Kohler Issue

[JGardner]

I recently got a replacement stage for my Zeiss Universal, which has been out of service for some time. The new stage works fine, but I'm having issues setting up Kohler illumination that I don't remember having before. I checked the stage alignment, and it's as it should be, so no problems there.

The issue is that when I close down the field iris, center it in the field of view, and then move the condenser up and down to focus on the iris blades, I can only do this for low magnification objectives, like 4x and 6.3x. When I try it with the 10x and 40x objectives, I can't get the iris blades in focus even with the condenser all the way down.

Here's my Kohler procedure:

• Place slide on stage and focus the image by moving the stage up and down.

• Close down the field iris to minimum.

• Center the circle of light visible through the eyepieces in the field of view using the condenser centering screws.

• Bring the field iris blade edges into focus by moving the condenser up and down.

• Open field iris so edges of the blades are nearly at the edge of the field and re-center using condenser centering screws.

• Open field iris so blade edges are no loner visible.

• Set condenser iris to illuminate 65-80% of the exit pupil.

What am I doing wrong here? I follow the same procedure on my Orthoplan and have no trouble focusing on the iris blade edges even with 32x and 40x objectives.

[Hobbyst46]

I recently got a replacement stage for my Zeiss Universal, which has been out of service for some time. The new stage works fine, but I'm having issues setting up Kohler illumination that I don't remember having before. I checked the stage alignment, and it's as it should be, so no problems there.

The issue is that when I close down the field iris, center it in the field of view, and then move the condenser up and down to focus on the iris blades, I can only do this for low magnification objectives, like 4x and 6.3x. When I try it with the 10x and 40x objectives, I can't get the iris blades in focus even with the condenser all the way down.

Here's my Kohler procedure:

• Place slide on stage and focus the image by moving the stage up and down.

• Close down the field iris to minimum.

• Center the circle of light visible through the eyepieces in the field of view using the condenser centering screws.

• Bring the field iris blade edges into focus by moving the condenser up and down.

• Open field iris so edges of the blades are nearly at the edge of the field and re-center using condenser centering screws.

• Open field iris so blade edges are no loner visible.

• Set condenser iris to illuminate 65-80% of the exit pupil.

What am I doing wrong here? I follow the same procedure on my Orthoplan and have no trouble focusing on the iris blade edges even with 32x and 40x objectives.

The procedure as listed above is fine. It should work.
One possibility is that the auxiliary lens below the condenser (the one that is just above the filter holder) is swung in. Try swinging it out for the 40X at least. This lens is usually needed only for the low mags, e.g. 6.3X. Perhaps the 10X as well.