As the development of technology of liquid crystal monitors, mobile communication terminal products with cameras
integrally installed in have become more popular with consumers. These cameras must satisfy some requirements, for
example, the lens system must have a sufficient resolution and a size larger than the actual size of a sensor in
consideration of an assembly tolerance. In this paper, we provide a lens system with a high performance and compact
structure, which comprises a small number of lenses and is installed in a mobile communication terminal. In the system,
both the first and the second lenses have positive powers, and the third lens has a negative power, respectively. One of
the these lenses has at least one aspherical surface, and a perforated iris is located between the first lens and the second
lens. All the material for the lenses is plastic. The lens system is compact and its field angle is larger than 60 degree.
Moreover, the system consists of an infrared filter separated from the third lens by a designated distance for filtering
infrared wavelengths incident onto the optical system so as to protect an image plane from the infrared wavelengths.