| 摘要 |
PURPOSE:To obtain a wide-angle, compact rear stop type photographic consisting of four elements in four groups while various aberrations are compensated with good balance by satisfying specific geometric optical conditions. CONSTITUTION:The lens of 4-element, 4-group constitution consists of the 1st positive meniscus lens which has the convex surface on an object side, the 2nd negative meniscus lens which has the convex surface on the object side, the 3rd negative lens, and the 4th positive lens while a stop is arranged behind the 4th lens, and various conditions shown by inequalities 1-4 hold. The condition shown by the inequality 1 is concerned in the 1st lens and the compensation of a spherical aberration is improved. The condition shown by the inequality 2 is concerned in the compensation of coma flare, and the inequality 3 gives a relation between r3 and r2 so as to compensate the coma flare generated by the 2nd surface by the 3rd surface. The condition shown by the equation 4 is concerned in the divergent surface (6th surface) of the 3rd lens and the aspherical aberration and the Petzval's sum are held at proper values to compensate the astigmatism.
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