Autofocus module having a diffractively achromatized toroidal lens

An autofocus module for determining the distance of an object from a detector plane, comprising:

• means for generating a beam of light that is divergent in the horizontal direction and collimated in the vertical direction said beam of light reflecting from an object in its path;
• at least one pair of receiver lenses which have focal lengths that are longer and shorter than the distance to the detector plane positioned to receive the beam of light reflected from the object;
• at least one pair of photodetectors each positioned at the detector plane and associated with one of said pair of receiver lenses for providing output signals indicative of the reflected intensity received from the object;
• and
• means for determining the difference in output signals from said at least one pair of photodetectors whereby said difference is a function of the distance of the object from the detector plane.