AP187 Act9: Stereometry

In this activity, we learned the technique called stereometry in which multiple (at least two) images of different views of the same object is used to obtain depth information. Instead of using two cameras, we captured two images of the same object but one is displaced a known distance from the original.

Figure 1: Two images of a rubix cube one is displaced with respect to the other

The focus of the camera is traditionally obtained by camera calibration like in Activity 8. However, for the camera that we've used the focus is already explicitly stated to be equal to 6.6cm.

Using the equation below, we can obtain the depth of the rubix cube based on the two images.

z = bf/(x2-x1)

where,

b is the displacement between the two images
f is the focus of the camera
x2, x1 are corresponding points on the object from the two images
z is the depth of the said point

We now consider the edges of the rubix cube as the corresponding points that will be used to calculate the the depth z.

Figure 2: 3D plot of the rubix cube

The figure above was obtained by plotting the the calculated depth and its corresponding x, y coordinates from either one of the two images. The figure indeed resembles the rubix cube. Credits to BA for letting us use his camera.