Patent ID: 6835921
Filing Date: 2004-12-28
Classification: B41J,G02B

Abstract:
An imaging system for automatically focusing an image for recordation onto an illumination surface, the system comprising:a first illumination source for producing a first illumination field; a diffractive modulator for modulating the first illumination field received from the first illumination source; a first collimating lens for collimating the first illumination field received from the diffractive modulator; a pupil for passing the first illumination field from the first collimating lens; a first IR blocking filter for shielding the first collimating lens from light reflected from the imaging surface; a focal lens for focusing light received from the pupil onto the imaging surface; and an autofocus system comprising: a second illumination source for producing a second illumination field: a second collimating lens for collimating the second illumination field received from the second illumination source; a beam splitter and mirrors for directing the second illumination field from the second collimating lens through the first collimating lens, the pupil and the focal lens to the imaging surface, a portion of the second illumination field being reflected from the imaging surface and passing through the focal lens, the pupil and the first collimating lens; a second IR blocking filter for filtering the reflected portion of the second illumination field; a cylindrical lens for receiving the reflected portion from the second IR blocking filter and introducing an astigmatism that transforms a round spot into two orthogonal ellipses; a quad cell sensor for receiving the reflected portion from the cylindrical lens to produce a sensor output signal; and a control assembly for adjusting a focal point of the optical imaging system responsive to said sensor output signal.