Errors in Image Intensity

Errors in Line Estimation

Errors in Movement

Erroneous Shape Estimation

Errors in Image Intensity
Spring Pattern

Figure 1

This pattern is a perfect square grid with black squares superimposed that give the illusion of the lines being bulged.

Let us look closely at the image, smooth the image and then detect the edges, as illustrated below. Where there is a single line smoothing causes the edges to drift apart (type 2 edges). But where there is a block against the line, there is a single edge (type 1), which stays in place.

Figure 2

The next set of pictures takes an even closer look and provides movement vectors that show how the edges move from their original positions.

Figure 3

The video below illustrates the computations.