sources of differences that come to mind. Let's denote the matrix of intrinsic parameters with K.

The first possible difference could just come from a scaling difference. If the second time you estimate your intrinsics matrix, you end up with a matrix 

K_2=lambda*K

then it doesn't make any difference when projecting or reprojecting, since for any 3d point X you'll have 

K_2*X=K*lambda*X //X is the same as lambda*X in projective geometry

The same thing happens when you backproject the point: you just obtain a direction, and then your estimation algorithm (e.g. least squares or a simpler geometric solution) takes care of estimating the depth.

The second reason for the difference you observe could just come from numerical imprecisions. Since you haven't given any information regarding the magnitude of the difference, I'm not sure if that is relevant to your case.

Upvotes: 1

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