Optical system of camera adapter for endoscope

The invention relates to an optical system of a camera adapter for an endoscope. The optical system comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens, wherein the principal optic axes of the six lenses are positioned on the same straight line; the first lens and the sixth lens are window plates and are respectively arranged at the two ends of the optical system; the second lens and the fifth lens are meniscus lenses and are arranged between the first lens and the sixth lens, and the concave surfaces of the second lens and the fifth lens are respectively arranged towards the first lens and the sixth lens; the third lens and the fourth lens are double-gluing lenses and are arranged between the second lens and the fifth lens; each double-gluing lens is formed by gluing a biconvex lens and a biconcave lens; the biconvex lenses of the third lens and the fourth lens are respectively arranged towards the second lens and the fifth lens; the biconcave lenses of the third lens and the fourth lens are arranged in an opposite way. After the optical system is adopted, the resolution ratio of the camera adapter for the endoscope is remarkably improved; the optical system is suitable for a high-definition camera with the pixel of more than two million.