Light from the objective lens (main optical comparator lens) exits the back of the lens and passes through a “hot” mirror. This mirror reflects the infrared light and some visible light and lets most of the visible light pass through to form an image on the optical comparator screen. The light reflected by the hot mirror is directed up to a small mirror located inside the top of the comparator. From there it is directed down and onto a fiber optic cable located in the left front section of the optical comparator. In effect the fiber optic cable sees in infrared light anything that passes over the center cross lines of the screen. You will see the image on the screen in visible light.

As the edge of the part you are measuring passes over the cross lines located in the center of the screen the edge sensor (if turned on) will detect that the cross line area has moved from light to dark and will enter a point on the readout. Then as you continue moving the part the sensor will detect that the cross-hair area has changed from dark to light and enter another point.

By using internal edge detection you can speed up the inspection process and achieve greater accuracy of measured parts by eliminating some of the human error associated with lining up the part on the cross lines by eye.

Related posts:

1. Optical comparator internal edge adjustment
2. Optical comparator bulbs
3. Optical comparators operating basics part 2