What Are the Best Optical Filters for Diverging Light?

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Discussion Overview

The discussion centers around the suitability of various optical filters for use with diverging light, particularly in the context of a low-cost fluorescence system. Participants explore the challenges of filtering excitation and emission wavelengths effectively while managing costs and the implications of using different types of filters.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Tom questions the availability of optical filters that work effectively with diverging light, noting that most encountered filters are designed for collimated light.
  • One participant suggests that chemical filters (colored glass) can be used with diverging beams, while interference filters may not perform as well unless angle uniformity is not a concern.
  • Tom expresses a specific need to filter excitation wavelengths (488nm +/-10nm) from emission wavelengths (515nm) in a low-cost setup, highlighting the difficulty of achieving this with high-quality filters designed for collimated light.
  • Another participant questions the cost concerns regarding collimating the beam and inquires about the illumination method being used (epi-illumination vs. trans-illumination).
  • Tom clarifies that he is aiming for a low-cost solution, comparing the prices of diverging and collimating objectives, and indicates a preference for an epi-illumination setup but acknowledges limitations due to diverging beams.
  • A participant estimates the cost of a three-filter set suitable for Tom's specifications and suggests that a simple plano-convex lens could provide sufficient collimation at a lower cost.
  • Another participant notes that there are filters that can function with diverging light but requests more details about Tom's application to provide better suggestions.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness and cost of various optical filters for diverging light. There is no consensus on the best approach or solution, and the discussion remains unresolved regarding the optimal filtering method for Tom's specific application.

Contextual Notes

The discussion highlights limitations related to the specific requirements of filtering tight wavelength bands and the trade-offs between cost and filter performance. There are also unresolved questions about the application context and the implications of using different illumination methods.

tommyers
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Hi,

Is there a particular type of optical filter which is suited for use with diverging light? Most of the filters which I have encountered; dichroic, interference ... are suited to collimated light.

I have an application where I would like to long pass filter a diverging beam of light between an objective and eyepiece.

Regards,
Tom
 
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Chemical filters (colored glass) are fine in diverging beams - it's only a problem for interference filters.
Even then if you aren't too concerned about all the angles having exactly the same bandpass they will still work
 
The problem I have is that I am trying to produce a low-cost fluorescence system and as such I am trying to filter the excitation wavelength (488nm +/-10nm) from the emission wavelength of 515nm.

With such a tight band between exciatation and emission, the best filters, including the dichroic beam splitter, ideal for such a job rely on collimated light, but then that negates the low-cost aspect.

Question is can I get enough information to do what I need with high background emission from the light which would not be fully attenuated by the long pass filter (chemical or otherwise).

Regards,
Tom
 
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If you are willing to pay for a high-end filter set, I'm surprised you say it's too expensive to collimate the beam.

Are you doing this using epi-illumination or trans-illumination?
 
If you are willing to pay for a high-end filter set

Did I?

I am trying to make this low-cost.

A DIN 60X objective (diverging) costs around £130, a 60X collimating objective costs around £1,300.

Ideally I would like to create a epi-illumination set-up, but it looks like I will only be able to achieve trans-illumination because of the diverging beams and the lack of being able to use a beam splitter as required in the epi-illumination.

Any suggestions greatly welcomed.

Regards,
Tom
 
tommyers said:
Did I?
<snip>

I think so:

tommyers said:
[...] I am trying to filter the excitation wavelength (488nm +/-10nm) from the emission wavelength of 515nm.

With such a tight band between exciatation and emission, the best filters... <snip>

Given the specs you posted, I estimate the three-filter set at around US$500, if you are using standard 25mm diameter filters and 'standard sets' (i.e. GFP, FITC). I regularly use Omega and Chroma- Chroma is a great company to work with.

By contrast, a simple plano-convex lens will give sufficient collimation for $20, and add another $100 for the mount.

But reading more of your post, I wonder if this is an imaging system or not- what is your application, exactly? There may indeed be a simple, inexpensive method.
 
Actually, there are some filters with the function of with diverging light, it depens on your appliaction, and what effect do you wan to reach? could you tell details about your application?


--------------
Lisa
www.refetoptics.com[/URL]
 
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