| 摘要 |
PROBLEM TO BE SOLVED: To obtain a diffraction lens formed into an approximate shape with high accuracy by a simple expression formula in the process of converting an optical pass difference function into a practical diffraction relief pattern having steps. SOLUTION: In the diffraction lens having a diffraction relief pattern on the lens surface, the diffraction relief pattern on at least one lens surface is expressed by formula (2) when the distance h in the perpendicular direction from the x-axis, which is the optical axis of the diffraction lens, is in the range of formula (1). The formulae are (1) hi-1<h<hi and (2) x=f(h-hti), wherein i is a suffix representing the number of the diffraction ring zone counting from the first zone surrounding the optical axis of the diffraction relief pattern to the peripheral region, hi is the distance of the border between the i-th diffraction zone ring and the (i+1)-th diffraction zone ring from the optical axis, and h0=0, f(h) is a function of h, and hti is a const. with a suffix i and at least one of hti is a constant which is not 0.
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