Endoscope objective lens

Abstract

Abstract PURPOSE:To reduce distortion aberration by placing the 1st group having negative refracting power, the 2nd group having positive refracting power, the 3rd group which has positive refracting power and includes a lens having the convex surface on the object side, and the 4th group which includes a meniscus lens having the concave surface on the object side in specific relation. CONSTITUTION:The objective lens consists of the 1st group having negative refracting power, the 2nd group having positive refracting power, the 3rd group which has positive refracting power and includes a lens having the convex surface on the object side, a brightness stop arranged between the front end of the 2nd group and the rear end of the 3rd group, and the 4th group which includes a single body or cemented meniscus lens having the concave surface on the object body, and this lens system meets specific requirements shown by inequalities. Thus, the stop is arranged between the surface of the 2nd group closest to the object side and the surface of the 3rd group closest to the image side to compensate the distortion aberration. Further, the 4th group including the meniscus concave lens is arranged in front of an image plane, and consequently the lens system having long overall lens system length, a short lens diameter, a wide visual angle, and the large quantity of peripheral light is constituted.

Inventors

• 👤 Kimihiko Nishioka
• 👤 公彦 西岡

Bibliographic Details