Abstract: A lens system includes a plastic positive lens, a plastic negative lens and a glass positive lens. The plastic lenses are made to be meniscus lenses and an aspheric surface and a diffractive surface are respectively mounted onto the plastic lenses so as to have better image with low manufacturing cost.

Abstract: An assembly of optical lenses includes a first lens and a second lens, wherein the two lenses each have a concave surface and the two respective concave surfaces face with each other. The second lens has a contact surface and a separation surface respectively defined in an outer periphery of the concave surface. The separation surface is located closer to a center of the second concave surface than the contact surface. The concave surface of the first lens is engaged with the contact surface. The size of the contact surface is the same as the centering wheel so as to reduce the change resulted from machining between the two lenses.

Abstract: A lens system includes a plastic positive lens, a plastic negative lens and a glass positive lens. The plastic lenses are made to be meniscus lenses and an aspheric surface and a diffractive surface are respectively mounted onto the plastic lenses so as to have better image with low manufacturing cost.

Abstract: A lens system is particularly designed for use in an image reading device, essentially including three lenses elements, wherein two or three of them are plastic lenses.