Scratch-Dig Information

Scratch-Dig Information

Scratch /Dig Optical Surface Specifications

A surface imperfection, such as a scratch and dig, can reduce the quality of high-precision optics. Scratch and dig specifications can be visual, although this only serves the purpose of determining quality on a cosmetic basis. More precise dig and scratch specifications are typically necessary to determine the possible impact of a dig/scratch on overall performance.

Until fairly recently, there was no standardized method of quantifying the size of a scratch-dig present on a surface, and manufacturing companies and others had no choice but to implement a highly subjective visual standard. It wasn't until the 1980s when more precise scratch dig specifications based on the actual measurement of the imperfection were developed.

Today, these dig scratch standards are used almost universally throughout the optics industry. They give manufactures a more effective way to gauge the possible impact of scratch/dig on part performance.

PR Hoffman Lapping and Polishing Machines: Simplifying the Scratch and Dig Removal Process

PR Hoffman offers a complete line of lapping and polishing machines that facilitate the process of dig and scratch removal. Our machines are backed by more than 70 years of innovation that has helped us earn worldwide recognition as an industry leader.

We partner with you to solve your processing needs, understanding your success is the key to our success. Our focus on adhering to the highest standards for quality and service ensures your lapping and polishing machine will help you meet and even exceed your own stringent quality standards.

You can learn more about optics surface quality specifications by reading below:

This document defines surface quality on optical components per MIL-PRF-13830B.


View Mil Spec


  • SCRATCH: Any marking or tearing of the part surface.
  • DIG: A small rough spot on the part surface similar to a pit in appearance. A bubble is considered a dig.
  • SLEEK SCRATCH: A hairline scratch.
  • CRUSH or RUB SCRATCH: A surface scratch or a series of small scratches.

Please visit one of the Optical Industry leaders for more detailed information on this topic:

Feel free to contact us or call 717-243-9900 for more information or to get concise answers to your sapphire substrate questions.


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