| 摘要 |
PURPOSE: A lens having diffractive elements attached thereto is provided to cut with high productivity using a diamond bit and which provides sufficient achromatism. CONSTITUTION: A diffraction order for the computation is set in step 2101, which is the first step. In the step 2102, Ei is initialized to 0 and the counter m for counting the regions is initialized to 1. In the step 2103, the diffraction efficiency ηmi of the i-th order diffraction light at the m-th region and the weight Wm for the m-th region are read out from the first and the second memory, and the product of ηmi and Wm is added to Ei. The step 2104 determines whether the region counter m is equal to M, to decide whether the calculation has been terminated for all regions. If m = M is not true, then there are regions left that have not been calculated, so m is increased by 1 in step 2105, and the procedure returns to step 2103. If in step 2104 m = M is true, the procedure advances to step 2106. The steps 2102 to 2105 correspond to the first processor of the present invention. Step 2106 determines whether a calculation for another diffraction order has to be performed. If a calculation of the diffraction efficiency of another order is necessary the procedure advances to step 2107, i is set to the next diffraction order, and the procedure is repeated from step 2102. When no calculation for another diffraction order is necessary, the calculation is terminated.
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