| 摘要 |
PROBLEM TO BE SOLVED: To provide a high performance wide angle conversion lens suitable for a high performance lens having a view angle in a wide angle end of about 55 deg.-60 deg., and reduced in image quality change. SOLUTION: This wide angle conversion lens 1 of a substantially afocal type fitted to a field side of a photographing lens to shorten a focal distance of the whole lens system is composed of, in order from the field side, the first lens L1 of a concave lens with a concave face of high curvature directed toward an image surface side, the second lens L2 of a convex lens with a convex face of high curvature directed toward the image surface side, the third lens L3 of a both-side-concave lens, and the fourth lens L4 of a both-side-convex lens. In this constitution, an angular magnification is made about 0.7, and respective conditions of 0.3<|h2/r2|<0.85, 0.15<|h2/r4|<0.45, 0.15<|h5/r5|<0.45, 1<r6/r7|<1.35, and 8<ν4-ν3<25 are satisfied, where hi represents a radius of an effective diameter of the i-th face, ri represents a radius of curvature of the i-th face, ni is a refractive index in the d-line of the i-th lens, andνi represents the Abbe number of the i-th lens.
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