|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
68.6.139.182
In Reply to: RE: CD/ disc scratch repair (not sure if right forum) posted by JaroTheWise on August 05, 2015 at 00:50:33
I'm sure, than, you are aquainted with something called an 'optical flat'. We used it to maintain FLATNESS of certain tooling. Putting the flat on a surface and illuminating with a monochromatic light produced an interference pattern. From this you could determine flatness of the inspected object.
The reason I bring this up? I'll bet $$ that a CD is 'specified' as having a certain surface flatness.
The lens which focuses on the 'pits' has an extremely SHORT depth of field which renders a few of the explanations I've heard for some 'digital problems' absolutely moot.
Now that I think about it, I wish I could still get at some of the goodies I USED to have routine access to. A Macbeth densitometer? Surface Profiler? Optical flat? Even a good 'scope, both micro and oscillo.
Those were the days!
Too much is never enough
Follow Ups:
I have always been surprised at how well a CD laser can read despite scratching - a level of scratching that would make a telescopic lens or mirror a complete mess.
I also use those cd lens cleaning discs often enough living here in AZ with all the dust. I noticed even before it starts to completely fail then it starts into skipping and pauses etc
JaroTheWise
Objects too far OUT of the focal plane will NOT be seen.
Same reason the dust on your camera lens GENERALLY doesn't interfere with taking a picture.
That's ANOTHER good reason not to abrade / polish (overall) the surface of your CDs. Making that coating thinner brings closer the time when ANY minor imperfection enters the focal plane.
Too much is never enough
yes we used a flat with an interference pattern to measure consistency of the concavity - that it would reveal inconsistency causing lack of sameness in the pattern. I recall my piece turned out well, luckily - but also recall how the method was so precise that you could place your fingertips on the glass for a few seconds and the "bumps" in the pattern would appear where the heat from the fingers caused the surface to expand
Sounds like you should get back some of the instrumentation or express it in building some items in order to express your interest
I did that optics stuff 30 years ago so it has been awhile for me too
JaroTheWise
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: