| 摘要 |
<p>Provided is an endoscope objective optical system (1) that is constituted of, in order from an object side, a positive first group (G1), an aperture stop (S), and a positive second group (G2), wherein the first group (G1) is constituted of a negative first lens (L1) whose surface on the object side is flat and a positive second lens (L2); the second group (G2) is constituted of a combined lens (L34) formed of a positive third lens (L3) and a negative fourth lens (L4); and Conditional Expressions (1) to (3) are satisfied. f31, F32, and f are the focal lengths of the third lens, the fourth lens, and an entire system, respectively; and R3 and R4 are the radii of curvature of an object-side surface and an image-side surface of the second lens, respectively. 1.2 < f31/f < 1.55...(1), -2.8 < f32/f < -1.98...(2), and 0.38 < |R4+R3|/|R4-R3| < 0.77...(3).</p> |
