METHOD FOR EVALUATING SPHERICAL MICROLENS

摘要

PURPOSE:To evaluate the sphericity of a lens with high accuracy by projecting a laser beam on the spherical lens to be measured, rotating the lens around an axis intersecting orthogonally with a direction perpendicular to optical axis of light beam and observing a projection image of a multireflection interference pattern from the lens. CONSTITUTION:The spherical lens 4 to be measured is fixed on a holding table 8 by vacuum suction and a fine adjustment base 7 is so adjusted that the laser beam is projected on the center of the lens 4. The distance L between the lens 4 and a screen 2 is so adjusted that the outermost periphery of the multireflection interference pattern 5 is of size suitable for observation; and the lens 4 is rotated by a holding table rotary mechanism 9 by + or -90 deg. around the axis Z-Z intersecting orthogonally with the direction perpendicular to the optical axis X-X' of incidence of the laser beam. At this time, the worst value Rmax of the major-monitor axis ratio R of the outermost periphery of the multireflection interference pattern 5 is read. Then a permissible value R'max corresponding to requested sphericity set with accuracy of the purpose of use previously is compared with the worst value Rmax to decide whether or not the lens is normal.