Surface Roughness

Calculating BTDF from Window Surface Roughness (ABSTRACT)

ABSTRACT: Stover, et. al., show that scatter in transmission through a window may be calculated from surface roughness in a manner similar to calculating BRDF from roughness for a reflecting surface.

In Situ Surface Roughness Measurement (ABSTRACT)

ABSTRACT: A note describing initial measurements made with the MicroFinish Topographer (MFT) directly on large optical surfaces thereby eliminating the need for making replicas and making secondary measurements.

MicroFinish Topographer: Surface Finish Metrology for Large and Small Optics (ABSTRACT)

ABSTRACT: Description of the MicroFinish Topographer (MFT) and why its unique mechanical design largely removes the need for vibration isolation. The paper also describes how the MFT is used for making surface roughness measurements on large and small optics as well as its usefulness for on-machine measurement due to its small size and light weight.

Optical Surface Specification using the Structure Function (ABSTRACT)

ABSTRACT: A tutorial on use of the structure function (SF) as a specification to limit the effects of mid-spatial frequency roughness. The paper points out that the SF units of measurement are familiar to opticians and optical engineers and that it is easy to calculate the SF without making ambiguous assumptions as opposed to the use of Power Spectral Density function (PSD).

Specifications: Figure and Finish are not Enough (ABSTRACT)

ABSTRACT: A paper that shows why simply specifying figure and rms surface roughness is not enough information to assure a finished optic will perform as expected. Mid-spatial frequency roughness must also be specified. There are examples using the PSM to show the effects of mid-spatial frequency roughness, and examples of using the structure function to characterize mid-spatial frequency roughness.

Super-Smooth Optical Fabrication Controlling High Spatial Frequency Surface Irregularity (ABSTRACT)

ABSTRACT: A paper by Del Hoyo, et. al., showing how the MicroFinish Topographer (MFT) was used for in process control assessment of the removal of high spatial frequency polishing errors during polishing as a function of type of polishing compound and polishing pad. The MFT was particularly useful for determining when a surface was fully polished out, that is, had no defects left from previous steps in the lapping and polishing process.

Use of the Surface PSD to Investigate Near Specular Scatter from Smooth Surfaces (ABSTRACT)

ABSTRACT: A paper by Talabaly, et. al., showing that a low magnification objective on the MicroFinish Topographer (MFT) can measure surface roughness in a spatial frequency domain that is so close to specular that it is not possible to make a similar measurement with a scatterometer. This makes it possible to predict a valid near specular BRDF that is functionally not measureable, particularly if the substrate material scatters.

Case Studies & Testimonials

Why is proper alignment so important?

Here is a case of a very happy customer due to better optics.

A few days ago an astronomer friend of mine commented that he had gotten the optics of his telescope improved and the improvement reduced the time it took to get data by a factor of 3. For an astronomer this is a dramatic improvement since observing time on large telescopes can cost thousands of dollars an hour.

My friend did not say how the optics had been improved, but the important point is that better optics, whether due to figure errors, mounting or alignment mean more productive optics. I generally think of better optics as a better product leaving the manufacturing facility without thinking about how much the better optics mean to the productivity of the customer.