Optical comparators can be very complex machines. However every optical comparator has similar design features and follows the same working principles. Optical comparators are used to magnify inspected part and cast its shadow onto a screen with chart to check for imperfections. Every optical comparator has a light source, which emits light beam. That light beam travels through prism and projects the shadow of inspected part. The shadow is then reflected through series of mirrors and finally ends up on chart screen. The operator can then compare the part against preset chart. Optical comparators have multiple lenses available, with different magnification steps. Zoom options vary from 5X to 500X. Screen sizes are also available in different sizes, from 10” to astonishing 80”. Combining screen size with optical zoom operator can inspect really big parts for really small anomalies. Another features found in modern optical comparators are digital readouts. These can vary from very simple, 1 or 2 axes digital readouts to more complicated 3 axes, programmable readouts, with geometric displays. More sophisticated digital readouts feature serial or parallel interfaces to interact with personal computers. In the nearest future those readouts can be expected to be equipped with more modern ports, such as usb, firewire and possibly Ethernet or lightpeak. Digital readouts with computer connection interfaces allow to transfer inspection results and to further export to CAD applications to manipulate extracted data.

Last important element found in optical comparators is stage. Optical comparator stages can be fully motorized or manual. Stages allow adjusting the position of inspected part. Inspected elements mounted on stage are resistant to external vibration providing more accurate results.

To summarize, the principle of optical comparator is to magnify inspected part. Basic elements found in most, if not every optical comparator are:

  • Light source
  • Mirrors
  • Screen with chart ring
  • Stage, motorized or manual
  • Digital readout