Prime lens

The utility model relates to a prime lens, which comprises a lens body and a lens cover, the first lens (L1) and the second lens (L2) are both negative in focal power, the third lens (L3) and the fourth lens (L4) are both positive in focal power, the fifth lens (L5) is negative in focal power, the sixth lens (L6) and the seventh lens (L7) are both positive in focal power, the eighth lens (L8) is negative in focal power, and the ninth lens (L9) is positive in focal power, or the third lens (L3) is negative in focal power. The prime lens further comprises a diaphragm (STOP) located between the fourth lens (L4) and the fifth lens (L5). The lens has a large view field, the view field angle can reach 144 degrees, 8 million pixels are considered, the lens is miniaturized and low in cost, the maximum image surface is 9.2 mm, and the lens is suitable for a sensor chip with a large target surface size. 本实用新型涉及一种定焦镜头，包括：沿光轴从物侧至像侧的方向，依次排列的光焦度均为负的第一透镜(L1)和第二透镜(L2)、光焦度均为正的第三透镜(L3)和第四透镜(L4)、光焦度为负的第五透镜(L5)、光焦度均为正的第六透镜(L6)和第