| 摘要 |
An optical system is provided to improve a transmittance ratio of a thermal IR(InfraRed) ray by arranging first and second lenses in a normal direction with respect to an inlet direction of the thermal IR ray. An optical system detects or senses heat according to a transmittance ratio of a thermal IR(InfraRed) ray and includes first and second lenses(110,120) and a diaphragm(130). The first lens has a positive magnification ratio and includes a convex surface on an object side and an aspherical concave surface on an image side. The convex and concave surfaces have positive and negative refractive powers, respectively. The second lens has a positive magnification ratio and includes a convex surface on the image side and an aspherical concave surface on the object side. The second lens is arranged behind the first lens. The convex and concave surfaces have positive and negative refractive powers, respectively. The diaphragm is arranged between the first and second lenses and close to the first lens, such that the light from the first lens is selectively converged.
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