GR Metrology

What is an optical comparator?

An optical comparator is a measurement tool used to inspect and measure the dimensions of small manufactured parts. Images of the part are magnified using illumination sources, lenses and mirrors to make the 2-D measurement. The magnified 2-D image is projected on a screen to assess if the parts dimensions and geometry are within specifications.



In a horizontal optical comparator model, light travels horizontally across the stage. This model works well with parts that are held in a fixed location such as screws, castings or transmission shafts. In a vertical optical comparator model, light travels vertically. This model works well with parts that are flat such as gaskets.

There are three different measuring processes. The simplest way is to have an instrument over the silhouette of the image. Another way is to have various points of the silhouette line up with the center point of the screen and measure how far the stage moved to reach those points. The last measuring process involves a software that analyzes the image.

Optical comparators provide more information than basic length and width dimensions. They detect scratches, indentations and many other surface defects. The non-contact method of measuring is popular in the scientific, automotive, aerospace, defense and other industrial industries. When only light touches the part, there’s less room for human error.

This equipment has been used for over five decades and remains cost effective. It is very versatile, easy to use and decreases inspection time. If you’re thinking about investing in an optical comparator, contact us! We are a leading distributor for over 25 manufacturers.




What is an optical comparator

Optical comparator market

Optical comparator calibration



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