Optical comparators, though, are no longer restricted to just optical magnification lenses. New advancements have allowed a comparator to be equipped with a video camera, similar to video inspection equipment. Much like a video inspection system, camera options come in both zoom and telecentric options. A zoom lens, capable of magnification levels of up to 240x, is useful for when smaller and more intricate features are the goal of inspection. Conversely, a telecentric option is more useful for when parts with larger features need to be fit within the field of view (FOV). Multiple telecentric lenses are now available depending on the specific FOV requirements of the user. An optical comparator that is equipped with a zoom or telecentric lens has all of the power of both a traditional comparator and video inspection system, but at a lower cost, while maximizing the initial investment in the comparator. The video cam- eras are designed to be interchangeable with traditional magnification lenses allowing the user to retrofit an existing system, quickly switch between interfaces, or equip a multi-lens system with a combination of the two. Modern comparators even have the ability to be equipped with a dedicated video system setup. Systems like the HDV Series from Starrett are essentially an optical comparator with a telecentric or zoom video lens, depending on the user’s needs. When an optical comparator is equipped with a video camera, it gains the ability to store digital overlays. Digital comparator technology eliminates the need for physical overlays and templates which can be costly to maintain and store.
For more advanced requirements there are a number of PC-driven options available. All in one touchscreen PCs are available and can mount directly to the comparator itself, as well as a traditional PC with monitor, keyboard and mouse for when full CNC control is required. All of these options are now also capable of supporting optical edge detection, a technology that makes use of a fiber optic edge sensor to identify transitions between light and dark fields, reducing operator subjectivity dra- matically when entering feature points to be measured. Second to none in terms of importance is the illumina- tion on an optical comparator. Most modern systems are equipped with LED lighting. LED illumination provides many advantages over more traditional options like fluorescent or halogen. They are far more durable and can withstand varying conditions across a wider range of temperatures making them far less likely to suffer a failure. They also boast a far longer lifespan than traditional bulbs and provide greater flexibility in design options, making them a more versatile resource. Along- side these important design features are many other benefits, including decreased energy requirements and lower waste production, that make them a very energy efficient and cost-effective design feature. The main feature set for any given optical compara- tor, however, is the optical equipment options that are available. There is a wide array of lens configurations available for both bench-top and floor-standing sys- tems. Lens options can range from 5x magnification all the way up to 100x in even magnification increments. Special lens options are also available, such as the 31.25x magnification, for when a special magnification specification is called for. Modern lenses are also easily interchangeable; a quick turn of the lens allows one magnification to be removed and another to be inserted in a matter of seconds.
Most companies also produce an extensive line of accessories that are designed to work in tandem with and enhance the capabilities of comparators. Storage cabinets are available in multiple sizes that are designed to work as a base for bench-top models or along- side floor-stand-
ing systems. Canopy and
curtain systems are available for
The Starrett HDV Series digital comparator
when the need for controlling, or minimizing, external light arises. Many different part-holding fixtures are also available depending on the specific requirements of each piece including multiple sizes of centers and vees, both fixed and rotary vises, rotary work stages, glass plate work holders, screen overlays, and calibration standards.
Lenses are readily interchanged
More advanced bench-top models, as well as floor-standing models, also have the capability of being equipped with two or more lenses simultaneously and indexed into position by means of a turret or slide.
EDM Today, Fall 2020 Issue
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