Roadie's Diffraction Grating (shearing?) Interferometer

[hla27b]

excellent demo thanks a bunch

now could it be the lenses' imperfections that create the interference or maybe just your fingerprints lol

[RoadRunnerLaser]

Not imperfections or fingerprints.

The "lens" is a form of beam-splitter and it's the interaction between the multiple wavefronts which are causing the interference patterns.

The real key to this setup seems to be that the light entering the splitter is not a thin collimated beam, but a distinct cone and so takes a number of different routes through the system depending upon the angle of incidence at any given point.

[foxandthehen]

lol, I often think this when seeing these sorts of demo's, but most of the time it probably is interference. apart from when I see people on youtube using normal household mirror of course!

[eternetytenrete]

Looks like a fingerprint or brain coral. : )

[RoadRunnerLaser]

It also looks like the visual disturbances I get at the start of a migraine.

[ltc1290]

What was the grating density?

[RoadRunnerLaser]

To be honest, I don't know. I ripped it out of an old Philips LaserDisc player along with a HeNe and a pile of other interesting optics.

It's the kind of optic device which spreads a single incoming beam into a fan of beams (in one axis).

[foxandthehen]

maybe you could adapt "young's" to find out.

[dhaffner101]

Very cool demonstration!!

[antediluvia007]

I agree. :)

[LittleMickyFingers]

Good stuff! My own knowledge of Lasers is confined to the instruments I use in the construction industry and some of this information is a little beyond me, but, I must admit I am tempted to get some lenses and give it a go!

[RoadRunnerLaser]

It's amazing the number of different uses to which lasers can be applied.The first uses that come to mind for construction include LIDAR (laser-distance measurement), line-guides (you don't get much straighter than a laser-beam) and the good old 'pointer'. "Oy, Paddy, grab THAT with the hook and swing it over to THERE !"

Interferometry can also be used in a 'strain-gauge' type of application too - Which is what's happening in this video.

Did you have other uses for them ?

[LittleMickyFingers]

Yep, I have a sophisticated self-leveling laser that allows me to create datum lines over 150 metres in length. It has a set of prisms to allow me to project angles of deviation and perfect right angles to allow for better construction. It also has a remote control which allows me to send calibration data to the unit whilst I am somewhere else. Superb bit of kit!

[RoadRunnerLaser]

I've seen the domestic 'Black and Decker' version of the self-levelling line, but the one you describe sounds excellent.

Those 'lines' are made by passing the beam through a thin glass cylinder, by the way. Shine a laser-pointer through a wine-glass stem and you can achieve much the same effect. Not useful for construction, but just as a demonstration of how to create the effect.