Jan. 28th, 2019

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The holidays are over and I'm back to having a little hobby time here and there. With the LED mod assembled and in place, the coaxial illuminator is certainly much brighter than the original halogen-powered unit. Of course, an LED ring light still utterly destroys it, but the brightness level of the modded version is usable in a lit room, where the original halogen version really wasn't. So, yay.

However... contrast is damaged somewhat? Did I get some optics dirty?

A little investigation reveals our problem is at the primary constraint in the optical path. Specifically, the coaxial illuminator is designed to focus down an image of the light source right at the plane of the internal adjustable iris in order to get as much useful light through it as possible. You can see the glowing filament clearly when the iris is nearly closed, and it passes through cleanly with the iris open.

When the light doesn't clear the iris but shines on it instead, the light pollutes the image. Interestingly, this means the adjustable iris and coaxial illuminator don't really coexist well, a problem I hadn't noticed before but yup.... sure enough... the illuminator is only really useful with the iris wide open.

Possibly for this reason, the slightly later SZH10 dispenses with the adjustable iris for a fixed aperture, instead offering the iris as an accessory 'slice' that can be placed later in the optical path. This neatly avoids the contrast problem.

In any case, my problem is 90% a slight misalignment, easily dealt with.

That said, the square die image is just a bit too large to fit cleanly through the round iris opening even when aligned. A little optimization of my illuminator optics is probably called for.

But... can I actually do better? Olympus knew what they were doing, and if there was an obviously better lens design they'd have used it, right?

Stay tuned for our next exciting episode!


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