# TIRF and laser damage to the objective

**URL:** <https://forum.microlist.org/t/tirf-and-laser-damage-to-the-objective/1621>\
**Category:** Hardware\
**Created:** [November 29, 2021, 2:44pm UTC](https://forum.microlist.org/t/tirf-and-laser-damage-to-the-objective/1621 "2021-11-29T14:44:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![vytas\_z](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.microlist.org/vytas_z/32/903_2.png) [@vytas\_z](https://forum.microlist.org/u/vytas_z)\
**Post date:** [November 29, 2021, 2:44pm UTC](https://forum.microlist.org/t/tirf-and-laser-damage-to-the-objective/1621/1 "2021-11-29T14:44:46Z")

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Hi everyone,

Has anyone ever damaged their expensive TIRF objectives by focusing on the back focal plane (BFP) with too much power? I couldn’t get an answer from Nikoin about damage threshold (DT) at the BFP (I imagine the DT will depend on where the BFP happens to lie - near a coated surface/cement/or deep in a lens), they only mentioned that they did not observe issues with collimated beams filling the back aperture at 150mW (so it’s possible to work out a lower limit). The objective in question is HP Apo TIRF 100x/1.49NA (MRD01993). A senior academic was telling me horror stories about people burning spots in their precious TIRF objectives.

Cheers,  
Vytas

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**Author:** ![ShawnPatrickCasey](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.microlist.org/shawnpatrickcasey/32/712_2.png) [@ShawnPatrickCasey](https://forum.microlist.org/u/ShawnPatrickCasey)\
**Post date:** [December 1, 2021, 4:36pm UTC](https://forum.microlist.org/t/tirf-and-laser-damage-to-the-objective/1621/2 "2021-12-01T16:36:16Z")

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Do not know the answer. But have burned a lot of holes in things with lasers by accident over the years. Also a lot of frustrating conversations regarding damage thresholds with various vendors (one not too long ago with a linearly variable filter vendor regarding specific parameters related to its use with a supercontinuum laser). Often they do have data but not for the particular wavelength or parameters of your intended use case.

You might ask:

> **[Microscope Objective Lens & Part Repair | Nikon Plan Apo | Epic Optics](https://epicoptics.net/about-us/)**
>
> Our microscope alignment procedure and parts repair service will help our customer to get rid of microscope blurry image and removal contamination from the top lens

If someone damaged such an objective he may have repaired it. He has provided me with a lot information about the lenses which I didn’t know (particularly about the soft coatings on the internal surfaces of some lens elements within particular objectives). He may even have damaged individual lens elements left from a previous repair if you want to experiment without damaging a good lens.

Best of luck!