| 摘要 |
Generally, it is difficult to previously know an adequate position of a special optical surface such as an aspherical surface, a diffraction optical element, or an eccentric surface in an optical system. If a trial of designing an optical system with all the possible surface numbers is made, the number of combinations is very large, and the designing is often impossible. The invention solves such a problem and provides means for automatically and efficiently finding out the most suitable surface number of a special optical surface. According to the invention, the surface number of a special optical surface different from a spherical surface is expanded to a real number value, the constitution of an optical system including a special optical surface having a real number value surface number is defined, the real number value surface number is used as an independent variable for optimizing the optical system, and the best surface number of the special optical surface is determined. If the real number value surface number lies in the range from an integer n to an integer n+1, one method for defining the constitution of an optical system including the special optical surface is inserting one or more virtual optical surfaces between an optical surface n and an optical surface n+1 and setting the virtual optical surfaces as special optical surfaces determined by the characteristic values and the real number value surface numbers of the special optical surfaces and different from a spherical surface.
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