Activity 6. Camera Calibration

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Hayy.. after a very long time of staying as a draft... here is my blog report for the 6th activity. whew!

Introduction
When taking a picture, one can think that the object's world (actual) coordinates are being mapped into the camera's coordinates.

This activity allows us to get the camera properties so that we can get the actual or world-coordinates just from the pictures collected by this camera.

A readily available Matlab Toolbox can be used or one can program his own codes.



Methodology
Pictures of a tsai grid at different orientations are collected. Then the program should successfully trace the squares in the grid. Finally, the program will compute for the camera properties using two methods:

A. Camera calibration using the available Matlab toolbox from the internet, and
B. Camera calibration using our own codes. In this part, two Tsai grids are oriented perpendicular to each other.

Shown in Figure 1 are five of the 17 images I used for part A, and shown in Figure 2 is the Tsai grid I used for part B.

Figure 1. Few of the figures I used for part A of this activity.

Figure 2. The image used for calibrating the camera using own code.

Results
A. Figure 3 shows the calibration done for images in Figure 1. As one can see the corners of each of the squares are correctly predicted. As a plus from the toolbox, the errors and the extrinsic parameters can also be computed. Here i computed it and the results are shown in Figure 4.

Figure 3. Camera calibration results using the available toolbox.


Figure 4. The computed errors and the extrinsic parameters of the camera.

B. For part B, I had a hard time since I had to click all the input points for the program. I had to click at least 25 points and one mistake... just one mistake... will bring me back to zero. So for this part, Rene kindly offered his help not only in the Matlab program but also in clicking the images when I got too upset repeating the clicking process for the 3rd time.

Figure 5s is a sample of my failures in clicking the Tsai grid. hehe :) And Figure 5b shows the correct calibration done.


I put in a lot of effort in this activity especially patience. :) I give myself a grade of 9 for I posted my report so late. :)