Grey's orthonormalization method (ORT method) was used in an automatic lens design program together with the damped least squares method (DLS method). A comparison was made with respect to the convergence efficiency of these two methods. Experimental results obtained are; 1) The influence of non-linearity should be taken into account in constructing a set of orthogonal axes. The ORT method is proved to be effective when the method is used with such a non-linear treatment. 2) At the initial

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... of design, the DLS method is superior in efficiency, while the ORT method is preferable after a design by DLS method comes to a saturation point.