Measure Laser Wavelength with a CD and a Tape Measure

Obviously the wavelength of a laser can’t be measured with a scale as large as that of a carpenter’s tape measure. At least not directly and that’s where a Compact Disc comes in. [Styropyro] uses a CD as a diffraction grating which results in an optical pattern large enough to measure.

A diffraction grating splits a beam of light up into multiple beams whose position is determined by both the wavelength of the light and the properties of the grating. Since we don’t know the properties of the grating (the CD) to start, [Styropyro] uses a green laser as reference. This works for a couple of reasons; the green laser’s properties don’t change with heat and it’s wavelength is already known.

It’s all about the triangles. Well, really it’s all about the math and the math is all about the triangles. For those that don’t rock out on special characters [Styropyro] does a great job of not only explaining what each symbol stands for, but applying it (on camera in video below) to the control experiment. Measure the sides of the triangle, then use simple trigonometry to determine the slit distance of the CD. This was the one missing datum that he turns around and uses to measure and determine his unknown laser wavelength.

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RGV laser

[Carl] sure has come a long way with laser modifications, now introducing his portable RGV Full Colour Laser. Although it feels just like yesterday when he showed us his green spiro and his Lego diffraction grating projector.

But enough of the past, the RGV laser is built using a White Fusion Mixing Kit and his own Full Colour Driver Extension. We couldn’t find any circuit diagrams or code to build your own at the moment, but it appears fairly straight forward and you can always take a look at [c4r0’s] Colour Laser.

Hackaday links: Sunday January 24

Everyone Remembers Free day right? [The Ideanator’s] Bus Pirate came in such a nice red box – he decided to make it his permanent case.

[Chico] is in the middle of making a CNC, but decided to make some music with the steppers in the mean time.

What looks like an old wooden box is actually [Ludvig’s] super sweet retro arcade cabinet. Complete with a giant emergency stop red button.

Who says Legos are dead? [Carl] used them to create a simple and cheap diffraction grating projector. Including video!

[Torchris] used an Ethernet shield exactly as it was designed, sending data over Ethernet. Still a nice hack for those needing help working with Ethernet shields and Arduino.

Finally [Robert] let us know about a friends Arduino Binary Clock. But we think his elegant use of tape and a sand blaster to engrave glass is cooler.