Wednesday, March 10, 2021

For those that like equations

In the last post I introduced a traffic light based, Augmented Information feature in DOFIS.

The augmented information sitting behind the feature is the defocus blur at the overlap between the depths of field of the last image taken and the current focus position.

The equation being:

Where: b is the defocus blur at the overlap in microns; f is the focal length, u is the focus distance of the last image captured (from the front principal); w the current focus distance, once again from the front principal; e the pupil 'extension', ie f*(1-1/pupil_mag); and n is the infinity aperture number.

The above equation is simply derived from the DOFIS model:

To get the most out of all the above, I've now added two presentation modes to the traffic light feature.

Mode 2 is as first posted, ie you only see the traffic lights if you have taken an image, and the traffic lights reset/disappear if you change focal length or aperture.

Mode 1 introduces a base traffic light set that is always there, until you take an image, when the traffic lights switch to mode 2. The mode 1 presentation, ie before an image is captured or after being reset, looks like this:

In the above we see the left hand traffic light telling us the impact of the current aperture's diffraction on the lp/mm 'quality': as also shown in the top right green box. This is a figure of merit % that is relative to the widest aperture at infinity focus. You can read about this in these two post: and

The right hand traffic light shows the infinity defocus blur (microns) as before.

As usual I welcome any comments or feedback on this or any of my posts.

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