Design of short-focus projection lens for LED digital projectors

To achieve LED digital projectors project in a short distance with the bigger picture projection, according to the structural characteristics of such projectors, a short focal digital projection lens for 0.7 inch DLP projectors was designed and a design example of a lens, whose operating wavelength was 462-625 nm,full field of view angle was 84, relative aperture was 1:2.4, focal length was 10 mm and back focal length was greater than 20 mm was given on the basis of the theoretical calculation and the optimization of optical design software ZEMAX. Its MTF in all fields less than 30 is higher than 0.5 at the limiting spatial frequency of 40 lp/mm. The absolute value of the full field of view distortion of the lens was less than 1.5% ,the image quality is very good. Analytical results show that the design can decrease the production costs of the projecting system and promote the technological industrialization.