Lens transmission measured with a DIY integrating sphere

[ulf]

The first results from the DIY integrating sphere measurements is ready.

Tested Lens: EL-NIKKOR 80/5.6 old metal type.

Measured valid spectral range ca 360nm - 380nm

 

After suitable stabilisation times and calibrations all was stable enough for measuring.

 

The actual lens measurement graph: Green (0% and 100% graphs kept for reference)

All measurements except the wavelength verification are averages of 50 exposures each 282ms long.

 

I consider the results valid between 260nm and 280nm.

 

Jonathan (JMC) have kindly allowed me to show the result he got when measuring his EL-NIKKOR 80/5.6 old metal type lens.

 

When I compare Jonathan's result with mine, from our two different lenses, between 260nm and 280nm, there are an amplitude difference or offset of between 3.5% and 4.5%.

His values are the high ones.

 

The difference can be a combination of more scattered stray light added to the spectrometer's detector when Jonathans wide-band light source was used and the fact that my lens has a tiny bit of barely visible haze.

The scattered stray light result in the offset that can be seen in Jonathans graph, below 330nm.

This phenomenon is typical for our type of array spectrometers with some types of light-sources.

 

We are amazed that our results are that similar and will both continue to try to improve the methods further.

 

Parameters tested and verified before and after the lens measurement:

Wavelengths better than 0.05nm. Red (not amplitude offset corrected) The correct wavelength for this peak is 365.015nm.

 

Zero offset between 360nm and 380nm, well below 0.2%. Brown.

 

Light source better than 1% between 360nm and 380nm. Blue.

 

The convoy torch has a 10nm narrow peak. This reduces the internal reflections and false offsets substantially

 

 

 

I will explore the possibility of more narrow-band measurements, using several different power-LEDs, with different wavelength peaks, as light-source.

Another of my DIY projects is in progress where I have gathered some different LEDs that I hope to be able to use.

 

With some luck it will be possible for me to create a combined lens-transmission by stitching together several results.

[Andrea B.]

Good work, Ulf! And thank you.

 

The convoy torch has a 10nm narrow peak.

Good to see a confirmation of this.