| abstract |
Provided are a wide angle optical system having better optical performance, low in cost, and compact in size, an imaging lens device having the wide angle optical system, a monitor camera, and a digital apparatus. The wide angle optical system ( 1 ) has, in order from the object side to the image side, a first lens ( 11 ) having a negative optical power, a second lens ( 12 ) having a negative optical power, a third lens ( 13 ) having a positive optical power, an aperture ( 15 ), and a fourth lens ( 14 ) having a positive optical power. The wide angle optical system satisfies the conditional expression of 3<f 34 /f<10, where f 34 is the composite focal length of the third and fourth lenses ( 13, 14 ) and f is the focal length of the entire system. |