50X objective recommendation

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jnh
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Re: 50X objective recommendation

Post by jnh »

I just received my M50, and literally only 10 min ago, I had a first look through it at a chip wafer. Unless I have an odd specimen, I'd say the 1 mm working distance estimate is very optimistic. In order to get something into focus the objective was pretty much sitting on the waver (no air gap that I could discern). From that position I was turning the lead screw on the WeMacro rail by hand, and with about an eighth of a turn (~100 um) I'd hit the top of the wafer.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

Your tube lens not being focused to infinity could change the working distance. How do you have it set up?

jnh
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Re: 50X objective recommendation

Post by jnh »

I'm using it with a Raynox DCR-150 with roughly 180 mm tube length. Adding another 25 mm extension to bring it closer to 200 mm doesn't change the very tight working distance.

Adalbert
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Re: 50X objective recommendation

Post by Adalbert »

Hi,
For the NA=0.65 the DOF=0,001302mm.
So, you will need the steps smaller than the DOF.
Usually I use the step-size=DOF/3 but for such NA the DOF/4 or DOF/5
Best,
ADi

jnh
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Re: 50X objective recommendation

Post by jnh »

Wow - what kind of rail are you using to reach ~250 nm steps? That is closer to linear servo territory.

Lou Jost
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Re: 50X objective recommendation

Post by Lou Jost »

Wow - what kind of rail are you using to reach ~250 nm steps? That is closer to linear servo territory.
You can get step sizes almost that size with simple, cheap off-the-shelf microscope focusing block driven by the cheap WeMacro MicroMate.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

jnh wrote:
Thu Jan 14, 2021 4:28 pm
I'm using it with a Raynox DCR-150 with roughly 180 mm tube length. Adding another 25 mm extension to bring it closer to 200 mm doesn't change the very tight working distance.
Bummer. Is image quality good at least? It looks like they made these mitutoyo/akashi hardness testers for some tiem so they may have had a few with different specs.

Pau
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Re: 50X objective recommendation

Post by Pau »

Lou Jost wrote:
Fri Jan 15, 2021 5:53 pm
Wow - what kind of rail are you using to reach ~250 nm steps? That is closer to linear servo territory.
You can get step sizes almost that size with simple, cheap off-the-shelf microscope focusing block driven by the cheap WeMacro MicroMate.
This is what I do, depending of the microscope focus block I can work at 100 or even 50 nm step size
Pau

Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Re: 50X objective recommendation

Post by Adalbert »

Hi,
Wow - what kind of rail are you using to reach ~250 nm steps? That is closer to linear servo territory.
I use this one (home-made)
https://www.photomacrography.net/forum/ ... nano+steps

Best,
ADi

jnh
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Location: US East Coast

Re: 50X objective recommendation

Post by jnh »

So, this M50/0.65 didn't work out so well for me. If anyone is interested to play around with it, I'd be happy to ship it out to someone (in the US).

Still might be interested in exploring some options for sub-micron stepping. Certainly lots of good suggestions above (Thanks!). With regards to focus blocks, the well regarded Olympus BHMJ is actually quite expensive. Would something much cheaper (e.g. https://www.ebay.com/itm/Stereo-Microsc ... 3448954661) be equally suitable/capable?

rjlittlefield
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Re: 50X objective recommendation

Post by rjlittlefield »

jnh wrote:
Sun Jan 17, 2021 9:37 am
With regards to focus blocks, the well regarded Olympus BHMJ is actually quite expensive. Would something much cheaper (e.g. https://www.ebay.com/itm/Stereo-Microsc ... 3448954661) be equally suitable/capable?
Very interesting! Today's price of $62.91 for a focus block spec'd as "One scale of fine focusing: 0.002 mm" Markings on the focus knobs suggest that fine focus is 200 microns/turn, same as the Olympus blocks. This is ball bearing, versus rollers in the BHMJ, but that by itself is no problem for what we do.

I have not laid hands on one of these blocks. From general principles I would expect it to behave about the same as the focus block that I tested and reported at "Amscope B490/T490 focus block is good for stacking".

--Rik

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

Do not buy that focus block. It's trash, I have gotten two of them in hand (one used one new) and neither even works. Really bad build quality.

I have a couple of the focusy parts from bhmjs coming in that I got a deal on. If they are good I can pass one on--maybe a swap for the objective if you didn't pay too much for it?

Here's an obscure solution that might work too: https://www.ebay.com/itm/152095412821. Might be worth a lowball offer.

Lou Jost
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Re: 50X objective recommendation

Post by Lou Jost »

I use several Nikon focusing blocks bought cheaply on eBay, and two of the three are excellent. The third was unacceptable but I could have returned it if I had lived in the US and been able to inspect it on delivery.

jnh
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Location: US East Coast

Re: 50X objective recommendation

Post by jnh »

@Scarodactyl: Thanks! I'd be happy to swap that objective (paid $120 for it) for a focus block, if that would be a fair trade for you.

Scarodactyl
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Re: 50X objective recommendation

Post by Scarodactyl »

I'll shoot you a message when it comes in and I've tested it out.

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