Abstract: A projection lens structure mainly includes a first group of lenses with a negative dioptric value, a second group of lenses with a positive dioptric value, a third group of lenses with a positive dioptric value and a fourth group of lenses with a negative dioptric value. The first group of lenses further includes at least a first lens and a second lens, of which the first lens ha a plastic aspheric lens in a meniscus shape with a focal length between ?25˜?80 mm. The second group of lenses further includes at least a third lens. The third group of lenses further includes at least a first doublet with a focal length between 25˜80 mm. The fourth group of length further includes at least a group of doublets, a fourth lens and a fifth lens.

Abstract: A projection lens structure includes a first group of lens, an aperture stop and a second group of lend. The aperture stop is arranged at a rear of the first group of lens to form a long-focus lens with a focal length between 30-80 mm and the second group of lens is arranged at a rear of the aperture stop to form a short-focus lens with a focal length between 20-30 mm. With the long-focus lens and the short-focus lens operated correspondingly, the structure of the projection lens is simple and the manufacturing cost is low without affecting the quality of produced images.

Abstract: A projection system includes a long-focus lens that is able to generate an image independently with a focal length between 70-300 mm, a short-focus lens that is able to generate an image independently with a focal length between 3-8 mm and shares an optical axis with the long-focus lens and at least one reflector to reflect the optical axis for direction change. When the long-focus lens generates an image, the short-focus lens then generates the image to a pre-determined position thereby.