Tag Archives: optical comparator

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.

 

 

Sources:

What is an optical comparator

Optical comparator market

Optical comparator calibration

The Battle of the Visual Measurement Systems

Visual measurement systems have a wide variety of application for numerous industries. At Grand Rapids Metrology, we offer two premier systems: optical comparators and vision systems (also known as video measurement systems). With similar capabilities, these systems are often seen as key players in an age-old battle. Today, we break down each system and take a closer look at the comparison of their abilities to help you discover which visual measurement system is best for your specific needs!

The optical comparator originated back in 1920 and showed great potential when it came to 2-dimensional measurement capabilities. Over 96 years since its creation, the optical comparator has been upgraded but those improvements seemed to have plateaued with no further possible renovations in sight. The optical comparator is an instrument used to visually measure X, Y, and Z axis of a small objects against prescribed limits using magnification. In older optical comparator models, measurements were required to be taken manually by an operator, however more contemporary models use an optical edge detection to identify the edges of an object for enhanced accuracy and quicker measurement results. The benefits of using a measurement system like an optical comparator have been apparent for many years; these systems do not require PC based software, they’re relatively easy to operate, and they’re one of the less expensive visual measurement system options.


Very similar to an optical comparator, a vision system is a machine that enables a computing device to inspect, measure, evaluate, and identify still or moving objects. Unlike the optical comparator, these machines use automated inspection. Many users view vision systems as a complete upgrade of the optical comparator and for good reason. The speed and efficiency of vision systems is much greater as well as an accuracy that is twice that of an optical comparator (Approximately 0.0005” on an optical comparator compared to 0.0002” of a vision system).  Likewise, these systems measure using zoom optics which constructs much better lighting and utilizes multiple sensors for a clear resulting image. Vision systems, like optical comparators, are also completely customizable based on application. Adversely, a strong advantage of optical comparators is that is does not require PC-based software whereas vision systems do depend upon PC software. Most available software’s, however, are user intuitive and easy to operate.


Although these systems are similar in the basic purposes of measurement, there are crucial differences that may make an optical comparator, more so than a vision system, the optimal choice a certain scenarios and vice versa. First, an optical comparator does not require a trained or certified operator, but some vision systems do require such trained operators. The dimensional capabilities of an optical comparator are 2D and 2 ½D for that of a vision system. As stated before, the accuracy of an optical comparator is approximately 0.0005” while a vision systems capabilities are double that at approximately 0.0002”. The differences continue when examining contact measurement and CAD/DXF compatibility, for contact measurement is optional for visions systems but not optical comparators and visions systems are compatible with CAD/DXF but again, optical comparators are not.

Purchasing a visual measurement system, whether it be an optical comparator, a vision system, or another device, is a major investment and the available options should be investigated carefully. On a budget, but still need to perform quick and accurate 2-dimensional measurements without a PC software system? An optical comparator may be the right choice for you. Have a slightly larger budget and a desire to perform fast, accurate, easily repeatable measurements with contact measurement optional and CAD/DXF compatibility? You may want to look into a vision system. Whether you are certain which system is right for you or not, contact us to ensure your investment is a wise one. We’re here to help you! Contact your account manager for more information, call us at (800) 348-5701, or request a quote on one of our offered visual measurement systems.