Patent ID: 7589830
Filing Date: 2009-09-15
Classification: G03B

Abstract:
1. A method for testing a lens, the method comprising: providing an object and an image sensor, and positioning a lens at a first position between the object and the image sensor such that a distance between the lens and the object is a first object distance and a distance between the lens and the image sensor is a first image distance corresponding to the first object distance; obtaining a first modulation transfer function value for the lens with the lens at the first position; micro-moving the lens frontward and backward relative to the first position along a central axis of the lens to obtain a plurality of secondary positions of the lens and recording a plurality of secondary modulation transfer function values with the lens at the secondary positions, respectively; plotting the first modulation transfer function value and the plurality of secondary modulation transfer function values to form a first modulation transfer function curve; offsetting the first modulation transfer function curve a predetermined distance to form a secondary modulation transfer function curve, wherein the predetermined distance is a residual value between the first image distance and a secondary image distance corresponding to a secondary object distance; marking a line representing a first required modulation transfer function value and a line representing a secondary required modulation transfer function value; determining whether the first modulation transfer function curve intersects the first required modulation transfer function value line and whether the secondary modulation transfer function curve intersects the secondary required modulation transfer function value line to determine whether the first modulation transfer function value is not less than the first required modulation transfer function value and not less than the secondary required modulation transfer function value; and in response to determining at least one of that the first modulation transfer function value is less than the first required modulation transfer function value and that the first modulation transfer function value is less than the secondary required modulation transfer function value, determining that the lens is unsatisfactory.