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CD Spectroscopy - Dr. Cameron Jones

tsg

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tsg
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Discovery Science Channel showed an episode[#23, Nov 2, 2005] of Australia's "Beyond Tomorrow" last night that featured one Dr. Cameron Jones and his method of detecting biological agents like anthrax with just a CD-ROM drive and some software. The episode summary is here. The idea is that you can use a CD-ROM drive to identify different substances using the laser as a spectroscopy device and matching the signature to a database of different substances.

I am not a biologist (don't play one on TV), but this set off my baloney detector because it sounds too easy, would make him a bunch of money, plays on people's fears, and few would have the knowledge to evaluate it critically. However, if it does work, I could have an application for it if it could be adapted to identify mold. Currently we have to send samples out for testing and it can take a week or more to get results. This could be done on site in under an hour.

Google is short on details other than from Dr. Jones' website, Beyond Tomorrow's story summary (above), and a press release from Swinburne University of Technology in Australia, who I've never heard of.

As much as I would like it to be true, my skepticism is raising alarms. Anybody have any info, perhaps a biologist that can comment on the possiblity of it working?

Thanks.
 
CD players have no spectroscopic potentials. The laser hits a spot, and is reflected as either a hit or a no-hit, giving a binary, digital signal. As pretty as the rainbow 'iridescent effect' is off of the discs, the insides work as black and white.

Besides, I lasers aren't used in spectroscopy, since they are monochromatic, not broad band white light that can be broken into all the colors of the rainbow. CD's probably work on red, or infra red, wavelengths. Like laser pointers.

The claim is totally BS. Was it shown on April Fool's day?
 
casebro said:
CD players have no spectroscopic potentials. The laser hits a spot, and is reflected as either a hit or a no-hit, giving a binary, digital signal. As pretty as the rainbow 'iridescent effect' is off of the discs, the insides work as black and white.

Besides, I lasers aren't used in spectroscopy, since they are monochromatic, not broad band white light that can be broken into all the colors of the rainbow. CD's probably work on red, or infra red, wavelengths. Like laser pointers.
Click to expand...

I may have added "spectroscopy" based on what I thought it was doing. I can't seem to find that word on any of the links I gave originally, so it is probably my misunderstanding.

Apparently, by putting the substance on a CD (I believe a blank one), the way in which the substance scatters the light from the laser is supposed to give them the information they need to identify it.

But your description of how a CD-ROM works is accurate. It either reflects or doesn't, on or off. Could that possibly give them enough information to tell anthrax from talc?
 
I think this link is supposed to explain how it works, though I haven't read it completly. I found in the "Refereed Papers" section of DR. Jones' site.
 
BenK said:
I think this link is supposed to explain how it works, though I haven't read it completly. I found in the "Refereed Papers" section of DR. Jones' site.
Click to expand...

Interesting. Ignorant as I am of nano- anydamnthing, it seems that a CD player can tell you what color blotch is on a cd. After going through the whole staining process, instead of a microscope, use a computer.

The genius of the concept lies in "who woulda thunk it"?
 
Well, CD's use a very small group of wavelengths in the IR band.

It sounds a lot like checking reflectivity based on gram stain reactions.

But, well, it does sound a bit odd.
 
casebro said:
Besides, I lasers aren't used in spectroscopy, since they are monochromatic, not broad band white light that can be broken into all the colors of the rainbow.
Click to expand...

While not applicable to the discussion of using a CD-ROM for spectroscopy, the above statement is not true.

Lasers are frequently used in a large number of aspects of spectroscopy, and you have to be very careful in what you mean by monochromatic. Tunable lasers that use a lasing medium with a broad spectrum gain profile (such as dye lasers) can scan very large wavelength range. There are many other lasers available today that have varying capabilites when it comes to tuning or multiple wavelength emission. And even narrow band lasers that one might colloquially refer to as "monochromatic" have a finite linewidth, and can be tuned over that linewidth using a number of techniques ... probably the most famillliar being a Fabry-Perot etalon. There are times when one wants to differentiate between the absorption and emission of wavelengths that are a fraction of a nanometer apart ...using an etalon is a way of getting a much sharper probe wavelength enabling better resolution, as well as being able to scan the modes.

- Timothy (Optics guy)
 
Just a slight correction: Lasers can be used for spectroscopy, as in photoluminescence spectroscopy, or PL. Take a semiconductor and a laser with a wavelength larger than the semiconductor's bandgap. The laser light is then absorbed by the semiconductor, creating electrons on a higher energetic level. When the electrons fall down to their normal state they emit light. You analyze that light.

For (optical) spectroscopy, you either vary the wavelength of the light going in, or of the light going out. CD players do neither.
 
Timothy said:
There are times when one wants to differentiate between the absorption and emission of wavelengths that are a fraction of a nanometer apart ...using an etalon is a way of getting a much sharper probe wavelength enabling better resolution, as well as being able to scan the modes.

- Timothy (Optics guy)
Click to expand...

Oh, when one needs a 3-meter coherence length, eh?
 
Thanks for the enlightenment. You have put me into a light hearted mood. 'C' ya later.
 
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