Microlens testing: an application

Abstract

A measurement system for measuring effective focal length of a microlens is presented. The system consists of a microprocessor controlled 3-axis stage with an optical system which provides 500 times magnification for focal length and diameter measurement. The focal length testing is carried out by single pass (transmission) approach. A point source from halogen white light is used as the object for the measurement. A CCD camera displays the magnified image on a computer. Focusing is performed by moving the microlens along the principal axis by manual control of a stepper motor and observation of the image on the computer. Similarly, moving the microlens along its substrate plane and capturing three points on its circumference gives its diameter. The co-ordinates of the 3-axis stage and diameter are displayed separately on dot-matrix LCD panel. Anti-backlash mechanisms are employed on all axes, each with a positioning resolution of 1 μm.