Design of compact fisheye lens with slope-constrained Q-type aspheres

摘要

Two types of fisheye lenses for automobile navigation are designed with slope-constrained Q-type aspheres. Special requirements have been considered in the design process, and Q-type surfaces are introduced by converted from other kinds of aspheric description with only coefficients of low-order terms retained. A possible problem of imaging the first surface onto the sensor has also been analyzed. As a result, as for the six-element fisheye lens, MTF is greater than 0.3 at 451p/mm, f-θ distortion is less than 0.03 when the focal length is calibrated, field of view is 230° and full field relative illumination is greater than 0.4. For the four-element fisheye lens, MTF is greater than 0.4 at 451p/mm, f-θ distortion is less than 0.16 , field of view is 190° and full field relative illumination is greater than 0.6. The design results show that the Q-type surfaces employed in fisheye lenses can make the system more compact, lightweighted and easier to manufacture.