Question about filtering out the blue wavelength from lights

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Discussion Overview

The discussion revolves around finding a method to filter out blue wavelengths from a light source for a research project. Participants explore various types of optical filters, their properties, and methods for verifying their effectiveness. The scope includes technical specifications of filters and practical applications in experimental settings.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests using a photographic filter to remove blue wavelengths and proposes testing its effectiveness using a photospectrometer.
  • Another participant questions whether a notch filter (which absorbs a specific waveband) or a pass filter (which transmits a waveband) is needed, and challenges the necessity of grinding the filter for transmittance measurement.
  • There is a suggestion that a low pass filter might be appropriate, depending on whether UV light needs to be retained.
  • A participant expresses a preference for a notch filter to ensure blue light is not transmitted, noting the potential expense of such filters.
  • One participant mentions finding a list of optical properties for Wratten filters, indicating they are inexpensive and have quantitative data available, which they plan to suggest to their professor.

Areas of Agreement / Disagreement

Participants express differing views on the type of filter needed (notch vs. low pass) and the method of verifying filter effectiveness. There is no consensus on the best approach or filter type, indicating ongoing debate.

Contextual Notes

Some assumptions about the definitions of filter types and their applications remain unresolved, and the discussion does not clarify the specific requirements of the research project.

vande060
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I volunteered to help out with a research project, and we need a solution for a way to filter out light of the blue wavelength from a light source. THe blue wavelength is the only wavelength we want to remove. I was wondering if anyone here had any suggestions? Someone from the project suggested a photographic filter, and this is a good idea, but if we bought a color filter from a photography shop how could we know that it was working? I thought we might be able to file one and put the filings in a cuvette in solution and place that in a photospectrometer to see if the peak absorbance is 440-490. Or maybe there is an optics reference book with the absorbance of materials?
 
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I'm confused- are you looking for a notch filter (absorbs a waveband) or a pass filter (transmits a waveband)? Either way, why do you have to grind one up to measure the transmittance?

There are many companies that make filters- Omega, Hoya, Chroma, Semrock, Tiffen,... yours is probably a stock item, or close to one.
 
Andy Resnick said:
I'm confused- are you looking for a notch filter (absorbs a waveband) or a pass filter (transmits a waveband)? Either way, why do you have to grind one up to measure the transmittance?
There are many companies that make filters- Omega, Hoya, Chroma, Semrock, Tiffen,... yours is probably a stock item, or close to one.

it would seem he's looking for a low pass filter ... so from a white light source, he wants the blue end filtered out leaving all the rest to pass through.

@vande060 ... how would you know its working? easy, put a blue filter in front of the light coming out if the other filter it should be dark, ie. no blue light present to come through the blue filter

Dave
 
Andy: it sounds like they're looking for a notch filter to remove blue. I'm not sure if a low pass would be sufficient (it depends on whether they want to keep the UV or not).
 
Optical filter sites are very helpful. I just didnt really know the title of what I was looking for. Thanks for the info. I think I am looking for a notch filter. I don't want the blue light to be transmitted from the source, and I'm hoping to find a filter that will absorb it and reduce transmittance. They are pretty expensive though, maybe the photography shop has something to offer.
 
I actually found a list of optical properties for wratten filters(kodak company) in the crc. They are very cheap, and I have some nice quantitative data to go with them. Just in case anyone was interested, I think I'm going to suggest these to the professor.
 

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