Isn't this beautiful.

[colinbm]

Isn't this beautiful.

[Andy Perrin]

Yes! Did you run your little spectrometer gadget on it and see if the peaks match?

[colinbm]

3 minutes ago, Andy Perrin said:

Yes! Did you run your little spectrometer gadget on it and see if the peaks match?

Thanks Andy
Yep & so does this one....
 

[colinbm]

I got the UVC transmission grating, so I can test a Mono Converted camera, soon.

[Stefano]

Did you use a lens? You could also put a slit in front of the sensor with the diffraction grating behind it, and directly project the light onto the sensor.

[colinbm]

@Stefano Could you read the caption & labels on the photo again please.

[Stefano]

Yes sorry, I didn't fully read them.

[Lou Jost]

Colin, what is the "0 degrees" aluminum strip? Is it the origin of the x-axis?

 

Is the faint green light just to the right of the aluminum strip a spectral line or just an edge of the aluminum bar?

 

If I am interpreting this correctly, I don't see any UV-B and UV-C peaks. I would have expected them to show up.

[colinbm]

@Lou Jost I got this UVC diffraction grating because I am looking at a Mono converted camera soon.
I have tried out the setup with my Full Spectrum camera.
The 0 deg is the origin of the X-axis.
Their are many ways to use a diffraction grating, some use a slit to get a narrow line of light.
I have used in the past needles to reflect the light back to the grating, it works the same as a slit, but the light can be on the same side at the grating & the camera.

Unfortunately needles don't reflect all of UVC, I have some special UVC reflective Aluminium, so I folded one edge to give a nice round surface less then 1mm dia.
The UV B & C should be blocked by the CFA & perhaps the sensors cover glass ?
Looking at these colours that are not emission lines, from left to right.
At the extreme right & left is the black background which is an Acktar Metal Velvet from Edmund Optics....
https://www.edmundoptics.com.au/p/metal-velvet-adhesive-foil-sheet-200-x-300mm/30499/

Left, Black, Acktar Metal velvet.
Violet, black cardboard to support the UVC Aluminium.
White, UVC Aluminium strip.
Dark green, unknown ?
Black, should be the Acktar background.
Two dark blue, unknown ?
Violet/magenta, 365nm emission line.
Dark blue, unknown ?
Blue/violet, 405nm emission line.
Black nearly, could be the Acktar background ?
Blue, 436nm emission line.

Dark green, unknown ?
Green, 546nm emission line.
Black, Acktar background.
Yellow, 579nm emission line.
Right, Black, Acktar background.

[Andy Perrin]

1 hour ago, Lou Jost said:

Colin, what is the "0 degrees" aluminum strip? Is it the origin of the x-axis?

 

Is the faint green light just to the right of the aluminum strip a spectral line or just an edge of the aluminum bar?

 

If I am interpreting this correctly, I don't see any UV-B and UV-C peaks. I would have expected them to show up.

Lou, if the visible light ones are properly exposed, the UV-B and UV-C peaks may be too dim because the camera's sensitivity is orders of magnitude smaller there, in addition to what Colin said about CFA and cover glass attenuation.

[Lou Jost]

Thanks Colin for the very clear reply. I wonder if the broad dark blue and purple bands to the left of the 365nm line are actually the blurred 254nm and 313nm lines? Maybe the UV 105 is not parfocal between UV-C, UV-B, and UV-A ? Though the sharpness of the edges of those bands may be evidence against my idea....You could test this by refocusing to see if you can get those bands to focus into lines.

[Lou Jost]

7 hours ago, Andy Perrin said:

Lou, if the visible light ones are properly exposed, the UV-B and UV-C peaks may be too dim because the camera's sensitivity is orders of magnitude smaller there, in addition to what Colin said about CFA and cover glass attenuation.

Yes, that may be, but the presence of the dark blue and purple bands to the left of the 365nm line argues that the camera is sensitive in those regions. I think there is some kind of defocusing issue affecting those UV-B and UV-C lines; see my response above.

[colinbm]

@Lou Jost It is late in the evening now, I'll have a play with the focus in the morning.
I'll also try some other UVC tube lights I have.
 

[colinbm]

Ha Ha, I just woke from my slumber & I wonder if that black cardboard that looks violet is putting out its broad spectrum from the grating ??
More in the morning.

 

[Lou Jost]

I wonder if the faint dark green broad band is the defocused 185nm line?

 

Edit: No, it looks more like an internal reflection, since the border is not straight.

[colinbm]

I have rearranged the set-up & I am now using a 0.9mm Aluminium wire to reflect the UV light off & into the grating. lens & camera.
Also I have separated the wire from the background by about 400mm.
This has stopped the majority of stray colours, The only stray light colour must be coming from the black cardboard that I made to hold the grating in a filter ring.
I'll try some black aluminium sheet ?
The Full Spectrum Sigma fp is not sensitive enough the 'see' UV below 365nm from 8w Mercury Vapour Tube lights.
But the camera is able to 'see' the light from higher wattage UV A & B LED lights, down to 310nm as shown by the diffraction grating.
Here is a new set of photos with better exposure & processing.

 

[Lou Jost]

Big improvement in cleanliness!

 

 

[colinbm]

With a less then 1 sec exposure I can photograph with this Chinese 310nm LED of Irradiance of 40uW/cm2 @ 380mm.

[colinbm]

This is an interesting spectrum of Raymond's 310nm LED with an irradiance of 166um/cm2 at 380mm.
I don't understand the second & third colours ?


 

 

 

[Stefano]

Two questions:

- how are you calculating wavelengths when you don't have known references (like mercury lines)? For example in you LED spectrum. The relationship between wavelength and displacement is almost linear for short wavelengths, but not exactly linear;

- do you have any clue about the 330 nm peak in your 310 nm LED?

[colinbm]

Chinese 340nm LED with an irradiance of 1.5mW/cm2 at 380mm.
 

[colinbm]

A 365nm LED with an irradiance of 8mW/cm2 at 380mm.

[colinbm]

@Stefano I am trying to match the spectrums with the Mercury Emission Lines.
Data is from my Spectroscope.
All these photos that are taken on the same day are of the same size & setup so they can be measured between each other.
There seems to be some drift in the LEDs measurements from when I labelled them & now, so I will have to double check everything & make small changes over the next few days.
I need to make a scale of the distances of the wavelengths from the 0 degree line out to 500nm which is the upper limit of this Diffraction Grating. the lower limit is 250nm.
But the scale will be dependant on accurate distances from the sensor to the grating & reflection wire.

[Stefano]

Why the upper limit is 500 nm? You saw longer wavelengths than that.

[colinbm]

That is what is in the specifications...
https://www.edmundoptics.com.au/p/300-groovesmm-25mm-sq-uv-transmission-grating-beamsplitter/28226/