metrology myths
Myths of Modern Metrology
Does your metrology measure up?
Myth #1: Buying additional standard interferometers substantially increases your metrology capabilities.
The Reality:
Buying more of the same gives you... more of the same. 30-40% of the optics manufactured today cannot be measured over the full aperture with standard interferometers. SSI® Metrology systems are the only tools that can measure large optics, steep optics and even aspheric optics, with standard transmission elements, over the full aperture.
Myth #2: If a subaperture measurement looks good, the entire part will be in spec.
The Reality:
What you see is what you get. A good subaperture measurement truly only indicates the surface of that particular subaperture is good. Even subapertures that cover 70% of the lens surface can give you false confidence in your manufacturing quality. With SSI® Metrology systems, you can see the whole surface, every time.
Myth #3: If measurement says it’s good, the part is good.
The Reality:
Sometimes the difference between what you WANT to measure and what you are ACTUALLY measuring is significant. Accounting for and correcting transmission element errors is critical but the processes are difficult, slow and are rarely used. SSI® Metrology systems automatically detect and correct systematic errors, including reference wave, distortion, and retrace errors.
Myth #4: Pixel Scale = Resolution
The Reality:
Though the theoretical limit states that features can be measured as small as two pixels in width, these measurements suffer from attenuation inherent in non-ideal instrumentation. Such issues can be corrected utilizing precision metrology tools that apply apeture stitching algorithms to improve the accuracy and precision of the final measurement.View our selection of technical papers on spatial resolution.
