Patent ID: 6664524
Filing Date: 2003-12-16
Classification: G02B

Abstract:
A method of focusing for use in a focus detecting apparatus comprising an objective lens, means for entering a luminous flux for focus detection into a target object from a position inconsistent with an optical axis of said objective lens through at least said objective lens, a condenser lens for converging the luminous flux after it is reflected by said target object and again passes through said objective lens, two two-division sensors disposed with the same optical inclination in front of and behind a position where said reflected luminous flux is converged by said condenser lens when a focus of said objective lens is adjusted to the surface of said target object, and a signal processing circuit for performing operational processing of signals from said two two-division sensors, the method comprising the steps of:an autofocus step of driving said objective lens with respect to said target object in rest and stopping said objective lens at a position where a processed signal corresponding to the luminous flux reflected by said target object after repassing through said objective lens of said signal processing circuit presents a value indicating a focus position; and a focus lock step of repeating a series of operations while said target object is moved, the series of operations including detection of processed signals of said signal processing circuit over a number of times, averaging of the detected signals, and drive of said objective lens such that the resultant average value matches a processed signal of said signal processing circuit to update the focus position, and then fixing the focus position.