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[PIC HEAVY] Got a Monochromator!

icecruncher

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Analog implies electronics are involved, where there are none here. A more appropriate term might be "mechanical."
Thank you.

Simplex/Kaba 5 button locks are another example. People think they have some kind of electronic control, when in actuality it's just a very sophisticated mechanical device.

in any case its a very cool device.
 



The Lightning Stalker

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Probably the most sophisticated mechanical device I've ever seen are the old IBM Selectric™ typewriters.
Just try fixing one of those.
 
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Oh. Bloom, there isn't a PCM on this one =p Just another slit. I was thinking about adding a PCM though. I don't think all monochromators are designed that way. At least not this one!
Then what is reading the light??

There has to be an element beyond the exit slit that reads if light is present, and sends a signal to the meter.

The PCM is the only electrical part of this device. At least in the Verity. The rest is an entrance slit, bounce mirror, michrometer-controlled mirrored grating, two more bounce mirrors, exit slit, then the PCM.

Your PCM functions like a photodiode. All it does is send a signal to the meter. If light makes its way through when the grating is tuned to allow 532nm, then the light is 532nm.

I would be very interested in how this works if it is not a PCM..
 
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Wolfman29

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Thanks for the good discussion, guys :D

Bloom -
This is everything in the Verity up to the output slit. Right now, I still need to optimize the slit sizes to make sure that the only light that gets through is the light I want to get through. However, I have simply been pointing my defocused laser at the entrance slit and adjusting the dial until I see something come out! Because this is a high-intensity intended monochromator, it can take the power (I haven't tried the 445nm yet, still worried about that), and so the intensity on the output slit is high enough that I can simply just adjust until I get light through. When I get light through, that has the be the wavelength, right?

I did buy a PCM from Sam but I have yet to hook it up. That may be my weekend project.
 
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I would assume it's your wavelength right, based on your DPSS readings.

Mine has no exiting of light, and I use a weak source as to not burn out the PCM. So no hands on experience there.
 
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Wolfman said:
"When I get light through, that has the be the wavelength, right?"
Yes, it must be your wavelength. As displayed in your DPSS testing, only one wavelength could be exiting, your wavelength you are testing.
 

Cyparagon

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(I haven't tried the 445nm yet, still worried about that)
There's another reason to use a fiber. You can point the fiber at the dot instead.

I have simply been pointing my defocused laser at the entrance slit and adjusting the dial until I see something come out!
Well yeah. Is there any other way to do it? :confused:

Then what is reading the light?
The point of a monochrometer is to isolate a wavelength. Why "is reading the light" required for this? I can certainly see why it would be included in some models, but I don't think it is an integral part of the design.
 
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Not saying "reading the light" as in your display on a spectrometer.

I am saying a photodiode, or similar element, that sends a signal to the meter telling you that light is present. That is how mine works. The internals separate the light, and the PCM element sends a signal to a voltmeter that spikes when there is light reaching the PCM. The mirrors, and grating, are to split up the light to match up with the micrhometer's reading. So when I turn the meter to 532, 532nm light should make it through the exit slit, hitting the PCM, causing the signal to be sent.

This is the basic layout of my monochromator.
 

Wolfman29

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Ah, that's what you mean. I just have a white light at the output that I can see the emission. I should probably get a setup like yours though so I can narrow the slits even further and then I wouldn't have to shine the laser through the slit directly.
 
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I don't have an output. There's an input slit, light goes in, hits a mirror, then the grating, two more mirrors, then the exit slit. That exit slid feeds the light to the PCM, and that PCM sends the signal to the meter.
 

Wolfman29

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See, I figure that as long as the light is intense enough that it's still visible, a PCM is just as good as my eyes =p
 

The Lightning Stalker

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Not a light output. That type has a voltage output to indicate the intensity of the light. It uses a PMT
which can detect individual photons, which is why it's called a photon counter. A PMT is way more
sensitive than a photodiode. It's more than just a light separator, more of an astronomy/physics
instrument.
 
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Not a light output. That type has a voltage output to indicate the intensity of the light. It uses a PMT
which can detect individual photons, which is why it's called a photon counter. A PMT is way more
sensitive than a photodiode. It's more than just a light separator, more of an astronomy/physics
instrument.
Exactly. I use the photodiode as an analogy as it does basically the same thing. It cannot tell what wavelength the light is, just whether it's there or not.

It sends a signal to a voltmeter externally, and I turn a pot to send more/less power to the PMT (been saying it wrong all along..), to change the sensitivity. Once it it sensitive enough to read the light, a signal is sent to the meter, and the meter pings when the micrometer is tuned to the current wavelength.

:)
 




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