Aug 10, 2010.

George, needless to say it is very difficult to make a generic comparison of surface quality standards that are used for any high power Optical system to other optical components. But I will give it my best shot. In response to your questions:

For our application we use the following scratch/dig designations, 30/10 for 1 omega light optics in the system and 20/10 or better for 3 omega optics in the system. Number 30 scratch =30microns in width and a 20 scratch is 20 microns in width. The maximum length of a scratch is determined by the sum of the scratch number times the ratio of the length to the diameter. Of the element or appropriate clear aperture shall not exceed one half the width of the scratch number. As a 30 scratch could be determined not to exceed 15 microns in length.

The definition of a Dig is any defect that is round in nature. Dig numbers are the actual diameters of defects allowed ,specified in units of 1/100mm. The maximum allowed dig is one per each 20mm diameter. However a size 10 Dig needs a minimum of 1mm separation and also requires scattering measurements.

When we refer to scratch/dig that is the Mil Spec designation. However the optical design may require that these specifications be tighter depending on the application. We do not use Clinical grading, The Mil. Standard spec does not correspond to any of  your listed grades. The sheer number of defects in the clinical grades  would be cause for rejection. Just to give you an idea what were looking for in our optics (mind you they are 440mmx440mmx10mmthick) we allow a total of 12 defects between the two surfaces (clear aperture of ~400mm square). Allowed one scratch max length 50mm.

I went thru all of the data that you sent and best I can tell the equivalent  Mil Standard Spec for Scratch Dig is between 30/10 and or 20/10.

The bottom line is that these defects due to the size and nature would not be acceptable for use on NIF or any other laser that would require defect free optics. These defects would work like a lens within the lens, who knows where the focal point (both efl and bfl) would be. Since the material for these lenses (if I understand it right) is flexible you might even get a cylindrical lens effect.

So in my opinion these parts would not be acceptable for any high precision system.

If you need any additional information let me know.

Sincerely, Dan

Dan Walmer,

Master Optician,

Senior Engineering Associate,

National Ignition Facility

Lawrence Livermore National Labs