Getting flat field out of Mitutoyo 5x / 7x objectives

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bokemon
Posts: 20
Joined: Sun Jan 16, 2022 6:06 pm
Location: Silicon Valley, CA

Getting flat field out of Mitutoyo 5x / 7x objectives

Post by bokemon »

Hello again,

In another thread, I asked about a setup for doing machine vision on flat samples, sort of like microchip inspection. After learning a few things, I think a good combo to use would be the Mitutoyo 5x or 7.5x objective with something like a Raynox DCR 250 to "squeeze" as wide a field of view as possible onto a high megapixel 4/3" sensor. But unlike most of you, I won't really have the option to do a lot of focus stacking since the plan is to capture the images in one go, and then either digital zoom into the areas of interest (if still sharp) or worst case, pan the sample over with the XY stage and image again. Or do a 2-3 stack image. And so I would like to get as flat a field as possible into the corners. I see that sometimes people test with flipping the tube lens backwards, or using non-infinity spacings. For now, I'm not using coaxial illumination, so I don't care too much about the infinity space, but maybe later I will.

What's the right way to test / tweak to get the flattest field possible? I'm also willing to throw more money at it and get more expensive tube lenses, e.g. Thorlabs or Olympus units.

Lou Jost
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Re: Getting flat field out of Mitutoyo 5x / 7x objectives

Post by Lou Jost »

Does it have to be in color? If not, you can use the absolutely flattest-field lenses available, the photolithography lenses that made microchips. They are readily available on ebay at 5x and 10x. They have huge absolutely flat fields. Difficult to work with though.

bokemon
Posts: 20
Joined: Sun Jan 16, 2022 6:06 pm
Location: Silicon Valley, CA

Re: Getting flat field out of Mitutoyo 5x / 7x objectives

Post by bokemon »

yes, it does have to be in color.
I like the notion of using the infinity objectives since it gives me the option to do stuff in the infinity space like insert illumination, polarizers, lasers, u name it.

Lou Jost
Posts: 5944
Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

Re: Getting flat field out of Mitutoyo 5x / 7x objectives

Post by Lou Jost »

Yes, that would be a much more general solution. I just like to remind people of these photolithography lenses in case their application fits.

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