Arc-step model_file / ring_distribution maths

[jasonmnemonic]

Hi,

In the method get_arc_step_params, it refers to the model_file or the ring_distribution file and does the maths for the ring radius (column 0) and its working distance from the cone's first ring at the base (column 1).

Some excerpt from the file:

4.0 0.0
5.7 10.9
7.0 19.3
8.1 25.9
8.9 31.2
9.6 35.6
10.2 39.4
10.7 42.6
...

How does the maths in:

model.append(
                (   
                    # uncomment and use below in-case of oldest placido head
                    (model_temp[idx][0] + model_temp[idx + 1][0] - 2 + 0.5) / 2.0, 
                    #(model_temp[idx][0] + model_temp[idx + 1][0]) / 2.0,
                    (model_temp[idx][1] + model_temp[idx + 1][1]) / 2.0,
                )
            )

What is the numbers for -2 + 0.5 mean (what they refer to)?

Thanks.

[mohja1]

Good question.

We did this to adjust for the thickness of each ring (-2 was added as the inner diameter was 2 mm smaller than the outer diameter, with the ring thickness being 1mm). Due to this thickness, we need to adjust for the available space allowing the light to pass out. To compute the adjustment factor, we minimized that parameter for the reconstruction on a set of test images and found it to be 0.5 mm.