I was wondering if anyone has tried the following micrometer for measuring DCG layer thickness:
http://www.harborfreight.com/digital-mi ... 98485.html
They say on the website it has a resolution of 0.0001 inch, but on the package it says 0.00005. (0.0001 inch would be 2.54 microns) The price is $34.99, but occasionally it goes on sale. Very high precision wouldn't be needed, but I would like to know if my coatings are around 15, 20, 25 microns, etc.
harbor freight micrometer
harbor freight micrometer
I use this type at work and I bring in plates once in a while to measure.
One thing to keep in mind Joe, there are types in which when you rotate the micrometer the tip also rotates. This is not the best thing rather the prefered type is the tip that simply goes up and down.
Good price though,
Good Luck
Tony
One thing to keep in mind Joe, there are types in which when you rotate the micrometer the tip also rotates. This is not the best thing rather the prefered type is the tip that simply goes up and down.
Good price though,
Good Luck
Tony
harbor freight micrometer
Thanks Tony. It will still probably be a destructive method, though; measure the glass/gelatin, scrape off the gelatin, measure at that same spot again, and subtract for the glass.
harbor freight micrometer
I thought we sorted out an optical method to measure this? Am I mistaken?
harbor freight micrometer
Using a spectroscope requires that you coat a mirror I believe.
Am I mistaken?
Am I mistaken?
harbor freight micrometer
Strictly you don't need to coat a mirror, you'll get interference from the reflections at the air->gelatin and gelatin->glass interfaces. The interference will cause dips in the reflection spectrum at (approximately) equally spaced wavelengths. From how many dips you see per wavelength interval you can calculate the thickness. At my previous job I wrote software to fit a theoretical spectrum to a measured one to measure antireflection coating thicknesses this way. It also worked well for the emulsions. Because the difference in refractive index between glass and gelatin is very small, the reflection at the second interface will vary from almost nothing to a couple of tenths of a %. So the dips are shallow. I don't know if you'll be able to see them by eye. For a free standing layer they'll be very easy to see.
harbor freight micrometer
I guess I recalled this post.
http://holographyforum.org/phpBB2/viewt ... ess#p41567
Have you tryed it with glass Thieu?
http://holographyforum.org/phpBB2/viewt ... ess#p41567
Have you tryed it with glass Thieu?
harbor freight micrometer
This morning I tried both techniques. For the first type I looked at the reflection of the sun on a small portion of the plate through a grating. I could not discern the dips in the spectrum. For the other type I reflected the unfocused beam of the blue diode onto a screen. It also generates a reflection with a slow variation of the entrance/exit angles. No luck there either. I guess the contrast is just too low. I used photoframe glass with a couple of um's of knox (finally made some plates Joe ) I'm afraid the conclusion has to be that the shallow dips can only be seen with a digital spectrometer like the one I used at work. It worked well there with the same gelatin on glass coatings.
Btw, if you use mold coating, you can use rainex on parts of the plate that are normally coated. Then the layer can easily be pealed off. This certainly works with the spectral technique, I use it as a demo for students in a wave optics class with mica plates. The dips show up really well in that case.
Btw, if you use mold coating, you can use rainex on parts of the plate that are normally coated. Then the layer can easily be pealed off. This certainly works with the spectral technique, I use it as a demo for students in a wave optics class with mica plates. The dips show up really well in that case.
harbor freight micrometer
What mica do you use? I need some optical grade mica about 50mm in diameter and a mm or so thick.Thieu wrote:This certainly works with the spectral technique, I use it as a demo for students in a wave optics class with mica plates. The dips show up really well in that case.