What flatness tolerance is achievable on optical part?

[AllInADaysWork]

We have an application which requires a 40x40mm section of a 85x130x10 plate to be optically clear as well as flat to ±0.005 (or better).
Does anyone have any recommendations on how to achieve this, what materials would be suitable, and if there is anyone out there who can produce it?
Low initial volumes for testing. Around a thousand or so parts. Laboratory environment, single use application.
I'm thinking PMMA but have seen Noryl suggested in some similar discussion threads.

Any advice appreciated.

 

[IRstuff]

Glass flats and mirrors can be much flatter than that. Have you looked at:

http://www.edmundoptics.com/optics/.../ito-coated-emi-shielded-plastic-windows/3366

TTFN
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[AllInADaysWork]

Interesting. Do you know what the material is and if it's moulded?
I'm trying to replace a glass slide in an assembly by incorporating it directly into a moulding. So far molders are very reluctant to committing to a tool which features such a flat section.

 

[IRstuff]

How flat does it NEED to be? You can see through Saran wrap pretty well, and its flatness is terrible.

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[AllInADaysWork]

Pretty flat. I'm not wrapping sandwiches here
I was asked to achieve 0.002mm but managed to nudge it out to 0.005mm.
There's a microfluidic space which needs to be maintained. Any irregularity means surface tension can cause a droplet to move. Plus it's area changes.
It's probably more important to be flat than to be clear, if it really is unachievable.
The current design uses 2 sheets of microscope slide glass with a film spacer.

 

[IRstuff]

Have you looked at Googling "PCR on a chip"

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[AllInADaysWork]

Yep. That's the kind of thing I'm working on.