Seiko 1.67 MR-10

[Alvaro Cordova]

I have been trying to find out as much information as I can about this material. They say the index is 1.67, but was it tested at Nd = 589nm or was it some other wavelength? I have just found out that trivex was measured at 546nm instead of Nd. I heard through some of teachers that Seiko does the same thing. I tried calling them, but no one knows anything.

Trivex info

[Darryl Meister]

The refractive index of MR-10 is often stated using international and Japanese standards (at the mercury e-line), which puts it at 1.668 (1.67 to two decimal places). Using US standards (at the helium d-line), I believe the index is 1.661.

To the best of my knowledge, the refractive index of Trivex (using the helium d-line) varies from 1.525 to 1.529 (1.53 to two decimal places), depending upon the specific recipe.

[OPTIDONN]

Just a question. Is the sodium D line used to measure the refractive index of lenses anymore? I read some place that that was the US standard.

[Darryl Meister]

Is the sodium D line used to measure the refractive index of lenses anymore?

Nope. Though it's pretty close to the helium d-line. Helium d is used now because it is easier to isolate, I believe.

[OPTIDONN]

Thanks!! Good to know
:cheers:

[Alvaro Cordova]

Thank for the info Darryl. Do you know where I can get this info myself? I never seem to able to locate it. I think this stuff is important because standardization of indices is the only way to determine if something truly is "high" or "low" or whatever. It compares apples to apples instead of peaches to nectarines.

[Darryl Meister]

OptiCampus Material Chart

[Alvaro Cordova]

Sorry, I meant where are standards listed. I imagine it would be ANSI or ISO, but you have to pay to get a document. Would you happen to know when they switched from sodium to helium?

[Darryl Meister]

I guess I'm not certain of what you're specifically asking. Reference wavelengths are generally specified in national and international standards (e.g., ANSI, ISO, and so on), but only after the local optical industries have agreed to them. That is to say, an organization like ANSI isn't going to specify a reference wavelength that isn't already widely accepted in the US. Off the top of my head, I don't recall when the switch was made to the helium d-line, but I do know that it was at least 20 years ago (the ANSI Z80.1-1987 Standard used the helium d-line, for instance).

[Alvaro Cordova]

You answered my question (it is in fact the ISO or ANSI that specify the reference wavelengths). I was just wondering because I find this interesting and useful. It's important to be able to make valid comparisons.

Thanks again.