Baader solar film question

[beamer3.6m]

Hi.

It's been a long time since I have been on this form but I always remember it being a helpful and friendly place so thought I might ask this somewhat unusual question here.

I have a CNC machine which I am going to mount laser module on so that I can cut various accessories for my scope (acrylic eyepiece holders etc).

I want to add an extra layer of protection from the laser and thought baader solar film may be of use if I were to stick it to a clear acrylic sheet.

The lasers wavelength is 450nm.

Would the baader sheet shield this wavelength but still allow the laser beam/spot to be seen?

Your help is appreciated.

[Wyvernp]

I have a feeling that the laser will simply burn through the film.

Sorry just re-read this

I thought you meant protection against the laser beam itself. It might be worth a go.

Edited April 17, 2020 by Wyvernp

[Peter Drew]

I doubt whether the laser beam would be bright enough to show but the spot might.  There is a photographic version of the film that has less extinction.     🙂

[Wyvernp]

1 minute ago, Peter Drew said:

I doubt whether the laser beam would be bright enough to show but the spot might.  There is a photographic version of the film that has less extinction.     🙂

That's a good point, 450nm is not particularly bright to the human eye. It's possible that when it's actually in use the laser spot may give off other wavelengths but it will probably depend on what you are cutting.

[vlaiv]

Not easy one to do from the top of the head.

Let's try some reasoning. Baader solar film is ND5 which means it attenuates 10^5 times.

That is 10 magnitudes (stellar) of difference. Using telescope one can easily see 10 mags of difference - Vega and mag 10 star and Vega, while bright is not unbearable to look at (I'm comparing 8" views from memory here).

If your laser spot is anywhere as bright as Vega in a telescope - you should be able to see it thru ND5 filter.

[beamer3.6m]

The laser spot will be far brighter than Vega. The laser comes with safety Googles which are od3+ I believe but you can still see the laser spot and the item being etched/carved.

Ideally I want to be able to see the laser spot (so it can be focused etc) but at the same time avoid the potential dangers to viewers of the process.

This is available in the US but the shipping is silly money... https://jtechphotonics.com/?product=445nm-laser-shielding the images however show a good idea of the laser brightness however.

[vlaiv]

2 minutes ago, beamer3.6m said:

The laser spot will be far brighter than Vega.

I'm aware of that - I was just pointing out that human eye has quite dynamic range. It can see 0mag star and 13mag star in the same scope without much difficulty.

This means that if something is very bright - and we attenuate it by ND5 type filter - it will still be visible to human eye under right conditions. So to address original question

4 hours ago, beamer3.6m said:

Would the baader sheet shield this wavelength but still allow the laser beam/spot to be seen?

It is ND type filter so it blocks all wavelengths and under right circumstances you will be able to see laser spot thru this filter. When I say right circumstances - that depends on how strong reflected laser light is and how bright ambient is. You might need to pull on the shades to create darker ambient to get enough contrast for laser beam / spot to be seen good.

[beamer3.6m]

I assumed it was just a case of the baader film blocked certain wavelengths and thus reduced the damage/brightness (wrong word) of the sun which can still be seen through it.

I couldnt find the wavelengths the baader film blocked and thought that 450nm (blue laser) might still get through but with any harmful rays (wrong word) being blocked.

I'm obviously wrong.

Edited April 17, 2020 by beamer3.6m

[vlaiv]

1 minute ago, beamer3.6m said:

I assumed it was just a case of the baader film blocked certain wavelengths and thus reduced the damage/brightness (wrong word) of the sun which can still be seen through it.

I couldnt find the wavelengths the baader film blocked and thought that 450nm (blue laser) might still get through but with any harmful rays (wrong word) being blocked.

I'm obviously wrong.

No, it's just ND type filter (a good one) which means that it blocks all wavelengths equally (neutral density - meaning no preference to any wavelength).

I also found this very interesting table / chart that might be of use:

If Welding shade number 13 blocks laser enough - so will ND5 by Baader. If you need less blocking there is photographic filter - ND3.8 I believe.