The difficulty of optical adjustment
In the context of the manufacturing process, "adjustment" signifies matching up the product's performance and specifications to standard ranges. If optical performance can be entirely translated into numerical values, the adjustment mechanism is operated so as to bring the parameter values to within their standard tolerances. At present, however, there are some parts for which optical performance cannot be translated into numerical values, and adjustment commonly relies on the sensitivity and experience of the technician.
For some optical systems, the technician has to adjust the focal point by visually judging the color. As the technician views the adjustment tool and turns the adjustment screw slightly, the white light from the light source separates into red, green and blue. If red is determined as the standard, the technician will need to adjust all microscope bodies under adjustment to exactly the same red. If the adjustment screw slips even slightly, the red will be too pale or too dark. The amount by which the adjustment screw is turned is so slight that it is virtually imperceptible to the human eye.
It takes considerable experience to be able to adjust the color to match. The technique required involves the technician's sensitivity, the ability to remember the color clearly, and the ability to reproduce it accurately.