| 摘要 |
This infrared imaging optical system comprises a stop, a resin lens in which the object-side surface is convex on the object side, and an imaging element, and has an F value of 1.4 or less. On a plane that includes the optical axis, among the parallel luminous flux that enters the optical system at a positive incidence angle theta, a light ray that enters at a position that is the farthest from the optical axis on the plane of incidence is set as an upper light ray, the counterclockwise angle formed by the optical axis and the upper light ray before said upper light ray passes the plane of incidence is set as thetaOU, the angle formed by the optical axis and the upper light ray after said upper light ray passes the plane of incidence is set as theta1U and Deltatheta1U = theta1U-theta0U, and Deltatheta1U is negative throughout the entire range of theta0 and monotonically decreases in the range of 60% or less of the maximum value. Among the parallel luminous flux, a light ray that enters at the position farthest from the upper light ray is set as a lower light ray, the counterclockwise angle formed by the optical axis and the lower light ray before said lower light ray passes the plane of incidence is set as theta0L, and the angle formed by the optical axis and the lower light ray after said lower light ray passes the plane of incidence is set as theta1L and Deltatheta1L = theta1L-theta0. theta0 is 0 and Deltatheta1L is positive, and Deltatheta1L becomes negative when theta0 increases. |
