Little work has been documented regarding the design of optical instrument scale reticles. Reticle is the word used to describe both scales and crosshairs used in the eyepiece of an optical instrument. An ergonomic (the relation of man to his working environment) experiment was performed in which thirteen different scale reticles were designed, manufactured and tested. The design parameters tested were scale spacing, line height, and line thickness. The testing consisted of thirty observers measuring a circular test object through a microscope with each scale reticles. The results, taking into consideration both variance in measurement and observer comments, showed the following dimensions to be best. Scale spacing of 10.0 or 15.0 minutes of arc as subtended by the eye is best. Line heights of 20.0, 10.0, and 15.0 or, 50.0, 25.0, and 37.5 for major, minor and intermediate marks respectively are best. The best line thickness was determined to be 30 minutes of arc for major marks and baseline, minor and intermediate marks should be 2.0 and 2.5 minutes of arc respectively. Appendix C should be consulted for the dimensions of the other two parameters in use at the time the optimum for the third was being determined.
Library of Congress Subject Headings
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Rockafellow, David D., "The Effect of microscope scale reticle design on variance of measurement" (1983). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus