Design of ultra-short focal miniature projection lens based on DMD

In order to solve the problems of high cost, large volume, vertical color difference and distortion correction for most existing ultra short focal projection equipment,an ultra-short focal micro projection lens based on DMD (digital micro-mirror device) chip was designed, and its tolerance analysis and thermal analysis were carried out. The system consists of 7 lenses, greatly simplifying the structure and reducing the cost. The F number of the system is 1.7, the focal length is 1.65 mm, the optical length is 79.39 mm, the projection ratio is 0.16, and the system has the characteristics of large aperture, large field of view and miniaturization. The design results show that the MTF (modulation transfer function) of the full field of view is larger than 0.65 at the space cutoff frequency of 93 lp/mm, which is close to the diffraction limit. The vertical color difference of the system is controlled within 1.2 μm, the maximum distortion is −2.17%, and the full-field relative illuminance is greater than 0.95, which satisfy the design requirements.