I am considering trying an index matching fluid between my DCG plate (non coated side) and a resin block.
I know glycerin can be used as index matching fluid
Glycerine: 1.473
Glass =1.52
Resin + 1.5 to 1.6
Real expensive optical index fluid = 1.8
Question is glycerin OK enough to use?
Is there a cheap material I can use?
What is the rule of thumb for using index matching fluid
Thoughts?
Glycerin as index matching fluid
Glycerin as index matching fluid
We use mineral spirit for index matching, but I'm not a fan of index matching, so I don't do it a lot.
In terms of the numbers you give, use the Fresnel equations to determine the efficacy of the material. The reflectivity (for normal incidence) is:
R = [ {n(1) - n(2)}/{n(1) + n(2)} ]^2
and the angle of refraction is, of course, Snell's Law:
n(1)*sin(theta-in) = n(2)*sin(theta-ref).
For an air-glass (index ~1.5) interface, the reflectivity for normal incidence is:
R = [(1.0 - 1.5)/(1.0 + 1.5)]^2 = (0.5/2.5)^2 = 0.2^2 = 0.04 (or, 4%)
For your glycerin,
R = [( 1.52 - 1.473)/(1.52 + 1.473)]^2 = (0.016)^2 = 0.0002 (or, 0.02%)
For refraction between the media:
sin(theta-in)/sin(theta-ref) = 1.47/1.52 = 0.96 (ie, the two angles, in and refracted, are almost equal and there's practically no refraction)
I would say this is pretty adequate as an index matching fluid!
In terms of the numbers you give, use the Fresnel equations to determine the efficacy of the material. The reflectivity (for normal incidence) is:
R = [ {n(1) - n(2)}/{n(1) + n(2)} ]^2
and the angle of refraction is, of course, Snell's Law:
n(1)*sin(theta-in) = n(2)*sin(theta-ref).
For an air-glass (index ~1.5) interface, the reflectivity for normal incidence is:
R = [(1.0 - 1.5)/(1.0 + 1.5)]^2 = (0.5/2.5)^2 = 0.2^2 = 0.04 (or, 4%)
For your glycerin,
R = [( 1.52 - 1.473)/(1.52 + 1.473)]^2 = (0.016)^2 = 0.0002 (or, 0.02%)
For refraction between the media:
sin(theta-in)/sin(theta-ref) = 1.47/1.52 = 0.96 (ie, the two angles, in and refracted, are almost equal and there's practically no refraction)
I would say this is pretty adequate as an index matching fluid!
Glycerin as index matching fluid
I guess this discussion should be copied in the wiki!
Dinesh wrote:We use mineral spirit for index matching, but I'm not a fan of index matching, so I don't do it a lot.
In terms of the numbers you give, use the Fresnel equations to determine the efficacy of the material. The reflectivity (for normal incidence) is:
R = [ {n(1) - n(2)}/{n(1) + n(2)} ]^2
and the angle of refraction is, of course, Snell's Law:
n(1)*sin(theta-in) = n(2)*sin(theta-ref).
For an air-glass (index ~1.5) interface, the reflectivity for normal incidence is:
R = [(1.0 - 1.5)/(1.0 + 1.5)]^2 = (0.5/2.5)^2 = 0.2^2 = 0.04 (or, 4%)
For your glycerin,
R = [( 1.52 - 1.473)/(1.52 + 1.473)]^2 = (0.016)^2 = 0.0002 (or, 0.02%)
For refraction between the media:
sin(theta-in)/sin(theta-ref) = 1.47/1.52 = 0.96 (ie, the two angles, in and refracted, are almost equal and there's practically no refraction)
I would say this is pretty adequate as an index matching fluid!