Oooo thats super cool to see how the lines show on the defect! Most ppl on youtube only ever show super flat or slightly out of flat things so all you ever see is straight lines or slightly curved lines.
If I was still taking metrology class (30yrs now) I woud ask, b/c I remember the overhead projection concept being brought up like it was a standard setup-killer. That prof was the anchor for the entire mfg college program and it was real easy to grow to hate that ball buster.
What are you using as an exposure media? Parchment paper? It is neat that it works with a glass test piece, but does work with a granite target? A typical mono-chromatic light source shows nothing against a dark target like granite.
Im not sure if this is what I was seeing in the past but it looked like if you put a laser to a really shape focus at the point of reflection It would show the grain of the material on the projected image.
How loud would a sound wave need to be before you started seeing distortion on the surface of the flat? Like, would Surface Acoustic waves disturb the fringe and display patterns similar to Faraday waves in water?
This seems interesting, but I cannot understand what your optical setup is. It appears that your laser is not well collimated, based on the elliptical bright area seen on the screen. I don't understand why where is so much light extending out to the edges of the reflections from the optical flat. In a traditional setup, the monochromatic light source is uniform and diffuse, which gives even illumination of the test optic. With a diode laser source, this can be achieved by cutting a hole in a white ping pong ball that allows the ball to be slipped over the laser. I have tried this with a green laser and have seen this with red diode lasers, but I don't know if the plastic in the ping pong ball would absorb too much 405 nm light. I do not understand what you are doing to zoom in on different areas. Please give a more detailed description of the setup and what you are changing to zoom in.
@@cylosgarage It should work with any type of the laser. But beam should be diverging to enable zoom and bigger surface coverage. I have successful experiments with red laser on my channel.
@@heraldofdisaster3322 I’ve since come up with a theory. Because the laser light is so coherent, it can interfere over longer distances such as the top and bottom of the optical flat. If these surfaces are parallel and the flat is n*λ thick, then they can destructively interfere with the fringes coming from the bottom for a light of wavelength λ. This may explain why some laser wavelengths work but not others. The red for me produced very very faint fringes, but not zero. I think this is also why in schematics of fizeau interferometers the reference flat is wedged on one side, to prevent a superposition of a 3rd wavefront we don’t care about. We don’t have to worry abt this is traditional optical flat use with a sodium or helium light because is it not highly spatially coherent and won’t interfere over such great distances. But I have no idea and have not tested this. Just a thought
@@cylosgarage One option to test you theory about interference between optical flat's surfaces is to point the laser at different angles to check pattern under different path length differences. In my experiments with red laser I observe interference from flat and front surfaces of glass plates in form of concentric circles (because my laser source is diverging one). And those circles always present so I have to filter them out when testing some parts.
