Focal compensation method for real-time focus correction in an autofocus system and slit mark structure

摘要

The present invention relates to a focus compensation method in an automatic focusing system used in various precision instruments and the like. In particular, a correlation between signals received by receiving an optical signal marked with a specific pattern reflected through an object is expressed by the following equation (3) A second step of detecting a center point of a marking signal in the received signal based on a correlation calculated through the process; A third step of determining whether or not the position correction is performed by comparing the center points of the marking signals detected in the above process, and a third step of determining whether or not the position correction is performed. If it is determined that the position correction is necessary, It is possible to detect the correlation of the mark signal only by the addition operation at the time of calculating the correlation, And the center point of the large signal is used as a reference point of comparison judgment.;Where k is the number of CCD pixels, and a₀, a₂, . , a_kAre integers that are not equal to each other, and l_One, l₂, . , l_n-1Is an interval between the slit bars when the slit is n,;T is the incident angle of the optical signal to the object, d is the starting point positional deviation occurring in the comparison of the third process, dL is the positional deviation of the object from the reference position, and providing the slit-There is an effect that real-time processing can be performed as compared with the conventional focus correction method.